SPATIAL AND TEMPORAL VARIABILITY IN EARLY GROWTH RATES OF THE

ANTARCTIC SILVERFISH, PL£URAGRAMMA ANTARCT/CUM, AROUND

THE ANTARCTIC CONTINENT

A Thesis Presented to the Faculty of Moss Landing Marine Laboratories California State University, Stanislaus

In Partial Fulfillment of the Requirements for the Degree of Master of Marine Science

By Dawn Outram May2000 TABLE OF CONTENTS

PAGE

Acknowledgements...... V

List of Tables...... VII

List of Figures...... VIII

List of Appendices...... X

Abstract...... XI

Introduction ......

Methodology...... 9

Results

Data Base...... 15

Shrinkage...... 15

Developmental Stages...... 16

Growth Relationships ...... 16

Back-Calculation and Hatch Size ...... 17

Hatch Seasonality...... 21

Growth Seasonality...... 21

Discussion

Data Base...... 23

Staging and Shrinkage...... 23

Growth Relationships...... 24

Increment and Growth Rate Analysis...... 25 iii PAGE

Literature Cited ...... ,... ,,...... 37

Tables ...... ,, , , , , , , , , , , , , , , , , , , ...... 48

Figures...... 61

Appendices ...... 91

IV ACKNOWLEDGEMENTS

The work presented here was made possible with the help of many people, and it is with the utmost appreciation that I would like to thank them. First I would like I o thank my parents for knowing just when a little push was needed, and being there when things seemed to go a little slower than desired. Salina Ciandro, Barbie Byrd, Julie Neer and Kim Puglise for all their words of wisdom and for helping me become a well rounded individual in the scientific world. Jane Schuytema for drawing the map template used throughout this project. Thanks to Mary Yoklavich and Martin White for being there from the beginning and providing me with the background necessary to get this project off the ground. John Heine, Dan Backus, Richard Williams, Bruce Robison, and the entire

AMLR Program for all their assistance in collecting the specimens used here. John Krupp and Giacamo Bernardi of University of California Santa Cruz and Sarah Tanner of Moss

Landing Marine Laboratories for their technical assistance with the scanning electron microscope. Gail Johnston and Sandy Yarbrough for making sure everything was taken care of in the front office, and to Joan Parker and Eleanor Uhlinger of University of Rhode

Island for finding and precurring any obscure refernces I may have needed. Tony Amos,

Chuck Rowe and Andi Wickham-Rowe of University of Texas and Roger Hewitt of the

AMLR Program for providing the necessary facts about what is happening in the Elephant

Island area. Thanks to those back-east, Karen Wishner, Celia Gellman, Bob Sand, and

Kevin Golde for providing me with the necessary equipment, time and support to get things done when I moved back home. A very special thanks to Mary Rapien for getting

v me focused when I started to stray. Thanks to the National Science Foundation (RACER

Program) for providing me with the funding needed to do this project. Finally, I owe a great deal of thanks to my committee for all the time they spent on this project.

Thanks to Pam Roe for making it easier to finish a thesis from a distance. To Valerie

Loeb for being a mentor and a friend. I sure will miss those trips down South. And finally to Gregor Cailliet tor all the support you have given me and for helping show I can do it If I put my mind to it.

vi LIST OF TABLES

TABLE PAGE

1. Summary of specimens collected per sampling location, date, and

technique used...... 49

2. Summary results of at-test to determine a diHerence in diameter

between left and right sagittal otoliths of P/euragramma

antarcticum ...... 52

3. Summary calculations of intra-reader precision of age estimates...... 53

4. Summary of the statistics used in determining between-year and

between-region differences in size and age of Pleuragramma

antarcticum during ring formation ...... 54

5. Summary of environmental parameters within each region of Antarctica

used in this study...... 56

6. Standard length and age during P/euragramma antarcticum's early

development for each sampling time available ...... 58

7. Instantaneous growth rates during early development as well as total

instantaneous and absolute growth rates of P/euragramma

antarcticum for each sampled region ...... 59

B. Variability in date of hatch of P/euragramma antarcticum

between-years and between-regions...... 60

Vll LIST OF RGURES

RGURE PAGE

1. Map of study area with pertinent currents...... 62

2. Examples of pertinent otolith microstructure of P/euragramma

antarcticum ...... 63

3. Plot comparing otolith diameter to standard length, total length and

weight of P/euragramma antarctcium ...... 64

4. Plot indicating sample utilization...... 67

5. Annual sea ice for Elephant Island...... 68

6. Size frequency histogram of P/euragramma antarcticum standard

length and otolith diameter for each sampling period...... 69

7. Plot comparing pre-preservation standard length to post-preservation

standard length of P/euragramma antarcticum...... 70

8. Plot showing the progression of notochord and plate development of

P/euragramma antarcticum based on Moser (1996)...... 71

9. Plot showing the progression of flexion in Pleuragramma antarcticum

based on Moser (1996)...... 73

10. Plot comparing weight to standard length in P/euragramma

an tarcticu m...... 76

11. Comparison of otolith diameter and standard length in P/euragramma

an ta rcticum...... 77

V!ll RGURE PAGE

12. Between-year comparisons of Pleuragramma antarctic urn growth using

logistic function...... 78

13. Between-region comparisons of Pleuragramma antarcticum growth using

logistic function...... 81

14. Between-year comparisons of P/euragramma antarcticum growth using

von Bertalanffy growth function...... 82

1 5. Between-region comparisons of P/euragramma antarcticum growth using

von Bertalanffy growth curve...... 85

16. Von Bertalanffy growth curve for P/euragramma antarcticum...... 86

1 7. Growth seasonality during P/euragramma antarcticum's first year of

development...... 87

ix LIST OF APPENDICES

APPENDIX PAGE

A. Modified Julian Day calendar applied to fish whose hatching event

started on September 1 of one year to August 31 of the following

year...... 92

B. Modified Julian Day calendar applied to fish whose hatching event

started on May 1 of one year to April 31 of the following year...... 93

C. Summary of growth curves for P/euragramma antarcticum and their

subsequent parameters ...... 94

D. Reported environmental values for all Antarctic regions considered in

this study...... 96

X ABSTRACT

Pleuragramma antarcticum is an essential part of the high Antarctic ecosystem, yet little is known about its early stages and their physiological responses to variations in environmental conditions. It has been speculated that fish in some regions may show different growth or developmental rates; therefore this study was designed to: a) determine patterns in otolith microstructure; b) enumerate daily increments for age analysis; c) determine the birthdate and size at hatch of P. antarcticum within five different regions; d) determine if significant between-year or regional differences exist for birthdate and/or size at hatch; e) determine the cause of certain microstructure patterns; and f) determine the existence of between-year or regional differences in early growth rates. Fish were measured and otoliths removed. Enumeration of daily rings was possible using scanning electron microscopy. P. antarcticum reaches an asymptotic length of ca. 217 mm SL (standard length) and a maximum age of 52 years. P. antarcticum predominantly hatched between October-January; however between-year and regional differences are apparent. Within the Elephant Island region, low ice years enable P. antarcticum to have an extended hatch season. This is in contrast to

McMurdo Sound in which fish hatched during March-April, possibly due to delayed spawning or prolonged incubation times resulting from cold temperatures and/or low prey availability. Fish within McMurdo Sound were also larger at hatch, absorbed their yolk-sac earlier, and were the only specimens to show a drastic decline in growth rate during the onset of winter. Therefore, while fish at all other regions had similar growth rates, growth in fish at McMurdo Sound was significantly different. xi INTRODUCTION

Antarctic waters are inhabited by endemic species adapted to withstand harsh temperatures and varying degrees of glaciation and productivity. The blood of fishes in temperate and tropical waters freezes at -o.9'C, but many Antarctic species (e. g.

Champsocephalus gunnari; Channichthyidae) have evolved different peptides and glycopeptides that act as antifreezes (DeVries, 1 982; Bargelloni and Lecointre, 1998;

Cheng, 1998; Giardina, et al., 1 998; Wehrmann, 1998).

The family Nototheniidae contains approximately 50 species, most of which lack swimbladders and are demersal. However, a few species, including the Antarctic silverfish, Pleuragramma antarcticum (Nototheniidae), have lipid sacs (75% triacylglycerols) that increase buoyancy and allow them to reside in the water column and feed upon pelagic resources (Dewitt and Hopkins, 1977; DeVries and Eastman,

1978; Daniels, 1982; Kellermann and Kock, 1 984; Hubold, 1 985b; Hubold and Tome,

1989). Buoyancy of this species is further enhanced by weight reduction (e. g. unconstricted vertebrae, reduced vertebral processes, and poorly mineralized scales) and the persistence of a notochord composed of vacuoles containing glycosaminoglycan

(density=1 .03 g/cm'; Eastman, 1 993). P/euragramma antarcticum has 5-10% red

muscle fibers and therefore is considered "active" relative to other nototheniids (e.g.

adult Notothenia neglecta (3%)), but it is sluggish compared to most temperate teleosts,

which have 26% red muscle fibers (Eastman, 1993; Greer-Walker and Pull, 1 975).

P!euragramma antarcticum numerically dominates the fish assemblages of the

circum-Antarctic convergence and pack ice zones (Figure 1) of the Davis Sea, Weddell

Sea, Ross Sea, and Prydz Bay. Individuals occur from 0-900 m in both open water and 2 under ice (Hubold, 1984; Takahashi and Takahashi, 1984; Hubold, 1985a;

Gerasimchuk, 1986; Gon and Hemmstra, 1990; White and Piatkowski, 1993). Hubold

(1985a) reported adult P. antarcticum concentrations of 1 ton/km2 in the Weddell Sea; lower densities were reported for the seasonal sea ice zones of Gerlache Strait and

Antarctic Peninsula (Kellermann, 1986). This species alone comprised 90-97% of total pelagic fish biomass in the Ross and Weddell Seas (Hubold, 1985a; Dewitt, 1970).

White and Piatkowski (1993) encountered larval concentrations (predominantly age 0) of up to 350/1000m3 within the Weddell Sea from 0-700 m. Although these larvae occurred throughout the water column, greatest abundance typically was within the upper 70 m. For 0-age fish, mean standard length (15.3-18.2 mm SL) increased with depth (White and Piatkowsi, 1993).

P/euragramma antarcticum has a relatively complex life history that includes ontogenic migration (Hubold, 1985a). The eggs (1.8-2.0 mm diameter) are spawned in inshore areas along the permanent pack ice (Hubold, 1984; Eastman, 1985;

Kellermann, 1986; Kock and Kellermann, 1991 ). Although the eggs were once presumed to be buoyant, recent research near Vestkapp in the Weddell Sea casts doubt on the hypothesis of pelagic egg development (Hubold pers. comm.). While Hubold collected thousands of early yolk sac larvae, not a single egg was found within the entire water column before or during the hatching event. Larvae hatch in cold (~ -1.4°C) nearshore shelf areas, and after an unknown period of time, the juveniles migrate offshore to the warmer (,; -0.5°C) ice free waters of the East Wind Drift (Figure 1; Hubold, 1985a;

Radkte, et al., 1993). Based on Sr/Ca ratios measured within the otoliths, Radkte, et al.

(1993) hypothesized that this migration occurs at the age of 2-4 years. At 3 approximately 8-10 years old, the adults become benthopelagic and migrate back to colder shelf areas adjacent to the permanent pack ice to spawn (Hubold, 1985a;

Kellermann, 1986 ; Hubold and Tome, 1989; Radkte, et al., 1993).

P/euragramma antarcticum reaches sexual maturity by age 6, but first spawning generally occurs in the seventh year when individuals are 180-190 mm SL (Keel< and

Kellermann, 1991 ). At this time, they are at least 65% maximum length and have a

Gonosomatic Index ((gonadal weight/weight of fish) x1 00) of 13-46% (Kock and

Kellermann, 1991 ). Potential fecundity (# eggs/ female in one year) is positively correlated with female size and ranges from 4,315-17,774 eggs (Kock and Kellermann,

1991). Estimated relative fecundity (# eggs/weight or length of the female) is 67.7-

156.8 eggs. The potential fecundity is high relative to other Antarctic fish species associated with the permanent pack ice zone (e. g., Trematomus bernacchii and

Pagothenia borchgrevinki have only 1000 eggs; Gerasimchuk, 1988; Kock and

Kellermann, 1991 ). Pleuragramma antarcticum is the only high Antarctic fish species with a relative fecundity >50 eggs (Kock and Kellermann, 1991 ). The high fecundity and peak spawning time (2-4 weeks in early austral spring (i.e., August-September) characterize P. antarcticum as an altrical spawner (Andriashev, 1965; Kellermann,

1989; Loeb, 1991; Kock and Kellermann, 1991; Kellermann and Schadwinkel,

1991 ).). The eggs develop for 60-75 days and young larvae occur from October to

December (Andriashev, 1965; Kellermann, 1989; Kock and Kellermann, 1991 ).

Larval size at hatch is reported to be 6-9 mm SL (Regan, 1916; Hubold, 1989; Kock and Kellermann, 1991 ). 4

Larvae and juveniles of P/euragramma antarcticum are long and slender with a patch of chromatophores at the caudal fin base and two parallel dorsal rows of melanophores extending from the gut to caudal fin. Pigments are also present along the ventral surface (Yefremenko, 1979; Keller, 1983). Notochord flexion begins at ca.

17.8 mm standard length (SL) and continues to ca. 24.6 mm SL when fin ray formation occurs; metamorphosis to juvenile stage is apparently complete by 36.8 mm SL (Keller,

1983). Keller (1983) plotted body depth vs. standard length, and the regression line shows an inflection point between 20-30 mm SL. This inflection point was also observed when caudal peduncle depth was plotted against standard length. Keller (1983) attributed this point to the onset of metamorphosis and offshore migration.

Larval, juvenile and adult stages of P. antarcticum exhibit resource partitioning (Hubold and Ekau, 1987). In the Weddell Sea, larvae feed on abundant pteropods (e. g. Limacina spp.; Hubold, 1985a, Hubold, 1985b) and cyclopoid copepods

(Oncaea sp. and Oithona sp.; Hubold and Hagen, 1997). The juveniles in offshore waters feed on small krill (Euphausia superba), polychaetes, chaetognaths, and copepods

(primarily Galan us propinquus in winter and Calanoides acutus and Metridia gerlachei in the summer; Hubold, 1985b; Williams, 1985b; Hubold and Hagen, 1997).

Throughout the spring and summer the adults feed principally on adult krill, copepods, and amphipods (e. g., Themisto gaudichaudil); occasionally they also feed on larval krill, pteropods, and Euphausia crystallorophias (Hubold, 1985b; Williams, 1985b). During the winter, the adults may feed primarily on cyclopoid and calanoid copepods

(Kellermann and Schadwinkel, 1991 ). Visual acuity allows the adults to implement a

"sit and wait" predation strategy (Eastman, 1988; Eastman, 1993). 5

P/euragramma antarcticum appears to avoid direct competition for shared food

resources with another high Antarctic nototheniid, Aethotaxis mitopteryx, through

spatial separation. In Halley Bay (Weddell Sea) P. antarcticum was captured primarily

between the 700 and 2000 m isobaths, while A. mitopteryx occurred mostly inshore of the 650 m isobath (White and Piatowski, 1993).

The diet of adult P. antarcticum demonstates large regional variation in

dominant prey (Dewitt and Hopkins, 1 977; Daniels, 1982; Kellermann and Kock,

1 984; Takahashi and Takahashi, 1984; Hubold, 1 985b; Williams, 1985b). In contrast to the Weddell Sea, the diet of P. antarcticum within McMurdo Sound (Ross Sea) is

comprised of 22% fish, 13% due to cannibalism. The harsh environment here forces the adults to feed on all available resources including their young (Eastman, 1985).

In the permanent pack ice zone and seasonal sea ice zone, characterized by

fluctuating krill abundance, P. antarcticum fills an intermediate level in the food chain.

In the Ross Sea, P. antarcticum dominates the diet of other fishes, and channichthyids

here are dependent upon this prey species (Eastman, 1 985). The dominant

channichthyid in the Weddell Sea, Chinodraco myersi, feeds almost solely on P.

antarcticum (frequency of occurrence 95.5%; Takahasi and Takahasi, 1 984; White and

Piatkowski, 1993). Following krill, P. antarcticum may be the most important prey

item for top predators such as whales (e.g., Orcinus orca), penguins (Pygoscelis papua,

P. adeliae and Aptenodytes forsten), South Polar sku as ( Catharacta maccormickt),

Antarctic petrels (Thalassoica antarctica), seals (e. g., Leptonychotes wedde/lt),

icefish (channichthyids), and Antarctic cod (Dissostichus mawsont) (Eastman and 6

DeVries, 1981; Keller, 1983; Takahashi and Takahasi, 1984; Hubold, 1985b;

Eastman. 1 985).

P/euragramma antarcticum is an essential part of the high Antarctic ecosystem, yet little is known about the early life stages and its physiological responses to regional variations of environmental conditions around the Antarctic Continent. There are; however, some regions where factors such as growth and developmental rates may vary.

For example, based on otolith morphological characteristics, Radkte et al. (1993) suggested that P. antarcticum may have different growth rates in the Weddell and Ross

Seas. To investigate links between environmental conditions and differential growth rates within the high Antarctic, one must consider age structure and growth rate between different ecosystems.

Previous studies of Antarctic fish growth rates have predominately utilized size frequency analysis (Keller, 1983; Hubold, 1985a; North, 1990; Loeb, 1991 ). Based on sequential sampling in the Weddell Sea, Keller (1983) calculated a growth rate of

0.24 mm/day for larval P. antarcticum. Hubold (1985a) reported larval growth rates of 0.20 mm/day over a 50 day period in January-February 1980 and 0.24 mm/day over a 38 day period in January-February 1981. While these growth rate estimates are similar, the accuracy of predicting age from size frequency alone is questionable (Lough, et al., 1982) and otolith ring formation has been established as a more reliable aging method (Pannella, 1971; Brothers, et al., 1976).

Pannella (1971) determined that daily increments were laid down in the otoliths of some temperate and tropical fish species. Daily increments have also been found in the otoliths of Antarctic fishes such as P. antarcticum, Nototheniops nudifrons, and 7

Trematomus newnesi (Radkte, et al., 1989; Radkte and Hourigan, 1990; Radkte, et al.,

1993}. During periods of favorable environmental conditions and fast growth (e.g. daylight or summer), protein-dense rings (O-zone) are deposited in the otoliths. In contrast, a calcium carbonate rich ring (L-zone) is laid down during periods of suboptimal conditions and slow growth (e.g. night time or winter). Together the two rings form a daily increment with width reflecting fish growth (Pannella, 1971; Secor, et al., 1992; Secor, et al., 1995).

Antarctic fish have adapted to grow quickly during the short peaks in seasonal productivity (Kellermann, 1989; Loeb, et al., 1993). One would therefore expect faster growth rates and wider daily increments associated with enhanced primary production during the nearly 24 hours of daylight in the austral summer compared to the dark, zero productivity conditions in winter (Hubold, 1985a).

The sagittal otoliths of P. antarcticum are smooth with a rounded but distinguishable rostrum and anti-rostrum. In younger individuals, the sagittae appear to be circular in shape; the rostrum becomes more pronounced as the fish ages (Figure 2

a-d). The core region is a distinct area separated by a well pronounced organic matrix

or O-zone. It forms prior to hatching and therefore represents the primoidal nucleus

and embryonic growth (Radkte, et al., 1993; Figure 2 e).

Using otoliths, Radkte, et al. (1993) calculated a growth rate for P. antarcticum

Which was consistent with that based on size frequency analysis (Hubold, 1985a). Their

results indicated a relatively high early growth rate that decreased as the fish reached

adulthood. Radkte, et al. (1993) and Hubold and Tomo (1989) described P. antarcticum

as a slow growing and long-lived species, which reaches a maximum length of 211 mm 8

SL and 308 mm SL, respectively. The great difference between these maximum size estimates complicates determination of age at maturity, which could be 13-14 years based on Radkte, et al. (1 993) or 7-8 years based on Hubold and Tomo (1 989).

Validation is therefore needed to establish the real age-at-size relationship lor this fish and therefore the true age of maturity. However, validation is complicated by the difficulty in maintaining live specimens from such a harsh environment lor appropriate periods of time.

Because of its importance in Antarctic food webs we must learn more about the biology and ecology of P. antarcticum. Basic information includes estimates of growth and development relative to environmental conditions that vary around the continent. The main objectives of this study were to: (a) determine patterns in otolith microstructure;

(b) enumerate daily increments lor age analysis; (c) determine the birthdate and size at hatch of P. antarcticum within live different regions around the Antarctic continent;

(d) determine if significant regional differences exist lor birthdate and/or size at hatch;

(e) determine the cause of certain microstructure patterns; and (I) determine the existence of temporal or regional differences in early growth rates. 9

METHODOLOGY

Collection Information

Larval, juvenile and adult specimens of P. antarcticum were obtained from five regions around the Antarctic continent: a) Marguerite Bay, West Antarctic Peninsula,

December 31,1991; b) Elephant Island, East Antarctic Peninsula, February-March

1995 and February-March 1996; c) Weddell Sea, Atlantic Ocean Sector, October 1992; d) Prydz Bay, Indian Ocean Sector, January 1987, January 1991, and January 1993; and e) McMurdo Sound, Ross Sea, Australian Sector, November 1992 and December

1993-February 1994 (Figure 1 and Table1 ).

Specimens (9-1 85 mm SL) were collected and processed by a variety of different people using many different techniques (Table 1). In all of these cases except at

Prydz Bay, fish were stored in 100% ethanol until processing at Moss Landing Marine

Laboratories (MLML). Length measurements were made using a stage micrometer.

Standard length (SL; tip of snout to end of notochord or urostyle) and if possible, total length (TL) were recorded to the nearest 0.1 mm. Representative specimens from each region were weighed to the nearest mg using a Perkin-Elmer autobalance AD-22.

Sagittal otoliths were removed from those fish still in ethanol.

Personnel from the Australian Antarctic Division measured and weighed all specimens obtained from Prydz Bay. Lengths {56-185 mm SL) were measured to the

nearest mm using a meter stick and weight measurements were made to the nearest mg

on a digital scale. Sagittal otoliths from these fish were removed and stored dry prior to

analyses at MLML. 1 0

Data Analysis

Growth relationships were calculated using a linear regression or power function. Forty-one specimens (16-59 mm) were measured prior to and after preservation (3 days to 2 months) in 100% ethanol to establish a shrinkage rate, which could then be used to adjust post preservation lengths to fresh lengths. Shrinkage rate was consistent regardless of time between pre- and post-preservation measurements.

Dramatic physiological changes such as flexion and fin formation during early development may affect the early growth rate of marine fishes; therefore, larval developmental stages were determined according to the definition presented by Moser

(1996). These fish were then grouped in 1.0 mm intervals to determine the size at which each stage began.

Sagittal otoliths were removed from 335 of the 461 analyzed fish, representing the entire size and developmental range sampled (Figure 4). Otoliths were then mounted in Cytoseal 60© resin on a glass slide with the concave side facing down (Dawn Outram,

Mary Yoklavich and Martin White, pers. comm.). Otolith diameter (the widest distance across that encompassed the nucleus; Figure 2 a) was measured to the nearest 0.01 mm

using a Bausch and Lomb Image Analysis System (Image 1.37). A paired t-test was

performed to determine if a significant difference existed between the mean diameter of

the left and right sagitta (Table 2). Since no significant difference (p>0.05) was

calculated, the first otolith measured was used, in order to maintain consistency.

Back-calculations (predicting fish size given otolith diameter; Ricker 1992)

were dependent upon a strong relationship between (Ricker, 1992) growth of the otolith

and fish growth. In order to establish the best relationship for back-calculations, 1 1 otolith diameter was plotted against fish standard length, total length and weight (Figure

3 a-c). Because of the narrow range of standard lengths, total lengths and weights from each region, all data were pooled to establish the relationship between fish and otolith growth. The standard length to otolith diameter regression yielded the highest r-squared value; therefore, it was used to calculate growth rates. For comparison with results from Radkte, et al. (1 993), otolith diameter was also regressed against standard length.

Due to economic constraints, otoliths from ca.180 fish of the total collected (ca.

20 fish/sampling period) were prepared for SEM analysis; the selected material represented the available size range from each sampling period (Figure 4). For the

Elephant Island region and the Weddell Sea, the entire collection of fish was used. These otoliths were ground and polished using 320, 600, 800, and 1200 grit paper to accentuate daily rings (Radkte, et al., 1 993). Grinding continued until the core was clearly visible under a compound microscope {40 X). After polishing, the otoliths were etched with 4% ethylenediaminetetraacetic acid (EDTA) for 1-17 min or 1%

Hydrochloric acid (HCL) for 1-90 sec (HCL) to enhance physical discontinuity between the zones. Otoliths were then attached to viewing stubs for scanning electron microscopy at the University of California at Santa Cruz (John Krupp, SEM Specialist). The stub

and a portion of the slide containing the otolith were coated with silver paint to facilitate

the gold coating process (John Krupp, pers. comm.). Three coats of gold were applied

using a Polaron E5100 cool sputter coater@ and argon gas. Each coating process lasted

30 seconds yielding a final thickness of ca. 506 angstroms. A scanning electron

microscope (SEM) was then used to examine surface relief and increments at a

magnification of 12,000 X ± 4,000. The SEM revealed raised areas of CaC03 (L-zones) j 2 and depressed areas representing the organic protein matrix (O-zone) made distinguishable during etching (Secor, et al., 1992 and Secor, et al., 1995). The two zones together were presumed to form a daily increment. If microstructure was apparent, increment counts were performed using the O-zone as a day (Figure 2 g). If microstructure was not yet visible, the gold. was ground off and the otolith was etched for an additional length of time. It was then recoated and scanned.

At least two counts were made per otolith. To assess intra-reader precision,

Average Percent Error (Beamish and Fournier, 1981 ), Coefficient of Variation (Chang,

1982), and Index of Precision (Chang, 1982) were calculated. Precision indices showed an error of 4-32%, but the error was predominantly less than or equal to 10% (Table

3). Within the Weddell Sea, the intra-reader precision was as high as 32%. These were the first otoliths read and the only ones read more than twice. If the first reading

is eliminated, the intra-reader precision is 12%.

Standard length at hatch was back-calculated using otolith core diameter (Figure

2 e) in conjunction with the otolith diameter to standard length regression. Interannual

and regional comparisons between size at hatch were made using parametric ( T-test or

AN OVA) or non parametric (Mann-Whitney) statistics (Zar, 1984). Date of hatch was

back-calculated using average age per animal and time of capture. These dates were then

used to determine a mean hatch date as well as a modal month of hatch. The Julian day

calendars used to account for the initiation of the hatch season are provided in Appendices

A and B.

Three highly etched rings were detected near the core of many otoliths. These

rings are denoted as ring 1 (closest to the core), ring 2 (intermediate) and ring 3 1 3

(largest diameter and latest to form; Figure 2 e-f). The diameter of each ring was measured and used to back-calculate standard length at the time of their formation. Age at the time when each ring was formed was determined. Standard length and age were compared between years or between regions using either parametric (Hest or ANOVA) or nonparametric analysis (Mann-Whitney or ~ruska/1 Wallis; Zar, 1984; Table 4).

Instantaneous growth rates (In SL2-In SL1)/(age,-age1) (Ricker, 1979) were also calculated for the intervals separating each ring. By comparing increment counts with length, total fish instantaneous and absolute (SL,-SL,)/(age2-age,) growth rates were calculated for each sampling time and/or region.

Several growth functions were tested to determine the best fit: von Bertalanffy; oscillating von Bertalanffy (Newberger and Houde, 1995); Logistic; Gompertz; and

Linear. In some instances, back-calculations were necessary to determine growth

during the first year or to supplement missing data (Ricker, 1 992). The best fit of data to growth function was determined using smallest sum of squares. This comparison of

growth curves indicated that the logistic curve fit the data best in most cases with the

only exceptions being McMurdo 1992, McMurdo 1993, and Prydz Bay 1993 (Appendix

C; Moreau, 1987). Therefore, the logistic curve was used for comparisons between

years and regions. The von Bertalanffy curve was also chosen for between year and

regional analysis because of its fit when older individuals were encountered (Moreau,

1987) and to permit comparisons with data from other studies (Hubold and Torno,

1989; Radkte, et al., 1993).

Growth curves for each year/region (e. g., McMurdo 1992 vs. McMurdo 1993)

were compared graphically as well as by sum of squares analysis (Kappenman, 1 980). 1 4

Kappenman (1980) established a criterion whereby one calculates the sum of squares for each combination (n!/(r!(n-r)!) of comparisons to be made, and the lowest result is considered the most preferable. Between-region comparisons were made by the same methods as between years, but they utilized pooled data from each sampling time (i.e. all years). In addition, three growth curves (Gompertz, von Bertalanffy, and Logistic) were applied to the entire data set to determine which one best described the growth of P. antarcticum. The oscillating von Bertalanffy growth function (Newberger and Houde

1995) was used in conjunction with modal month of hatch for each sampling period to determine seasonal fluctuations in growth rates.

Different Antarctic regions have different ecological and environmental characteristics. An attempt was made to acquire as much environmental information as possible to characterize the environment of the five regions studied here. Unfortunately such data are limited or unavailable. However, some information was obtained for all regions. This includes: temperature, salinity, chlorophyll-a (chi-a}, primary production, and zooplankton abundances of primary prey items (Table 5 and Appendix

D). Ice indices were also acquired for the Elephant Island Region (Figure 5; Hewitt pers. comm.). 1 5

RESULTS

Data Base

Length data for a total of 461 specimens ranged from 9 to 185 mm SL; however, the complete range did not exist for all sampling periods. In fact, standard length (F o.o 5

'· '· 340 =299.08; p<0.05) and otolith diameter (F o.o5 340 =294.67; p<0.05) were significantly different between all sampling periods except within McMurdo Sound. A total of169 individuals representing three sampling periods (1 987,1991, and 1 993) from Prydz Bay were in the late juvenile stage with the exception of a few specimens in

1 993 that were adults. Specimens from the Weddell Sea (11 individuals from 33-39 mm SL) and Elephant Island region (26 individuals representing data from 1995 and

1996) were also in the juvenile stage. Two individuals captured near Elephant Island

(1/yr) were postflexion larvae of 14 mm §,L. Thirty-three larval (preflexion and flexion stage) specimens ranging in size from 9-13 mm SL were captured within

Marguerite Bay. Collections from McMurdo Sound (1 992 and 1993) included a total of

103 postflexion larvae (18-25 mm; Table 1 and Figure 6).

Shrinkage

Biological specimens stored in preservatives undergo morphometric changes

(Fowler and Smith, 1983; Glenn and Mathias, 1 987; Hjoerleifsson and Klein-MacPhee,

1992; AI- Hassan, et al., 1993; Johnston and Mathias, 1993). These changes cause

shrinkage in fish. Based on 41 specimens, the mean post-preservation standard length

was significantly smaller than that prior to preservation in 100% ethanol (T=-9.51,

df=40, p<0.01 ). Uncorrected SL measurements were used throughout this study with 1 6 one exception, those lengths used in developmental stage analysis were corrected using

2 the regression T 0 =1.0981 (Tt)+1 .8417 (R =0.966; Figure 7) to permit comparisons with other studies.

Developmental Stages

When developmental stages were determined for 101 specimens ranging from post hatch (10 mm) through flexion and fin formation (21.9 mm), 96% of the 10-

10.9 mm SL specimens and 100% of the 11 .0-1 1.9 mm SL specimens were in the preflexion stage (straight notochord, with or without initial hypural plates). The flexion stage generally began at 12.0-12.9 mm SL and continued to 13-13.9 SL mm, however, a few specimens in these size categories were post flexion (vertical hypural plates). All specimens ::o, 14.0 mm SL were in the postflexion stage. Fin ray formation was observed in one individual at 21.9 mm SL (Figure 8 and 9).

Growth Relationships

Initially, P. antarcticum appeared to expend a greater amount of energy on

linear growth (i.e., length) and later used more energy for secondary growth (i.e.,

weight; Figure 10). The regression is Wt=2E-07(SL)'·"" (R 2=0.935). This curve

indicated at ca. 90 mm, P. antarcticum made a transition from increased length to

increased weight.

Back-calculations to determine size at hatching and early growth used the

2 resulting regression of SL=0.0698 (00)+8.9106 (R =0.970; Figure 1 1a) because the

regression coefficient was high and there was little scatter. When otolith diameter was

used as the independent variable (for comparisons with Radkte et al. 1993). the

equation was 00=1 3.887 (SL) -101.1 1 (R 2=0.970; Figure 1 1 b). 1 7

Back Calculation and Hatch Size

In almost all otolith cores examined, there appeared to be many "false centers"

which were laid down during embryonic development (Figure 2 e). Examination of 53 otoliths yielded a mean core diameter (Figure 2 e) of 7.5 11m (s. e.=0.28). Applying the

regression equation in Figure 11 a to this otolith diameter yielded a mean standard length at hatching of 9.4 mm (s. e.=0.02). Between sampling periods, standard lengths at

hatch ranged from 9.2-9.8 mm. Statistical tests yielded no significant interannual differences in hatch size (p>O.OS). However, an ANOVA applied to pooled data within

each region indicated between region differences in hatch size (F0.05 • 3•49=2.984; p<0.05;

Table 6). Hatch lengths were similar in the Weddell Sea and Prydz Bay regions

Three well defined otolith rings were present in fish collected from 4 of the 5

regions. Specimens collected from Marguerite Bay were too young to have deposited ring

2 or 3. The first ring had a mean diameter of ca. 24.2 11m (s.e.=0.43) in all regions.

This was formed at a mean standard length of 10.6 mm (s.e.=0.03) and an age of 15.2

days (s.e.=0.56). Statistical tests applied to back-calculated standard lengths and age

data yielded no significant between-year differences (p>O.OS). A One-Way ANOVA also

yielded no significant regional differences in standard length (p>O.OS) at the time of

ring formation when between-year data were pooled for each region (Table 6).

However, the age at which this size was reached was significantly different between

regions (F0 .05 , 3 •62 = 7.815; p

Sound (12.2 days) and oldest in Prydz Bay and the Weddell Sea (ca. 18 days).

Ring two had a mean diameter of 68.3 11m (s.e.=0.80); formation of this ring

was associated with a mean standard length of 13.7 mm (s.e.=.06) and an age of 63.7 1 8

days (s.e.=1.96). As with ring one, no significant interannual differences were found in

either larval size or age at formation (p>0.05). When the interannual data were pooled for each region, statistical analyis yielded no significant between region differences for

either standard length or age (p>0.05) at ring two formation (Table 6).

At ca. 117.03 days (s.e.=2.52), ring three was formed. At this time, the fish

were ca. 17.5 mm (s.e.=0.10) with a corresponding otolith diameter of 122.4 1-1m

(s.e.=1.40). As with the other two rings, statistical analysis yielded no between-year

differences in fish size or age during ring three formation (p>0.05). However, a One­

Way ANOVA on pooled standard length and age data for each region indicated that fish from

the Elephant Island region were significantly larger (p<0.05) than fish of similar age

(p>0.05) in the Weddell Sea or Prydz Bay (Table 6).

During the early development of P. antarcticum, instantaneous growth was

highly variable and influenced by region. From hatch to 10.6 mm SL, fish within

McMurdo Sound had a faster instantaneous growth rate (0.009) than those captured in

the other regions (0.006-0.008). Growth rates calculated using fish between 10.6-

13.7 mm SL were the same (0.005) for all regions. Fish from McMurdo Sound had a

slower growth rate (0.004) once ring two was formed, while fish from the Weddell Sea

demonstrated slightly increased growth rates at this time (0.006; Table 7).

When the total rate of fish growth within each region was calculated, there were

significant between region differences in both instantaneous and absolute growth rates

(Fo.os.,. 107=67.6 and F0.05•3•107=36.99 respectively; p<0.05; Ricker, 1979). The Weddell

Sea had the greatest instantaneous growth rate (0.004). However, the Weddell Sea and 1 9 the Elephant Island area had equally high absolute growth rates (0.074) compared to

McMurdo Sound (0.049; Table 7).

Temporal variability in growth rates was found in fish from Prydz Bay, but not in fish from McMurdo Sound or Elephant Island. Although Kappenman's (1980) criterion suggested that growth in McMurdo Sound and Elephant Island be described using separate curves for each year within each region, these curves were obviously superimposed (Figure 12 a, c). This allows between-year data to be pooled for each region, and growth for that region can be represented by one curve (r=5.15, K=21.97,

Y,=9.46 and r=1.83, K=70.79, Y,=10.895 respectively; Figure 12 a, c). Fish within

Prydz Bay also showed some between-year growth differences. The lowest total sum of squares (4,636) resulted from the combination of each year's sum of squares considered separately. A similar sum of squares (4,934) was calculated when Prydz Bay

1987 and Prydz Bay 1991 were combined and Prydz Bay 1993 was separated. This

negligible difference and graphical similarity allowed Prydz Bay 1987 and 1991 data to

be combined (r=1.31, K=89.80, Y,=1 0.96),while Prydz Bay 1993 considered separately showed r=1.2, K=112.8, Y,=12.33 (Figure 12 b).

Comparisons of regional grow1h characteristics resulted in the use of two logistic

curves. One curve represented samples from the Marguerite Bay, Weddell Sea, and

Elephant Island regions (r=1.844, K=70.115, Y,=11.098) while the other

represented McMurdo Sound and Prydz Bay fishes (r=1.173, K=107.70, Y,=11.35).

The first curve resulted in faster initial growth and a smaller K than the second (Figure

1 3). 20

Interannual comparisons using the von BertalanHy function showed the same characteristics as the logistic curve. McMurdo Sound (L_=23.4, K=2.7, T,=-0.187) and Elephant Island (L_=108.2, K=0.374, and T,=-0.200) were superimposed whereas

Prydz Bay showed that the 1993 data (L_=159, K=0.24, T,=-0.205) differed from

1987 and 1991 (L_=149.27, K=0.22, T,=-0.259; Figure 14 a-c).

Using the von Bertalanffy growth function, regional growth parameters were

best explained by two diHerent curves. Growth within McMurdo Sound was significantly

different from all other regions both graphically and statistically using Kappenman's

(1980) criterion. In contrast, the growth curves for the Marguerite Bay, Weddell Sea,

Elephant Island, and Prydz Bay regions were statistically similar (i.e. within 96% of the best curve sum of squares) and superimposed. Therefore, it was reasonable to

combine growth data from these four regions (L_=183.4, K=0.179, T,=-0.280), while

the data from the McMurdo Sound region were considered separately (L_=23.4, K=2.7,

T,=-0.187; Figure 15).

When three growth curves (Gompertz, von Bertalanffy, and Logistic) were

applied to the entire data set to determine which one best described the growth of P.

antarcticum, the following results were seen: using sum of squares, the Gompertz

function (SS= 701) was considerably better than the other two curves (SS= 8,757 and

10,339 respectively), but it produced a maximum standard length (>500 mm) more

than double that reported for P. antarcticum (245 mm; Figure 16). For this reason as

well as a smaller sum of squares than the logistic curve, the von Bertalanffy growth

function represents the overall growth of P. antarcticum (L_=217.4, K=0.140, T,= -

0.287; Figure 16). 21

Hatch Seasonality

The Elephant Island and Prydz Bay regions (T 0.05121,20=2.09 and Fo.o> 2,33=6. 76

respectively; p<0.05) both showed significantly different between-year mean hatch dates for P. Antarcticum. In the Elephant Island region during 1995, the mean hatch

date was ca. 3.5 months earlier than in 1 996. In the Prydz Bay region, fish collected in

1987 had a later back-calculated hatch date than those in 1991 or 1993 (February vs.

December). In addition, the Prydz Bay region had a much more variable hatching period compared to the other regions. McMurdo Sound showed no interannual variation in mean

hatch date (Table 8).

Though the peak hatching time within McMurdo Sound (March-April) showed no

significant between-year variability (p>0.05), it differed markedly from the other

regions, which conform to that previously reported by Andriashev, 1965; Kellermann,

1 989; Kock and Kellermann, 1991 (October-January). This represents an almost six

month difference in hatch period between McMurdo Sound and the other regions (Table

8).

Growth Seasonality

When the oscillating von Bertalanffy growth function (Newberger and Houde,

1 995) was used in conjunction with modal hatch date for each region, seasonal

fluctuations in growth rates showed that growth was highly variable in seasonal timing

and duration when the entire data set for each sampling period was considered, but a 22 different pattern emerged when only the first year of growth was examined. The points

indicate an almost continuous growth rate in the first year in all regions except

McMurdo Sound. Here, growth rate declines in winter (July to August) and remains

lower until February or March (Figure 17). 23

DISCUSSION

Data Base

Sampling bias resulted in significant differences in mean standard length and

mean age between each sampling event. These differences partly result from sampling technique (e.g. dip net verses rectangular midwater trawl) and location (e.g. depth and

proximity to the ice shelf). Due to vertical and horizontal stratification of the different

life stages (Hubold, 1985a; Kellermann, 1986; Hubold and Tomo, 1 989; Radkte, et al.,

1993), shallow samples (e.g. 0-135 m) or samples collected near ice shelves were

primarily comprised of larvae and early juveniles, while older juveniles and adults

were primarily collected from greater depths and/or offshore waters.

Staging and Shrinkage

Data from this study indicate that P/euragramma antarcticum begins notochord

flexion at a smaller standard length than that previously reported by Keller (1 983).

According to Keller (1 983), notochord flexion of P. antarcticum begins at

approximately 17.8 mm SL, and continues until fin formation (24.6 mm SL); however,

results from the current study indicate that hypural plates begin to form ventrally along

the notochord by 11.0-11.9 mm SL, and flexion occurs between 12.0 to 14.0 mm SL. A

broad size range (12.0-21.9 mm SL) was also representative of the postflexion phase,

which continued to the onset of fin formation (ca. 21.9 mm SL).

Examination of the illustrations provided by Keller (1983) showed that

differences in size at flexion between his study and this study were due to different

interpretations of the term "flexion." Larvae of 11.8 mm SL in Keller's (1 983) 24 illustrations appear to be in the flexion phase (notochord bent with hypural plates not aligned; Moser, 1996) yet he indicated that these were preflexion larvae. In addition,

Keller's (1983) 17.8 mm SL fish which he described as flexion stage appeared to be in the postflexion phase (hypural plates vertical; Moser, 1996).

A true comparison of this study's data to that of Keller (1983) was further hindered by the fact that Keller (1983) used formaldehyde while this study used alcohol as a preservative. Greater shrinkage due to alcohol versus formaldehyde preservation has been reported for capelin (Mallotus vilosus) and silver hake (Mer/uccius bilinearis; Fowler and Smith, 1983; Kruse and Dailey, 1990). Specimens from the current study that were preserved in 100% ethanol were significantly smaller after preservation than upon capture, and shrinkage due to alcohol accounted for approximately 3.0-5.0 mm SL tor all lengths of fish examined. Therefore, because of the 3.0-5.0 mm shrinkage observed due to alcohol, P. antarcticum flex at between

15.0-17.9 mm SL, and all specimens greater than 18.0 mm SL at collection were in the postflexion phase. In contrast, Keller (1983} did not take shrinkage into consideration.

Growth Relationships

Pleuragramma antarcticum undergoes a drastic change in energy expenditure at ca. 90 mm (3-4 yrs. old), when young juveniles are thought to begin a migration offshore to warmer water (Radkte, et. al., 1993}. It is therefore reasonable to assume that energy reserves (i. e., weight} are required to make this journey. A similar ontogenic change in the length to weight relationship is observed in other fishes including the Pacific electric ray (Torpedo ca/ifornica; Neer, 1998) and the Antarctic nototheniid, Trematomus newnesi (Eastman and Devries, 1997). 25

A highly significant relationship between standard length of the fish and otolith diameter was needed to back-calculate and supplement missing data or establish early growth rates. Regression analysis produced an r-squared value greater than 95% for this relationship. The strong relationship between otolith growth and fish growth was further supported by consistency in the regression, as current values were similar to those reported by Radkte (1 993).

Increment Analysis

Metamorphic changes in fish can result in "checks" on the otolith (Kawase, et. al., 1 993; lmai and Tanaka, 1996). A number of checks appeared on otoliths of P. antarcticum. Approximately 15 days after hatch, a prominent organic matrix (O-zone) was deposited on the otolith; this ring corresponded to 10.6 mm SL. Considering that none of the larvae had yolk sacs and that hypural plate formation was underway by 1 1 .0 mm SL, this check could result from yolk absorption and/or first feeding by the larvae.

Based on the formation of this check, it appears that yolk-sac absorption by P. antarcticum larvae occurred at approximately the same standard length regardless of year or region; however, the timing of this check's formation differed regionally. In

McMurdo Sound formation (yolk absorption) occurred 6 days earlier than in the

Elephant Island area. If this is considered in conjunction with hatch size one may speculate that P. antarcticum within McMurdo Sound has a longer incubation time due to colder temperatures (-2 to 0 oc; Appendix C) and therefore hatch at a larger size with less yolk reserves than specimens in the Elephant Island area (-1 to 3 oc; Amos, et. al.,

1995; Amos, et. al., 1 996). 26

Many studies on temperate and tropical fishes indicate that incubation time may be prolonged by decreased temperature (Bigelow and Schroder, 1953; lmai and Tanaka,

1996). For example, incubation times for cod (Gadus morhua) range from 10 days at

8.3 oc to 40 days at 0.0° C (Bigelow and Schroder, 1953).

Assuming that this check is an indicator of yolk absorption, then P. antarcticum appears to reach this stage sooner than some other Antarctic species. Nototheniops nudifrons, Harpagifer antartcicus, and Notothenia neglecta take 3, 5, and 4 weeks respectively between hatch and resorption (Daniels, 1978; Hourigan and Radkte, 1989;

Kock and Kellermann, 1991 ). The longer time for resorption in these three species may be the result of egg diameter and size at hatch. Hatch sizes of N. nudifrons (7 mm SL) and H. antarcticus (8 mm SL) are similair to P. antarcticum (8 mm SL), but both species have a slightly larger egg diameter (2.0-2.5 mm and 2.2-2.6 mm, respectively) than P. antarcticum (1.8-2.0 mm; Kock and Kellermann 1991 ).

Though P. antarcticum has a relatively short resorbtion time compared to some

Antarctic species, this time exceeds that of many temperate and tropical species which require as little as 3-7 days for yolk absorption (i. e., three spined stickleback

(Gasterosteus acu/eatus), white perch (Marone americana), scup (Stenotomus chrysops), tautog (Tautoga onitis), American pollock (Pollachius virens), cusk

(Brosme brosme), Nassau grouper (Epinephe/us striatus) and Canadian plaice

(Hippoglossoides platessoides)). However, absorption rates of a few temperate and subarctic species are similar to those of P. antarcticum (1 0-14 days; i.e. winter flounder (Pseudop/euronectes americanus), witch flounder (Giyptocepha/us 27 cynoglossus), haddock (Melanogrammus aeglefinus), and Siberian sturgeon (Acipenser laeri); Bigelow and Schroder, 1953; Ellis, et al., 1997; Gisbert and Williot, 1997).

BecauseP. antarcticum flex at between 12.0·14.9 mm SL; the second prominent

D zone deposited on the otolith at approximately 64 days post hatch (13.7 mm SL) most likely results from flexion. Length and age at notochord flexion was independent of hatch year or region. The estimated development time for P. antarcticum to reach this stage is considerably longer than reported for temperate species such as the roughskin sculpin

( Trachidermus fasciatus), which requires less than 16 days post-hatch to undergo flexion (Takeshita, et al., 1997). The extended development time needed by larval P. antarcticum is most likely the result of water temperature, which can be less than

3.0"C whereas Trachidermus fasciatus were reared at between 2.3-11.3"C.

The third prominent O-zone deposited on the otolith at approximately tour months post-hatch is presently unexplainable, but could mark the onset of winter and increased darkness. If hatching occurs in December or January this ring would be formed in April or May and thus coincide with the four month continuous dark cycle at high latitudes (McMurdo Sound) reported by Rivkin and Putt (1987).

The Intervals between otolith check marks provide a wealth of information about the early development and growth rates of P. antarcticum. Yolk-reserves allowed P. antarcticum to grow quickly (0.006-0.009) after hatching, but as their early development continued and they relied more on exogenous feeding, instantaneous growth rate declined to 0.005, and remained so through flexion. Similarly, Canino (1997) reported a slowing of growth rate after first feeding by walleye pollack ( Theragra 28 cha/cogramma). As P. antarcticum aged beyond flexion, the instantaneous growth rate decreased further to 0.002-0.004.

Early absolute growth rates established here for P. antarcticum (ca. 0.07 mm/day for the first seven months of development) were comparable to those in the literature. Guglielmo, et al. (1998) reported a value of 0.08 mm/day for the first year of life. Cohort analysis of 1980 and 1981 data provided by Hubold (1985a) yielded an absolute value of 0.05 mm/day; while a value of 0.06 mm/day was produced using static analysis. Static analysis applied to data provided by Regan (1916) produced an absolute growth rate of 0.06 mm/day between December and September. As with early absolute growth rates, the overall absolute growth rate of 0.07 mm/day is comparable to that presented in the literature. Hubold (1985a) assigned ages of 7, 9,

11, and 12 years for fish of 165, 175, 210, and 225 mm SL respectively, which correspond to absolute growth rates of 0.05-0.06 mm/day.

Generally, growth rates of Antarctic and deep-sea fishes are considerably slower than those of fishes in temperate and tropical areas (Knox 1994). The slow growth rate of P. antarcticum is comparable to some other Antarctic fish such as Champsocephalus gunnari (mackerel icefish, 0.09 mm/day; Radkte, 1989) and Trematomus bernacchii

(La Mesa, et al., 1996). While the growth rate of the Antarctic fish, Notothenia rossii

{Antarctic cod) is comparatively fast 0.21 mm/day (Radkte, 1989), it is still lower than that of many temperate species (e. g., shad, Alosa sapidissima, 0.42 mm/day; haddock, Melanogrammus aeglefinus, 0.30 mm/day; Atlantic halibut, Hippoglossus hippog/ossus, 0.29 mm/day; Canadian plaice, Hippoglossoides platessoides, 0.40 mm/day; sea raven, Hemitripterus americanus, 0.32 mm/day; Tautog, Tautoga onitis, 29

0.28 mm/day; and American goosefish, Lophius americanus, 0.49 mm/day). Examples of two temperate water species with growth rates similar to Antarctic fishes are the rosefish (Sebastes marinus, 0.09 mm/day) and shorthorn sculpin (Myoxocephalus scorpius, 0.08 mm/day); however, both species inhabit deeper (732 m) and/or colder waters (1.7-15.5° C) than most other species reported (Bigelow and Schroder, 1953).

Pleuragramma antarcticum from Prydz Bay demonstrated between-year differences in growth rates. However, these differences most likely resulted from sampling bias, specifically the lack of specimens older than four years of age for 1987 and 1991 and the poor fit of the logistic curve (SS=3767) in 1993, when older individuals were included (Figure 12 b). Moreau (1987) also reported difficulties in fitting the logistic curve to fish growth throughout the life span of a fish.

Regional differences in growth rates were also apparent in that fish from

McMurdo Sound and Prydz Bay differed from those from Marguerite Bay, Weddell Sea, and Elephant Island combined. Again, the apparent difference in specimens from Prydz

Bay was likely due to the poor logistic fit. However, the slower growth rate of fish from

McMurdo Sound is more likely a product of environmental conditions (i.e., colder temperatures and food limitation).

Despite its appropriate fit for many sampling periods in this study, the logistic function failed to adequately assess the growth of P. antarcticum when older individuals from Prydz Bay in 1993 were included ; furthermore, this function is not the one generally reported in the literature. This is why between-year and regional growth rates were also assessed using the von Bertalanffy function. Both the logistic curve and von Bertalanffy growth function suggest apparent between-year differences within 30

Prydz Bay probably due to incomplete size range coverage. The von Bertalanffy function also produced between-region differences, in that fish from McMurdo Sound had different growth rates than those pooled from Marguerite Bay, Weddell Sea, Prydz Bay and Elephant Island regions. Prydz Bay is no longer considered separate, graphically or using Kappenman's criterion, because the von Bertalanffy curve was more accurate in incorporating the larger individuals into the analysis. Due to the persistent difference of growth rates from McMurdo Sound in these analyses, they are more likely real and result from environmental factors.

Hatch dates from six of the nine sampling events (Marguerite Bay; Elephant

Island 1996; Weddell Sea; and Prydz Bay 1987, 1991, and 1993 ) conformed to the

October-December hatch periods reported by Andriashev, 1965, Kellermann, 1989, and Kock and Kellermann, 1991; while hatch dates from Elephant Island (1995) and

McMurdo Sound (1992 and1993) did not. Fish captured in the Elephant Island region during 1995 had a much earlier mean hatching season {late July), which may have been the result of source location or hatching year. In contrast, fish from McMurdo Sound did not begin hatching until January-April, well after the reported hatching season. This delay may be a direct result of the environment limiting development at different levels

(egg to adult).

There is ample evidence suggesting that P. antarcticum is not being spawned within the Elephant Island region. Pleuragramma antarcticum spawns in proximity to permanent sea ice (Hubold, 1984; Eastman, 1985; Kellermann, 1986; Kock and

Kellermann, 1991 ), yet Elephant Island is located within the seasonal sea ice zone.

This, coupled with the fact that the majority (91 %) of specimens collected in both 1995 31 and 1996 near Elephant Island were migratory pelagic juveniles (2-4 years; Radkte, et al., 1993), suggests that P. antarcticum is supplied to this area from elsewhere.

Therefore, the yearly variability in hatch date of these individuals could be the result of different source locations (e. g. Weddell Sea to the East and Bellingheusen Sea to the

West) to this area.

Though the influence of different watermasses and source locations may vary annually within the Elephant Island region, trends in hatch date were similar regardless of watermass. One specimen collected in 1996 was associated with water originating in

Bransfield Strait (probably Gerlache Strait source) whereas the remainder were captured in Drake Passage-Shelf Water (possibly Bellingheusen Sea source; Amos, et al., 1996). In 1995, two fish were collected from water originating in the Weddell Sea while the remainder were associated with Bransfield Strait water (Amos, et al., 1995).

Despite the different watermass associations in 1995, the specimens in 1995 showed a similar range of hatch date (May-October). In addition, it is uncertain whether the juveniles remained in the watermass in which they were spawned.

Determination of hatch seasonality within the Elephant Island area was complicated by the fact that samples collected there represented many different cohorts, each of which was exposed to different environmental conditions present before spawning to hatching. The specimens collected in 1995 were hatched in May-October 1993 and late August 1994, while specimens collected in 1996 were hatched in September 1992,

June-November 1993, July 1994, and October 1995. It appears that fish which hatched during 1993 experienced the broadest temporal range (May-November) and 32 therefore were the product of extended spawning. This is in contrast to other years when

hatching was limited to one (1992 and 1995) or two months (1994).

Interannual variability in hatching seasonality and duration may be influenced by the availability and condition of important prey items. Spawning of P. antarcticum in the Weddell Sea, Bransfield Strait and the Antarctic Peninsula region is reported to occur from August to September (Andriashev, 1965; Kellermann, 1989; Loeb, 1991;

Kock and Kellermann, 1991; Kellermann and Schadwinkel, 1991 ); this is late austral

winter/ early spring when resources are limited. Though P. antarcticum is able to feed throughout the winter, the food source is often less nutritious. Kellermann and

Schadwinkel (1991) suggest that adult P. antarcticum feed primarily on copepods throughout the winter instead of E. superba, amphipods, larval krill, or E.

crystallorophias. In addition, Hubold and Hagen (1997) found that juvenile P.

antarcticum (> 60 mm) prey on large calanoids ( Ca/anoides acutus and Metridia

gerlachel) in the summer verses Ca/anus propinquus in the winter. Hubold and Hagen

(1997) also state that lipid content of P. antarcticum {30-80 mm) does not vary

seasonally; however, their data appear to show a significant difference between winter

and summer and only juvenile specimens were examined. Keeping this in mind, it

seems likely that the bulk of spawning energy needed is gained in the summer

(November-March; Eastman, 1993) and maintained through winter when the

individuals feed on a less nutritious source.

Timing and extent of seasonal sea-ice formation may be a factor in determining

the availability of food resources. Winters of both 1992 and 1993 were considered

below average in sea-ice index throughout the Southern Ocean (Smith, et al., 1998), 33 including Elephant Island (s 4.66 X1 06 km 2-month). The low ice development in late

6 2 1992 (4.27 X10 km -month, Elephant Island) and early 1993 (3.91 X106 km 2- month, Elephant Island) may have allowed the spawning adults of 1993 to consume more nutritious food in the winter of 1992 thus allowing them to spawn earlier and continue longer (hatch=May-November). Ice conditions in 1994 were average to slightly above average (4.86 X1 06 km 2-month, Elephant Island; Smith, et al., 1998). In this case, hatching time was still slightly earlier (July-late August) than that reported in the literature. This could again be due to a higher abundance of winter food during the prior low ice year (1993). However, spawning in 1994 was abbreviated because it was an average ice year with little winter food available. Conversely, fish born in 1992, a below average ice year which followed an above average ice year (Smith, et al., 1998), hatched in September. This nearly "typical" hatching time could be due to the lack of reserves available from the previous year (1991 ). Specimens which were hatched in

1995, an above average ice year (5.00 X1 06 km 2-month, Elephant Island) conformed to reported values. Thus, adults which are able to feed on nutritious prey items (e.g. euphausiids) throughout the prior year are able to begin spawning earlier, and if these conditions continue, spawning season can be extended.

Since adults typically spawn in the austral winter (August-September;

Andriashev, 1965; Kellermann, 1989; Kock and Kellermann, 1991; Kellermann and

Schadwinkel, 1991; Loeb, 1991), it is reasonable to assume that the environmental conditions during the preceding austral late summer-fall are important for building energy reserves. Within McMurdo Sound, consistently low temperatures (e.g., -2.0°C to 0.0°C vs. Marguerite Bay, 0.0-2.0°C; and Weddell Sea -2.0 -2.0°C) coupled with low 34 prey availability (e. g., E. crystallophorias, Ca/anoides acutus, Ca/anus propinquus;

Metridia gerlachei, and Limacina he/icina; Table 5 and Appendix D) may force adults to delay spawning until after the onset of the following austral summer (November to

February; Eastman, 1993) to attain additional energy, this in turn, delays hatching until March or April. In contrast to areas like the Weddell Sea where E. superba and E. crystallorophias co-exist, E. superba is absent within McMurdo Sound. The absence of this important prey item forces P. antarcticum to rely heavily on other prey items such as copepods, E. crystallorophias, and even its own larvae. In addition to slightly warmer temperatures, the austral summer brings sea-ice retreat, increased primary production (0.78-2.63 gC/m 2d; Smith, et al., 1996), and spawning of E. crystallorophias (November-December; Kirkwood, 1996; Pakhomov and Perissinotto,

1996) and C. acutus (December-January; Huntley and Escritor, 1991 ). An influx of food resources (e.g. young E. crystallorophias and C. acutus) may provide the necessary energy to initiate summer spawning by P. antarcticum. Delayed spawning seasonality is also reported for Trematomus hansoni and Chionodraco hamatus in the Ross Sea verses the Mawson Sea (Vacchi, et al. 1996).

In addition to delayed spawning, P. antarcticum eggs may undergo prolonged incubations due to consistently low water column temperatures (-2.0°C-o.ooc; Table

5). This is further supported by the fact that larvae from McMurdo Sound absorb their yolk reserves faster than in the other areas. Once hatched, larvae from McMurdo Sound grow rapidly thus decreasing the time when they are most vulnerable to predation by adults of P. antarcticum and other fishes (e.g. channichthyids). The increased growth rate early in development may also be a product of the warmer temperatures (late 35

austral summer) and available food, potentially calyptopis stage E. crystallorophias,

which occur in the water column, before the onset of winter (Kirkwood, 1996). Harsh temperatures and low food availability within McMurdo Sound during the winter appears to cause a comparatively sharp decline in growth rate, and it is this decline that

probably accounts for the regional deviation in calculated growth parameters.

The von Bertalanffy growth function produced an asymptotic length of 217.4 mm

SL which is similar to the 211 mm SL value reported by Radkte (1993), but much

lower than 308 mm SL reported by Hubold and Tomo (1989). In both cases (Hubold and

Tomo, 1989; Radkte, 1993) the K value was considerably lower (0.07) than the 0.14

calculated here; however, they examined multiple specimens in excess of 200 mm SL

whereas none were available in this study.

If one extends the curve to this study's asymptotic value of 217.4 mm, it can be

shown that P. antarcticum is long lived (52 years) and late maturing. Kock and

Kellermann (1991) stated that sexual maturity of this species is reached by 60-70%

body length. If this is true then P. antarcticum mature at 141 mm SL and

approximately 7 years of age. This age and size of maturity agree with that reported in

Hubold (1985b, 140 mm), Hubold and Tomo (1989, 7-8 years), and Kock and

Kellermann (1991, 6-7 years).

Though P. antarcticum is not heavily exploited by a direct fishery, there is a

risk of depleting the population by taking this long-lived and late maturing fish as by­

catch in the krill (E. superba) fishery. Fish constitute at least 4% by weight of the total

catch in tows aimed at capturing E. superba along the continental shelf of the Prydz Bay

region; P. antarcticum comprises 95% of this by-catch (Williams, 1985a). As the 36

demand for E superba increases, there is a potential for reducing the number of

developing juveniles as well as the late maturing spawning stocks of P. antarcticum. As

is the case for many slow growing, long-lived and late maturing species (Grimes and

Turner, 1999; Sedberry, et al., 1999; Stevens, 1999;}, these stocks would rebound

slowly from any "overfishing."

Due to its susceptibility to "overfishing" coupled with its importance in the

Antarctic food web, further research must be done to better understand the cause and

effects of environmental change on P. antarcticum. Some possilities for future

research would include widespread sampling (e. g. multiple locations including McMurdo

Sound), rearing experiments and age validation. One way to determine the importance of

either delayed spawning or prolonged incubation times on hatch seasonality is to compare gonadal condition indices overtime as well as between regions. In conjunction with this,

cultures of eggs should be reared to the larval stages at a variety of temperatures (-2 to

3•C) thus allowing researchers to calculate temperature dependent incubation times as well as determine the role of temperature on larval development (e.g. yolk absorption or

flexion). Use of reared larvae of known ages in an aging experiment would also allow

researchers to confirm or refute the validity of using a single ring to denote daily

growth in P. antarcticum. LITERATURE CITED 38

Literature Cited

AI-Hassan, L.A.J., Saleem, S. D., and M.K. Kelkonian. 1993. Effect of freezing, formalin, and alcohol on certain body proportions of the clupeid fish Nematalosa nasus, collected from the Khor al- Zubair area (northwest region of the Arabian Gull}. Acta Hydrobiol. 35(2}:179-183.

Amos, A. F., Rowe, C., and A. Wickham. 1996. Physical Oceanography. AMLR Field Season Report. NOAA Administrative Report LJ-95-13. La Jolla, CA. pp 16-33.

Amos, A. F., Wickham, A., and C. Rowe. 1995. Physical oceanography. AMLR Field Season Report. NOAA Administrative Report LJ-96-15. La Jolla, CA. pp 14-32.

Andriashev, A. P. 1965. A general review of the Antarctic fish fauna. In Van Mieghem, I. and P. Van Oye (eds}. Biogeography and Ecology in Antarctica. The Hague: W. Junk, pp 491-550.

Bargelloni, L. and G. Lecointre. 1998. Four years in notothenioid systematics: A molecular perspective. In G. di Prisco, E. Pisano, and A. Clarke (eds}. Fishes of Antarctica. A Biological Review. Springer-Verlag, Italy. pp 259-273.

Beamish, R. J. and D. A. Fournier. 1981. A method for comparing the precision of a set of age determinations. Can. J. Fish. Aqua!. Sci. 38:982-983.

Beaumont, K. L. and G. W. Hosie. 1997. Mesoscale distribution and abundance of four pelagic copepod species in Prydz Bay. Ant. Sci. 9(2}:121-133.

Bigelow, H. B. and W. C. Schroder. (eds}. 1953. Fishes of the Gulf of Maine. Fishery Bulletin 74. U.S. Government Printing Office. Washington DC. 577 pp.

Boysen-Ennen, E., W. and U. Piatkowski. 1988. Meso- and macrozooplankton communities in the Weddell Sea, Antarctica. Polar Bioi. 9:17-35.

Boysen-Ennen, E., Hagen, W., Hubold, G., and U. Piatkowski. 1991. Zooplankton biomass in the ice-covered Weddell Sea, Antarctica. Mar. Bioi. 111:227-235.

Brinton, E. 1991. Distribution and population structure of immature and adult Euphausia superba in the western Bransfield Strait region during the 1986-87 summer. Deep-Sea Res I. 38(8/9A}:1169-1193.

Brothers, E. B., Mathews C. P., and R. Lasker. 1976. Daily growth increments in otoliths from larval and adult fishes. Fish. Bull. 74(1}:1-8 39

Budnichencko, E. V. and N. C. Khromov. 1988. Biomass of mesoplankton, age composition and the distribution of dominant species in relation to the hydrological structure of the Sodruzhesiva and Kosmonavtov seas. Collection of Scientific Papers. VNIRO Publishers. Moscow. 40 pp.

Canine, M. F. 1997. Nucleic acid contents and growth of first feeding walleye pollack larvae in response to prey densities typical of sub-arctic ecosystems. J. Fish Bioi. 51 (1 ):41-52.

Chang, W. Y. B. 1982. A statistical method for evaluating the reproducibility of age determinations. Can. J. Fish. Aqua!. Sci. 39:1208-1210.

Cheng, C.H.C. 1998. Origin and mechanism of evolution of antifreeze glycoproteins in polar fishes. In di Prisco, G., Pisano, E., and A. Clarke (eds). Fishes of Antarctica. A Biological Review. Springer-Verlag. Italy. pp 259·273.

Daniels, R. A. 1978. Nesting behaviour of Harpagifer bispinis in Arthur Harbor, Antarctic Peninsula. J. Fish Bioi. 12:465-474.

Daniels, R. A. 1982. Feeding ecology of some fishes of the Antarctic Peninsula. Fish. Bull. U. S. 80:575-588.

DeVries, A. L. 1982. Biological antifreeze agents in coldwater fish. Comp. Biochem. Physiol. 73A:627 -640.

DeVries, A. L. and J. T. Eastman. 1978. Lipid sacs as buoyancy adaptation in an Antarctic fish. Nature 271 :352-353.

Dewitt, H. H. 1970. The character of the midwater fish fauna of the Ross Sea, Antarctica. In Holdgate, M. W. (ed). Antarctic Ecology, Vol. 1, Academic Press, London. pp 305·314.

Dewitt, H. H. and T. L. Hopkins. 1977. Aspects of the diet of the Antarctic silverfish, Pleuragramma antarcticum. In Llano, G. A. (ed). Adaptations within Antarctic Ecosystems. Smithsonian Institution, Washington DC. pp 557-567.

Eastman, J. T. 1985. Pleuragramma antarcticum (Pisces, Notothenfidae) as food for other fishes in McMurdo Sound, Antarctica. Polar Bioi. 4:155-160.

Eastman, J. T. 1988. Ocular morphology in Antarctic notothenoid fishes. J. Morpho!. 196:283-306.

Eastman, J. T. (ed). 1993. Antarctic Fish Biology: Evolution in a Unique Environment. Academic Press. pp 162-163. 40

Eastman, J. T. and A. L DeVries. 1981. Buoyancy adaptations in a swimbladderless Antarctic fish. J. Morph. 167:91·102.

Eastman, J. T. and A. L. Devries. 1997. Biology and phenotypic plasticity of the Antarctic nototheniid fish Trematomus newnesi in McMurdo Sound. Ant. Sci. 9(1):27- 35.

Ellis, E. P., Watanabe, W.O., Ellis, S.C., Ginoza, J., and A. Moriwake. 1997. Effects of turbulence, salinity, and light intensity on hatching rate and survival of larval Nassau grouper, Epinephelus striatus. J. Appl. Aquacult. 7(3):33-43.

Foster, B. A. 1989. Time and depth comparisons of sub-ice zooplankton in McMurdo Sound, Antarctica. Polar Bioi. 9(7):431-435.

Fowler, G.M. and S.J. Smith. 1983. Length changes in silver hake (Merluccius bilinearis) larvae: Effects of formalin, ethanol, and freezing. Can. J. Fish. Aqua!. Sci. 40(7):866-870.

Fuhrman, J. A. and F. Azam. 1980. Bacterioplankton secondary production estimates for coastal waters of British Columbia, Antarctica, and California. Applied Environmental Microbiology 39:1085-1095.

Gerasimchuk, V. V. 1986. Characteristics of Antarctic silverfish, Pleuragramma antarcticum (Nototheniidae), from Olaf-Pruds Bay (Commonwealth Sea, eastern Antarctica) with notes on the identification of the species. J. lchthyol. 26(5):10-17.

Gerasimchuk, V. V. 1988. On the fecundity of Antarctic sidestripe, Pleuragramma antarcticum. J. lchthyol. 28(1):98-100.

Giardina, B., Mordents, A., Zappacosta, B., Calla, C., Colacicco, L., Gozzo, M. L., and S. Lippa. 1998. The oxidative metabolism of Antarctic fish: Some peculiar aspects of cold adaptation. In G. di Prisco, E. Pisano, and A. Clarke (eds). Fishes of Antarctica. A Biological Review. Springer-Verlag. Italy. pp 129-138.

Gisbert, E. and P. Williot. 1997. Larval behavior and effect of te timing of intial feeding on growth and survival of Siberian sturgeon (Acipenser laert) larvae under small scale hatchery production. Aquaculture. 156(1·2): 63-76.

Glenn, C.L. and J.A. Mathias. 1987. Body shrinkage in young walleye, Stizostedion vitreum, preserved with AFA, formalin, ethanol, and quick freezing. Can. Field-Nat. 101 (3):408-414.

Gon, 0. and P. C. Heemstra. (eds). 1990. Fishes of the Southern Ocean. J. L. B. Smith Institute of Ichthyology, Grahamstown, South Africa. 462 pp. 41

Greer-Walker, M. and G. A. Pull. 1975. A survey of red and white muscle in marine fish. J. Fish Bioi. 7:295-300.

Grimes, C. B. and S. C. Turner. 1999. The complex life history of tilefish Lopholatilus chamaeleonticeps and vulnerability to exploitation. In Musick, J. A. (ed). Life in the Slow Lane. American Fisheries Symposium 23. Bethesda, Maryland. pp. 17-26.

Guglielmo, L., Granata, A., and S. Greco. 1998. Distribution and abundance of postlarval and juvenile Pleuragramma antarcticum (Pisces, Nototheniidae) off Terra Nova Bay (Ross Sea, Antarctica). Polar Bioi. 19(1 ):37-51.

Hebling, E. W., Villafane, V. E., and 0. Holm-Hansen. 1995. Variability of phytoplankton distribution and primary production around Elephant Island, Antarctica, during 1990-1993. Polar Bioi. 15:233-246.

Hebling, E. W., Villafane, V. E., Calvete, T. C., Hernando, M. P., and 0. Holm-Hansen. 1996. Phytoplankton. AMLR Field Season Report. NOAA Administrative Report LJ-96- 15. La Jolla, CA. pp 32-43.

Hjoerleifsson, E. and G. Klein-MacPhee. 1992. Estimation of live standard length of winter flounder P/euronectes americanus larvae from formalin-preserved, ethanol­ preserved and frozen specimens. Mar. Ecol. Prog. Ser. 82(1):13-19.

Holm-Hansen, 0. and B. G. Mitchell. 1991. Spatial and temporal distribution of phytoplankton and primary production in the western Bransfield Strait region. Deep­ Sea Res. I 38(8/9A):961-980.

Holm-Hansen, 0., Hebling, E. W., Figueroa, S., Montes, M., Valenzuela, C., Rojas, L. L., and V. E. Villafane. 1995. Phytoplankton. AMLR Field Season Report. NOAA Administrative Report LJ-95-13. La Jolla, CA. pp 33-45.

Hopkins, T. L. 1985. Food web of an Antarctic midwater ecosystem. Mar. Bioi. 89:197-212.

Hopkins, T. L. 1987. Midwater food web in McMurdo Sound, Ross Sea, Antarctica. Mar. Bioi. 96:93-106.

Hopkins, T. L. and J. J. Torres. 1988. The zooplankton community in the vicinity of the ice edge, western Weddell Sea, March 1986. Polar Bioi. 9:79-87.

Hopkins, T. L. and J. J. Torres. 1989. Midwater food web in the vicinity of a marginal ice zone in the western Weddell Sea. Deep-Sea Res. I 36(4):543-560.

Hosie, G. W. 1991. Distribution and abundance of euphausiid larvae in the Prydz Bay region, Antarctica. Ant. Sci. 3(2):167-180. 42

Hosie, G. W. and T. G. Cochran. 1994. Mesoscale distribution patterns of macrozooplankton communities in Prydz Bay, Antarctica-January to February 1991. Mar. Ecol. Prog. Ser. 106:21-39.

Hosie, G. W., Cochran, T. G., Pauly, T., Beaumont, K. L., Wright, S. W., and J. Kitchener. 1997. The zooplankton community structure of Prydz Bay, January­ February 1993. Proceedings of the NIPR Symposium on Polar Biology 10:90-134.

Hosie, G. W. and M. Stolp. 1989. Krill and zooplankton in the western Prydz Bay region, September-November 1985. Proceedings of the NIPR Symposium on Polar Biology 2:34-45.

Hourigan, T. F. and R. L. Radkte. 1989. Reproduction of the Antarctic fish Nototheniops nudifrons. Mar. Bioi. 100:277-283.

Hubold, G. 1984. Spatial distribution of Pleuragramma antarcticum (Pisces: Nototheniidae) near Filcher and Larsen Ice Shelves (Weddell Sea, Antarctica). Polar Bioi. 3:231-236.

Hubold, G. 1985a. The early life history of the High-Antarctic silverfish, Pleuragramma antarcticum. In Siegfried, W. R., Candy, P. R., and R. M. Laws (eds}. Antarctic Nutrient Cycles and Food Webs. Proceedings of the 4th SCAR Symposium on Antarctic Biology. Springer-Verlag. Berlin. pp 445-451.

Hubold, G. 1985b. Stomach contents of the Antarctic silverfish, Pleuragramma antarcticum from the southern and eastern Weddell Sea (Antarctica). Polar Bioi. 5:43- 48.

Hubold, G. 1989. Seasonal patterns of ichthyoplankton distribution and abundance in the southern Weddell Sea. Fifth Symposium Antarctic Biology, Hobart, Tasmania 1988. pp 149-158.

Hubold, G. and W. Ekau. 1987. Midwater fish fauna in the Weddell sea, Antarctica. In Kullander, S. 0. and B. Fernholm (eds). Fifth Congress of European Ichthyologists, Proceedings, Stockholm, 1985. Swedish Museum of Natural History, Stockholm. pp. 391-396.

Hubold, G. and W. Hagen. 1997. Seasonality of feeding and lipid content in juvenile Pleuragramma antarcticum (Pisces: Nototheniidae) from the southern Weddell Sea. In Battaglia, B., Valencia, J., and D. W. H. Walton (eds}. Antarctic Communities: Species, Structure and Survival. Cambridge University Press, Cambridge, UK. pp. 277-283.

Hubold, G. and I. Hempel. 1987. Seasonal variability of zooplankton in the southern Weddell Sea. Meeresforschung. 31:185-192. 43

Hubold, G. and P. Tomo. 1989. Age and growth of the Antarctic silverfish, P/euragramma antarcticum Boulenger, 1902, from the Southern Weddell Sea and Antarctic Peninsula. Polar Bioi. 9:205-212.

Huntley, M. and F. Escritor. 1991. Dynamics of Ca/anoides acutus (Copepoda: Calanoida) in Antarctic coastal waters. Deep-Sea Res. I. 38(8/9A):1 145-1167.

Huntley, M., Karl, D. M., Niller, P., and 0. Holm-Hansen. 1991. Research on Antarctic coastal ecosystem rates (RACER): An interdisciplinary field experiment. Deep-Sea Res. I. 38(8/9A): 911-941.

lmai, C. and S. Tanaka. 1996. Effects of sea water temperature on growth under unfed conditions and marginal feeding conditions for first feeding in Japanese anchovy (Engrau/is japonicus) larvae. J. Nat!. Fish. Univ. 45(2):39-45.

Johnston, T.A. and J. A. Mathias. 1993. Length reduction and dry weight loss in frozen and formalin-preserved larval walleye, Stizostedion vitreum (Mitchill). Aquacult. Fish. Manage. 24(3):365-371.

Kappenman, R. F. 1980. A method for growth curve comparisons. Fish. Bull. 79(1 ):95-1 01.

Kaufmann, R. S., Smith, K. L. Jr., Baldwin, R. J., Glatts, R. C., Robison, B. H., and K. R. Reisenbichler. 1995. Effects of seasonal pack ice on the distribution of macrozooplankton and micronekton in the northwestern Weddell Sea. Mar. Bioi. 124:387-397.

Kawase, H., Mochioka, N., and A. Nakazono. 1993. Otolith increment formation and planktonic larval duration of a temperate damselfish, Chromis notatus notatus. Jap. J. lchthyol. 40(3):377-380.

Keller, R. 1 983. Contributions to the early life history of Pleuragramma antarcticum Boul. 1902 (Pisces, Notothenioidei) in the Weddell Sea. Meeresforschung. 30:10-24.

Kellermann, A. 1986. Geographical distribution and abundance of postlarval and juvenile Pleuragramma antarcticum (Pisces, Notothenioidei) off the Antarctic Peninsula. Polar Bioi. 6:111-119.

Kellermann, A. 1989. The larval fish community in the zone of seasonal ice cover and its seasonal and interannual variability. Atchiv fur Fischereiwissenschaft. 39:89- 109.

Kellermann, A. and K.-H. Kock. 1984. Postlarval and juvenile notothenioids (Pisces, Perciformes) in the Southern Scotia Sea and Northern Weddell Sea during FIB EX 1981. Meeresforschung. 30:82-93. 44

Kellermann, A. and S. Schadwinkel. 1991. Winter aspects of the ichthyoplankton community in Antarctic Peninsula waters. Polar Bioi. 11(2):162-174.

Kirkwood, J. M. 1996. The developmental rate of Euphausia crystallorophias larvae in Ellis Fjord, Vestfold Hills, Antarctica. Polar Bioi. 16:527-530.

Knox, G. A. (eds). 1994. The Biology of the Southern Ocean. Cambridge University Press, Great Britain. 444 pp.

Kock, K. and A. Kellermann. 1991. Reproduction in Antarctic fish-a review. Antarctic Sci. 3(2):125-150.

Kottmeier, S. T., Grossi, S. M., and C. W. Sullivan. 1987. Sea ice microbial communities. VIII. Bacterial production in annual sea ice of McMurdo Sound, Antarctica. Mar. Ecol. Progress. Ser. 35:175-186.

Kruse, G. H. and E. L. Dailey. 1990. Length changes in capelin, Mallotus villosus (Mueller), larvae due to preservation in formalin and anhydrous alcohol. J. Fish Bioi. 36(4):619-621.

La Mesa, M., Arneri, E., Giannetti, G., Greco, S., and M. Vacchi. 1996. Age and growth of the nototheniid fish Trematomus bernacchii Boulenger from Terra Nova Bay, Antarctica. Polar Bioi. 16(2): 139-145.

Lancraft, T. M., Torres, J. J., and T. L. Hopkins. 1989. Micronekton and macrozooplankton in the open waters near Antarctic ice edge zones (AMERIEZ 1983 and 1986). Polar Bioi. 9:225-233.

Loeb, V. J. 1991. Distribution and abundance of larval fishes collected in the western Bransfield Strait region, 1986-1987. Deep-Sea Res. I. 38(8/9A):1251-1260.

Loeb, V. J., Kellermann, A. K., Koubbi, P., North, A. W., and M. G. White. 1993. Antarctic larval fish assemblages: a review. Bull. Mar. Sci. 53(2):416-419.

Loeb, V. J., Nebenzahl, D., Outram, D., Force, M., Phleger, R., Rosenberg, J., Setran, A., Shigenaka, G., and C. Zapata. 1995. Direct krill and zooplankton sampling. AMLR Field Season Report. NOAA Administrative Report LJ-95-13. La Jolla, CA. pp 53-89.

Loeb, V. J., Outram, D., Siegel, V., Armstrong, W., Cobb, W. T., Force, M., Phleger, C. F., Silva-Azevedo, G., and R. Vender. 1996. Direct krill and zooplankton sampling. AMLR Field Season Report. NOAA Administrative Report LJ-96-15. La Jolla, CA. pp 51-92.

Loeb, V. J., Siegel, V., Holm-Hansen, 0., Hewitt, R., Fraser, W., Trivelpiece, W., and S. Trivelpiece. 1997. Effects of sea-ice extent and krill and salp dominance on the Antarctic food web. Nature 387:897-900. 45

Lough, R. G., Pennington, M., Holz, G. R., and A. A. Rosenburg. 1982. Age and growth of larval Atlantic herring, C/upea harengus L., in the Gulf of Maine-Georges Bank region based on otolith growth increments. U. S. Fish. Bull. 80:187-199.

Miquel, J. C. 1991. Distribution and abundance of post-larval krill (Euphausia superba Dana) near Prydz Bay in summer with reference to environmental conditions. Ant. Sci. 3(3):279-292.

Moreau,J. 1987. Mathematical and biological expression of growth in fishes: Recent trends and further developments. In Summerfelt, R. C. and G. E. Hall (eds). Age and Growth of Fish. Iowa State University Press. Ames, Iowa. pp 81-113.

Moser, H. G. (ed). 1996. The Early Stages of Fishes in the California Current Region. Calif. Coop. Ocean. Fish. Invest. Atlas No 33. Allen Press Inc., Kansas. 1505 pp.

Neer, J. A. 1998. Life History of the Pacific Electric Ray, Torpedo californica (Ayres), in Central and Southern California. Masters Thesis, San Jose State University. San Jose, CA. 62pp.

Newberger, T. A. and E. D. Houde. 1995. Population biology of bay anchovy Anchoa mitchilli in the mid Chesapeake Bay. Mar. Ecol. Prog. Ser. 116:25-37.

North, A. W. 1990. Ecological Studies of Antarctic Fish with Emphasis on the Early Development of Inshore Stages at South Georgia. Ph. D. thesis. British Antarctic Survey, Cambridge. 319 pp.

Nunnes Vaz, R. A. and G. W. Lennon. 1996. Physical oceanography of the Prydz Bay region of Antarctic waters. Deep-Sea Res. I. 43(5):603-641.

Pakhomov, E. A. and R. Perissinotto. 1996. Antarctic neritic krill Euphausia crystallorophias: Spatia-temporal distribution, growth, and grazing rates. Deep-sea Res. I. 43(1 ):59-87.

Pannella, G. 1971. Fish otoliths: daily grow1h layers and periodical patterns. Science 173:1124-1127.

Radkte, R. L. 1989. Age determination of the Antarctic fishes Champsocepha/us gunnari and Notothenia rossi marmora/a from South Georgia. Polar Bioi. 10:321-327.

Radkte, R. L. and T. F. Hourigan. 1990. Age and growth of the Antarctic fish Nototheniops nudifrof]s. Fish. Bull. 88(3):557-571.

Radkte, R. L., Hubold, G., Folsom, S. D., and P. H. Lenz. 1993. Otolith structural and chemical analyses: the key to resolving age and grow1h of the Antarctic silverfish, P/euragramma antarcticum. Antarctic Sci. 5(1 ):51-62. 46

Radkte, R. L., Targett, T. E., Kellermann, A., Bell, J. L., and K. T. Hill. 1989. Antarctic fish growth: profile of Trematomus newnesi. Mar. Eco. Prog. Ser. 57:103· 117.

Regan, C. T. 1916. Larval and postlarval fishes, British Antarctic "Terra Nova" Expedition 1910. Nat. Hist. Rep. Zool. 1 (4):125-156.

Ricker, W. E. 1979. Growth rates and models. In Hoar, W. S., Randall, D. J., and J. R. Brett (eds). Fish Physiology (Volume VIII): Bioenergetics and Growth. Academic Press. pp 677-743.

Ricker, W. E. 1992. Back-calculation of fish lengths based on the proportionality between scale and length increments. Can. J. Fish. Aqua!. Sci. 49:1018-1026.

Rivkin, R. B. and M. Putt. 1987. Diel periodicity of photosynthesis in polar phytoplankton: Influence on primary production. Science. 238: 1285-1288.

Secor, D. H., Dean, J. M., and S. E. Campana. (eds). 1995. Recent Development in Fish and Otolith Research. University South Carolina Press. Columbia, SC. 735 pp.

Secor, D. H., Dean, J. M., and E. H. Laban. 1992. Otolith removal and preparation for microstructural examination. In Stevenson, D. K. and S. E. Campana (eds). Otolith Microstructural Examination and Analysis. Can. Spec. Publ. Fish. Aquat. Sci. (117):126.

Sedberry, G. R., Andrade, C. A., Carlin, J. L., Chapman, R. W., Luckhurst, B. E., Manooch, C. S. Ill, Menezes, G., Thomsen, B., and G. F. Ulrich. 1999. Wrecktish Polyprion americanus in the North Atlantic: fisheries, biology. and management of a widely distributed and long-lived fish. In Musick, J. A. (ed). Life in the Slow Lane. American Fisheries Symposium 23. Bethesda, Maryland. pp. 27·50.

Smith, W. 0. Jr., Nelson, D. M., DiTullio, G. R., and A. R. Leventer. 1996. Temporal and spatial patterns in the Ross Sea: Phytoplankton biomass, elemental composition, productivity and growth rates. J. Geophys. Res. 101(C8):18455·18465.

Smith, R. C., Baker, K. S., and S. E. Stammerjohn. 1998. Exploring sea ice indexes for polar ecosystem studies. Bioscience 48(2):83-93.

Stevens, J. D. 1999. Variable resilience to fishing pressure in two sharks: the significance of different ecological and life history parameters. In Musick, J. A. (ed). Life in the Slow Lane. American Fisheries Symposium 23. Bethesda, Maryland. pp. 11-15.

Takahashi, M. and N. Takahashi. 1984. The food of some Antarctic fish in the Western Ross Sea in Summer 1979. Polar Bioi. 3:237-239. 47

Takeshita, N., Onikura, N., Matsui, S., and S. Kimura. 1997. Embryonic, larval and juvenile development of the roughskin sculpin, Trachidermus fasciatus (Scorpaeniformes: Cottidae). lchthyol. Res. 44(3):257-266.

Vacchi, M., Williams, R., and M. La Mesa. 1996. Reproduction in three species of fish from the Ross Sea and Mawson Sea. Ant. Sci. 8(2):185-192.

White, M. G. and U. Piatkowski. 1993. Abundance, horizontal and vertical distribution of the fish in eastern Weddell Sea micronekton. Polar Bioi. 13:41-53.

Williams, R. 1985a. The potential impact of a krill fishery upon pelagic fish in the Prydz Bay area of Antarctica. Polar Bio. 5:1-4.

Williams, R. 1985b. Trophic relationships between pelagic fish and euphausiids in Antarctic waters. In Siegfried, W. R., Condy, P. R., and R. M. Laws (eds). Antarctic Nutrient Cycles and Food Webs. Springer-Verlag, Berlin and Hiedelberg. pp 452-459.

Wehrmann, A.P. 1998. Aspects of eco-physiological adaptations in Antarctic Fish. In G. di Prisco, Pisano, E., and A. Clarke (eds). Fishes of Antarctica. A Biological Review. Springer-Verlag, Italy. pp 119-128.

Yamada, S. and A. Kawamura. 1986. Some characteristics of the zooplankton distribution in the Prydz Bay region of the Indian sector of the Antarctic Ocean in the summer of 1983/84. Memoirs of the National Institute of Polar Research Special Issue. 44:86-95.

Yefremenko, V. N. 1979. The larvae of six species of the family Nototheniidae from the Scotia Sea. J. lchthyol. 19(6):95-104.

Zar, J. H. (ed). 1984. Biostatistical Analysis. Prentice Hall, Englewood Cliffs, NJ. 718 pp.

Zmijewski, M. I. 1983. Copepoda (Calanoida) from Prydz Bay (Antarctica, Indian Ocean Sector). Polish Polar Research. 4:33-47. TABLES Table 1. Summa!}' of specimens collected per sampling location,date,and technique used Marguerite Bay Elephant Island Source Valerie Loeb Valerie Loeb and Dawn Outram Net Type tv'OCNESS IKMT

Sampling Period Dec-91 Feb-Mar 95 Sampling Depth (m} 0-5 25-157 Number of Specimens 33 17 Developmental Stage Collected Preflexion and Flexion Larvae Postflexion Larvae and Juveniles Size Range (mm} 9-13 14-57

Sampling Period Feb-Mar 96 Sampling Depth (m} <270 Number of Specimens 11 Developmental Stage Collected Postflexion Larvae and Juveniles Size Range (mm} 14-73

(table continues} (\; Weddell Sea Prydz Bay

Source Bruce Robison and Kim Resinbeckner Richard Williams Net Type RMT 1/RMT 8 RMT 1/RMT 8

Sampling Period Oct-92 Feb-Mar 87 Sampling Depth ( m) 1 30-761 Number of Specimens 1 1 25 Developmental Stage Collected Juveniles Adult Size Range (mm) 33-39 67-99

Sampling Period Jan-Feb9 1 Sampling Depth ( m) 34-461 Number of Specimens 50 Developmental Stage Collected Adult Size Range (mm) 62-109

Sampling Period Jan-Feb 9 3 Sampling Depth ( m) 20-600 Number of Specimens 94 Developmental Stage Collected Adult Size Range ( m m) 56-185 (table continues) ~ McMurdo Sound Source John Heine and Daniel Backus Net Type Dipnet

Sampling Period Nov-92 Sampling Depth ( m) 2 Number of Specimens 60 Developmental Stage Collected Postflexion Larvae Size Range (mm) 18-25

Sampling Period Oct-Nov 93 Sampling Depth ( m) 2 Number of Specimens 43 Developmental Stage Collected Postflexion Larvae Size Range ( m m) 18-24 Table 2. Summary results of a t-test to determine a difference in diameter between left versus right sagittal otoliths of P/euragramma antarcticum. Left and Right Otolith Diameter are denoted as DL and DR respectively.

Region Year df DL ().lm) DR ().lm) !-Calculated t -Grit ical p Accept or Reject H0 Prydz Bay 1 991 1 883 830 1.61 12.71 0.35 Accept Prydz Bay 1993 76 1348 1349 -1 .45 1.99 0.54 Accept Marguerite Bay 1991 28 54 53 0.33 2.05 0.75 Accept McMurdo Sound 1992 41 247 249 -0.83 2.02 0.41 Accept McMurdo Sound 1993 30 235 235 0.14 2.04 0.89 Accept Weddell Sea 1992 7 375 373 0.21 2.36 0.84 Accept Elephant Island 1995 1 3 605 612 -1.66 2.16 0.12 Accept Elephant Island 1996 1 0 865 871 -1 .9 2.23 0.09 Accept

"'"" Table 3. 53 Summary calculations of intra-reader precision in age estimates. (Average Percent Error (APE; Beamish and Fournier 1981), Coefficient of Variation (V; Chang 1982) and Index of Precision (0; Chang 1982)). N represents the number of ag_es!samgling_ time. Region Year APE v D N Standard Length Marguerite Bay 1991 5.8 7.5 4.3 21 9-13 mm McMurdo Sound 1992 9.0 12.7 9.0 37 18-25 mm McMurdo Sound 1993 5.6 7.9 5.6 88 19-24 mm Weddell Sea 1992 32.3 18.6 22.9 40 33-39 mm Elephant Island 1995 7.1 9.8 6.4 40 16-56 mm Elephant Island 1996 4.0 5.6 4.0 23 15-73 mm Prydz Bay 1987 3.4 4.8 3.4 1 3 82-96 mm Prydz Bay 1 991 2.9 4.1 2.9 54 65-77 mm Prydz Bay 1993 4.7 6.6 4.7 61 80-154 mm Table 4. Summary of the statistics used to determine between year and between region differences in size and age of Pleuragramma antarcticum during ring (Ring1-Ring 3) formation.

Comparjsion Between years or Regjonaf Type qf Statjstjcs tlsed Ojfference ryes or No) Ring 1 Standard Length-Prydz Bay Between Years ANOVA 1\b Ring 1 Standard Length-Elephant Island Between Years T-Test 1\b Ring 1 Standard Length-McMurdo Sound Between Years T· Test 1\b Ring 1 Age-Prydz Bay Between Years Kruskaii-Wal!is 1\b Ring 1 Age-Elephant Island Between Years T-Test 1\b Ring 1 Age-McMurdo Sound Between Years Mann-Whitney 1\b Ring 1 Standard Length Regional ANOVA No Ring 1 Age Regional ANOVA Yes Ring 2 Standard Length-Prydz Bay Between Years ANOVA 1\b Ring 2 Standard Length-Elephant Island Between Years T-Test 1\b Ring 2 Standard Length-McMurdo Sound Between Years T· Test 1\b Ring 2 Age-Prydz Bay Between Years ANOVA 1\b Ring 2 Age-Elephant Island Between Years T-Test 1\b Ring 2 Age-McMurdo Sound Between Years T-Test 1\b Ring 2 Standard Length Regional ANOVA 1\b Ring 2 Age Regional Kruskai!-Wallis 1\b

(table continues) ':: Comparision Between Years or Regional Type of Statistics Used Difference {Yes or No) Ring 3 Standard Length-Prydz Bay Between Years ANOVA No Ring 3 Standard Length-Elephant Island Between Years Mann-Whitney No Ring 3 Standard Length-McMurdo Sound Between Years T-Test No Ring 3 Age-Prydz Bay Between Years ANOVA No Ring 3 Age-Elephant Island Between Years T-Test No Ring 3 Age-McMurdo Sound Between Years T-Test No Ring 3 Standard Length Regional ANOVA Yes Ring 3 Age Regional ANOVA No

'" Table 5. Summary of environmental parameters within each region of Antarctica used in this study (see Appendix D).

Marguerite Bay Elephant Island Weddell Sea Prydz Bay McMurdo Sound Water Temperature ("C) 0.0-2.0 -0.5 -3.0 -1.8-2.0 -1.9-2.0 -2.2-0.0 Salinity (ppt) 33.9-34.6 33.6-34.8 33.4-34.7 33.2-34.7 33.4-34.8 Oxygen (mill) 6-9 4.7-6.1 Phytoplankton Concentration (mg/m3) 0.33 -25.00 0.2-6.0 .004-1.943 0.5-4.9 Integrated Primary Productivity (mg Cfm2d} 185 311-716 780-2630 Zooplankton Biomass (gDW/m2) 0.7-2.9 3-87 1.5-3.4 Euphausia crystallorophias biomass (gDW/m2) 0.21 Euphausia superba (adults/Juv; #/1 ooorri3) 0-329 5.7-112.5 6.05-27.95 0-20 E. superba (larvae; #/1 ooorri3) 2.7-3690.0 1 3 9.8-97.3 E. crystallorophias (adults/Juv; #/1 ooorri3) 54 0.3-53.3 E. crystallorophias (Larvae; #/1 OOOrri3) 1927 127.8-564.3 Thysanoessa macrura (Adults/Juv; #/1 ooorri3) 51.5-161.3 0.91-8 T. macrura (Larvae; #/1 ooorri3) 15.9-414.4 121.3-471.8 Euphausia frigida (Larvae; #/1 OOOrri3) 10.2-74.3 E. frigida (Adults; #/1 ooorri3) 1.0-25.9 Euphausia tricantha (Larvae; #/1 OOOrri3) 4.7-5.7 E. tricantha (Adults; #/1 OOOrri3) 0.5-1.6 Copepoda (#/1 ooorri3) 41.3-3189.1 16059 1351 .5 Calanoides acutus (#/1 ooorri3) 2065-21250 260-1314 11-225400 13.8-140.8 Ca/anus propinquus (#/1 OOOrri3) 263-676 1-11110 4.8-14.4 Rhinca/anus gigas (#/1 OOOrri3) 37-59 8-50 Metridia gerlachei (#/1 ooorri3) 4052 1-19060 315.2-1606.9 (table continues) '""' Marguerite Bay Elephant Island Weddell Sea Prydz Bay McMurdo Sound Oithona spp (#/1 ooom3) 775-482000 Oncaea spp (#/1 OOOfli3) 837-457000 Bacteria (cells/ml) 1x1 o4 -9.6X1 o5 Limacina helicina (#/1 ooom3) 0.3-33.7 499 33.7-848.2 Clio pyramidata (#/1 OOOfli3) 0.0-5.4 4 Clione limacina (#/1 OOOfli3) 0.1-2.1 1 0 0.9-40.3 Spongiobranchaea australis (#/1 OOOfli3) 0.1-1.8 0.7 Table 6. Standard length (mm) and age (days) during Pleuragramma antarcticum's early development for each sampling time available.

Core Ring 1 Ring2 Ring3 Ref.!ion (Sq !Sll !Af.!e! (SL) !A2el !Sll !Age) McMurdo Sound 1992 9.47 10.63 12.00 13.78 58.50 17.74 121.54 McMurdo Sound 1 993 9.55 10.55 12.55 13.66 58.68 17.81 125.50 Weddell Sea 9.45 10.53 17.00 13.75 75.87 16.55 106.30 Prydz Bay 1987 9.36 10.60 15.50 13.78 65.75 16.84 105.25 PrydzBay 1 9 9 1 9.35 10.60 18.17 13.73 66.00 17.3 119.00 Prydz Bay 1 9 93 9.45 10.65 17.33 13.62 64.80 17.33 116.96 Elephant Island 1995 9.38 10.62 14.64 13.58 65.14 17.2 109.40 Elephant Island 1 9 9 6 9.32 10.46 18.00 13.79 63.20 17.06 106.00

c.n "' Table 7. lnstaneous growth rates (lnSL2-InSLt)I(Age2-Age1) during early development as well as total instaneous growth and absolute growth rates (SL2-SLt)I(Age2-Aget) of Pleuragramma antarcticum for each sampled region (Note: The presence of a dominant ring was used to denote an important early life event. Equations from (Ricker 1979)). Location Birth to Ring 1 Ring 1 to Ring 2 Ring 2 to Ring 3 Birth to Total Absolute Growth McMurdo Sound 0.009 0.005 0.004 0.003 0.049 Weddell Sea 0.006 0.005 0.006 0.004 0.074 Prydz Bay 0.007 0.005 0.005 0.002 0.068 Elephant Island 0.008 0.005 0.005 0.003 0.074 Table 8. Variability in the date of hatch of Pleuragramma antarcticum between years and between regions (Back-calculated hatch dates (date of capture-average age) were used to generate a mean and median date of hatch as well as a mode month of hatch. Two modified Julian calenders (Appendix Aand B) were used to establish the mean and median. The error around the estimate was calculated using average percent error {APE) for each location and mean age of thosefish captured within that area. Location Year of Capture Mean Hatch date Median Hatch Dale M:lde Range Error McMurdo Sound 1992 17-Mar 22-Mar March Jan -April ± 23 days

McMurdo Sound 1993 14-Mar 17-Mar April Dec -April ± 18 days

Weddell Sea 1992 28-Dec 29-Dec Dec Oct -Jan ± 76 days

Marguerite Bay 1991 19-Dec 19-Dec Dec Dec < 1 day

Elephant Island 1995 22-Jul 1 -Jul July May-Oct ± 42 days

Elephant Island 1996 4-Nov 25-Nov Dec Aug-Jan ± 35 days

Prydz Bay 1987 9-Feb 4-Feb Jan,March Nov-May ± 44 days

Prydz Bay 1991 23-Dec 14-Dec Oct Sept-June ± 32 days

Prydz Bay 1993 8-Dec 1-Jan Jan July-Apr ±51 days

Ol 0 RGURES South Pole

"' 63 a) b)

SL=20 mm

c) d)

SL=64 mm SL=94 mm e) f)

g)

Figure 2 a-g. Otoliths of Electron Microscope; a-d represents otolith transformation as the fish ages from a larvae (a) to an adult; (a) also shows the otolith diameter measurement, prominent ring 1 (R1) and prominent ring 3(R3); e-f shows the dominant ring structure seen near the core (C) as well as R1, R3, and prominent ring 2 (R2). The measurement of core diameter can be seen in e; g contains a close up of the microstructure used to determine age. a) Standard length vs Otolith Diameter 200

SL:0.0698(00)+8.9106 .-. R2:0.970 •• E ...... E

J:: C) -c II) ....1 "C... m 80 • "C • c .!!! 60 (/) 40

0 500 1000 1500 2000 2500 3000

Otolith Diameter (um)

Figure 3 a-c. Plot comparing otolith diameter to standard length (a), total length (b) and weight (c) of Pleuragramma antarcticum (Standard length produced the strongest relationship; therefore it was used in all age plots). b) Total Len th vs Otolith Diameter 200

100 TL=O. 0 63 8 ( 00) +2 9. 3 53 R2 = o .8 42 ...... 160 E 140 ...... E .s::..... 12ll Cl c: (I) 100 ..J .. .. ro • Ill .. 0 • 1-- 60

40

2)

0 0 500 1000 1500 Otolith Diamat er (urn) Figure 3 a-c. Continued.

Ol 0'1 c)

Weight vs Otolith Diameter 25000.------~~------, WI=0.0002(0D)2.4133 • R2=0.666 • • 20000

~ Cl E ...... 15000 .r::: -Cl ~ 10000 • • •• 5000 • • • • • • 500 1000 1500 2000 2500 Otolith Diameter (urn) Figure 3 a-c. Continued.

m m 67

s·soc:-ooc: .!!!,.. iii"' c s·ss ~-os ~ <(

::ii 6"61B-OB ~ w (f.) s·sL ~-OL ~ ~ I ,.,- 0 u.., s·ss ~-os ~ -.. Ill !=..c ~"iii s·ss ~-os ~ ...... 1! "' ~ s·sH-ov~ E ,o= E == ~ .5"'o.s 0 s·se~-oe~ E m..C.c ~ j·i 5 "'c .,c .,c Ill Ill '" ,...,.,. oE u·o E E ., '" Q) C.I:I.C. (f.) (f.) (f.) 6"66-06 IDIJ 5·5e-oe

6"6L-OL ...... , 5·5s-os s·ss-os I 6"6!1-ov ~ 6·6e-oe s·sc:-oc:

s·6 ~-o ~

I s·s-o 0 0 0 0 c 0 0 0 ., "' ..,. ~"' "' Ice Indices for the Elephant Island Region 8

~ ..c 7 s:: -0 E I 6 N ~ 5 10 mean=4.66 .....0 -- 4 1il "CI s:: 3

(I) ..2 2

1

0 - 1975 1980 1985 1990 1995 2000

Year

Figure 5. Annual sea ice indices for the Elephant Island region (R. Hewitt, pers. comm.). The solid line represents the mean sea ice value from 1979·1998. Y-error bars indicate standard error. a)

cfl I!!,_ 120 :::1 CJ CJ 0 80 0 £)' 40 c Q) Ill! McMurdo Sound 1993 :::1 0 ., ., ., 1111 McMurdo Sound 1 9 9 2 ~ "' "' "' "' "' "'.... !!iil Prydz Bay 1 993 l ' "'' "' ""' "' ' ~• "'. "'. ~. "' "' .,."' "' "' - ~~, Prydz Bay 1 9 91 "' "' "' "'Q "' "' "' .. ~ ~ .. - "' ~ []Prydz Bay 1987 Standard Length {mm) r.t.Weddell Sea b) Elephant Island 1996 120 cfl §1 Elephant Island 1 99 5 ~ II Marguerite Bay § 80 0

0 - 40 £)' c Q) :::1 n 0 0 0 0 Q 0 0 Q 0 0 0 0 [ 0 0 0 0 0 0 0 Q 0 Q 0 Q 1.1.. '\' Ol ' Q• • "'Q "" "' -0 "' 0 ""0 ' -'; "'• "' '; ": "' . ' 0 0 Q 0 0 -0 0 ' 0 -0 0 "'0 ' "'0 .. .. 0 0 0 0 Q 0 0 0 "' "' 0 .,. ., 0 ... ~ "' ~ "' ~ "' Otolith Diameter- {mm)- "' "' "' m Figure 6 a-b. Size frequency histogram of Pleuragramma antarcticum standard length and otolith diameter lor each sampling period. '"' Correction for Shrinkage due to Preservation 70.------,

SLA=1.096(SLa)+1.642 ..... 60 R2=0.966 • E • E 50 / a; / .. ./ 0 'lii ,/ m 40 ...... • / .s::; / .... / C) c 30 ·"' -· Cll ..J • 'C ·''" ..ca 20 / 'C ~ . c ....ca (/) 10 / / ,.·· .- 0 0 5 10 15 20 25 30 35 40 45 50 Standard Length (After; mm)

Figure 7. Plot comparing pre-preservation standard length to post-preservation standard length of Pleuragramma antarcticum (Samples preserved in ethanol were significantly smaller than fresh specimens). The dashed grey line signifies the null line _., 0 Notochord Development 71 a) Notochord Straight 1

0.9

"tt o.a .!!! .. a; gt 0.7 "'­QJtJ) c. 0.6 a:.. -., c 0.5 :;j .. - E tJl

0

b) Plates Present

0.9 > .0 o.a ]l .. :ii ~ 0.7 ~Ci) .,_0. 0.6 a: "' c 0.5 .!:!.. ..E tJl 0. 0.4 0 0 g! 0.3 c .. oc l 0.2 0.1

0 10· 11· 12· 13· 14- 15- 16- 17- 18- 19- 20· 21- 10.9 11.9 12.9 13.9 14.9 15.9 16.9 17.9 18.9 19.9 20.9 21.9 Standard Length ( m m) Figure 8 a-f. Plots showing the progression of notochord and plate development in P/euragramma antarcticum based on Moser {1996). (Fraction at a given size was determined by taking the number of individuals lor a given stage at size/ total number at that size.) Notochord Development 72 c) Notochord Bent/Plates Not Vertical 1

0.9 ., 0.8 siji OJ0.7"' em"' "' .,_c. 0.6 a: 1:"' 0.5 l!l "' iii a0.4 0 0 ~ 0.3 --r:~ ~ 0.2 1.1.. 0.1

d) Plates VerticaV Not Aligned

0.9 ., 0.8

.l!!; "'C'l0,7 eznUl "' .,_c. 0.6 a: 'E"' 0.5 •!:!"' ..E (/) c. 0.4 0 0 ~ Q,3 I r: .. OCI ·1.1..~ 0.2 0.1

0 +---,.----,- 10· 11· 12· 13· 14· 15· 16· 17· 18· 19· 20· 21· 10.9 11.9 12.9 13.9 14.9 15.9 15.9 17.9 18.9 19.9 20.9 21.9 Standard Length ( m m) Figure B. a·f Continued. Notochord Development 73 e) ned

0.9

, 0.8 !!! ., i ~0.7 :llii) .,_0. 0.6 a: "' 'E., 0.5 .!:!.. E Cl) Q.0.4 0 --0 g! 0.3 ~ ~ 0.2 0 1:! 1.1.. 0.1

0

f) Fin Format ion

0.9 , O.B !!! ., i en 0.7 "'~(i) "' .,_Q. 0.6 a: 'E"' 0.5 .!:!., E"' Cl) Q. 0.4 0 0 ~ 0.3 occ .. ""0 0.2 1:! 1.1.. 0.1

0 10- 11- 12- 13- 14- 15· 16- 17· 18- 19- 20· 21- 10.9 11.9 12.9 13.9 14.9 15.9 16.9 17.9 18.9 19.9 20.9 21.9 Standard Length {mm) Figure 8 a-f. Continued a) Preflexion 74

0.9 .c>- ., 0.8 ~ CD 0.7 Q) "' "'f!cn "' .,_Q. 0.6 a: "' c 0.5 I!! -Q) ·-We.E 0 0.4 oj c Q) 0.3 oc ti 02 .....~ 0.1

0 b) Rexion

0.9 ., 0.8 !! Q) c "' 0.7 Q) .. lllli.i ~ .,_Q. 0.6 a: .. c 0.5 .!::!Q) "'E r.n.,_ 0 0.4 oj Q) 0.3 ~c 0.2 ...~ 0.1

0 10· 11· 12· 13- 14· 15· 16· 17- 18· 19- 20· 21· 10.9 11.9 2.9 13.9 14.9 15.9 16.9 17.9 18.9 19.9 20.9 21.9 Standard Length ( m m) Figure 9 a-d. Plots showing the progression of flexion in Pleuragramma antarcticum based on Moser (1996; Fraction at a given size was determined by taking the number of individuals for a given stage at size/ total number at that size). c) Post flexion 75

,.. 0.9 .c Q.B

"".2! .. 0.7 .,ewc: "'en .,_c. 0.6 a: .. ;: 0.5 ., QJ -~ E Ulc. 0 0.4 -iii 0 > g;c.. ~ u.f! 0.1

0·

d)

0.9

0.8

"".2!<= "en 0.7 QJ .. ~Ci) .,_c. 0.6 a: ...... ;: 0.5 -~ E We. 0 0.4 0~ 0.3 oc<:: "' :g 0.2 f! u. 0.1

0~------10- 11- 12- 13- 14- 15· 16· H· 1 a. 19· 20· 21· 10.9 11.9 2.9 13.9 14.9 15.9 16.9 17.9 18.9 19.9 20.9 21.9 Standard Length (mm) Figure 9 a-d. Continued Weight vs Standard Length 70.------, Wt=2E-07(SL)3. 71 a 5 60 R2=0.935

50

-s 40 .c.... .!.? ~ 30

20

10

0 20 40 60 80 100 120 140 160 180 200 Standard Length (mm) Figure 1 0. Plot comparing weight to standard length in P/euragramma antarcticum (Note: at ca. 90 mm the length to weight relationship changes). a) Standard vs. Otolith Diameter 77 200 SL=0.0698(00)+8.91 06 180 FF=.97o •• 160 -E E 140 ~ J::..... 120 tn c: j 100 "E 80 • "tl"'c: 60 ..... en"' 40 .

20

0 0 500 1000 1500 2000 2500 3000

Otolith Diameter (um)

b) Otolith Diameter vs. Standard Length 3000 OD=13.BB7(SL)·101.11 2500 FF=.97o E -:::. ~ ,_ 2000 ....Ql Ql E 1500 • .!!!c ..c: :1:: 1000 0 • • 5 • •••• 500 •

0~~~~------4 0 20 40 60 80 100 120 140 160 180 200 Standard Length (mm) Figure 11 a-b. Comparison ol otolith diameter and standard length of Pleuragramma ant arcticum. a) McMurdo Sound-logistic 30,------,

25 0 • -E E 20 0 -.t:: 0 0 tn -r::: Q) 1 5 ..J "0 ... McMurdo Sound 1992 ttl "0 10 • r::: 0 McMurdo Sound 1993 ttl -McMurdo Sound Total (J) - (SS92+SS93)=143 5 (SS Combined)=312

0 +-----,-----~--~~--~----~----~----~----~-----r----4 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Age (years} Figure 12 a-c. Between year comparisons of Pleuragramma antarcticum growth using the Logistic function. (Note: No temporal differences in growth rate existed in McMurdo Sound or Elephant Island; however, this is not true for Prydz Bay. Also note, the lowest sum of squares as well as the one used is reported in the legend). b) Pryd.z Bay-Logistic 180.------~

160 0

-140 E §. 120i I

0 0 t "'I • Prydz Bay 1 987 801 <> Prydz Bay 1991 ~ - Prydz Bay {1987 and 1991) ~ 60 !: . 0 Prydz Bay 1993 tU ~,~,·o•~ Prydz Bay 1 9 9 3 en 4o - {SSe rtSSe1+8Sgs)=4636 20 (SS8 rtSS91 )+(SS93)=4934 (SS Combined)=7037 0~----~----~-----~--~==~====~====~ 0 2 4 6 8 10 12 Age (years) Figure 12 a-c. Continued. ...., to c) Elephant Island~ logistic ao "1 70 0 0 -E E 601 -.c sol 0) -c • (1.1 ...1 40~ 0 'tJ.... I m 301 'tJc .. Elephant Island 1 9 9 5 m 201 0 Elephant Island 1 9 9 6 en- - Elephant Island Total (88 +88 )=371 1 o I 95 96 (SS Combined)=505

0 0 0.5 1 1.5 2 2.5 3 3.5 4 Age (years)

Figure 12 a-c. Continued.

OJ 0 6 8 10 12 Age (years) • Marguerite Bay (SSMarJ+{SSwi+(SSE)+(S~+(SSp)=7967 0 Weddell Sea (SSMar+SSw+SSEJ+(SSMc)+(8Sp)=8 124

Figure 1 3. Between region comparisons of P/euragramma antarcticum growth using logistic curves (Note: a differences in growth rate exists between McMurdo Sound and Prydz Bay vs the other regions. Also, the lowest sum of squares as well as the one used is reported in the legend). a) McMurdo Sound-von Bertalanffy

2 0 • -E 0 o

Figure 14 a-c. Between year comparisons of P/euragramma antarcticum growth using the von Bertalanffy Function. (Note: No temporal differences in growth rate existed in McMurdo Sound or Elephant Island; however, this is not true for Prydz Bay. Also note, the lowest sum of squares as well as the one used is reported in the legend). "' b) Prydz Bay-von Bertalanffy 180

160

140 -E E 120 -.r:..... C'l 100 c Prydz Bay 1987 Cl) • Prydz Bay 1991 ..J 80 <> ,,._ - Prydz Bay (1987 and 1991) ,IU 60 0 Prydz Bay 1993 c w~r= Prydz Bay 1 9 9 3 IU 40 (/)- (SS8p-SSg 1+SSg 3)=3277 (SS8y+SS9 1)+(8893)=3503 20 (SS Combined)=4958

0 0 2 4 6 8 10 12 Age (years)

Figure 14 a-c. Continued. c) Elephant Island-von Bert alanffy 90

80

70 -E 0 E 60 -..c: Cl 50 -1: Q) ..J 40 "0... ttl "0 30 1: +Elephant Island 1995 ttl 0 Elephant Island 1 9 9 6 .... 20 en -Elephant Island Total Combined 55=542 10 SS95 +5596=522

0 +----~---~--~-~--~--~---..----~·----! 0 0.5 1 1.5 2 2.5 3 3.5 4 Age (years) Figure 14 a·c. Continued. 85 180

160

140

120

100

80

60

40

20

2 4 6 8 10 12 Age (years) • Marguerite Bay (SSMarl+(SSwl+(SSE)+(SSMc)+(SSp)=5939 <> Weddell Sea (SSMar+SSw+SS£+SSp)+(SSMc)=6162 IJJ Elephant Island (SS Combined)=8757 !Ill McMurdo Sound 0 Prydz Bay - Marguerite, Weddell, Elephant,Prydz

"'"~' McMurdo

Figure 15. Between region comparisons of P/euragramma antarcticum growth using the von Bertalanffy function (Note: a differences in growth rate exists between McMurdo Sound and the other regions. Also, the lowest sum of squares as well as the one used Is reported in the legend). P. ant art icum -von Bert alanffy 180,------,

160 jLinF217.4; K=0.14; and 10 =·0.2871 -E 140 E - 120

20

0+------~------~------.------~------~ 0 2 4 6 8 10 12 Age (Years)

Figure 16, von Bertalanlly growth curve lor Pleuragramma antaraticum. The x·error bars indicate average percent error (APE) for the entire data set.

"' Growth Seasonality: 87

a) McMurdo Sound 1 9 9 2 40

35 ...... E 3o .....E s::. 25. tn -r:: • ••• (1,) 20 •• ...1 ... • • "E m 15 "0 r:: m 1 0 en- 5

0 M A M J J A s 0 N D J F M Month

b) McMurdo Sound 1 9 9 3 40

35 ...... E 3o .....E s::..... 2 5 tn r:: (1,) 20 ...1 "0 ...m 15 "0 r:: m 1 0 en- 5

0 A M J J A S 0 N D J F M A Month Figure 17 a-g. Growth Seasonality during Pleuragramma antarctlcurrls first year of develpment (Note: The x-axis uses month to represent age with the zero point equal to modal hatch month. The oscillating curves were generated for the entire data set, e.g. adulthood, but only early growth was examined here.) 88

D J F M A M J J A S 0 N D Month Figure 1 7 a-g. Continued. Growth Seasonality 89 Prydz Bay 1991 40

35 .-. E 30 E ~ 0 ' .c- 25 / ..... ~ ct:ll Ill 20 ...I "0 ... 15 111 "0 c .....111 1 0 (/)

5

0 ------.------r·· 0 N D J F M A M J J A s 0 Month Prydz Bay 1993 40

35 .-. E 30 E '<~

- 25~ f,> .c..... t:llc Ill 20 ...I ... ~> 'E 15 111 "0 c 111 10 (i)

5

0 J F M A M J J A s 0 N D J Month Figure 17 a-g. Continued. Growth Seasonality_ 90 f) Elephant Island 1995 40 /I 35 /// I 0 //' .-.. __.,,/ I / E 30 / I E ,,/"/ /"/"// --.t: 25 /' / Ol / -c + ~.-~/·· II) 20 ..J . ~··'_,~· • -e 1 5 -·~,.0·.<;.···""· <1l S¥-" ~ "tlc <1l --· . 1 0 ..#'/" tn- 5

0 . J A s 0 N 0 J F M A M J J Month g) Elephant Island 1996 40

35 .-.. E 30. E --J::. 2 5 • Ol -c '· Q) 20 ..J "tl... Ill 1 5 "tlc <1l tn 10

5

0 0 J F M A M J J A s 0 N 0 Month Figure 17 a-g. Continued. APPENDICES Appendix A. Modified Julian Day calender applied to fish whose hatching event started on September 1 of one year to August 31 of the following year Sept I Oct Nov Dec I Jan I Feb I Mar I Aor I Mav June , Julv i Auo 1 --~1--~~3~1--~~6~2~1-~9~2--~__1~2~3~~--1~5~4~4--1~8~2~+-1~2~1~3~+-~2~4~3-4--2~7~4~1-~3~0~4~-t-~3~3~5~ 2 1 32 63 93 124 1ss 183 1 214_+ 244 275 3os 336

--=-3 ____ t-l--'3'-'3'-+--'6'-4'--+--'9'-'4~+-'1-"2""5 __1 _ _:.1:.5"'-6--f--'-1 "'-8_,_4----1!- 21 5--J- _,2'-'4"'5'--+--'2c7c..:;6_ .. _30"'6"-·--1--'3'-'3'-'-7- 4 34 65 95 126 157 185 216 246 277 307 338 5 s5 I 66 96 · 121 158 186 211 247 __ [_ 278 3o8 339 ----'a'--+---"3"'6--+[--"'6"-7--+--"-9 "'7 --+) --'1'-"2~8--+l--'1"'s"'g--+---'1-"8-"7--!---"2'-'-1-'-B--I--'=2"'4-'-8+ 2 7 9 _f---_,3,_,0"'9,___ _ _,3'"4_,.0_ 1 7 37 68 98 l___1g9 160 188 219 249 I 280 I 310 341 ---a~--f--"-3~8--+---'6~9~4[---"9"-9-! 13o--r=J"'6~1--f--,~8~9~t-~2~2~o-4,=~2~5~o~~+~2~8~1--l'r-~3~11~_ 1 _ _,3~4~2- 9 39 70 100 131 ' 162 I' 190 221 251 I 282 ' 312 343 __1,~0'--t-~4~0~--LL----~-~--1~3~2'-+--1~6~3'--+--1~9~1'--+-~2~2~2,__ '·,, j 1_~2~5~2,__+1,~2~8~3--t-_,.3~1"-3-l--"-3"'44~- 11 41 12 102 1s3 1a4 ___,_19"'2,___ 223 253 1 284 t' 314 _ ___,3,_,4_,5 __ I 1 1 12 42 73 103 134 I 165 i 193 224 254 I 285 315_,__,3-:,:4"'6'--- _ 3 8 _ _:..1-"-3-1--- 4'-'3"-·+---'-7.:::,4__ +-_:1,_,0c;:4_ 1 _:_11=5.--f--1'-"-" 6 6._;-1. ___,_1 "-9;:_4 ----1--'2"-'2'-'5'---l--"2-"'5"-5 ---11__,2 6 I 31 6 34 7 14 44 75 105 136 167 195 226 256 287 ' 317 348 1s 45 76--1 1oa 137 168 : 196 221 257 2sa I 318 349 ~-_,_16"---+--4""§- _7_i'__+_J_,0_,_7__ r-,;_1"'3a:c__.,_j.69 J__ 197 ~ 228 258 289 I' 319 350 17 47 78 108 139 I 170 I 198 229 259 I 290 320 351 18 48 79 109 140H__ tu__! 199 230 260 291 I 321 352 ___1!l_+-_4"'e"'--t-·---'a"'o,__+__,_1_.:.1-=-o_ _ _:.1"'4-'-1 ___172 -~ __2oo. 231 261 2e2 s22 353 1 L 2o so a1 111 142 173 · 201 2s2 262 2es L 323 354 21 51 82 112 143 174 i 202 233 263 294.1 324 35_5 --+-8"'3"--+--'1-'-1"'3-f-_,_1_,_4_;.4_, _ _:.,_,_7"'5_ 203 ?~_264 __ 295--+ 325 I 356 1 ___g]L_ , t-~" 84 114 145 176 i 204 235 265 296 1 326 357 24 s4 as 115 146 j. 111 , 2os 236 2ss 297 I s21 I 3sa 25 55 86 116 147 - 178 "'I 206 237 267 298 l 328 I 359 -""'2"'6 -,• sa ----87 117 1 148 I 179 i 201 238 268 299 :m-t 360 27 1. 57 88 118 I 149 - 180 ! 208 239 269 300 L. 330 I 361 2a i 5s 89 11s t5o ~e -l--?4o__ _m_ 301 L23_t_p~ 29 I 59 90 120 'I 151 . 210 241 271 302 I 332 363 -""s"'o'--+----'6'-'o~~--"9'-'1~~~12"'1"-- 1 52 l 211 2 4 2 2 7 2 so 3 j 3 3 s I 3 a 4 I 61 122 I 153 I 212 i I 273 I 334 365 Appendix B. Modified Julian Day calender applied to fish whose hatching event started on May 1 of one year to April 31 of the following year. May I June I July I Aug I Sept I Oct I Nov I Dec I Jan I Feb I Mar I Apr 1 32 62 93 124 154 185 215 246 ' 277 305 336 2 33 63 94 125 I 155 186 216 247 276 306 337 3 34 64 95 126 I 156 187 217 248 279 307 338 4 35 65 96 127 I 157 188 218 249 280 308 339 I 5 36 66 97 126 I 158 I 189 219 250 ' 281 I 309 340 I -· 6 37 67 96 I 129 i 159 I 190 220 251 282 310 341 7 38 I 68 I 99 I 130 I 160 I 191 221 252 283 i 311 342 8 39 69 100 131 I 161 I 192 222 253 284 312 343 9 40 70 I 101 132 162 ! 193 223 254 285 . 313 344 10 41 I 71 I 102 I 133 I 163 I 194 224 255 286 314 345 11 42 I 72 103 I 134 164 i 195 225 256 287 315 346 I I I ' 12 43 73 I 104 I 135 l 165 196 226 257 288 I 316 347 13 44 74 105 136 166 197 227 258 289 317 348 ' I I I 14 45 75 106 137 ! 167 i 198 226 259 290 l 318 349 I 15 46 ' 76 107 I 138 I 168 I 199 229 260 ' 291 I 319 350 16 47 I 77 108 139 169 I 200 230 261 292 320 351 17 48 78 109 140 170 I 201 231 262 293 I 321 352 18 49 79 110 141 171 I 202 232 263 294 322 353 I l 19 50 I 80 1 1 1 + 142 172 I 203 233 264 295 323 354 20 51 I 81 112 143 173 ! 204 234 265 296 i' 324 355 21 52 82 113 144 174 I 205 235 266 297 325 356 I ' I ' I 22 ! 53 83 I 114 I 145 175 206 236 267 298 I 326 I 357 23 54 84 1 15 ( 146 176 I 207 237 268 299 I 327 I 358 24 55 85 116 ! 147 177 I 208 238 269 300 I 328 359 I I ' 25 56 86 117 I 148 178 I 209 239 270 301 ' 329 360 26 57 87 118 ! 149 179 I 210 240 271 302 i 330 I 361 27 58 88 119 ! 150 180 211 I 241 272 303 i' 331 36? 28 59 89 120 ! 151 181 I 212 242 273 304 ' 332 I 363 29 ' 60 90 I 121 i 152 182 I 213 ' 243 274 I 333 364 30 rat 91 122 153 183 I 214 244 275 i 334 I 365 I I I 31 I 92 123 I 184 I 245 276 335 I Appendix C. Summary of growth curves for Pleuragramma antarcticum and ihair subsequent parameters for each sampling time (The smallest sum of squares (Bold) was considered !he best rlt).

I'

von Bartalanffy (Oscillate) 14.2 ~inf=245 1<=.199 To=-.21 0 C=-.266 Ts=.042 Linear 4109.6 Slape=.367 Y-int=6.99 Gompertz 14.2 Wo=9.372 G=.716 g=1 0.0 Logistic 14.2 r=50.0 1<=12.78 Yo=S.02

Weddell 1992 van Bartalanffy 112.0 Llnl=58 K=.785 To=-.208 van Benatanffy (Oscillate) 103.0 Llnf=215 K=.135 To=.394 C=-.427 Ts=.328 Linear 153.3 Slope=.074 Y·int=1 0.32 Gompertz 102.8 Wo=9.024 G=1.522 9=2.274 Logistic 99.5 r=3.S 1<=37.27 Yo=9.29

McMurdo 1992 von Bertalanffy 49.6 Linf=24 1<=2.45 Tom-.21 0 von Bartalanffy ( 0 scilla! e) 48.4 Linf=181 1<=.099 To=-.599 Cm•.503 Ts=.082 Linear 181.6 Slope=.044 Y-int=1 0.54 GJmpertz 49.6 Wa=9.652 Go.856 9=3.603 Logistic 50.7 r=4.8 1<=22.1 Yo=9.72

McMurdo 1993 von Bertalanffy 99.0 Llnf=23 Km3,01 To=-.173 von Bertafanffy (Oscillate) 92.6 Linf=178 1<=.085 To=-.798 c=-.973 Ts=.173 Linear 234.8 Slope=.045 Y·int=1 0.83 Gompertz 95.0 Wa=9.44 (3..857 9=4.213 Logistic 92.6 r::::5.5 1<=21.8 Yo=9.532

Prydz Bay 1987 von Bertalanffy 509.0 Linf=98 K=.587 To=-.087 von Bertalanffy (Oscillate) 343.1 Linf=742 K=.033 To=-.1 08 C=~3.785 Ts=O Linear 875.1 Slope=.058 Y-int=11.32 Gompertz 327.7 Wo=7.164 Go2.512 g=1.428 Logist lc: 274.8 r=2.4 1<=87.06 Yo=8.918 ..."' Appendix C. Continued.

Region Year CUrve Sums of Squares Ke~ Parameters Prydz Bay 1991 von Bertalanffy 795.4 Linl=159 K=.195 To=-.281 von Bertalanffy (Oscillate) 1862.9 Llnf=126 K=.289 To=-.119 C=·1 TS=-.08 Linear 988.1 Slope=.062 Y-int=9 .99 Gompertz 665.1 Wa=10.05 6=2.25 g=.753 Logistic 594.7 r=1.3 K=84.74 Yo=10.91

Prydz Bay 1993 von Be rtalanfty 1973.0 Llnf=163 K=.244 To=-.205 von Bertalanfly (Oscillate) 1862.9 Linf=159 K=.258 To=·.161 0=.432 Ts=-.76 linear 7414.0 Slope=.058 Y-lnt=14.05 !?ompertz 2760.3 Wo=11.34 6=2.444 g=.631 Logistic 3766.8 r=1.2 K=112.8 Yo=12.33

Elephant rsland 1995 von Bertalanffy 111.4 Linf=211 K=.154 Ta=-.272 von Bartalanlly (Oscillate) 102.4 Llnf=212 K=.159 To=-.236 C=-.235 Ts=-.1 8 linear 120.6 Slope=.075 Y·int=9.34 Gompertz 86.5 Wa=9.252 G=2.007 9=1.277 Logistic 82.6 r=2.4 K=58.96 Yo=9.873

Elephant Island 1996 von Bertalanlfy 410.8 Unf=1 01 K=.426 To=-.185 von Bertalanfty (Oscillate) 370.4 Llnf=BB K=.58 To=-.1 04 C=·.419 Ts=.23 Linear 4266.8 Slope=.065 Y-int=1 0.75 Gompertz 304.1 Wo=9.186 G=2.1i3 g=1.232 Logistic 288.5 r=2.1 K=71.06 Yo=1 0.31 Appendix D. Reported environmental values lor all regions examined. Bold numbers indicate 96 the reference lor a given value. Some values were standardized for conformity with other table values EnvlronmtH'lta! f'arame,IH Mamuarite lla' Elenhant Island Watef Temeerature {}J"C i0·700[!)·1ll03 " ·1 to 3"C {0·750mH995 ' ·-£.::9_\M!J!. Surla~----· •1.5 \tt 3"(: (0·750m}·l996 '

-

"

------·

' 5 Sail 34 3 ;at 50 m);-19!12 ' 3''.6 1n 34.8 0·7$0n!J.:.ll!.!![i_'-·--- " {0-70Qm!-t963 14 33,7 iu 34.7 fi}-1SOm ·1996 ' "'" lo_JMJF . . +-·

---·

~eo 7.5~9.0 mll! !1 Omj-1995 ' 6·8.0 mill JQmi-1>196 , 1 1 Pnytoelankttm Coneentr<~tkm 25 mG Chi a/m3 !•hal(. !lurfaca}.Jan 19137 " <1.5 to 6 Cilia molrr.J fSml-1995 ' ,_ 1 __ 11...!.U!LChJ a!m3 llntgg~Q·SOml·Om;; 1986 • .:0.3-~.1 Chi a mqlm3 (Q:1Q_Oml·HI95 " 4 l.1 m! Cl:llalm:llin!emated O·SOml-Jan 19!:17 1 0.4 In 5 Ch111. .!!illill!1U.§!!!1:..19U6 lt 6.5 mg Q!J! aim;! !SUrf§Cil mg{!n)-19~6 " s.,.?-2.1 [email protected]:J.QQ!nl:~ 4.6 Crl atm3 su!taca maanl-1987 " 1.4 nm Chl Wm3 (surlaca mean)-19§17 " 1.2 mq Chi t~fm~!!£!Lln!'li:Wl·1iill.L..~-·--- ~ lt33·0.496 rna Chi ~1J.!§.;L-"_,

1 Integrated Primal)' Product!Y!lY_ 1.85 g Cim2qJ!!:ill.Jti!!!...§IU;U)·1.967 • 377-5:19 ~.:i..J..!f::JOOml-1990 " 31:Hi52 m-:.~Cim2d /0-toO:m\•199_1-'-'- 315-434 moCJm2d (.[-100m)·1992 " 311·716 tooC/m2d fD·IOD.i!!l:.li~~ " ~--· ,!Q.QP.lnnktcn 51~ 0.7 cDW/m2 j0·100Cm· .::1mm)·J983 " 2.9 r.DW/m2 IO•tOOOm• 1-15mm)-!U63 " E. C~t~/lotDef1ias blomruJs. ,. Euf!hausla ~rbn ~adult !If Juvj 0.8-3 !mmltOOOm:l {0-45rn· dnyH!lll7 • 5. 7 ·14.5/1 OOOm:!-1996 ,. -· 5-329 lmmfHJO!lm3 !0-45m' n!gl!tl·1987 • 1Q.,_4·27 -l£!iliLOm:H994 ,. 1m...!!!L!.Q.QJl!!!lli.Q·20tlm· d\!¥.1:.11107 !!§.:14.1/1000m3·1993 - ~· ~- 3·45 immltQOllil13!(HWOm;_ nlqhU·1907 • 106.7·112.5/1000m~·liJ96 " ·63 c:dtll sl1000m3 IG-45!l:Lll!t ht ·Hl67 •

0·6 udultslt Q-:JOm3(0-200m; !layJ~1987 . 6 fh>l·OO od;;li§!!OOOm3{{}-~~thl9!!7

E!fE!!nuskt SUE!;!!_rlm (larvae) 135.B·O§fl0!1000tn3· 199.5 " 2.7·13.91 1 oooro:H 996 "

Euph;wsla cry$tolloraphfas (adults./ Juv) Appendix D Continued 97 Environmental Param~ter Milr uorlla "' Efe hant &!l;md -~~E!!!!.~ulforcehiils_ !l..nrvae) '" Th~D:ffCes$3 "'"""'' {Adulls/Juvl \HI 4·16i.311000m3·1995 " 79. 7·118.9/1 000m3-1Q94 " - 51AH41 5/1000m3·HH!3 " 10

I!!Y.!anr:uJssa ~;l 15.>H!76.911000m3-1995 "'~""' " :WB.5-414.411000rtl3· 1998 " ------· .. .§!Ehausla ttfJJ.Idn ila!VM2

E!!£hai!SI4 frl!]_lda {Mulls) 9.8•16. 711 OOOm3-1995 " [JJ!::.g§,0/1 ooom3-tlt94 " 1-3.611000m:l-t!l:93 " 1.9-9!1 OOOm3-199G " Ev£hal1$/8 rrl~Umtha .. {l..nrvne} - EIJI)hm.Jsfa trlcanlha (Adulls) 1.5-1.61100Qm3·199S " - t-1.2/1000m3-1994 " l.0/1000mJ-1993 " 0.5~1l.Of1000m3-1996 " ~ode 6!'!2.7·51B!l.11000m:H995 " 41.3·30!HL2/1 000m3·1994 " ;}tl. H10!Hlm:J•1993 " 794 A·1MlL.10QQm3-199§ " Calancides acutus 20G5fHl00m:l \in 200 m}.Dec 1996 H 2f250!1oooma nn 200 ml·Jp.!!...l.Q~~- --!!ll!.fi.Q/1000m3 {l11 :too mj·feb Hl87 14 :rnJ!illOOOm3 \i!] l!OO m}·M@f t 907 " -

~C./anus eroefn~

------·----· - rtmrcc.ti#Ws gigas

------·

Metridlii garlachel Appendix D. Continued. 98

EnvJronmental Parametor Maroucdte aa, El111.1har~t Island Olfhona 'Ell

Onc.Jef!l Sf!P. ·--

Bacteria

Umoclrm hc/lcimr 1,9!JI)OQmJ·1Jl!!5 .. 0,3HOOOm3-1994 ~------~-· " - 1 ,9·33, 111 OOOm;.l-1996 " -

--- r--- ,. ~amidst a 0-5.J!1001Jm3•1995 0 ,jf-5.4{1 OOi!.l'J!U994 .. 0·0.2/1000m3-1993 " 0-0, 111!>0Um3·190-S " Cli/Jne limacflla . q_,511000m3·1995 ~g --- 0.311000m3·1994 " o, 1f100fim3-199;1 " ----· .2·lU/1000m3-199fi "

]!epngic!:mJnchiUia suslralls ·-c--·--· 0.4·0.5/1 OOOm3·1995 .. 0,1/1000m3-199~ " 0.3AlJi11900m3·1 99JL...!~ t A-1 .a/1 ooom:H996 " Appendix D. Continued. 99 Environmental Parameter Weddell '" p dz "" Water Tcm ra1ure -\t5"C h>urlaee\•1996 ,. -1.9 lo 1.3"Q (0-200 m ln!eg;atnd)·i9S3 . ·0.5 lo ·1JJ"C (0..150m}-!9!:16 " -Ui to 2.0'0 -1995 ~' 0.7S"C lsurfacel-1978 u -1.5 !o -t.O"C.,.JQyar sheltj-HIIJ5 " :l,!L.!Q.~JQ:§..QOtnl-1926 " .g,o·c imlmlmumH001 .. ·2 to 0.5"Cj(H000ITIH'il00 • -1.7 to ·0.2"C {0·100pml-1986 ..

-1.2s~c (sllrlno!1i.....2t!._a!!..JY.u!er!-1992 " ~~~--~·-----·--~- ·1.25 10 ·Q.3'C !Q:900m· fl.!'!!2!L.Walerl·1992 .. -1.75"C l!!!l.ill!~nder lcaH992 '" ·1.75 lo O"C i0·90Qm· undar lcel-1SG2 .. Salinity 33.6 isurfaeal-1986 u 33.2! lo 34.33 i0-200 m lntegrated!-1993 • ,:J:l,B to 34J3 0-tsnm-1~ ~1.5 to 34.5· HHIS u ·-~- :!4.4 {suf.!aoel-1978 n 34.5-34.7 mnrlmum}-1982 " 33.40 to 34.7 [0-tOOO m}-1963 ~

3.1.6 !0 34,6 0-1000 m -1986 :~~ 3•1.4 lsuri:!l£l'!4..!ill~l1!P.1!'Hl·1992 H ·-- 34.4 !o 34.6 l0·90Cm' watef ·1992 -~ " 34 a lsurface· tmder !ceH 992 u !o :!4.6 IO,.I'IOO:w unOOt !c ·19!12 ,.

.Q!m_fl(! "'·'

P'tlytoJlli!.!:!!lton Ctmcenuatlon OJI04 lo 1.943 mg chi n/mS (0·290 m 1nteqra!ed)·19!13 • 9.46 mg ct11 nlm3 {maximum)-1985 3 ~

<0.3 mg C!JJ ai!!P {0~21Hlm)·1l!'85

<:tL5 mg Chi !lfm3~jSS4

Integrated Primary Produe:Hv!Jy <-

~o£!!ankton BiOti»J.'lll ?·B1 gDWim2 ... (0-300ml~19fl3 '

~ e:r,staNcrttf!.hltiS blonm;s El.loha!J$Ja 1!11£1Srbs laduUsiJw :n.9511000m3 I0-20Um ·1086 " 0·20!1 000m3 " &,.QSt1000m3 {0·1000m/·1986 " 23fl000~Qm.i.::..l!LB3 • 15.55!1 oooma l0·29Jill!l::i.lillB " 4.341m2 .. {0·200fi1_H9B3 .. "------~-<

<---~---

~&Jp St

E!.Jphausis crystaJiorcpt;las (aduiUJ Juv} 54/HJOOrn3 {O·:lOOm)·HHIJ . Appendix D. Continued. 100

Envlrcnmcntal Parnmetor Weddell .,, "' ·~ Eue_fll!usla CIJ:~Sia/farochfas tlurvael 1927i1000m3 0·300m ·1983 • 5E4.3t1000m3 i:0-200mJ· 1955 " -- 127.8/lOOOmJJ (Q-1 000!!ll:1985 .. ~tw'CSS.ll m~• jAdultsfJ"!!i- 6/IO.(i0rn3 (0·30llm}·l9!.1;} ' 2.

Thynnoossa mac:rura jlarvae) 183/1000m3 o-aoom\·1 !Hl3 ' 47UUI000m3 f0·200m -19115 .. 121.3/IO~iOQOm)·HHIS "

Euf!hausla frJilda !larvae) 74.3/tOOOrn3 i0·200m)·19S5 " 1il,2J1QOOm3 j0·1000m}-19135 " Ef!Ehauskf Welda

--

Euehausin trir;anthn (L.ruvall! 5.7/IOQOm)l {0·200ml:.ll!§5 .. 4.7/1000m.1 IO·Hl09.!!!1.:1985 " Euptmus!s Ufeanlhs {Adults)

J#~f!OdO 1i1059iHl00-'!'13 fO·SOOml-1903 ' 1351 511Q.Q.QmL.J.Q·2fiOm)·1903 '

--·-----·--- ~~------~---~--~--~--· '--·--·-· -

Cslaooldcs liCUIU:S 1314/1000m3 ~.QQ.m}-1983 • B7·1 pes , ' ~ proplnqnus 576/IOOomJ 0-JOOmi·iUBJ ' 127/HIOOmJ f0·200m ·1993 263!Hl00m3 t0·200mH907 _;, 8!1000m3 f0-200m}·1997 " 3711000m:l j0-200m)-19~4 " lwoooma {l'h2QOm!-1989 " 1QQ0/1000m3 f0·100!!ll:.198B " - 111IOI1000m3 0·220mi·Hf03 " O!l01t000m3 i0-10GOmj-t90H ' f!!!EE!L~UJE!_9!Jl_n~~----· 59/IOOOmJ O

·--·- ··------.. Cllo _ py)'im'f!data /1000m3 0·300m\-1983 •

CHrme Hmtu:lna 10f1000m:l (0·300m~.'--·

.. ·--·

Spangfobrarn:haea 8U5ftl'l.liS 0.7/1000m3 (O·:JOO~l-1 983 • Appendix D. Continued. 102 Enlllrurtmental Pnrame!er McMurdo _ytater TemQnrajurt~ surtm::ej-1983-· " -1Jl"" !a ·LR"C !'Ifill m}-19[;'! " ·UJ'i"C l!lOOml • c:l'C {3-275ml . 2.16 lo ·t.8€'C u ·1.!)6 In -1.91 i0·87ml "

Salinity 3.4.39-34.83 "

~-·---·--·- ·------

""" " 5·5.05 mill 10-67ml n 4.65:4.8 mill l0:·67m} " f'h'I/U.lQl!£!klon Concentration 11·4.9 mg[m3 !syrfaca}-1990 " n.s-O.B2 mglm3-19!Hl " ,. ______

---·----·------f-.-·

f---.. Integral elf PTim.!!!.Y ProtluetMI~ 780-2630 mg Clm:ld-1990 "

~lankton Biomass. 1.§-3A gDWim2-19U3 "

E. (;rysrollorophiall biamnss 1121 0Wlm2 I0-800mi~19S3 " .. ~usls superbs {tulultsiJ~

--·----·------··- Eve_hau.Jkl supcttm (In~

Euphausia cr;:stal!oroehilfs { ndultsl Juv) 0,511000m3 (0-100m)-1981 • ~J.. ~1000mLJP·300.ml:.lru!L..* __ 0.3!1000m3 t0-100m•·19B5 ~ t L5/1000m3 (0·3Jom)-19B5 • Appendix D Continued 103 Envlrcnmontal Parameter McMurdo Etlptuwsfa oystJJJ/orcphlss {Larvae~ ·- -·------· TIJt:sanoossa mncrun: {Adu!ls/Juv)_

- --- ~llOI!.!IB.I.l macntta (Larvaej

El/tJhausia frfalda ft. .prvael

Eupfllro!!ila frfgJdlf !Adu!tsi ---

"''"'hausla trkantha Lnrvaal

~aus!a trlcRntha !Ad~ ·-

~da -

Cal:mrtides ncutus 13.tl/1000m:i to· 1OOm I ::!.!m_7 _•_ 123.911GOOm3 l.O·;:?OOm)-1!.!:07 •

Gnfil!IIJS proplnquus •UI!OOOm3 (1-iOOm -HHI7 • 7 31100!lm3 j0-3Q\!m}-19B7 • 11.5/10Qllm3 10-100m}·HlSS • 14.4il0!}0m3 10·3:J0m ·19B5 •

Rtinestanus gigas -- ---·----f-. ------

0 Metrldfa gerfach!!i 713.3!1 000mL.ill:.l.QOml·19S7__ 1606.9!1000m3 !0·30JlmH91l~ ~QOOm:J 10-to!lml-1~ 1465.7/101JOID3 {0-33t'lm)-1935 • Appendix D Continued 104 Environmental Parameter McMurdo So"" Oithooo "" ~ -

O~caspp-

--~-~-~-----·

Bncterl!t a.s o 9.6 'Xl{)l =!!simi " 1 10 10 X10• ce!lslml (tlndar lc!U.,._~

!:!!!!.~ttfh:lrtll 414.3/1900m3 \O•!Q.Om)-!907 • - S4H.:U1000m3 I0-300f!!l::!.g.!l..L!_ SL'ilftQOOrn3 (0-IC{)m]-1985 • 33.7/1000m3 f0-330m)-1 995 • -- +---· Clio pytamldata

- ----~-

Cflaf!e llmocintl 1.4/100Q!!l.LJ0·10~.l:J991 • 0.9/lOOpm:; {G

Spr:mgiobranchalllllt australis

Amn~. ct ul., 1!195 1 Hcmky and Escritor, 1991 24 Amns, cl al.. 1996 2 Huullty.etlll. l991lS

Beaumnnt nn<.l Hosie. 1997 J Kaufmann, !Oil!L, 1995 26

Buys~n-Ermcu lUll! f'ia!knws!J, 1988 4 Knr>~. I !194 27 D11ysen, ct ul., 11)91 5 Kottmcier. t:t 111., 1\!872!1 Oriuhlr., 1!191 6 Ltncmft, Cl ul., 19&9 29 Budnichcnckoanr.! Khromov, 19&R 7 Locb,ctuL, 199530 Eai\lmnn. 19&5 B Luch. clal.. lY% 31 Fllstcr, !969 9 Miquc!, 199132 Fubrna."' amJ Amm, 19!!0. Ill N1.me.1 V;u. anti Lennon, 1996 J3

Hch!io~. c:! nL, !9951[ SmiUl. tt al, 1996 3.1 Uehling, ct a!., 199(> l2 'l'ammb.nnd Kawamut:l, \936 JS

Hohn-H:mscn, e! at, 1995 U Zlnijcw~ki, l9!!3 :36 Holm-Hansen and Milch ell. 199 l 14 Ho}l\cin;, J!JS5IS HopkiM, 1987 Hi

Hnpl::ln~ a.1d Torres, l93S 17 Hopkirls .attd TOI'r\!$, 19R9 18 Hosie, 199119

1-f~Y;ic ami Co.::mm. 1994 26

Ba;ie :mtl Stillp, 1989 21 Ho;;ic. et al, l'l97 22

Buhold unil HemjlCl, 19117 :ZJ