Technical Report Series
32
32
Number 73-3
.
....
CHEMICAL AND BIOLOGICAL SURVEY
OF THE SAVANNAH RIVER
ADJACENT TO ELBA ISLAND
by
Robert R. Stickney
and
David Miller
31
31
Georgia Marine Science Center
University System of Georgia
Skidaway Island, Georgia
81
CHEMICAL AND BIOLOGICAL SURVEY OF THE
SAVANNAH RIVER ADJACENT TO ELBA ISLAND
by
Robert R. Stickney
and
David Miller
Skidaway Ins t itute of Oceanography
P. 0. Box 13687
Savannah, Georgia 31406
February 1973
The Technical Report Series of the Georgia Marine Science Center
is issued by the Georgia Sea Grant Program and the Marine Extension
Service of the University of Georgia on Skidaway Island (P. 0 . Box 13687,
Savannah, Georgia 31406). It was established to provide dissemination
of technical information and progress reports resulting from marine
studies and investigations mainly by staff and faculty of the University
System of Georgia. In addition, it is intended for the presentation of
techniques and methods, reduced data and general information of inte rest
to industry, local, regional, and state governments and the public.
Information contained in these reports is in the public domain. If this
prepublication copy is cited, it should be cited as an unpublished
manuscript.
INTRODUCTION
The present study was supported by a grant from the Southern Natural Gas
Company which plans to constr uct a regasc:ification plant on Elba Is Land in the
Sav:mnah River (Figure 1) where liquifi d natural r.ras (LNG) will be off-loaded
from ships , r .gassifi d and piped to distribution ·:-: enters.
The initial plan called
for water from the Savannah River to be pumped into the plant where it would be
used to carry away the thermal debt incurred in converting the LNG from the
liquid to the gaseous state.
This process water, when returned to the river,
was expected to be cooled approximately 5°F below ambient river temperature.
No other changes in or additives to the process water were expected or comtemplated.
The present study was initiated to collect information on the basic water
chemistry and faunal assemblages in the river adjacent to Elba Island prior to
construction of the plant.
The results of this study are intended to provide a
data base for the water quality and biota in this section of the river under
presently existing conditions of pollution from domestic, municipal and industrial sources against which any environmental effects of the regassification
operation may be measured in the future.
The authors would like to express their appreciation to Messrs . Daniel
Perlmutter, Douglas Mullis and Gary Taylor for field and laboratory assistance .
DESCRIPTION OF THE STUDY AREA
The Savannah River, separating Georgia and South Carolina, flows through
a concentration of industrial and municipal areas during several of the last 25
2
miles of its course before entering the Atlantic Ocean.
Th e City of Sa vannah is
located approximately 10 miles above the ri ver entranc e .
Located above, and
adjacent to the city are several industrial plants involved in food, paper and
chemical processing.
The Port of Savannah receive s nu m erous vess els daily.
Access to the Port facilities is provided by a ship channel approximately 150
meters in width and 12 meters in depth.
r!'his chann e l, currently being increased
to a depth of 15 mt·ters, is dredged and othe rwis t' rr.:.aintained by the
. S. Army
Corps of Engineers.
With the exception of one set of data obtained near the mouth .of the Savannah
River (Figure 1, station 5), the sampling stations were located near Elba Island .
Station 1 was established in the South Channel of the Savannah River behind Elba
Island . The water depth at this station varied between three :mel four meters
depending upon the stage of the tide (the tidal range in the coastal region of
Georgia is between two and three meters).
The sediments, typical of Georgia
estuarine areas, consisted of clay and mud rich in organic matter.
On ebb tide
some of the flow of the main channel Savannah River is diverted down the South
Channel, through station 1 .
Station 2 was located directly upstream from a large chemical plant, near
Fort Jackson.
Oil Company storag·e facilities were also located near this station.
Water depth at station 2 and the following stations was 12 to 14 meters at low tide
and up to 16 meters at high tide.
Station 3 was established in the immediate
vicinity of the proposed construction site on Elba Island. At present, there are
no obvious sources of domestic or industrial effluents into the river downstream
from station 3 until the immediate vicinity of the ocean . Station 4 was established
3
just downstream of the eastern end of Elba Island. On one occasion a fifth
station (station 5) was occupied for the purpose of obtaining data on the fish and
macroinvertebrate populations.
This station was established about 2 miles
downstream from station 4 .
During past years the Savannah River has been used for the disposal of
various types of industrial, municipal and ship wostes . The city of Savannah
is presently installing a sewage treatment plant and the major industries along
the river have initiated various types of pollution control programs.
The
Savannah River was closed to commercial fishing along much of its lower
reaches during 1971 due to excessive levels of mercury.
Part of the river was
reopened during 1972 but concern about the quality of fishes taken from the
river is still expressed by local fishermen.
Sport fishermen also complain
about the "oily' taste of fishes caught in the Savannah River.
The Savannah River
is utilized by striped bass (Marone saxatilis) as a spawning area during the
spring . Sportsmen, in addition to angling for striped bass, are also interested
in the channel bass or red drum (Sciaenops ocellata) which attain large size in
the Savannah River . Other species of sport and commercial interest are also
present seasonally.
The coastal area of Georgia is characterized by vast expanses of marsh grass
(predominantly Spartina alterniflora intertidally with Juncus sp. on higher
ground).
The Savannah River has been deeply channelized throughout the extent
of the study area . Virtually all of the marsh has been eliminated along the river
and has been covered with high spoil banks. Both sides of the river have been
spoiled and maintenance dredging is required at frequent intervals to maintain
4
the ship channel, thus adding to the dimensions of the spoil banks.
METHODS AND MATERIALS
Cruises were undertaken at monthly intervals beginning January, 1972 and
terminating December, 1972. In April, July and October diurnal samples were
obtained for water chemistry from each station at three hour intervals. Both
routine monthly and diurnal water samples were obtained through utilization of
either a Van Dorn or Kemmerer water sampling bottle. Samples were collected
at the surface, bottom and at two meter intervals between.
Temperature was determined immediately after collection of each sample
through use of a mercury-in-glass thermometer. Salinity was determined to the
nearest part per thousand (ppt) by refractometry.
The salinities obtained with
the refractometer were checked and verified during one cruise with an induction
salinometer.
Measurement of pH was done either in the field or in the laboratory using
a Corning battery operated pH meter. Oxygen was determined by azide modification of the Winkler titration in most cases (APHA 1965); however, during the
latter few months of the study an oxygen meter was used.
Winkler titration of
one or more replicate samples during each month when the oxygen meter was
used verified the readings obtained from the meter.
Sampling of the parameters listed above carried out in this area by other
agencies of federal and local government was not as intensive as that undertaken
by us but provides additional information, especially upstream of our station
(Georgia Water Quality Control Board 1972).
5
A ten minute otter trawl was made at each station during each month with a
6 . 1 meter Wide at the mouth nylon otter trawl with 2. 5 em stretch mesh . The
organisms capturer! were placed in 10% formalin s olution and returned to the
laboratory for examination. All animals were identified to species, counted and
weighed . Individual lengths and weights were obtained in most cases· however,
the data are presented on the basis of pooled dala for the most part, since further
reduction of these data did not appear to add to or modify the conclusions presented
below.
RES LTS AND DISC SSION
Temperature Regime (monthly)
Monthly temperature patterns for stations 1 through 4 are presented in
F igure 2 . Values for surface, midwater and bottom are given in addition to the
mean for the water column.
Values were obtained at two meter intervals, but
are not presented due to the extremely narrow range in temperature with depth .
Standard deviations are included in cases wher e the standard deviation exceeded
2:_0. 500. By comparing the points for any given month among the four stations it
becomes apparent that there was little variation in temperature within or between
stations . In addition, there was no evidence of thermal stratification within any
station . In this respect, the Savannah River is similar to other rivers along the
Georgia coast. None of the other estuarine waters in the area have shown thermal
stratification.
They are, for the most part, shallow and well mixed, thus, no
stratification would be expected.
Temperature readings in excess of 30°C are
common in Georgia estuaries during July and August.
Several areas within a
6
few miles of the Savannah River, Wilmington River and Ossabaw Sound exhibited
30°C temperatures during the summer, 1972. The maximum value obtained
during the present study was 28°C which occurred during August at all stations.
The lowest temperature obtained was 8°C at the two upstream stations (stations
1 and 2) during February, 1972. Stations 3 and 4 had temperatures of 10°C during
February . Several stations in Ossabaw Sound and the Wilmington river, both
within a few miles of the' Savannah River, demonstrated the lowest winter temperatures, 10°C.
There is some indication that the Savannah River does not get
quite as warm as the surrounding area during the summer and th1,lt its winter
temperatures are the same or possibly slightly less than surrounding areas. In
general, the Savannah River temperature regime is not dramatically different from
the surrounding estuarine areas.
Salinity Patterns (monthly)
Salinity patterns at two meter intervals monthly from stations 1 through 4
are presented in Figure 3. Station 1 is a shallow water station which showed a
maximum depth of four meters. Because of the shoalness of this station, little
salinity stratification was evident, although there was a slight tendency toward
increasing salinity with depth during most months.
This station is more typical
of Georgia estuarine conditions where relatively shallow water is well mixed
showing little or no salinity variability.
Stations 2 through 4, located in the middle of the Savannah River ship channel,
showed a high degree of salinity stratification.
The surface water was generally
of low salinity at each of these stations with a tendency toward increasing sur-
7
face values in the downstream direction. Salinity increased steadily with depth
reaching levels in excess of 20 ppt at the bottom of the water column, which
varied in depth from 10 to 16 meters depending upon the month and tidal stage.
Salinity data showed some aberrant patterns. During February, 1972, low
salinities were recorded at all four s tations, with station 3 being the only one
among the four to approach the typical salinity configuration.
The salinity
patterns at station 2 were fairly cons istant during all months with the exception
of February . The normal pattern of increasing salinity with depth was disrupted
during the November, 1972 sampling period at stations 3 and 4 . .The water column
for this set of samples was apparently well mixed from surface to bottom. As
will be shown later, this phenomenon also occurred during the diurnal sampling,
and seemed to be associated with the passage of large ships. Samples taken
within an hour or two following passage of a large vessel show a disruption of
the normal salinity gradient.
pH Determinations (monthly)
The Savannah River receives acid wastes from chemical plant effluents which
appear to affect the pH of the river.
Monthly pH values, surface to bottom at two
meter intervals in stations 1 through 4 are presented in Figure 4.
tained at station 2 were generally acid.
Values ob-
Normal values for Georgia estuarine
waters (based on data taken from the Skidaway River adjacent to the Skidaway
Institute of Oceanogrphy) generally range between 7. 5 and 7. 9. As previously
noted, a portion of the ebb flow of the Savannah River moves down the South
Channel, thus allowing the low pH water access to station 1. In general, pH
8
values obtained from the surface at stations 2 through 4 were slightly acid,
although some neutral to slightly basic values were also obtained. A slight increase in pH with depth occurred at stations 2 through 4. During more than half
of the sampling period all values obtained throughout the water column at station
2 were acid.
This station is located in close proximi ty to a large chemical plant
which emits acid effluents and the station would be expected to have been influenced
by the discharge from the plant.
The pH values obtained from stations 3 and 4 approached or exceeded neutrality
at some depths during most months.
Exceptions occurred during. February,
March, April and July at both stations when the pH was acid throughout the water
column. In each of these cases the tide was either falling or low , indicating the
possibility that tidal influences were operating.
(Table 1 indicates the tide stage
for each month of sampling). During May, August and December the tide was also
falling or low at the time of sampling and the trend was toward increasing pH with
depth . The pH could not be determined at stations 3 and 4 during December due
to failure of the pH meter in the field. It is not known whether acid discharge is
constantly flowing into the river or is allowed to enter the river intermitently.
A pollution abatement program initiated by the chemical company involved should
effectively remove the acid effluent from the river in the future .
Dissolved Oxygen (monthly)
Dissolved oxygen demonstrated little variation with depth at all four sampling
stations (Figure 5), although in many cases the surface values were slightly higher
than those obtained at two meters. This could be associated with diffusion of
9
atmospheric oxygen into the water. Seasonal patterns in dissolved oxygen levels
were apparent.
These patterns followed temperature to a great extent in that the
high values of dissolved oxygen were recorded during the winter when the water
was cold and low values were recorded during the summer when water temperature
was high . Biologists consider dissolved oxygen levels below 5. 0 mg/ 1 detrimental
to aquatic life.
At station 1 the dissolved oxygen was consistantly b low 5. 0 mg/ 1
during the period from April through September, corresponding with temperatures
above 20 C for that station.
The poorest water quality from the standpoint of dis-
solved oxygen levels was found at station 2 (Figure 5).
alues fell from over
8. 0 mg/1 in February to less than 5. 0 mg/ 1 in March and continued at the lower
levels through September. Values of less than 3. 0 mg/1 were observed in April,
May and June at some depths, and fell below 2. 0 at 4 meters and below during
August. Dissolved oxygen values of less than 2. 0 mg/1 are potentially lethal to
many species, especially if that level pcrs ists for any length of time.
Some increase in summer levels of dissolved oxygen occurred downstream.
At station 3 the August dissolved oxygen level reached a low of 2. 3 mg/1, while
at station 4 the lowest value obtained during the same month was 3. 0 mg/1. Most
of the dissolved oxygen values obtained from station 3 during March through
September were below 5. 0 mg/1, while one or more values in excess of 5. 0 mg/1
were recorded at station 4 during every month except July.
It is likely that the heavy input of both domestic and municipal waste entering
the Savannah River becomes diluted enough for some recovery of the river below
station 2 . Some data from a state governmental agency are available for locations
both upstream
~d
downstream of our stations (Georgia Water Quality Control
10
Board 1972) .
These data indicate that dissolved oxygen during 1970 and 1971 was
very low from a point about 10 miles upstream (near station 3) to about 22 miles
upstream from the ocean during the summer; an area encompassing the waterfront
of the city of Savannah and the bulk of the industrial and port facilities associated
with the Savannah River.
From these data, it appears as though station 2 is at
the lower extremity of the poorest water quality associated with the lower reaches
of the Savannah Ri ver .
Temperature Regime (diurnal)
Diurnal temperature, salinity, pH and dissolved oxygen determinations were
run on 21 April, 19 July and 23 October at three hour intervals.
Problems in
sampling equipment required termination of the 23 October sampling prior to
collection of a complete 24 hour series.
The effects of tidal amplitude on depth
are clear in that the available sampling depth is reduced at low tide (cf. Figure 6) .
Diurnal temperature data for each sampling period are presented for stations
1 through 4 in Figures 6 through 9, respectively. All
dat~
collected at two meter
intervals from surface to bottom are presented in the figures. As was observed
above in the discussion of the monthly samples, there was little variation with
depth within a given station and also little variation between stations during the
same month. In the present case, diurnal temperature variation was generally
slight although a surprising increase in temperature was noted between the first
two sets of samples at station 1 during April (Figure 6).
This phenomenon was not
repeated at any of the other stations during the same month or during any other
month . Shallow waters are more susceptible to diurnal changes than are the
deeper waters such as exist in stations 2 through 4. Diurnal temperature values
11
were relatively constant within any one diurnal sampling period at stations 2
through 4 (Figures 7 through 9, respectively).
Salinity Patterns (diurnal)
Diurnal salinity data from stations 1 through 4 are presented in Figures 10
through 13, respectively.
Only slight variations were observed diurnally at
station 1 (Figure 10) and, as seen in the monthly data presented above (Figure
3), salinity increased only slightly with depth at station 1, irrespective of tidal
stage.
The expected pattern of salinity variation with time at stations 2 through 4
(Figures 11 through 13) would be for salinity to increase with the rising tide at
all depths, reaching a maximum at high tide and falling with the ebbing tide.
While this general tendency did seem to occur at some depths and stations, there
were many aberrant points in the data suggesting the presence of eddies or other
disturbances in stratification.
The normal stratification was disrupted in station
2 during the low tide period sampled in October when low salinities were recorded
at all depths. A more typical salinity gradient ex isted at that station both three
hours before and three hours after the aberrant condition.
This disruption may
have been associated with the passage of a ship just prior to the low tide sampling.
The same phenomenon occurred during the same sampling period at station 3
(Figure 12). Station 4 did not seem to be affected in the same way (Figure 13).
The normal routine of sampling was in increasing order by station and it is
possible that sufficient time had elapsed between passage of a ship and the collection of the samples at station 4 to allow redistribution of the salinity gradient.
12
Another similar period of isohaline samples was found at station 4 on the first
set of high tide samples, 21 April 1972. Records of passing ships were not kept
as there seemed no poi.nt in doing so until the unusual salinity patterns emerg·ed .
The isohaline pattern was not recognized as being associated with shipping until
the October diurnal sampling data when an observation of the data in the field
showed the aberrant pattern.
VerjfjC;ation of this point should be relatively simple
and will be pursued in the future.
The current patt rns :md possibility of turbulent
mixing caused by passing ships are not completely understood in the Savannah
River. Cooled water, such as that proposed for dumping in the
r~ver
upon comple-
tion of the South ern Natural Gas Company liquid natural gas facility, will probably seek the level in the river where the same density exists.
Mixing will occur
when ships create turbulence and possibly at points of instability in the salinity
stratification as were implied in some of our diurnal data.
pH Determinations (diurnal)
Diurnal pH values at station 1 showed patterns varying from acid to slightly
alkaline independent of tidal stage during each of the three dates during which
diurnal samples were taken (Figure 14). On 21 April acid values coincided with
samples taken during the daytime, while alkaline determinations were obtained
from night
samples.
samples, however.
This pattern did not hold up for the July and October
We have no data to show the quantity of acid wastes being
added to the river on the dates ill question or the schedule by which acids were.
being released from one or more industrial facilities on the river.
Diurnal patterns in pH for station 2 were similar to those previously
13
described for station 1, except that at station 2 one period of predominantly
alkaline conditions prevailed in the daytime (first period of rising tide, Figure
15) . Once again it was not possible to coordinate pH values in the river with any
specific industrial activities during the period in question.
Values for pH were consistently higher at stations 3 and 4 (Figure 16 and
17) than at stations 1 and 2 (Figure 14 and 15) throughout the diurnal studies.
Station 3 and 4 as previously mentioned lie below all present point sources of
industrial and municipal effluents except for those which may exist in the
immediate vicinity of the Savannah River entrance. Some improvement in water
quality was evident downstream from station 2, although normal pH levels for
estuarine waters were only occasionally reached.
Monthly pH sampling demonstrated a general tendency toward increasing
pH with depth during most months.
The more intensive diurnal studies did not
indicate that this pattern was constant over the tidal cycle. As salinity increases,
the buffer capacity of the water also increases due to the presence of higher
levels of carbonate and bicarbonate present in the higher salinity water . Since
the buffering capacity of the water is disrupted to as great an extent with depth
as at the surface, the acid is apparently mixing rather thoroughly ' through the
water column.
Dissolved Oxygen (diurnal)
Diurnal dissolved oxygen values obtained from the diurnal sampling studies
are presented for station 1 through 4 in Figures 1 through 21, respectively.
Values of dissolved oxygen at the bottom of the water column at station 1 were
14
generally above 5. 0 mg/ 1 during each of the three dates during which diurnal
sampling was undertaken. Only in October di d values consistently above 5. 0
mg/1 appear in the upper water levels. No extremely low values were obtained,
although a few determinations only slightly in excess of 3. 0 mg/ 1 were obtained
{Figure 18).
The diurnal variability in dissolved oxygen at station 2 showed some patterns
which may have been related both with tide stage and time of day. Oxygen
production by photosynthetic plants ceases during the darlmess, thus the greatest
respiration demand occurs at night when the supply of dissolved oxygen is not
being replenished.
The first low tide samples of 21 April 1972 were taken in
!he morning about 0800 and had strikingly low levels of dissolved oxygen
(Figure 19). At low tide,water from upstream carrying waste effluents is not
balanced by relatively unpolluted water from downstream.
The two factors may
have been the reason for the low oxygen levels seen at that time. On the next
low tide stage of 21 April 1972 the oxygen was reduced from the previous falling
tide samples but not to the extent of the early morning low tide levels. This
pattern did not seem to hold up during the July and October diurnal sampling
periods. During July the lowest levels of dissolved oxygen seemed to occur on
high tide during the afternoon.
(Each series of samples was initiated when low
tide was occurring at about 0800.)
Fluctuations during the other two diurnal
sampling dates seemed to occur independent of daylight. On 23 October 1972
the highest levels of dissolved oxygen occurred during high tide as would be
expected if the pollutional load was at its lowest level during the high tide period.
The deviations from classical theory governing diurnal patterns in oxygen are
15
obviously complicated beyond the factors outlined above.
In general, dissolved oxygen levels at stations 3 and 4 were consistently
higher than those at stations 1 and 2. The idea that the pollution load seems to
be reduced by the time the water reaches station 3 is supported by the fact that
the lowest levels of dissolved oxygen occurred during low tide on all three
sampling dates (Figure 20), consistent with the idea that incoming higher salinity
water was carrying more oxygen than that carried by the more highly polluted
water coming from upstream.
The higher levels of dissolved oxygen at stations 3 and 4
wer~
generally
consistent with the previously discussed better water quality at these stations
when compared with stations 1 and 2. The lowest values of dissolved oxygen
observed at station 4 also occurred during low tide; however, there appeared
to be little effect related to time of day (Figure 21). The exception occurred
when an aberrant 1. 4 mg/1 value was obtained at eight meters depth on falling
tide during the April diurnal sampling period. Since the values above and below
eight meters at that tide were in excess of 5. 0 mg/1, it appears likely that the
aberrant sample was due to an error in technique.
While there were definite trends toward increased values of dissolved
oxygen at high tide at stations 3 and 4, the diurnal changes in dissolved oxygen
within any station were not particularly dramatic.
When low· levels were
obtained, as during the spring and summer, they tended to remain low throughout the day. A. 2. 0 mg/1 diurnal change or less in dissolved oxygen was generally
the case at most stations. This implies the lack of large algal blooms which
might be expected to cause a large jump in oxygen level over a 24 hour period.
16
High turbidity and flowing water such as found in the Savannah River contribute
to the low primary productivity, actual values for which are not presently
available .
In summary of the chemical data, the values for temperature, salinity, pH
and dissolved oxygen collected to date, give background information as to the
water quality conditions to be expected over the period of a year in the vicinity
of Elba Island.
The diurnal studies indicate that samples t aken during any tide
and during any part of the day give values similar to those which might be expected during any other tide or part of the day . The exceptions aJ?pear to be that
dissolved oxygen is slightly reduced during low tide periods at sam stations .
Indicators of pollution , such as pH and dissolved oxygen indicate that stations 1
and 2 are most severely affected, with generally improved water quality downstream of those stations . A strong salt wedge is established in the Savannah
River throughout the year; however, there is no apparent temperature gradient.
Water quality conditions were not found to be as detrimental to the survival
of marine organisms as might have been expected considering the amount of
waste received by the Savannah River . pH levels were low for normal estuarine
waters , but not to the extent where they would be lethal (usually below 5. 0 for
shrimp and many fishes). Dissolved oxygen, was low and often less than the
gener ally recognized safe level 5. 0 mg/ 1. During certain periods some
organisms certainly must have been stressed to one degree or another.
Cool water, such as that proposed to be added to the river at the site of the
Southern Natural Gas plant upon its completion has the potential for carrying
more dissolved oxygen than that of the surrounding warmer water. While the
17
winter and late fall dissolved oxygen levels are adequate, problems with oxygen
could occur during the spring and summer in the Savannah River. If the water
returned to the river after passage through the regassification plant is allowed
to gain oxygen by turbulent exposure to the atmosphere, the oxygen conditions in
the river may actually be improved . There . hould be no effect of addition of
this cooled water on either salinity or pH .
Faunistic Studies
Lists of the species of vertebrate and invertebrate organisms captured
during the 12 month trawl survey in the Savannah River arc presented in Tables
2 and 3, respectively.
Twenty-five species of fish and eight species of inverte-
brates were captured.
Of these, 12 species of fish and five species of inverte-
brates were of either commerciaL or sport interest.
The fish population was dominated, both in number of species, and biomass,
by fi s hes of the family sciaenidae.
This family (the drum and croaker family)
predominates all along the Georgia coast and is a dominant family to the north
and south of the state of Georgia and into theGulf of Mexico.
Many of the fishes and invertebrates captured are normal residents of
Georgia estuarine waters. One, the white catfish, Ictalurus catus, is a freshwater species and cannot live in salinities above about 15 ppt (Kendall and
Schwartz 1968) . Freshwater fishes were a rarity, however, and the biota of the
Savannah River was populated by several species which generally occur in high
sal inity water.
For example: Larimus fasciatus, Trichiurus lepturus, Spheoroides
maculatus and Xiphopeneus kroyer i were not captured in the estuarine waters
18
adjacent to the Savannah River (Wilmington River), but have only been taken in
the sounds and coastal waters of Georgia by workers at our laboratory.
The
presence of these organisms, and others, several miles upstream may be
attributed to the presence of the strong salt wedge in the Savannah River . The
depth of the channel, which creates conditions making the formation of the
salinity gradient possible, has effectively displaced the mouth of river several
miles upstream, at least insofar as bottom water is concerned. Since trawling
provides for the capture of predominantly benthic organisms, those species
which were restricted to the high salinity bottom water were captured.
Pelagic
animals are selected against by the otter trawl.
The total monthly biomass of organisms captured at each of the four stations
i.s presented diagramatically in Figure 22 and the actual figures for each month
are presented in Table 4 with means and standard deviations.
The dramatic
difference in total biomass captured between the summer (June, July and August)
and the remaining nine months of the year is apparent in Figure 22, even though
the vertical axis is a logarithmic function. A second depression in the general
level of biomass occurred during February.
These two periods of low biomass
coincided with the coldest and warmest water temperatures of the year. In order
to determine which if any, means were significantly different from the others ,
paired t tests were run comparing the means of the annual biomass between
stations and comparing the means of the biomass collected at all stations between
months . The results are presented in Table 5 and Figure 23.
When the mean
values of annual biomass between stations were compared (Table 5) we found no
statistically significant differences even at the 0. 10 level.
Thus, even though the
19
water quality conditions appear
to
be poorer at stations 1 and 2 than at stations
3 and 4, this is not reflected in the annual biomass figures insofar as organisms
collected by trawling is concerned.
The animals collected in the trawl in the
Savannah River are in general, euryhallne and eurythermal forms well adapted
to 1ife in the Georgia estuaries , or forms found in the sounds or nearshore
coastal waters.
These animals are r e;.P!lly adaptable to harsh environmental
conditions, so it is not surprising that they appeared able to adapt to conditions
at the upstream stations which may have been somewhat less than optimum
during portions of the year .
Figure 23 presents the t test results when the average biomass of samples
collected at each of the four stations within each month were calculated and
compared . Significant differences are noted below the values for t derived from
standard statistical tables . Meaningful significant levels in the table should be
considered as those at the 0. 05 and 0. 01 levels.
levels of significance are suspect.
For biological work, lower
The mean biomass collected in February,
which looked somewhat reduced from that obtained during all other months except June through August, was in fact, significantly lower than the mean biomass
collected during all but the three summer months mentioned.
The values ob-
tained in June, July and August were not significantly different from each other,
nor as stated above were they significantly different from the February mean
biomass , but did differ at varying levels of significance from values obtained in
most other months . The major exception was that the mean of tbe biomass from
the four January samples was not significantly different from that of the other
11 months.
This was largely due to the fact that the standard deviation for the
20
January samples was high.
Examination of Tabl e 4 will demonstrate that th
standard deviation for January was higher than the mean, whereas during all
other months the standard deviation was somewhat less than the mean value .
Thus, we found two significant pulses in the animal population. One depress ion in biomass occurred during February, and was probably associated with
low temperature; the other occurred during th e summe r. Routine sampling in
other estuarine areas along the Georgia coast has demonst rated that a winter
depression in standing crop biomass, associated most dramatically with low
temperature water, but beginning usually in the late fall or early .winter and
ending in March, is common throughout the area. On the other hand, high levels
of biomass are generally common during the summer months, peaking in September when the shrimp population is moving through the estuaries . Therefore,
the summer depression in biomass found in the Savannah River is sam what
unusual.
Examination of the species composition may give insight into some of the
reasons for the peaks observed in biomass. A comparison of the percentage
biomass contributed by vertebrates, monthly at each station is presented in
Table 6. With very few exceptions, vertebrates dominated the biomass during
each month at all stations. Only in September was the biomass of vertebrates
at each of the four stations less than . 50 ~ of the total.
In January through May
vertebrates accounted for more than 70% of the biomass at each station. Beginning in June, while vertebrates were still generally dominant, there were
one or more stations each month in which the percentage of vertebrate biomass
fell below 70%.
21
Biomass contributed by vertebrates as opposed to invertebrates indicates
that the pulses in biomass seen in Figure 22 and Table 4 may be largely
accounted for by vertebrates . Invertebrates often dominate the biomass of
trawl catches in Georgia, especially seasonally when blue crabs (Callinectes
sapidus) and white shrimp (Penaeus setiferus) become abundant.
Crabs did not
contribute significantly to the trawl catches in the Savannah River during most
months, and never were a dominant organism . Shrimp, while often present, and
sometimes present in significant numbers were only dominant during a short
period.
The percentages of total numbers contributed monthly at each station by
invertebrates are presented in Table 7. In a general way Table 7 mirrors the
data of Table 8 in that vertebrates dominated the quantity of individuals during
the first half of the year.
Once again, in September, there was a series of
samples which showed a relatively lower percentage of vertebrates than did the
previous samples, but the trend was reversed again in October.
The November
and December samples were definately dominated by invertebrates. During the
last two months of the year numerous white shrimp (Penaeus setiferus) and sea
bob shrimp (Xiphopeneus kroye r l) were captured, while
relatively fewer fish
were collected than in prior months.
Examination of the raw data pointed up the fact that the population of fishes
was dominated by members of the family Sciaenidae, especially the croaker
(Micropogon undulatus) and the star drum (Stellifer lanceolatus), while the invertebrates, when present in numbers, were dominated by Peneus setiferus.
This can be seen in Table 8 which presents the total number of individual
Micropogon undulatus, Stellifer lanceolatus and Penaeus setiferus captured at.
22
each station monthly during 1972.
The population of Micropogon undulatus reached a high level during March,
April and May, and was thereafter a rather insignificant part of the total catch .
The average weight of Micropogon undulatus during each month is presented in
Figure 24.
The few specimens captured during January and February were small
(less than 10 g average).
This small average weight continued when larger
numbers of individuals came into the population during the March through May
period. Beginning in August the average size of the few individuals caught increased monthly . This tends to indicate that the Savannah River was used as
a nursery ground, and possibly a spawning ground for Micropogon undulatus and
that after the spawing season the young fish left the river.
The pattern for Stellifer lanceolatus followed a trend similar to that of
Micropogon undulatus for the first few months of 1972, except that a large number
of individuals were present in January (Table ) , the average size of which was
generally less than 5. 0 g (Figure 25). Large numbers of Stellifer lancolatus
were captured during the March through May period, although the average weight
of these was somewhat higher than that of Micropogon undulatus for the same
period . Relatively few Stellifer lanceolatus were present in the samples during
the summer months, but large numbers began appearing in the fall, this time
as smaller average weight individuals than those of the spring peak.
The
average weight increased from August through December, with animals of an
older age class presumably moving in during November and December .
The pattern for Stellifer lanceolatus seems to indicate that they wer e
23
eliminated by the cold water during February (this may also apply to Micropogon
undulatus), but were numerous after the water temperature warmed.
The spring
population may have been spawned the previou s fall and moved into the river with
the warming water.
This animal is usu al '' f.-)tmd in the sounds, inhabiting water
of salinities greater than 20 ppt.
Th e Savannah River
regime for the species and apparently
acter~
h ',(~
the proper salinity
as a nursery area during the spring.
The population apparently was eliminated during the summer, again , probably
due to temperature. It is likely that they moved offshore until the water began
cooling in September.
The fall population was dominated by very small individuals
which were probably spawned during 1972. As the water temperature began to
cool this second peak was replaced by larger fish.
The difference in average
size between October and November indicates that at least two age classes were
present whereas few large individuals were present during the months of September and October.
Penaeus setiferus made up an insignificant portion of the total number of
organisms collected during most of the sampling period. Several individuals
were captured during the spring, but the largest numbers were present beginning
in September and running through December.
Once again, the lowest numbers
were recorded during the coldest and warm st months , February, June, July
and August.
The average weights of Penaeus setiferus collected at each station
and month are present in Figure 26. The pattern is, in this case, rather random
with no specific trends other than the fact that the few shrimp captured during
the summer were juveniles.
White shrimp spawn generally during May, but
shrimp of all sizes are present in Georgia estuaries throughout the year in at
24
least small numbers.
Temperature seems to have been the limiting factor
on the shrimp population as it was on the fishes discussed above.
During February, no particular species dominated the catch. All stations
had very few organisms and usually had two or more species, except station 3
where no animals were captured during a 10 minute tow.
observed during the summer period, June througl'
~rul
The same trend was
. The population was
generally made up of the same organisms whicl, occurred prior to and after the
summer, but the numbers and biomass were severely r .J uced during the period
of warm temperature.
An additional trawl was made during Oc ober downstream from station 4
(Figure 1, station 5). The total weight of organisms in that sample was 3169. 9g
with
84 individuals collected in 13 species.
The biomass was similar to that
at the upstream stations, and was dominated by Stellifer lanceolatus, which
followed the pattern exhibited upstream. No new species were found, nor was
the population structure different in any significant way from that of the upstream
stations .
Diversity was calculated using the Shannon-Weiner function, which has been
used in Georgia by Dahlberg and Odum (1970) and is derived from information
theory . This index appears to be one of the best for characterizing estuarine
fish populations. Diversity indicates the relative "health" of the animal community, with increasing diversity being desirable.
The results of the application
of the selected diversity index to the population of animals in the Savannah River
are presented in Table 9. In general, diversity was somewhat lower in most
cases than is found in most Georgia estuarine situations. Values of less than
25
1. 0000 are relatively uncommon in other areas except during the coldest winter
months. However, in the Savannah River values of less than 1. 0000 were the rule .
The diversity index followed no particular pattern seasonally; all values being
almost uniformly low regardless of whether they carne from samples when
biomass and numbers of organisms were high or low.
During the winter months
there was a trend toward higher diversity in a downstr eam direction; however,
diversity was not higher at stations 3 and 4 during the summer months as
would be expected if poor water quality wer e limiting the upstream fauna.
From
the diversity information presented, we would have to conclude that the Savannah
River offers a unique situation in which large quantities of a few species can
thrive. At no time does a highly diversified community become established .
The species composition of each station is presented in Tables 10 through
13 .
In summary of the biological data, it is apparent that both biomass peaks
exhibited in the data are due to fish pulses, the first (March through May) being
due to the presence of large numbers of yow1g Micropogon undulatus and
Stellifer lanceolatus.
The second pulse (September through January) is caused by
an apparent new hatch of Stellifer lanceolatus and is augmented by Penaeus
setiferus . Many other organisms are present, but the three discussed seem to
dominate the population, insofar as those animals available to the trawl are
concerned.
There are two periods during the year when the animal population is severely
restricted; during the coldest part of the winter (February, in 1972) and during
the summer (June through August) . The reasons appear to be related to temperature
26
and not to any pollution impingement.
The water quality except for temperature
may be sufficient for the survival of all of the species which are present during
other times of the year in abundance. The addition of cool water from the
Southern Natural Gas plant may offset some of the low biomass by decreasing
ambient temperature.
The effects of the effluent during the winter may be to
increase the onset of evacuation of the fishes from the river when the temperature
approaches 10 C and delay their return when the water begins to warm.
The Savannah River, apparently due wholly or in part to the fact that it has
b en channelized in excess of 15 meters depth, appears to
displa~e
ground for young Sciaenid fishes during large portions of the year.
the nursery
The numbers
of small Micropogon undulatus and Stellifer lanceolatus which we captured in the
river (often at a point over 10 miles upstream from the entrance) were not observed by us in any adjacent estuarine area, even if the salinity regime was
similar .
In conclusion, the Savannah River is not a biological wasteland, as some
would have us believe, but houses large quantities of Sciaenid and other fishes.
Current studies aimed at investigating the feeding habits of these fishes as well
as the quantity of benthic organisms present and their diversity are underway .
Plans are also being formulated to examine the zooplankton and phytoplankton
populations of the Savannah River to obtain information on the productivity present.
27
Literature Cited
American Fisheries Society. 1970. A list of common and scientific names of
fishes from the United States and Canada. AFS, Special Pub . No. 6. 150 p .
American Public Health Association. 1965. Standard Methods for the Examination
of Water and Wastewater. APHA, New York. 769 p.
Dahlberg, M.D. and E . P. Odum. 1970. Annual cycles of species occurrence,
abundance and diversity in Georgia estuarine fish populations. The Amer.
Midl. Natur. 83:382-392 .
Georgia Water Quality Control Board. 1972. Water Quality Data Lower
Savannah River 1970-1971. River. G. W. Q. C. B., Atlanta, Ga. 54 p mimeo.
Kendall, A. W., Jr. and F.J. Schwartz. 1968. Lethal temperature and salinity
tolerances of the white catfish, Ictalurus catus, from the Patuxent River,
Maryland. Ches. Sci. 9:103-10 .
N
t
ATLANTIC
SAVANNAH.
GEORGIA
OCEAN
N
CX>
Figure 1.
Location map for sampling stations occupied during the course of the
study.
STATION 2
STATION I
29
JO
M£tlN
JO
MEAN
SURFACE
JO
SURFJJCE
10
JO
u
20
10
2 METERS
10
JO
10
BO TTO M
20
20
10
10
JFIIIAMJJASONO
JFMA
MJ
1972
JASONO
1972
STATION 4
STATION 3
JO
MEAN
u
10
8 MfTERS
JO
JO
BO T TOM
20
20
10
10
JF
MAMJJA
1972
Figure 2.
SONO
BOTTOM
JF
MAM
JJASO
N
O
1972
Monthly temperature determinations at stations 1 through 4 including
values obtained from surface, midwater and bottom, and the mean
value of the three . (Standard deviation of the mean is indicated where
it exceeded !_0 . 500) .
STATION 3
STATION 2
STATION
4
STATION
s
t
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1972
Figure 3.
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1972
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1972
Monthly salinity determinations at two meter inter vals, surface to
bottom, from stations 1 through 4 . (All values in parts per thousand.)
J
1972
STATION 2
STAT/ON
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1972
Monthly pH determinations at two meter intervals, surface to bottom,
from stations 1 through 4.
A
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1972
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1972
Monthly dissolved oxygen determinations a~ two meter intervals ,
surface to bottom, from stations 1 through 4. (All val ues in mg/ 1.)
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23 OCTOBER 1972
19 Jlil y 1972
28 I
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Figure 6.
STAGE
Diurnal temperature determinations from station 1 at two meter
intervals, surface to bottom, on three dates during 1972. (All
values in Celsius. )
w
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19 JULY 1972
21 APRIL 1972
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23 OCTOBER 1972
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Figure 7.
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Diurnal temperature determinations from station 2 at two meter
intervals, surface to bottom, on three dates in 1972. (All values
in Celsius.)
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21 APRIL 1972
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Figure 8.
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23 OCTOBER 1972
19 JULY 1972
Diurnal temperature determinations from station 3 at two meter
intervals, surface to bottom, on three dates during 1972. (All
values in Celsius.)
....
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21 APRIL 1972
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Figure 9.
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Diurnal temperature determinations from station 4 at two meter
intervals, surface to bottom, on three dates during 1972. (All
values in Celsius.)
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STAGE
Figure 10. Diurnal salinity determinations from station 1 at two meter intervals,
surface to bottom on three dates during 1972. (All values in parts
per thousand .)
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23 OCTOBER 1972
19 JULY 1972
21 APRIL 1972
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TIDE STAGE
Figure 11. Diurnal salinity determinations from station 2 at two meter intervals,
surface to bottom, on three dates during 1972 . (All values in parts
per thousand.)
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STAGE
Figure 12. Diurnal salinity determinati<?ns from station 3 at two meter intervals,
surface to bottom, on three dates during 1972. (All values in parts
per tho us and. )
w
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21 APRIL 1972
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TIDE STAGE
Figure 13. Diurnal salinity determinations from station 4 at two meter intervals,
surface to bottom, on three dates during 1972. (All values in parts
per thousand.)
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23 OCTOBER 1972
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STAGE
Figure 14. Diurnal pH determinations from station 1 at two meter intervals,
surface to bottom, on three dates during 1972 .
21 APRI L 1972
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TIDE STAGE
Figure 15. Diurnal pH determinations from station 2 at two meter intervals,
surface to bottom, on three dates during 1972 .
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Figure 16.
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23 OCTOBER 19 72
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STAGE
Diurnal pH determinations from station 3 at two meter intervals,
surface to bottom, on three dates during 1972.
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19 JULY 1972
2 1 APRIL 1972
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TIDE STAGE
Figure 17. Diurnal pH determinations from station 4 at two meter intervals,
surface to bottom, on three dates during 1972.
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23 OCTOBER 1972
19 JULY 1972
21 APRIL 1972
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TIDE STAGE
Figure 18. Diurnal dissolved oxygen determinations from station 1 at two m eter
intervals, surface to bottom, on three dates during 1972. (All values
in mg/1.)
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21 APRIL 1972
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JULY 1972
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STAGE
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Figure 19.
Diurnal dissolved oxygen determinations from station 2 at two meter
intervals, surface to bottom, on three dates during 1972. (All values
in mg/1.)
21 APRIL 197 2
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19 JULY 197 2
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STAGE
Figure 20. Diurnal dissolved oxygen determinations from station 3 at two meter
intervals, surface to bottom, on three dates during 1972. (All values
in mg/ 1. )'
21 APRIL 1972
..
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6
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23 OCTOBER 1972
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H
TJ
7.1
T. l
Tl
0 .1
...
f. I
...
...
"
16
Ill
,...
•
0
'!!
i!!
i!i
*
!!
~
,...
i
r
0
•
"';;;
!
I :,...,...
i
,...
•
0
'!!
!!!
i!i
I
~
g
,...
0
. "'
i
"'
;;;
~
:<
a:<
TIDE STAGE
Figure 21. Diurnal dissolved oxygen determinations from station 4 at two meter
intervals, surface to bottom, on three dates during 1972. (All values
in mg/1.)
49
Numbwt
ov• bare COttltpot'ld
3
with ttotl"" duovn otlono
10000
!1000
--
JAN
FEB
MAR
APR
MAY
DATE
Figur e 22 .
JUN
JUL
AUG
SEP
OCT
NOV
( 1972)
Total monthly biomass collected at each station during 1972 .
DEC
50
FEB
242 .8
Level of
1.120
a i gni f i cone e
below
MAR
105 4.4
APR
for t
0 .669 2 . 547
0 .05
0 .097 2 .277
0.05
2181.5
value
indicated
0.184
MAY
6283.5 1.14 7 2 .470 2 .092 2 .038
0 .05 0 .05 0 .05
143.6
1.139 0 .3 4'1 2.652 2.363 2 .486
0 .05 0.05 0 .05
JUL
1.169 1.119
JUN
86.2
AUG
143.0
SEP
2.883 2 .533 2 .510 0 .641
0.05 0 .05 0 .05
1.140 "0.474 2 .722 2.402 2.487 0 .011
0 .05 0 .05 0 .0 5
1.365
683.5
0 .852 2.470 0 .906 0.970 2 . 251 2 .633 3.084 2.830
0 .05 0 .05 0.05 0.05
0.05
OCT
0.080 2 .111
2571.0
NOV
22J0.3
1.288
1. 17 7 1.323
0.05
0 .079 2876 1.499
0 .05 0.10
2J44 2 .200 2.149 1.629
0 .05 0 .05 0.05 0.10
1.305 1.558 2 .929 3.025 2 .946 2 .076 0 .260
0 .10 0 .05 0 .05 0 .05 0 .05
DEC
0 .635 20.143 7 .052 5 .580 1.066 20.136 22.467 22.582 11.787 p.943
3645. 5
0.01 0 .01
0.01 0 .01
0.01
0.01 001
JAN
FEB
MAR
APR
MAY
JUN
2390.4 242.8 10544 2181.5 62835 143.6
Figure 23 .
OCT
1.966
0 .05
JUL
AUG
SEP
NOV
86.2
143.0
683.5 25710 2210.3
Comparison of mean monthly b iomass colle cted during 1972 by paired
t test.
51
• - Sta.
• - Sta . 2
6 - Sta . 3
o - Sta. 4
M icropogon undulatus
0
35
I
30
-0
•
25
0
1~
(!)
Lu
•
20
~
z
<t
15
I
w
•
•
~
10
0
0
•
0
•
J
F
••
I
0
5
•I
••
M
A
•
M
J
J
A
s
0
N
D
MONTH ( 1972)
Figure 24 . Average weight of Micropogon undulatua captured at each sta tion
monthly by otter trawling dur ing 1972.
52
Stell ffer lanceolatus
• - Sta. I
•
• - Sta. 2.
• - Sta. 3
o - Sta . 4
20
•
-.....
0
15
0
:I:
•
(!)
w
~
z
<(
w
10
~
•
5
•
0
8
•
•
•i
•
•
•
•
0
•
J
F
M
•
i
•
A
M
J
0
•
J
A
I
0
0
s
0
•
•
N
D
MONTH ( 1972)
Figure 25. Average weight of Stellifer lanceolatus captured at each station
monthly by otter trawling during 1972 .
53
Penaeus setiferus
• - Sta.
• - Sta . 2
• - Sta. 3
0 - Sta. 4
15
0
0
•
-
0'
......,
..,_
:r:
0
10
•
•
(.!)
i.&.J
@
3:
0
z
0
•
<t
•
•
0
w
~
5
•
••
•
• •
0
• •
•
•
i
•
J
F
M
AM
J
J
AS
0
N
D
MONTH ( 1972)
Figure 26. Average weight of Penaeus setiferus captured at each station monthly
by otter trawling during 1972.
54
TABLE 1
Tide stage in the Savannah River during monthly sampling
Month
Tide Stage
(1972)
January
Low to slightly rising
February
Falling
March
Falling
April
Falling
May
Falling
June
Low
July
Low
August
Low
September
Rising
October
High
November
High
December
Falling
55
TABLE 2
Scientific and common names of vertebrates captured in the
Savannah River during 1972 by otter trawling
Family
Scientific Name1
Common Name
Clupeida
Brevoortia tyrannus 2
Opisthonema oglinum
Atlantic menhaden
Thread herring
Engraulidae
Anchoa hepsetus
Anchoa mitchelli
Bay anchovy
Striped anchovy
Ictaluridae
Ictalurus catus2
White catfish
Ariidae
Arius felis
--Bagre marinus.a
Sea catfish
Gaftopsail catfish
Batrachoididae
Opsanus tau
Oyster toadfish
Pomatomidae
Pomatomus saltatrix2
Bluefish
Carangidae
Chloroscombrus chrysurus
Vomer setapinnis
Atlantic bumper
Atlantic moonfish
Sciaenidae
Bairdiella chrysura2
Cynoscion regalisa
Larimus fascia1us2
Leiostomus xanthurus3
Micropogon undulatus 2
Stellifer lanceolatus 3
Silver perch
Weakfish
Banded croaker
Spot
Atlantic croaker
Star drum
Mugilidae
Mugil cephaluaa
Striped mullet
Trichiuridae
Trichiurus lepturus
Atlantic cutlassfish
Stromateidae
Peprilus alepidotus
Harvestfish
Bothidae
Etropus crossotus
Paralichthys lethostigma2
Fringed flounder
Southern flounder
56
TABLE 2
(continued)
Scientific and common names of vertebrates captured in the
Savannah River during 1972 by otter trawling
FamUy
Scientific Namel
Common Name
Soleidae
Trinectes maculatus
Hogchoker
Cynogloss idae
Symphurus plagiusa
Blackcheek tonguefis h
Tetr aodontidae
Sphoeroides maculatus
Northern puffer
1
Fishes placed in phylogenetic order according to American Fisheries Society
(1970).
2
Commercially valuable or sought by sport fishermen.
57
TABLE 3
Scientific and common names of invertebrates captured in the
Savannah River during 1972 by otter trawling
Family
Scientific Name
Common Name
Penaeidae
Penaeus az tecus1
Penaeus duorarum1
Penaeus setiferusl
Xiphopeneus kroyeri1
Brown shrimp
Pink shrimp
White shrimp
Seabob
Portunidae
Callinectes sapidus1
Portunus gibbesii
Blue crab
Crab
Squillidae
Squill a empus a
Mantid shrimp
Loliginidae
I..oligu.ncula brevis
Squid
1
Commercially valuable species
TABLE 4
Total monthly biomass (g) of organisms collected at each atatlon wlth mean, standard deviation
Month
1
Station Number
2
3
Monthly
Total
Monthly
4
Mean
Monthly
Standard Devlattpn
January
380.0
. 897.5
7.4
8276.6
9561.5
2390.4
3941.1
February
337.3
113.9
0.0
277.1
728.3
182.1
153.8
March
1109.2
264.1
954.0
1890.1
4217.4
1054.4
667.3
April
1064.1
735.7
2354.9
4571.1
4611.8
1153.0
838.8
May
1252.2
6130.2
11468.2
U>at Net
18850.6
6283.5
5109.7
June
384.8
90.9
62.6
36.1
574.4
143.6
162.3
July
156.7
17.8
147.0
23.1
344.6
86.2
76.0
88.8
146.4
175. 6
167 . 1
577.9
tn.5
39.1
249.3
572.9
1182.1
809.7
2814.0
703.5
393.1
68.0
1258.5
4352.4
4604.9
10283.8
2571.0
2258.2
November
2247.4
4187.7
1513.7
950.9
8899.7
2224.9
1412.1
December
4090. 9
3523.3
3388.2
3579.6
14582.0
3645. 5
307. 6
11428.7
17938.9
25605.6
21072.3
952.4
1494.9
2133.8
1915.7
1180.8
2001.9
3268.4
2600.0
August
September
October
Total for station
Monthly mean
Standard deviation
V>
00
59
TABLE 5
Comparison of average monthly biomass of organisms
collected at each trawl station during 1972.
The comparisons were made utilizing the paired t test
Comparison Between
Stations
1
degrees
of
freedom
Mean Annual
Biomass
1
2
1030.8
1325.3
0.81
22
1
3
1030.8
2320.6
1.18
22
1
4
1030.8
2289.1
1.16
21
2
3
1325.3
2320.6
0.58
22
2
4
1325.3
2289.1
0.44
21
3
4
2320.6
2289.1
0.18
21
None of the values obtained is significant at the 0.10 level or below.
60
TABLE 6
Percentage of total biomass contributed monthly at each station
by vertebrates collected by otter trawling during 1972.
Station Number
Month
3
4
1
2
January
100.0
94.0
100.0
86.8
February
100.0
71.3
No specimens
94.8
March
100.0
100.0
99.2
97.6
April
70.7
100.0
81.7
76.0
May
97.6
96.0
98.8
Lost net
June
63.9
100.0
100.0
100.0
July
33.0
83.1
96.2
100.0
August
82.1
73.8
63.6
81.4
5. 7
45.3
22.5
48.5
October
51.6
79.6
68.4
80 .0
November
17.3
52.4
38.1
63.1
December
87.4
58.1
65.5
72.7
September
61
TABLE 7
Percentage of total number of organisms contributed monthly at
each station by vertebrates collected by otter trawling during 1972.
Station Number
3
4
1
2
January
100.0
98.6
February
100.0
70.6
March
100.0
93.5
99.3
97.7
April
80 .3
100.0
96.4
95.9
May
97.7
98.5
99.2
Lost net
June
96.1
100.0
100.0
100.0
July
90.0
85.7
95.6
100.0
August
57.1
75.0
87.5
66.7
5.9
48.6
21.4
86.4
October
61.1
81.6
86 .4
87 .3
November
34.3
9.4
22.2
47.1
December
26.8
25.7
22.9
35.5
Month
September
100.0
No Specimens
90.
90.4
62
TABLE 8
Total numbers of Micropogon undulatus, Stellifer Lanceolatus and
. Penaeus setiferus captured monthly by otter trawling during 1972.
Month
January
February
Micropogon
undulatus
4
...,
I
Stellifer
lanceolatus
Penaeus
setiferus
186
26
0
2
March
174
310
12
April
598
644
50
May
487
1443
7
June
0
0
1
July
10
52
1
August
3
59
15
September
8
160
269
October
9
2347
45
November
0
239
294
December
38
134
212
TABLE 9
Diversity of organisms captured at each station monthly during January through October, 1972,
according to the diversity index H ==-lpi ln pi where pi = the proportion of the total
contributed by species i.
Station
JAN
FEB
1
0.6931
0.6931
2
0.2941
3
4
MAR
APR
MAY
JUNE
• 9743
1. 2331
1. 0168
0.5648
0.6057
1.1039
0.2186
0.6053
0.3767
0.6931
NS
• 9152
0.8492
0.3314
0.5690
1.0092
1. 5257
0.5509
NS
wst Net
1. 0985
NS -No specimens in sample
TABLE 9
(continued)
Diversity of organisms captured at each station monthly during January through October, 1972,
according to the diversity index H =- I pi ln pi where pi = the proportion of the total
contributed by species i.
Species
JULY
AUG
SEPT
OCT
NOV
DEC
1
0.9974
1.2773
0.3895
0.9579
.5990
1. 2815
2
0.7967
1. 4119
1. 5447
0. 6085
0.9631
1. 0180
3
1.0720
0.7154
0.9740
0.6633
1.0654
1. 2230
4
0.0000
1.2864
0.7816
0.6148
1.6224
1. 6966
TABLE
10
Spe.e lea compoeltloa or fl1be1 aDd m.orolaver&ebrate.• u lodlcaled by l.be rumber of1Ddl\'l4lal8 o1 eaob
apecl.e • c apo.. red moa.l hly a1 1\aUoa J by otur trawlhrc 4lrl• 19'72:
Claaatflcatlon
Ju
Feb
Mar
Ap<
~
Jun
Jul
""'
Bep
Oot
No•
~
\ ·F.nTEBR A TES
Clupeldao
~tyr....,....
Oplo thoDOma O(li .. m
t:ocr .. ud ..
~~
u
9
ArUdae
AriUII~
Sci auld..
~cbry1u.ra
59
15
eyDOOclo• re1allo
Ulo1&omu1~
lollc!'OPOI[!>a..-I&D>I
90
107
HO
SUIIlfe< 1-laa&o
14
~llld ..
~oepbolu
BolbtdMO
Parollc:blllye letboollp.a
Soleld•
J7
~·~
14
cy-Joa•ld•
~Pl!lluu
INVERTEBRATES
Peaaeld•
!!!!!!!!!~
!!!!!!!~
47
32
Z04
90
236
118
Xlp!oope_..~
PortYIDtdae
~··Tol&l aumber c.,ured a.cb moaU.
Total yeuly odeb,
7U
"'
:se
74
10
$1
I.
(7\
Ul
TABU:
Specl1111.
J. .
C l:~~~•lfieatioa
II
ol n.taea &ad m.ac:rola.¥ersebrate. u iadlc:at.d by tbe .au.mbl!r of ladMd.ull ol il!lach
IJIIIIC: lu c- ~wred moedll,y at uatloo 2 by ol1ll!r u-awllac cklrtor Jt12
eompo~ILlDD
Feb
Mar
Apr
IUy
.llLO
••
14
Jol
....
Sop
01"
"'"'
""'
VERTEBRATES
C\upeld.e
~qru..aa
£Gi_r.alld.M
~~
II
k:t.a .... rfd•
lc1.&lurua!!!!:!.!..
Ar ltdae
~.!!..!!!
~"'...,.
......
Pamalomkl-
~~
a.raAJ1dM
Vomer aet.9U••la
Scl.sa."'-r
~et.rz at.~.n
Cy111011etoq reedit
~~
~~
~~
11
"
...
....
Zl
IU
zz
302
••
.
•••
90
&ombrkt.c
&ombc~o ~
ID.culdi.a
StromaU!Id•
p..,,,.... &Jepl<lo>....
Salcld.~m-.r:ruUIIILI•
C'7B?CIOI •ld•
~~
~\· £RT.£9R AT £S
••
.
1M
311
...
.,,
Pr.aM~ Id.M
~
!!!!!!!!!!
XlpbopeDBU.I~
Pu ra.a.aldar:
Calll•ctat
••6du
Tol.al •nnber c tp•u•ed c.:b moat.b
Toa..l _yt!arly e atcb;
Q 41
...
17
u
an
...
••
••
•••
•u
g:
67
TAn f.>:
12
~c:!C"IIf'" comiX*Itlon of rt•ht!• nntt m :~rroln\'t• rwhr:llct~~ M lndlt- IU.t.-rl hv lht· numhcr
Il l IMh ldu.t.' nl
t• r~ch
apcrln C't\UIUn•d llr 1ttft\Jon 3 hY '•Iter trnw llna durlrut 1972
Jon
C'lu•Hit•allon
t'"l •b
M r
Apr
M ;"'
Jun
Jul
""•
.'!rp
I> I
No\
llt•i
n: Rn: RRAT~S
("lutJehtllt'
Br~\·onrlla
S"rannua
10
t:,.rrwl ld!ll
Ant" btm h 'L'!)!IIru.ll
~~·
Arl ldnc.o
~~
.!!.!~!.! martm.~1
Pomatomtdw
~laiLaU'IJt
CarM«ldae
~•elllplftAll
Sc:IMIIid&e
~ehryaura
13
ey..,.ciOD Mil o! ..
~a:uthuru.
Mentlclrrbu
~
~undulatwl
1< 5
~ IUftolAD.U
10<
71
83
1437
32
52
20
1101
38
16
Trlelllurkl•
Trlcbtun~o~
-
lepD.Iru
.....u..
~olepldoiiU
Boll>kloe
Porollcbtbya lethooUcmo
)
Boleld•
~~
cyqloe•hiae
36
~..e.!!&!!!!!..
INV&RTEBRAT£9
Pea.eldu
145
~~
Xlphot;M!Dir1.1.• kroyerl
II
23
3•
I~B
147
227
10"47
lll
lH
Porcu.nldiie
Ct~.lHneclr•
aytdua
Squ.illtd ..
~rmpu•a
t..oll.gl.nlclae
lnl!guncula
~
Tola.l ~mber- c:JPD.II'fli euh month
To._.t ;v•arl.' · c-:ucb :
3ttS9
160
197
15-10
~5
fi "'
19'!
68
TABU: II
Srpeol•a oom~ltlolo ol f\aa-1 ud miCirOlDYUt.br& ... M llld\ou.d bJ' \M •mber ll( '.tiY&dullli of._,ll
•pee'-• c-.p1UNd at •LAUoa -t by ouar Cl'._..ll • .dlllrf.alll 1112
...
C l••lflcatloa
rob
.....
Ajlr
. ...
Jqo
ohl.l
....
...,
Ool
,....
VUTE.BJIATEI
-
Clupeld•
~trr....
~ ..lid•
~~
~~
II
ArUd•
~!!.!!!
Balr.elml.d.ld•
g...,..!!!!
Poma-.m~
~·aJt.ltl'~
Cu-MPI•
Olot"OeOOIDbW.I
2!l!!!!!.
8ct•DJd•
.
BalrdNlla~
CyaoecJoencalt..
II
wt... r..c••••
~~
.
Meatlctrr.._ aaerlc..,
~udlllbllla
... w.~~
Trtclailtrtd.•
II
:102
•
110
413
II
Ill
lUI
II
IS
.....
~...,
-~~~~~
.... ld_
~ .....1.....
c,..,.a.,..ld..
~~
u
14
,,.
14
S4
'nltr .,dDatld•
atlllooarokt.a~
IIIVERTEBRAT!!I
PaiU81.c a.
.£!!!!!!~
~.!!!!!!!!!
X!p!!o!>o.u
.
It
14
~
to
.
H
14t
I!
Ill
1310
IT
Itt
Portu.aid.M
CaiU.DIIC ..a Ufidua
II
10
~·-··
!O!UIIIIdM
!!I!!!!! !.!!!e!!.!.
Total aumber uptured ..c\ moatb
TOLal
yeuty caicb :
3254
383
tl
344
!lOG
u
...