Antarctic Science 13 (4): 385-392 (2001) 0 Antarctic Science Ltd Printed in the United Kingdom Seasonal relative abundance of fish larvae inshore at jles Kerguelen, Southern Ocean P. KOUBBI1*,G. DUHAMEL2and C. HEBERTI 'Ichtyoe'cologie marine, Universith du Littoral Cbte d'Opale, UPRES-A 8013, 17, avenue Ble'riot. BP 699, F-62227 Calais cedex, France 'Laboratoire d 'Ichtyologie Gtntrale et Applique'e, Mushurn national d 'histoire naturelle, 43, rue Cuvier, F- 7523I Paris Cedex 05, France *corresponding author: Koubbi@univ-tittoralJir Abstract: Ichthyoplanktonsampling was conducted seasonallywith36 surveys betweenspring 1989 and spring 1992 in four bays in the Kerguelen archipelago: Morbihan, Baleiniers, Choiseul and Audierne. Golfe des Baleiniers is open to the shelf whereas Choiseul and Audierne are long fjords. Golfe du Morbihan is a very large and protected area open to the shelf at its eastern end. Larvae of neritic species were abundant outside whereas larvae of inshore species were abundant inside the Golfe du Morbihan. Larval Lepidonotothen squamifrons were detected during summer every year whereas larvae of Champsocephalus gunnari were observed in only two years, mainly in the northern coastal zone. For both species, our results support coastal spawning grounds in addition to those on the shelf slope. Larvae of the mesopelagic fish Krefltichthys anderssoni were dominant primarily during winter; this was linked to homogenisation of the water column over the shelf and the coastal zone. Larvae ofNotothenia cyanobrancha were present throughout the year everywhere, which is linked to the year long pelagic earlylife-history phase. Received 27 June 2000, accepted 14 August 2001 Key words: coastal zone, fish larvae, multivariate analysis, Notothenioids Introduction Materials and methods The Kerguelen archipelago is the largest island group in the Sites Indiansector oftheSouthemOcean(tota1 area 6500km2).The main island is surrounded by more than 400 isles and islets Golfe du Morbihan is semi-enclosed and communicates to the (Fig. 1). Deep fjords and bays dissect the shelf (Nougier open ocean over a sill at about 50 m depth located in its eastern 1971). The coast has a belt kelp of Macrocystis pyrifera part. The westernpart ofthe bayhasmanydeepandlong fjords (Linnaeus) Agardh over 186 km2 (Belsher & Mouchot 1992) with many islands; the eastern part is a vast area with few and 10% of Golfe du Morbihan (Delepine 1976). This kelp islands. Koubbi et al. (1990) described larval stages from this belt is a habitat for juvenile fish (Hureau 1970, Duhamel bay. Golfe des Baleiniers, in the north-eastern part, is the 1987a). largest of the Kerguelen Archipelago. It has a mean depth of These coastal zones are dilution basins due to inputs of 50 mwithadeep canyonat IOOmorientednorth-eastward and freshwater derived fiomprecipitation or rivers from the Cook contains numerous islands and bays on its southern and Glacier (Murail et al. 1977). The Antarctic Circumpolar western borders. Duhamel(l987a, 1987b, 1995) described Current and the Antarctic Polar Front influences the oceanic this area as a spawning ground and larval nursery for icefish zone (Park etal. 1993). This front meanders around the Champsocephalus gunnari. It is also a nursery ground for Kerguelen shelfand its position varies (Charriaud 1993). The larvae of Lepidonotothen squamifrons (Koubbi et al. 2000). demersal juvenile/adult inshore and shelf fish are well known Golfe Choiseul, west of Golfe des Baleiniers, is oriented (Hureau 1970,Duhamel1987a). The ichthyoplankton(inshore, northward. Inward, it has two long and deep bays ofmore than shelf, seamount and oceanic) andmesopelagic fishassemblages 150 m mean depth, with entrance sills at about 50 m. To the have been investigated in relation to hydrology and frontal west, the Peninsule Loranchet protects it from the prevailing zones (Koubbi et al. 1991, Koubbi 1992, 1993, Loeb et al. west wind. To the east, large islands and long bays, connected 1993, Duhamell998, Duhamel et al. 2000). to the Golfe des Baleiniers, limit this area. Lepidonotothen We studied the importance of the inshore zone for larval squamiji-onsspawns in its fjords (Koubbi et al. 2000). In the fish. Four areas were investigated. Comparison of larval fish south of the archipelago, a narrow bay with a fjord at one end dominance and diversity from seasonal surveys in Baleiniers, marks Baie d'Audierne and Baie de la Table. Mean depth is Choiseul and Audierne are presented in comparison to Golfe about 100 m for the Baie d'Audierne and 200 m for Baie de la du Morbihan to study larval succession. Table. 385 386 P. KOUBBI eta/. Fig. 1. The coastal zones of the Kerguelen archipelago. Positions of samples and polygons used for mapping abundances by mean of a GIs. Sampling Numerical analysis From December 1986 to November 1990, when possible, Species maximum abundance in polygons of ten minutes monthly samples were collected in Golfe du Morbihan at nine longitude and five minutes latitude were mapped, by a stations (Fig. 1) (Koubbi 1992). From October 1989 to Geographic Information System, to show optimal distribution October 1992, thirty-six seasonal surveys were undertaken, and abundance of species. with a total of 775 samples (Table I, Fig. 1). The number of Because ofthe highnumber ofsamples withnull abundance, stations differed among surveys due to sea conditions. In it was difficult to analyse the spatial distribution of larval Golfe des Baleiniers, fourteen surveys were made in a grid of assemblages using all sectors. Golfe du Morbihan was 28 to 44 stations, except February 1990 and July 1991 when analysed separately as it was too unusual to compare well with less than five samples were taken. Twelve surveys were done the three other areas. in the Audierne Sector with 7 to 21 sampling stations. Ten For the analysis excluding Golfe duMorbihan, we computed surveys were conducted in the Choiseul Sector with between the percentage of dominance of each species per survey. The 10 and 18 stations. Sea surface temperatures were recorded at aim was to standardize the data to eliminate differences in each station by surface thermometers. abundance per sampling station and between surveys. A Fish larvae were sampled with a bongo net of 500 pmmesh, Correspondance Analysis (CA) was carried out on the 36 6 1 cm diameter and 3.6 m long. Oblique tows, at a speed of 2 surveys and ten species. This analysis is well suited to data knots, were from the surface to near the bottom or to 200 m for percentage (Benzecri 1973). Eggs, Zanclorhynchus spinifer deeper water. Flowmeters (General Oceanic 2030R) were juveniles and Channichthysrhinoceratus larvae were removed used to determine the volume of water filtered. from the analysis because they were rare. Gymnoscopelus Samples were fixed in seawater formalin (5%)buffered with larvae were pooled for the analysis, as they were otherwise too sodium tetraborate. Samples were sorted in the laboratory. few. It is possible to represent the correspondence of each Fish larvae and fish eggs were removed under a variable (species) and observation (surveys) in the same stereomicroscope. Identification of notothenioid larvae was framework due to barycentric projection. Following CA, the using descriptions ofNorth & Kellermann (1989) and Koubbi first three axes of inertia were used to calculate inter-euclidian et al. (1990). Myctophid larvae were identified according to distances and a classification based on group average. Groups Moser & Ahlstrom (1970), Efremenko (1986) and North & driven from a dendrogram were plotted on each factorial White (1982). Counts of all eggs and larvae were converted plane. Observations for each axis were also plotted versus into number of individuals per 10 000 m3. time and compared with seasonal meansea-surface temperature. FISH LARVAE AT KERGUELEN 387 Table 1. Survey code, date and number of stations sampled at Kerguelen in Baleiniers, Choiseul and Audieme sectors. Audierne ...... Survey from to No. of samples Audieme Al 1 510 1/90 9 A2 18/04/90 I9/04/90 7 A3 19/07/90 2 1/07/90 13 A4 12112/90 13/12/90 9 A5 24/01/91 2710 119 1 19 A6 I6/05/9 1 18/05/91 21 A7 2 1/08/9 1 22/08/9 1 20 A8 0411 1/91 0511 1/91 21 29/02/92 0 1/03/92 .J .......................................... A9 16 J"I-8'1 ,."do ,"l.90 Jan.9, J"l.9, h".S2 J"I.92 A10 07/04/92 16 Date A1 1 09/07/92 15 Baleiniers A12 0311 0192 05/10/92 15 Baleiniers BI 26/10/89 0111 1/89 31 B2 12/02/90 13/02/90 5 B3 10/05/90 16/05/90 33 B4 12/08/90 16/08/90 37 B5 2711 1/90 01/I 2/90 28 B6 0310 1/9 1 0810 119 1 38 B7 13/04/91 1510419 1 34 B8 03/05/91 3 B9 01/07/9 1 09/07/91 40 nJ ....................................... BIO 1011 019 1 1211019 1 44 J"l-89 ,a"-90 Jul-00 J.n-9, J"l.91 J."d* J"l.92 Date BI 1 04/02/92 08/02/92 37 B12 07/05/92 10/05/92 37 Choiseul 813 15/07/92 17/07/92 37 814 2711 0192 3011 0192 38 Choiseul C1 12/05/90 13/05/90 12 c2 2811 1/90 2911 1/90 12 I 1 \ c3 0510 119 1 06/01/91 16 c4 15/04/91 1 610419 1 10 c5 30/06/9 1 0 1/07/9 1 17 C6 081 1019 1 1011 019 1 18 c7 06/02/92 08/02/92 16 C8 10/05/92 16 ........................................ hid9 Jan.90 J3-00 Jan-9, J"l.Sl Jan.92 J"l.92 c9 17/07/92 18/07/92 15 Date CIO 2 91 10192 30/10/92 17 Fig.