International Council for
the Exploration of the Sea
CROSS-SHELF
AND
DRIFT
C.M. 1993/L: 33
Theme Session 0
ZONATION.
OF
PORTUGAL
FISH
VERTICAL
LARVAE
DURING
WEAK
OFF
DISTRIBUTION.
NORTHERN
UPWELLING.
by
H.-eh. John
*
•
**
*
and P.
Re **
Taxonomische Arbeitsgruppe der Biologischen Anstalt Helgoland
c/o Zoologisches Institut und Museum
Martin-Luther-King-Platz 3, 20146 Hamburg, PR Germany
Departamento de Zoologia e Antropologia, Pac. de Ciencias
Universidade de Lisboa
Bloco C2 - Piso 3 - Campo Grande, 1700 Lisboa, Portugal
Abstract:
An area off Northern Portugal was surveyed in August 1989, norma1ly a month
of strong upwelling, in order to study the horizontal and vertical distribution of fish larvae in relation to the coastal upwelling structures.
Stable stratification and anomalously high temperatures caused the unusual
offshore spawning of anchovy, En.~ ~ ~ , during the survey.
Spawning intensity of anchovy was at maximum during periods of non-upwelling. The observed upwelling event was of short duration only and had low
intensity, particularly close to the coast.
The cross-shelf zonation and dispersal of fish larvae depended on the
interaction of spawning bathymetry, vertical distribution of larvae and the
hydrographical conditions in the respective range, but integrated time
scales larger than the survey.
Soleid larvae living in less dense and less wind exposed coastal surface
waters appeared to be retained there.
Surface living larvae of midshelf species showed dispersal offshore. For
young anchovy larvae dispersa1 up to about 10 miles from the spawning
grounds was directly related to the observed upwelling event, but for eIder
larvae up to 43 days old occurrences up to 37 mi1es from the respective
zonal spawning depths were related also to two events north of the surveyed
area during July.
Larvae from midshelf origin. but with a more extended vertical distribution
including the thermocline showed reduced net offshore dispersal, particularly when they avoided the Ekman-layer as e. g. eatUonyrTI.(A -6p. However,
the bottom-near specimens of many taxa showed some advection from midshelf
towards the coast.
The inshore boundaries of larvae of several slope or oceanic species were
not always as anticipated from their vertical range, the reasons are discussed.
It
is
presumed
that
under
normal
swmner
conditions
(with more
consistent
and stronger upwelling) all discussed dispersal patterns would become more
pronounced.
,.
Introduction:
An area off the central west coast of the Iberian Peninsula (Fig. 1) was
object of a seasonal study of horizontal and vertical distribution patterns
of fish 1arvae in relation to the coastal upwe1ling structures.
Coastal upwelling in seasona1 scales occurs normally off Northern Portugal
from late spring to late summer or early autumn (WOOSTER et al. 1976; PIUZA
et al. 1982). As in other eastern boundary current areas, coast-parallel,
equatorward windstress causes offshore Ekman-transport in the surface
layer. A resulting mass-deficit near the coast is partly compensated by an
intermediate onshore compensating current. This compensating current feeds
cooler, nutrient-rich water into the euphotic 1ayer (MINAS et a1. 1982),
enhancing primary and subsequent production (e.g. HEMPEL 1982). There exist
relations between upwel1ing intensity and biomass of commercia1 fish
stocks, the effects being positive or negative, depending generally on the
species (e.g. ARNTZ 1986; WYATT & PEREZ-GANDARAS 1988). However, as pointed
out by DICKSON et al. (1988), such relations may even reverse sign between
adjacent stocks of the same species, and the mechanisms are on1y partly
understood. Among the acting mechanisms are besides trophic enrichment
turbulent mixing (affecting prey-density) and cross-she1f dispersal of fish
larvae with both Ekman-transport and compensating current, potentially
removing larvae from optimum food concentrations or the habitat of adults
(e.g. BAKUN & PARRISH 1991, and literature therein). I t is assumed that
successful recruitment of pelagic stocks in upwelling ecosystems needs an
optimum environmental window (CURY & ROY 1989).
This paper describes both the hydrographic structure and the species composition of fish larvae off Northern Portugal during weak upwelling, and
analyses specific cross-shelf zonations and vertical distributions as a
pilot study to elucidate the space and time scales of cross-shelf dispersal
of fish larvae.
Material and methods:
A grid of 79 fixed standard CTD/p1ankton stations, organized in 6 crossshore sections, was carried out off northern Portugal from 08 to 15 August
1989, on board of the German RV "Priedrich Heincke" (cruise no. 279, see
Fig. 2). The typical station spacing was ~10 km over the shelf and upper
slope, increasing to 30 km offshore. The sections were named A to P, from
north to south, and the stations numbered, within each section, from coast
to the open ocean (1 to 12 - 14), regard1ess of the direction the observations were carried out (Fig. 2).
CTD-data come from a mini CTD (ME-OTS 1500) instal1ed near the opening of
an ob1iquely towed multiple-opening-closing plankton net (MCN). The system
was towed under contro11ed conditions (ships speed 1.2 m/s, speed of ascent
<10 m/min) from 200 m depth (or about 5 m above the bottom in shallower
stations) in an oblique path. The mounting was done in a way to achieve
unobstructed flow through both CTD-sensors and net. The dots in Fig. 2
refer to the starting positions of the stations. However, the end positions
of CTD (not oxygen) might have been as far as 2 nautical miles away.
In order to assess data quality, the T,S properties in the temperature
range 12° - 13°C were checked against the standards of EMERY & DEWAR
(1982), and no significant deviations were found. The salinity values are
2
•
therefore believed to be generally correct.
Disso1ved oxygen was measured with an independent. but similar, CTD-02
probe that had a slightly deficient conductivity senSOr. Due to a slow
02-sensor (time constant 60 s), measurements were taken at S8 standard
depths between 5 and 300 m, or 3 m above the bottom in sha1lower stations
(see dots in Fig. 7); The oxygen sensor was ca1ibrated twice dai1y by the
WINKLER-method
(GRASSHOFF. et alt
,
.1983).
, ,Oue
' to
,instrument failure ' the
oxygen measurements were dlscontlnued before the end of section C.
"
SEEWETTERk~ HAMBURG provided wind-time series for the period01 July -·15
August 1989 ("SWA"-data). The data came from stations off Vigo and in viana
do Castelo, Leixoes (Fig. 3) and elose .to Peniche· (the 1atter was 'least
affected by oreographic effects; but showed the highest number of interruptions and worst directional resolution).
Except for the deepest stratum 120 - 200 m, the up to five plankton sampies
per tow came from steps 30 m wide (or less, see e.g. Fig. 9). The average
sampie size was 3.91 m2 (s
2.17; n
311), and the efficiency of the
sampler is also comparable to the Bongo net (KLOPPMANN 1990). This paper
deals with a representative selection out of a total yield of almost 3700
fish 1arvae and some 60 taxa.
Abundance va lues (catch per unit of effort
cpue) are expressed as n/l m2 ,
either integrated over the total vertical range sampled for horizontal
distributions, or per individual step for vertica1 distributions.
=
=
=
Preservation of' anchovy larvae permitted direct ageing from daily growth
increments in sagittal citholii::hs for 23 specimens only (prevailing 4.5 10.0 mm TL). These data showed elose agreement with a broader length/age
key from the Mira estuary in April 1987 (R~ 1987; see also for literature
and methods), which was therefore applied to assess .the age from spawning
of the remaining material. We assume that the first growth ring was formed
at the end of the fourth day after spawning.
Por the spawning bathymetry of the selected species, the reader is generally referred to the origina11iterature reviewed e.g. in HUREAU & MONOD 1973
or WHITEHEAD et a1. 1984-86, some additional data of relevance will be
quoted be10w.
Ibe hydrographical situation:
Weak and variable wind conditions prevailed the 12 days prior to the survey
(SWA-data) •. The plankton survey coincided with an onset of upwe11ing favourable, stable wind directions, weakat 08 August and moderate winds up to
Beaufort force 5 at 09 - 12 August. The wind ceased and changed direction
again during transect D at 13 August, when the survey was about 60 % completed. This deve10pment was consistent in time from at least Vigo to
Peniche and is be10w referred to as "the observed event". However, it might
be argued that this event cou1d be traced back i::o 03 August at all 4 stations, though with instabilities in the beginning.
With a response time lag of 1 day (PIUZA et a1. 1982; JORGE DA SILVA 1992)
transects B to perhaps D shou1d show coasta1 upwelling, but coastal stations had 1ess wind forcing during the observed event than offshore stations
(Pig. 2), in agreement with the meteorologica1 situation (JORGE DA SILVA,
pers. comm.).
Horizonta11y, temperature and sa1inity (with coasta1.salinity m1n1ma due to
river p1umes) increased both towards offshore and southwards, from 19.0·C
3
or 35.4 psu to >22.0·C and 36.1 psu. Except for an isolated m1n1mum 18.8·C
offshore, the minima coincided with the event.
There was a permanent stratification in temperature and density, the diseontinuity layer was almost eonfined to the upper 50 m and the strongest
gradients oeeurred in the upper 30 m (e.g. Figs. 4 & 5). Upwelling did
mainly affect the vertical position and width of the thermo- and pyenoeline, which ascended near the eoast at transeets A - D (exeept in the river
plume), and corresponded with a bottom-parallel aseent of 35.7 psu water
from some 100 - 150 m to either the river p1ume or the surface (Fig. 6).
The sloping of isopleths and vertieal continuity of sa1inity diminished or
disappeared in the upper 100 m at transects E & F, in e10se response to the
wind event. Surface-near waters of ~35.7 psu were oxygen-oversaturated
(Fig. 7), and the eongrueney of the distribution patterns of all physical
parameters there is striking. The same salinity range at depths was oxygen-dep1eted.
Same upwelling-like structures were also found consistently below 100 m
depth (Figs. 5 - 7), but these struetures were uncorrelated to the observed
I.. ind
event, and the eongruency between the parameters was weaker. While
generally in the upper 200 m salinity (and temperature) decreased with
depth, at intermediate depth a wedge of somewhat higher salinity ~35.8 psu
was consistent1y present. Its inshore boundary depended on the vertica1
movement of 35.7 psu water.
Results:
Species composition and vertical distributions:
Among a total catch of 3670 fish 1arvae same 60 taxa have been identified.
As many of these taxa were rare, or, as e.g. for fami1y Gobiidae with at
least 3 species, specific identification was not possible for a11 specimens, some regrouping to higher taxa was done. The 15 resulting taxa listed
in Table 1 eomprise about 84 % of the total catch (standardised to cpue).
Some additional taxa of relevance will be mentioned below. The first ranking species was anchovy, E ~ ~.fu..6, with 29.4 % of the unquantified total catch or 24.6 % of total epue.
Average vertical distributions for more abundant or frequent taxa are
listed in Table 1, arranged from surface preference (top) to deep distribution (bottom) . The vertica1 resolution of samp1ing is with generally 30
m-steps fair1y coarse, particu1ar1y in respect to the sha110w mixed 1ayer
and narrow thermocline (Fig. 5). Nevertheless the patterns are not unusual
and may also be attributed to a preference for the mixed 1ayer, a mixed
1ayer-thermocline group, a thermocline pattern and a group preferring
subthermocline temperatures.
Zonation and drift:
Among a complex mixture of individual horizontal distribution patterns, the
following general patterns emerged:
1. "Stationary" taxa, not revealing any cross-shelf displacement fram the
spawning grounds of adu1ts. Within the stationary group, the fo110wing
eross-she1f zonations were observed (Fig. BA - BC):
1-A. Surface-near 1iving 1arvae of fami1y Soleidae (almost exclusive1y
B u e t o ~ ~ ) remained above the shallow, inshore habitat of adults
4
•
and coincided wi th the 1ess saline, or 1ess wind-exposed, inshore waters
(Pig. 8A). No second taxon revealed a simi1ar distribution.
1-B. C~nym.u. -6p. 1arvae remained above the midshe1f spawning grounds
(Pig. 8B). Preferring depths of some 30 - 60 m, they coincided most1y with
the intermediate wedge of somewhat higher sa1inities. Por the deeper 1ivine
1arvae some onshore transport may be assumed from Figure 9, whi1e 1ess
saline coasta1 surface waters were devoid of the species. A corresponding
horizontal distribution is found for 1arvae of the vertica11y extended
fami1y Gobiidae, except that they also occurred at most inshore stations.
The taxon is likely to inc1ude severa1 species spawning from shallow waters
to the she1f edge.
1-C) Generally larvae of oceanic species and extended-shal1ow distribution
remained exclusively beyond the shelf edge (Fig. 8C)~ An almost identical
offshore distribution showed (unexpected1y, see below) larvae of the oceanic-s10pe dwe1ling family Para1epididae in spite of a deep vertica1 range
60 to at least 200 m. Though also of oceanic oriein and with shallow distributed larvae (JOHN 1984 and literature therein), 1arvae of the oceanic
meso- to bathype1agic genus cyctotho~ make an exception. In spite of low
overall abundance they occurred untl1 the shelf stations adjacent to the
200 m depth contour, and, with a single specimen, at station B 4.
2. Taxa with offshore displacement:
Anchovy,' E ~ ~.&u., larvae hatch from eggs spawned at midshelf. There abundance maxima of larvae and minimum 1engths (ages) were
encountered (Figs. 10 & 12). Minimum 1engths coincided with the zone of
deepest occurrences of larvae (Fig. 11), and age distribution showed a Ushape cross-she1f (Pig. 12). Anchovy 1arvae of most1y 1arger age (together
with few trig1id, serranid or sparid 1arvae main1y at transect D) occurred
also offshore of the spawriing grounds a10ng the northern trarisects A - D,
but arichovy 1arvae of any size were absent in offshore waters of transects
E & F (a single trig1id 1arva was encountered at E 8). There was a relative
paucity of young 1arvae at all depths of transects B - D in contrast to the
surveys at the onset of the event or distinctly after it (transects A and
p).
A fairly similar horizontal distribution as found for anchovy; but with
'less extension seawards due to the absence of larger specimens, was observed for the eco1ogically weH comparab1e 1arvae· of Mn.ogto~ ~ .
Broad1y corresponding patterns were found also for Ce.pota. JU.Lbe,..6c.etv.> and
T ~ ~ , where with a somewhat more extended vertical distribution a sma1ler percentage of the larvae shou1d be affected by offshore
Ekman-transport.
3. Taxa with evident or anticipated onshore disp1acement:
The occurrence of larvae of the deep-sea genus cyeto~o~ above bottom
depths as shallow as 140 m (exceptiona1ly 100 m at station B 4) can only be
exp1ained by advection, though probab1y during the egg stage as 1arvae live
in surface waters. Simi1ar is likely for the single straggler of the slope
species MyctoProwrn ~ at station B 3 (see H&~ et a1. 1981).
~ o ~ ~ ~ larvae originate from a pseudoceanic (sensu HULLEY
1981) parental stock and hatch at some 150 - 300 m depth (JOHN & KLOPPMANN
1989). Literature data (JOHN 1985; .WEISS et a1. 1988) indicated drift with
the onshore compensation flow during upwelling. Larvae had their maximum
extension towards the shore at transects B & C (Pig. 13), but as the inshore boundary was not beyond the extreme records for adults, such dispersal
remains questionablein our survey~'
Larvae of other oceanic and slope-dwel1ing fami1ies were almost ,
deep-living Paralepididae comp~etely, absent above the shelf.
5
Discussion:
The inerease of surfaee temperature and salinity both towards offshore and
southwards is known for the area (DHI 1967; ANDRES et a1. 1992; own, unpublished data). The aetual surfaee temperatures showed upwelling-related
eoastal minima. but were warmer than long-term means for the month, wi th
o
anomalies of some +2°C offshore (eompared with DHI 1967) and +3.0 to 3.S C
at the eoast (eompared to data from off Leixoes and Peniehe, PIUZA et al.
1982).
It is 1ike1y, that the oeeurrence of the first ranking speeies anehovy,
En.g~ ~ ~ , was related to this temperature anomaly. The speeies was previously not eonsidered to be an important eomponent of Portuguese iehthyoplankton outside of estuaries (R~ 1991, and literature therein). The relative pauei ty of young larvae at transects B to D might be
interpreted as a eonsequenee of redueed anehovy-spawning during the observed event, whieh reached or exeeeded the eri tical threshold of 5 - 6 m/ s
defined by CURY & ROY (1989, assuming prey density to be affeeted) from 09
- 11 August. A baek-ealculation of birthdays for all larvae revea1ed a
eoincidenee of the absolute maximum of larvae born per day, as well as some
preceding weak modes, with winds from the south (which occurred during July
at northern locations 1 to 2 days earlier than off Leixoes). Assuming a
reduction of spawning intensity during northerly winds, the birthday histogram would correspond better to a triggering wind event starting on 03
August (Fig. 3, NW-wind 5 m/s), than to the event seale defined above on
base of eonsisteney.
While otherwise the speeies eomposition is not unusual for a summer survey,
the vertieal distributions eneountered may part1y be a result of the sha1low mixed 1ayer and strong temperature gradients (see e.g. RUSSELL 1976,
and literature therein).
Considering the eoarse vertieal resolution of samp1ing, most vertieal
distribution patterns agree fairly weIl with earlier resu1ts from the
NE-Atlantic boundary eurrent system (e.g. JOHN 1985), but not always with
data from shallower and turbulent British waters (RUSSELL 1976). As e.g.
eorroborated by a mueh wider vertieal distribution of san..dhta.. ~
larvae in the identieal station grid but with a deeper thermoeline during
autumn 1987 (ANDRES et a1. 1992), the vertieal distributions deseribed here
mayaiso be different from "normal" upwelling seasons.
Besides temperature, some further eongruencies between the spatial (horizontal and vertical) distribution of larvae and physica1 parameters were
revealed: anehovy larvae with aged upwelled water (characterized by temperatures >19°C, sa1inity 35.7 psu and oxygen saturation >100 %), Bu8~~­
um ~ larvae with less dense coastal water and C~ny~ larvae with
the intermediate wedge of higher salinities (>35.8 psu).
We regard the coastal temperature and salinity signal plus the time behaviour of the diseontinuity 1ayer as evidenee for (weak) upwe11ing. On base
of the congruent distribution of all parameters, we assurne here that the
distribution of 35.7 psu water is broadly representative for the origin and
spreading of upwelling water (but as a eonservative parameter salinity must
have integrated also past events, see below). The
upwelling water should
thus have originated from some 100 - 175 m depth above the slope, aseended
in the bottom-near layer over the shelf and arrived in the surfaee layer
either over midshelf (when the inshore low-density and less wind-exposed
river plume appeared to be coupled off from upwelling), or much closer to
the coast (in case there was no river plurne present). Upwelling water must
6
•
•
,------------
--
-
have got some 4 - 5°C warmer during the ascent by mLxLng.
The '11 tcrnati ve hypothesis , that upwelling water originated from shallow
pycnoeline depths only (JORGE DA SILVA, pers. comm.) would conform better
with the weak SST-signal, but would fail to explain the salinity signal,
the spreading of oxygen depleted waters (the absolute minima were below the
va lues at 300 m above the slope and thus result of local consumption), and
the time/depth behaviour of all parameters from mid pycnocline downwards;
Upwelledwater displaeed again westwards at the surfaee, where, eonsidering
the weak to moderate winds, the oversaturation with oxygen must have been
eaused by primary produetion. This watcr, however, eould not have been
upwelled during the observed event, as oversaturation was found already
from thc beginning of the event onwards, instead after the expected time
lag of some days. Biological resuits discussed below suggest, that these
waters aetual1y had ages of >10 - <43 days.
Offshore Ekman-drift and the deeper low-salinity layer appeared to be
separated by a permanent intermediate (100 - 30 m) layer of elevated salinity and probably reduced cross-shelf motion, separating deeper from surface waters under quiescent conditions, but ending wedge-like off the coast
during upweiling.
We presume, that the observed cross-shelf zonations of fish larvae depended
on the following interactions between spawning bathymetry, vertical distribution, and hydrography:
The U-shape of anchovy age distribution cross-shelf (Fig. 12) is likely to
have been caused by vertieally separated, opposite eross-coast dispersal
linkcd with both offshore Ekman-drift (for larvae with preference for
surface waters) and the onshore compensation flow (for the deeper stages),
as had been shown for ~ ~ by JOHN et al. (1980). The bottomnear vertica1 distribution of cpue for this speeies (as wel1 as for catttonymuh larvae) suggests also some onshore transport above the bottom from
midshelf to shallow depths.
The shown meridional differences in offshore distribution of surface living
anehovy larvae seemed to indicate a eoineidenee with the time-behaviour of
the observed upwelling event, but the time seales aetually did fit on1y
partly and to the younger cohorts:
As mentioned, the observed event had a directional consistency of 7 days
only, after a variable period of 12 days. A more generous interpretation
would yield an event scale of 12 days. Anehovy larvae with an age of 10 12 days had modes up to 10 nautical miles offshore of the spawning depths
at transeets B to D, while for the same agegroup the spatial differenee
was almost nil at transeet A during the beginning of the event. This dispersal (as well as that of e.g. Ä'U1.Ogto-MLU> ~ with a small length
range) may thus have been e10sely related to the observed event.
Contrary to this, anchovy 'larvae of any size (but not other eoasta1 speeies) were absent in offshore waters of transects E & F after the event. We
had above re1ated the paucity of youngest larvae to an inhibition of spawning during upweIIing, but some 1arvae eIder than 10 days should neverthe1ess have been expeeted at these southern slope stations.
Anehovy 1arvae 32 - 43 days old, and dispersed up to 37 nautiea1 mi1es
offshore from the respeetive zonal spawning bathymetry, must have been
dispersed also during the preceding event 06 - 10 July (12 Ju1y off Leixoes) and the minor one around 24 July, and were probab1y born mueh farther
northwards. These larvae were found in water masses showing the charaeteristies of aged upweiled water. JORGE DA SILVA (pers. eomm.) estimated the
place of origin to have been some 150 - 300 km to the north, between Viana
do Caste10 and Cape Finisterre.
As mentioned, for the bottom-near Iayer from midshelf to the eoast some
7
indication of an onshore transport is indicated for deeper C~ony~
larvae and respecti ve youngest anchovy, which did not, or less so, extend
into the less dense and less wind-exposed coastal waters (the data from
soleid larvae also suggest that these waters showed little spreading crosscoast). The overall horizontal distribution of C~ony~, however, indicates little cross-shelf net dispersal, as to be anticipated from the
prevailing medium-deep vertical distribution of the larvae.
Contrary to our expectations, there is contrasting evidence concerning the
onshore advec tion of deep-li v lng oceanic taxa. Deep-li ving Paralepididae
(fairly rare) did not spread at all beyond the shelf edge. Entrainment of
eggs, but not of shallow or extended-shallow larvae, by an earlier onshore
compensation flow (perhaps about 04 August?) is likely to have caused the
occurrence of cyeto~o~ larvae or the individual Myetophum ~ up to
the extreme midshelf stations B 3 & B 4.
The inshore limit of the horizontal distribution of ~ ~ ~ ~ 1S
almost identical as found for Cycto~OrLe., and for the deep living M.
~ larvae closest inshore at transects Band C a direct relation with
the upwelling event seems more likely, though the vertical distribution of
cpue of ~o~~ ~ ~ (Fig. 14) along the transects is somewhat ambiguous. It might be reasoned, that there was little volume transport in the
Ekman-layer (some 15 m deep), resulting in a much sma11er onshore velocity
of the vertically wider compensation current. Whi1e yolk-sac larvae of M.
~~ live at depth, with feeding they show a vertical ascent into the
upper layers in time sca1es of probably few days, but wi thout increasing
much in size (JOHN & KLOPPMANN 1989). This ascent could have consequently
smeared any indication of onshore transport in Pig. 14, which would have
become apparent during stronger upwelling. We consider it likely also, that
those drift patterns revealed above wou1d become more pronounced during
stronger upwelling, and that larvae of B~g~o~ ~ would also
become subject of Ekman transport.
Conclusions:
Stab1e stratification and anomalously high temperatures caused the unusual
offshore spawning of anchovy off Northern Portugal in summer 1989. Spawning
of anchovy was at maximum during periods with winds from the south. The
observed upwelling event was of short duration only and had low intensity,
particu1arly close to the coast. However, additionally signals of preceding
upwe11ing events were evident in the meteoro10gical, hydrographica1 and
biological data.
The cross-she1f zonation and dispersa1 of fish larvae depended on the
interaction of spawning bathymetry, vertica1 distribution of 1arvae and the
hydrographical conditions in the respective range, not a1ways consistent
during the entire planktonic phase before the time of catch.
Surface 1iving larvae of anchovy as wel1 as those of other midshelf species
showed dispersal offshore. For young larvae dispersal up to about 10 mi1es
from the spawning grounds was directly related to the observed upwe11ing
event, but for e1der 1arvae up to 43 days old, occurrences up to 37 miles
from the respective zonal spawning depths were re1ated also to two events
north of the surveyed area during July. Larvae from midshelf or igin hut
with a vertical distribution extending into the thermocline, 1ike e.g.
T ~ ~ or Ce.po~ ~~cen4, showed reduced offshore dispersal.
Soleid larvae living in less dense and less wind exposed coastal surface
waters appeared to be retained there. Larvae originating from midshe1f and
with medium-deep (subthermocline) vertical distribution as e.g. C~ny~
8
•
~p.
showed 1itt1e overall cross-she1f dispersal, though the deepest specimens of the very same group were advected somewhat from midshe1f towards
the coast.
The inshore boundaries of 1arvae of severa1 slope or oceanic species were
not a1ways as anticipated from their vertieal range. Some inshore oeeurrenees of shallow living larvae of e.g. cyceotho~ were attributed to an earlier entrainment of deeper living eggs. Evidence for an onshore adveetion
of deeper-living larvae of the slope speeies ~ ~ ~ with the
compensation flow is inconelusive, probably because the ontogenetical
aseent of feeding larvae occurred in the same or smaller time scale as
onshore flow.
It is presumed that under normal summer conditions (with more consistent
and stronger upwelling) all discussed dispersal patterns would become more
pronouneed, and that anehovy would not be a prineipal eomponent of Portuguese offshore ichthyoplankton.
Acknowledgements:
•
A. JORGE DA SILVA (Lisbon) informed us about the meteorological conditions
prior to our survey and provided an estimate of the scale of meridional
dispersal. Wind da ta obtained from SEEWETTERk~ Hk~BL~G were plotted by T.
XULLER and C. TIETZE (Kiel). We benefited from engaged and partly eontro.versial discussions of the hydrographieal situation with E. HAGEN (Warnemünde), A. JORGE DA SILVA (Lisbon) and W. ZENK (Kiel).
References:
H. G.; JOHN, H.-Ch. & R~, P. 1992: Fish larvae and Gammaridea
plankton off Northern Portugal during autumn 1987. Senckenbergiana
marit. 22 (3/6):179-201.
.
J~~Z, W. 1986: The two fa ces of E1 Nino 1982-83. Meeresforsch. 31 (1): 1 46.
BAKUN, A. & PARRISH, R.H. 1991: Comparative studies of coastal pelagic fish
reproductive habitats: the anchovy ( E ~ ancho~) of the southwestern Atlantie. lCES J. mar. Sei. 48 (3): 343 - 361.
Cu~Y,
P. & ROY, C. 1989: Optimal environmental window and pe1agic fish
recruitment suecess in upwelling areas. Can. J. Fish. aquat. Sei. 46:
670 - 680.
DHI 1967: Monatskarten für den Nordatlantischen Ozean. Deutsches Hydrographisches Institut, Hamburg
DICKSON, R.R., KELLY, P.M., COLEBROOK, J.M., WOOSTER, W.S. & CUSHlNG, D.H.
1988: North wind and production in the eastern North At1antic. J. Plankton Res. 10: 151 - 169.
.
E~ERY,
W.J. & DEWAR~ J.S. 1982: Mean temperature-salinity, salinity-depth
and temperature-depth curves for the North At1antic and the North Pacific. Prog. Oceanogr. 11: 219 - 305.
.
FIUZA, A.F.G., MACEDO, M.E. & GUERREIRO, M.R. 1982: C1imato1ogica1 space
and time variation of the Portuguese coastal upwelling. Oceanol. Acta 5
(1): 31 - 40.
GRASSHOFF, K., EHRHARDT, M. & KRE~LING, K. 1983: Methods of seawater analysis. Verlag Chemie, Weinheim: 419 pp.
HAMANN, I., JOHN, H.-Ch. & MITTELSTAEDT, E. 1981: Hydrography and its
effect on fish 1arvae 1n the Mauritanian upwe11ing area. Deep Sea Res.
28 A(6): 561 - 575.
.~~DRES,
9
HE~PEL,
G. (ed.) 1982: The Canary Current: Studies of an upwe11ing system.
Rapp. P.-v. Reun. CIEM 180: 455 pp.
HULLEY, P.A.J. 1981: Results of the research crU1ses of PRV "Walther
Herwig" to South America. LVIII. Pamily Myctophidae (Osteichthyes,
~yctophiformes). Arch. PischWiss. 31, Beih. 1, 300 pp.
HUREAU, J.G. & MONOD, Th. (eds.) 1973: Check list of the fishes of the
north-eastern At1antic and of the Mediterranean. Unesco, Paris: 681 pp.
JOHN, H.-Ch., BÖHDE, U. J. & NELLEN, W. 1980: ~ ~ larvae 1n
heir southernmost range. Arch. PischWiss. 31 (2): 67 - 85.
JOHN, H.-eh. 1984: Horizontal and vertica1 distribution of 1ance1et larvae
and fish 1arvae in the Sargasso Sea during spring 1979. Meeresforsch. 30
(3): 133 - 143.
JOHN, H.-Ch. 1985: Horizontal and vertical distribution patterns of fish
1arvae off NW Africa in relation to the environment. In: BAS, C., MARGALEP, R. & RUBI~S, P. (eds.): Simposio internaciona1 sobre las areas de
af1oramiento
mas importantes de1 oeste africano (Cabo B1anco
y
Bengue1a). Inst. Inv. Pesqueras, Barcelona, Vol. 1: 489 - 512.
JOHN, H.-Ch. & KLOPPMANN, M. 1989: Ontogenetic changes in the vertica1
distribution of larval ~o~~ ~ (Gme1in, 1789). Arch. PischWiss. 39 (2): 79 - 93
JORGE DA SILVA, A.J. 1992: Dependance of upwelling re1ated circulation on
wind forcing and stratification over the Portuguese northern shelf.
ICES, C.M., C: 17: 12 pp.
KLOPPMANN, ~. 1990: The sampling efficiency of a horizonta11y towed B~
multiple-opening-c1osing-net. ICES 1990, C.M., L: 97: 11 pp.
~INAS,
H.J.; PACKARD, T.T.; MINAS, M.; COSTE, B. 1982: An analysis of the
production-regeneration system in the coasta1 upwe11ing area off N.W.
Africa based on oxygen, nitrate and ammonium distributions. J. mar. Res.
40 (3): 615 - 641.
R~,
P. 1987: Ecology of the p1anktonic phase of the anchovy, Eng~
~ ~ (Linnaeus,
1758), within Mira estuary (Portugal). Inv.
Pesq. 51 (4): 581 - 598.
R~, P. 1991: SARP re1ated studies on anchovy 1n Portuguese estuaries.
ICES, C.M. L:5: 10 pp.
RUSSELL, P.S. 1976: The eggs and p1anktonic stages of British Marine Pishes. Academic Press, London: 524 pp.
WHITEHEAD, P.J.P., BAUCHOT, M.-L., HUREAU, J.-C., NIELSEN, J. & TORTONESE,
E. (eds.) 1984-86: Pishes of the North-eastern At1antic and the Mediterranean. 1-111. Unesco, Paris: 1473 pp.
WOOSTER, W.S., BAKUN, A. & MC LAIN, D.R. 1976: The seasonal upwel1ing cyc1e
along the eastern boundary of the North Atlantic. J. mar. Res. 34 (2):
131 - 141.
WEISS, G., HUBOLD, G. and A. C. T. BONECKER 1988 - Eggs and 1arvae of
~ ~ ~ (Gmelin, 1789) (Teleostei, Sternoptychidae) in
the
Southwest Atlantic. Meeresforsch. 32: 53 - 60.
WYATT, T. & P~REZ-GANDARAS, G. 1988: Ekman transport and sardine yie1ds in
western Iberia. In: WYATT, T. & L_~ETA, M.G. (eds.): Long term changes in Marine Fish Populations. Vigo, Instituto de Investigaciones Marinas: 125 - 138.
10
ON
38
•
.,- ~#;
.-~ #,'" •••'
Pig. 1: The sur,ey area off tbe western Iberian
Peninsula and location of reference points
mentioned in the telt.
.,,: '.'
L---..,---,-----r----,--..........,---,----+ 36
°W
12
10
6
8
9°
10°
11°W
'E
o
o
N
:::::::::::::::::::::::::::::::
...............................
...............................
. . . ........ . ......... . . . . ..... .
::::::0:::::
. :::::::::::::
:::::::::::::::
'. ,
............. ..
)'
..r-."
.::::ä:::::::.:::::::"::::::~
. . . . . . . .. . . . .. . . . . . . .. .. . . . . :~:::~::o
::: ::::::::::::::::::::::::::::
.
i:
/, 1°30'
...
N
.~'"' .
.9:
A 13-1
0
-=---
/
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~: ~ :i ~: J:.: :1 ~ ~ ~ j.~ ~ ::::::::.... ~
:::::;::::
:~:::: : ~: ~T T:: :::~: ~~.~ .:~ ::.::~: :)'~: ~~TJ. :t~~UJ. k~:
...............
'~'~'~'~';
Lei x 0 es
B 12-'
::::::::
~\"
~
:::::::::::: .••••••••••••••••••••••••• :•••••••••• f::::::::
:::::::::::::::,
:::::::::
:::::::::::::::::~
••••••••••••••••••••••• 't.. •••••••• ::::::::.
: :S : : ;,: :
.:
~ ~ ~ ~ ~~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ .r:::::.;::::::~::.;::~ ~:
~
~:: ~~ ~ ~~
.
~~~~~~~~~~~~~~~~~~ '::::::::::::::::::: :.~.:..::~:~:~:~:.::.:~~~~~~~~~:::'
.
..
::::::~.:·T :;~~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~ ~}:~):~::.~~}~:::~ ~.
:::::::: ::::: ::::::~.~ .:.;. ;.;.;.~ .~..~..:.~. ~.;.~ .~.:': ::::'
::::: :::: :::::...........................................
::::: :::: ::::::: ::::::::::::::: :::::::: ..\.
/-
C 13~
o
13-'
--....-
/.,
o
o
0 . . . . :~:. :. . . . . . .
.'
c
'I
0
0
E 11.-1
~
j
,
\
o
•
• •
~
0
o
Ci
I
0
0
0
0
00
F 11.-1
+-----......------r------'-......- - - - -.......L..::..-::......--,.:...
:::;.-.----+/,O°
Pig. 2: The grid sa.p1ed off lorthern Portugal. Lettera A to P refer to trlnaeets and nu.erala
to standard station nu.bera aacending fro. the coast, regard1ess of the direetion (see arrows)
of sa.pling. Crosses represent CTD-casts only. Open eireles represent daytime CTD/plankton
stationa, full cirelea nightti.e stations Ind eroaaed eireles CTD-easts/twilight plankton tows.
Shading depicts npwelling fa,ourable (Bi to I) wind direetioDs at stations, different srey
shadings represent Beaufort forces 3 (licht) to ) (dark).
11
8 Lelxoe9
WInd
ROUTIN
z=
0.000 M
6
2
I/l
"E 0
-2
-6
Pig. 3: A.ind-vector ti.e-series 01 July - 15 August 1989 fro. Leiloes. Sticks fly with
the .ind towards the line of 0 ./s. positive va1ues thus represent a southward coaponent
of lIindstress.
rab1e 1: Relative vertical distributions of fish tala of anl abundance or frequencl, as based on
cUllulated catches per unit of effort.
Pattern
Talon
Stations
positive
t cpue
0-30 •
%
30-60 •
(=100%)
%
60-90 •
%
90-120
11
120-200 •
%
%
a11 fish larvae
75
1007.0
58.8
22.2
9.3
4.0
5.7
Sparidae
E. e.tl.e..ta..Uc.otLu.
8
40
34
14
12
15
17
8.8
248.1
54.9
18.5
25.6
7.6
12.7
97
86.6
80.1
75.7
72.7
70
68.5
0
9.9
16.4
22.7
27.3
30
18.1
2
1.8
1.8
1.6
0
0
2.4
1
1.1
0
0
0
0
0
0
0.6
1.6
0
0
11.0
17·
19
23
32
22.5
14.2
14.9
184.8
52.9
40.8
33.6
31.8
42.7
45.8
47.7
48.2
3.6
7.7
12.8
14.8
0.9
0
2.7
4.7
0
5.6
3.4
0.5
11
26
9.7
136.9
34
15.1
53
57.6
10
20.4
3
5.7
0
1.2
18.6
9.7
10.2
68.4
6.4
6.4
21.0
28.2
20.4
15.4
38.7
43.6
----------------------------------------------------------------------------------.--------------------
Shallo.
A. ta.twta.
C.
JULb~c.eM
B. tu.twm
S.
pU~
Cyc.totkou
0
-------------------------------------------------------------------------------------------------------
llitended- T. ~
shaUo.
B. 9.ta.c..Utt.q.
M.
PlLIl.c.ta..twn
Cobiidae
----------------------------------------------------------------------.--------------------------------
Mediu.
Triglidae
Ca..tUon.yllllU
------------------------------------------------------------------------------------------------------Deep
Paralepididae
M. mu.tU2M.
32
41
12
11'OO'W
200 km
10'00'
l1'OO'W
09'00'
10'00'
200 km
150
:-]70
09'00'
100
'SO
SO
SO
SO
100
100
ISO
-------------====--------''-------'-200
200
.
~25.0
~
ISO
A
>-27.S
------------------'=""--
0
SO
SO
'00
100
~27.0
>-27.5
B
'SO
09 - 10
m
200
=:::
0
SO
=-27.0
B
~12
SO
""'_==_20_
'00
C
>-275
100
------------------
150
200
=-
~25.0
>21
SO
0
100
150
:>27.5
c
ISO
,,",12
----------------------'----------'-200
11 - 12
~27
'SO
--------------------<~--------l.200
>20
so
100
0
200
-150
200
>25.0
>21
SO
SO
>27.0
---------~
100
>-27.5
E
150
------~12
13-1<
100
>1 )
E
200
150
200
SO
""'27.0
100
:>-275
F
'00
ISO
F
1L - 15
-------------->.:.-'-'-2---'-
200
PiC' 4: The ,ertical stracture of ia situ dealit, aaoaal, (ksf.3)
aloDS traasects A - P, 01 - 15 A.~ual 1989.
150
-'-200
Pie. 5: The ,ertical distributioDs of te.perature ('C, al for Pis. 4).
13
200
'00
ISO
km
.
0
260 km
.
.
09·00'
so•
10·00'
11·00·W
09·00'
so
10·00'
11·00·W
I
I
.00
ISO
---1
o
. >100
>359
50
50
-IQO
'00
>351
ISO
ISO
200
>=
50
SO
'00
'00
B
.so
.50
~80
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _..LAL
~35.6
--I.ZOO
o
»10 :
>;100
50
50
~35.8
100
00
------------------~
_ _ _ _ _ _ _ _ _~..:3..:5..:6
'50
150
L
_ _ _ _ _ _ _ _ _ _ _ _.L-
J200
Pico 7: The yertical distributioD of OII&en saturation (I) along
transects A to C uDtil fail.re of the probe.
~
~
~~35.8
.00
o
150
>35.6
SO
100
E
------
150
----l200
L:...:=l-_--L
50
>35.9
'00
F
>35.1
,so
m
---------------..I:....-------------.l2oo
'i~.
,: 1he yerticil
-'-ZOO
distributioD of pr.ctic.l s.liDitJ (.s for 'ic. 4).
•
14
,
11' W
g'
10'
8'
'E
~
Soleidae
(nl1m' )
... J
0
0
0
0
0
0
0
0
0
0
0
0
,9'
,,
0
""
0)
0
N
..,
\-
(
0
0
I
\
41'30'
41'
0
"
J
0
0
0
0
0
0
0
0
0
0
~"
j
0
0
0
p" 0
0
0
0
40'30'
/f"
0
0
0
0
0
7
o
('I
"
0
0
0
0
0
0
\
9
0
0
0
0
40'
Callionymua
app.
(nI1m' )
0
0
0
0
0
0
0
0
0
0
0
41'30'
N
0
0
41'
0
0
0
0
0
0
0
0
0
0
0
0
0
40'30'
0
0
0
0
0
0
0
0
0
0
0
0
40'
'E
•
~,
•
0
0
.......,,
•
0
0
0
0
9' 0
"
",
• • •
0
41'30'
N
'-
.(
0
0
0
'\
41'
"
'j
e
•
•
•
0
•
•
0
•
0
~
0
0
\;
I
•
0
• •.'
;/0
40'30'
,,/
•
0
0
•
••
0
•
0
0
0
.)
,
0
0
0
0
<,
•
\
0
pis. 8: The croBB-shelf zonation of
0
0
40'
eBtationarJ •
taza.
A, top: lIearahore, aurface-li.iDI' I, ceDtre: .idahelf, ~diwadeep, C, botto.: oceanic, eltellded-shallow ,ertical distributioll,
15
Ogooo'
10°00'
i
I
!
I
!
o
SO
150
~
__
. __
I-+_+-_~
O·'IO··L1J
~I
z.,
~
50
ulJ7
v
n.'
I.t
•. 1
•. t
./
1.'
ISO
A
L...L_l.--'-.......L-
0
0
0
0
•., J···lJ
1.1.V'
LI·
0
t 00
0
0
ul
0
ISO
... ... ~
100
(
150
7"
c
,.t
I.l
0
0
150
m
..,
I.S
~7/
-
o
SO
V
I
100
E
150
200
...
....., ...... ... .. ... Tof7'r7
··V
•. 1
'.1
.
SO
... ... ... i?"
7~~
t 00
F
I 50
m
200
.1
Pico 9: The ,ertical distributioD of caltio~~ lar,ae (nil
for
positi,e Iteps; zero ,alues are left blank for reasons of clarit,),
•
0
0
o
0
. . . .---..:..:...:...r_~~----:~~~~--_r_----_+1.0·
Pig. 10: The horizontal distribution of
100
11.1 l./
... ...... ...... 1'·'/
I.J
0
0
+----~-----
200
•. 1
1.0"30'
50
... l)?
1
0
0
I.·' 1-7'
'·'W
..,'/'
@
50
200
I .•
0
0
o
W
,.t
...
,..
0
0
50
200
l.l
0
V
B
I.J
0
.l.200
[7
L--
6'
1.1·30'
N
100
10·
...
9'
10·
11· W
o
16
~ ~~
lar,ae •
11'OO'W
10'00'
09'00'
~.~r-----'--~l--""'·--:""--r-----L------,-.:":"":.
:...:-
260 km
'50
'00
0.'
-
_.. _
- - a.•
-
10'00'
09'00'
-2'00-km----'----,T;0----:....c.:..:.---."oo.---'------,so,-''--- - - - - - - ; ,
L.'
0
'a ), " .• ,. ',OIJ
1--1-- t--
--- - - f -
---
11·00'W
--j
50
O.10.!)~
50
~
t---- f--- I---
'00
v
r----.------,---r---~-.,--~-
A
150
.
...
U
0.'
-
]].0
'4.4
,ol .J./
'-'
00
/
1
C
-7
s.s
0.'
1.0
so
•.IV
0.'
.., ...
o
1·,luW
B
... I'-'lI.) ~
0.'
... 17"
V
•
~
c
0.'
..
so
i
!
zoo
o
-+-
t7
t7'
1
100
t
150
0
D
• .
t
-t-
10.
0.) 11.]
14 i
E
'0
0
+-L
;
f
t
Pig. 12: The cross shelf age-distribution (d
d
JO
= dars)
t~
of
~ ~ ~ lar,ae fro. the upper 30 •• The length
150
m
of the horizontal bar in each cross is a relatile .easure
for the Du.her of indi,iduals per age group. The fnll
triangle indicates the positioo of the 200 • depth contour.
200
so
100
F
•
11
100
I~
20
F
m
200
so
~t7V
. t:f:
150
,
'-'I /
V
so
uluJV
o.•y
I-
E
100
0
d
JO
10
T
so
0.' 0.01'·' t7
0.•} 7
0.'
0.)
0
20
1
0.] ,.,
\
'0
1
200
0\
!:
>~-L : [~
' - - - - ' - - ' - - - ' - - - ' ' - - - - - - - - ' 200
0.)
~
I-l-+:t:
1!'>Q
m
--'-_-'-_'---'---J 1 - - - - - - - - - - - - - ' - 2 0 0
- - J . -_ _--'-_ _
Pig. 11: The lertical distribution of EAg'I~tL6 eAe4l~eo~
larlae along the traolects (al for Pig. 9).
17
9'
10'
11' W
S·
11'00'W
,
10'00'
,
I
ISO
'E
09'00'
I
o
M
o
0
0.1
Ll'30'
N
'"
0'
0.'
0.'
0'
0.'
"
0
'0
0.'
)
-19
0
0
0
o
0
0
0
o
0
SO
100
ISO
A
0.'
Jzoo
0
0.'
1.0
"0
0.1
0.)
0.1
1.1
.'
0.'
0.'
1.1
7
,
. 0.)
1
0
'00
ISO
B
0.)
0.'
0
+-----.----=--=.T"""----.:-r----__r--'l-'>~~-__r-----_+
I
0.'
..,
'-'
~
0.)
0.'
0.'
0.1
0.)
0.'
0.'
LI O.S
0.'
..,
t:7'
0.'
I.)
~ljtU4 ~
I
J./
~
If
c
LO'
o
SO
100
\ SO
200
larfae.
~
0.)
0.1
O.S
0.'
"0
..,
0.1
f:/
T
0.'
Pig. 13: The horizontal distribution of
SO
200
O.S
0
7
L0'30'
0.1
\
i
V
0.'
0.)
t/
9
0.)
p'
0
:v
0.)
0.)
o
I I-J
0.)
®f'
o
0)
"
0.'
L l'
'@';i
@ /.'
i
0
O.
o .-0"
\
-e: 1.0
0)
0
l---L._L....L--<f-
\
o
0
0.'
0)
...
0.1
..0
0
SO
o
y,
0
-1
I
I
100
0.'
0.)
0.'
0.'
0.'
0.1
.,V'
U
0.'
so
F7
os
0.'
o
f77
100
0
\50
m
200
I
I /
V
0.1
0.'
0.)
'.0
0.'
o.
o
L/
so
\00
f-17V
0./ V"-
E
>---.
200
1 17'
0.)
0.'
ff
0.'
0.'
0.)
0.'
0.)
0.'
O.S
0.'
150
0.'
1.1
0.1
0.'
I7~V
50
v?
'00
F
\50
200
Pig. 14: The ,ertical distribution of
aloDg the traDsects (as for Pig. 9).
18
~~ ~
lar,ae