47

completed 6-7 days post-hatch at 7°C (Laurence, 1974).
Lab-reared larvae were considered metamorphosed (c.

lo mm, 1000 ug dry wt) in 30 days at 99C and 40-50 days
at 79°C. Fig. 1 depicts the principal haddock spawning
time and area on Georges Bank, the generalized egg and
larval drift, and areas where demersal Q-group fish are
most abundant 6-8 months later (Grosslein and Hennemuth,
1973). The distribution of late stage eggs and recently-
hatched larvae indicate that dispersion from the spawning
center on northeast Georges follows the general pattern
of drift, predominantly to the southwest at 1-4 miles/d
(2-7 km/d) (Walford, 1938; Marak and Colton, 1961; Colton,
1965; Smith et al., 1979). During April-May, high concen-
trations of larvae (>0.1/m3) can be found along the southern
flank of Georges between the 60 and 100 m isobaths. Some

i Sc ee | | |

Fig. l. Principal haddock spawning area on Georges Bank and
generalized larval drift (indicated by arrows) and areas
where demersal 0-group haddock are most abundant 6-8 months
later.


11

PROBABILITY .

L «7 HADDOCK e— |
P=. 9(1-. 72EXP (-. 0045 (W-Wmin) ))

COB o——
P=, 9(1-. B7EXP (-. 004 (W-Wmin)

2 2 4 6 8

12° W-Wmin (ug)

Figure 5. Relationship of the probability of capturing an encountered
prey organism and larval size of cod and haddock.

12


13

Blaxter, J. H. S. and M. E. Staines. 1971. Food searching potential in marine
fish larvae. Proc. 4th European Marine Biol. Symposium. Ed. by D. J. Crisp.
‘Cambridge University Press. pp. 467-481.

Braum, £. 1964. Experimentelle Untersuchungen zur ersten Nahrungsautnahme
und Biologie an Jungfischen von Blaufelchen (Coregonus wartmanni Bloch),
Weissfelchen (Coregonus fera Jurine) und Hechten (Esox Tucius L.). Arch.
Hydrobiol. 28(2/3):183-244.

- 1967. Yne survival of fish larvae with reference to their feeding
behaviour and the food supply. In The biological basis of freshwater
fish production, Ed. by S. D. Gerking. Blackwell Scientific Publications,
Oxford. pp. 113-131.

Buckley, L. B. and D. W. Dillman. 1982. Nitrogen utilization by larval
summer flounder (Paralichthys dentatus). J. Exp. Mar. Biol. Ecol.
59:243-256.

Colton, J. B. and R. R. Marak. 1969. Guide for identifying the common
planktonic fish eggs and larvae of continental shelf waters, Cape Sable
to Block Island. Bureau of Commercial Fisheries Biological Laboratory,
Woods Hole, Massachusetts. Laboratory Reference No. 69-9.

Duka, L. A. 1969. Feeding of larvae of the anchovy Engraulis encrasicholus
Maeoticus Pusanov, in the Azov Sea. Prob. Ichthyol. 9:223-230. (transl.
from Vopr. Ikhtiol.)

Eldridge, M., T. Echeverria and J. A. Whipple. 1977. Energetics of Pacific

herring (Clupea harengus pallasi) embryos and larvae exposed to low
concentrations of benzene, a monoaromatic component of crude oi]. Trans.
Am. Fish. Soc. 106(5):452-461.

Ellertsen, B., P. Solemdal, S. Sundby, S. Tilseth, T. Westgard and V. Qiestad.
1981. Feeding and vertical distribution of cod larvae in relation to
availability of prey organisms. Rapp. P.-v. Reun. Cons. int. Explor.
Mer, 178:317-319.

Gray, J. 1926. The growth of fish. I. The relationship between embryo
and yolk in Salmo fario. J. Exp. Biol. 4: 214-225.

Harding, D., J. H. Nichols and D. S. Tungate. 1978. The spawning of plaice
(Pleuronectes platessa L.) in the southern North Sea and English Channel.
Rapp. P.-v. Reun. Cons. int. Explor. Mer, 172:102-113.

Hardy, J. D., Jr. 1978. Development of fishes of the mid-Atlantic Bight.
Vol. 11, Anguillidae through Syngathidae. U. S. Dept. of Interior,
Fish Wildl. Serv.

Hargrave, B. T. and G. H. Geen. 1970. Effects of copepod grazing on two
natural phytoplankton populations. J. Fish. Res.Board Can 27:1395-1403.


FREQUENCY

15

12

142

“37 SURVIVORS OF 10208
3 PREY/LITER
DAY 42
L ¥e437. 64289. 3
1 1 1
a ze & 8 8 & &

LARVAL. WEIGHT (ug)

Figure 36. Frequency histogram of the distribution of weights of ‘larval
~ cod survivors. on day. 42-from a large population run (10,000
initially) with the 3 3 stochastic element model at a prey
density of 3 liter" .


FREQUENCY

78
65

25

15
18

137

HADDOCK

DAY 14

38% SURVIVAL

38 PREY/LITER
Xe171. 8465. 1

uh

im 1 n 1
8 &€ 8 8

LARVAL WEIGHT (ug)

725+

Figure 31. Frequency histogram of the weight distribution from a 3
stochastic element model run at a prey density of 30 liter”
for haddock larvae at 14 days after hatching.

1





6%) LHOTSA AMO
8001 OS6 B26 BSB BB BSL BBL BS9 BB9 BSS BOS Ar BBr BSE BE BS2 Bez BSI aBI ws B

107
\

T

T

T

a rs

a

(20-1 WSTTOSYLAW ATIVG

a

Bt

Be

BE

ar

as

ag

aL

a8

06

B01

(SLL * AD
18°) ¥e=W GOD

(789 *. ASED ">
¢e=W MOOCOVH

Based on empirical respirometer

Daily (24-hr) metabolic expenditure of cod and haddock larvae
measurements from Laurence (1978).

as a function of body size.

Figure 1.


56

bottle collections also are used to make discrete observa-
tions. of micro-zooplankton, nutrients, and phytoplankton
biomass measures by. conventional methods. Continuous in-
situ fluorescence is measured at the same time by deploying
an ENDECO submersible fluorometer (Turner Designs Model) :
with on-deck recording of depth, fluorescence, and tempera-
ture via conducting cable. A recently acquired Variosens
in-situ fluorometer will be interfaced with the CTD.

Real-time zaoplankton processing

In process-oriented studies there is need for real-time
results so that decisions can be made to optimize the ex-
perimental operations. A methced we employ at sea to make
routine, quantitative analyses of plankton-net samples
using silhouette photography techniques coupled with a
microfiche reader, an. electronic digitizer, and a small
personal computer is described by Lough and Potter (1983).
More than 90% of the organisms can be identified to species
level and life stage, and a subsample enumerated within
20 min after collecting by this method.

A HIAC Criterion PC320 12-channel particle counting and
sizing system (Pugh, 1978; Tungate and Reynolds, 1980) has
been acquired for development as a real-time tool for the
quantification of marine plankton. Three sensors. (CMH-150,
CMH-600,°E=2500) are used to count particles in the range
of 5-2500 um. However, at present we process Niskin bottle
water samples only. in a batch mode. -The HIAC unit has been
interfaced with a. Canberra Multi-Channel Analyzer and. an
HP-85 computer system to control all settings and. functions.
The instrument is being modified for in-situ particle pro-

filing along the lines reported by Tilseth and Ellertsen
(1984).



FREQUENCY

12

140

HADDOCK

DAY 35
37% SURVIVAL
38 PREY/LITER
Xe814. 64528. 7

fila nn
af g

- - 8

LARVAL WEIGHT Cug>

a.

Figure 34. Frequency: histogram of the. weight. distribution from a 3.
stochastic. element model run at a.prey density of 30 liter”
for haddock: larvae at 35 days after hatching.

1



67

10 mg chl a/m? near the bottom, apparently due to sinking of
larger diatoms and dinoflagellates (Busch and Mountain,
1982). Nanno-phytoplankton (<20 um) biomass was evenly dis-
tributed throughout the water column at 1-2 mg chl a/m?,

The vertical distribution of gadid eggs was low at the sur-
face and also generally increased in density with depth to
a maximum at the bottom (Pig. 9). The cod larvae were sepa-
rated into two size groups for analysis (3-8 mm and >8 mm)

25-29 APRIL 1981 MOC 168-186

3- 8mm LARVAE >8mm LARVAE
Nasiooms> NO./100M>
ad 4a 20 QO 20 40 60 ae 4a 20 0 20 4 60
— — —— ms

Or pay nicHT = '°
~ 2% 20
= 30 30 *
x= ® ® *
40 40
g
Q 50 sO
60 60
rol tor1om= = s7710oM2 — gl 6rIOMe = 1artOM?
GADID EGGS MOC 170
NO./100MmTM
°° 200 400 GADUS MORHUA
tof GEORGES BANK
AA MOCNESS —1
~ 2 Z
= x0
z
§ 40 re
QS s0 3 WEIGHTED MEAN DEPTH
60
vo 1888/10M2

Fig. 9. Vertical distribution of cod larvae and gadid eggs
collected by 1 m MOCNESS (333 um mesh) on the southeast part
of Georges Bank (41020'N 66953'W), 25-29 April 1981.


with increasing body length. There is some indication that older larvae may feed
in reduced light (Blaxter, 1969).

The swimming ability of larvae directly determines the amount of water
searched for prey as well as metabolic expenditures of energy. When food is
scarce, weaker-swimming larvae would be subject to starvation because of the
lowered frequency of contact with prey organisms. Swimming capability as
measured in speed tests are summarized in Table 5 from Theilacker and Dorsey
(1980) showing species specific results for burst and cruising measurements.

The combination of swimming ability as measured by linear speed and
perception as measured by visual field produce a functional measure of the
actual volume of water a larva is capable of searching. The volumes are small
in the range of 0.1's to 10.0's of liters per hour as indicated by the compilation
in Table 6.

Success or failure of feeding responses has been observed by some researchers
to influence larval mortality. Blaxter (1962) reported a failure of some herring
larvae to feed at all. Schulmann (1965) attributed failure of Pacific sardine
larvae to feed to a “non-feeding behavior" in which the larvae would "give up" if
initially unsuccessful. First feeding success is typically lower than for success
of older, larger larvae within a given species, although there can be a significant
difference between species that are approximately the same age. As examples:
larval anchovy captured food successfully 10% of the time at first feeding
increasing to 90: in 3 weeks (Hunter, 1972); initial feeding success of herring
larvae was 2-6% and 32-62% for plaice (Blaxter and Staines, 1971). These differ-
ences are attributed to swimming abilities by the researchers.

The required food ration of larvae for growth is of prime importance in
survival and successful development. All physiological and developmental processes
require energy in the form of food. The processes involved include growth,
metabolism, digestion, assimilation, excretion and osmoregulation. The bioener-
getic relationships of these processes for early life stages have only recently
been studied and quantitated in a holistic way (Vlymen, 1974; Laurence, 1977;
Beyer and Laurence, 1980; Houde and Schekter, 1982). The review by Theilacker
and Dorsey (1980) presents summaries of research results for many of the
individual factors involved in larval energetics. Clearly, most of the processes
are species specific and/or temperature dependent and generalizations are difficult
with the present state of knowledge. Table 7 from Theilacker and Dorsey for
growth efficiencies and associated parameters gives, perhaps, the most valid
general comparison of known information between larval marine species.

Absolute nutritional requirements for fish larvae, especially non-salmonids,
are virtually unknown, For fishes in general, proteins are the largest single
class of natural dietary component. Twenty-three amino acids occur in natural
fish foods, 10 of which are incapable of being synthesized by fish and are
therefore essential. Tests in feeding young salmonids and freshwater species
show that gross protein requirements as a percent of diet are highest in initial
feeding stages and decrease as size increases (National Research Council, Subcom-
mittee on Cold Water Fish Nutrition, 1981). For maximum growth, young fish must
ingest a diet nearly half of which is digestable protein containing at least the


FREQUENCY

ww

116

LARVAL HADDOCK - 68.1 ug
25 PREY/LITRE
Ke61. 246.1
g g 8 5 6 8 & g & =
# PREY/DAY

Figure 10. Frequency histograms of the normalized distribution of # of

+. prey of preferred size-consumed’ day~* ‘for a newly ha
68.1. wg haddock larva at a ‘prey density of 25 liter”

pched


FREQUENCY

u

12

ot]

122

PREFERRED PREY=2. Sug

. o ~ in o.

PREY WEIGHT (ug)

Figure 16. Frequency histogram of the distribution of prey size about
the preferred prey size for a 250 ug haddock larva.

18


62

66°30 W
41°30'N.
41°00 F 56
L
COO LARVAE
NO./tom2
16-18 APRIL 1981
618333
He30'N
41°00"
| COO LARVAE
per" NO./10M2
i: 19-21 MAY 1981
we 618333
L ‘ .

Fig. 5. Cod larval distributions from April and May 1981
grid surveys. Densities contoured by factor level of 4.


Il.

c.

20

Timing
1. Critical
2. Diurnal

General Experimental Studies

A.

Endogenous Nourishment

1.
2.

Chemical Constituents

Sequence of Utilization

First Exogenous Feeding

1.
2.

Timing

Food Size Preference and Absolute Requirements

Delayed Feeding

1.
2.
3.
4.

Delayed First Feeding

Delayed Feeding of Older Larvae

Temperature Effects on Timing

Comparisons Between Species

Growth and Mortality vs. Food Density and/or Physical Factors

1.

T, Sal, Pollutants, etc.

2. Age and Growth (otoliths, chemical indicators)

3. Competition
a. interspecific, intraspecific, cannabalism

Starvation

1. Initial Post Hatch Starvation

2. Condition of Older Larvae and Starvation

3. Size and Condition @ Starvation :

4. Sequence of Events During Starvation Process (behavioral,
physiological, chemical)

5. Bioassays

1.

Feeding levels in Assays Interpreted in Relation to Toxic
Insult Effects and Interactions


91

population (Fig. 43), it. can be seen that the survivors definitely come
from the upper range of weights of the whole population. The
implication is that larger initial larvae have a higher probability of
initial growth and subsequent or consequential survival.

ASPECTS OF FOOD LIMITATION OF LARVAE AND PREDATION
PRESSURE BY LARVAE ON THEIR FOOD RESOURCE

A primary goal of this modelling effort was to assess food-limited
growth and survival of cod and haddock larvae on Georges Bank. A
combination of model simulations and empirical field data from Georges
Bank research cruises allowed this to be done. The method was to use
MARMAP field data on seasonal abundances and production of cod and
haddock larvae (Table 3) (Smith et al., 1979, 1981), fine-scale
estimates of relevant larval fish prey abundance from process-oriented
research cruises (Table 4) (Lough, 1984; Laurence et al., 1984), and
model simulations to calculate the required food intake of the indicated
amount of larvae from the individual amount of prey organisms.

The following results of this approach are based on the use of
conservative parameters from the field data. The total volume of water
on Georges Bank within the }90 q contour (where cod and haddock larvae
mainly reside) is 2.96 x 10*¢ m° (Green, J. R. pers. comm.) (Fig. 44).
The highest abundance of cod or haddock larvae from the MARMAP data base
(Table 3) was for haddock in 1980 at 743.8 x 10”. This would give a
peak haddock abundance of 0.25 larvae per m’ (Fig. 44). The mean
relevant larval prey density from the process-oriented research bottle
sqmples (Table 4) is approximately 14 organisms liter! or 14 x 10 per
m’. This gives an overwhelming ratio of instantaneous abundances of
55,000 to 1 prey organisms over larvae in a m’ within the 100 m contour
(Fig. 44). A model simulation was used to assess the more dynamic
aspects of larvae grazing the prey. The model subroutine dealing with
feeding and growth parameters (equations 1-14) was used to
deterministically calculate the prey consumption of preferred prey sjze
for an average of cod and haddock larvae at a growth rate of 8% dayTM*,
at 7° C, and from hatching - yolk absorption until a dry weight of
1000 yg. The calculated consumption was = 1700 prey (Fig. 44). This
was conservatively matched with total annual larval production for the
entire peak season of 110 x 10 2 larvae (Table 3) to derive a seasonal
(not instantaneous) grazing requirement of 188 x 10 5 organisms (Fig.
44) for the entire larval population produced. A comparison of the
larval population's seasonal requirement with the instantaneous estimate
of prey abundance shows a ratio of 1 to 4.5. This means that the
instantaneous (not even considering any food production aspects)
estimate of prey should be enough to allow 22% of the entire annual
production of larvae to survive and grow at 8% dayTM*.

Of course the larvae must encounter the food and capture it after
encounter, and this is what the modelling is all about. But, in
general, it would appear that food is not the single limiting,
catastrophically critical factor.


27

Table 3. Average densities of microcopepods in the sea. (Table 5 from Theilacker and Dorsey, 1980).

Average density of
microcopepods
(number per liter)

nauplii copepodites total Location Reference
13 2 15 Southeast Coast of Kyoshu Yokota et al. 1961
22 36 582 California Current Beers and Stewart 1967
S 40 5 452 Southern California near shore Reers and Steward 1970
a 27 7 343 Eastern Topical Pacific Beers and Steward 1971
S 36 1 7 California Current Arthur 1977
— 7 +419 ~*~«~8S”~S~*~«S SeassSSsS*=~<C*=‘_‘TMSTMS;*;*;*;*SMUKBCWOO”STMC*TM*TM*TM~*~“‘CS(C#C#C*TMW
8 - - 2234 Gulf of Taganrog Mikhman 1969
= 3 40 - 40 North Sea (0-10 m) Ellertsen et al. 1980
xo 20-30 - 25 North Sea (10-20 m) " "

mean for all stations and years given in publication listed in table (Hunter, in press).
2Includes al? copepods passing 202 um mesh net.
3tncludes all copepods passing 202 um mesh net and caught on 35 um mesh.

j Defines as food of Clupeonella delicatula; microcopepods account for over 90% of items eaten (Mikhman
1969).



52

as synoptically as possible at the population level. However,
since populations af larvae, their prey and predators usually
eccur at different scales, an array of. sampling gear is re-
quired which tends to negate simultaneous sampling, unless
more than one. research vessel is used. Nevertheless, we can
approach near synopticity for some elements of the sampling
program utilizing just one vessel. ,

The Fotary > tides (12.4 h period) are the dominant forcing
function on the bank so that experiments should be nested
within its space-time domain. According to the Nyquist
theorem, which states that a function can be detected if its
period ‘is’ at Least twice the sampling frequency, station
sampling on a grid would have to be taken at least once every
6 h at a sampling distance between 5 and 20 miles (9 and
37. km) depending on bottom depth. And in order to encom- ,
pass a before and after storm event, observations should be
repeated every 2 d over at least an 8-10 d period. Sameoto
(1975, 1978) found that zooplankton variability was similar
over a broad aréa of the Scotian Shelf so that an accurate
and éfficient estimate of population means could be made by
taking 2 net samples 6 h apart at a fixed station.

Our basic field strategy is to locate and characterize a
population of larvae and their prey, and then to compare and
contrast their fine- to micro-scale distribution within stra-
tified and well-mixed waters on Georges Bank. Previous ex-
perience from the 1978 Larval Herring Patch Study indicated
that relatively coherent and stable patches of larvae and
zaoplankton could be defined with conventional sampling ‘tech-
niques. ‘(bongo-net samples) and followed for a number of days
to weeks at a spatial Scale somewhat greater than the tidal ‘
excursion (>5 miles or >10 km). It was assumed for sampling
purposes that variability within the tidal regime was similar
as mixing processes dominate on this scale. Also, by fol- —
lowing a drogueTM for station time-series observations, one
assumed the same parcel of water was being sampled with the


FREQUENCY

5 a

78
65

5a

45

35

32

25

136°

HADDOCK

DAY 7

58% SURVIVAL
38 PREY/LITER
Xe93. 6425.6

n L 1

1 : - 1 1 i
XY 8 8 8 8 & 8 8
LARVAL - WEIGHT (ug)
‘histogram, of- the; wei ght distribution from a 3 : “1

hasti¢c.element.-model: run- ata: prey. density: of 30 literTM
“for haddock larvae at..7 days: after. hatching. -



DAYS

n
VAN 6

bats 4

[ n,

3-6!
oays'~4

J
i}
i}
'
1
!
|
|
I
1
'
1
I
|
1
1
1
1
1
i}
1
1
'
l
|
'
1
(
'
1
1
1
1
1
i)
' 2
1 DAYS
1
.

JUNE 30

23

GENERAL SCHEDULE
HADDOCK PROCESS-ORIENTED LARVAL SURVIVAL STUDIES

IDENTIFY AND LOCATE
REMOTE SENSING -- BROAD SCALE MARMAP SURVEY
1, TEMPERATURE PROFILING FOR THERMOCLINE LOCATION
2. STANDARD ZOOPLANKTON AND LARVAL SAMPLING
3. CHLOROPHYLL SAMPLING AND ENUMERATION

v
PORT CALL - DISEMBARK/EMBARK

v

ALTERNATING PROCESS ORIENTED STUDIES (3 WEEKS)

INTENSIVE 3-D GRID SAMPLING
(25x25 MILE, 5 MILE/STATION)

1. ESTABLISH PHYTOPLANKTON PRESENCE USING TOWED FLUOROMETRY,
IDENTIFICATION AND ENUMERATION

2. ZOOPLANKTON SAMPLING - TOWED PARTICLE COUNTERS (LHPR, BATFISH,
UOR) AND FINE MESH NETS

3, LARVAL PATCH DELINEATION WITH BONGOS, MOCNESS, MILLER, OPENING
AND CLOSING DEVICES
4. PHYSICAL OBSERVATIONS

SELECTED STATION STUDIES

1, VERTICAL PROFILING OF PHYTOPLANKTON WITH “IN SITU" FLUOROMETER.
SPECIES IDENTIFICATION AND ENUMERATION FROM BATCH SAMPLING.

2. FINE-SCALE COPEPOD DISTRIBUTION SAMPLING (NISKIN, PUMPING
SYSTEMS, PARTICLE COUNTERS) FOR PATCH VERIFICATION

3. MICROSCALE PHYSICAL OCEANOGRAPHIC STUDIES WITH FINE-SCALE
TEMPERATURE SENSORS TO CORRELATE WITH BIOLOGICAL PATCHES

4, CONTINUATION OF LARVAL HADDOCK SAMPLING FOR DENSITY AND
DISTRIBUTION

5. SHIPBOARD BIOASSAY GRAZING STUDIES OF COPEPODS ON PHYTOPLANKTON
AND LARVAL HADDOCK ON COPEPODS TO ESTABLISH AND CONFIRM TROPHIC

LINKAGES
¥

[[ Port caLt - DISEMBARK/EMBARK |

¥

— — ~ — }REPEAT ABOVE SCHEDULE 2 MORE TIMES |

IMMEDIATE OUTPUTS

1. RELATE TO: a) FALL JUVENILE SURVEY RESULTS, b) "IN SITU"
ENVIRONMENTAL CHAMBER RESULTS, c) LABORATORY STUDIES

2. FORMULATE NEW TESTABLE HYPOTHESES AND STUDY MORE COMPLICATED
RELATIONSHIPS OR CRITICALLY IDENTIFIED MECHANISMS IN ENSUING
YEARS



55

MOCNESS 191

START FINISH
2t MAY 1981 22: S40 47 21 MAY 1961 23: 56218
42 S5.10N 67 16.950 4@S4,85N 67 15.53%
BOTTOM DEPTH 7e~ BOTTOM DEPTH @gM
TEMPERATURE (°C)
2 = Ww a as
s T T a T
1g
E DEPTH TEMP
at 2 07
1 26
E 2. &e
=r 32 3
3 E we SF
"19 —NET + we S39
Ef w 59
E 7e $8
z= =r NET 3
a fF
WwW
Oo wr NET 2
7er —NET I
E
ae
oe
t
rash

Fig. 3. Real-time temperature-depth plot of 1:m MOCNESS
haul 191. A solid temperature line is drawn as net is set
to maximum depth and dotted after first net is opened and
sampling sequence begins.

depth levels in the upper 50 m of water for 10 min each
depth to filter 1 m3 of water. Since the 1982 season, a
larger submersible pump has been used to filter l m3 of
water in l min. :

CTD-fluorometer

A Neil Brown CTD micro-profiling system with a General
Oceanics Niskin bottle rosette is used for rapid continuous
profiling of temperature and salinity with depth. The water


92

The following points serve as interim conclusions in this
continuing research:

1. Starvation mortality is undoubtedly one of the largest, if not
the largest, components of total mortality in the early life stages.

2. Starvation mortality is most significant in the first 2-3 weeks
after hatching.

3. Haddock are considerably more food limited than cod.
4. However, starvation mortality does not appear to be population

limiting or the single controlling mortality factor under the normal
range of prey densities.


114:

ABBREVIATED FLOW CHART OF STOCHASTIC MODEL

ce LOOP COUNTER # INITIAL LARVAE

INITIALIZE CONSTANT OR STOCHASTIC PREY DENSITY

m’

i

SUBROUTINE: STOCHASTIC INITIAL SIZE RANGE OF LARVAE

t

LOOP COUNTER TIME OR LARVAL WEIGHT INTERVAL

iy

IE: :
METABOLISM UTILIZATION COEFFICIENT, BReME RRED PREY’ SIZE,

SUBROUT! TN CALCULATE LARVAL PARAMETERS: SIZE,

EARCHING CAPACITY, SWALLOWING "PROBABILITY, MINIMUM
WEIGHT BARRIER

i

SUBROUTINE: STOCHASTIC PREY. S75 SELECTION ABOUT PREFERRED

PREYS.

i

SUBROUTINE: STOCHASTIC PREY ENCOUNTER

CALCULATE, RATION. SIZE, GROWTH AND COMPARE WITH
MINIMUM WEIGHT BARRIER FOR SURVIVAL ESTIMA

i

NEXT COUNT

’

ARRAY STORAGE AND PRINTOUT

NEXT COUNT

Figure 8.

An abbreviated flow chart of the basic 4 element stochastic
computer model.


33

Table 9. Larval haddock daily feeding requirements and calculation parameters.
Larval Haddock Std. Length (mm)

Parameter 5 10 15

Dry Wgt (ug) 59.2 1316.0 8084.2

4 G 6% day! (yg) 3.6 79.0 485.0

4 G 2% day-! (ug) 1.2 26.3 161.7

Daily Metabolism - Upper

Limit (y202) 41.4 347.6 1203.3

Daily Metabolism - Lower

Limit (202) 18.3 152.8 529.4

B 0.290 0.769 0.800

w - Preferred Prey

Size (ug) 1.0 7.9 23.0

Range of R, # of Prey

Ingested day-!, Calculated

from Eq. 3 with Upper and

Lower Values of above

Parameters 107-248 47-111 57-143



75

(192), 21 May, made in the well-stratified waters showed a
peak concentration of c. 50 prey/l for the <0.19 mm prey
size class at 10-20 m depth where the thermocline layer
resided, as well as the peak concentration of both haddock
and cod larvae. A range of 5-25 prey/l was observed at
other strata sampled. During 22-24 May, the storm

which mixed the water column, also throughly redistributed
the zooplankton. The important size class of prey now were
uniformly distributed from top to bottom with a range of
5-10 prey/L. On the shoal, well-mixed station, 27 May
(Fig. 15B), the <0.19. mm size class of prey ranged from 12-
25 prey/l with peak densities between 15 and 30 m depth.
The weighted mean depth of larvae at this station was
between 20 and 30 m.

Probabilistic larval prey encounter models, similar to
that developed by Beyer and Laurence (1980, 1981), are being
used to assess the degree of food limitation on Georges Bank.
The most recent empirical results from laboratory experiments
and field studies have been incorporated into the model and
preliminary simulation runs provide some interesting contrasts
in the survival capabilities of larval haddock and cod. One
model run (Laurence, 1983) shows that haddock larvae need
20 prey/il for minimal survival, and about 50 prey/l for 50%
survival through 42 days. On the other hand, cod larvae only
require about 5 prey/k for minimal survival, and 20. prey/l
for 50% survival. These kinds of relatively high prey den-
sities for larval survival have been observed in the Georges
Bank area for the first time. Our field methods and modeling
techniques now appear sufficiently sophisticated to produce
an accurate picture of the environment in which the larvae
grow and survive. Although haddock larvae hatch at a some-
what larger size than cod and remain larger, cod are more
efficient behaviorally and metabolically and consequently,
require lower prey densities for the same percentage survival.
Cod larvae appear to be more adapted as a winter species when
prey densities are generally lower. Haddock larvae, more


1
di
Figure 4. Haddock larval distributions from April and May 1981 grid.
surveys. Densities contoured by factor level of 4

Figure 5. Cod Tarval- distributions from April. and May" 1981 . “grid
surveys. Densities contoured by factor level of 4.

Figure 6. Haddock and cod egg and. Jarval . distributions “sede tae from
. _ the April and May 1981 grid surveys.

Figure th Length- frequency distributions of haddock ° larvae “collected on
the April and May 1981 grid surveys. .

Figure 8. ength- Frequency. distributions of. cod ‘\arvae collected on the
Figure 9. distribution of cod larvae and gadid-eggs collected

% 1 mzMOCNESS (333 wm'mesh) on the. southeast part of Georges
Bank (are 20'N 66°53'W), 25-29 April 1981.

Figure 10. Verticat distribution of haddock larvae on (A) stratified
> .2 +: Station’ (40°55'N 67°16'W) before and after storm, 22-24 May
981;.-and on: (B) shoal, well-mixed station (41°07'N 67°35'W),
27-29. May. 1981. : :

Figure-11.. Vertical ‘distribution of cod larvae on (A) stratified station
(40°55'N 67°16'H) before and after storm, 22-24 May 1981, and
on (8). shoal, well-mixed station (41°07°N 67°38'W), 27-29 May

5 1981.

12. Waters column density (sigma-t) profiles. on stratified station
** (40°55"N- 67°16'W) before and after storm, 22-24 May 1981.
Corresponding MOCNESS haul numbers shown.

3 Preferred prey. size of larval haddock and cod. length ‘groups
‘from May 1980 Georges Bank study (Kane, in press).

Figure 14. Vertical distribution of larval prey field collected by 1/4 m
- MOCNESS (64 ym mesh) on the southeast. part of Georges. Bank,
‘28° April. 1981,

Figure 15. Vertical distribution of larval prey field on (A) stratified
., Station before and after storm, 22-24 May 1981, and on (B) .
. shoal well-mixed station, ;27 May 1981.. ne

Figure. 16. “RNA/ONA ratio. values- versus: size..of individual: -cod and:
haddockJarvae (denoted by station), collected: during April-—
May 1981 on Seorges Bank.



LIST OF TABLES ....... Peace eee eceereeveeeee deen eee een e ee eeesenenee ix

LIST OF FIGURES ...... hee ese recneenceccenceacanes Oe cece neccncnenas xi
“NUTRITION AND TROPHODYNAMICS OF LARVAL FISH - REVIEW, CONCEPTS
STRATEGIC RECOMMENDATIONS AND OPINIONS °...-.+scsssseseeeeeeeee 1
Introduction ....eseceeeeeseeees ee . sete eeeenenes tee seecensnceens 1
State of Knowledge and Review ........cececeeeeenseee seveeveevene 1
Concepts, Strategies and Recommendations ........csecscecesceacee 4
A Concept .......eseeee se eeeeeeeeeeee Pence sence cence ee wees 4
Strategy Relating Larval Trophodynamics to Applied
Fishery Management ....... dee e eee eeneeeeenee sence eee eee neee 5
Sampling Rationale and Strategy for Field Verification -
Georges Bank Haddock as an Example ......isseeeeeeee ae
Quantitative Rationale ......... cece cece cece eee e cess eee 6
Constant, Variable and Parameter Definitions ..........6. 6
Miscellaneous ............ fae ee reece eer eseerenseeseccees 7
Larval Haddock Feeding Requirements ......... see ereeceeee 8
Larval Haddock Swimming Abilities and Searching
Behavior ....ccsececesceseceseeesee tebe eeceeneee seseeeeee 8
Larval Haddock Food Encounter ...... tbe eeneeceeees seseeee 8
Sampling Strategy ..... Seven eeerececeees tee eeeeccecneeeee 9
Opinions - Two Persistent Problems .............eeee seen eeeenees 10
Literature Cited ...........ee0 obec ce eeesecenne eda eeeeececccnes 12
Appendix ........0- bee e eee n ee seeees bene ee ee een enes eee eeeeecee vee 19
~ LARVAL FISH TROPHODYNAMIC STUDIES ON EORGES BANK. SAMPLING
“STRATEGY AND INITIAL RESULTS 77 Lhe soe eenececccene 43
Abstract ........ een e ence eee e enn eeeeseeneeeeeeeeees ese cecncncene 43

Introduction .....

Target Species

an

| Pceding Page Blank


138

ee Le

FREQUENCY

HADDOCK

DAY 21

37% SURVIVAL
38 PREY/LITER
Re2e6. 64148. 7

78
65 +

4a +
35 +

25 Fr

we

a & §° 8 3 8 g g 8

LARVAL WEIGHT (ug)

925 F

Figure 32, . Frequency -histogram of the weight distribution from a 3

“stochastic .element, model run at a-prey density of 30 liter
ddock, larvae at 21 days after hatching.

-1



30

Table 6. Searching ability of larval fishes. (Table XIII from Blaxter, 1969).

Volume Searched during Feeding

Volume
_ " Size searched
.. Species (mm) (liter/hr) Author
Coregonus wartmanni (?)10 14.6  Braum (1964)
: (wnitefisn)
Clupea harengus 8-16 0.3-2.0 Blaxter (1966), Blaxter and Staines
(herring) (1969a)
Clupea harengus 10 1.5-2 Rosenthal and Hempel (1968)
(herring) 13-14 6-8
Sardina pilchardus 5-7 0.1-0.2 Blaxter and Staines (1969a)
({pilchard)
Pleuronectes platessa 6-10 0.1-1.8 Blaxter and Staines (1969a)



FREQUENCY

40

30

10 f

149

8

- HADDOCK. _ .
INITIAL WEIGHTS 7
2 Xe67..549, 3,
sew bes DAILY. VARYING*PREY DENSITY
UNIFORM DISTRIBUTION: 1 TO 50/

er) a ee
LARVAL WEIGHT (ug)

“Figure’ 43. Frequency histogram of the distribution of initial weights of
. vothe entire: Population - for: the* puns S“depicted in-Figures 41 and

100



61

41°30'N

41°00! F

‘THAOOOCK LARVAE,
. Na./10M2

; 16-18 APRIL 1981
ot 618333

WY

230" S
41°30'N 26"

41°00'
/” [waodock LARVAE
poset” NOL 1OM2
19-21 MAY 1981
b~ a 618333
L aa
Fig. 4. Haddock larval distributions from April and May 1981

grid surveys. Densities contoured by factor level of 4.


70

A) STRATIFIED STATION

2t May 1981 MOC 1ST 24-26 MAY 1981 MOC 193-207 28 MAY 1981 MOC 220
NO:/100 MF No./100M> NO. /100M5
ott € 810 QO 0 S OS 10S 2 66 4 2 0
to gh -O4Y J ONIGHT. 4 .
20 20 20
g 30 e 30
§
= 40 40
§ 50 50
60 60
10/10M2 6t/10M? 410m?
70 .
sol 80 80
B) WELL-MIXED STATION GAODUS MORHUA
27-29 MAY 1981 MOC 209-224 GEORGES BANK
0.1008 MOCNESS - {M

6 # 2 0 2-4-6 8 10

ie)
10
20
30
40
50

@ SINGLE OBS
4 WEIGHTED MEAN DEPTH =

DEPTH (m)

15710M= 43/10M?

Fig. ll. Vertical distribution of cod larvae on (A) strati-
fied station (40°55'N 67°16'W) before and after.storm, 22-
24 May 1981, and.on (B) shoal, well-mixed station (41907'N
67935'W), 27-29 May 1981.

of Georges Bank, found that 84% of the larval population
occurred. within the discontinuity layer, the confines of a
thermocline, which occupied about 25% of the water column.

A shoal-water station (50 m bottom depth) was occupied
for 25 h, 27-29 May, where. the water column was well-mixed,
8-99C. Haddock and cod larvae were. broadly distributed
through the water column with weighted mean depths between
20 and 30m (Figs. 10 and 118). There was no significant
difference between their day and night vertical distribution.


(PB85220098
f Cie

» weve,

NOAA Technical Memorandum NMFS-F/NEC-36

This TM series is used for documentation and timely communication of
preliminary results, interim reports, or special purpose information, and

has not received complete formal review, editorial control, or detailed
editing.

Growth and Survival of Larval Fishes
in Relation to the Trophodynamics
of Georges Bank Cod and Haddock

Geoffrey C. Laurence’ and R. Gregory Lough?

1‘ Narragansett Lab., National Marine Fisheries Serv., Narragansett, Rl 02882
2Woods Hole Lab., National Marine Fisheries Serv., Woods Hole, MA 02543

U.S. DEPARTMENT OF COMMERCE
Malcolm Baldridge, Secretary

National Oceanic and Atmospheric Administration
Anthony J. Calio, Acting Administrator

National Marine Fisheries Service
William G. Gordon, Assistant Administrator for Fisheries

Northeast Fisheries Center
Woods Hole, Massachusetts

January 1985

REPRODUCED BY: ‘

, Department of Commerce
National Technical Information Service
‘Springfield, Virginia 22164,

No a



16.7
16.8
16.9
16.9
17.0
17.0
17.1
17,2
17.2
17.3
17.4
17.4
17.5
17.5
17.6
17.6
17.7
17.8
17.8
17.9
17.9
18.0
18.0
18.1
18.1
18.2
18.2
18.3
18.3
18.4
18.4
18.5
18.5
18.6
18.6
18.7
18.7
18.8
18.8

ROBa RL OUBL eS RODUNbLONUODH

RRNRRNN EH HK SSSSOO OOOH YNF AU

PRERERERERERER)
PUDH ENE ow nUD

6200
6300
6400
6500
6600
6700
6800
6900
7000
7100
7200
7300
7400
7500
7600
7700
7800
7900
8000
8100
8200
8300
8400
8500
8600
8700
8800
8900
9000
9100
9200
9300
9400
9500
9600
9700
9800
9900
10000

50

100
150
200
250
300
350
400
450
500
600
700
800
900
1000
1100
1200
1300
1400
1500
1600
1700
1800
1900
2000
2100
2200
2300
2400
2500
2600
2700
2800
2900

400.0

232.0

96

122.76 208.6 +80
124.33 211.2 ~80
125.89 213.8 +80
127.44 216.4 +80
128.98 219.0 +80
130.52 221.5 80 4
132.06 224.1 ~80 4
133.59 226.6 +80 5
135.11 229.2 +80 5
136.63 231.7 80 5
138.15 234.2 80 5
139,66 236.7 +80 5
141.16 239.3 +80 5
142.66 241.8 «80 5
144.16 244.3 «80 5
145.65 246.7 80 5
147.13 249.2 «80 6
148.61 251.7 «80 6
150.09 254.2 «80 6
151.56 256.6 ~80 6
153.03 259.1 +80 6
154.49 261.5 «80 6
195.95 264.0 +80 6
157.41 266.4 +80 6
158.86 268.8 +80 6
160.30 271.2 +80 ZT
161.75 273.6 «80 J
163.18 276.1 80 a7
164.62 278.5 ~80 a7
166.05 280.8 -80 a
167.48 283.2 80 7
168.90 285.6 +80 7
170.32 288.0 «80 7
171.74 290.4 80 7
173,15 292.7 +80 7
174,56 295.1 80 8
175.96 297.4 80 8
177.36 299.8 «80 8
178.76 302.1 +80 8
8% Growth
1.69 5.0 32 26.7
2.57 6.8 34 23.2
3.43 8.5 +36 21.0
5.09 11.7 «40 18.2
6.68 14.6 44 16.4
8.20 17,3 48 15.1
9.69 20.0 51 14,2
11,13 22.5 53 13.4
12,54 24.9 56 12.9
13.91 27.3 +58 12.4
15.26 29.6 +60 12.0
17.90 34.1 64 11.4
20.44 38.5 67 10.9
22.93 42.7 69 10.6
25.35 46.7 71 10.4
27.71 50.7 73 10,3
30.03 54.6 74 10.1
32.31 58.4 75 10.1
34.55 62.2 76 10.0
36.76 65.8 7 10.0
38.93 69.5 a7 10.0
41.07 73.0 78 10.0
43.18 76.5 78 10.0
45.26 80.0 79 10,0
47,33 83.4 79 10.0
49.36 86.8 79 10.0
51.38 90.1 79 10.0
53.37 93.5 78 10.1
$5.35 96.7 79 10.1
$7.31 100.0 80 10.1
59.24 103.2 80 10.2
61.17 106.4 +80 10.2
63.07 109.5 «80 10.2
64.96 112.7 80 10,3
66.83 115.8 +80 10.3


FREQUENCY

18

168

14

12

18

119

COD ~ 258ug

PREFERRED PREY = 8.2

PREY WEIGHT (UG)

Figure 13. Frequency histogram of the distribution of prey size about
the preferred prey size for a 250 ug cod larva.



147

s
at
; eee X1109, 7833, 9
: DAILY VARYING PREY DENSITY
ee UNIFORM DISTRIBUTION: 1 TO 50/2
> 3 *
oO i
2 :
ja
=} ;
o :
aw :
i i
a 2+ -

1000
soo

LARVAL WEIGHT (ug)

Frequency histogram of the distribution of weights of
surviving-haddock. larvae’ on’ day -42 from the.4 stochastic
element model with a daily varying prey ‘density.





14.0
14,1
14.2
14.3
14.4
14.5
14.6
14,7
14.8
14.9
15.0
15.1
15.2
18.3
15.4
15.5
15.5
15.6
15.7
15.8
15.9
15.9
16.0
16.1
16.2
16.2
16.3
16.4
16.5
16.5
16.6
16.7
16.7
16.8
16.9
16.9
17.0
17.0
W.1
17.2
17.2
17.3
17.4
17.4
17.5
17.8
17.6
17.6
17.7
17.8
17.8
17.9
17.9
18.0
18.0
18.1
18.1
18.2
18.2
18.3
18.3
18.4
18.4
18.5
18.5
18.6
18.6
18.7
18.7
18.8
18.8

aon
oon

3000
3100
3200
3300
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
4600
4700
4800
4900
5000
5100
5200
5300
5400
5500
5600
5700
4800
5900
6000
6100
6200
6300
6400
6500
6600
6700
6800
6900
7000
7100
7200
7300
7400
7500
7600
7700
7800
7900
8000
8100
8200
8300
8400
8500
8600
8700
8800
8900
9000
9100
9200
9300
9400
9500
9600
9700
9800
3290
10000

$0
100

240.0

312.0

408.0

496.0

$36.0

640.0

664.0

744.0
760.0

792.0
800.0

wee

118.8 10.3
121.9 10.4
124.9 10.4
128.0 10.4
131.0 10.5
133.9 10.5
136.9 10.6
139.8 10.6
142.7 10.6
145.6 10.7
148.5 10.7
151.4 10,7
154.3 10.8
157.1 10.8
159.9 10.8
162.7 10.9
165.5 10.9
168.3 10.9
11.1 10.9
173.8 11.0
176.6 11.0
179.3 11.0
182.0 ll
184.7 Ml
187.4 M1
190.1 Ml
192.8 11.2
195.4 11.2
198.1 11.2
200.7 11.3
203.4 11.3
206.0 11.3
208.6
211.2
213.8
216.4
219.0
221.5
224.1
226.6
229.2
231.7
234.2
236.7
239.3
241.8
244.3
246.7
249.2
251.7
254.2
256.6
259.1
261.5
264.0
266.4 11.9
268.8 11.9
271.2 11.9
273.6 11.9
276.1 12,0
278.5 12.0
280.8 12.0
283.2 12.0
285.6 12.0
288.0 12.1
290.4 12.1
292.7 12.1
295.1 12.1
297.4 12.1
299.8 12.2
302.1 12.2
12.5% Growth
1.69 5.0 +32 33.3
2.57 6.8 +34 29.3
3.43 8.5 136 26.7


18

Theilacker, G. and K. Dorsey. 1980. Larval fish diversity, a summary of
laboratory and field research. Intergov. Ocean. Comm. Workshop
Rept. No. 28, 105-142.

Toetz, D. W. 1966. The change from endogenous to exogenous sources of energy
in bluegill sunfish larvae. Invest. Indiana Lakes and Streams, 7:115-146.

Vlymen, W. J.. 1974. Swimming energetics of the larval .anchovy, Engraulis .
mordax. -Fish. Bull.,U.S., 72:885-899.

- 1977.. A mathematical model of the relationship between larval
anchovy (E. mordax), growth, prey microdistribution and Jarval behavior.
Environ. Biol. Fishes, 2:211-233.

Webb, P: W. and R. T. Corolla. Ms. Burst. swimming performance of anchovy
larvae, Engraulis mordax. Southwest Fisheries Center, P.0. Box 271,
La Jolla, CA 92038.

‘Werner, R. G. and.J. H. S. Blaxter. 1981. The effect of prey density on
mortality, growth and food consumption in larval herring (Clupea harengus L.).
Rapp. P.-v. Reun. Cons. int. Explor. Mer, 178:405.

Wyatt, T. 1972. Some effects of food density on the growth and behavior
of plaice larvae. Mar. Biol., 14:210-216.

Yokota, T., M. Toriyama, F. Kanai and S$. Nomura. 1961. Studies on the
feeding habit of fish. Rep. Naukai Reg. Fish. Res. Lab. 14, 243 p.
(in Japanese, English summary).


77

2 coo STA. xX

16- APRIL 1981 *- B17 S.24
16+ N = 6a o- 628 6.36
° «x - B39 6.12
z Mr . * = MIS8 7.77
= 12h . - MI66 6.3
<= 8b
& ae r+} > -
= aw, bead +> . .
2 48 See. 2
4b Ord me. t .
2e
“a 2 $ i
ORY WT (MG)
ae HADDOCK STA. x
L *- MIST 6.64
ve MAY 198T o- M205 867.99
ep Nw Lid x - M2LI-0 7.44
= ut o +-M211-8 7.62
= 12 ~- M215 7.24
s We x, a
a $cte
S ar % = x e ~ °
2 st = x Be Seu x to x
4b x “
2k . +
a t z 5 4
ORY WT (MG)

Fig. 16. RNA/DNA ratio values versus size of individual cod
and haddock larvae (denoted by station) collected during
April-May 1981 on Georges Bank.


72

haddock and cod show that the naupliar and copepodite
stages of Pseudocalanus and Calanus are their most important
prey (Sherman et al., 1981; Kane, in press). Eggs of these
two species can sometimes comprise a significant number of
prey items for the smallest larvae (<6 mm), especially for
the more passively feeding haddock larvae. The preferred
prey size of four length groups of larvae is depicted in
Fig. 13. Note that cod feed upon larger prey at a smaller
size than haddock. Both species of larvae (<10 mm) select
50-80% of their prey in the 0.10-0.19 mm width class. Re-
cently-hatched larvae, 3.5-5.9 mm, are particularly depen-
dent on this size class of prey which encompasses the nau-
plius III through copepodite II stages of Pseudocalanus and
the nauplius II-v stages of calanus.

HADDOCK cop
1

PREY ORGANISMS (%)

2533 3333
hoc T topo

3828 3338
LENGTH GROUP (MM)

PREY WIDTH _[MM)|

AI0-O45
| 20-0.29
0.10 -A19
_}201-0.09°

_ Fig. 13. Preferréd prey size of larval haddock and cod
length groups. from May 1980 Georges Bank study (Kane, in press) -


xvi

Figure 44, A. graphic illustration of the parameters and calculations
° involved in assessing food limitation and impact on prey for
larval - gadids on Georges Bank.

at



42

NO. COPEPODS/M3

G9 2 4 6 8 18 12 14 16 18 2G

i T T T T T 7

€

i — PSEUBOECALANUS

\ 7 CALANUS

1Ge
pam
i
fi 20-
Q

36-

MOC 326

Figure 7. Vertical distribution of dominant copepods on Georges Bank.
(Albatross 82-05, May 15, 1982, 1831-1844 D.S.T. MOCNESS-1
m, O.333 mesh, 41°14'N, 67°37'W. Bottom depth: 36m). No
gadoid larvae present. Temperature 6.7°C isothermal.


84

INTRODUCTION

This report documents the evolution and development of stochastic
models simulating the processes associated with: feeding, growth and
survival of larval cod and haddock both as individuals and
populations. The predecessors to this research were an initial
deterministic energetic model approach by Laurence (1977) and subsequent
stochastic models by Beyer and Laurence (1980, 1981). This exercise is
an extension of the Beyer and Laurence model (1981) with the addition of
more stochastic elements: because of -new empirical information now
available for both species. Data sources used are principally from
published and unpublished. studies conducted in the Marine Ecosystems
Division of the National Marine Fisheries Service, Northeast Fisheries
Center, although all available sources from the published literature
were used when applicable. The ultimate goal of the modelling is to
assess aspects of food-limited larval starvation and predation pressure
of the larvae on their food sources in the Georges Bank spawning and
nursery areas.

BASIC DETERMINISTIC ELEMENTS

Interconversion between length and weight are given from the
research of Laurence (1978a) as:

L = 1,935 wo-247 (1) for cod
and
L = 2.026w0-222 (1a) for haddock

where L = standard length in mm and W = dry weight in ug.

Metabolism was derived from empirical laboratory respirometer
measurements (Laurence, 1978b). Coefficients from that research were
adjusted for active periods in daylight and resting periods in darkness
and prorated over 24 hours with 13 light - 11 dark for cod and 14
light - 10 dark for haddock corresponding to the amount of ambient light
at the peak of larval abundance for each species. Equations for daily
metabolism (Fig. 1) are:

M = 24 (0.010 w0-775) (2) for cod
and
M = 24 (0.038 w0-684) (2a) for haddock

where M = metabolism in ug day-! (1 u209 = 1 ug larval tissue by caloric
conversion), W = weight in ug.


63

67°30’ 67°00" 66°30'W

16718 APRIL,

41°30'N

41900 F

/”” | HADDOCK EGGS & LARVAE
: pric | GENERALIZED,
aw oD i ISTRIBUTION
gm + ° NO./10M2
402 SPRING 1981
—_ 2 =

41°30'N

41°00! F

Lp a
erence” | COD EGGS @ LARVAE
vm uot’ | GENERALIZED
i DISTRIBUTION
ie NO./10M2
182 SPRING 1981

L Hn

Fig. 6. Haddock and cod egg and larval distributions
generalized from the April and May 1981 grid surveys.


24

Table 1. Species specific early life history parameters. (Table 1 from Theilacker and Dorsey, 1980.)

Spawning season Incubat ion Hatching
Species Range (peak) ye days c Tzemm dry wt vg
Limanda Gulf of St. March-Aug, Pelagic 0.88 5-7 19 2.03.5 16
ferruginea Lawrence to 0.79-1.01
TelTowtan Virginia
Flounder) lL
Limanda North Sea March-June. Pelagic 2.6
Tinands’ English (Feb.-April) 0.85-0.95
~Theby 2. Channel
Pleuronectes North Sea Mec.=Apr‘} Pelagic 2.0 1B Ta 5.06.7 151
atessa English Channel 1.7-2.2
Sereteey 3. to Norwegtan
Rinne Skagarrate
Pseudo- Northern Nec. -May Nemersal 9,80 17-25 3 2.3-3.5 10-30
pleuronectes Labrador to 0.71-0.96 ’
americanus Georgia
Winter —
flounder)
Paralichthys Maine to Oct .-April Pelagic 1.04 3 i 2.4-2.8
jentatus Florida 0,90-1,13
‘anne
flounder) 5.
Solea solea North Sea April-June Pelagic 8 10-12 3.2-3.7
Sole f. English Channel 1.0-1.5
Achirus Florida and Pelagic 1 28 21.8
Tneatus Gulf of Mexico
Tined sole) 7. to Uruguay
Stenotomus Nova Scotia May-July Pelagic 0.94 15 2 2.0
““chrysops to Eastern 0,85-1.15
Tomy a, Florida
Archosargus New Jersey Sept.-May Pelagic 1 26 1.8-3.2 27.8
“Thombetdalis to’ Rlo de
Seabrean) 9, Janeiro
Gadus morhua North Rec. April Pelagic 1.52 12 5.5 3,365.7
Tod} - Atlantic 1,10-1.72
10. Coastal
Waters
Melanograrmus North Atlantic Feb, -June Pelagic 1.46 v 5.5 2.68.1
aeglefinus : Biscay to 1,10-1.67
Raddock ‘Barents Sea
Newfound)ané
11. to Cape Cod
Clupea Greenland-Cape July-Nov.; May Remersal 1.0-1.4 15 (Maine, 8 4,010.0 90
Wiengus Hatteras (Sept. & May) 0.36-3.9 Downs) (50-220)
ttantTe Iceland-
herring) 12, Gibraltar
Sardinops Southern Feb.-July Pelagic M7 2.8 15 3.75 36
sagax Alaska to (May-June)
act tic Gulf of
sardine) 13, California
Engraulis Northern Raja dan.-July Pelagic 0,66-1,35 2-3 16 2.9-3.2 a.
coat California to (March-May)
Northern: ‘ Arctic Alaska
anchovy), 14. and Japan
Engrautis Coasts of | duly-March Pelagic 0,711.42 202.28 16 2.19-2,72
ringens . Peru-and (Sept. & Fed.) .
Thehoveta) 15. chive
Sconber Southeast April -August Pelagic 3.6 16 3.1 49
aponicus Alaska to (May-duly) > - 1.06-1,14
SST Banderas Bay,
mackere)) 16. Mexico - -
Trachurus Magdalena Bay, Feb.-August Pelagic 1.0, 23 6 2s ae
‘Symmetricus Baja Cali- (May-June) 0.90-1.02 2.8
facl a fornia to .

mackerel) 17, Southeast
Alaska



b-Z seTqe, 0} razor sseaTd seureu oTztoeds TInz 120g *Aerd Jo yAPTM 02 YWhHom

TeAzeT JO YIPTA Jo dtysuotzeyeu “snosny snzeqdostzy pue snbueprew sntbuepzew ‘enyxrow snpey *¢ ‘Ohta

Figure 1.

36°

2
T

—
dinoflagellates

€

—
tintinnids

dlatoms

(wu) a0aspy yo yy6uaq
9

——
Lamellibranch tarvae

—
Paracalanus Paracaianus
=, ROUBLE copepodites,

ny
‘Acartia Acartia copepodi
7  nouplii

————___
Pseudocalanus Pseudocalanus
ae AQUI copepodites

—
Temora  Temora copepodites
=) nauplii

a

& 100

Ss

© 200

0 t00

< 100

3 300
90:0

Z

bo
>x
33
33
32
53
a
€
a

.
~
aq
3
5

Relationship of larval and prey sizes.

1978b).

(Figure 3 from Last,


105

Table 3. Relevant larval gadid parameters for Georges Bank (from Smith
et al. 1979, 1981 and Sherman et al. 1983).

Maximum Larval Annual
Year Species 0385 #/m3 ae ata
1974 Cod 157.5 0.05
Haddock 54.1 0.02
1975 Cod 121.8 0.04
Haddock 138.9 0.05
1976 Cod 16.1 0.01
Haddock 76.5 0.03
1977 Cod 459.6 0.15
Haddock 431.6 0.15
1978 Cod 71.1 0.02
Haddock 313.2 0.11
1979 Cod 122.1 0.04 39.1
Haddock 408.3 0.14 64.3
1980 Cod 227.8 0.08 102.8
Haddock 743.8 0.25 110.4
1981 Cod 311.2 0.11
Haddock 405.8 0.14
1982 Cod 10.4 0.093

Haddock 6.5 0.002



41

NO. COPEPODS/M3
1 18 102 1, 92 16, 083

1 1 1 ! 1 1 ! ! |
1 fl ' 1 1 i i 1 1

\ /

PSEUDOCALANUS ——

19 F

28 f a

w
Q
_—

DEPTH (M)
8

.oay
Q
T

6a |

\
| \

74 +

|
\

[|
K

MOC 344
eg b

Figure 6. Vertical distribution of dominant copepods on Georges Bank.
(Albatross 82-05, May 17, 1982, 1830-1920 D.S.T. MOCNESS-1 m,
mm mesh, 40°55! N, 67°17'W. Bottom depth: 75.9 m). No

gadoid larvae present. Temperature Ca. 5-6° C isothermal.


FREQUENCY...

126

oa
~ LARVAL HADDOCK” -
X68. 8418.5

ASF
18}

SE NX
<<

8 2 B 8 ty 8

ORY WEIGHT (ug)

Figure 20. Frequency histogram of a-generated normal distribution of
larval initial hatching weights based on empirical laboratory
measurements for haddock.



37

E, ancharta (Wiea)
. jeponico (shoded)

PREY SIZE, WIDTH OR LENGTH (mm)

Oe s 4 5 6 7 8 9 10
G ‘Scomber spp (bors)
M: merluccius tubes: (live)

LARVAL LENGTH (mm)

Figure 3. Relation between prey size and larval length for 12 species of marine fishes:
label on ordinate indicates whether prey width or prey length were measured; vertical
bars and shaded areas represent range of prey sizes; and straight lines connecting
dots indicate average prey sizes. Plots were redrawn from Arthur (1976) for Sardi-
nops sagax, Engraulis mordar, and Trachurus symmetricus; from Rojas de Mendiola
(1974) for Engraulis ringens; from Detwyler and Houde (1970) for Harengula pensa-
colae and Anchoa mitchilli; from Stepien (1976) for Archasargus rhomboidalis; from
Ciechomski and Weiss (1974) for Engraulis anchoita and Merluccius merluccius; and
from Yokota et al. (1961) for Engraulis japonica, Trachurus japonicus, and Scomber
spp. Data were for sea-cauyht larvae except panel D, which were laboratory reared,

Figure 2. Relationship between prey size and larval size. (Figure 3
from Hunter, 1981).


66

produced egg and larval concentrations nearly identical to
the previous station values (within a factor of 4). -Using
all available information, the haddock and cod egg and larval
concentrations have been generalized in Fig. 6 to show their
size, shape, and dispersal between surveys. The highest con-
centrations of eggs and larvae contoured were elliptical in
shape with major and minor axes of about 30 x 15 miles

(56 x 28 km). The smallest patch resolved is about 10 x 5
miles (19 x 9 km), which is on the scale of the tidal excur-
sions and the sampled grid of stations. The lowest concen-
tration of larvae defined and contoured as a patch was about
60 miles (111 km) long between the shelf/slope-water front
and the tidal front. If one assumes that the patch dimen-
sions are reasonably accurate, an estimate of mortality can
be made between the eggs in April and the larvae in May.
Using methods similar to those described in Lough et al.
(1980), mortality of haddock and cod from their hatching
midpoint through the 6-mm size class (18-24 d post-hatch)
was estimated ta be 6-8%/d. These loss rates are consis—
tent with the range of rates (5-15%/d) reported by Saville
(1956) for Faroe haddock larvae.

It also is of interest to note that the largest and pre-
sumably oldest larvae collected on the grid survey were found
to the extreme southwest and on the shoals (<60 m). This
past May 1983, using the 10 m MOCNESS, relatively high den-
sities (70=450/10 000 m3) of cod post-Larvae (15-50 mm) and
sand eel, Ammodytes sp- (45-80 mm), were collected through-
out the shoaler parts of western Georges Bank, both of which
have been observed to prey upon young fish larvae.

In April, winter conditions still prevailed; the water
column: was ‘weli-mixéd throughout the study area, isothermal
(6°c) from surface to bottom. Only during the final days of
the cruise was’ a slight warming of surface waters observed,
indicating ‘the onset of spring thermal stratification on the
flank of the bank. ‘Net-phytoplankton (>20 um) biomass in-
creased with depth from 1-2 mg chl a/m? near the surface to 5-


76

adapted to spring ‘conditions, require higher prey densities
which appear to be concentrated by spring stratification.
Prey densities tend to be uniformly higher in the shoal,
well-mixed waters, but stratification along the southern
flank of Georges offers. a greater potential for higher than
average prey densities on which an opportunistic species
like haddock ‘can capitalize. The recruitment pattern of
haddock also tends to be a ’boom or bust! type with 3-4 good
years out of 20, whereas cod recruitment tends to be rela-
tively low but with less variation (Hennemuth et al., 1980).

Further evaluation of population growth and survival in
the sea may best be made through a comparison of biochemical
condition indices derived from larvae reared in laboratory
experiments. The RNA/DNA ratios of haddock and cod larvae
collected in spring 1981 are plotted against size in Fig. 16.
A minimum Llaboratory-determined RNA/DNA ratio of 3.2 has been
established for cod, below which starvation and death occur
(Buckley, 1979). However, very few (<2%) of the larvae ana-
lyzed from the field had ratios <4, indicating recent high
population growth rates. Nevertheless, differences in station
mean ratios occur which may be related to short-term varia~
tions in prey density, and may in turn be related to predation
of the slower growing individuals. Perhaps in future simu-
lation studies, population growth rates can be associated
with discrete predation proabilities.

In conclusion, our sampling scheme is similar in many as-
spects to other multidisciplinary studies of larval growth
and survival (Report of the Working Group on Larval Fish
Ecology; 1982), but specifically designed to be carried out
within the spawning season of haddock-cod and the physical
regime of the Georges Bank region. Our sampling strategy
is unique fora single vessel operation in its attempt to
allocate a suitable balance of sampling effort among the
various spatial ana temporal scales needed to estimate the
abundance and distribution of fish larvae, their prey, and
predators in order to achieve the proper integration of


31

Table 7, Growth efficiencies of larval fishes. (Table 9 from Theilacker and Norsey, 198M).

Daily ration

Prey Container Gross
A density volume % body efficiency
°c uy (8/L) (Titers) ug wt (3) Reference
Bay anchovy! 26 50 10 19 3 37 Houde % Schekter 1980
Anchoa mitehilt * 100 0 51 32
. 1000 15 140 4
nauplii
wild
plankton)
Herring = 12-22 6; 14,000- 8 n Eldridge et al. 1977
Clupea harengus pallasi 100-150" ug 20,090 ~
Sea brean! 2 17 4; 200 ug 50 10 12 : 83 Houde & Schekter 1980
Archosargus rhonboidalis * 15 di 200 ug 100 31 42 38
. 10 200 ug 500 45 - 38
nauplii
(utd)
" . 23-26 2-3 4 1900 8 14 68-147 3 Stepien 1976
2 2-3 d 1no0 2 199 16
230 «10d ‘lon - 69 31
Pacific mackerel? 19 3d; 3Rug 157,990 200 27 70 20 Hunter & Kimbrel}
Scomber japonicus "4d; 43 ug 47,000 3a 89 7 1980"
"5 4; 85 ug 198,900 85 192 44
rotifers
Striped bass IR 16d, 400 wy 10 13 Eldridge (unpubl.)
Marona saxatil's " 100 15
7 san 2n
. 1900 a
500 50
Artemia
R294 “Tr 20
" 190 14
* 500 uv
. 1000 19
* 5n0n 32
Artemia
Lined sole 7% 21d; 200 ug 50 10 14 - 63 Moude f Schekter
Achirus lineatus "AT ds 200 ug 100 20 29 52 1980
* 12d; 200 uq loan 4 ~~ 20
nauplii
(witd)
Winter flounder3+4 BR 2 wks. 500 10 Laurence 1977
Pseudopleuronectes americanus @ 7 wks. 20
nauplii-
RB 2 wks. copepods 300 15
8 7 wks. 3000 30 B

Inaity ration estimated from grazing experiments; dry weights determined with preserved larvae; wild plankton nauplii 9.15 ug, fresh dry wt.
2Rration from stomach contents and evacuation rate (discontinuous feeding).
3ration from stomach contents and evacuation rate (active feeding).

‘Net growth efficiencies.


FREQUENCY

18

16

14

12

@

117

COD-MODEL 1

DAY 42
r 188% SURVIVAL

1@ PREY/LITER

X=604141376
L
L
B B B B B R B B
n in no in Tel ite} w wo
“ N m oO wn ao

z rs)
LARVAL WEIGHT (ug)

Figure 11. Frequency histogram of the distribution of larval weights of
survivors at 42 days after hatching. Cod model 1 at 10 prey

liter ~


14.1
14.1
14.2
14.2
14.3
14.3
14.4
14.4
14.5
14.5
14.6
14.6
14.6
14.7
14.7
14.8
14.8
14.9

14.9

50

100
150
200
260
300
350
400
450
500
600
700
800
900
1000
1100
1200
1300
1400
1500
1600
1700
1800
1900
2000
2100
2200
2300
2400
2500
2600
2700
2800
2900

1062.5
1075.0
1087.5
1100.0
1112.5
1125.0
1137.5
1150.0
1162.5
1175.0
1187.5
1200.0
1212.5
1225.0
1237.5
1250.0

SO0000000000000000000050000000

AN GESANDSGANDROANRGSOGASNOBALON

OOVMOUIMADAN EE RWUNNY EEE

101

31.88 358.1 -80 67.3
32.24 362.0 80 67.5
32.61 366.0 80 67.7
32.97 369.9 -80 67.9
33.33 373.7 80 68.1
33.69 377.6 .80 68.3
34.04 381.4 80 68.5
34.40 385.3 80 68.7
34.75 389.1 80 68.8
35.10 392.9 80 69.0
35.45 396.7 -80 69.2
35.80 400.4 80 69.4
36.15 404.2 80 69.6
36.49 407.9 80 69.7
36.83 411.6 -80 69.9
37.18 415.3 +80 70.1
37.52 419.0 -80 70.3
37.86 422.6 80 70.4
38.20 426.3 80 70.6
38.53 429.9 +80 70.8
38.87 433.6 80 70.9
39.20 437.2 80 7
39.54 440.8 -80 71.3
39.87 444.3 80 71.4
40.20 447.9 80 71.6
40.53 541.5 -80 71.8
40.86 455.0 80 71.9
41.18 458.5 +80 72.1
41.51 462.1 +80 72.2
41.83 465.6 -80 72.4
42.16 469.1 -80 72.6
42.48 472.5 80 72.7
42.80 476.0 80 72.9
43.12 479.5 .80 73.0
43.44 482.9 +80 73.2
43.76 486.3 -80 73.3
44.08 489.8 80 73.5
44.39 493.2 -80 73.6
44.71 496.6 80 73.8
4% Growth

72 30 111.5
1.04 32 96.3
1.33 35 86.4
1.88 39 73.5
2.38 43 65.1
2.85 46 59.2
3.30 «50 54.9
3.73 «53 $1.5
4.15 +55 48.8
4.55 58 46.6
4.94 -60 44.8
5.69 +63 42.1
6.40 +66 40.1
7.09 69 38.6
7.75 71 37.6
8.40 73 36.7
9.02 74 36.1
9.63 75 35.6
10.23 76 35.3
10.81 77 35.0
11.38 77 34.8
11.93 78 34.7
12.48 78 34.6
13.02 78 34.5
13.55 79 34.4
14.07 79 34.4
14.58 279 34.4
15.09 +79 34.4
15.59 79 34.5
16.08 -80 34.5
16.57 80 34.5
17,05 -80 34.6
17,53 +80 34.6
18.00 207.9 80 34.7
18.46 212.9 80 34.8



110

(8>) |HOTSA Aud
G6 006 BSB B08 BSL BBL BS9 B49 BSS BBS BSy Boy BSE BoE BSe Boe

BST BAT BS

1]

T T T T T T T T T T T T T

T

T

T

N
1

AVG/SH3LT1

i}

Se

8s

SL

Bat Tel * -ALEL “=S
(tite)

Set

“Daily: visual searching capacity of cod and haddock larvae.

Figure 4.


FREQUENCY

13

12

I

18

115

LARVAL COD - 44 ug
18 PREY/LITRE
Xe20. 744, 2

x a ag S

28

# PREY/DAY

Figure 9. Frequency histograms of the normal ized. distribution of # of
prey of preferred size. consumed day~~ for a newly hatched
44 ug cod larva at a prey density of 10 literTM*.

32


FREQUENCY

139

15
HADDOCK
DAY 28
37% SURVIVAL
38 PREY/LITER
X=446. 84245. 8
18 r
SF
1

: f]. ff]
ge  &

LARVAL WEIGHT (ug)

2488 |
2888

Figure 33. Frequency histogram of the weight distribution from a 3 1
stochastic element model run at a prey density of 30 liter”
for haddock larvae at 28 days after hatching.

3288 +



FREQUENCY

143

2s
HADDOCK
81 SURVIVORS OF 18820
15 PREY/LITER
DAY 42
oa Xe1173, BLAS. 3
s+
aE
i
a l i 1 [

s & &§ —€ & — § & 8 &

LARVAL WEIGHT (ug)

Figure 37. Frequency histogram of the distribution of. weights or larval
haddock survivors on day 42 from a large population run
(10,000 initially) with the 3 stochastic element model at a
prey density of 15 literTM*.



i; —S
| Preceding Page Blank | iii

f
wee FOREWORD

A paramount problem in fisheries science is understanding the
causes of natural variability in fish production and resultant stock
size. This variability is thought to be fixed by the time fishes are
recruited to the fishery and is believed to be determined by factors
influencing survival and growth in the early life stages (egg, larval
and juvenile). These determining factors are both biological and
physical. Predator-prey relationships are the important biological
mechanisms with early life stage success linked to capture of prey
(food) and avoidance of predators. Physical factors directly affect
physiological mechanism and developmental rates as well as the transport
and distribution of the early life stages and their predators and prey.

The Marine Ecosystems Division of the National Marine Fisheries
Service, Northeast Fisheries Center, has been especially cognizant of
the need to understand recruitment variability for potential use in
management strategies. As a result, the Division has focused on
research designed to understand the possible controlling factors
mentioned above. The Larval Dynamics Investigation within the Division
has concentrated its research on the role of food sources and successful
feeding in the larval stage. The three papers of this NOAA Technical
Memorandum (two of which have been presented elsewhere) present a
detailed description of this research. The first paper on nutrition and
trophodynamics explores the present state of knowledge of larval feeding
as it relates to success (growth and survival) or failure (starvation
and death) with special emphasis on experimental research. The second
paper describes the at-sea sampling strategy of process-oriented, multi-
discipline studies of fine and micro-scale distributions of cod and
haddock larvae and prey on Georges Bank in relation to physical
factors. The operational plan, sampling gear & instrumentation, and
special techniques employed are discussed in terms of results and
usefulness of the parameters measured. The third paper documents the
evolution and development of stochastic models simulating processes
associated with feeding, growth, and survival of larval cod and haddock
as individuals and populations. This modelling synthesizes much of the
laboratory experimental and field empirical data bases collected by the
Division.

Interim conclusions from this compendium of continuing research
indicate that starvation mortality in the larval stage is one of the
largest components of total mortality and is most prominent in the first
weeks after hatching. However, its magnitude is such that it does not
appear to be population limiting under most conditions observed in the
field thus far. There is normally enough food in the sea to allow an
ecologically significant portion of larval populations to grow and
survive. Thus, the implication is that predation and/or factors
affecting the juvenile stage may be keys to variable recruitment.

Geoffrey C. Laurence
Narragansett, Rhode Island

January 1985


FREQUENCY

133

2a
cop
DAY 35
27% SURVIVAL
8 PREY/LITER
Xe573. 02561. 2
Is}
ig +
St
a 1 [| i [| L am 1 1 im
2
= & § € § & & §8

LARVAL WEIGHT (ug)

Figure. 27. Frequency histogram of the weight distribution from a 3
stochastic element model run at.a prey density of 6 liter

for cod. larvae at 35 days after hatching.

-1


94

aeglefinus) as influenced by temperature during laboratory
studies. Mar. Biol. 50:1-7.

LAURENCE, G. C., J. R. GREEN, P. FOFONOFF, and B. R. BURNS.
1984.. “Smal - scale spatial variability of plankton on Georges Bank

with-particular. reference to prey organisms of larval cod and
haddock, ICES C.M. 1984/L:9, 10 p.

LOUGH, R. G.

1984.- Larval fish trophodynamic studies on Georges Bank: Sampling
strategy and initial results. In: E. Dahl, D. S. Danielssen, E.
Moksness, and P. Solemdal (Editors), The propagation of cod Gadus.
morhua L. Flgdevigen rapportser. 1(1984):395-434.

PEARRE, S., dre .
1980. The copepod width-weight relation and its utility in food
chain research. Can. J. Zool. 58:1884-1891.

SMITH, W. G., M. PENNINGTON, P. BERRIEN, and J. SIBUNKA.
1979. : Annual changes in the distribution and abundance of Atlantic
cod and haddock larvae off the Northeastern United States between
1973-74 and 1977-78. ICES C.M. 1979/G:47, 9 p.

SMITH, W. G.,P. BERRIEN, D. G. McMILLAN, and A. WELLS.
1981. The distribution, abundance, and production of Atlantic cod
and haddock larvae off Northeastern United States in 1978-79 and
1979-80. ICES C.M. 1981/G:52, 10 p.

STEELE, R..G. D., and-J. H. TORRIE.
1960. Principles and procedures of statistics. McGraw-Hill, New
York, 481 p.


54

MOCNESS | oop Dk
A Multiple Opening/Closing Net. and Environmental Sensing
System .(MOCNESS;.Wiebe et al., 1976; 1982) with three separate
underwater-sampling units (1/4 m, 1m, 10 m) provides us with
wide spectrum capabilities of sampling discrete. vertical stra-

ta encompassing three trophic levels from micro~plankton,
fish Larvae-zooplankton, : to: micro-nektonic organisms.. MOCNESS
is a rectangular sampler whose nine serially linked nets can
be opened and closed sequentially by commands through a con-
ducting cable from the surface vessel, thus permitting sam-
pling of up to nine discrete depth levels or horizontal series
in a single haul. The three underwater samplers are designed
to be hauled at 11/2 knots (78 cm/s), 45° net angle, for an
effective.mouth area of 1/4 m2, 1 m2, and lo m2. Standard
net .mesh size for ‘the underwater units are 64 um, 333 um,

and 3.mm, respectively. On-deck, real-time monitoring in-
cludes depth (pressure), net angle, number of the net pre-
sently filtering water, volume of water filtered, temperature
and chlorophyll fluorescence (Aiken, 1981). Parameter data
are stored on an HP-85 computer system for real-time X+Y¥
plots of temperature and fluorescence vs. depth, which are
useful in selecting sampling depths (see Fig- 3). A North-
star Loran C unit with plotter also is integrated with the
MOCNESS for recording the position at each net release.

Other -sensors..such as salinity, light, and oxygen will be
integrated with MOCNESS.

Plankton. pump::~

In 1981-a:1-hp ‘submersible well pump was used to sample
micro~zooplankton at depth.- The pump is typically deployed ©
attached to 1/4"° (6.4mm) wire with a 45 kg lead ball. De-
livery of water from depth to a deck manifold fitted with
fine-mesh nets (20 and 53 um mesh) is by a 7.5 cm diameter
Pvc discharge hose. Watec is typically pumped. from five


40

NO. COPEPODS / Mm?
10° 10° 10° 10° 10% 10°
f - . 0 1 1 v 1

NO. GADID LARVAE /100 m3
30° 101 102 10°
Pe ~ T 1

TEMPERATURE ( °C )
6) 5 10 15

40; ae

20 —— Calanus

Temperature
30 -

(M)

\
1
j-—-Lorvae

40;- Pseudocolonus —!

50 |-

OEPTH

70 —-

MOC 193

80

Figure 5. Vertical distribution of gadid (haddock and cod) larvae and
dominant copepods (Calanus finmarchicus, Pseudocalanus sp.)
onthe Southeast Part of Georges Bank after storm. (MOCNESS-

.lm;.0.333-mm mesh. 24 May 1981, 1835-1920 D.S.T. 40°55'N,
67°13'W. Bottom depth: 80 m). Note different log-scales used
for copepods and gadid larvae.



89

Figure 11. This type of population simulation is derived by making
repetitive runs for individual larvae like the ones illustrated in
Figure 7 and simply noting sizes and numbers alive at given times.

Version #2 of the model included a second stochastic element which
was varying the size of prey about the preferred prey size. The
procedure was to compute the preferred size from equations (3) and (3a)
through (5) and (5a) and compute a normalized probability distribution
based on a poisson (random) distribution about the preferred size. The
computed distribution was arbitrarily truncated on both ends based on
biological considerations. The upper prey size was truncated at +2
standard errors. If a larvae encountered a prey larger than this it did
not eat the prey since it was too big to handle. The lower end of the
prey size distribution was at a prey size of 0.1 ug. Any encounters of
prey smaller than this were considered to be 0.1 ug and were calculated
to be consumed rather than truncated and not consumed. The rationale
behind this was that there are many more smaller and available prey in
the natural environment than larger so the encounter of numbers of
smaller prey should be greater. Figures 12 through 17 show the
frequency histograms of prey size about the preferred size encountered
by cod and haddock larvae at 3 different body weights.

This model version (#2) with its addition of stochastic prey size
to stochastic prey encounter was more robust and somewhat less
deterministic than model 1. A simulation of survival and size (growth)
for cod similar to Figure 11 is shown in Figure 18. It can be easily
seen that survival and growth has been reduced to more realistic levels
with the addition of stochastic prey size.

The third stochastic element added to the model (version #3) was a
distribution of different initial larval weights at hatching. Until
this version, all larvae started out at the same size. Empirical data
from laboratory studies of known age larvae from known hatching times
and known date spawnings showed the distribution of hatching sizes to be
essentially normal about the mean size. A normal probability
distribution of initial larval sizes +2 standard errors about the mean
size was calculated based on the known empirical mean and standard
errors. Examples of generated frequency distributions for cod and
haddock initial sizes are presented in Figures 19 and 20.

An additional element of model version #3 was a calculated delay of
any weight loss due to unsuccessful food encounter for 3 days after
hatching. This was to compensate for energy available from yolk still
present, and was based on empirical laboratory observations and
experiments.

This model version (#3) proved to be even more robust and
intuitively as well as actually more realistic. Simulations at
different constant prey densities with this #3 stochastic element
version pinpointed the ranges. of population survival as a function of
prey density for each species. This relationship is shown in Figure 21
where it can be seen that cod survive a lower prey density than haddock.


14

Heinle, D. R. and. D. A. Flemer. 1975. Carbon requirements of a population
of the estuarine copepod Eurytemora affinis. Mar. Biol. (Berl.) 31:235-247.

Hempel, G. 1965. On the importance of larval survival for the population
- dynamics of marine food fish. California Coop. Oceanic Fish. Invest.,
Vol. X:13-23.

Hempel, G. and J. H. S. Blaxter. 1963. On the condition of herring larvae.
Rapp. P.-v. Reun. Cons. int. Explor. Mer, 154:35-40.

Hoagman, W. J. 1974. Vital activity parameters as related to the early life
history of larval and post-larval lake whitefish (Coregonus clupeaformis).
In The Early Life History of Fish, Ed. by J. H. S. Blaxter. Springer-
Verlag, Berlin. pp. 547-558.

Houde, E. D. 1969. Sustained swimming ability of larvae of walleye
istizostedion vitreum vitreum) and yellow perch (Perca flavescens). J.
Fish. Res. Board Can. 26:1647-1659.

1974. Effects of temperature and delayed feeding on growth and
survival of larvae of three species of subtropical marine fishes. Mar.
Biol. 26:271-285.

1975. Effects of stocking density and food density on survival,
growth and yield of laboratory-reared larvae of sea bream Archosargus
rhomboidalis (L) (Sparidae). J. Fish. Biol. 7:115-127.

1978. Critical food concentrations for larvae of three species of
subtropical.marine fishes. Bull. Mar. Sci., 28:395-411.

Houde, E. D. and R. C. Schekter. 1978. Simulated food patches and survival
of larval bay anchovy, Anchoa mitchilli, and sea bream Archosargus
rhomboidalis. Fish. Bull.» U.S., 76:483-486.

1982. Comparative bioenergetics among three species of subtropical
marine fish larvae. Mar. Biol. (Submitted).

Hunter, J. R. 1972. Swimming and feeding behavior of larval anchovy, Engraulis
mordax. Fish. Bull.» U.S., 70:821-838.

.» 1976. Culture and growth of northern anchovy , Engraulis mordax,
Tarvae. Fish. Bull.,U.S., 74:81-88. :

1981. . Feeding ecology and predation of marine fish larvae. In
Marine fish larvae - morphology, ecology and relation to fisheries, Ed.
by R. Lasker. University of Washington Press. pp. 34-77.

Hunter, J. R. and C. Kimbrell. 1980. Early life history of Pacific mackerel,
Scomber japonicus. Fish. Bull.,U.S., 78:89-101.

Hutchinson, G. E. 1961. The paradox of the plankton. Am. Nat. 95:137-145.


10

starvation, keep actively searching for food, and be able to still feed success-
fully is in the order of 4-7 days for haddock larvae (Laurence 1974, 1978). So
searching parameters could be expanded by a factor of 4-7. 2) Larval fishes have
the behavioral ability to remain in concentrations of prey once located. This
strategy might allow successful existence in a contagious prey environment with
small scale patches or considerable distances between patches. 3) Since larvae and
their prey are transported by currents of greater velocity than their own swimming
power and since the prey swim with a certain velocity relative to the larvae,
larval searching parameters could be expanded. if prey were moving in a direction
opposed to the larvae or if the larvae swam against the prevailing current direction
for any length of time. This expansion would be by a factor of the prey or current
velocity. These factors have been or are quantifiable. .

This sampling strategy and the measurement capabilities of available sensors
exceed requirements necessary to relate to fish larvae on the vertical and approach
those necessary for horizontal determinations. The discrete and continuous measure-
ments of the aforementioned physical and biological factors will allow a physical
and statistical description of the heterogeneity (or lack of) of the prey environ-
ment of larval haddock as well as describe and understand functional trophic
linkages and production aspects.

Results to date (Lough and Laurence, 1981, and unpublished) indicate that
larval food is contagiously distributed on a small scale (Table 11), that the
absolute abundance of food organisms can approach the calculated requirements
based on experimental results (Fig. 4 and Table 11), that larvae and prey do co-
occur vertically in the water column and that these distributions and occurrences
can be both maintained and disrupted by meteorological and physical forces (Figs.
4 and 5), and that conditions can be quite variable from year to year (Figs. 4-7)
and in different areas of bottom depth on the bank (Figs. 6 and 7).

TV OPINIONS--TWO PERSISTENT PROBLEMS

Without a doubt the single most significant drawback to understanding larval
trophodynamics in the natural environment is a lack of available technological
means for making fine scale measurements of small organisms. There is a particular
need to be able to count and size planktonic organisms "in situ" in real time
without disturbing their behavior or distribution. There have been some small
advances in particle counting technology as spin-off from other applications,
however, it has been minimal. There is little doubt that the acoustic, optical
and laser technologies currently available to the defense, space and oil industries
could be applied to fishery problems. But, until society places living resource
problems above defense, space and oil, there is little chance that engineers, etc.
associated with developmental technological systems will cooperate with living
resource programs in other than a trickle down manner, or that living resource
Programs will receive enough money to devote to specific developmental engineering
research.


93

LITERATURE CITED

ANDERSEN, K. P. and E. URSIN.
1977. A multispecies extension to the Beverton and Holt Theory of

Fishing, with accounts of phosphorus circulation and primary
production. Medd. Dan. Fisk. Havunders., N. S., 7:319-435.

BEYER, J. E., and G. C. LAURENCE.
1980. A stochastic model of larval growth. Ecol. Modelling 8:109-
132.

BEYER, J. E., and G. C. LAURENCE.
1981. Aspects of stochasticity in modelling growth and survival of
clupeoid fish larvae. Rapp. P.-v. Reun. Cons. int. Explor. Mer
178:17-23.

BLAXTER, J. H. S., and M. E. STAINES.
1971. Food searching potential in marine fish larvae. Proc. 4th
European Marine Biol. Symposium. Ed. by D. J. Crisp. Cambridge

University Press. pp. 467-481.

BOLZ, G. R., and R. G. LOUGH.
1983. Larval cod (Gadus morhua) and haddock (Melanogrammus
aeglefinus) growth on Georges Bank, late winter and spring,
1581: Fish. Bull, U.S. (In press)

BUCKLEY, L. J., and D. W. DILLMAN.
1982. Nitrogen utilization by larval summer flounder (Paralichthys
dentatus). J. Exp. Mar. Biol. Ecol. 59:243-256.

ELLERTSEN, B., P. SOLEMDAL, T. STROMME, S. TILSETH, T. WESTGARD, and V.
OLESTAD.
1980. Some biological aspects of cod larvae (Gadus morhua L.)
Fiskerdir. Skr. Ser. Havunders. 17:29-47.

KANE, J.
1984. The feeding habits of co-occurring cod and haddock larvae.
Mar. Ecol. Prog. Ser. 16:9-20.

LAURENCE, G. C.
1977. A bioenergetic model for the analysis of feeding and survival

potential of winter flounder, Pseudopleuronectes americanus,
larvae during the period from hatching to metamorphosis. Fish.
Bull, U.S. 75:529-546.

LAURENCE, G. C.
1978a. Larval length-weight relations for seven species of northwest
Atlantic fishes. Fish. Bull., U.S. 76(4):890-895.

LAURENCE, G. C.
1978b. Comparative growth, respiration and delayed feeding abilities

of larval cod (Gadus morhua) and haddock (Melanogrammus


150

ce | STANDING. STOCKS=GEORGE’S-BANK.... 143°
3 8
PEAK LARVAL GADID ABUNDANCE-0.25/M OR 743X12

: 15 }
4ac- 3 , : 43°
VOLUME - M H20 ) . 2

/
12 ;
2.96X18  s100M a
al ‘
41
ot nen MAXIMUM ANNUAL LARVAL PRODUCTION
om OO 12 :
SL = 11K18

J sane 5
40° RELEVANT RATIOS EAN LARVAL PREY COMSUMMED TO |] |
oo 1000 ug AT 8%/DAYAG = 1707: )

INSTANTANEOUS PREY/LARVA-SSGQQ: 1 Bee cee em

ANNUAL LARVAL PRODUCTION PREY

INSTANTANEOUS PREY/ANNUAL LARVAL 15:

PRODUCTION CONSUMPTION - 124.5 CONSUMPTION = 188X180 .
sora ; ; ; F F os J sg°

ve 70° 69° 68° 67° 66°

Figure 44. A graphic illustration of the parameters -and calculations
involved in assessing food limitation and impact on prey for
larval gadids on Georges Bank. a8

EU. S. GOVERNMENT PRINTING OFFICE: 1985--501-657-~20,041


VI.

VII.

VIII.

Ix.

22
Morphology, Histology and Development
A. Developmental Sequence, Inhibitors, Enhancers of:
1. Mouthparts
2. Eye :
3. Digestive Organs
4. Musculature and Locomotor Skeletal Components
Behavior
A. Ethological Reactions and Interactions
1. Predator-prey Responses
a. detection, reaction, attack, flight
B. Swimming Abilities
1. Activity Levels
2. Sustained and Short Term "burst" levels
3. Changes with Age/Size
4. Changes with Prey Level
C. Visual Fields
1. Phototaxis
2. Perception
Nutrition
A. Palatability - Acceptability
B. Nutritional Values
C. Organic (Energy) Components
D. Inorganic (Essential) Components
€. Non Essential Fillers, Binders, Matrices, Encapsulators, etc.
Aquaculture
A. Differences in Concepts and Goals of Laboratory Experimental

Research and Culture Optimization


DUBLRLOBUDRLHOmAENOU RH OU ENO ON

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Dan

14.

150

200

250

300

350

400

450

500

600

700

800

900
1000
1100
1200
1300
1400
1500
1600
1700
1800
1900
2000
2100
2200
2300
2400
2500
2600
2700
2800
2900
3000
3100
3200
3300
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
4600
4700
4800
4900
5000
5100
5200
5300
5400
5500
5600
§700
5800
5900
6000
6100
6200
6300
6400
6500
6600
6700
6800
6900
7000
7100
7200
7300
7400
7500

408.0
416.0
424.0
432.0
440.0
448.0
456.0
464.0
472.0
480.0
488.0
496.0
504.0
512.0
520.0
528.0
536.0
544.0
$52.0
560.0
568.0
576.0
584.0
592.0
600.0

103

1.88

4.15

16.57
17.05

18.92
19.38

20.72
21.16
21.59
22.02
22.45
22.88
23.30
23.71
24.13
24.54
24.95
25.35
25.76
26.16
26.55
26.95
27.34
27.73
28.12
28.51
28.89
29.27
29.65
30.03
30.40
30.77
31.14
31.51
31.88
32.24
32.61
32.97
33.33
33.69
34.04
34.40
34.75
35.10
35.45
35.80
36.15
36.49

28.1
34.2
39.8
45.1
$0.1
54.9
59.5
64.0
72.5
80.5
88.2
95.7
102.8
109.7
116.5
123.0
129.4
135.7
141.8
147.8
153.7
159.5
165.2
170.8
176.3
181.7
187.1
192.4
197.6
202.8
207.9
212.9
217.9
222.9
227.8
232.6
237.4
242.2
246.9
251.6
256.2
260.8
265.3
269.9
274.3
278.8
283.2
287.6
292.0
296.3
300.6
304.9
309.1
313.3
317.5
321.7
325.8
329.9
334.0
338.1
342.1
346.1
350.1
354.1
358.1
362.0
366.0
369.9
373.7
377.6
381.4
385.3
389.1
392.9
396.7
400.4
404.2
407.9

85.5
76.7
70.4
65.6
62.0
59.1
56.7
54.8
51.9
49.8
48.3
47.2
46.4
45.8
45.4
45.2
45.0
44.9
44.8
44.8
44.9
44.9
45.0
45.2
45.3
45.4
45.6
45.7
45.9
46.0

46.4
46.5
46.7
46.9
47.0
47.2
47.4
47.5
47.7
47.8
48.0
48.1
48.3
48.4
48.6
48.7
48.9
49.0
49.2
49.3
49.5
49.6
49.7
49.9
50.0
50.2
50.3
60.4
50.5
50.7
50.8
50.9
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51.2
51.3
51.4
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51.7
51.8
51.9
52.0
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52.2
52.4
52.5
52.6
52.7


FREQUENCY

124

1B
CON-MODEL 2
DAY 42
“23% SURVIVAL
1@ PREY/LITER
8 X=4962380
6K
at
2k
a =e
2 i=] 32 =] =]
= 8 &-& 8 8S § §& 8 8

LARVAL WEIGHT (ug)

Figure 18. Frequency histogram of the distribution of larval weights of
prs at 42 days after hatching. Cod model 2 at 10 prey

survi vi
liter”

2100


46

resolve patterns and interactions occurring on the over-
lapping time-space’scales (Haury et al., 1978). In this
paper our sampling. strategy is presented on the haddock-
cod study-which-has evolved.in part fromthe results of the
Larval. Herring-Patch Study. The experimental objectives,
sampling gear and instrumentation employed are discussed
in terms of.the usefulness of the parameters measured and
highlighted with data analyzed to-date.

Target Species

Haddock .(Melanogrammus aeglefinus L.) was chosen as the
main target species, followed by cod (Gadus morhua L.), be-
cause of its commercial and ecological importance and the
best overall base of life history data. This data base
includes extensive laboratory experimental data, an index
of year-class. strength at the 'O-group' stage, and fecundity
and spawning population biomass data. The northeastern part
of Georges :Bank.is a principal spawning ground for haddock
and cod:and their early life histories are similar in many
respects.. Their spawning seasons overlap, but for cod it
is considerably longer and alsa its spawning distribution
appears to.extend further south than the haddock's (Colton
et al., .1979). Cod spawn from late autumn into April-May,
whereas. haddock spawn from February to June. Peak spawning
for both cod and haddock occurs in the spring with cod
spawning about a month earlier than haddock. The onset and
duration of. haddock spawning appears to be associated with
increasing water temperature (Marak and Livingstone, 1970).

Fertilized cod and haddock eggs hatch in about 2-3 weeks
at average spring temperatures (Marak and Colton, 1961;
Laurence and Rogers, 1976), and the larvae are planktonic
for several months thereafter. The larvae hatch at c.

4 mm SL (Colton and Marak, 1969) and yolksac resorption is


100

Table 2. Deterministic parameters and output variables at three constant daily growth rates for haddock
Jarvae. Each iteration represents a specific weight in the range from the initial weight at hatching-yolk
absorption until 10,000 ig.

12.5% Growth Rate

Dry Daily Growth Preferred Digestion=
Length Weight Increment Prey Size Metabolism Utilization # Prey
(mm) (ug) (ug) (ug) (ug) Coefficient Required
4.8 50 6.3 72 13.2 +30 140.4
5.3 75 9.4 1.04 17.5 32 124.3
5.6 100 12.5 1.33 . 21.3 35 113.5
6.2 150 18.8 1.88 28.1 39 99.1
6.6 200 25.0 2.38 34.2 43 : 89.6
6.9 250 31.3 2.85 39.8 46 82.9
7.2 300 37.5 3.30 45.1 -50 77.8
7.4 350 43.8 3.73 50.1 53 73.8
77 400. 50.0 4.15 54.9 655 70.7
7.9 450 56.3 4.55 59.5 58 68.1
8.1 $00 62.5 4.94 64.0 +60 66.1
8.4 600 75.0 5.69 72.5 -63 62.9
8.7 700: 87.5. 6.40 80.5 +66 60.7
8.9 800 100.0 7.09 88.2 69 59.2
9.2 900 112.5 7.75 95.7 71 58.1
9.4 1009 125.0_ 8.40 102.8 73 $7.3
9.6 1100 137.5 9.02 109.7 74 56.8
9.8 1200 150.0. 9.63 116.5 75 56.5
10.0 1300 162.5 10.23 123.0 . 76 56.3
10.1 - 1400 175.0 10.81 129.4 77 56.2
10.3 1500 187.5 11.38 135.7 77 56.2
10.4 1600 200.0 11.93 141.8 78 56.3
10.6 1700 212.5 12.48 147.8 78 56.4
10.7 1800 225.0 13.02 153.7 78 56.6
10.8 1900 237.5 13.55 159.5 79 56.8
11.0 2000 250.0 14.07 165.2 79 57.0
lle. 2100 262.5 14.58 170.8 79 57.2
11.2 2200 275.0 15.09 176.3 79 57.5
11.3 2300 287.5 15.59 181.7 79 57.7
11.4 2400 300.0 16.08 187.1 +80 58.0
11.5 2500 312.5 16.57 192.4 +80 58.3
11.6 2600 325.0 17.05 197.6 «80 58.6
11.7 2700 337.5 17.53 202.8 +80 58.9
11.8 2800 350.0 18.00 207.9 +80 $9.1
11.9 2900 362.5 18.46 212.9 «80 59.4
12.0 3000 375.0 18.92 217.9 «80 $9.7
12.1 3100 387.5 19.38 222.9 80 60.0
12.2 3200 400.0 19.83 227.8 80 60.3
12.2 3300 412.5 20.28 232.6 «80 60.5
12.3 3400 425.0 20.72 237.4 -80 60.8
12.4 3500 437.5 21.16 242.2 80 61.1
12.5 3600 450.0 21.59 246.9 +80 61.3
12.6 3700 462.5 22.02 251.6 80 61.6
12.6 3800 475.0 22.45 256.2 80 61.9
12.7 3900 487.5 22.88 260.8 -80 62.1
12.8 4000 500.0 23.30 265.3 80 62.4
12.8 4100 512.5 23.71 269.9 80 62.6
12.9 4200 525.0 24.13 274.3 -80 62.9
13.0 4300 537.5 24.54 278.8 80 63.1
13.0 4400 550.0 24.95 283.2 -80 63.4
13.1 4500 562.5 25.35 287.6 80 63.6
13.2 4600 575.0 25.76 292.0 80 63.9
13.2 4700 587.5 26.16 296.3 -80 64.1
13.3 4800 600.0 26.55 300.6 80 64.3
13.4 4900 612.5 26.95 304.9 80 64.5
13.4 5000 625.0 27.34 309.1 80 64.8
13.5 5100 637.5 27.73 313.3 80 65.0
13.5 5200 650.0 28.12 317.5 80 65.2
13.6 5300 662.5 28.51 321.7 +80 65.4
13.7 5400 675.0 28.89 325.8 80 65.7
13.7 5500 687.5 29.27 329.9 -80 65.9
13.8 5600 700.0 29.65 334.0 80 66.1
13.8 5700 712.5 30.03 338.1 +80 66.3
13.9 5800 725.0 30.40 342.1 -80 66.5
13.9 5900 737.5 30.77 346.1 -80 66.7
14.0 6000 750.0 31.14 350.1 80 66.9
14.0 6100 762.5 31.51 354.1 -80 67.1


64

MELANOGRAMMUS AEGLEFINUS

sor 16-16 APRIL 198t
=
» °F z= 3.6mm
=
8
g 20b
we
oS er ee
19-21 MAY 1981
30
~
x #260
~ 20k x mm
$
=
x }
= tok
e
&
l .
0

LENGTH (mm)

Fig. 7. Length-frequency distributions of haddock larvae
collected on the April and May 1981 grid surveys.

historical spawning grounds. Cod larvae were more widespread
than haddock and their greater size range was indicative of
their earlier spawning in February-March.

By May, a concentration of larval haddock and cod was
located along the southern flank of Georges to the southwest
of the April distribution, situated between the shoal tidal
front and the deeper shelf/slope-water front. The mean
length of both larval populations sampled on the grid was
6 mm and is consistent with laboratory growth rates over the
period of time between hatching in April and the May survey
(Laurence, 1978; Bolz and Lough, 1983). Also,an estimated
transport of 1-2 miles/d, which is consistent with the long- .
term residual. currents reported for this area, would account


16

1972. Comparative swimming abilities of fed and starved larval
Targemouth bass (Micropterus salmoides). J. Fish. Biol. 4:73-78.

1973. Influence of temperature on energy utilization of embryonic
and prolarval autog, Tautoga onitis. J. Fish. Res. Board Can. 30:435-442

1974. < Growth and survival of haddock (Melanogrammus aeglefinus)
Tarvae in relation to planktonic prey concentration. J. Fish. Res. Board
Can., 31:1415-1419.

1976. Caloric. values: of some North Atlantic copepods. Fish. Bull.

74(1) :218-220.

1977.° A bioenergetic model for the analysis of feeding and survival
potential of winter flounder, Pseudopleuronectes americanus, larvae during
the period from hatching to metamorphosis. Fish., Bull. U.S., 74:529-546.

1978. Comparative growth, respiration and delayed feeding abilities
Of larval cod (Gadus morhua) and haddock (Melanogrammus aeglefinus)
as influenced by temperature during laboratory studies. Mar. Biol. 50:1-7.

-_. 1979. Larval length-weight relations for seven species of Northwest
Atlantic fishes reared in the laboratory. Fish. Bull., U.S., 76:890-895.

1981. Modelling - An esoteric or potentially utilitarian approach
to understanding larval fish dynamics. Rapp. P.-v. Reup. Cons. int.
Explor. Mer, 178:3-6.

Lough, R. G. and G. C. Laurence. 1981. Larval haddock and cod survival
studies on. Georges Bank. 12 p. In ICES Larval Fish Ecology Working
Group. ICES C.M.1982/L:3.

Marak, R. R. 1960. Food habits of larval cod, haddock and coalfish in the
Gulf of Maine and Geroges Bank area. J. Cons. Perm. int. Explor. Mer,
25(2):147-157.

Martin, F. D. and G. D. Drewry. 1978. Development of fishes of the mid-Atlantic
bight. Vol. VI. Stomateidae through Oyocephalidae. U. S. Dept. of
Interior, Fish Wildl. Serv.

May, R. C. 1974. Larval mortality in marine fishes and the critical period
concept. In The Early Life History of Fish, Ed. by J. H. S. Blaxter.
Springer-Verlag, NY. pp. 3-19.

Mikham, A. S. 1969. Some new data on the larval feeding of the Azov tyul'ka
(Clupeonelta delicatula (Nordm.)) and on the role of the nutritional
factor in fluctuations in its abundance. Probl. Ichthyol. 9:666-673.
(trans]. from Vop. Ikhtiol.)

National Research Council. 1981. Nutritional requirements of coldwater
fishes. Subcommittee on Coldwater Fish Nutrition, National Academy of
Sciences, Washington, D.C. 63 p.


82

Saville, A., 1956. Eggs and larvae of haddock (Gadus
aeglefinus L.) at Faroe. Mar. Res-, No- 4: 1-27.

Shepherd, J.G. and Cushing, D-H., 1980. A mechanism for
density-dependent survival of larval fish as the basis
ef a stock~recruitment relationship. J. Cons- int.
Explor. Mer, 39: 160-167. .

Sherman, K., 1980. MARMAP, a fisheries ecosystem study in
the Northwest Atlantic: Fluctuations in ichthyoplankton-
zooplankton components and their potential for impact on
the system. In: F.P. Diemer, F.J. Vernberg and. D.Z.
Mirkes (Editors), Advanced Concepts in Ocean Measurements
for Marine Biology. University of South Carolina Press,
Columbia, S.C., pp. 9-37.

Sherman, K., Maurer, R-, Bryon, R- and Green, J., 1981. Re-
lationships between larval fish communities and zooplankton
prey species in an offshore spawning ground. Rapp. P.-v.
Reun. Cons. int. Explor. Mer, 178: 289-294.

Smith, W.G., Pennington, M., Berrien, P., Sibunka, J., Koni-
ec2na, M., Baranowski, M. and Meller, E., 1979. Annual
changes in the distribution and abundance of Atlantic cod
and haddock larvae off the northeastern United States be-
tween 1973-74 and 1977-78. Coun. Meet. int. Coun. Explor.
Sea, 1979 (G:47): 1-19 (Mimea.).

Theilacker,' G.H., 1981. Effect of feeding history and egg
size on the morphology of Jack mackerel, frachurus sym-
metzricus, larvae. Rapp. P.-v- Réun. Cons. int. Explor.
Mer, 178: 432-440.

Tilseth, S. and Ellertsen, B., 1934. The detection and dis-
tribution of larval cod (Gadus morhua L.) food organisms
by an in situ particle counter. Fish. Bull., U.S., 82:
(in press).

Tungate, D.S. and Reynolds, E., 1980. The MAFF on-line par-
ticle counting system. Fish. Res. Tech. Rept., MAFF Direct
Fish. Res. Lowestoft, No. 58: 1-111.

Viymen, W.J., 1977. A mathematical model of the relationship
between larval anchovy (Engraulis mordax) growth, prey
micro-distribution, and larval behavior. Env-~ Biol. Fish.,
2: 211-233.

Walford, L.A., 1938. Effect of currents on distribution and
survival of the eggs and larvae of haddock (Melanogrammus
aeglefinus) on Georges Bank. Fish. Bull., U.S., 49: 1-73.

Wiborg, K.F., 1960. Investigations on eggs and larvae of
commercial fisheries in Norwegian coastal and offshore
waters in 1957-58. Fisk. Dir. Skr. Ser. HavUnders., 12:
1-27.

Wiebe, P.H., Boyd, S.H., Davis, B.M. and Cox, J.L., 1982.
Avoidance of towed nets by the euphausiid Nematoscelis
megalops. Fish. Bull., U.S., 80: 75-91.

Wiebe, P.H., Burt, K.H., Boyd, S.H. and Morton, A.W., 1976.

A multiple opening/closing net and environmental sensing

system for sampling zooplankton. J. Mar. Res., 34: 313-
326.


xii

A REPORT ON THE DEVELOPMENT OF STOCHASTIC MODELS OF FOOD LIMITED GROWTH
AND SURVIVAL OF COD AND HADDOCK LARVAE ON GEORGES BANK

Figure 1.

Figure 2.

Figure 3.

Figure 4.
Figure 5.

Figure 6.

Figure 7.

Figure 8.

Figure 9.

Figure 10.

Figure 11.

Figure 12.

Figure 13.

Figure 14.

Figure 15.

Daily (24-hr) metabolic expenditure of cod and haddock larvae
as a function of body size. Based on empirical respirometer
measurements from Laurence (1978).

Relationship of mean preferred prey size and larval size for
nt and haddock larvae. Based on empirical data from Kane
1983).

Relationship of the fraction of food ingested. that is
utilized in the digestion process and larval size for cod and

haddock larvae. From Beyer and Laurence (1981) based on
nitrogen budget research of Buckley and Dillmann (1982).

Daily visual searching capacity of cod and haddock larvae.

Relationship of the probability of capturing an encountered
prey organism and larval size of cod and haddock.

Minimum barrier or the smallest size larvae alive at a given
time for cod and haddock larvae in laboratory experiments.

Daily weight gain or loss of 3 haddock larvae feeding on
variable daily rations.

An abbreviated flow chart of the basic 4 element stochastic
computer model.

Frequency histograms of the normal ized distribution of # of
prey of preferred size consumed dayTM* for a newly hatched
44 ug cod larva at a prey density of 10 literTM*.

Frequency histograms of the normalized distribution of # of
prey of preferred size consumed day~* for a newly hafched
68.1 ug haddock larva at a prey density of 25 literTM* —

Frequency histogram of the distribution of larval weights of
survivors at 42 days after hatching. Cod model 1 at 10 prey
liter “+.

Frequency histogram of the distribution of prey size about
the preferred prey size for a 44 ug cod larva.

Frequency histogram of the distribution of prey size about
the preferred prey size for a 250 ug cod larva.

Frequency histogram of the distribution of prey size about
the preferred prey size for a 750 ug cod larva.

Frequency histogram of the distribution of prey size about
the preferred prey size for a 68.1 wg haddock larva.


65

GADUS MORHUA

307 16-18 APRIL 1981

FREQUENCY (%)

30° 19-21 MAY 1981

i= 61mm

FREQUENCY (%)

LENGTH (mm)

Fig. 8. Length-frequency distributions of cod larvae col-
lected on the April and May 1981 grid surveys.

for the displacement between the highest concentration of
eggs in April and larvae in May. Coupled with the fact that
no other egg or larval concentrations were found in the area,
these observations support the view that the egg and larval
concentrations defined belonged to the same spawning popula-
tion.

An important feature of these egg and larval concentrations
is their coherence and stability which provide continuity in
the sampling program. The grid station densities have been
contoured by a. factor of 4 as the coefficient of variation of
a single plankton haul typically is in the range of 22-44%
(Cassie, 1963). Note the internal consistency of the station
values within the contoured areas. Resampling a grid tran-
sect once on the April survey and again in May 4-7 d later


71

SIGMA-T
25.06 .20 « R_°] 80 2600

DEPTH (m)

te]

Fig. 12. Water-column density (sigma-t) profiles on strati-
fied station (40°55'N 67°16'W) before and after storm, 22-
24 May 1981. Corresponding MOCNESS haul numbers shown.

Phytoplankton biomass was uniformly low throughout the water
column with a noticeable increase in the bottom few meters,
but slightly higher (1-2 mg chl a/m?) than the deeper station
(80 m).

The dominant copepods on Georges Bank in late-winter and
spring are Pseudocalanus sp., Calanus finmarchicus, and
Oithona similis. Pseudocalanus tends to be more abundant on
the shoal area of Georges while Calanus develops high abun-
dance in the near-surface waters of the stratified zone
along the southérn flank. oithona, a small copepod, is wide-
spread in its distribution. “rey selection studies of larval


Preceding Page Blank | ix

cee ~~ LIST OF TABLES

NUTRITION AND TROPHODYNAMICS OF LARVAL FISH - REVIEW, CONCEPTS,
STRATEGIC RECOMMENDATIONS AND OPINIONS:

Table 1.

Table 2.

Table 3.

Table 4.

Table 5.

Table 6.

Table 7.

Table 8.

Table 9.

Table 10.
Table 11.

Species specific early life history parameters. (Table 1 from
Theilacker and Dorsey, 1980).

Critical prey densities for fish larvae. (Table 4 from
Theilacker and Dorsey, 1980).

Average densities of microcopepods in the sea. (Table 5 from
Theilacker and Dorsey, 1980).

Field concentrations of larval fish food organisms. (Table 10
from Houde, 1978).

Swimming performance of larval fishes. (Table 2 from
Theilacker and Dorsey, 1980).

Searching ability of larval fishes. (Table XIII from Blaxter,
1969).

Growth efficiencies of larval fishes. (Table 9 from
Theilacker and Dorsey, 1980).

Caloric and ash values for some North Atlantic copepods.
Species are recorded in order from largest to smallest mean
value under each category. Those species side-scored have
similar means (Duncan's New Multiple Range Test, P = 0.05).
(Table 1 from Laurence, 1976).

Larval haddock daily feeding requirements and calculation
parameters.

Larval haddock swimming, searching and food encounter.

Small scale discrete plankton sampling on Georges Bank.
Twelve replicates each of 1.7, 8.0 and 30 1 collected
simultaneously in same area. Morisita index 1.0 or greater
denotes statistically significant contagion between
replicates. Evrika 80-02, Station 47, May 21, 1980, 1610 GMT,
41°00'N, 67°5I'W, bottom depth 44 m. Water temperature 7.4
isothermal. Gadoid larvae present.

A REPORT ON THE DEVELOPMENT OF STOCHASTIC MODELS OF FOOD LIMITED GROWTH
AND SURVIVAL OF COD AND HADDOCK LARVAE ON GEORGES BANK

Table 1.

Deterministic parameters and output variables at three
constant dafly growth rates for cod larvae. Each iteration
represents a specific weight in the range from the initial
weight at hatching-yolk absorption until 10,000 ug.


17.6
17.6
17.7
17.8
17.8
17.9
17.9
18.0
18.0
18.1
18.1
18.2
18.2
18.3
18.3
18.4
18.4
18.5
18.5
18.6
18.6
18.7
18.7
18.8
18.8

7600
7700
7800
7900
800
8100
8200
8300
8400
8500
8600
8700
8800
8900
9000
9100
9200
9300
9400
9500
9600
9700
9800
9900
10000

950.0

962.5

975.0

987.5
1000.0
1012.5
1025.0
1037.5
1050.0
1062.5
1075.0
1087.5
1100.0
1112.5
1125.0
1137.5
1150.0
1162.5
1175.0
1187.5
1200.0
1212.5
1225.0
1237.5
1250.0

144,16
145.65
147.13.
148.61
19

99

244.3
246.7
249.2
254.2

259.1

16.3
16.4
16.4
16.4
16.5
16.5
16.5
16.6
16.6
16.6
16.7
16.7
16.7
16.8
16.8
16.8
16.9
16.9
16.9
17.0
17.0
17.0
V7.1
W.1
Wal



69

A) STRATIFIED STATION

21 MAY 1981 MOC 19t 24-26 MAY 1981 MOC 193-207 28 MAY 1981 MOC 220
wo. /100M> wa/too Ms wo.stooms

fo} 100 200 300 gon 200 100 fe} 100 200 fe 50 ie

1
night = TOF Z
20

fe)

10 + 10 oay
20 20
ca) 30 30
&
z 40 40 40
g s0 %
60 60
4157 10M? 70 a a 70 156/ 10M?
80 900/10M2 6r7/1om? 80
B) WELL-MIXED STATION
27-29 MAY 1981 MOC 209-224 MELANOGRAMMUS
No.7100M4 AEGLEFINUS
140-80 ° 80 pA
° GEORGES BANK
,* MOCNESS —/M
£ 20
E 30
Q
§ 40 SINGLE 08S

a 4 WEIGHTED MEAN DEPTH

224/10M?

256/10M2

Pig. 10. Vertical distribution of haddock larvae on (A)
stratified station (40°55'N 67°16'W) before and after storm,
22-24 May 1981, and on (B) shoal, well-mixed station
(41°07'N 67935'W), 27-29 May 1981.

(220) showed that a shallow thermocline had formed and the
larvae were reaggregating in the upper 20 m associated with
the restratification. By plotting water column density
(sigma-t) values during this period in Fig. 12, one can see
the process of restratification between the time the storm
abated sufficiently to resume sampling on 24 May (MOC 193)
and the last haul on 28 May (MOC 220). At this rate it
would take a total of about 7-10 d for the water column and
fish larvae to restructure to the same degree observed prior
to the storm. Miller et al. (1963), in a mid-May 1958 ver~
tical distribution study of larval haddock around the flank


95

Table 1. Deterministic parameters and output variables at three constant daily growth rates for cod
jJarvae. Each iteration represents a specific weight in the range from the initial weight at hatching-yolk
absorption until 10,000 ug.

4% Growth Rate

Ory Daily Growth Preferred Digestion-
Length Wei ght Increment Prey Size Metabolism Utilization # Prey
(mm) (ug) (ug) (4g) (1g) Coefficient Required
5.1 Su 2.0 5.0 +32 20.8
5.6 75 3.0 6.8 34 17.9
6.0 100 4.0 8.5 36 16.0
6.7 150 6.0 11.7 40 13.7
7.2 200 8.0 14.6 4d 12.2
250 10.0 173 +48 11.1
. 300 12.0 20.0 51 10.4
8.2 350 14.0 22.5 «53 9.7
8.5 400 16.0 24.9 +56 9.3
8.8 450 18.0 27.3 58 8.9
9.0 500 20.0 29.6 +60 8.6
9.4 600 24.0 34.1 64 8.1
9.8 700 28.0 38.5 67 7.7
10.1 800 32.0 42.7 69 7.5
10.4 900 36.0 46.7 wl 7.3
10.7 1000 40.0 50.7 73 7.1
u 1100 44.0 54.6 «74 7.0
li. 1200 48.0 58.4 75 7.0
11.4 1300 52.0 62.2 76 6.9
11.6 1400 $6.0 65.8 77 6.9
11.8 1500 60.0 69.5 7 6.8
12.0 1600 64.0 73.0 78 6.8
12.2 1700 68.0 76.5 18 6.8
12.3 1800 72.0 80.0 79 6.8
12.5 1900 76.0 83.4 79 6.8
12.6 2000 80.0 86.8 79 6.8
12.8 2100 84.0 90.1 79 6.8
12.9 2200 88.0 93.5 79 6.8
13.1 2300 92.0 96.7 6.8
13.2 2400 96.0 100.0 6.8
13.4 2500 100.0 103.2 6.8
13.5 2600 104.0 106.4 6.8
13.6 2700 108.0 109.5 6.9
13.7 2800 112.0 112.7 6.9
13.9 2900 116.0 115.8 6.9
14.0 3000 120.0 118.8 6.9
Mal 3100 124.0 121.9 6.9
14.2 3200 128.0 124.9 6.9
14.3 3300 132.0 128.0 7.0
14.4 3400 136.0 131.0 7.0
14.5 3500 140.0 133.9 7.0
14.6 3600 144.0 136.9 7.0
14.7 3700 148.0 139.8 7.0
14.8 3800 152.0 142.7 7.0
14.9 3900 156.0 145.6 7.0
15.0 4000 160.0 148.5 7.1
15.1 4100 164.0 151.4 7
15.2 4200 168.0 154.3 7a
15.3 4300 172.0 157.1 7.1
15.4 4400 176.0 159.9 7.
15.5 4500 180.0 162.7 7.1
15.5 4600 184.0 165.5 7.2
15.6 4700 188.0 168.3 7.2
15.7 4800 192.0 V1. 7.2
15.8 4900 196.0 173.8 7.2
15.9 $000 200.0 176.6 7.2
15.9 5100 204.0 179.3 7.2
16.0 5200 208.0 182.0 7.2
16.1 5300 212.0 184.7 7.3
16.2 5400 216.0 110.03 187.4 7.3
16.2 5500 220.0 111.64 190.1 7.3
16.3 5600 224.0 113.25 192.8 7.3
16.4 6700 228.0 114.85 195.¢ 7.3
16.5 5800 232.0 116.45 198.1 73
16.5 5900 236.0 118.04 200.7 7.3
16.6 6000 240.0 119.62 203.4 7.3
16.7 6100 244.0 121.19 206.0 7.4



80

Denman, K. and Platt, T., 1978. Time series analysis in
marine ecosystems. In: H.H. Shugart, Jr. (Editor), Time
Series and Ecological Processes. Proceedings of SIAM-SIMS
Conference, Alta, Utah, June-July, 1977. SIAM, Philadelphia,
PA, pp. 227-242.

Grosslein, M.D., Brown, B.E. and Hennemuth, R.C., 1979. Re-
search, assessment, and management of a marine ecosystem
in the northwest Atlantic -- a case study. In: J. Cairns,
dr., G.P. Patil and W:E. Walters (Editors), Environmental
Biomonitoring, Assessment, Prediction, .and Management -
Certain Case Studies and Related Quantitative Issues.
International Co-operative Publishing House, Fairland, MD,
pp. 289-357.

Grosslein, M.D. and Hennemuth, R.C., 1973. Spawning stock
and-other factors related to recruitment af haddock on
Georges Bank. Rapp. P.-v. Réun. Cons. int. Explor. Mer,

- 164: 77-88. ©

Gower, J.F.R., 1982. General overview of the nature and use
of satellite remote sensing data for fisheries application.
NAFO Sci. Counc. Studies, 4: 7-19.

Haury, L.R-, McGowan, J.A. and Wiebe, P.H., 1978. Patterns and
processes in the time-space scales of plankton distributions.
In: J.H. Steele (Editor), Spatial Pattern in Plankton Com-
munities. Plenum Press, NY, pp. 277-327-

Hennemuth, R.C., Palmer, J.E. and Brown, B.E., 1980. A statis-
tical description of recruitment in eighteen selected fish
stocks. J. Northw. Atl. Fish. Sci., 1: 101-111.

Houghton, R.W. and Marra, J., 1983. Physical/biological struc-
ture and exchange across the thermocline shelf/slope front
in the New York Bight. J. Geophys. Res., 88: 4467-4481.

Joyce, T. and Wiebe, P., 1983. Warm-core rings of the Gulf
Stream. Oceanus, 26: 34-44.

Kane, J., In press. The feeding habits of co-occurring cod
and haddock larvae. Mar- Ecol. Prog. Ser.

Kelley, J.C., 1976. Chapter 15. Sampling the sea. In:

D-H. Cushing and J.J. Walsh (Editors), The Ecology of
the Seas. W.B. Saunders Co., Philadelphia, PA, pp.
361-387.

Lasker, R., 1975. Field criteria for survival of anchovy
larvae. The relation between inshore chlorophyll maxi-
mum layers and-successful first feeding. Fish. Bull.,
U.S., 73: 453-462.

Laurence, G.C., 1974. Growth and survival of haddock
(Melanogrammus aeglefinus) larvae in relation to plank-
tonic prey concentration. J. Fish. Res. Board Can., 31:
1415-1419.

Laurence, G.C., 1978. Comparative growth, respiration and
delayed feeding abilities of larval cod (Gadus morhua)
and-haddock (Melanogrammus aeglefinus) as influenced by
semperature during laboratory studies. Mar. Biol., 50:

-7. . . .

Laurence, G.C., 1981. Modelling -- An esoteric or poten-
tially utilitarian approach to understanding larval fish
dynamics? Rapp. P.-v. Réun. Cons. int. Explor. Mer, 178:
3-6.


48

portion of the larvae apparently are transported north

on the western‘side of'Georges Bank, but little is known
about possible losses of larvae off the bank. The 0-group
fish tend to bé concentrated on the northern part of the
bank indicating a2 favorable environment for their survival.

Hydrography of Georges Bank

The residual drift of Georges Bank is described as a semi-
enclosed clockwise circulation with a mean speed of approxi-
mately 10 cm/s-or 5 km/d (Fig. 2). A counter-clockwise cir-
culation develops in the Gulf of Maine and both gyres inten-
sify in the summer (Bumpus and Lauzier, 1965). In winter the

i a
EH ,
STI

\ 8 /

“ GEORGES BANK BANC
AL AREA 5
; . %
3 XY 4

Fig. 2. Schematic representation of the well-mixed and
stratified waters on Georges Bank and mean circulation flow
(arrows) during.spring and summer.


44

When the same larval population was surveyed again in May
it had moved to the southwest at a rate consistent with the
residual currents. By May the water column was stratified
along the southern flank. A seasonal thermocline was ob-
served between 10.and 20 m and fish larvae and their prey
(SO prey/l) were concentrated in this zone. A storm swept
the region and dispersed the larvae and prey (5-10 prey/1)
throughout the water column. On the crest of the bank in
the well-mixed waters (<60 m), larvae and their prey (10-25
prey/1l) were broadly distributed vertically, but the mean
depth of the larvae coincided with the highest density of
prey at middepth. The implication of these observations to
haddock and cod survival are discussed.

INTRODUCTION

Other than catastrophic losses, trophic (feeding) inter-
relationships involving both growth and predation are con-
sidered to be the basic factors controlling larval mortality.
The mortality process at the individual level is thought to
be a function of, chance encounters by larvae with their pred-
ators and zooplankton prey which (like the larvae themselves)
are distributed contagiously or in patches (Lasker, 1975;
Vlymen, 1977; Beyer, 1980). It is believed that the degree
to which larvae are able to grow rapidly through a succession
of decreasing. predatory fields, thereby reducing mortality,
determines their potential population size. However, this
process is a complex function of the density distribution
(patchiness) of the larvae, their prey and predators, and
possible competitors or other forms which may be alternative
prey of. larval predators. Since prey abundance below some
level will be a.critical factor influencing larval survival,
it is necessary to know how feeding of larvae in the field
is affected by the fine-scale (patchy) distribution of plank-
ton communities and to understand the biological and physical
processes which lead to the formation and dissipation of such
patches. *


be correlated with data from subsequent fall juvenile survey estimates conducted
for a number of species as a validation test. The final step is to integrate
the results into the recruitment functions of appropriate ecosystem or manage-
ment models.

Sampling Rationale and Strategy for Field Verification--
Georges Bank Haddock as an Example

The above cited experimental and descriptive field results of larval
trophodynamics from the first half of this paper, the proposed conceptualization
of functional mechanisms of larval trophodynamics, and the proposed strategy
relating to fishery management needs provide the basis for formulating sampling
rationale and strategy for appropriate field research. Particular emphasis
should be given to the “arena of predation" within which larvae succeed or fail
including: 1) a description of spatial and temporal variability of larval prey
and predators, 2) confirmation of linkages and factors affecting production of
the 3 trophic levels, 3) identification and understanding of the operating
function of physical processes causing or mediating biological consequences.
Since fish larvae are small, and short time and small space scales need to be
considered, the proposed sampling presents unique and challenging problems for
a field program and the technology currently available to support it.

Quantitative Rationale

The prey field of a larval fish is defined by the larva's physical abilities
of locomotion, behavior, and physiological limitations. Actual quantification of
these aspects can provide discrete dimensions relative to a feasible ship board
sampling scheme. The following presentation defines the problem in quantified
terms for Georges Bank haddock based on empirical observations from experimental
research similar to that reviewed in the first part of this paper and model
application extended to the current field program operated by the Larval Fish
Dynamics Investigation of the Northeast Fisheries Center.

Constant, Variable and Parameter Definitions

4G = change in growth day-1. Lab experiments (Laurence, 1974, 1978) and
field data have shown a maximum rate of approximately 6% day-! on a
weight basis and about 2% day-! as a minimum, viable rate.

Ru = food ingested day-1. Where: R= # ingested and w = food weight
which is a variable function of larval size (Beyer, 1980; Beyer and
Laurence, 1981).

. B = coefficient of digestion, a variable changing with larval size
based on nitrogen budget data (Buckley and Dillman, 1982) and from
Beyer and Laurence (1981).


35

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“[PUaYIOSL p'Z aunzesadwaz uazey
quedij1uBb1s (12919819838 saq0

“W pb Yadap wWOI30q *H,15,49 ‘N.00 ob “AND OL9L ‘OR6L ‘
uap 4932346 40 0°] Xapul eI1stL0H

2 AeW ‘ep uorqers ‘20-08 PHEIAG
“Pedr SUES UL Aj Snoauez[MWLS PaII2[ [02 | OE PUe O'R ‘Z°L JO YOea saqedL[dar aAlam]

“quasaid Sensei propes

“saqe21 [dau uaamjaq uopbequ0>

“yueg Sab4089 uo Bul {dues UOIxUeLd aJas9Sip aLers [LeU “LL atqeL


39

NO, COPEPODS / m3

10° 70" 102 10° 30% 10°
f 7 T 7 T 1
NO GADID LARVAE /100 M3
70° 10! 10? 10°
i 1 i} 1
TEMPERATURE (°C }
0° 5 10 15
Ui T 1 rT T TT T T t TT T
10K \
‘
\
L. a
20 |—
= 50;— “o
L ¢  Temperature—
N
x 40-—- “S Larvae
b \
a r \, '— Pseudocalanus
Wo50- \
a \
V
{ 1
1
/
60-- /
a
= /
/
f
70 {— ’
" Moc 194
80
Figure 4. Vertical distribution of gadid (haddock and cod) larvae and

dominant copepods (Calanus finmarchicus, Pseudocalanus sp.)
in relation to thermocline on the Southeast Part of Georges
Bank before storm. (MOCNESS-1m, 0.333-mm mesh, 21 May 1981,
2303-2358 D.S.T. 40°55'N, 67°16'W. Bottom depth: 78-80 m).
Note different log-scales used for copepods and gadid larvae.



68

because of reported differences in behavior of the larger
larvae (Wiborg, 1960; Miller et al., 1963). Their mean

day and night abundances within 10 m sampling strata over

a 54h period are shown in Fig. 9. The size range of larvae
collected by the 1 m MOCNESS are essentially the same as
that collected by the él om bongo net shown in Figs. 7 and
8. Both size groups of cod larvae are broadly distributed
throughout the water éoLumn with weighted mean population
depths between 30 and 40 m in water 66-70 m bottom depth.
More cod larvae are usually caught by night than day, es-
pecially in the upper 20 m. A significant vertical displace-
ment between day and night is shown by the larger size group.
Night mean. abundance of these larvae in the upper 20 m of
the water column (mean length of 11 mm) was greater by a
factor of 14-26 than that of the mean day abundance.

By mid-May, the water column was well-stratified at
bottom depths greater than 60 m. At the first time-series
station (80 m), 21 May, the surface temperature approached
10°c, a strong thermal gradient (0.75°C/m) was evident be-
tween 15 and 20 m, and below the thermocline the water was
5.9°C to bottom (refer Pig. 3). Both net- and nanno-phyto-
plankton biomass were reduced to <l mg chl a/m, but showed
a slight increase in the nanno-phytoplankton biomass above
20 m. Both haddock and cod larvae were almost exclusively
confined to the upper 20 m of the water column with maximum
abundance within the thermocline (Figs. 10 and 11A, moc 191).
An intense storm swept the area with high northeasterly winds,
35-40 knots (18-21 m/s), and upon resuming operations at: the
same site several days later on 24 May, it was evident that
the water column was well-mixed, c. 7°C isothermal. Phyto-
plankton biomass was uniformly dispersed from top to bottom.
Haddock and cod larvae now were broadly distributed through-
out the water column with a weighted mean depth between 30 and
42 m, although there was a suggestion of an upper shift in
the vertical distribution of larvae during the night (Figs.
10 and 11A, Moc 193-207). On 28 May, a single MOCNESS haul -


FREQUENCY

180

80

78

130°--

cop
DAY 14

37% SURVIVAL
6 PREY/LITER
X90, 2243.6

§ #8 & &

LARVAL WEIGHT (ug)

825 -

g
@



FREQUENCY

123

25
HADDOCK-758ug

aut

1s f

Wr

PREFERRED PREY®6. Jug

sk |

: Lf

_ + ef © & 8 & 8 8 B
PREY WEIGHT (ug)

Figure 17. Frequency histogram of the distribution of prey size about
the preferred prey size for a 750 ug haddock larva.


NUTRITION AND TROPHODYNAMICS OF LARVAL FISH: REVIEW,
CONCEPTS, STRATEGIC RECOMMENDATIONS AND OPINIONS# =>

Geoffrey C. Laurence
National Marine Fisheries Service
Northeast Fisheries Center
Narragansett, RI 02882 1199

I INTRODUCTION

A significant proportion of the natural variability in fish production and
resultant stock size is believed to be the result of changing recruitment to a
fishery. Recruitment is, in turn, thought to be directly related to the
survival success of the early life stages. The ability to understand the
causative factors and predict early life survival and relate it to recruitment
would be a paramount step toward effective fishery management schemes.

In a consideration of the early stages, particularly the larval, it has
almost become axiomatic that the trophic (feeding) relationships of predation
and starvation with their inherent biological components modified by
environmental physical factors are the basic controlling principles of
survival. It is the purpose of this document to explore the state of knowledge
of larval feeding as it relates to success (growth and survival) or failure
(starvation and death) under the general heading of larval fish nutrition.

II STATE OF KNOWLEDGE AND REVIEW

Because of the length restriction of this paper and the desire to use a
good portion of it for concepts, opinions, and recommendations, I will highlight
our present state of knowledge concerning larval feeding with reference to a
number of recent review or workshop contributions for more detail. A workshop
on approaches to larval fish feeding studies (G. Laurence and E. Houde,
convenors) was held at this year's 6th Annual Larval Fish Conference, CBL,
Solomons, MD. The appended outline (Appendix) used to prepare the program for
that workshop gives a reasonably detailed presentation of factors involved in
larval feeding. Additionally, 2 recent review publications (Hunter, 1981, and
Theilacker and Dorsey, 1980) as well as the original larval fish review by
Blaxter (1969) serve as a compendium from which much of the review part of this
paper is drawn.

1, contribution to: Fish Ecology III, Cooperative Institute of Marine and
Atmospheric Studies, University of Miami; September 6-10, 1982; Brian J.
Rothschild, University of Maryland, and Claes G. H. Rooth, University of Miami,
Convenors.

2This is MARMAP Contribution No. MED/NEFC 82-50.
3this is a University of Miami Technical Report No. 82008.


FREQUENCY

125

25-7

28

| la

LARVAL COD
Xe43, 626.0

rT)
~

8

DRY WEIGHT (ug)

Figure 19. Frequency histogram of a generated normal distribution of
larval initial hatching weights based on empirical laboratory

measurements for cod.


43

Flgdevigen rapportser., 1, 1984. ISSN 0333-2594
The Propagation of Cod Gadus morhua L.

LARVAL FISH TROPHODYNAMIC STUDIES ON GEORGES BANK: SAMPLING
STRATEGY AND INITIAL RESULTS

R. G. Lough

National Marine Fisheries Service
Northeast Fisheries Center

Woods Hole Laboratory

Woods Hole, Massachusetts 02543 USA

ABSTRACT

Lough, R. G., 1984. Larval fish trophodynamic studies on
Georges. Bank: Sampling strategy and initial results.
In: E. Dahl, D.S. Danielssen, E. Moksness and P. Solem-
dal (Editors), The Propagation of Cod Gadus morhua L.,
Flgdevigen rapportser., 1, 1984:

A sampling strategy is outlined to serve as a framework
for determining the fine- to micro-scale vertical distri-
bution or fish larvae and their prey on Georges Bank in a
single vessel, interdisciplinary mode of operation. A major
objective of this sampling program is to characterize the
development and temporal-spatial variability of these dis-
tributions to evaluate growth and survival of larval popu-
lations. The operational plan, sampling gear and instru-
Mentation, as well as special techniques employed are dis-
cussed in terms of the usefulness of the parameters measured.
Initial results are presented from a two-part study conducted
in April-May 1981, focused on haddock (Melanogrammus aegle-
finus L.) and Cod (Gadus morhua L.) larvae.

In April, a gadid egg patch with recently-hatched larvae
(c. 91% haddock) was located on the southeastern part of
Georges Bank, between the tidally-well-mixed front (c. 60-m
isobath) and the shelf/slope-water front (c. 100 m). The
water column along the southern flank was still well-mixed
in April and the larvae were broadly distributed with a
weighted mean depth between 30 and 40 m. Density of their
dominant copepod prey was relatively low near the surface
(<3 prey/l) but increased with depth (5-10 prey/1).


vi

Hydrography of Georges Bank ..+ssssceseceeesecueueaeas seeeeeeeee . 48
Objectives and Sampling Strategy wee ee eee e tenn eect eee ee nenen: 50
Methods cece eee eeeeeeaeenneenanenees Le eceeeeecenceeseseeeneas 53

‘Gear, Instrumentation, “and 1 Special Techniques

“Bongo- Net Sampler . :

MOCNESS ..eeeeeeeeeeeeeneeenes Leet eeeeeeeeeeneee nee eiuince SA
Plankton PUMP ..scceccceeceeceteeebereteeer ee enneeneeeeee 54
CTD - Fluorometer ....ccc cece ened cee ee ces eeeneeeeetoene 55
Real-Time Zooplankton Processing ...ceeeeceeeeeeereeerees 56

Larval Condition and Growth Indices .....ssseseceeeeeenee 57

' Prey Selection

Field oper tional Plan etereeeteegs sevens Veceseueeeesuns 57

CTD -. Fluorometer Cast ......seeee Wenn dence esececncereeee 59

MOCNESS 1 m Haul ....... eee e eee nee eennee eens seneeene 59

¢ Plankton Pump Cast .....eceeeeeceeeeeeee eens eeeeeweceees 59
- MOCNESS 1/4 m Haul .ccscccccccnccecececeeeescetennseecenes 60
Results and Discussion ....sseeeeeeeeeeeees toe eee ccencoreeeseveees 60
Acknowledgements seen eee eee e enter eee e eee eee e eee ene e teen eeenes 78
References oeicsscseeseees sec e nena eens eee sees eee ene e eee e este eee 78

A REPORT ON THE DEVELOPMENT OF STOCHASTIC MODELS OF FOOD
CimiTeD GROWTH AND SURVIVAL OF COD. AND HADDOCK LARVAE
ON GEORGES BANK: hae nenee tenes seen ee eeeeeeeaeeeeeeeeeteeenes 83

Introductic on ..

Method for Transferring a Normal Probability Distribution a
to a Distribution with Known Mean and Variance . 87

Stochastic Model EVOIUtION ....ccccecceceeereeeteeeteteeeeeenaees


60

MOCNESS 1/4 m haul

The objective of this haul is to determine the vertical
distribution and abundance of micro-zooplankton retained by.
64-pm mesh nets aver the vertical distribution range of fish
‘Larvae. About 20-36 m? of water is filtered by each net
(1-3 min) within an integrated strata of 10, 5, or 2-m
resolution (94-170, m horizontal distance traveled).

Following the fine-scale station observations, the grid
of stations may be resurveyed and new transects added in the
direction of the residual current, or MOCNESS l0-m hauls may
be made on a transect of stations in the study area. The
10: m MOCNESS is used to determine the vertical distribution
and abundance of potential micro-nektonic predators and
post-larvae with 15 ar 25 m resolution, each net filtering
7000-14000 m3 of water in 15-30 min (705-1410 horizontal
distance traveled). A Lm MOCNESS haul usually is made
immediately before or after to collect larval fish or other
food prey-

RESULTS AND DISCUSSION

Some of the initial results are presented here from a two-
part study conducted aboard R/V ALBATROSS IV, 15-30 April
1981 and 18-30 May 1981. On the April cruise a well-defined
concentration of gadid eggs was located on the southeast part
of Georges Bank between the 60 and 100 m isobaths by the
bongo sampling grid of stations (Figs. 4-8) -, Recently-hatched
haddock and cod larvae (3~5 mm SL) were found most abundantly
towards the southeastern part of the grid and a ratio of their
abundance indicated that about 91% of the gadid eggs. were had-
dock, the other 9% cod. The majority of eggs were at a late
stage of development (Colton and Marak, 1962) and were esti-
mated to have been spawned 8-10 d previously in the 6°C water.
Early stage eggs were more abundant to the northeast near the



15

Johnson, G. D. 1978. Development of fishes of the mid-Atlantic bight. Vol.
Mv. Carangidae through Ephippidae. U.S. Dept. of Interior, Fish Wildl.
erv.

Jones, R. 1973. Density dependent regulation of the numbers of cod and
haddock. Rapp. P.-v. Reun. Cons. int. Explor. Mer, 164:156-173.

Jones, P. W., F. D. Martin, J. D. Hardy, Jr. 1978. Development of fishes of
the mid-Atlantic bight. Vol. I. Acipenseridae through Ictaluridae. U.S.
Fish and Wildl. Serv., Dept. of Interior.

Kramer, D. 1960. Development of eggs and larvae of Pacific mackerel and
distribution and abundance of larvae 1952-1956. U. S. Fish, Wildl. Serv.,
Fish. Bull., 60:393-438.

Kramer, D. and J. R. Zweifel. 1970. Growth of anchovy larvae (Engraulis
mordax Girard) in the laboratory as influenced by temperature. Calif.
Coop. Oceanic Fish. Invest. Rept., 14:84-87.

Lasker, R. 1962. Efficiency and rate of yolk utilization by developing
embryos and larvae of the Pacific sardine Sardinops caerulea (Girard).
J. Fish. Res. 80ard Can. 19:867-875.

1964. An experimental study of the effect of temperature on the
incubation time, development and growth of Pacific sardine embryos and
larvae. Copeia 2:399-405.

1975, Field criteria for survival of anchovy larvae: the relation
between inshore chlorophyl1 maximum layers and successful first feeding.
Fish. Bull. U.S., 73:453-462.

+ 1981. Factors contributing to variable recruitment of the
northern anchovy ( Engraulis mordax) in the California current: Contrasting
years » 1975 through 1978. Rapp. P.-v. Reun. Cons. int. Explor. .Mer

Lasker, R., H. M. Feder, G. H. Theilacker and R. C. May. 1970. Feeding,
growth and survival of Engraulis mordax larvae reared in the laboratory.
Mar. Biol., 5:345-353.

Last, J. M. 1978a. The food of four species of Pleuronectiform larvae in
the eastern English Channel and Southern North Sea. Mar. Biol. 45:349-368.

1978b. The food of three species of Gadoid larvae in the Eastern
English Channel and Southern North Sea. Mar. Biol. 48, 377-386.

Laurence, G. C. 1969. The energy expenditure of largemouth bass larvae,
Micropterus' salmoides, during yolk absorption. Trans. Am. Fish. Soc.
98:398-405.

. 1971. Digestion rate of larval largemouth bass. New York, Fish
Game J., 18 (1):52-56.


58

40-50 stations, 5 miles apart, is occupied within a 2d
period to characterize the larval fish, plankton, and
temperature-salinity field in an area sufficiently large

(c. 30 x 50 miles (56 x 93 km]) to encompass the antici--
pated dispersal of plankton having a residual drift of

4 miles/d (-7-km/d) in which the fine-scale station studies
will be carried out aver 4-6 d. The survey grid usually

is situated sa that stations overlap the shoal front of the
well-mixed waters (<60 m) and the southern shelf/slope-water
front (c¢. 100 m) bounding the stratified waters on the bank.
A bongo haul’ and XBT drop are made on each grid station, and
surface temperature, salinity and fluorescence are monitored
continuously.

Based upon real-time sample analyses made during the grid
survey,-a@ station is selected for the fine-scale time-series
observations and a drogue is deployed at the depth corres-
ponding, ideally, to the weighted center of gravity of the
larval population. On one occasion, a drogue was deployed
with an array of vector-averaging current meters (VACM)
positioned to measure current velocity and temperature at
selected depths to determine shear in the water column.

On station, the sampling scheme used is a combination of
fine- to micro-scale observations in order to sample fish
larvae and their prey, and other environmental parameters.
This scheme allows 2-4 observations of each kind during a
tidal period (12.4 h)-~ On each drogue-follower station,
time~series observations are made for a minimum of 30 h and
sometimes as long as 50 h encompassing 2-4 tidal periods.
A complete series. of observations is made every 6°h.in the
following sequence: CTD-fluorometer cast, MOCNESS 1-m haul,
plankton pump cast, CTD-fluorometer cast, and MOCNESS 1/4 m
haul.


FREQUENCY

134 =:

28

15 -

cop

DAY 42

27% SURVIVAL

8 PREY/LITER

%n968, 94815. 7

Fit ; C]
| a € & & &

LARVAL WEIGHT (ug)

Figure..28. Frequency. -histogram-of the. weight distribution from.a.3:
hastic .element: model -run-at.:asprey-density of 6 liter”
for cod: larvae-at 42,days:after-hatching. ~-:)

1



51

Supportive evidence for the first four hypotheses can be made
by field observations; the fifth hypothesis must be investi-
gated through probabilistic food encounter models or quasi-
realistic laboratory experiments. The thermocline is poten-
tially important because bialogical productivity appears con-
centrated near this layer and larval and juvenile haddock
appear ta be uniquely associated with it (Miller et al.,
1963; Colton, 1965, 1972; Houghton and Marra, 1983). During
spring when recently-hatched larvae are present, the seasonal
thermocline is beginning to form, vertically stratifying the
water column (>60 m bottom depth). The presence of a dis-
continuity layer resulting in a greater degree of structure
and patchiness qf the plankton may be critical to the sur-
vival of larvae in this region. There is a need to measure
prey availability prior to, during, and after thermocline
formation in order to evaluate the importance of this phe-
nomenon.

A. field program addressing these hypotheses requires
sampling on spatial scales ranging from centimeters to kilo-
Meters and temporal scales from minutes to weeks. Consider-
able emphasis is given to the smaller scales of pattern as
individual larvae encounter their prey on the micro-scale
level (1 cm to 1m); however, a larva's swimming capabilities
soon develop to where it can migrate vertically 10's of
meters in a matter of hours. Sampling larvae at the popu-
lation level requires discrete samples at the fine-scale
level (1m to 1km), for example, to resolve vertical migra-
tion patterns. To define a coherent patch of larvae, or to
sample post-larvae or larger predators, requires sampling
on a coarse scale (1 to 100 km). Synoptic, three-dimensional
sampling of the variable fields is needed, but our present
technology and sampling techniques usually only permit quasi-
synoptic sampling of the parameters or organisms of interest
(Kelley, 1976). The sampling gear used should be directed
towards collecting discrete samples of the target organism


0.0046 calug-! (Unpublished Narragansett Lab data)

Larval haddock tissue

"

Copepods (larval prey) = 0.0052 calug-! (Laurence, 1976)

Metabolism (u202) = 0.005 cal (standard oxycaloric equivalent)
The larval haddock weight-length equation is:

W = 0.04424-476 (Laurence, 1979)

Larval Haddock Feeding Requirements

Table 9 presents upper and lower limit values of feeding related parameters
for haddock larvae of three different sizes. The most important parameter from
this Table is R the required number of ingested prey day-!. The absolute value
of the range decreases with larval size because the preferred prey size increases.

Larval Haddock Swimming Abilities and Searching Behavior

The visual field and perception distance for larval haddock is important in
the calculation of prey encounter rates.

Visual Field = 2/3 7 62

where 6 is the perception distance which is approximately 0.5-1.0 times the
body length (BL) of the larva (Beyer and Laurence, 1981).

Larval swiming speed is also a determinent of prey encounter rate.
Larval linear sustained swim speed = 1.0-2.0 BL sec-! (Laurence, 1972).
The total volume of water searched day~] by a larval haddock then becomes

the product of the visual field times the linear distance swam = 2/3 7 64-Dis-
tance swam unit time-l.

Larval Haddock Food Encounter

; All the above parameters and relationships have been used to calculate the
important factors in larval food encounter and searching capabilities. These
are presented in Table 10 for three larval haddock sizes.

The linear distance swam, if a larva decided to swim in a straight line,
at the sustained swim speed is in the order of hundreds of meters day-1. This
assumes a 12°h swimming day because larvae are visual feeders and become
relatively inactive at night.


Table 1. (continued)

25

Yolk_absorpt ton Onset_of feeding Ireversible starvation Metamorphosis
Nays from Tays tron Ta) Trays from hatching Days“trom Length
hatching °C hatching cb) Mays from Yolk Abs. °C hatching °C (ns)
45 10 45 0 14
Yolk absorption
6-10 7-11 46 7-10 6-8(9) ell 7d 9-13
3 8 8 a 5-70) 8 58 8 6.549
346 4 16 6-7 1 47-86 16 1s
7 42-55 10-12 9-10
3 8 2 8 343.5 Ey 16 28 45
3 2 3 10
2 8 1S 28 2.5 28 9-11 23-29 7-9
6 12 4 7 3(b) 7 52 7 10
7 7 “4 7 g(b) 7 42-89 1 19
6 (Firth 8 2-6 (Firth a 6(b) (Firth of Q-12 112-168 B12 30-40
of Clyde) of Clyde) of Clyse)
15-20. (W. 15-20 (Baltic) 12-228 8
Raltic)
45 16 45-50 31-35
4 6 4 15-16 2,5(0) 16.5 50-60 34-40
4.5(b) 15
3 18 45 B 4s 18 32
(3.5:6.8)
3 19 222.5 19 2b) 19 Ey 15
a a6 3.5 16
5 as 2.5(b) 18 40 11-16



FREQUENCY

-
a

mm
a

145

ee“ INITIAL WEIGHTS OF

HADDOCK

SURVIVORS FROM 18008 vrs fh
15 PREY/LITER : :
KeQ7. 148.8

\A
SANA

AANA
N

AXA

R 8 8
LARVAL WEIGHT ug)

108
118
120

Figure 39. Frequency histogram of the distribution of initial weights of
the surviving haddock larvae from Figure 37. ;



45

At the Northeast Fisheries Center (NEFC), the Marine
Ecosystems Division is conducting a broad-based research
program (MARMAP) on the Continental Shelf, involving both
monitoring and process-oriented studies, directed towards
a better understanding of the recruitment process (Gross—
lein et al., 1979; Sherman, 1980). In the last decade,
process-oriented studies have been carried out by.the NEFC
in the Georges Bank area addressing the recruitment problem.
The first major study is represented by the autumn 1978
Larval Herring Patch Study which was conducted as an inter-
national, multi-ship, multi-disciplinary experiment (Lough,
1979). The primary objective was to define and follow a
patch (homologous cohort) of herring larvae as a dissipative
feature to gain a better understanding of the physical pro-
cesses affecting its dispersal. The sampling strategy was
designed to provide short-term estimates. of larval growth
and mortality in relation to the prey-predator field as the
patch advected. More recent studies have been conducted on
haddock and cod larvae since spring 1980 in a single vessel,
inter-disciplinary mode of operation. Most of the sampling
effort in this mode is to determine the fine- to micro-scale
vertical distribution of larvae and their prey (copepods) in
well-mixed and stratified waters. A major objective in this
case is to characterize the development and temporal vari-
ability of these distributions for use in simulation models.
These studies require different sampling strategies within
the constraints of available resources to meet the desired
objectives.

Each sampling strategy must be uniquely designed for the
specific objectives and hypotheses investigated, taking into
account the peculiarities of the target species and its bio-
logical and physical environment. However, as an investi-
gation of larval fish growth and mortality is inherently
complex, involving the intimate interaction of three trophic
levels simultaneously (Shepherd and Cushing, 1980; Laurence,
1981), a multi-faceted sampling strategy is required to


11

Another significant problem is a general failure of physical oceanographers
and biologists to communicate and interact in the area of early life survival and
recruitment studies. Most biologists feel that physical factors are extremely
important in influencing biological events. Circulation patterns on the
Macroscale level and such processes as boundary or frontal exchange, thermal
inversion and double diffusion on meso and microscales could be prime factors
affecting broad scale distribution of fish larvae as well as the small scale
heterogeneity involved in individual larvae meeting contagiously distributed prey.

Differences in training and background may cause some of the dichotomy.
Nevertheless, with few exceptions that I can see, biologists dealing with early
life stage research have apparently failed to convey the essence of their
problems and importance of physical factors to oceanographers even when they
work in the same organization; while, at the same time, oceanographers generally
have treated these particular biological problems as lower priority, especially
those dealing with small scale phenomena. The best solution for this communica-
tion problem is for astute program managers to use a big club.

A second aspect to the problem is available instrumentation and technology.
Current means to measure and record physical parameters are more advanced than
those used for biological. It's basically nets vs. electronics. This gap is
narrowing, however, as biologists become more sophisticated in their needs. It
should become a non-problem provided funds are allocated to the necessary
technological development.


FREQUENCY

28.

15

-
a

132°

coo

DAY 28

27% SURVIVAL
8 PREY/LITER
X=318, 82322. 0

,_[] 4
sg &§

LARVAL WEIGHT (ug)

2408 F
2088:
3288

_ Figure: 26.:Frequency:-histogram-of- ‘the weight <distributton: from a°3:*
‘stochastic: element’ model: ‘run at rey: dénsity of 6 liter”
for cod ‘larvaeiat: 28° days “after hatching. mt

-1



78

observations for evaluating the causes of mortality. Special
effort is made to make our program truly interdisciplinary by
linking laboratory studies and model simulations with field
observations.

ACKNOWLEDGEMENTS ~

The core of our research program described in this report
is based on staff biologists and oceanographers from various
investigations within the Marine Ecosystem Division of the
Northeast Fisheries Center. Other individuals intimately
involved in the planning, execution, or data analysis are:
Geoffrey C. Laurence, John R. Green, Laurence J. Buckley,
Donna.S. Busch, David G- Mountain, Ronald J. Schlitz, David
C. Potter, George R. Bolz, Rosalind E. Cohen, Joseph Kane,
Philip R. LeBlanc, Peter J. Auditore, Bruce Burns, Jacquelyn
Anderson, and Harold G. Merry. This report is MARMAP Con-
tribution MED/NEFC 83-31. Reference to trade names does not
imply endorsement by NMFS, NOAA. Special thanks to Cheryl D.
Windsor for typing the manuscript.

REFERENCES

Aiken, J., 1981. A chlorophyll sensor for automatic, remote,
operation in the marine environment. Mar. Ecol. Prog.
Ser., 4: 235-239.

Beardsley, R-C., Boicourt, W.C. and Hansen, D.V., 1976.
Physical oceanography of the Middle Atlantic Bight.

Am. Soc. Limnol. Oceanogr. Spec. Symp., 2: 20-34.

Beyer, J.E., 1980. Feeding success of clupeoid fish larvae
and stochastic thinking. Dana, 1: 65-91.-

Beyer, J. and Laurence, G.C., 1980. A stochastic model of
larval fish growth. Ecol. Modelling, 8: 109-132.

Beyer, J. and Laurence, G.C., 1981. Aspects of stochas-
ticity in modelling growth and survival of clupeoid fish
larvae. Rapp. P.-v. Réun. Cons. int. Explor. Mer, 178:
17-23.

Bolz, G.R. and Lough, R.G., 1983. Larval Atlantic cod (Gadus
morhua) and haddock (Melanogrammus aeglefinus) growth on
Georges Bank, Spring 1981. Fish. Bull., U.S., 81: (in
press).


32

Table 8. Caloric and ash values for some North Atlantic copepods. Species
are recorded in order from largest to smallest mean value under each
category. Those species side-scored have similar means (Duncan's
New Hultiple Range Test, P=0.05). (Table 1 from Laurence, 1976)

. Mean Standard
Species Deviation
cal/g dry weight

[ Gelenus finmarchicus 6425.1 £187.0
Tortanus discaudatus 5398.3 + 14.6
Centropages typicus 5244.7 +183.3
Acartia tonsa 5160.0 + 78.8
Pseudocalanus minutus 5070.9 4181.7
Centropages hamatus 4998.6 $246.3

[ Temora longicornis 4466.3 + 92.8

L——

cal/g ash-free dry weight

[ Calanus finmarchicus 6835.2 4191.2

[Acartia tonsa 5664.1 + 86.6
Tortanus discaudatus 5642.0 + 15.3
Pseudocalanus minutus 5541.9 +198.6
Centropages typicus 5503.4 £192.3

| Centropages hamatus 5212.3 +256.9
Temora longicornis 4984.7 103.6

% ash

[Temora longicornis 10.40 + 0.16
LL

[Acartia tonsa 8.90 + 0.16
Pseudocalanus minutus 8.50 + 0.11
[ Calanus finmarchicus 6.00 + 1.82
Centropaages typicus 4.70 + 0.28
Tortanus discaudatus 432 + 0.07
Centropaaes hamatus 4.10 + 0.13


73

A conservative estimate of prey density in the field has
been made by. summing the appropriate life stages of Pseudo-
calanus and Calanus in the same prey size classes used above
in Fig. 13 from the 1/4 m MOCNESS hauls made during the April
and May station time-series. A comparison of various sampling
gear and net mesh sizes indicated that the naupliar and cope-
podite stages of these two species were quantitatively sampled
by the 1/4 m MOCNESS. In well-mixed waters, a coefficient of
variation of 26% was estimated for the total copepod nauplii
count from net samples within a selected stratum. In Figs.

14 and 15 the mean number of prey per liter within each depth
stratum is plotted by width class. In April (Fig. 14), the
vertical distribution of prey was low near the surface and in-
creased with depth. The dominant and most important size
class of prey, <0.19 mm, had <3 prey/l above 20 m depth and
5-10 prey/l at greater depths. The weighted mean depth of the
small cod larvae in this same series of hauls was between 30
and 40 m- In May (Fig. 15A), the single 1/4 m MOCNESS haul

NO./L
Or T T

ml
PO 26 APRIL '8t

e MOC 179-181
20 ji iN
~n i e
€ fl tl
1
= 40 '
SOU
Q t
60 o.Ue
60 ri, \y \e
,. NN
r @—@TOTAL PREY
o=-0 20.19mm WIDTH
80“ e—2 0.20-0.29 mm

o—e 0.30-0.45mm

Fig. 14. Vertical distribution of larval prey field collec-
ted by 1/4 m MOCNESS (64 um mesh) on the Southeast part of
Georges Bank, 28 April 1981.


50

‘Gulé Stream warm-core eddies moving near the southern
edge of the bank may play an. important role in the movement
of shelf/slope-water, both on and off the shelf, and the
entrainment of organisms residing there (Lough, | 1982; Joyce
and Wiebe, 1983) . 2.

Objectives. and Sampling Strategy

The main focus of the haddock-cod study to-date is to
describe the spatial-temporal variability of larvae and
their prey (copepods) during their first month of life on
Georges Bank. Observations also. are made to better under-
stand factors governing their production and to survey
post-larvae and potential predators of larval fish by
sampling the macro-plankton and micro-nekton components
on the same cruise. Our sampling program is presently
designed to. investigate the following hypotheses which we
feel are important in order to understand the feeding
dynamics ‘and survival of larvae retained on Georges Bank:

1. Growth of larvae is related to the density of micro-

zooplankton prey.

2. Micro-zooplankton are concentrated in areas of re-

latively high phytoplankton biomass.

3. Micro-zooplankton are contagiously distributed

; (clumped) -
4. Stratification of the water column along the
southern flank of Georges Bank in late spring
“s serves. to .concentrate _ zooplankton and fish larvae
vertically.

5. Feeding» success is a stochastic process of random

encounters with ‘patchy’ prey.


A) ‘STRATIFIED

STATION
. . NOLL ;
- gM, 20.40 60 Q 10 20
PCT?
; x —~TM, if e
20 b/ ££, 2obi/ \  {
(VO Tif
eo be go aoe
- FOF. 40H
{ ‘S; LJ d f
le Vy
A uit
60! \ 60 |!
 &e Ss leo oO ©
el oT) ap May tat Hl | | 24-26 May's!
. MOC 192 MOC 194-208,
z 80 gol
&
x @—©@ TOTAL PREY
wR O=9 £0.19mm WIDTH
& e—e 0,20-0.29mm
x —0.30-0.45mm
B) WELL-MIXED STATION
NOSL
to) 10 20 30
7 TT qT
fF ES
L? ¢ Oe
oe oO olUw®
HY a é
20% 7 Pf
es
ls 6 Noe
LY ok
40 fi] iI
y 27 MAY '81
sol MOC 210-216
Fig. 15. Vertical distribution of larval prey field on

(A) stratified station before and after storm, 22-24 May
1981, and on (B) shoal, well-mixed station, 27 May 1981.


109

T T 8
oN
“oN
lan
cg
“d
L € 470
=
=
VY
aN Van
L Y 40
Q a)
: Ne
| c
Y “4
an €
>< =
r Lu {T |
ic) =
iS
° e A
< |
Q
3 6 Co TOL ea
Q (es)
OO a °
x< © I
= OU mo
rn 1 2
“4 jee) oO wv ian] ies]

‘'NOILVYZITILN %

Figure 3. Relationship of the fraction of food ingested that is
utilized in the digestion process and larval size for cod and
haddock larvae. From Beyer and Laurence (1981) based on
nitrogen budget research of Buckley and Dillmann (1982).


DRY WEIGHT (ug)

150

112

As HADDOCK WeWmin€XP (0. 02261)

-—>- O COD WeWminexP<o, 02627)

Figure 6.

10F
20
- 30
40

DAYS

Minimum barrier or the smallest size larvae alive at a given
time for cod and haddock larvae in laboratory experiments.



19

APPENDIX
Approaches to Laboratory Studies of Feeding

of Fish Larvae

I. Logistics
A. Food Collection or Propagation
1. Techniques
2. Systems
3. Cost-Effort
B. Rearing System Design and Development
1. Open vs. Closed
2. Freshwater vs. Marine
3. Tank or Wall Effects
C. System Hygiene
1. Physical (vacuum, scraping, filtering, etc.)
2. Chemical (antibiotics, etc.)
II. General Food Requirements
A. Preferred Foods
1. Natural (trophic level) foods
2. Atypical Natural Foods (i.e. brine shrimp, rotifers, etc.)
3. Artificial Foods
a. Microencapsulation
B. Food Densities
1. Naturally Occurring
2. Critical
3. Optimal
4. Fluctuating

5. Measurement (#'s, calories)


. FREQUENCY -

15

18

144

INITIAL WEIGHTS OF...”
SURVIVORS FROM 10808

3 PREY/LITER

Xe5B. 845. 4

LZ

2 8 B
LARVAL WEIGHT (ug)

di Figure 38. “Frequency. histogram of the distribution: of initial weights of
. ‘the Surviving cod larvae from: Figure 36.-

78


xi

LIST OF FIGURES

NUTRITION AND TROPHODYNAMICS OF LARVAL FISH - REVIEW, CONCEPTS,
STRATEGIC RECOMMENDATIONS AND OPINIONS

Figure 1. teenyonsn of larval and prey sizes. (Figure 3 from Last,
_  1978b).

Figure 2. Relationship between prey size and larval size. (Figure 3
. from Hunter, 1981). .

Figure 3. Triotrophic relationship affecting larval fishes.

Figure 4. Vertical distribution of gadid (haddock and cod) larvae and
dominant copepods (Calanus finmarchicus, Pseudocalanus sp.)
in relation to thermocline on the Southeast Part of Georges
Bank before storm. (MOCNESS-1m, 0.333-mm mesh, 21 May 1981,
2303-2358 D.S.T. 40°55'N, 67°16'W. Bottom depth: 78-80 mi.
Note different log-scales used for copepods and gadid larvae.

Figure 5. Vertical distribution of gadid (haddock and cod) larvae and
dominant copepods (Calanus finmarchicus, Pseudocalanus sp.)
on the Southeast Part of Georges Bank after storm. (MOCNESS-
1m, 0.333-mm mesh. 24 May 1981, 1835-1920 D.S.T. 40°55'N,
67°13'W. Bottom depth: 80 m). Note different log-scales used
for copepods and gadid larvae.

Figure 6. Vertical distribution of dominant copepods on Georges Bank.
(Albatross 82-05, May 17, 1982, 1830-1920 D.S.T. MOCNESS-1 m,
0-333 mm mesh, 40°55'N, 67°17'W. Bottom depth: 75.9 m). No
gadoid larvae present. Temperature Ca. 5-6° C isothermal.

Figure 7. Vertical distribution of dominant copepods on Georges Bank.
. (Albatross 82-05, May 15, 1982, 1831-1844 D.S.T. MOCNESS-1
m, 0.333 mesh, 41°14'N, 67°37'W. Bottom depth: 36 m). No

gadoid larvae present. Temperature 6.7°C isothermal.

LARVAL FISH TROPHODYNAMIC STUDIES ON GEORGES BANK: SAMPLING STRATEGY
AND INITIAL RESULTS

Figure 1. Principal haddock spawning area on Georges Bank and
generalized larval drift (indicated by arrows) and areas
where demersal O-group haddock are most abundant 6-8 months
later. .

Figure 2. Schematic representation of the well-mixed and stratified
waters on Georges Bank and mean circulation flow (arrows)
during spring and summer.

Figure 3. Real-time temperature-depth plot of 1 m MOCNESS haul 191. A
solid temperature line is drawn as net is set to maximum
depth and dotted after first net is opened and sampling
sequence begins.


POPULATION SURVIVAL (%)

5
7
65
62
55
5a
45
42
35
30
25
20
15
1g

127

° copu-~——— 0
! HADDOCK e
I
I
t
/
I
|
!
t
I
I
I
r)
/
I
I
!
t
J
|
?
/
2
go L n 1 1 1 1 1
os #8 &§ & & & § 8B

PREY DENSITY (#/LITER)

Figure 21. Simulated population survival at different constant prey
densities for larval cod and haddock. Based on the 3
stochastic element model (version 3).

58


FREQUENCY

135

75

7+

65 +

Le

45+

35 +

257

IS -
WF

HADDOCK

DAY 1

188% SURVIVAL
38 PREY/LITER
X68. 4410.8

e« 8 8 §& 8

a

i's)

a

LARVAL WEIGHT (ug?

Figure 29. Frequency histogram of an initial weight distribution from a
3 stochastic element model run at a prey density of 30
literTM” for haddock larvae.


FREQUENCY

141

15

HADDOCK

DAY 42

37% SURVIVAL

32 PREY/LITER

Yu138B. 221001. 2
WF
st

1 AT 4794 es
; | | ale
8 5

4
2 & & &

LARVAL WEIGHT (ug)

Figure 35. Frequency histogram of the weight distribution from a 3
stochastic element model run at a prey density of 30 liter”
for haddock larvae at 42 days after hatching.

1



34

Table 10. Larval haddock swimming, searching and food encounter.

Larval Haddock Size, Std. Length (mm)

Parameter. 20 ee eee Be 10... —45-.

; Daily Linear Distance

Swam @ 1.5 BL sec-} and

12h Activity (meters) 324 643 972

CM Secu] - 0.75 1.5 2.25
Volume Water Searched

in 12 h Day (liters). 9.5 76.2 257.2
Range of Required

Prey Captures (R) day-! 107-248 47-111 59-143
Range of Required

Linear Swimming Distance

Capture-1 (meters) 3.0-1.3 13.7-5.8 16.5-6.8
Range Required # Prey

Liter-1 if 100% Capture

Rate 11.2-26.1 0.6-1.5 0.2-0.6
Range 10% Capture Rate 112-261 6.2-15.0 2.0-6.0



Table 2.

Table “3.

Table 45°

organisms

Deterministic parameters and output variables at three
constant daily growth rates for haddock larvae. Each  .
‘On.-représents: a specific weight-in the range: from. the.”
initial weight at hatching-yolk~ absorption: “until: 105000" pg.

Relevant “larval ‘gadid parameters for: Georges. Bank= (from Smith:
et al. 1979, 1981 and Sherman et=al. 1983). ;

Sunimary:of. bottle-samples {all sampler sizes,*depths, ~ :
stations) -- EVRIKA-80-02 relevant larval cod-and haddock prey



Table 4,

28

Field concentrations of larval fish food organisms,

(Table 10 from Houde, 1978),

Reference

Place

Organisms

Concentration

Purdick (1969, cited in May,

1974

Duka (1969)

Mikhman (1969)

Hargrave and Green (1970)
Reeve and Cosper (1973)

Heinle and Flemer (1975)

Houde (unpublished data)

Kaneohe Ray, Hawati

Sea of Azov

Gulf of Taganrog,
Sea of Azov

Two eastern Canada
estuaries

Card Sound, South Florida

Patuxent River estuary

Riscayne Ray, South Florida

copepod nauplii

Acartia clausi
nauplii

Other copepod nauplii
and copepodites
Total

Early stages of
copepoda

Copepod nauplii and
copepodites

Copepod stages
20-200 um in breadth
Tintinnids

Eurytemora affinis
nauplii and copepodites

Copepod nauplii and
copepodids <100 um
in breadth
Tintinnids

59-100/1 common
200/1 sometimes present

62-65/1

>30/1
90/1

39-546/1

>60/1

range 23-209/1 mean
for 28 collections 72/1
range 40-369/1

>100/1 frequently

>2,000/1 occasionally

usually 50-100/1
frequently >100/1



108

1@! PREY WIDTH (mm)
r N

t w
vl ne) un ot) ul
aK -@— T 7 T
\ 0
‘XO
“eho a
e Oo
ot 4
Se
-
mM oF 4
5 Ve ie)
4 Oo
mF \ 4
‘\ @ 0
> <i
5 es) | >
3, fT Io 10 |
° oS
Qo 80 \
me TM— i} AO
ar com ON 7
t te
Q | 4
r - Ww
W ine)
x< ><
rh 1 1

Figure 2.. Relationship of mean preferred prey size and larval size for
fat 30 haddock larvae. Based on empirical data from Kane
1983). .


so:
BRw = Ingested food that is digested

and

(1-8)Rw = Defecated portion of ingested food

a = Fraction of digested food lost in chemical and physiological
processing; a constant 0.40.

Thus:

(1-a)BRw q)

is available for growth and metabolism

where
KW" = Metabolism day-! with
K = Coefficient of metabolism (a variable changing with larval
activity level (Beyer and Laurence, 1980, 1981)
n = 0.671 (a constant exponent, Laurence, 1978), and W is larval
weight.
Thus:
(1-a)@Rw = 4G + KW" (2)

is the mass balance equation

and

— AG + KW
(12a) au (3)

is the solution for the number of food organisms required day-!,

Miscellaneous

The above relationships need to be converted into a standard unit of
measurement for calculation purposes. The calorie is that unit and conversion
factors are as follows:


There are a number of factors related to food and feeding which directly
affect larval survival. .They are: 1) duration of development from the embryo
stage to the time when the first feeding responses occur, 2) the preferred food
species and its abundance and distribution, 3) the behavioral relation between
the larva and its prey, 4) the success of feeding responses, 5) the swimming
ability of larvae in search of food, and 6) the required food ration for growth
and metabolic expenditure.

Maternal inheritance and temperature control the initial amount of endogenous
yolk reserves and the developmental rate, respectively, prior to external feeding.
The efficiency with which yolk is utilized probably is an important determinent
of early survival ‘since size and condition of larvae will affect their ability
to begin feeding. Presumably, larger larvae produced by more efficient use of
endogenous reserves will have an advantage over smaller larvae in foraging
ability. Blaxter (1969) noted for a number of species that development at
different temperatures can produce larvae with morphological differences as well
as different percentages of yolk and larval tissue at hatching and the initiation
of feeding. Furthermore, a number of authors (Gray, 1926; Smith, 1947; Lasker,
1962; Toetz, 1966; Laurence, 1969, 1973) reported potential energy deficits with
not enough yolk to provide for normal requirements before the ability to feed on
external prey organisms. Another aspect is the ability to withstand starvation
during the period when feeding commences if food is initially unavailable. This
has been termed "point of no return" or delayed feeding. Table 1 from Theilacker
and Dorsey (1980) presents an extensive summary of the known information about
these early developmental factors.

Preference for certain food organisms by larvae has been indicated in
numerous field studies (Ogilvie, 1938; Marak, 1960; Last, 1978a,b). This
selective feeding is influenced by the size of the larva and its mouth in relation
to prey size (Hempel, 1965; Sherman et al., 1981). Figure 1 from Last (1978b)
and Figure 2 from Hunter (1981) illustrate these points. Hunter (1981) summarizes
by stating that marine larvae select foods of increasingly larger size as they
grow, but that the average and range of sizes selected differ greatly among
species and may be diagnostic of specific ecological roles.

Prey concentration or abundance has been directly correlated with larval
growth (Laurence, 1974; Houde, 1975). Many larval fish researchers feel that
the contagious distribution of larvae and their prey in patches and the chance
meeting of these patches is a prime determinent of larval feeding success (Jones,
1973; Lasker, 1975; Laurence, 1977). This has been demonstrated experimentally
in the laboratory by Houde and Schekter (1978) who showed that larval sea bream
subjected ‘to simulated patches of copepods for short periods of time could equal
results from constant exposure to similar concentrations. Summary Tables 2 and 3
from Theilacker and Dorsey (1980) and Table 4 from Houde (19780 present relevant
aspects of prey concentration.

Behavioral relationships between larvae and prey determine the effectiveness
of prey capture. Larval behavior usually consists of perception, recognition
and directed, definite responses to a food organism. Hunter (1972, 1977, 1981)
has discussed and described the ethological basis of these activities in detail.
Most larvae are daylight feeders and perceptive distances generally increase


vii

Aspects of Food Limitation of Larvae and Predation
Pressure by Larvae on Their Food Resource .......+... see ceneeeees 91

Literature Cited ........... see neeeeee ede eeeeneeeneeeeee a eeeees 93


FREQUENCY

24

16

12

120

COD - 752ug

PREFERRED PREY=21.6

3 a 8 2 B 8
PREY WEIGHT (ug)

78
8a

Figure 14. Frequency histogram of the distribution-of prey size about
the preferred prey size for a 750 ug cod larva.

198


17.5

150

200

250

300

350

400

450

500

600

700

800

900
1000
1100
1200
1300
1400
1500
1600
1700
1800
1900
2000
2100
2200
2300
2400
2500
2600
2700
2800
2900
3000
3100
3200
3300
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
4600
4700
4800
4900
$000
5100
$200
$300
$400
5500
5600
$700
5800
5900
6000
6100
6200
6300
6400
6500
6600
6700
6800
6900
7000
7100
7200
7300
7400
7500

437.5

587.5

937.5

13(
13
133.59
135.11
136.63
138.15
139.66
141.16
142.66

1.7
14.6
17.3

22.5
24.9

151.4

219.0

23.4
21.2
19.7
18.5
17.6
16.9
16.3
15.8
15.1
14.6
14.2
13.9
13.8
13.6
13.6
13.5
13.5
13.5
13.5
13.5
13.5
13.6
13.6
13.7
13.7
13.8
13.8
13.9
14.0
14.0
4.1
14.1
14.2
14,3
14.3
14.4
14.4
14.5
14.6

14.7

15.3

15.5

15.7
15.7

15.9
15.9

16.2

16.3
16.3


57

Larval condition and growth indices

Special collections of larvae, preserved throughout the
cruise, are analyzed in the laboratory for biochemical con-
tent, histological and morphological assessment, and otolith
increment deposition. Laboratory studies by Buckley (1979,
1981) have demonstrated relations between food availability
and larval RNA/DNA ratios and growth. rate. _A regression
model has been developed recently (Buckley, 1982) between
temperature, RNA-DNA ratio, and mean daily protein growth
vate which accounts for short-term growth over the previous
2-4 days. This sensitive technique is now being used to
study the relations between environmental conditions. and
larval growth and survival in the field. From the same
samples larvae are being analyzed histologically (O'Connell,
1976) and. morphometrically (Theilacker, 1981) to evaluate
their condition and develop criteria for detecting starved
and weakened larvae. Population mean age and long-term
average growth of larvae can be estimated by relating otolith
growth increments. to larval size (Bolz and Lough, 1983). An
individual larva's past environmental growth history also may
be revealed with proper laboratory verification of their
otoliths (Radtke, 1984).

Prey selection

Larvae from selected MOCNESS hauls are processed for gut
contents by the methods described in Cohen and Lough (1983)
and Kane (in press).

Field Operational Plan

A concentration of larvae (or eggs) on Georges Bank is
located from a previous MARMAP broad-scale survey, or at
the time of the cruise by exploratory transects using
standard bongo-net gear in likely areas. Then a grid of


12

LITERATURE CITED

Ahistrom, £. H. 1943. Studies on the Pacific pilchard or sardine (Sardinops
caerulea). Influence of temperature on the rate of development of pilchard
eggs in nature. U. S. Fish Wildl. Serv., Spec. Sci. Rep. 23:1-2.

1966. Distribution and abundance of sardine and anchovy larvae in
the California Current region off California and Baja California, 1951-1964:
a summary. U. S. Fish Wildl. Serv., Spec. Sci. Rep. Fish. No. 534, 71 p.

Ahlstrom, E. H., and 0. P. Ball. 1954. Description of eggs and larvae of jack
mackerel (Trachurus symmetricus) and distribution and abundance of larvae
in 1950 and 1951. Fish. Bull. U. S. 56:209-245.

Arthur, D. K. 1977. Distribution, size and abundance of microcopepods in the
California Current system and their possible influence on survival of marine
teleost larvae. Fish Bull., U. S. 75:601-611.

Beers, J. R., and G. L. Stewart. 1967. Micro-zooplankton in the euphotic zone
at five locations across the California Current. J. Fish. Res. Board Can.
24:2053-2068.

. 1970. Numerical abundance and estimated biomass of micro-zooplankton.
Tn The ecology of the plankton off La Jolla, California, in the period
April through September, 1967 (Part VI), Ed. by J. D. H. Strickland. Bull.
Scripps Instn. Oceanog. 17:67-87.

1971. Micro-zooplankters in the plankton communities of the upper
waters of the eastern tropical Pacific. Deep Sea Res. 18:861-883.

Beyer, J. E. 1980. Feeding success of clupeoid fish larvae and stochastic
thinking. Dana, 1:65-91.

Beyer, J. E., and G. C. Laurence. 1980. A stochastic model of larval growth.
Ecol. Modelling 8:109-132.

1981. Aspects of stochasticity in modelling growth and survival of
Clupeoid fish larvae. Rapp. P.-v. Reun. Cons. int. Explor. Mer, 178:17-23.

Blaxter, J. H. S. 1962. Herring rearing. IV. Rearing beyond the yolk-sac
stage. Mar. Res. Scotland, 1:1-18.

. 1966. The effect of light intensity on the feeding ecology of herring.
Symp. Brit. Ecol. Soc. 6:393-409.

1969. Development: eggs and larvae. In Fish physiology (Vol. 3),
Ed. by W. S. Hoar and D. J. Randall. Academic Press, New York. pp. 177-252.


FREQUENCY

1280
95
92
85
82
75

aBRRSRSESRABSR!S

18

131

cop

r DAY 21

32% SURVIVAL
6 PREY/LITER

r R162. 52109. 5

TOA Le, ; Le
g

8 8 8 € F 8

LARVAL WEIGHT (ug)

Figure 25. Frequency histogram of the weight distribution from a3.
stochastic element model run at a prey density of 6 liter”
for cod larvae at 21 days after hatching.

1



Figure

Figure

Figure

Figure
Figure
Figure
Figure
Figure
Figure

Figure.

Figure -

Figure

Figure

Figure

16.-
1.
2. ez thes preferred. prey. size for-a 750 ug haddock: Varva.
18.
19.
-» Jarva).initial; hatching wel ghts» “based on: empirical laboratory

6
al.
22.
23.
24.
25.

-»Stochastic element model run at a prey density: of 6 liter-!

26
* ~ stochastic element model run at a prey density of 6 liter")

27.
: for cod larvae: at’ 35 days after hatching.

28. |

OL AiterTM

« Titer?

xiv

Frequency histogram of: the distribution of. prey. size about.
the preferred: prey size-for: a 250.ug haddock larva.

Frequency: histogram. of. the distribution of. prey size about

Frequency histogram of the ‘distribution of “Jarval weights of

“suryivors at 42 -days-after-hatching. Cod model 2 at 10-prey

Frequency histogram of a generated normal. di stribution of

Frequency--histogram of a seneatctn normal ‘distribution of

Jarval initial hatching weights based on empirical laboratory
measurements for haddock.

- Simulated population survival at different constant prey

densities for larval cod and haddock. Based on the 3
stochastic element model (version 3).

Frequency. histogram of an initial weight distribution from a
3 seoctastis element model run at a prey density of 6
for cod larvae.

Frequency histogram of the weight distribution from a 3
stochastic element model run.at-a prey density of 6 Viter-1
for cod larvae at 7 days after hatching.

-Frequency histogram of the weight distribution from a3 1
pStochastic- element model run at a prey density of 6 liter”

for cod larvae at 14 days after hatching.
Frequency histogram -of the weight distribution: from a 3
for ‘cod larvae at 21 days after hatching.
Frequency histogram of the weight distribution. from a 3
for cod larvae at 28 days after hatching.

Frequency histogram of the weight distribution from a 3
stochastic element model run at a prey densi ty of 6 Viter"!

Frequency histogram of the weight distribution from a 3 1
stochastic element model run at a prey density of 6 liter”

» for. cod larvae: at. 42° days -after hatching.
29.

Frequency histogram of an initial weight distribution from a
3 Stochastic element: model run at-a prey density of 30
for haddock “larvae.


FREQUENCY

108

82

76

12

129

LARVAL WEIGHT (ug?

Figure 23. Frequency histogram of the weight distribution from a 3
stochastic element model run at a prey density of 6 liter
for cod larvae at 7 days after hatching.

cop
L DAY 7
65% SURVIVAL
6 PREY/LITER
' Xe57, 7413.8
r
4 . re 4 4 a. 4 i _ = 1.
« 8 8 8 8 8&8 8 & 8 8

-1



7

Newell, G. E. and R. C. Newell. 1963. Marine plankton. Hutchinson Educational
Ltd., 243 p.

O'Connell, C. P. and L. P. Raymond. 1970. The effect of food density on
survival and growth of early post yolk-sac larvae of the northern anchovy
(Engraulis mordax Girard) in the laboratory. J. Exp. Mar. Biol. Ecol.,
5:187-197.

Ogilvie, H. S. 1938. The food of post-larval haddock with reference to
the annual fluctuations in haddock broods. ICES, Rpt. 107:57-66.

Reeve, M. and E. Cosper. 1973. The plankton and other seston in Card Sound,
south Florida, in 1971. Univ. Miami, RSMAS Tech. Rept. 24 pp.

Riley, J. D. 1974. The distribution and mortality of sole eggs (Solea solea L.)
in inshore areas. In The Early Life History of Fish. Ed. by J. H. S.

Blaxter. Springer-Verlag, Berlin, p. 39-52.

Rojas de Mendiola, B. 1980. Summary of studies about food and feeding habits
of the anchovy (Engraulis ringens). Intergov. Ocean Comm. Workshop Rept.
No. 28, 221-231.

Rosenthal, H. and G. Hempel. 1968. Experimental Studies in Feeding and Food
Requirements of Herring Larvae. Symposium on Food Chains. Univ. of
Aarhus, Denmark.

Ryland, J. S. 1963. The swimming speeds of plaice larvae. J. Exp. Biol.
40 :285-299.

Schumann, G. 0. 1965. Some aspects of behavior in clupeid larvae.
Calif. Coop. Oceanic Fish. Invest. Vol. X:71-78.

Sherman, K., R. Maurer, R. Byron, and J. Green. 1981. Relationship between
larval fish communities and zooplankton prey species in an offshore
spawning ground. Rapp. P.-v. Reun. Cons. int. Explor. Mer, 178:289-296.

Smith, S. 1947. Studies on the development of the rainbow trout (Salmo
irideus). II. The heat production and nitrogenous excretion. J.
Exp. Biol. 23:357-373.

Stepien, W. P., Jr. 1976. Feeding of laboratory-reared larvae of the sea
bream Archosargus rhomboidalis (sparidae). Mar. Biol., 38:1-16.

Tilseth, S. and B. Ellertsen. 1981. The detection of larval fish food
particles by an in situparticle counter, and monitoring of the particle
density and distribution in first feeding areas. ICES C.M. 1981/L:15. 17 p.

Theilacker, G. H. 1981. Effect of feeding history and egg size on the
morphology of jack mackerel, Trachurus symmetricus, larvae. Rapp. P.-v.

Reun. Cons. int. Explor. Mer, 178:430-440.


86

Tables 1 and 2 present examples of the deterministic. parameters and
output variables at.a constant growth rate for both species.

STOCHASTIC EXTENSION

Two major steps were taken in stochastizing the basic deterministic
model. These. were adding additional model variables based on empirical
data and generating probability distributions about a number of these
variables to form stochastic elements.

One of the additional variables is larval searching capacity.
Searching capacity equals the swimming speed multiplied by the cross-
sectional area of the perception field (Blaxter and Staines, 1971).
Swimming speed and perceptive field defined in terms of larval body
length are converted to terms of larval dry weight by the weight length
equations yielding searching capacity as a function of weight (Fig. 4)
as:

S$ = 0.737 wo-741 (9) for cod
and
S = 0.846 wo-666 (9a) for haddock

where S:= searching capacity in liters day~! and W = dry weight in ug.

The probability of a larva capturing and swallowing an encountered
and perceived prey organism was determined from unpublished. behavioral
observation at the Narragansett Laboratory for haddock and from
observations by Ellertsen et al. (1980) for cod. _ The probability
increased asymptotically with larval size (Fig. 5) and is described by
the following empirical equations:

$1 = 0.9 (1 - 0.667 279-004 (W- Mnind) (10) for cod
and
S1 = 0.9 (1 - 0.778 e-9-0045 (W - Wmind) (10a) for haddock

where :Sl = swallowing probability, W = larval dry weight in ug and
Wain = Minimum larval dry weight in ug. :

Ata given prey density, D, in number of organisms liter-!, the
mean daily ration for a larva would be:

R=S*SleDeLl qi)
where R = mean daily ration in number of organisms, S, Sl, and D are

defined as immediately above and Ll is the percentage of daylight hours
in 24h. , :


FREQUENCY

180

78

12

128

iL

cop

DAY 1

192% SURVIVAL
6 PREY/LITER
Youd. 845, 3

125
225 -

Figure 22. Frequency histogram of an initial weight distribution from a

“3 stoc!
ViterTM

cha

1

8

3054

8

8

LARVAL WEIGHT (ug)

Stic element model run at a prey: density of 6°

for” cod” larvae.

925 -



79

Buckley, L.J., 1979. Relationships between RNA-DNA ratio,
prey density and growth rate in Atlantic cod (Gadus morhua)
larvae. J. Fish. Res. Board Can. 36: 1497-1502.

Buckley, L.J., 1981. Biochemical changes during onetogenesis
of cod (Gadus morhua L.) and winter flounder (Pseudo-
Pleuronectes americanus). larvae. Rapp. P.-v. Réun. Cons.
int. Explor. Mer, 178: 547-552.

Buckley, L.J., 1982. Effects of temperature on growth and
biochemical composition of larval winter flounder (Pseudo-
pleuronectes americanus). Mar. Ecol. Prog. Ser., 8: 181-
186.

Bumpus, D.F., 1976. A review of the physical oceanography of
Georges Bank. ICNAF Res. Bull., 12: 109-134.

Bumpus, D.-F. and Lauzier, L.M., 1965. Surface circulation on
the Continental Shelf of eastern North America between
Newfoundland and Florida. Am. Geograph. Soc., Serial Atlas
of the Marine Environment. Folio 7: 1-4, 8 pl., Appendix.

Busch, D.A. and Mountain, D., 1982. Phytoplankton biomass
and physical conditions on Georges. Bank in an area of lar-
val cod and haddock concentrations. EOS, 63: 95.

Butman, B., Beardsley, R.C., Magnell, B., Frye, D., Vermersch,
J.A., Schlitz, R., Limeburner, R., Wright, W.R. and Noble,
M.A., 1982. Recent observations of the mean circulation on
Georges Bank. J. Phys. Oceanogr., 12: 569-591.

Cassie, R.M., 1963. Microdistribution of plankton. In: H.
Barnes (Editor), Oceanogr. Mar. Biol. Ann. Rev. George
Allen and Univin Ltd., London, 1: 223-252.

Chamberlin, J.L., 1982. Application of satellite infrared
data to analysis of ocean frontal movements and water mass
interactions of Northeastern United States. NAFO Sci.
Counc. Studies, 4: 21-30.

Cohen, R.E. and Lough, R.G., 1983. Prey field of larval
herring Clupea harengus on a continental shelf spawning
area. Mar. Ecol. Prog. Ser., 10: 211-222.

Colton, J.B., Jr., 1965. The distribution and behavior of
pelagic and early demersal stages of haddock in relation
to sampling techniques. ICNAF Spec. Publ., 6: 318-333.

Colton, J.B., Jr., 1972. Short-term variation in estimates
ef chlorophyll abundance. ICNAF Res. Bull., 9: 81-94.

Colton, J.B., Jr. and Marak, R.R., 1962. Use of the Hardy
plankton recorder in fishery research programme. Bull.
Mar. Ecol., 5: 231-246.

Colton, J.B., Jr. and Marak, R.R., 1969. Guide for identi-
fying the common planktonic fish eggs and larvae of con-
tinental shelf waters from Cape Sable to Block Island.
Bur. Comm. Fish. Biol. Lab. Woods Hole Lab. Ref. No. 69:
1-43.

Colton, J.B., Jr., Smith, W.G., Kendall, A.W., Jxr., Berrien,
P.L. and Fahay, M.P.,1979. Principal spawning areas and
times of marine fishes, Cape Sable to Cape Hatteras. Fish.
Bull., U.S., 76: 911-915.


Figure

Figure

Figure

Figure

Figure

Figure

Figure

Figure

Figure

Figure

Figure

Figure

Figure

Figure

30.

31.

32.

33.

34.

35.

36.

37.

38.

39.

40.

41.

42.

43.

xv

Frequency histogram of the weight distribution from a 3
stochastic element model run at a prey density of 30 liter-}
for haddock larvae at 7 days after hatching.

Frequency histogram of the weight distribution from a 3 1
stochastic element model run at a prey density of 30 liter”
for haddock larvae at 14 days after hatching.

Frequency histogram of the weight distribution from a 3
stochastic element model run at a prey density of 30 liter-1
for haddock larvae at 21 days after hatching.

Frequency histogram of the weight distribution from a 3 1
stochastic element model run at a prey density of 30 liter”
for haddock larvae at 28 days after hatching.

Frequency histogram of the weight distribution from a 3 1
stochastic element model run at a prey density of 30 liter”
for haddock larvae at 35 days after hatching.

Frequency histogram of the weight distribution from a 3 1
stochastic element model run at a prey density of 30 liter”
for haddock larvae at 42 days after hatching.

Frequency histogram of the distribution of weights of larval
cod survivors on day 42 from a large population run (10,000
initially) with the,3 stochastic element model at a prey
density of 5 liter~}

Frequency histogram of the distribution of weights or larval
haddock survivors on day 42 from a large population run
(10,000 initially) with tye 3 stochastic element model at a
prey density of 15 liter”

Frequency histogram of the distribution of initial weights of
the surviving cod larvae from Figure 36.

Frequency histogram of the distribution of initial weights of
the surviving haddock larvae from Figure 37.

Frequency histogram of the distribution of weights of
surviving cod larvae on day 42 from the 4 stochastic element
model with a daily varying prey density.

Frequency histogram of the distribution of weights of
surviving haddock larvae on day 42 from the 4 stochastic

element model with a daily varying prey density.

Frequency histogram of the distribution of initial weights of
the. survivors from Figure 41.

Frequency histogram of the distribution of initial weights of
the entire population for the runs depicted in Figures 41 and


85

Preferred prey size for given size larvae was calculated from the
data and relationships reported by Kane (1984). Regressions (Fig. 2)
are:

P = -0.073 + 0.043 L (3) for cod
and
P = -0.046 + 0.032 L (3a) for haddock

where P = prey width in mm and L = larval standard length in mm.

Conversions of prey width to prey wet weight were done according to
the generalized equation from Pearre (1980):

PL = 1000 (1.557 p2-878) (4):
where Pl = prey wet weight in ug and P = prey width in mm.

Conversion of prey wet weight to prey dry weight is:

P2 = 0.277 Pl (5)
where P2 = prey dry weight in ug.

The fraction of food ingested that is actually digested by larvae
has been measured in nitrogen budget studies by Buckley and Dillmann
(1982). Beyer and Laurence (1981) reworked these data (Fig. 3) as:

B = 0.8 (1-0.625 e-0-002(W - Win) (6)

where 8 = fraction of ingested food digested, W = larval dry weight
in ug and W,j, = minimum larval dry weight in yg.

The cost of processing and utilization of the digested food is put
to a = 0.4 (Andersen and Ursin, 1977).

Daily growth increment is expressed as:
Gl=G-W (7)

where Gl = daily growth increment in ug, G = % growth -day~+ and W larval -
dry weight in ug.

Daily ration is calculated from:

Gl +M
R1 = ————_________ 8
(1 - a) +B + P2 (8)

where Rl = daily ration as # prey, and Gl, M, a, 6 and P2 are as
previously defined.


90

This model version also proved useful in simulating a variety of
different situations. Population growth and survival can be
simultaneously followed for any time frame at a given prey density.
Growth (distribution of sizes at time) and survival percentages for
populations of cod and haddock larvae at constant prey densities of 6
and 30 literTM*, respectively, every 7 days after hatching until day 42
are presented in Figures 22 to 35. One can follow the population
progress up the weight axis and down the survival axis noting the
intermittent mean size and distribution about this mean. These figures
graphically show that most of the mortality takes place in the first 2-3
weeks after hatching.

Another type ‘exercise is to make runs of relatively large
populations of individuals (= 10,000) at the lower prey densities
supporting population survival (as indicated in Figure 21) to try and
simulate and elucidate conditions approaching the empirically observed
low survival measurements from field survey estimation. Figures 36 and
37, respectively, depict the sizes of the 0.37% cod and 0.61% ngadock
that survived at the marginal densities of 3 and 15 prey liter The
initial size distribution of these very same surviving larvae are given
in Figures 38 and 39.

The fourth and final stochastic element added to derive model
version 4 was varying the prey density encountered on a daily basis.
This tends to create a somewhat patchy food environment in terms of time
and may not be far from the real situation. The day can be considered a
discrete feeding state for larvae which can change from state to
state. Larvae are known to be visual feeders that cease feeding and
become passive in darkness. During the dark, non-feeding time the
larvae could be transported by physical factors to a new and different
feeding regime where the density of prey is different. The likelihood
of this seems quite high at the small spatial scales in which larvae
interact with their physical and biological environment.

Empirical data on small scale spatial variability and absolute
densities of prey are available from process-oriented cruises on Georges
Bank (Laurence et al., 1984; Lough, 1984). These data give mean-
variance’ parameters with which to generate probability distributions for
daily varying prey density. They showed that prey were distributed ina
uniform manner and likely to be in a range of 1 to 50 prey literTM* on a
small scale (30 liters or less) relative to larvae. A uniform
distribution for daily varying prey density was used as the stochastic
element; that is, larvae would have an equal probability of encountering
any ‘one of the prey densities within the range. .

Frequency histograms of survivors at 42 days show the differences
between cod and haddock in this #4 stochastic element simulation with
fa of He cod surviving (Fig. 40) and 15% of the haddock surviving
Fig. 41

A further look. at the surviving haddock revealed some insight as to
why they might have survived. The initial weight frequency distribution
of the actual individual survivors at time 0 is shown in Figure 42. If
this is matched up with the initial weight distribution of the whole


106

Table 4. Summary of bottle samples (all1 sampler sizes, depths,.
stations) -- EVRIKA-80-02 relevant larval cod and haddock prey

organisms.

No. Per Liter

Prey Category Mean” Range %
Lamellibranch Larvae 1.21 0.30 - 3.34 8.8
Copepod Eggs

(0.1 - 0.2 mm diam) 2.14 0.23 - 5.29 15.6
Copepod Nauplii 7.55 4.10 - 14.28 55.0
Older Stage Copepods 2.82 1.08 - 8.66 20.6

X for all sampler sizes,
Range 8.63 - 24.17.

depths and stations =

13.72 + 4.04.


53

same larvae-prey population. Thus, by reducing horizontal
variability, aliasing of observations. vertically would be
reduced in order to conduct time-series observations over
a minimum of two tidal cycles. The limitations of time-
series analyses in marine ecosystems are discussed by
Denman and Platt (1978)...

The deployment of moored current meter arrays can pro-
vide a truly synoptic three-dimensional picture:of the
horizontal current field within the study area. Coarse
to meso-scale MARMAP plankton-hydrography surveys con-
ducted on Georges Bank and contiguous waters during the
same time provide a broader background in which to com-
pare our more intensive fine-scale studies. Remote sen-
sing offers the potential of regional synopticity for a
number of near-surface parameters such as ocean tempera-
ture and color (Chamberlin, 1982; Gower, 1982).

METHODS
Gear, Instrumentation, and Special Techniques
Bongo-net sampler

Standard MARMAP bongo-type samplers are used to make inte-
grated water-column hauls from 5 m above the bottom to the sur-
face to collect zooplankton (Posgay and Marak, 1980). A
6l-cm bongo sampler (505 and 333 um mesh nets) and 20 cm
bongo sampler (253 and 165 wm nets) array are towed obli-
quely at 1 1/2 knots (78 cm/s) and lowered at a wire speed
of 50 m/min and retrieved at 20 m/min. Water filtered
through each net is measured by a flowmeter and the tow
depth profile is measured with a time-depth recorder.


59

CTD-fluorometer cast

The objective of this operation. is to obtain a vertical
profile (and variability) of temperature, salinity, and
chlorophyll a fluorescence on a micro-scale level. Casts
may be repeated for short-term variability. Niskin water
bottle samples are collected at selected depths for cali-
bration purposes and particle size analysis using the HIAC
PC320 system. Ancillary observations include a light-meter
cast to define the light extinction curve, and a bottom-trip
Niskin bottle cast to collect a phytoplankton sample within
ameter of bottom.

MOCNESS lm haul

The objective of this haul is to determine the vertical
distribution and abundance of fish larvae and larger zoo-
plankton from near bottom (<5 m) to surface with 10 or 5 m
resolution. An adequate sample of larvae (30-100 individuals)
is usually obtained by filtering 250 m3 of water which takes
about 5 min for each net. During this 5 min the net travels
a horizontal distance of c. 235 m..

Plankton pump cast

Micro-zooplankton samples are collected at 4-6 discrete
depth levels based upon the vertical distribution of the fish
larvae and environmental conditions. At each depth level,

1 m3 of water is pumped on deck and filtered through 20 and
53 um mesh nets. Sampling resolution is 1-2 m vertically
and 10's of meters horizontally, depending on the rate of
pumping and ship's drift.


10 required amino acids. Lipid requirements for fishes are not adequately
described (NRC, 1981). Polyunsaturated lipids are.found in.the natural diets

of fishes including essential fatty acids. These are used for energy, for
cellular structure, and for maintenance of the integrity of biomembranes.

Little carbohydrate is found in the natural diet or body of fishes, and they

can grow on diets devoid of carbohydrates. However, hexoses are of natural
nutritional significance to fishes, and all fishes studied have the ability

to utilize carbohydrate as an energy source (NRC, 1981). Nutritional constituent
composition of- larval fish food organisms is virtually unknown, although gross
energetic equivalents have been measured for some crustacean prey.(Table 8).

ITI CONCEPTS, STRATEGIES AND RECOMMENDATIONS

‘It is clear from the review that we have a great deal of specific knowledge
regarding component parts of larval feeding relationships and associated processes.
Nevertheless, we have thus far been unable to relate this knowledge to conditions
in the sea that pinpoint functional causal mechanisms controlling survival in
a reliable, quantitative way for predictive management purposes. The following
discussion presents a conceptualization of larval trophodynamics as well as
recommendations for sampling schemes and rationale, integration into appropriate
Management ‘systems, and some personal opinions about persistent problems.

A Concept

My conception of larval trophodynamics and related survival is that

it is most likely a probabilistic process. Given the fact that fish have evolved
over millions of years to respond reproductively (spawn) to environmental cues,
primarily temperature and photoperiod, within a certain finite range (temperatures
usually have a range of 1-3°C), they are not likely to be affected by productivity
(primary-secondary) disynchrony for the entire spawning period. Match-mismatch

is not apt to occur on a large scale. More plausible is the situation where
larval survival.-is controlled stochastically within a range of population levels
affected by. chance ‘encounter with "patchy" food and fine tuned by predation.
Catastrophic events such as major meteorological occurrences, advective currents,
anoxias, or man's fishing could also cause fortuitous major negative impact.

The basic functional aspect of this in terms of trophic encounter-interactions
can be explained within the framework of Hutchinson's (1961) "paradox of the
Plankton."- Plankton systems support a diversity of organisms in similar niches
unlike most systems where competitive exclusion sets up. Physical mixing in the
planktonic environment prevents dominance and contagion caused by gradations
of:this mixing causes. a probabilistic environment. Chance trophic’ encounter
resulting in success or failure could easily happen in this type system.

Progressing from the more general picture of Hutchinson's "paradox" to the
specifics of predator-prey interactions, it can be argued that it doesn't. really
matter if. you're a proponent of the so-called Cushing (predation) or Jones
(starvation) hypotheses regarding larval survival: because they are both the same
thing. They can be expressed together in a triotrophic relationship (Laurence,


FREQUENCY

148

HADDOCK
INITIAL WEIGHT-SURVIVORS
Ke76. 027.9 ae

DAILY VARYING- PREY

40

Figure:



87

Larval growth can then be defined as:
G= (1-a)+B+Re P2-M (12)
where G = larval daily growth increment in ug dry weight
and a, 8 (Equation 6), R (Equation 11), P2 (Equation 5), and M (Equation
2) are previously defined.

Maximum and minimum, rations which produce growth rates of +15% and
-10% of body weight day~* respectively are calculated as:

R2 (415%) = te N*M (13)
~(l-a) + B+ P2
and
RO (-10%) = N= OW (4)

(1 - a) +B + P2

where R2 and RO are the rations in ug dry weight and all other
parameters are previously defined. The maximum and minimum figures are
based on empirical results of field estimated growth rates from daily
growth increments of otoliths (Bolz and Lough, 1983) and results of
laboratory starvation studies (Beyer and Laurence, 1980).

A “minimum barrier" or death size has been calculated for both
species. This barrier corresponds to the smallest sizes of live larvae
of known age ever recorded in all the various laboratory studies
conducted at Narragansett over the years. The rationale is that any
fish smaller than these were dead and thus, the minimum live size.

Regression relationships describing the barriers for each species
(Fig. 6) are:

My = Minin 20 -0282T (15) for cod
and
Wp = Min €0°02267 (16) for haddock

where Wy = larval barrier dry weight in ug, Wmin = larval initial,
minimal hatching weight in ug, and T = age in days. During model runs,
larvae of given size and age are compared with the minimum barrier at
each time step (day) and judged to be alive and growing or dead and
eliminated from the simulation. Examples of this process are depicted
in Figure 7 which shows the weight trajectory (size) on a daily basis
for 3 haddock larvae feeding on variable daily rations. Larva #1 did
not grow well and reached the minimum barrier and died on day 12.
Larvae #2 barely maintained its weight for the first 4 1/2 weeks at
which time it increased its growth rate. Larvae #3 is an example of a
fast growing individual.


The swimming speed transformed to cm sec"! is for a comparison to current
velocities. Most larvae would be actively transported by prevailing tidal or
other currents.

The volumes of water searched day~! are relatively small because of the
short perception distances. However, they can be over long vertical or horizontal
distances (hundreds of meters).

The number of required prey captures per linear swimming distance shows
that larvae need to be successful in the order of meters to tens of meters.

The required number of prey liter-] for larval feeding at a 10% capture rate
is in the order of 1000-100,000 m-3 which has often been observed in zooplankton
surveys.

Sampling Strategy

If we relate the above calculations to a potential sampling strategy for
process-oriented field cruises we can assess feasibility, compatibility and
appropriateness. The core of the sampling scheme is to conduct on station
vertical profiling of T, S, chlorophyl], and zooplankton organisms with plankton
pumps and electronic sensors (CTD, fluorometer and HIAC particle counter) at
selected stations within a mesoscale survey (25 km2 grid) of larval distribution
and abundance (Appendix II). This will provide the capability of continuous,
instantaneous (real time) measurements in the vertical. Since we know that even
the smallest fish larva is capable of swimming up and down the vertical extent
of the water column in the Georges Bank study area (40-100 m), the instrument
Measurement capabilities are more than adequate in this dimension.

The horizontal mensuration aspects present some problems. Unlike the
vertical (bounded by the water surface and the bottom), the horizontal boundaries
of critical factors may far exceed the larva's ability to encounter them. A
larva can swim hundreds of meters day-! in the horizontal plane, while prey
encounter related to patch or inter-patch distance could conceivably be on the
order of kilometers. Also, larvae and their food are transported by horizontal
currents, thus compounding the picture. From a sampling strategy, the horizontal
current speed and the vertical sheer can be measured with profiling current
meters strung at depths, or a cyclosonde. This gives transport. Temperature
and salinity changes most likely will not differ significantly enough in the
horizontal to affect larvae and/or their food except, perhaps, in frontal zones.
Discrete measurements to the hundreds of meters in the horizontal can be made
for T, S, chlorophyl1 and zooplanktors with instruments such as U.0.R., other
fluorometers and particle counters. This does not approach the ability to make
these measurements in meters as in the vertical; but, nevertheless, it approaches
the scale (hundreds of meters) that fish larvae are able to travel and encounter
prey in a day's time.

The above estimates of feeding parameters are apt to be conservative, and
haddock larvae are likely to have powers of locomotion and/or transport and
encounter rates of prey greater than discussed. Three factors contribute to
this: 1) Delayed feeding ("point of no return") or the ability to withstand


38

TRIOTROPHIC RELATIONSHIP AFFECTING LARVAL FISHES

ADULT STOCK
PREDATOR : — PREY

CINDIVIDUAL ) a LARVAE ( POPULATIONS )

NUMERICAL DENSITY DEPENDANT DENSITY INDEPENDANT FINE- SCALE
ABUNDANCE & TROPHODYNAMICS GROWTH TROPHODYNAMICS DENSITY &

& er
BIOENERGETIC —==> SURVIVAL STRUCTURAL

DEMANDS CORRELATIVE PROBABILISTIC DISTRIBUTION

r

MEDIATED BY PHYSICAL (ABIOTIC) PROCESSES

Figure 3. Triotrophic relationship affecting larval fishes.


A REPORT ON THE DEVELOPMENT OF STOCHASTIC MODELS
OF FOOD LIMITED GROWTH AND SURVIVAL OF
COD AND HADDOCK LARVAE ON GEORGES BANK

Geoffrey C. Laurence

National Marine Fisheries Service
Northeast Fisheries Center
Narragansett Laboratory

Narragansett, RI 02882

MARMAP Contribution MED/NEFC 83-34


Iv.

21
Enercetics
A. Gross Metabolic Requirements
1. Techniques for Measurement
2. Reconciliation of Standard, Routine and Active Metabolic Levels
and Activity
B. Digestion Rate
1. Techniques
2. Mathematical Formulations
3. Digestion vs. Feeding activity, Prey Level, Prey Type
C. Assimilation
1. Definitions
2. Measurements and Techniques
D. Consumption Estimates
1. Direct and Indirect Determinations
E. Budgets
1. Theory
2. Types (Caloric, Nitrogen, Carbon)
3. Current Models
Biochemistry
A. Condition Indices (organo-cpds, nucleic)
1. Comparisons with Morphological and Histological Indices
2. Relation to Feeding Level and Diet
B. Digestive Enzyme Kinetics
1. Identification, Inervation and Sequence
2. Relations to Food Type and/or Level

3. Temperature Kinetics


FREQUENCY

Nn

18

121

PREFERRED PREY*@, 9Sug
b HADDOCK-68, 1 ug
L
L Y
Ss Nu ~ o ao s N 7 L-) L--)
a . ° ° ° a “a - = -

PREY WEIGHT (ug)

Figure 15. Frequency histogram of the distribution of prey size about
the preferred prey size for a 68.1 ug haddock larva.


1981; Figure 3). A key point in this triotrophus is a redefinition of or

clarified interpretation of density independence/dependence. If larvae function

as predators, they are essentially density independent of each other because

the order of magnitude of their own spatial density distribution in nature is |
so much greater than that of the density of the food they feed and grow on that

they are unlikely to directly compete with each other but are more affected by

the density of their food as it affects starvation. Conversely, if a larva

functions as a prey organism, its mortality is most likely density dependent

because its spatial distribution is much denser than its predators and the

More larvae there are, the more chances for predation mortality.

The overall interpretation of this is that at normal adult stock and larval
population levels, larval survival and growth is mainly density independent and
controlled by the varying encounter with patchy prey. This is a probabilistic
process and results in varying recruitment. At extremely abundant levels of
larvae, density dependent predation on larvae may operate to prevent abnormally
large populations in most instances or to reduce levels produced from large
adult stock size. This is mainly a correlative process associated with abundances.
At very low adult stock levels, egg production and subsequent larval survival may
be inherently so low as not to produce any recruitment. All this is affected
by adult stock size and physical oceanographic process. The physical processes
have, in general, a random influence and the adult stock level has a more direct
or abundance-cause and effect at low population levels and can be influenced
greatly by fishing effort.

Strategy Relating Larval Trophodynamics
to Applied Fishery Management

As previously stated, the ability to understand larval fish trophodynamics
and resultant survival and relate this to fishery production would be a major
advancement in resource management capabilities. Three main components are
needed: 1) abundance estimates or indices of egg and larval stages, 2) quantita-
tive estimates of larval growth and feeding parameters, and 3) predictive models.
Two of these three requirements are currently available as well as portions of
the third. Ichthyoplankton surveys conducted routinely as in the MARMAP mode,
for example, provide abundance estimates. A variety of larval fish growth and
survival models exist (Laurence, 1977; Beyer and Laurence, 1980, 1981; Beyer,
1980). some of which have population predictive capabilities. Larval tropho-
dynamics, physiology and behavior have been studied extensively in the laboratory
and field, as indicated in the review portion of this paper. The only area of
incomplete knowledge is in the physical-mathematical description of the spatial-
temporal bounds of larval predator-prey organisms from the natural environment
and associated production factors. Several laboratories have or are attempting
multidiscipline process-oriented field programs to study these problems
(Lasker, 1975, 1981; Tilseth and Ellertsen, 1981; Lough and Laurence, 1981).
Once these are known, prey encounter rate functions in the existing models can
be used to predict larval individual and population growth and survival based on‘
the abundance estimates of the eggs or early larvae from ichthyoplankton surveys
as an initial starting point. Predicted estimates of larval survival can then


49

near surface flow is generally driven by the winds; the mean
transport is offshore. Recent studies summarized by Butman
et al. (1982) concluded that the observed mean flow at 10 m
has a permanent. clockwise circulation around Georges Bank
with @ mean circuit time of c. 2 momths for a parcel moving
along the 60 m isobath. Despite the considerable variability
that could occur in the trajectory of such a parcel, they
inferred that the clockwise circulation around the crest of
the bank may provide a mechanism for partial retention of
plankton.

The water on Georges Bank shoaler than 60 m is vertically
well-mixed throughout the year by the semi-diurnal, rotary
tidal currents that have speeds up to >2 knots (103 cm/s)
(Bumpus, 1976). Progressive vector diagrams of the tidal
elipses are oriented NW-SE on the crest with their long
axes ranging 4-8 miles (7-15 km) in length. Summing the
hourly speeds over a 12 h period, an approximiation of the
distance travelled by @ parcel of water ranged 10-20 miles
(19-37 km) over the shoals and 5-6 miles (9-11 km) over the
deeper parts.

Besides the dominant tidal energy on the shelf, storms at
4-5 d intervals have an important role in shelf water dynam-
ics (Beardsley et al., 1976).

In winter the well-mixed water is separated from adjacent
water Masses by two fronts. On the southern flank, the shelf/
slope-water front intersects the bottom at about 80 m and
separates the cooler, fresher shelf water from the warmer,
more saline slope water. On the northern side, a subsurface
front separates the Georges Bank water from the Gulf of Maine
water. In late spring-summer a seasonal thermocline (20-30 m)
develops in waters greater than 60 m. A subsurface band of
cool winter water is found along the southern flank between
the 60 and 100 m isobaths.


FREQUENCY

118

15
COD = 44ug

127

“PREFERRED PREY =. 1.6

PREY WEIGHT (UG)

Figure 12. Frequency histogram of the distribution of prey size about
the preferred prey size for a 44 ug cod larva.


14.0

144

14.5

14.7

15.3
15.3
15.3,

3000
3100
3200
3300
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
4600
4700
4800
4900
5000
5100
5200
5300
5400
5500
5600
5700
5800
5900
6000
6100
6200
6300
6400
6500
6600
6700.
6800.
6900
7000
7100
7200
7300
7400
7500
7600
7700
7800
7900
8000
8100
8200
8300
8400
8500
8600
8700
8800
8900
9000
9100
9200
9300
9400
3500
9600
9700
9800
9900
10000

50
100

120.0
124.0
123.0
132.0
136.0
140.0
144.0
148.0
152.0
156.0
160.0
164.0
168.0
172.0
176.0
180.0

188.0

384.0

102

18.92 217.9 80 34.8
19.38 222.9 80 34.9
19.83 227.8 80 34.9
20.28 232.6 80 35.0
20.72 237.4 80 35.1
21.16 242.2 80 35.1
21.59 246.9 +80 35.2
22.02 251.6 +80 35.3
22.45 256.2 80 35.3
22.88 260.8 80 35.4
23.30 265.3 80 35.5
23.71 269.9 80 35.5
24.13 274.3 80 35.6
24,54 278.8 80 35.7
24.95 283.2 «80 35.7
25.35 287.6 ~80 35.8
25.76 292.0 80 35.9
26.16 296.3 80 35.9
26.55 300.6 80 36.0
26.95 304.9 80 36.1
27.34 309.2 ~80 36.1
27.73 313.3 80 36.2
28.12 317.5 80 36.3
28.51 321.7 80 36.3
28.89 325.8 -80 36.4
29.27 329.9 80 36.4
29.65 334.0 +80 36.5
30.03 338.1 80 36.6
30.40 342.1 «80 36.6
30.77 346.1 80 36.7
31.14 350.1 80 36.7
31.51 354.1 80 36.8
31.88 358.1 +80 36.8
32.24 362.0 80 36.9
32.61 366.0 80 37.0
32.97 369.9 80 37.0
33.33 373.7 80 37.1
33.69 377.6 80 37.1
34.04 381.4 80 37.2
34.40 385.3 80 37.2
34.75 389.1 80 37.35
35.10 392.9 80 37.3
35.45 396.7 80 37.4
35.80 400.4 80 37.4
36.15 404.2 80 37.5
36.49 407.9 80 37.5
36.83 411.6 80 37.6
37.18 415.3 80 37.6
37.52 419.0 80 37.7
37.86 422.6 80 37.7
38.20 426.3 80 37.8
38.53 429.9 80 37.8
38.87 433.6 80 37.9
39.20 437.2 80 37.9
39.54 440.8 80 38.0
39.87 444.3 80 38.0
40.20 447.9 80 38.1
40.53 451.5 +80 38.1
40.86 455.0 80 38.2
41.18 458.5 +80 38.2
41.51 462.1 80 38.3
41.83 465.6 80 38.3
42.16 469.1 80 38.4
42.48 472.5 80 38.4
42.80 476.0 80 38.5
43.12 479.5, 80 38.5
43.44 482.9 80 38.6
43.76 486.3 80 38.6
44.08 489.8 +80 38.7
44.39 493.2 80 38.7
44.71 496.6 80 38.7
8% Growth

72 13.2 30 125.1
1.04 17.5 +32 109.5
1.33 21.3 35 99.1


14.7
14.8
14.8
14.9
14.9
14.9
15:0
15.0
16.1
15,1
15.1
15.2
15.2
15,3
16.3
15.3
18.4
15.4
15.4
15.5
15.5
15.5
15.6

15.7

7600
7700
7800
7900
8000
8100
8200
8300
8400
8500
8600
8700
8800
8900
9000
9100
9200
9300
9400
9500
9600
9700
9800
9900
10000

608.0

632.9
640.0

736.0

800.0

104

451.5
458.5

465.6
469.1
472.5
476.0
479.5
482.9
486.3
489.8
493.2
496.6

52.8

83.1

53.4

54.5

54.9

55.2





81

Laurence, G.C., 1983. A report on the development of sto-
chastic models of food limited growth and survival of cod
and haddock larvae on Georges Bank. NOAA, NMFS, NEFC,
Narragansett Lab. Unpubl. MS, 68 pp-

Laurence, G.C. and Rogers, C.A., 1976. Effects of temperature
and salinity on comparative embrya development and mor-
tality of Atlantic cod (Gadus morhua L.) and haddock
(Melanogrammus aeglefinus L-). J. Cons. int. Explor. Mer,
36: 220-228.

Lough, R.G., 1979. Larval herring patch study. ICNAF Res.
Doc. 79/VI/116: 1-4.

Lough, R.G., 1982. Observations on the impingement of warm
core eddy 81-C on Georges Bank. EOS, 63: 59.

Lough, R.G., Bolz, G.R-, Pennington, M.R. and Grosslein, M.0D.,
1980. Abundance and mortality estimates for sea herring
(Clupea harengus L.) larvae spawned in the Georges Bank-
Nantucket Shoals area, 1971-1978 seasons, in relation to
spawning stock and recruitment. NAFO SCR Doc. 80/IX/129
(Revised): 1-59.

Lough, R.G. and Potter, D.C., 1983. Rapid shipboard identi-
fication and enumeration of zooplankton samples. J. Plank-
ton Res., 5: 775~-782.

Marak, R.R. and Colton, J.B., Jr., 1961. Distribution of fish
eggs and larvae, temperature and salinity in the Georges
Bank~-Gulf of Maine area, 1953. U.S. Fish and Wildl. Serv.,
Spec. Sci. Rept.-Fisheries, No. 398: 1-61.

Marak, R.R. and Livingstone, R., Jr., 1970. Spawning dates
of Georges Bank haddock. ICNAF Res. Bull., 7: 56-58.

Miller, D., Colton, J.B., Jr. and Marak, R.R., 1963. A study
of the vertical distribution of larval haddock. J. Cons.
int. Explor. Mer, 28: 37-49.

O'Connell, C.P., 1976. Histalogical criteria for diagnosing
the starving condition in early post yolk sac larvae of
the northern anchovy, fngraulis mordax Girard. J. exp.
mar. Biol. Ecol., 25: 285-312.

Posgay, J.A. and Marak, R-R., 1980. The MARMAP bongo zoo-
plankton samplers. J. Northw. Atl. Fish. Sci., 1: 91-99.

Pugh, P.R.-, 1978. The application of particle counting to
an understanding of the small-scale distribution af plank-
ton. In: J.H. Steele (Editor), Spatial Pattern in Plank-~
ton Communities. Plenum Press, NY, pp. 111-129.

Radtke, R.L., 1984. Cod fish otoliths: information storage
structures. In: E. Dahl, D.S. Danielssen, E. Moksness
and P. Solemdal (Editors), The Propagation of Cod Gadus
morhua L., Fligdevigen rapportser., 1, 1984:

Report of the Working Group on Larval Fish Ecology, 1982.
Lowestoft, England, 3-6 July 1981. Coun. Meet. int.

Coun. Explor. Sea, 1982 (L:3): 1-141 (Mimeo-)-~

Sameoto, D.D., 1975. Tidal and diurnal effects on zooplankton
sample variability in a nearshore marine environment. J.
Fish. Res. Board Can., 32: 347-366.

Sameoto, D.D., 1978. Zooplankton sample variation on the
Scotian Shelf. J. Fish. Res. Board Can., 35: 1207-1222.


26

Table 2. Critical prey densities for fish larvae. (Table 4 from Theflacker and Morsey, 1980),

“Survival at various

Container Stock food densities
volume Duration density
Species and Nensity Percent
common name (liters) (days) Food type No. /L No. /t survival Reference
PLAICE
Pleuronectes platessa 5 1a Artemia 50 1,000 7) wyatt 1972
nauplii (larvae) uu 7?
5 20n 54
1no 32
NORTHERN. ANCHOVY :
Engraulis mordax 10.8 12 Wild zoo- ou) 4,0n0 51 O'Connell #& Raymond
plankton {eqgs) 900 - 12 1970,
5 (naup? is) an a5
9 i)
BAY ANCHOVY
Anchoa mitchilli 76 16 Wild zo0- 0,5-2 5,000 64 Houde 1978
plankton (eggs) 1,900 48
5 (naupt it~ no 5
copepodites}3 50 0-12
SER AREAM
Archosaurqus rhomboidalis 76 16 " 05-2 500 72 " "
(eggs) 100 37
§ 50 13
2 7
1 4
LINED soLe
Achirus lineatus RB 16 7 05-2 1,000 54 " .
(eggs) 100 13
5 50 1
wennincx,
Melanogrammus aeglefinus aA 42 Wild z00- a 3,00 39 Laurence 1974
plankton (larvae) 1,009 22
5 (nauplii) san a
100 a
10 oO
HERRING
Clupea harengus 20 21-63 Artemia & 3,000 4-8 Werner & Blaxter
5R-84 1,000 3-12 1980
300 o-8
100 0-12
30 0-1
WINTER FLOUNDER
Pseudopleurontectes americanus 64 49 Wild zoo- 3 3,000 4 Laurence 1977
plankton (larvae) 1,000 4
(naup1ii) son 3
100 1
10 0

Survival was 100% at SO/L for first 7 days without a decrement in length; see also Riley (1966).
Estimated food density for indicated survival levels.

Aprankton blooms of Chlorella sp. and Anacystis sp. maintained in rearing tanks.

4Estimated by adjusting for hatching success.

Swunter, in press.


FREQUENCY |

146

20 : i
; cop
- DAY 42 j
a @6% SURVIVAL es
ee X= 1688. 841097. 1 :
1s + 1. DAILY VARYING PREY DENSITY
. UNIFORM DISTRIBUTION: 1 TO SO/1 -) =
to}
sft _
rt
o

2 ¢  §

LARVAL WEIGHT (ug)

Figure 40. Frequency histogram of the distribution of ‘weights of
surviving cod larvae’on day 42 from the 4 stochastic element
model with a daily varying prey density.


DRY WEIGHT (ug) |

1258
1008
958
988
852
Baa
758
728
652
6a
552
58a
45a
4B
358
328
258
28a
158
18a

11

3

HADDOCK

| ~——MINIMUM WEIGHT BARRIER

Figure 7,

AGE (DAYS POST-HATCH)

Daily weight gain or lo
variable daily rations.

ss of 3 haddock larvae feeding on



88

METHOD FOR TRANSFERRING A NORMAL PROBABILITY DISTRIBUTION
TO A DISTRIBUTION WITH KNOWN MEAN AND VARIANCE

A number of variables in this model development were transformed
into stochastic elements from empirically derived laboratory and field
data. Basically, the process was to use the known.mean and variance or
the relationship of mean and variance of the empirical data and transfer
these to.a known, normalized probability distribution from statistical
tables.

The steps in the method are:
1. Generate 21 random numbers between 0 and 20.

2. Calculate the mean (=10) and variance of the random number
sample or assign the variance of the required distribution (i.e. poisson
where mean = variance).

3. Normalize the random number distribution to a distribution with
mean = 0 and variance = 1 and with known probability distribution by

catculating the Z-statistic as Z = x - 10/s (Steele and Torrie, 1960).

4. Multiply calculated Z-statistic by the known standard deviation
of the empirical population and add or subtract (depending on sign of Z-
statistic) to known mean from empirical population to get a normalized
stochastic parameter.

STOCHASTIC MODEL EVOLUTION

‘Figure 8 is an abbreviated flow chart of the stochastic model that
illustrates basic routines, stochastic elements, chronology of operation
and flow. The model was developed by adding one stochastic element at a
time and noting parameter responses. The first stochastic element
incorporated was prey encounter which was a random process. At this
point the model was essentially like the one of Beyer and Laurence
(1980). In this version (#1) all larvae started out the same initial
size, the prey density was constant, and the prey size was the preferred
size according to equations (3) and (3a). Random prey encounter was
chosen because analyses of rélevant prey organisms from field studies
(Laurence et als, 1984) showed the prey to be randomly distributed at
smal} ‘scales “on Georges Bank. This was approximated by estimating a
poisson distribution about the mean daily ration R from equation (11)
and ‘transferring it to a normalized probability distribution. with. +2
standard errors. Examples of two of these derived distributions about
the mean number of prey. consumed day~* for. newly hatched cod and haddock
are shown in Figures 9 and 10. Results from this version (#1). of the
model proved to be somewhat deterministic with the larvae either all
living or dying ina narrow’ range of prey densities (45 to 50 prey
liter"! for haddock and 5 to 10 for cod). A population of cod that
survived 100% until day 42 after hatching and attained large body
weights is shown in the frequency histogram of larval weight in


Table 5. Swimming performance of larval fishes.

29

(Table 2 from Theilacker and Norsey, 1980).

1

Age Cruisin
Toy Taye Ts

Duration of burst

Species et om7s BL/s traveled per burst Reference
Sardine 15-18 yolk: 3-5 mm Rlaxter & Staines
Sardina pilchardus . 3 wks. 1971
Herring yolk; 6-1] mm Rlaxter % Staines
Clupea harengus B wks. 1971
Rlaxter 1969
Northern anchovy is) 3m Hunter 1972
Engraulis mardax 19 3m Hunter (in press)
n Som
19 5m -
v 15 mm
. . 7 35 mm?
Vv 80 mm Theilacker (unpubl.)
vv 150 gm
v 8 ome Hunter 1972
v 13 m3 “
. " v 3m 2a Webb & Carolla (MS)
7 & em cI
7 13m acd
whiterish® 7-15 15 nm 1S Hoagman 1974
Coregonus clupeaformis
Jack mackerel) 16 6,0-6.5 mm 4-6 Devonatd (pers.comm.)
Trachurus symmetricus
Paciffe mackerel 19 3.6 m Hunter & Kimbrell
Scomber japonicus . 15.0 m2 1980
Large mouth bass 19 2-7 d; 6-7 om 3.48 Laurence 1971
Micropterus salmoides
Platce? 10-12 yolk; 5-7 om 0.2 Blaxter & Staines
Pleuronectes platessa . 9-10 om 1.0, 1971
— " 5-7 om 1.5% ~10 Ryland 1963
" 9-10 mm = 2.78 13
" 25 mm 6.58
Sole” 10-12 yolk; 3-5 mm OL Blaxter & Staines
Solea solea 9-10 mm 07 1971
Walleye perch? 13 7.5 mm OS Houde 1969
Stizostedion vitreum vitreum 13 11.0 om 35
Yellow perch? 3 7.5 9m 15 Houde 1969
Perca flavescens * 11.0 mm 35

Votuntary swimming,
metamorphosis.

3attacking prey.
4,

Imean burst speed

Sno effect of temp. or age.

Storced swimming: speed sustained for 30 m,
790% decrease in activity at metamorphosis.
Storced swimming; speed sustained 4-20 s.

Storced swimming; speed sustained for 1h.

B.1R L + 4,89; maximum distance traveled = 3.79 + 0.08,