AN ABSTRACT OF THE THESIS OF Gordon Henry Kruse Master of Science for the degree of in Fisheries and Wildlife Title: Relationships between shelf temperatures, the coastal uplling index, and 17 April 1981 on presented English sole sea coastal (Parophrys level, vetulus) spawning activity ofT Oregon Redacted for privacy Abstract approved: Ty1er Albert V. The purpose of this study was to caupile records of (Parophrys spawning activity in Oregon waters and to attempt vetulus) to identify the environmental factors responsible for subobjective A spawning. relationships exist sole English between was Oregon to determine coastal the control whether of statistical shelf temperatures, sea level, and the upwelling index. waters Spawning times for English sole in Oregon for 13 were estimated years using data of adult female gonadal condition and surveys of pelagic larvae and newly-settled berithic juveniles of known The breeding variable. season of this species is ages. extremely protracted and Most spawning occurs between September and spawning lasting 1-3 months within this period. doci.nented to occur in all seasons of the year. April, with peak Some spawning has been ta sets of barometric pressure, the upwelling index, photoperioa and continental shelf temperatures along the Oregon coast were obtained to exanine possible interrelationships with the English sole spawning records. Because data of near-bottom temperature were not sufficiently complete, I investigated the relationships between the available sporadic records of temperature and two regularly measured variables, coastal sea level and the upwelling index. temperature at a moored of deep current meter (Poinsettia), sea level at Monthly means Newport, Oregon, and the coastal upwelling index at to found be significantly (P<O.05) 5°N, correlated over 125% were 1972-1974. Significant correlations were also found between both directly observed values and calculated anomalies of deep temperatures at two repeated hydrographic stations (NH-5 and NH-iS), and monthly mean sea Neah Bay, 1959-1969. Washington and level at the upwelling index at 145°N, 125°W during The geometric mean estimate of the functional regression best describes each linear relationship between variable pairs. Since the relationships between temperature and sea level were slightly stronger than those between temperature arid the upwelling index, Neah Bay sea level data were used to generate time series of a bottom temperature index, which was then incled into the environmental data set. Of the environmental variables considered, shelf temperature (inferred fran the relationship with Neah Bay sea level) appeared to best account for variations in Friglish sole spawning dynamics activity. Three hypotheses about temperature control of spawning were proposed and described by relationships were incorporated into driven by time of derived series a between simulated and historical which simulation model, bottom Hypotheses were parameterized arid evaluated, These relationships. mathematical spawning estimates. temperature based agreement the on The records. hypotheses which collectively explained most of the was three variability in observed spawning are: (1) the rate of gonadal development is inversely related to simmer bottom temperatures; (2) temperatures below about activity also be used in inhibited by The model can be used to simul ate years of no empirical spawning records and can for the is 7.8 C; and (3) spawning is delayed by rapid increases in bottom temperature. spawning spawning design of laboratory experiments validating the proposed hypotheses. capable of Relationships between elf Temperatures, Coastal Sea Level, the Coastal Upwelling Index, and glish sole (Parophrys vetulus) Spawning Activity off Oregon by Gordon Henry Kruse A THESIS submitted to Oregon State University in partial fulfillment of the requirnents for the degree of ster of Science Completed April 1981 Cornmencenent June 1981 APPROVED: Redacted for privacy Associate Professor of fisheries in charge of major Redacted for privacy iead of Dertznent of Fisheries and Wildlife Redacted for privacy Dean of aduate Schoqi ]te thesis is presented 17 April 1981 Typed by researcher for Gordon Henry Kruse Acknowi edgnents I wish to express my sincere appreciation to my advisor, Tyler, and my minor professor, Adriana Huyer, contributions of tine, advice and encouragenent. have been possible without their efforts. for his inputs as a committee manber. valiable assistance I Katherine for their generous This thesis would not I also thank Howard Horton am truly grateful for the offered by William Barsa, George Boehlert, Robert Demory, James Hell, Robert Hayman, Gary Hewitt, Laroche, Albert Myers, Bruce Earl Krygier, William Pearcy, t'bndy, Joanne Sally Richardson, Andrew Rosenberg and Carl Sebreak. William Gilbert constructed Pittock supplied the Fig. 1 and )4 of part II. Henry sea level data and Indrew Eakun provided recent values of the upwelling index. I am indebted to the following people who made part III possible by making their data available to me during the courses of their Laroche, Sally studies: Richardson, Gary William Hewitt, Pearcy, Earl Krygier, Joanne Andrew Rosenberg, Bruce tindy and Katherine Myers. of &ipport for this project was provided by the Pleuronectid Project the Program Oregon (Ok8MO11it). State University Sea Grant College TABLE OF CONTENTS I. Introduction II. The Relationships between Shel f Temperatures, . 1 Coastal Sea Level arid the Coastal Uplling Index off Newport, Oregon (coauthor: Adriana I-Juyer) ......... 3 Abstract ................................................. Introduction............................................. 5 Description of Observations .............................. 7 DataAnalysis ........................................... 12 Discussion.............................................. 23 III. Influence of' Physical Factors on the glish sole (Paroptirys vetul us) spawning season (coauthor: Albert V. 1'yler) .......................................... 26 Abstract ................................................ 26 introduction............................................ Compilation of Spawning Times ............................ Deve1o1ent of Spawning Simulation ?"bdel ................ Discussion.............................................. 28 30 37 50 IV. Conclusions ................................................ 54 V. References ................................................. 55 VI. Appendix ................................................... 62 LIST OF FIGURES II. The Relationships between ielf temperatures, Coastal Sea Level and the Coastal UpweJ.ling Index off Newport, Oregon Figure 1 2 Page Location of oceanographic data collection sites. 9 Daily values of (a) 80 m temperature at station Poinsettia; (b) Newport sea 1 ev el; and (c) the upl 1 irig index at 145°N, 10 Time series of observed and inferred near-bottom temperatures during 1959-1969 for (a) NH-5 and (b) NH-15 using Eqs. (3) and (5) of Table 5. 21 Inferred mean monthly temperature near the bottom at NH- 15 from Neah Bay sea level using Eq. (5) and observed mean monthly 22 125% for 16 December 1972 to 3 April 19714. 3 U temperature at Poinsettia. III. Influence of Physical Factors on the English sole (Parophrys vetul us) Spawning Season Figure 1 Location of data collection sites. Page ta used in this study came fran gonads of females landed at Astoria and Newport, larval surveys along transects between Astoria and Cape lanco, and juvenile surveys in Yaquina Bay. 2 Inferred spawning times for English sole using data of adult female gonadal condition arid surveys of' pelagic larvae and 32 36 benthic j uvenu]. es. 3 Relationship between spawning records and the mean bottom temperature index for the sunmer (May-August) prior to The proposed relationships beten mean sunnier temperature and the completion date of gona1 deve1oent for (a) most individuals and (b) the most rapidly developing individuals are also shown. spawning. 142 Figure 14 Hypothesized relationship between the rate of increase in mean monthly tnperature and the delay in the spawning Page 245 time. 5 Flow chart of spawning simulation model. 46 6 Comparison between observed (0) spawning records and those predicted (F) nen all three temperature hypotheses are incorporated into a simulation model driven with bottom temperature estimates. 148 LIST OF TABLES II. The Relationships between elf Temperatures, Coastal Sea Level and the Coastal Uplling Index off Newport, Oregon Table 1 Page Descriptions of oceanographic data used in this stxiy. 8 2 Correlation coefficients among daily and monthly means of 80 m temperature at Poinsettia, sea level at Newport and the upwelling index at 45°N, 125°W. 13 3 Correlation coefficients between monthly observations of 16 near-bottom temperatures at NH-5 and NH-iS and monthly means of sea level at Neah Bay and the uplling index at 145°N, 125°W over 1959-1969 for both the observed monthly means and the monthly anomalies. ! Long-tenn means of temperature observations, Neah Bay sea level and the upwelling index at 45°N, 125°W by month. 17 5 Regression equations between observations of temperature, sea level and the upwelling index based on 1959-1969 data for both the observed monthly means and the monthly mean 20 ancinal ies. III. Thfluence of Physical Factors on the English sole (Parophrys vetulus) Spawning Season Table Page Sources of data used to infer English sole spawning times. 31 2 Percentage of spent English sole females landed at Astoria as determined by the Oregon Department of Fish and Wildlife. 33 3 Total range of values of barometric pressure, day length and indices of upwelling and bottom temperature over all months and over only those months in 4nich spawning 38 1 occurred. Relationships between &ielf Temperatures, Coastal Sea Level, the Coastal Upwelling Index, and English sole (Parophrys vetulus) Spawning Activity off' Oregon Introduction The reproductive believed to be strategies by a given utilized species those which result in rnaxthrn.m reproductive success by growth and survival. favorable conditions best ensuring that the young will encounter which Since reproductive success is of investigations biological basis for the stocks. an important this management regard this In the reproductive strategies and survival are related. fecundity, productivity, for Annual variations in reproductive success (i.e year-class strength) reflect deviations of those factors to species' are canponent of fishery aspect constitute part of the of cctmnercially important studies of spawning activity and fish its envirormtal control can be of value to the management of species with variable spawning times. This is particularly true for those in stnich year-class strength is determined by factors operating time period during the early stages of develonent. the spawning time partly determines whether the young over a short For these fishes will encounter favorable conditions. English sole, species to the ?arophrys bottom United States and Canada. trawl vetulus, is fisheries a cctnmercially important along the west coast of the The breeding season of this species is quite 2 1959; Jow 1969) protracted (dd 19140; Harry Richardson 1979; Hayman and Tyler the survival rate of young 1980). English and variable (Laroche and The spawning time may affect soles, because year-class strength appears to be largely determined by environmental conditions prevailing prior to spawning (Hayman history stages (Ketchen 1956). variations in English sole and Tyler 1980) and during the early life investigation of the For this reason activity may lead to a better spawning understanding of their recruitment process and to improved management. The purpose of this study was three fold. to The first objective was canpile records of English sole spawning activity in Oregon waters using data of gonadal condition from commercially caught females landed at Oregon ports, size distributions and known growth rates of pelagic larvae collected off the Oregon coast, juveniles in Yaquina Bay, Oregon. and surveys of newly-settled The second objective was to attempt data to identify interrelationships between these spawning records and of' barcinetric pressure, the upwelling index, temperature on the Oregon continental shelf. observations re day length, and deep temperature Because deep not sufficiently complete, a third objective was to determine whether temperature is statistically related to two regularly measured variables (coastal sea level and the uplling index), so that a continuous temperature index could be developed. This thesis is comprised of two independent papers. The first is coauthored by Adriana Huyer and is designed to meet the third objective of this sti.r.ly. The second paper is coauthored by Albert V. is directed towards the first two objectives. Tyler and 3 The Relationships between iel f Temperatures, Coastal Sea Level and the Coastal tjpwelling Index off Newport, Oregon (Coauthor: Adriana Huyer) Abstract Sparse bottc4n temperature records have hampered with denersal fish dealing species living on the continental shelf along the northwest coast of North America. between deep temperatures on regularly measured variables, index. studies investigated We the the relationships Oregon continental shelf and two coastal sea level and the upwelling Monthly means of deep temperature at a moored current meter (Poinsettia), sea level at Newport, Oregon and the coastal upwell ing index at L5°N, 125°W were found to be significantly (P<O.05) correlated over 1972-1974. Significant correlations were also found between both directly observed values and calculated anomalies of deep temperatures at two repeated hydrographic stations (NH-5 mean sea level Lt.5°N, 125°W at during temperature and Neah Bay, 1959-1969. sea level and NH-is), and monthly Washington and the upwelling index at Since the relationships between were slightly stronger than those between temperature and the upwelling index, sea level is a more reliable deep temperature indicator. The geometric mean estimate of the functional regression best describes each linear pairs. relationship between variable The regression equations between temperature and sea level (or the upwelling index) and between their anomalies can be useful to reveal bottctn observations. tnperature dynamics during periods of sparse 5 Introduction Fishery stock-recruitment models must factors in order incorporate sufficiently account to variations of many fish species. for environmental year-class strength The most cctnmonly considered physical factor is temperature, owing to its known effects on many physiological processes and its linkage to other factors such as and productivity. Temperature appears to salinity, currents significantly affect the recruitment success of nunerous fishes (Ketchen 1956; Lett et al. 1975; Sutcliffe et al. 1977; and others). Temperature may act on reproductive success by controlling the amount of energy directed gonadal in maturing products and ivis 1967) processes associated production influence conditions. (Bagenaj. spawning therefore the timing of eggs and larvae abiotic and with growth and gonadogenesia (Weibe 1968) or indirectly through a linkage with food variations may also growth This control may be exercised adul ts. directly through the physiological (Warren into 1967). Temperature dates (de Vianing 1972) and with flucttating biotic and In addition temperature may regulate the survival of' the young by influencing their food availability (Lett et al. 1975), growth (Zweifel (Ketchen 1956). and Lasker 1976) and For these reasons bottom duration of pelagic life temperatures can be very important to demersal fish species. Unfortunately, northwest sporadic bottom records along the coast of North America have Impeded fishery correlation and simulation stiies in this region. to temperature Therefore it uld be advantageous identify a regularly measured environmental factor 'thich is well 6 correlated with deep temperatures on the continental shelf. Of f Oregon surface temperatures are not representative of deep temperatures (at least not seasonally), in part because of the seasonal influences of coastal upwelling and the Columbia river plume (Huyer 1977). Previous sti.iles have exanined relationships between surface or near-surface temperatures and such factors as sea level, wind, atmospheric pressure and upwelling (Roden 1960; Bourke 1969; Fisher 1970; and others). To our knowledge no stixties have found relationships between bottom or near-bottcm shelf temperatures and these or other factors. The apparent similarity between time series of coastal sea level and 40 in temperature at a current meter mooring located over the 100 in isobath off Newport, Oregon (Huyer and nith 1978: Fig. 2) suggested to us that perhaps sea level might be a good index of bottom temperature. A temperature-sea level relationship would be usefti because sea level measurements are readily avail able to researchers and are recorded at regular intervals. We also considered the possibility that deep temperatures are related to the coastal upwelling index (Eakun 1975), 1973; because this index is proportional to an important driving force in the Oregon oceanographic system, the al ongshore wind stress. index is already this region. widely This used in fishery and oceanographic stties in Values of the upwelling index are available at regular intervals to provide information about upwelling system dynamics. The purpose of this sti.y was to determine thether coastal sea level or the upwelling index can be used to infer near-bottom temperatures on the continental shelf off Oregon. 7 Description of Observations period We obtained a data set for the 2 April (Table 1), 197'4 which 17 December through 1972 daily means of the 80 m included temperature at a mid-shelf current meter mooring Poinsettia named (Fig. 1), the sea level at nearby Newport, Oregon and daily and monthly values of the coastal upwellirig index at current The 45°N, 125°W. observations fran this mooring and the simultaneous sea level data have been described by Huyer et al. recorded at was recorded on an was Using the 6-hourly records abridged and we per day). ( calculated to daily means of of the upwelling index were reported by Bakun (1973; 1975). computation of this index involves (computed 6-hourly Daily (Fig. 2) and monthly values temperature and sea level (Fig. 2). monthly values Sea filtered to remove tides, basis, hourly adjusted for the inverted barometer effect values. 80 in intervals of 10 or 20 mm, filtered to remove diurnal and shorter oscillations and reduced to 6-hourly values level at The temperature (1 979). a nonlinear tenn (wind Since the stress), fran monthly mean pressure fields) are not identical to the monthly means of the daily values (based on 6-hourly computations), although they are highly correlated (Bakun 1973). A second data set spans June 1959 through November 1969 and (Table 1) includes observations of near-bottom temperatures fran repeated hydrographic stations at NH-5 and hourly (not Washington hydrographic NH-iS (Fig. 1), monthly means of adjusted for atmospheric pressure) sea level at Neah Bay, and monthly values of Bakun's upwelling stations were described by Huyer (1 977). index. The Temperature was Table 1. Location Descriptions of oceanographic data used in this study. Observation Total depth Sample depth (m) (a) Poinsettia Temperature* Dates Data Type No. of values 80 17 Dec 72 - 2 Apr 711 Daily means '400 - - 17 Dec 72 - 2 Apr 714 Daily means 472 - - 17 Dec 72 - 2 Apr 711 Daily values 472 100 (44°115'tl, 124° 17. 5W) Newport, Oil Sea levelt 115°N 12W Upwelling index Temperature NH-S (44°39.1'N, 55 50 29 Jun 59 - 60 - 90 29 Jun 59 - 140 - Monthly values 17 21 Nov 69 Approx. 78 21 Nov 69 ApprOx. 82 12i1°10.6W) Temperature NH-IS 100 ('14°39.1N, 8 per yr. 8 per yr. 124°27. '4 W) Mesh Bay, WA Sea levelt 145°N 125<'W IJpwelllng index - .- Jun 59 - Nov 69 Monthly means 126 - - Jun 59 - Nov 69 tlonthiy values 126 *This record contains two gaps (23 March 1973 through 12 April 1973 and 25 June 1973 through 14 August 1973). These gaps were also placed into the sea level and upwelling records for all statistical analyses involving temperature and these other variables. t5ublract 1.1433 in from Newport sea level to refer to mean lower low water. +Subtract 0.701 in froni Neah Bay sea level to refer to mean lower low water. 1 Figure 1. Location of stations Poinsettia (P), NH-5 and NH-15 in relation to Newport, Oregon and Neah Bay, 1ashington. This figure is a Lambert conforia1 conic proj ectiori made from the Juan de Fuca plate map, published by the Pacific Geoscience Center, Sidney, British Colunbia. "-I YT !Z5 123a 10 tily values of (a) 80 m temperature at station Poinsettia; Figure 2. (b) Newport sea level; and (c) the upwelling index at 45°N, 125°t4 for 16 December 1972 to 3 April 19714. 2 6 U 0 w 0 2 L&i k 33r 3.' -J LA.i > 2.9 2.7 2.5 2.3 200- C 2OO LJ -400- 0.. I! 600DJFMAMJJASONDJFMA I I I MONTH I I I recorded an average of eight times per year at each station. than one averaged. observation was available for a given month, they were A total of six monthly values at each actually means of 2it observations. When more NH-5 and NH-15 are 12 Data P1nalysis Time series plots (Fig. 2) arid scatter diagrams (not shown) suggested the existence of linear relationships between Poinsettia deep temperature, Newport sea level and the upwelling index at 45°N, 125°W for 1972-197. To verify this we calculated simple linear correlation coefficients for daily and monthly mean values of the variables (Table 2). Since time series of each variable are autocorrelated, consecutive observations are not independent and the significance of these crosscorrelations cannot be determined by simply consulting standard statistical tables with N1 -2 degrees of freedaii, where N1 is the number of observations. In order to document statistical significance we could calculate normalized correlation coefficients (Sciremanmano 1979) or adjust the number of degrees of freedan by first estimating the actual of number independent observations latter procedure and used the Bayl ey and Hainmersi ey formulation because it is more conservative, i.e. results in fewer degrees of freedcm. The (Bayley and Rarnmersley l946; Davis 1976). chose We the Bayley and Hammersley formulation can be written as N N-1 N.+ 2 3:1 (N1-j) p (j.t) 2 (1) where n! is the number of independent observations estimated fran the autocorrelation (p(jat)) at lag jt of variable i for i=1,2. number of degrees of freedan (DF) can then be taken as DF : mn(n,n) - 2. (2) The 13 Table 2. Correlation coefficients (nunber of observations and degrees of freedan in parentheses) among daily and monthly means of 80 in temperature (T) at Poinsettia (P), sea level (SL) at Newport (NP) and the uplling index (UI) at 145°N, 125°W. a. Daily means UI SL(NP) _0.609(1472,12)* O.80k6(1400,12)** UI T(P) O.140k0()4OO,12) b. Monthly means SL(NP) UI T(P) UI _0.8909(17,5)** 0.9085(15,5)** _0.8255(15,5)* *P<0. 05 **p<0Q2 114 In practice the suimatiori in (1) is carried out for j:1,2,...,K, where K is some nunber large relative to the lag at which the autocorrelation beectnes zero. We took K to be a value such that DF reached an asymptote. Since the 80 in temperature series at Poinsettia has two gaps, is it not possible to calculate ri' for the entire tnperàture record. the longest noninterrupted Over 2 April period through (15 August 1973 the values of n* calculated for the temperature and sea 1 9714) level records were nearly identical. Therefore we assuned the value of n for temperature over the entire record through 2 April 19714) length (17 December 1972 to be equal to the value of n! calculated for sea level by Eq. (2). Correlations among Poinsettia temperature, Newport sea level and the upwelling index (Table 2) were significant in all but one case at the 95% confidence level using tables of critical values of the correlation coefficient (Zar 1 9714: Table D. 21). The exception (daily is not surprising because the short fluctuations are large relative to those of temperature versus upwe].ling) period upwelling index temperature, particularly during the winter months (Fig. 2a,c). Observations at. hydrographic stations made repeatedly (approximately 8 per year) at NH-5 and NH-i 5 (Fig. 1) between June 1959 and November 1969 allowed us to determine whether the associations suggested by the Poinsettia data remained true for longer time scales. For this time period, we had access to monthly mean sea level data from Neah Bay (the Newport sea level record does not start until 1967), and 15 monthly values of Bakunz upwelling index at 145°N, 125°W. period deep temperature individual fluctuations are observations of temperature approximations to the monthly means. short Since usually small (Fig. 2a), should generally be On this basis good corresponded NH-5 and NH-15 temperature observations with monthly means of sea level and the uplling index. Because lagged correlations on daily values during 1973 indicated that the upwelling index leads sea level by about 2 days and deep temperature by 5 days, no lagging of monthly means was necessary. Scatter diagrsms (not shown) again suggested linear between monthly values of each variable pair. positive correlation exists between relationships A significant (P<O.02) temperature and sea level and significant negative correlations exist between these ti variables and the coastal uplling index freedan by the calculated (Table procedure used 3a). Degrees of earlier. were The conservatism of the Bayley and Haxmnersley (1946) formulation is reflected by the fact there approximately only one is that degree of freedan per year of data (Table 3a). In order to correlations, eliminate we variable (Table U). estimated first the effect of seasonal For temperature the long-term monthly means by averaging the cc*nputed the long- term monthly means for each individual observations by month duration of the records (June 1959 - November 1969). the cycles on were for the For sea level and upwelling index, a ccinparable period was chosen sh that an equal number of values (11) were used for each month (June 1959 - May 1970). 16 Correlation coefficients (nunber of observations and degrees of freedi in parentheses) between monthly observations of near-bottom temperatures (T) at NH-5 and NH-iS and monthly means of sea level (SL) at Neah ay (NB) and the upwelling index (UI) at 45°N, 125°W over 1959-1969 for both the observed monthly means and the monthly Table 3. anana]. ies. a. Observed values UI SL(NB) UI T(NH-5) T(NH-15) T(NH-5) _O.8563(126,9)** o.7k25(78,9)** O.7168(82,9)** O.71O3(78,9)** _O.6791(82,9)** o.8579(78,9)** b. InomaJ.ies SL(NB) UI T(NH-5) _O.6198(126,65)** 0.14662(78, 65)** T(NH-15) 0.35)414(82,65)** *P <0.05 **p<002 UI T(NFI-5) 0. 3)432(78, 65)** _O.2)428(82,65)* 0.7156(78,65)** 17 Table U. Long-term means of temperature (°C) observations, Neah Bay at sea level0(m) and the upwelling index (m3/s/100 m of coastline) 45°N, 125 W by month. Monthly means for temperature are based on Means for sea level and observations during June 1959 - November 1969. uplling are based on a comparable period consisting of 11 values for each month (June 1959 - May 1970). T(NH- 5) T(NH-15) SL(NB) UI Jan Feb Mar Apr 9.94 9.12 9.35 8.89 9.59 -92.55 -58.00 -19.73 May 8.143 7.149 2.11 2.07 2.01 1.93 1.88 1.86 1.85 1.89 1.92 Jun Jul Aug Sep Oct Nov Dec Annual mean 9.149 7.69 10.10 9.29 8.73 8.72 7.78 7.60 7.52 7.76 9.05 11 . 61 9. 87 2. 07 10.68 10.26 2.13 52.55 20.82 -27.18 -65.82 -88.73 9.03 8.81 1.98 -7.09 7.19 7.143 2.00 12.145 39.73 57.00 814.36 1I We then subtracted these long-term monthly means frau the values to obtain monthly anomalies. all pairwise time Simple linear correlations between canbinations of anomalies confidence level (Table 3b). observed are significant at the 95% The nunber of degrees of freedom between series of ananalies is much higher than between absolutes, since the elimination of seasonal cycles reduces the autocorrelation of each time series. Based on these results, it is reasonable to attempt to infer deep temperatures fran either sea level or the upwelling index, but slightly more confidence Although uld be placed upon those variables were inferred fran sea level. clearly definable as dependent not independent, we initially conducted simple linear regression or anal yses on the 1959-1969 records with temperature as the dependent variable and sea level or the upwelling index as the independent variable. we found these regressions to yield undesirable biases. However, Plots of time series (not shown) conspicuously revealed that at high sea levels upwelling index) inferred temperatures observed temperatures and at low sea inferred temperatures (low were considerably lower than levels (high upwelling were much higher than those observed. index) Reversal of dependent and independent variables resulted in the converse. This phenomenon exists since a regression of Y on X minimizes the stin of the squares of the vertical distances of the while a regression of X on Y observations to the line, minimizes the sun of squares of the horizontal distances of the points to the line. 19 To circunvent the obvious biases caused by either simple linear regressions, we ccmputed the "geometric mean estimate of the functional regression", hereafter "GM regression", strongly advocated (1973) flicker particularly in situations in *iich variability due to natural causes outweighs that due to measurement. line by which minimizes vertical distances intermediate the fran sun The GM regression yields a of' the products of the horizontal and each observation to the to the regressions of Y on X and X on Y. equation is easily calculated Iran simple anal yses linear regression regression equations are presented statistics in is This regression normally provided by Computed GM (Ricker Table 5 and line, 1973). with approximate 95% confidence intervals for the slopes. To visually demonstrate the utility of the temperature and sea level, relationship between plots were made of observed and inferred mean monthly near-bottani temperatures at NH-.5 and NH-i 5 and (5), respectively (Fig. 3). using A test of this relationship would be to use sea level to estimate temperature for a different Since stations NH-iS and Poinsettia are close (15 over the same isobath (100 in), using data one Eq. (3) would expect time period. n apart) and located Eq. (5) (developed from 1959-1969) to reasonably estimate deep temperature at Poinsettia during 1972-1974. A plot (Fig. k) of inferred monthly mean temperatures observed at NH-iS and monthly mean Poinsettia indicates that this is the case. temperatures The average error is 0.56 C, an error which should be acceptable for most purposes. at only 20 Table 5. Regression equations with 95% confidence intervals of the slopes between observations of temperature (00), sea level (m) and the upwelling index (rrL3/s/1 00 m of coastline) based on 1959-1969 data for both the observed monthly means and the monthly mean anomalies. a. Observed values T(NH-5) T(NH-5) T(NH-15) T(NH-15) T(NH-15) -15.8133 + (12.5108 ± 2.17)43) X SL(NB) 8.8278 - (0.0228 0.00)42) X UI (3) -9. 1761 + (9.08)41 1.6019) X SL(NB) 8.6901 - (0.0168 ± 0.0031) X UI (5) (6) (7) 2.2118 + (0.729)4 ± 0.0972) X T(NH-5) b. 4noma1ies T(NH-5) T(NH-5) T(NH-15) T(HH-15) T(NH-15) -0.0863 + (10.6825 ± 2. 1659) X SL(NB) -0.0319 - (0.0205 ± 0.00)4)4) X UI -0.0213 + (8.7)402 ± 1.8257) X SL(NB) -0.0010 - (0.0176 0.0038) X UI = 0.0000 + (0.8811 ± 0.1)411) X T(NH-5) (8) (9) (10) (11) (12) 21 Time series of observed (dots) and inferred (solid line) Figure 3. near-bottom tanperature during 1959-1969 for (a) NH-.5 and (b) NH-iS using Eqs. (3) and (5) of Table 5. aS ri is: C) w b a. w12 I- LI 1959 1960 $961 1962 $963 $964 $965 $966 196T $968 1969 YEAR 22 Figure L mean monthly temperature near the bottom at NH-i 5 from Neah Bay sea level using Eq. (5) (dashed line) and observed mean monthly temperature at Poinsettia (solid line) with ±1 SD of the Monthly predicted (light stippled) and observed means (dark stippled). means and standard deviations of Poinsettia temperature are calculated using the full complement of daily values for each month except December 1972 (15 days), and five months in 1973: March (22 days), April (18 days), June (2 days), July (0 days) and August (17 days). Inferred 12 310 Ui 4 7 6 D J F M AM J J 1973 A SO N 0 J FM 1974 23 Discussion Studies investigating the dynamics of marine demersal fishes have established a demand for long- tenil continuous bottom temperature records. Since attempted such records are not usually available, have we to meet this need by establishing relationships between near-bottom temperature (measured only sporadically) other and variables which are routinely measured on a continuing basis. e found that near-bottom temperatures over the continental shelf off central Oregon are significantly correlated with coastal sea level, and also (though to a lesser extent) with the coastal upwelling index from computed the large scale wind field. th of these correlations hold for monthl y mean data. The correlation with sea level al so holds for daily means of' low-pass filtered sea level (i.e., with the diurnal and semi-diurnal tides removed from the sea level data before the daily means are computed). The correlation between temperature and the upwelling index does not hold on this shorter time scale. found significant correlations We between the monthly anomalies also of near-bottom temperature and those of sea level and the upwelling index. This correlation among anomalies indicates actually correlated with each other, instead of that the variables are only appearing to be correlated because they all have seasonal cycles. The observed correlations were not entirely unexpected. upwelling Coastal is well known to affect shore temperatures along the Oregon coast, and one would naturally expect it to also affect the near-bottom temperatures over the inner continental shelf and perhaps over the 24 mid-shelf. over Coastal sea level varies with the density changing field the continental shelf and slope on both the longer (monthly mean) time scale (Reid and Mantyla 1976) and the shorter (days-to-weeks) time scale (Buyer et al. and one might salinity, correlated Since density is a function of temperature 1979). with coastal expect temperatures near-bottom sea level. to be Our results show that the bottom temperatures are actually better correlated with sea with than level Bakun's upwelling index. We chose linear equations, tenried Q4 regressions, to describe relationships between variables the Simple linear regression (Table 5). eapations were not used due to biases which were particularly expressed at extreme values of each variable. near-bottom temperature relationships with and (10) be can locations. sea used at NH-5 or For estimating monthly mean one NH-15, should use level: Eq. (3) or (5), respectively. for estimating monthly anomalies the Eq. (8) at these The upwelling index is also useful to infer monthly values of temperature, particularly since gaps in the Neah Bay sea level record do exist in some years. Al though our quantitative results (the constants in Tables ! and 5) are probably valid only for the locations from which they were derived (i.e , NH-5 and NH-iS over the continental shelf off Oregon), we applicable. expect the qualitative results Anomalies of coastal sea distances (Enfield and Allen 1980). correlated with sea 1 evel, level are to Newport, be more generally coherent over long Since near-bottom temperatures are anomalies of near-bottom temperature 25 probably also have high alongshore coherence. If so, the Neah Bay sea level will be a qualitative indicator of bottom temperatures over shelf along California. much of shing ton, Oregon, and perhaps Our quantitative results will certainly prove simulation models of fisheries off central Oregon. the northern useful for Influence of Physical Factors on the &glish sole (Parophrys vetulus) Spawning Season Tyler) (Coauthor: Albert V. Abstract Spawning tines for &iglish waters were sole (Parophrys vetulus) in Oregon estimated for 13 years using data of adult female gonadal condition and surveys of pelagic larvae and benthic juveniles of known ages. The spawning season for this species is extremely protracted and variable. peak Most spawning occurs between September and April, with spawning lasting 1-3 months within this period. Some spawning has been docunented to occur in all seasons of the year. Variations in the largely attributable glish season spawning sole about temperature described by mathematical incorporated into be to to variations in a continental shelf temperature index (developed fran a relationship with Neah Bay sea hypotheses appear control of relationships. Three level). spawning were proposed and These relationships were a simulation model, which was driven by tine series of the bottom temperature index for those years in which spawning records were based on the records. The three temperature hypotheses which collectively explained available. Hypotheses were parameterized and evaluated, agreement between simulated much of the variablility in observed spawning and are: historical (1) the spawning rate of gonadal developnent is inversely related to sunnier bottom tanperatures; 27 (2) spawning is inhibited by temperatures below about spawning is delayed model can be used empirical spawning to by rapid simulate records and and (3) increases in bottom temperature. The spawning can activity also be 7.8 C; for years of no used in the design of laboratory experiments capable of validating the proposed hypotheses. 28 Introduction veral general patterns in the reproductive strategies of marine fishes have been proposed by sim (1956), Q.ishing (1969; 1975) and others. Fishes common to low latitudes or upwelling areas are often serial spawners and tend to have long seasons. In nonupwelling convergences spring (and intermittent breeding and regions polet..ard of subtropical the perhaps some fall) spawners generally breed only once per year over short (about three months) fixed seasons, while sunmer spawners tend to be intermediate in these characteristics. The reproductive strategies utilized believed by a given species are to be those which result in maxirnun reproductive success by best ensuring that the young will encounter conditions favorable for survival. growth and Annual variations in reproductive success (i.e year-class strength) reflect deviations of those factors to which the species' fecundity, reproductive strategies and survival are related. Investigations of reproductive success constitute part of the basis for the managnent of commercially important fish biological stocks. In this regard studies of spawning activity and its environmental control can be of value to the managnent of species with This is particularly true for those in which year-class strength is determined by factors operating over a short variable spawning times. time period during the early stages of develoinent. For these fishes the spawning time partly determines whether the young favorable conditions. will encounter 29 English sole, species to the Paropkrys bottom consistent fishes common suggests that is a along the west coast of the because pleuronectid with at least one of the general patterns observed for to upwelling areas. While examination of ovaries Hewitt, Oregon individuals are not serial spawners (G. quite comm.), protracted time may affect Harry (&idd 19)40; year-class the strength season of this breeding the variable (Laroche and Richardson 1979; Hayman spawning commercially important The spawning strategy of this State University (OSU), pers. species is fisheries trawl United States and Canada. is vetulus, and 1959; Jow 1969) and Tyler 1980). The survival rate of young Fnglish soles, appears to be largely detennined by hydrographic events occurring prior to spawning (Hayman and Tyler 1980) and during the early stages of develonent (Ketchen reason investigation of the activity may lead process to a better variations in understanding and to improved managnent. English of sole their this spawning recruitment The objectives of this sttdy were to compile records of English sole spawning activity in and For 1956). Oregon waters to attampt to identify the environmental factors which control the time of spawning. 30 Compilation of Spawning Times Generally the most accurate procedure for the determination of teleost spawning times involves the representative sample of adult examination of ovaries in a fema]. es. Temporal variations in intensity can be quantified using measures such as the proportion of females ioh are fully spawned (Harry 1959), spawning gonadosornatic indices ('brse follicles (Hunter and Goldberg or the incidence of postovulatory 1980) 1980). times Spawning can also be back-calculated fran larval or juvenile size composition data if the growth rates of these stages are accurately known. We access to had each of these types of data (Table 1) for the purpose of inferring past English sole spawning times. condition of adult P. vetulus females landed at The gonadal Astoria (Fig. 1) Oregon (Harry as monitored by the Oregon Fish Commission, now the Department of Fish and Wildlife 1959). during 1947-1 951 Since data have not been published on a year-by-year basis, we present then in Table 2. Ovaries were also sampled from individuals landed at Newport from October by Hewitt (ODFW), (1980). 1977 through February 1978 With these data, we used changes in the percentage of spent females between consecutive sampling dates as a measure of spawning activity. Pelagic larval surveys were conducted along a transect off Yaquina Bay (Fig. 1) during June 1969 1977; Richardson and Pearcy Cape Blanco and through August 1977), Astoria in and along 1972 (Mundy MS; Richardson various transects between rch and April of 1972-1975 (Laroche and 31 Table 1. Sources of' data used to infer English sole spasning times. Method Years Adult goriadal 1947-51 Harry (1959) 1977-78 Hewitt (1980) 1969-72 Mundy (MS) 1971-72 Richardson (1977), Richardson and Pearcy (1977) 1972-75 Laroche and Richardson (1979) Source Condition Fl anktonic larval surveys Benthic juvenile 1970-72 surveys 1977-78 1977-79 Krygier and Pearcy (MS) Myers (1980) Krygier and Pearcy (MS) Rosenberg (1980) 32 Figure 1. Location of data collection sites. tta used in this study came fran gonads of females landed at Astoria and Newport, larval surveys along transects between Astoria and Cape Blanco, and juvenile surveys in Yaquina Bay. 460 200m 100Dm ) 200Dm Newport D 0 Pacific Yaquina Ocean 44 Oregon Cape Olanco 42°N I 127°W 125° 123° 33 Table 2. Percentage of spent English sole females landed at Astoria on each sample date from ODFW data (Harry 1959). te Sample Size 18 JAN 19118* 18 MAR 19118 25 OCT 10 16 21 7 14 NOV 19)48 19118 19148* DEC DEC 19118* JAN 19)49 JAN 19)49 MAR 8 MAR 17 MAY 18 NOV 6 FEB 1 37J4 91 9 90 1115 59.0 100.0 0.0 0.0 31.0 210 112.9 19119 167 178 67 19119 73 59.9 72.5 95.5 98.6 99.0 9.2 80.9 96.7 19119 99 19)49 1714 5 APR 21 APR 1950 1950* 1950* 18 NOV 1950* 19 DEC 1950* 378 112 722 255 JAN 1951 9 JAN 1951 31 JAN 1951 158 62 79 1 Percent Spent 1111 95.7 16.0 143.1 514.11 69.14 77.2 *Sample size and percentage of spent females represent averages for data obtained on several closely spaced collection dates. 314 Richardson 1979). Laroche Richardson and back-calculated (1979) English sole spawning times for several years based on the presence or absence of larvae in plankton samples and growth rates. it their estimates of larval is now known that these growth estimates are inaccurate and better ones have been obtained using techniques (Laroche et al. MS). aging With these revised growth rates we were able to back-calculate spawning times from distributions. improved reported larval size ae to the variability of ocean currents and of larval growth and survival rates, spawning dates calculated fran iall larvae are more accurate than those obtained fran large larvae. For this reason spawning times which were inferred from larval size distributions were based primarily on the presence of newly-hatched larvae. Juvenile Ehglish sole have been collected in Yaquina Bay by a rnxnber of studies. However these are of limited value for the back-calculation of spawning times due to the large variation in juvenile growth rates, particularly for individuals larger than about 25 mm standard length (SL) (Rosenberg 1980: Fig. 14). we For this reason considered only those juvenile surveys which appeared to adequately sample newly-settled juveniles, 20 mm SL. which are individuals of about Growth equations developed for both the pelagic (Laroche et al. MS) and benthic stages (Rosenberg 1980) of 0-age English soles show that individuals of this size average 2.5 months of age. The majority of 20 mm SL P. vetulus are 2-3 months old, while the youngest individual found of this size s 1.7 months old (Laroche et al. MS) 35 and the oldest was 6 months old (Rosenberg 1980). Using each data aiglish type and inference procedure, we sunrnarized sole breeding activity in Oregon waters for 13 years (Fig. 2). Trends in spawning activity, probably rather accurate, particularly peak because sources were usually consistent. inferences spawning from Certainly some errors are times, different data exist due to the likelihood that all methods of data collection do not yield samples representative of the entire Oregon stock. encountered, When we relied most upon inferences from data of adult gonadal condition, next upon newly-batched larvae, and least upon older or were inconsistencies newly-settled juveniles. larvae Because subjectivity cannot be entirely eliminated, we describe the bases for our conclusions in the Appendix. 36 Inferred spawning times for English sole using data of adult female gonadal condition and surveys of pelagic larvae and benthic juveniles. Spawning is indicated by a solid line and peak spawning is shown by the solid shaded areas. Stippled areas denote that data are inconclusive as to peak spawning times and dotted lines signify that data are inadequate for any spawning inferences. Figure 2. .4: '947 '949 '949 1950 1950 '95' 1970 1970 1971 '97, 1972 1972 '973 '973 1974 '974 1975 1976 '977 '977 1978 '979 JASON DJ FMAMJ MONTH 37 Developnent of Spawning Simulation tbdel cogenous factors which may be involved in the reproductive timing of marine fishes include photoperiod, temperature, salinity, ocean currents and food quantity and quality (Brett 1970). These variables may be classified into ultimate and proximate environnental factors (Sadleir 1973). tlLti.mate factors are those which control reproductive success through their effects on the survival and growth of the young, and influence spawning timing through evolutionary adaptation. These factors are often investigated by laboratory experiments dealing with egg and larval survival and by correlation or modelling studies involving time series of year-class strength and other fishery and envirorinenta]. variables. Proximate factors are the envirormental cues initiating gemetogenesis and subsequent spawning behavior. Temperature and photoperiod have been found to be the principle proximate factors in most fishes (de Vlaniing 1972). In addition, the grunion (Leuresthes tenuis) (Clarke 1925), threadfin (Polydactylus sexfilis) (y 1979), and many others (Johannes 1978) have spawning closely linked to lunar-driven tidal cycles. We attempted to identify the proximate factors responsible for timing English sole reproduction by comparing the total annt.al range in magnitude of several envirormental variables with their range of values over only those months in which spawning occurred (Table 3). For this purpose we had access to monthly mean data of barometric pressure at 146°N, 12t°W, the coastal uplling index at 145°N, 1250W (Bakun 1973), an index of bottom temperature (derived from a relationship with sea 38 Table 3. Total range of values of barometric pressure, daylength, and indices of upwelling and bottom temperature over al]. months and over only those months in which spawning occurred. Factor Barometric Pressure 46°N, 124°W Upwelling Index )45°N, 125°W Bottom Temp. Index at NH-15 1 'N, 1011.1-1027.0 mb 8.75-15.5 h Dayl ength 45°N )4)4039 Total Range 12)4°27.)4'W -212 - +106 m3/s/100 m 6.60-11.19 C Range during Spawning 1012.3-1027.0 mb < 14.0 h most <+3m3/s/100 m most > 8.00 C 39 level) at a station (NH-15) over the 100 m isobath off Newport (Kruse and Huyer MS), and bimonthly values of dayl ength at 45°N (Beck 1968). We chose these variables because they were most likely to be related to English sole temperature reproductive cycling. previously As mentioned, and photoperiod are the common proximate timing factors of other fishes. Upwelling could be important to English sole, due to its relationships with current velocity. it is related variables such as food produciton, temperature and to local weather patterns. photoperiod, upwelling, and bottom reproduction, since Comparisons suggested that temperature might at related be to spawning activity occurred only over a portion of the total range of these variables (Table 3). occurred because Baranetric pressure could also be involved, daylengths greater than Little spawning activity of light, which at 145°N h 14 corresponds to the period spanning late April to late August. Possible inhibition of spawning activity by cold temperatures is suggested not only because most spawning seems to occur at temperatures greater than 8 C, but also since little spawning occurred at values of the upwelling index greater than 3 m3/s/100 m of coastline. We searched for other associations such as correlations between the intensity of spawning and the magnitodes of these variables, but no further relationships were English sole revealed. Next we took a more analytical spawning approach. activity is so variable, it is improbable that photoperiod is responsible for its interannual variation. is most Since likely to Instead, shelf temperature be the primary proximate timing factor. In other fishes temperature can have at least two regulatory effects on reproduction. It may control the rate of maturation (Hela and Laevastu 1961; Brett 1970; and others) or it may act as a releasing factor (Brett 1970; Hempel 1979; and others). Laboratory experiments are ccmmoni. y used to investigate the temperature control of spawning. However, since it is desirable to be able to account for the variable spawning activity of glish soles in their natural envirorinent, we attempted a different approach. First we suggested various hypotheses about temperature control of spawning and described them by mathematical relationships. Then we incorporated these relationships into a simulation model which could be driven by a time series of a bottom temperature index for those years in which empirically determined spawning times were available. This uld allow us to determine whether spawning times simulated using the temperature hypotheses are consistent with the spawning times docunented earlier. Since other physical factors are correlated with deep temperature (Kruse and Huyer MS), conclusions about these hypotheses cannot be made except to evaluate whether or not they are reasonable based on historical records of spawning activity and bottom temperature dynamics. The first hypothesis considered is that temperature controls the rate of gametogenesis. Kreuz et al. (MS) found a negative correlation between annual variations in marginal interopercul un growth (an index of body growth) of young glish soles and mean shelf temperature estimates during the growth season (sunnier). This implies an inverse 41 relationship between growth rate. We suggest that the gonadal develoient rate is also inversely related to and A plot of annual temperature. index of bottom (Fig. 3) temperature does the a close reveal riot glish sole spawning records and an during temperatures somatic the sumner prior relationship, although the three earliest spawning seasons followed three of the four Even if maturation was solely temperature spawning time versus temperature if temperature must coldest a beyond plot of relationship or increase at a threshold certain rate in order for spawning to be initiated. sufltners. a controlled, uld not reveal a close increase spawning to From trends in the dates of the start of peak spawning and the start of minor spawning, we proposed relationships completion date between mean summer temperatures and the of gonadal develonent for most individuals (Fig. 3, line a) and the most rapidly developing individual s (Fig. 3, line b). We next considered a temperature threshold hypothesis suggested to us by Table 3. That is, we proposed that even if gonadal maturation was compi eted, spawning would riot occur until temperature exceeded 8 C. Both temperature computer model. hypotheses to incorporated Each month of simulation subintervals of equal length. temperature were was into divided We assigned the estimated the middle of each month. FORTRAN a into four mean monthly The temperature during any subinterval was estimated by linear interpolation between the values at the midpoints of s.ccessive months. of the bottom maturity would temperature index and be completed (lines We drove this model with records inferred the dates on /nich a and b of Fig. 3) and the dates In W.ç __ I -. LJ I I I A I M ............................................................................... _ ............................................. I S .............. co. 0 rr _oo_ 111 -u (J)-.j A SPAWMNG ACTIVITY BY MONTH F M J D N 0 ctcflC-t 1) i.o 0 C) p. C)CD c- 0 çt - U) I CD CD CD ct0 ct CDC -10 CDp C).C)..CnCD çtQ. Ct Ca 0(1):3 C)uI).0 C) 0 :30) C1. - 0P.ctp. :3p:3 ) i :31- CD P) CDCO ) aCD ' CD :3(p. Z CD W(DCI) .0 Ca -:3 0 0'- .0 ct:jp. I- I-J.1- CD CD 0 CD 00 00 0oq-4 CD CD )'H<.0 (I) .0 CD 1.4:3 :3 :31. (DC). c;ip) c1(D CD CD(DFc P) 0 i- :3 (DC)) g.g.0 1 0_:31-. p)o 0-Cct 0 CD 1D,CDCDEF. CD CD BI- 0- CDCn.CD-. xJ CD(I1 01D c-I. :3 ctP) o g (DCt 00:3 Ct 0 WOctta Ct CD P HCDI- 0.w 0CDP)CD CDI- I-LCD g1) ) 1) Xj 30 FI-' CD çt r 143 thereafter on which spawning bottom temperatures above uld be started based on the inferred in this manner were generally in inferred fran records enpirical lines a and b or improve correspondence. the poor described did clear became It hypotheses were not valid or else that agreement with significantly not that either environmental the those Adjustments to earlier. threshold temperature the of dates of spawning initiation The 8 C. wanning these control of English sole spawning was more canpi ex. We next recalled that the of change of temperature can rate significantly influence fish physiology and behavior. our data rapidly strongly suggested sets that when Reexamination of increased temperature (>0.95 C per month) just prior to the inferred completion time of gonadal maturation, spawning activity was delayed. For example, in 19147_i 9148 the calculated (using a of fig. 3) compi etion date of gonadal maturation for most individuals was early December. The temperature index increased 1 .68 C between November and December, and peak spawning apparently did not occur until late January. increases occurred 1 974-i 975) just prior other in in to years which and calculated maturation completion dates (1950-1951, December activity. 1972-1973, and Large temperature increases (1 .36 C between 1969 and 1 .69 C between October and November doctinented interruptions in peak 1977) also coincided with the only t spawning 1970-1971, peak spawning did not start until sometime later than the maturation dates. November the Similar large temperature In general, the magnitude of increase (>0.95 C) and the number of these increases the temperature between several consecutive months appear to be related to the duration of the delay. In all other years for spawning which spawning data were available, peak activity began near the calculated dates of completed gonadal developuent and pre-spawning temperatures increased less (<0.95 C per month). rapidly this we constructed a third temperature From hypothesis which incli.des these rate effects (Fig. ). All three temperature hypotheses were incorporated into a revised for which a flow chart is (Fig. 5). For expediency we have used shortened notation as follows: t - present date, t - completion date of gonadal developnent, T(t) - present spawning model shown temperature, Dt - delay in spawning caused by a temperature increase froni month t, t-1 to month and - the actual delay expected D considering temperature increases over the past several months. equation such as t Pn t1 is analogous to a FORTRAN assigrnent statement and replaces the present value of t with the value t+1. The model is a monthly basis, but spawning dates are interpolated to the precision of .25 months. In the model the question "Is Spawning run on completed?" is answered in to ways. Peak spawning is completed if it has occurred for tw months or if the date is later than early For of lower intensity, spawning is completed if the present spawning date is later than early y. The spawning model including resulted in y. good dates of peak parameterizat ion all three temperature simulated and observed starting agreement between spawning. were In necessary hypotheses fact, to only minor changes in achieve the best possible 45 Hypothesized relationship between the rate of increase in mean monthly temperature and the duration of the delay in the spawning Figure 4. time. t+3 = = = C,, = ;; t+1 0.0 2.0 1.0 Increase in Temperature between Previous Month, t-1, and Present Month, t (in°C) 3.0 Flow ch Figure 5. in the text. 147 predictions fran these hypotheses. By adding a constraint that peak spawning could last no longer than two months for any one spawning year (July to June), we could also account for the dates when peak spawning was terninated. The set of hypotheses yielding the best agreement between simulated and observed spawning activity (Fig. 6) re: (1) the earliest possible spawning time is given by b and the earliest possible peak spawning time is given by a in Fig. 3; below 7.8 C; (2) no spawning occurs and (3) spawning does not occur in a particular month if the mean monthly temperature increases by more previous month. The length of the than 0.95 C fran the delay in spawning is linearly related to the rate of temperature increase (Fig. 14). Whether or not spawning actually occurs at this later time would again depend upon (2) and (3) and the current temperature. Rapid increases in temperature also cause a cessation of spawning activity if spawning had would already begun. In such a case spawning would restart later according to these same rules. We added the rule that if peak spawning is interrupted (by a large temperature rise), it until one month later. In our simulations (lines a spawning. and b would not begin again found that the maturation rate hypothesis of Fig. 3) set the limits to the earliest dates of The hypothesis about rapidly increasing temperatures was of primary importance as it frequently delayed or interrupted spawning. It also was responsible for the correct mod eli ing of the apparent bimodal spawning seasons. The activity in the 1969-1970 and 1977-1978 spawning threshold hypothesis was usually responsible for L8 Figure 6. Comparison between observed (0) spawning records and those predicted (F) when all three tnperature hypotheses are incorporated into a simulation model driven with bottom temperature estimates. A distinction is made between spawning (solid line), peak spawning (solid shaded areas) and probable peak spawning (stippled areas). A dotted line indicates no data. -1 948 947 01 948 1 or 1 950 1949:E 1950 - . 1- 1 1951 970 1 I970F 97! 97IF l972 972 973 F 1974 973 1 I974Pf .. 977 976 1977 - 1978 1 l978p 11979 A SO M DJ FMAMJ MONTH 49 terminating spawning activity in the spring or summer. 50 Discussion Off Oregon Parophrys vetulus spawn intermittently over an extended breeding season. We have searched extensively for the proximate factors regulating English sole reproductive cycling by comparing of series factors. seems spawning activity off Oregon and several envirorinental Barometric pressure, which is related to play no such role. time weather to patterns, Although day lengths greater than 114 h of of gametogenesis, light might preclude spawning or cue the initiation it does not appear that photoperiod can be used to explain large shifts in English sole spawning times. accountable by bottom temperature rel ationship with Neab Bay sea hypotheses of temperature Spawning instead seems to be primarily Support level). control, dynamics because (inferred is they given result Iran to a three in rather accurate simulation of spawning when incorporated into a computer model driven by records of a bottom temperature index (Fig. 6). However, since bottom temperature is correlated to other physical factors (Kruse and Huyer MS), it is possible that a simulation model incorporating hypotheses about roles of other result factors in in satisfactory spawning simulation. reproduction To also It is almost certain that other factors operate in concert with temperature control. will to affect spawning conclusively distinguish the effects of temperature fran these other factors, laboratory experiments should be conducted. It does seem reasonable that the rate of maturation is inversely related to the temperatures experienced during the sunnier (May-August). Gonadal develonerxt probably occurs during this time and it is known 51 that somatic growth is most temperatures (Kreuz et al. been MS). of season cool Negative correlations have previously found between annual variations in marginal interoperculxn growth in young English soles and mean summer In this during rapid other species on estimates. temperature has various effects on rates of gonadal deveJ. oçnent (de Vlaming 1972), effects temperature bottom different having sometimes stages of gametogenesis (Phsan 1966; Weibe 1968). compl etel y opposite in Since anomalies of bottom any one species temperature and the coastal upwelling index are inversely related (Kruse and Huyer M3), colder summer temperatures and stronger upwelling may lead primary and greater to secondary production and increased availablity of English sole prey items, including polychaetes, amphipods, molluscs, ophiuroids and crustacea (Kravitz et a.l. 1977). Relationships between feeding and maturation rates have been identified Kinne 1960; and others), so it in other possible is fishes (Gross 1949; that food production operates with temperature to determine the maturation rates of English soles. In any case this species has presumably evolved physiological mechanisms providing for optimal somatic environmental conditions existing and during gonadal growth at the the summer (including cold temperatures), when productivity is high. We also proposed that few or no P. vetulus spawn colder than Schroeder 1953) (Ware 1977; Lett 1978), detenninant of spawning temperatures In some species such as Atlantic cod, Gadus about 7.8 C. morhua (Bigel ow and at a and Scomber scombrus threshold may be the primary temperature activity. mackerel, Ahlstrom (1965) felt that 52 temperatures between 13-18 C were responsible for the time and length of the California sardine (Sardinops sagax) spawning temperatures Perhaps season. out of this range may operate by inhibiting production or release of honnones responsible for initiating breeding behavior. Finally we hypothesized that temperature greater in monthly mean increases bottom than 0.95 C delay or interrupt spawning activity. The magnitude of the increase and the length of the delay are suggested be to linearly related. clear, although it is The tuechanins behind this response are not widely known that deviations of short-term temperature can produce physiological and behavioral changes in fishes. It is possible that relatively small English increases soles physiologically are course temperature variations of 14 C or less over the year (Huyer 1977; Kruse and Huyer MS). of the (1 972) found that rising temperature retard it. a general sudden increases Alternatively, sharp increases in Oregon continental shelf temperatures may be associated with shifts and Leggett and accelerated upstream American shad (Alosa sapidissima) migration but that could entire Rapid temperature increases might also alter English sole spawning migration patterns. itney by since adults experience temperature, in stressed deterioration of the set in weather patterns of conditions required by English soles for spawning. Before our hypothesized relationships between shelf temperatures and reproductive cycling are accepted, they should be validated through controlled laboratory experiments. are However, in their present form they certainly useful for simulating English sole spawning activity, as 53 we have shown. This is significant, because year-class strength appears to be largely determined by environmental conditions prevailing prior to spawning (Hayman and Tyler 1980) and during history spawning stages (Ketchen 1956). Thus our valuable to investigations of the mechanisms by which factors operate. Once the early life model these will be physical these mechanisms are understood, forecasts of iglish sole availability can be made in advance incorporated into future managnent strategies. of recruitment and 5Lt Conci usions The first study presented here adds to our of the understanding oceanographic processes occurring along the Oregon coast. Although the Bakun's relationships between deep temperatures, coastal sea level and upwelling index are not totally the unexpected, significance of these relationships is docunented for the statistical first time. It is felt that the relationship between sea level and temperature will be useful estimates, to researchers in and I have found glish sole spawning model, (Microstomus pacificus). fishes and their those glish soles and Dcver should help managers fishery productivity in activity and those related to to distinguish related to fishing the environment. The second part of this thesis contributes glish soles n understanding of such interactions between environment changes Albert temperature index to be correlated to this annual variations in the groith of young between temperature shelf particularly during periods of sporadic empirical records. In addition to being useful to the Tyler of regular need to our knowledge of sole life history and perhaps of similar species living in the Oregon upwelling system. It is hoped that future studies can be conducted to validate the proposed hypotheses of temperature-controlled spawning and to assess the coupled effects of other food avail ability and photoperiod. factors, such as Predictions made from the spawning model developed here have already been valuable to an investigation of the Tyler. glish sole recruitment process conducted by myself and Albert 55 References Ahistran, E.H. A review of the effects of the environment of 1965. the Pacific sardine. Inter. Pub. Fish. Spec. Northwest Ati. Comm. 6:53_7LL Ahsan, S.N. Effects of tnperature and light 1966. changes in the sper'matogenetic activity of J. )44:161-171. Couesius plctnbus. Bagenal, T.B. S.D. on Can. Zool. the cyclical the lake chub, A short review of fish fecundity, p. 89-111. 1967. (ed.), Gerking basis of freshwater fish biologival. The In production. John Wiley and Sons. New York. Bakun, A. Iinerica, Bakun, A. Coastal 1973. 1946-1971. Tech. NOAA. Rep. i].y and weekly upweij.ing 1975. North uplling indices, America, west coast of North NMFS. 103 p. indices, west coast of NOAA Tech. 1967-1973. SSRF-671. Rep. NMFS. SSRF-693. 11)4 p. effective niinber of independent observations in an autocorrelated time series. J. Bayley, G. V., and J.M. Haxnrnersley. Roy. Beck, S.D. Stat. Soc. Ser. B The 19)46. 8:18)4-197. Acadnic Press, Insect photoperiodimn. 1968. New York. 288 p. Bigelow, H.B., and W. C. Maine. Bourke, R.H. Schroeder. Fish. Bull., U.S. 1969. 514 an estuary. p. Fishes of the Gulf of 53(7k):577 p. Monitoring coastal effects within Corvallis. 1953. M.S. upwelling by measuring its thesis, Oregon State Univ., 56 Brett, J.II. Temperature - fishes, 1970. rine ecology, vol. I. (ed.), Budd, P.L. Wiley - Interscience. and Develornent of the eggs l94O. California fishes. Calif. New York. early larvae of six Fish Dep. 0. Kinne In p. 515-616. Game, Bull. Fish. 56:53 p. Clarke, F.N. fish The life history of Leuresthes tenuis, an atherine 1925. with Fish. tide Bull. controlled spawning habits. 10:1-22. O.ishing, D.H. 1969. The regularity of the fishes. Cons. Inter. O.ishing, D.H. 1975. Marine ecology and Press. 1vis, R.E. Fish Game, Calif. New York. spawning Mer., J. Explor. Cons. fisheries. of some season 33:81-92. Cambridge 278 p. and Predictability of sea surface temperature 1976. level pressure anomalies over the North Pacific Ocean. Oceanogr. de Vlaming, V.L. 1972. Eifield, D.B., and J.5. of monthly mean Allen. 1970. A during 1949. Biol. Fish. J. 1980. :131-10. On the structure dynamics and sea level anomalies along the Pacific coast of Phys. J. statistical Oregon Oceanogr. study coastal Oregon State Univ., Corvallis. Gross, F. Phys. J. reproductive &ivirorinental control of teleost North and South America. temperature sea 6: 2k9-266. cycles: a brief review. Fisher, C.W. Univ. of' winds 10: 557-578. and upwelling. J. ter thesis, M.S. 67 p. Further observations on fish growth in sea loch (Loch Graiglin). sea Mar. Biol. a fertilized Assoc., U.K. 28:1-8. 57 Harry, G. Y., Jr. Time of 1959. fecundity of the vetulus, respectively). Hayman, R. A., and A. V. of Dover Fish Comm. Tyler. sole and Microstomus and jordani, Oreg. and maturity, at petrale, and Dover soles (Parophrys English, Eopsetta length spawning, Briefs 7:5-13. Res. Environment and cohort 1980. English pacificus, Trans. sole. strength Fish. Am. Soc. 109: 5k-68. Hela, I., and I. Laevastu. News (Books) Ltd. Hempel, G. London. Washington Sea Grant Publ. Hewitt, G.R. Seattle. Oregon State University, Corvallis. Goldberg. Hunter, J. R., and S. R. U.S. Huyer, A. stage. 70 p. of the inshore trawl fishery off Oregon. fecundity egg Seasonal changes in English sole distribution: 1980. analysis Fishing 137 p. Early life history of marine fish - the 1979. Univ. oceanography. Fisheries 1961. 1980. M.S. an Thesis. 59 p. batch Spawning incidence and in northern anchovy, Fngraulis mordax . Fish. Bull., 77:641-652. Seasonal 1977. density over Oeeanogr. variation the continental shelf off salinity, Oregon. and Limnol. 22: k42-)453. Huyer, A., and R.L. nith. 1978. Physical characteristics of Pacific Northwestern coastal i.aters, p. marine plant biomass of the State Univ. temperature, in Press. 37-55. Pacific Corvallis. In R. Northwest Krauss (ed.), The coast. Oregon 58 Huyer, E.J.C. A., transition in J. Geophys. Res. Johannes, R.E. currents Mar. Fish. Ketchen, K.S. sole continental shelf. Biol. Fishes 3:65.-84. glish sole tagging off California. Pacif. 7:15-33. Factors inf1i.ncing the survival of the laon (Parophrys vetulus) in Hecate Strait, British Colunbia. Fish. Kinne, 0. &ivir. Comm., Bill. 1956. Oregon the over spring The 1979. 8:6995-7011. Results of 1969. nith. R.L. Reproductive strategies of coastal marine fishes 1978. in the tropics. Jow, T. and Sobey, Res. Board Can. 1960. euryplastic salinities. Kravitz, M.J., W.G. 13:647-694. Growth, food fish exposed Physiol. J. in a tnperatures and different to 33:288-317. Zool. Pearcy, and conversion food and intake, Gum. M.P. 1977. Food of five species of cooccurring flatfishes on Oregon's continental shelf. Fish. Kreuz, Bull., U.S. K.L., A.V. Variation 74:98)4-990. Tyler, Thans. Kruse, G. H., and A. temperatures, Pmer. Huyer. coastal off Newport, Oregon. Krygier, E.E., and W.G. waters. R.L. Demory. MS. in growth of ]ver sole and English sole as related to upwelling. glish and Kruse, G.H. MS. Fish. &c. The relationships between near-bottom sea level and the coastal upwelling index Lirnnol. Pearcy. MS. Oceanogr. (in press). Distribution sole (Parorys vetulus) (in prep.) (in press). in and abundance of Yaquina Bay and offshore 59 Laroche, J.L., and S.L. English larval Richardson. sole, Winter-spring abundance of 1979. River and Cape Blanco, Oregon during occurrences Sd. between the Columbia vetulus, Paropirys of three other pleuronectids. notes with 1972-1975 Estuar. on Mar. Coast. 8:455-476. Laroche, J.L., S.L. growth of Richardson, and Rosenberg. A. and Age MS. a pleuronectid, Parophrys vetulus, during the pelagic larval period in Oregon coastal waters. Bull., U.S. Fish. (in press). Laroche, W.A., and R.L. Holton. 1979. Occurrence English 0-age of sole, Parophrys vetul us, along the Oregon coast: an open nursery area? Northwest Sd. Leggett, W.C., and R.R. 53:94-96. Whitney. migrations of American shad. Lett, P.F. Water 1972. temperature the 70:659-670. Bull., U.S. Fish. and A comparative study of the recruitment mechanins of 1978. cod and mackerel, their interaction, and its implication for dual stock management. Lett, P.F., A.C. biomass Ph.D. thesis, ]lhousie Univ. Kohler, and D.N. and Fitzgerald. 125p. Role 1975. of stock in recruitment of southern Gulf of St. temperature Lawrence Atlantic cod, Gadus rnorhua. J. Fish. Res. Board Can. 32:1613-1627. May, R.C. Lunar 1979. sexfilis, in Hawaii. rers, K.W.W. areas 1980. in spawning Fish. of the Bull., U.S. threadfin, Polydactylus 76:900-9O4. An investigation of the utilization of four study Yaquiria Bay, Oregon, by hatchery and wild juvenile 60 salmonids. Morse, W.M. M.S. 1980. thesis. Oregon State Univ. Corvallis. 234 p. Spawning and fecundity of Atlantic mackerel, Fish. Scomber japonicus. M.ndy, B.C. Bull., U.S. 78:103-108. Yearly variation in the abundance and distribution of MS. fish 1 arvae in the coastal zone off Yaquina Head, Oregon, from June 1969 to August M.S. 1972. thesis, Oregon State University, Corvallis. (in prep.) Qasim, S.Z. Time and duration of the spawning season in 1956. marine teleosts in relation to their distribution. Explor. Mer, J. Reid, J.L., and A.W. Cons. J. Ocean. Richardson, S.L. Oregon: August 1976. The effect of the geostrophic sea elevations in the Northern North Pacific Geophys. 1977. Res. 81:3100-3110. Larval fisries in ocean waters off Yaquina Bay, abundance, distribution and seasonality, January 1972. Sea Inter. Cons. 21:1)414_155. Mantyla. flow upon coastal some Grant Ccll. Frog. Fubl. 1971 to ORESU-T-77-0O3. 73 p. Richardson, S.L., and W.G. Pearcy. 1977. Coastal and oceanic fish larvae in an area of upwelling off Yaquina Bay, Oregon. Fish. Bull., U.S. Bicker, W.E. Res. Roden, G.I. the 1973. 75:125_1L5. Linear regression in fishery research. J. Board Can. 1960. west 65: 2809-2826. 30:kO9_314. On the nonseasonal variations in sea level coast Fish. of North Pmerica. J. Geophys. along Res. 61 Rosenberg, A.A. Thesis. Sadleir, H. estuarine in vetulus, of Growth 1980. English juvenile and nursery areas. coastal open Oregon State University, Corvallis. New York. M. S. 51 p. Press, Academic The reproduction of vertebrates. 1973. Parophrys sole, 227 p. Sciranaiimano, F., Jr. suggestion A 1979. presentation tne for correlations and their significance levels. Oceanogr. Phys. J. of 9:1273-1276. Sutcliffe, Jr., W.H. Correlations of Ware, D.M. ine. Fish. Board Can. G.E. production. 1968. reproductive 1974. t.vis. J. mackerel, Fish. The Laboratory studies 1967. and growth of biological Jobn Wiley and Sons. basis of on p. 175_21L1. fish, freshwater Res. the In fish New York. The effects of temperature and day length on the physiology of the viviparous seaperch, Cymatogaster aggregata Gibbons. Zar, J.H. of Atlantic in relation to the plankton. bioenergetics, S.D. Gerking (ed.), Weibe, J.P. size 34: 2308-2315. Warren, C.E., and feeding, 1977. 3:19-30. Board Can. Res. Spawning time and egg scombrus, Scctnber Muir. B.S. of fish catch and envirormental factors in the Gulf J. 1977. and Drinkwater, K. Can. J. Zoo].. Biostatistical analysis. CLiffs, New Jersey. )46:1207-1219. Prentice Hall. Englewood 620 p. Zweifel, J.R., and R. Lasker. 1976. Prehatch and posthatch growth fishes-a general model. Fish. &tll., U. S. 74:609-621. of appendix 62 Appendix. Spawning activity by season. 19147-1 948 The gonadaJ. condition of English sole females were landed We had access sampled by the ODFW during 19147_1951 (Harry 1959). to the raw data collected during this time period Astoria in (Table No 2). samples were obtained in 19147 and collections were made only in January and March of 19148. Approximately 140% of the spawning total activity Spawning was terminated by occurred between mid-January and mid-March. the middle of March. 19148-1 9Lt9 Adult females landed in Astoria were sampled frequently during the 19148_1949 spawning season (Table middle of November and early March. 2). Spawning occurred between the was period The heaviest spawning fran early December to late January. 19149-1950 Spawning began prior to the first sampling date in mid-November 19149 and terminated in about the middle of April 1950 (Table 2). of peak spawning activity cannot be accurately determined, samples were taken in December or January. Ltes since no About 70% occurred sometime between mid-November and early February. 1950-1951 Gonadal condition duration of the females appear during 1950-1951 was not spawning season (Table 2). to have spawned prior to sampled for the Approximately 16% of the the first sampling in 63 mid-Novanber and only 1950 31 January 1951. About 60% 77% had spawned by the last sampling date, of the spawning activity occurred between the middle of Novnber and late January. 1969-1 970 Using revised growth estimates (Laroche et al. MS), collections of 2-3 mm SL English sole larvae (Mundy MS) spawning season began in early Noviber 1969. show that the 1969-1970 Spawning appears to have stopped in mid-Decanber, resiined in mid-January and finished compi etel y by the end of March. Based on larval abundances, peaks in spawning intensity are indicated for mid-Novnber In 1970 beam 1969 and February 1970. juvenile surveys were also conducted in Yaquina Bay using trawls (Krygier and Pearcy MS). Individuals approximately 20 mm in length were collected in mid-January to early February. about Allowing 2-2.5 months to reach this length, this confinns spawning during the month of November. Juveniles of this age were also collected (and in greater abundance) from late March to late May, which indicates that additional heavy spawing occurred from mid-January through late March. However, we place more confidence in spawning inferred from larval data, which clearly shows spawning to be heavier in February than in March. 1970-1 971 nall (2-3 mm SL) larvae first appeared in late (t4mdy MS), December which means that spawning began in mid-December. data (Mndy M5; Richardson 1977; Richardson and Pear'cy 1977) also 1970 Larval show 6)4 that spawning early March. intensity increased many fold frcm late January through Spawning activity seems to have stopped late in April, since 5-8 imn SL individuals were collected no later than May. A survey using beam trawl s in Yàquina obtained y (Krygier and Pearcy This a few juveniles less than 20 mm SL in mid-January 1971. to mid-Novnber, means that some spawning must have occurred in early contrary to the MS) Significant lack of such evidence Iran larval data. nunbers of small juveniles were obtained Iran late February through the end of June. Spawning times inferred fran these later collections are Since essentially identical with those inferred fran larval data. greatest the nunbers of these young soles were observed between mid-March and mid-May, the peak spawning times inferred Iran juvenile both and larval data also closely agree. 197 1-1 972 1977) indicate that spawning began in mid-Septnber 1971 and continued through late February 1972. been Pearcy and Larval studies 04.indy MS; Richardson 1977; Richardson in tcember. Peak spawning Al though no samples activity appears were taken to have in January or February 1972, heavy spawning likely did not occur during these months, since the nunbers of 1-2 month old larvae collected in March were low. Beam trawis (Krygier and Pearcy fish MS) less than 20 mm SL in late November. early March when saznpl ing was terminated. first encountered juvenile They were collected through This suggests spawning from the middle of September 1971 through at least the end of January 1972. The greatest numbers of juveniles were taken Iran early to late 65 February, indicating peak intensity in spawning Thus December. from juvenile data are highly supportive of conclusions drawn larval samples. 1972-1973 Information available regarding only one fran for spawning data Based 1973. during 17-29 early March and on revised growth rates (Laroche et al. presence of larvae up to 20 mm SL in March samples activity from season 1972-1973 is source (Laroche and Richardson 1979). Larvae were surveyed using bongo tows April the MS), the spawning No statement can be made January through March. about possible spawning prior to January. indicated 1 7-26 Fran the presence of very large nunbers of 7-1)4 mm SL larvae in March samples and expected ages of these individuals (Laroche et al. early February for MS), peak spawning to early March. is indicated Spawning appears to have tapered off by late April, although it is possible that some spawning occurred after this last sample date. 1973-1 97)4 large Laroche and Richardson (1 979) reported that of running ripe 20 October 1973. March 197)4 and concentrations spent adults were found off the Oregon coast on Larval surveys were conducted only in the middle of (Laroche and Richardson 1979). At this time newly-hatched soles were sparse and in the 2-8 mm SL size range. This indicates that minor spawning occurred from mid-February to mid-March arid little or no spawning fran at least mid-January to mid-February. t size groups of 0-age juveniles along the The collection of coast in 197)4 also suggested fall and winter-spring periods of spawning (Laroche and Hol ton 1979). Based this information, it can be inferred that on spawning was intense in early October, absent fran mid-January to mid-February and minor fran mid-February to mid-March. 19714_i 975 Larvae were Richardson 1979), only on surveyed V4-16 March 1975 (Laroche and and large numbers were obtained on these dates. The presence of newly-hatched and 60 day old larvae indicated that spawning began at 1 east by mid-February mid-March. The predctninance of mid-February to early March. and continued at least through 1975 day olds suggest a peak 8-25 from No statement can be made about possible spawning prior to mid-January or after mid-March. 1976-1977 A juvenile sampling program (Krygier and Pearcy MS) was conducted in Yaquina Bay from 24 April to 2 July 1977. Individuals less than 20 mm SL were collected on all dates suggesting that spawning began at least by late February and continued through early May. The greatest numbers of larvae less than 20 mm SL period were taken from 22 May to 14 collected during any sampling June. This uld suggest a peak in spawning during late March or early April. aie to the shortness of the sampling period, however, one cannot conclude that this would represent the peak spawning time over the entire season. A beach seining program (Myers initiated in late June 1977, of 19-22 mm fish. None were 1980) collected only very slight numbers collected after late June indicating that spawning did not extend past 67 early No conclusion can be drawn about possible spawning prior to y. mid-January. 1977-1978 Hewitt (1980) adult female gonads fran October sampled 1977 on the percentage of ripe stage III (the most advanced stage of ripeness) or spent females, his data show that through spawning rch Based 1978. began at least by early October, continued moderately through January, and peaked strongly in February. were spent by 1 March of the females Almost 95% 1978. Beam trawl sampi es (Ho senb erg 1 Krygier and Pearc y MS) of small juveniles in Yaquina Bay indicate spawning fran mid-October through early April. Although trends are difficult to discern from these samples, spawning can be inferred to be intense in the middle to late October and heaviest in January. Beach seine samples in Yaquiria Bay (Myers individuals less than 20 nn SL cm mid-December through late April 1978. 1980) 1977 first encountered and collected them A very small ntznber were also obtained late July to early August. from This infonnation implies that spawning occurred fran early October through the end of February, with a minor amount in late May or so. A peak in spawning activity appears to have occurred fran mid-December through early March. Each of the 1977-1 978 studies indicate similar spawning times. Clearly spawning began at least by early October and continued in varying intensity through early May. and The precise dates for the start finish of the major peak for this season are uncertain. However, 68 each study indicates heavy spawning in January and/or February. 1978-1979 Beach seine samples (Myers 1980) spawning na.11 began at least by mid-August 1978. SL were caught as early as 28 October. occurred of between mid-September and show that juveniles Some fish less than 20 mm Peak spawning appears Young mid-October. have to soles were caught through the last sampl e date (10 December 1 978). Beam indicate trawl spawning samples (Rosenberg 1980; Krygier and Pearcy MS) to have occurred fran early September and continued through mid-March. Peak spawning is indicated for mid-September through mid-November. Both of these juvenile studies yield compatible spawning times. Using both, it seems that inferences spawning about began in mid-August, peaked from mid-September through mid-November and ended in mid-March.