CHAPTER 32

The Coastal Fish Fauna of Terra Nova Bay, Ross Sea, Antarctica

M. Vacchi', M. La Mesa', and S. Greco2

ABSTRACT The coastal fish community ofTerra Nova Bay (Ross Sea) was studied from samples collected off the Italian Antarctic station Terra Nova Bay down to about 700 m depth from 1987 to 1995. Species composition, abundance and vertical distribution are reported and the biological characteristics such as feeding habits, reproduction, age and growth of the common species have been studied. Twenty-six fish species were recorded, the most common being the nototheniid Trematomus bernacchii and the channichthyid Chionodraco hamatus. As for the vertical distribution of fish, species diversity was higher in shallow than in deep waters. The fish community comprises species which exhibit three different trophic niches: T. bernacchii and Trematomus pennellii are mostly benthos feeders, Trematomus hansoni and Trematomus /oennbergi are mostly piscivorous and Trematomus newnesi feeds preferentially on plankton. Differences in reproductive strategies have been found during the sampling period, i.e. January and February, when C. hamatus and T. hansoni were in a spawning condition, whereas T. bernacchii was in a resting-early development stage. The two most common species, T. bernacchii and C. hamatus, show a high longevity, living more than 20 and 10 years, respectively. Moreover, in both species the females attain slightly older age and grow faster than males.

Introduction

The first samples of the fish fauna of the Ross Sea were collected during the 1839-1843 British expedition led by James Clark Ross (Richardson 1844-1848). The next substantial contributions to the knowledge of the fish community of this Antarctic sector were due to the British Antarctic expedition Terra Nova at the beginning of this century (Regan 1914). After a gap of more than 40 years, ichthyological studies in the Ross Sea started again mostly by shore-based research con­ducted at McMurdo Sound by American and New Zealand scientists. These studies concerned sys­tematics, zoogeography, biology and physiology (Wohlschlag 1960, 1964; Dearborn 1965; DeWitt 1971; DeVries and Eastman 1981; Eastman and DeVries 1982; Montgomery and Macdonald 1987; Macdonald et al. 1988).

Other ichthyological investigations were car­ried out during Antarctic cruises in the 1960s and

1970s. Among them, relevant data on the fish fauna of the Ross Sea were collected during the NZ oceanographic survey on HMNZS Endeavour (Reseck 1961), the USA Eltanin oceanographic cruise (DeWitt 1970), and the Japanese explora­tory fish survey on board the Daini Bashu-Maru (Iwami and Abe 1981).

In recent years, Italian scientists have per­formed several research programmes on coastal fish of the Ross Sea as a contribution to the Italian Programme for Antarctic Research (PNRA). Most studies were carried out at Terra Nova Bay (western sector of the Ross Sea, Victoria Land Coast), where the Italian Antarctic station Terra Nova Bay was built in 1986-87. Ichthyological investigations at Terra Nova Bay included bio­chemical and physiological approaches (di Prisco et al. 1991; Tota et al. 1991), ecotoxicology studies (Focardi et al. 1992), as well as studies on phylo­genetic and evolutionary relations (Morescalchi et al. 1992; Bargelloni et al. 1994). Ecological and

lICRAM-Istituto Centrale per la Ricerca scientifica e tecnologica Applicata al Mare, Via Lorenzo Respighi 5, 00197, Rome, Italy 'CNR-Istituto Talassografico Sperimentale, Spianata San Raineri 86, 98122 Messina, Italy

F. M. Faranda et al. (eds.), Ross Sea Ecology© Springer-Verlag Berlin Heidelberg 2000

458 M. Vacchi et al.

faunistic studies of the coastal fish fauna of Terra Nova Bay were the main aims of the Nekton team, who started ichthyological surveys as of the third Italian Antarctic expedition in 1987-88 (Vacchi et al. 1992). The research was particularly con­cerned with improving the knowledge of biologi­cal and ecological characteristics of the most abundant species, such as feeding habits (Vacchi et al. 1994; Vacchi and La Mesa 1995; La Mesa et al. 1997), reproduction (Vacchi et al. 1996) and age and growth (Vacchi et al.1992; La Mesa et al.1996). The present chapter provides additional informa­tion on the coastal fish fauna of the 3rd, 6th and lOth Italian Antarctic expeditions.

Materials and Methods

The research on coastal fishes was conducted near the Italian station Terra Nova Bay (74°41'42"S and 64°07'25"E), from the Gerlache Inlet to Cape Russell, in the north-western Ross Sea (Fig. 1) during three Italian Antarctic expeditions. The sampling area is characterized by shallow hard bottoms down to the 20 m depth, where two macroalgal species (Iridaea cordata and Phyl­lophora antarctica) and a few animal taxa (mainly

polychaetes, molluscs and peracarid crustaceans) dominate the benthic association (Gambi et al. 1994). In the soft bottom, that appears at about the 20-m depth and extends down to the 600-m depth, the benthic community is represented by facies of Adamussium colbecki and by sponges, cnidarians, bryozoans and polychaetes (Di Geronimo et al. 1992).

Fish samples were collected by trammel and gill nets, both with 32-mm mesh size (side), and longlines and traps. Fishing activities were mainly carried out during the day for an average of 4-5 h. The samplings in the Polar Queen expedition were made from 13 January to 13 February 1988, from a 6-m-long aluminium boat, and consisted of 61 hauls made from 16- to 300-m depth (Vacchi et al. 1992).

During the Cariboo expedition, a total number of 90 fishing operations were conducted from 19 December 1990 to 9 February 1991 (Vacchi et al. 1991); the availability of a larger boat equipped with a hydraulic winch allowed us to extend the depth range sampled. The hauls were taken along four transects perpendicular to the coastline and extended offshore, ranging between 16 and 682-m depths (Fig.l). On December 16, 1994, we collected

Fig.!. The study area of Terra Nova Bay showing the sampling stations during the 1987/88 expedition (el and 1990/91 expe­dition (grid stripes l

one sample of fish by gill net at the IsO-m depth, during a short pause of the Italian oceanographic cruise ROSSMIZE near the Station.

All fishes were identified after Fischer and Hureau (1985) and Gon and Heemstra (1990). The specimens of the most common species were mea­sured as total length (TL) to the nearest mm below. Total weight was determined to the nearest gram below. Each specimen was gutted and its gonads weighed and staged according to a five-point scale (Everson 1977; Anonymous 1989). With the aim to detect growth rates and spatial migrations of the most abundant species, 477 specimens of Tremato­mus bernacchii, caught mostly by hooks during the 1990-91 expedition, were tagged and released near the station.

The feeding habits of some abundant species, such as the nototheniids T. bernacchii, T. hansoni, T. newnesi, T. loennbergii and T. pennellii were determined by stomach content analysis (Vacchi

Table I. Fish species found in Terra Nova Bay

The Coastal Fish Fauna of Terra Nova Bay, Ross Sea, Antarctica 459

et al. 1994; La Mesa et al. 1997). Some reproductive characteristics such as gonado-somatic index (GSI), fecundity and egg size were studied in T. bernacchii, T. hansoni and Chionodraco hamatus (Vacchi et al. 1996). Studies on age and growth, by means of otolith (sagittae) reading, were per­formed on T. bernacchii and C. hamatus (Vacchi et al. 1992; La Mesa et al. 1996).

Results

Species Composition and Vertical Distribution

The fishing activities of the Nekton team provided 19 species (11 genera) belonging to 4 families. In addition, one whole specimen of Paraliparis sp. was found in the stomach of the largest Dissos­tichus mawsoni specimen caught (Table 1). The following species collected from other colleagues are also reported in Table 1:

Family Species No. of specimens Size range (TL in mm) Our samples Other investigators

Nototheniidae Dissostichus mawsoni Norman Notothenia coriiceps Richardson Pleuragramma antarcticum Boulenger Trematomus bernacchii Boulenger Trematomus eulepidotus Regan Trematomus hansoni Boulenger Trematomus lepidorhinus Pappenheim Trematomus loennbergii Regan Trematomus newnesi Boulenger Trematomus nicolai (Boulenger) Trematomus pennellii Regan Trematomus scotti (Boulenger) Pagothenia borchgrevinki (Boulenger)

Bathydraconidae Cygnodraco mawsoni Waite Gymnodraco acuticeps Boulenger Prionodraco evansii Regan

Channichthyidae Chaenodraco wilsoni Regan Chionodraco hamatus (Lonnberg) Chionodraco myersi DeWitt and Tyler Cryodraco sp. Dollo Neopagetopsis ionah Nybelin Page tops is macropterus Boulenger

Artedidraconidae Artedidraco loennbergi Roule Histiodraco velifer Regan Pogonophryne scotti Regan

Liparididae Paraliparis sp.

'Not reported. b Specimen damaged.

1 6

2107 23

169

94 198

5 195

-20

15 14

435 6

13

16

1 2

1200-1670 ,.} ,.l

141-345 155-320 210-420 ,.} 105-330 210-249 185-263 165-255 120 ,.}

421-554 366-423 138

280 180-440 297-336 392-510

230-304

169 274-280

+

+ + +

+ + + + +

+ + +

+ + + +

+

+ +

+

+ +

+

+

+

+

460 M. Vacchi et al.

- One specimen of Artedidraco loennbergi found in the sediment of a bucket set at the 283-m depth, during the activities of benthic ecologists near the station in 1988.

- An adult Notothenia coriiceps caught in January 1991 by a small trammel net at the 80-90-m depth (Focardi, pers. comm.).

- One specimen of both Neopagetopsis ionah and Trematomus lepidorhinus collected by gill net during the 1995-96 expedition at the 200- and 150-m depths, respectively (Ungaro and Varotto 1997).

- Several specimens of Pagothenia borchgrevinki fished from holes or natural cracks in the fast ice by hand line during the 1994-95 and 1995-96 expeditions (Ungaro and Varotto 1997; di Prisco, pers. comm.).

- A few adult and subadult specimens of Pleura­gramma antarcticum caught by trammel-net during the 1992-93 expedition (Nascetti, pers. comm.).

Nototheniidae were the most numerous family, with 12 species, followed by Channichthyidae, with 6 species. Nototheniidae were also dominant in number, with 85.4% of total catches and Tremato­mus bernacchii as the dominant species (Table 1).

The three specimens of the giant nototheniid Dis­sostichus mawsoni (up to 60kg in weight) were caught only during the first half of the sampling period of the 199011991 expedition (from late December to mid-January) in the 530-655-m depth range (Vacchi and Greco 1994). Among channichthyids, C. hamatus was the most common species, whereas the most abundant bathydraconid was Cygnodraco mawsoni. Arte­didraconidae were represented by one specimen of Histiodraco velifer and two of Pogonophryne scotti. The bulk of catches consisted mainly of adult individuals, as shown in Table 1. T. bernacchii, C. hamatus, T. hansoni and T. penne/lii were very common in the area, each species occurring in more than 25% of samples collected by nets. T. newnesi, T. loennbergii, C. mawsoni, Pagetopsis macropterus, Cryodraco sp., T. eulepidotus, Gymnodraco acuticeps and T. nicolai can be con­sidered rather common species, showing a fre­quency of occurrence between 5 and 25% of the hauls. The other species, found in less of the 5% of the samples, may be considered occasional species (Table 2).

As for the vertical distribution, higher species diversity was found between 0- and 200-m depths. However, T. bernacchii and T. hansoni were

Table 2. Frequency of occurrence ('Yo) of the fish species and mean number of specimens per haul at the different depth levels (standard deviation in brackets), sampled by trammel and gill nets

Species F('Yo) O-IOOm 28 hauls lOl-200m 27 hauls 201-400m 9 hauls >400 m 9 hauls

Nototheniidae Dissostichus mawsoni 1.4 Trematomus bernacchii 86.3 35.1 (±29.9) 18.3 (±23.6) 2 (±2.2) 0.2 (±o.4) Trematomus eulepidotus 9.6 Trematomus hansoni 52.1 1.7 (±2.5) 1.2 (±2.1) 4.6 (±IO.I) 3.7 (±2.4) Trematomus loennbergii 13.7 1.1 (±3.0) 9.3 (±6.6) Trematomus newnesi 20.5 4.9 (±18.7) 0.3 (±0.5) Trematomus nicolai 5.5 Trematomus pennellii 45.2 1.3 (±3.I) 3.9 (±4.4) 0.6 (±1.0) Trematomus scotti 1.4

Bathydraconidae Cygnodraco mawsoni 13.7 Gymnodraco acuticeps 8.2 Prionodraco evansii 1.4

Channichthyidae Chaenodraco wilsoni 1.4 Chionodraco hamatus 69.9 5.4 (±7.1) 7.8 (±11.5) 2.1 (±2.0) Chionodraco myersi 4.1 Cryodraco sp. 11.0 Pagetopsis macropterus 12.3

Artedidraconidae Histiodraco velifer 1.4 Pogonophryne scotti 2.7

sampled over the whole depth range, T. bernacchii being the shallower (Table 2). On the other hand, C. hamatus and T. pennellii were collected in the first three depth levels (see Table 2), with a relative abundance peak in the lOO-200-m depth range. Some species, such as T. nicolai, T. newnesi, Cygnodraco mawsoni, Gymnodraco acuticeps and Cryodraco sp. seem confined in shal­low waters, whereas other species, such as T. loennbergii, Chionodraco myersi and Dissostichus mawsoni, were caught only in deep waters.

Feeding

Thirty seven prey taxa, of which 22 were polychaetes, were identified in the diet of T. bernacchii (Vacchi et aI.1994). Besides polychaetes

The Coastal Fish Fauna of Terra Nova Bay, Ross Sea, Antarctica 461

(Barrukia cristata and Amphicteis efr. midas), bivalves (Adamussium colbecki) and euphausiids were the main food source. Nototheniids and amphipods seem to be secondary prey groups (Fig. 2). In T. pennellii, polychaetes (in parti­cular Amithas membranifera, Barrukia cristata and Aglaophamus ornatus) were the main prey; amphipods were also well represented, whereas fish eggs constituted a secondary food. The diet similarity between T. bernacchii and T. pennellii was 23% by number and 26% by weight (Vacchi et al. 1994; Fig. 2).

Stomach content analysis of T. hansoni revealed that this species is mainly piscivorous. Fish prey were often represented by juveniles and provided a dietary coefficient about ten times higher than the secondary prey, i.e. the fish eggs

T,emololllus /oellllbergii TrellllltoltJus Itwrson;

Fig. 2. Relative abundance (expressed by graphic representa· tion of the dietary coefficient Q of the most common prey of the nototheniid species collected in this study

DDccapods

D Fishes D Polychaetes

IilIAmphipods

T'CllllllolIIlIS IIl!lmcsi

D Fishes (post larvae)

Euphausiids

EI Amphipods

D Fishes

• Fish eggs

D Polychactcs

IIIlsopods • CrinoId,

T,elllololll/lS berllocchii T,elllololl"I> penllellii

o Polyehaetes

• Euphausiids lID Bival\,cs

o Fishes !;I Amphipods

• Echinoid,

D Polychaetcs !;I Amphipods

iii FIsh eggs

Il!I Pycnogonids

462 M. Vacchi et al.

(Fig. 2). Polychaetes and decapods (Chorismus antarcticus and Notocrangon antarcticus together) were secondary food items.

In T. loennbergii, a total of 174 food items belonging to 28 taxa were identified, most of which were polychaetes (La Mesa et al. 1997). In this species, the decapods C. antarcticus and N. antarcticus, as well as fishes, represented the main food (Fig. 2).

The diet similarity between T. hansoni sampled below 300-m depth and T. loennbergii was 27.3% by number and 49.0% by weight, whereas between T. hansoni sampled above 300-m depth and T. loennbergii, it was 48.6% by number and 65.9% by weight. The difference in food com­position observed in the diet of T. hansoni was probably due to the change of the benthic prey species in relation to depth of sample. This influ­enced the value of food similarity between the two nototheniids.

In the stomach content of T. newnesi, Vacchi and La Mesa (1995) found mostly zooplank­tonic preys, such as fish larvae, amphipods and euphausiids (Fig. 2). Postlarval stages of T. new­nesi, both as number caught and biomass, was the main diet component, indicating a marked can­nibalistic behaviour not previously detected.

Reproduction

Most specimens of C. hamatus caught in Terra Nova Bay during December-February were in spawning condition, with a gonado-somatic index (GSI) ranging from 7 to 14.4% in females and from 1.5 to 1.8% in males. The percentage of ripe specimens decreased progressively from Decem­ber to February in both sexes (Fig. 3). The range of mean egg diameter and fecundity of C. hamatus was respectively 4-4.6mm and 2360-3317 eggs (2.9-7.9 eggs g-l of total weight being the range of relative fecundity) (Vacchi et al. 1996).

Data on T. hansoni suggested that, in the same period, also this species spawns: GSI in females ranged from 9.9 to 11.8% and in males from 0.15 to 0.23%. A high percentage of females were gravid but no ripe males were found (Fig. 4). Egg size and total fecundity of T. hansoni from Terra Nova Bay were 3.1-3.6 mm and 5149-6527 eggs, respectively, both increasing from December to February. Relative fecundity of this species ranged between 9.8 and 16.5 eggs g-l of total weight (Vacchi et al. 1996).

T. bernacchii showed a decrease in percentage of spent females and an increase of specimens in an early developing stage of ovarian maturity from December to February. Almost all the males were in early gonad development stages and no ripe specimens were found during the whole sampling period (Fig. 5; Vacchi et al. 1996).

Age and Growth

Age estimate was made by otolith section reading in T. bernacchii and C. hamatus (La Mesa et al. 1996; Vacchi et al. 1992). Of the 457 right otoliths of T. bernacchii examined, 211 otoliths of females ranging from 157 to 333 mm TL and 122 otoliths of males ranging from 154 to 256mm TL were aged. The age range was 7-21 years for females and 8-16 years for males. The Von Bertalanffy growth curve (Fig. 6) was fitted to the length-at -age data for females and males and is summarized in the following equations:

Lt = 273.5[I_e-O.109(t+2.101] (males, n = 122)

Lt = 422.2[1- e-O.055(t+I.92I] (females, n = 211)

The yearly length increment was very low, about 7 mm for males and 11 mm for females. The values of the Pauly Growth Performance Index (P) were 1.46 for males and 1.82 for females.

Our C. hamatus samples comprised mostly adults, with females ranging from 320 to 430 mm TL and males from 300 to 400 mm T1. Of 118 spec­imens of C. hamatus analyzed, 30 females and 70 males were aged, providing an estimated age range of 5-10 years. For this species, the Von Bertalanffy growth function was not fitted to the experi­mental data because, dealing only with relatively old individuals, such a fitting would probably have smoothed the extrapolation curve.

Discussion

The faunistic composition and species diversity in Terra Nova Bay do not differ very much from the other coastal fish communities inhabiting other sites of east Antarctica, such as Lutzow-Holm Bay (Naito and Iwami 1982), the Vestfold Hills region and Mawson Sea (Williams 1988; Vacchi et al. 1996), Adelie Land (Hureau et al. 1965) and McMurdo Sound (DeWitt 1971; DeVries and Eastman 1981). Some differences concerning the presence/absence of a few species

Fig. 3. Seasonal pattern of maturity stages frequency (above) and gonado-somatic index (below) of Chionodraco hamatus

100%

80%

i' 60%

'" 1r 40% "-

20%

The Coastal Fish Fauna of Terra Nova Bay, Ross Sea, Antarctica 463

Females (n = 85)

l::l 5

04 Ill)

0 2 . 1

0% +---'------'

100%

80%

i' 60% :> [ 40% "-

20%

Dec Jan Month

Males (n = 45)

Feb

El5

0% !-JlIIIIIIII_~ t-L------'--j

Dec Jan

Month

Females (n = 85)

Feb

§ :~ t +---!--+--~-< - __ - !-..-,

- mean + Se • mean

- mean - Sc

0.2

u; 0, 15

(;) 0, 1

Dec

ii

Jan

Month

Males (n = 45)

Feb

• - mean + Sc • mean

- mean - Sc

0.25

1 0.05

0 -1-----1-------+----..-,

in the different areas can be explained more in terms of different selection of fishing gear used rather than a real paucity of some species. For instance, the lack of icefish in McMurdo Sound is most likely related to the particular fishing tech­nique adopted at this site (lines and traps from

Dec Jan Month

Feb

drilled holes in the pack ice). Indeed, as we can see from our catches, channichthyids do not seem vulnerable to lines and traps. This is confirmed at Davis station, where 99% of the specimens of the icefish C. hamatus were caught by gill net (Williams 1988).

464 M. Vacchi et a1.

~ c " " ~ .....

20

15

~IO 5

100%

80%

60%

40%

20%

0%

Dec

Dec

Females (n ~ 115)

Jan

Monlh

Males (n a 205)

Jan

Month

Females (n ~ 115)

Feb

Feb

6 5

04 ElI3

02

.1

- mean + Se

• mean

- mean - Se

Fig. 4. Seasonal pattern of maturity stages frequency (above) and gonado·somatic index (below) of Trematomus hansoni

o +-----------+-----------+---------~

Dec

i

0,5

Jan Monlll

Males (n ~ 205)

•

Feb

• ~ ': I O +---------r-------~--------~

Dec Jan Momh

Feb

The capture at Terra Nova Bay of only one adult individual of Notothenia coriiceps can be considered as the southernmost finding of this species (Miller 1993). The paucity of this species distinguishes Terra Nova Bay from other Antarc-

- mean + Se

• mean

- meM - Se

tic coastal areas, such as, for instance, Adelie Land, where N. coriiceps is very abundant in shallow waters (Hureau et al. 1965).

The analysis of biometric characteristics of Cryodraco specimens stressed some difficulties

Fig. 5. Seasonal pattern of maturity stages frequency (above) and gonado.somatic index (below) of Trematomus bernacchii

100%

80%

g- 60% ~ If 40% ~

20%

The Coastal Fish Fauna of Terra Nova Bay, Ross Sea, Antarctica 465

females (n ~ 660)

O%LJ----~~ .... ~JB .... ~

a s 0 4 FiIl3

0 2 .1

100%

80%

g- 60% '" " [ 40% u..

20%

0%

0,5

Dcc

Dec

Jan

MOnlh

Males (11 ~ 323)

Jan

Month

Females (n ~ 660)

•

feb

Feb

•

r:::l S

04

11'13

0 2 .1

- !Ilean + Se • mcan

- mean - Se ~': f 0 +-- ---+-----+----;

0,25

0,2

iii 0,15

o 0, 1

O,OS

Dec Jan

Month

Males (n ~ 323)

•

feb

- mean + Se

• mCan

- mean - Se

o +-----r----~----~

in obtaining a clear taxonomic diagnosis of the species belonging to this genus. The specimens caught in Terra Nova Bay showed some, but not all, of the distinctive characters of Cryodraco atkin-

Dec Jan Month

Feb

soni described by Regan in 1914 (La Mesa and Vacchi 1997).

Considering the species richness in relation to depth, our results partially disagree with literature

466 M. Vacchi et a1.

400

350

300

I 250

-= ~ 200 .!l

~ 150 ~

100

50

400

350

300

I 250

-= ~ 200 .!l

~ 150

100

50

a

o 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

Age (years)

b

O+-+-+-+-+-+-+-t--t--t--I--f---1--1--1--1

o 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

Age (years)

Fig. 6. Von Bertalanffy growth curve for males (a) and females (b) of T. bernacchii

data from east Antarctica, that indicate the great­est number of fish species occurring in deep waters, between 250 and 600m (DeWitt 1971). However, the higher species diversity in shallow waters found at Terra Nova Bay (Table 2) may be explained mostly by the more intensive sampling made in the waters less than 200 m depth.

As for the feeding pattern of the most common fish of Terra Nova Bay, the comparison of the trophic niche was carried out between species showing the same areal distribution. The low diet similarity observed between T. bernaeehii and T. pennellii indicates a partition of food resources. Some organisms are preyed by only one species, pycnogonids and gastropods (T. pennellii), echi-

noids (T. bernaeehii) being an example. Other taxa, such as molluscs and amphipods, fishes and euphausiids, are consumed in significant amounts only by T. bernaeehii. As regards polychaetes, which are the most common prey of both species, the burrow-dwelling species Aglaophamus ornatus, Ophelina gymnopige and Seoloplos mar­ginatus were mainly preyed on by T. pennellii. Finally, the diet richness of T. pennellii and T. bernaeehii was outlined, as well as the low trophic overlap between the two species. The same situation was found when comparing T. hansoni and T. loennbergii. Our data on the diet of these two species suggest that the interspecific competi­tion is partially avoided either by taking different preys or by taking different amounts of the same prey. Moreover, the same prey was often consumed by different size categories of the two species.

As regard the pelagic fish species commonly found at Terra Nova Bay, namely T. newnesi, our results on feeding habit of adult fish confirm the zooplanktonic feeding behaviour of this species, reported in previous studies on juveniles (Casaux et al. 1990; Daniels 1982; Targett 1981). In the stomach contents of our specimens we found a high number of postlarval stages of fish (638 indi­viduals), of which the majority were T. newnesi. This high level of cannibalistic behaviour has not been detected previously, although cannibalism has been reported in some larval stages of T. newnesi caught in the Bransfield Strait (Balbontin et al. 1986).

Our estimates of age and growth of T. bernae­ehii at Terra Nova Bay do not agree with those of Wohlschlag (1962) at McMurdo Sound and Hureau (1970) at Adelie Land, who determined both higher growth rates and lower estimates of longevity. Besides the natural intraspecific vari­ability due to different environmental conditions at different sampling sites, the different ageing methodologies used (scales for McMurdo speci­mens and whole otoliths for Adelie Land speci­mens), could account for the discrepancy in the results. Conversely, the growth rates and the maximum age obtained by Ekau (1988) on T. bernaeehii specimens from the Weddell Sea are generally in agreement with our data. Ekau found a maximum age of 21 years and a K value of 0.088 from the Von Bertanlaffy growth formula, which fall between our values for males and females. As concerns the age and growth of C. hamatus, not previously studied, our data show that both sexes grow very slowly in the sampled length range, but

females are, on average, larger than males of the same age and increase their size at a greater rate.

Finally, our results on the reproduction pat­terns of T. bernacchii, T. hansoni and C. hamatus are in good agreement with the existing informa­tion on the spawning period of the High Antarc­tic Zone species, which show a high proportion of spring and especially summer spawning species (Kock 1992). Moreover, the low fecundity (both relative and total) along with the relatively large yolky eggs that are probably spawned annually as a single batch, seem to be common to the three species, and, on a wider scale, they represent some of the reproductive strategies most frequently adopted by the Antarctic fish fauna (Kock and Kellermann 1992).

Acknowledgements. This study was financially supported by the Italian National Programme for Antarctic Research (PNRA).

References

Anonymous (1989) Report of the Working Group on Fish Stock Assessment. In: Report of the 8th Meeting of the Scientific Committee of the Commission for the Conser­vation of the Antarctic Marine Living Resources, 6-10 November 1989, CCAMLR, Hobart, Australia, Annex 6, pp 183-295

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