Bulletin of the Sea Fisheries Institute 2 (156) 2002 - CEEMaR

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Sexual maturation of mackerel icefish ..... 27 MALES Elephant FEMALES 4,0 4,0 3,5 3,5 3,0 3,0 2,5 2,5 2,0 2,0 1,5 1,5 1,0 09 10 11 12 01 02 03 04 05 1,0 09 10 11 12 01 02 03 04 05 South Shetland 4,0 4,0 3,5 3,5 3,0 3,0 2,5 2,5 2,0 2,0 1,5 1,5 1,0 09 10 11 12 01 02 03 04 05 1,0 09 10 11 12 01 02 03 04 05 Kerguelen Islands 4,0 4,0 3,5 3,5 3,0 3,0 2,5 2,5 2,0 2,0 1,5 1,5 1,0 09 10 11 12 01 02 03 04 05 1,0 09 10 11 12 01 02 03 04 05 months months DISCUSSION This paper analyzes fish maturation according to criterion of achieving initial sexual maturity (L 50 ) (gonad stages II-V). The lowest L 50 in the Atlantic Antarctic sector was recorded for the stock from South Georgia. Stocks located more to the south had a relatively higher L 50 . Similar observations have also been made by other researchers (Kock 1981, 1990, 1992, Kock et al. 2000, Everson et al. 1996, Olsen 1955) (Table 4). Despite the fact that the fishing grounds are located in closeproximity to each other, L 50 is slightly higher in the Shag Rocks stock than in that from South Georgia. In the Indian Ocean sector, the L 50 for the stock from the Kerguelen Islands is
28 JÓZEF SOSIÑSKI and KORDIAN TRELLA 4,2 4,0 3,8 males < L95 females < L95 males > L95 females > L95 average gonad maturity stage 3,6 3,4 3,2 3,0 2,8 2,6 2,4 2,2 2,0 1,8 09 10 11 12 01 02 03 04 05 months Fig. 10. Average sexual maturity of male and female C. gunnari in the fishing ground of South Georgia in subsequent months of the study. similar to that from South Georgia, which was confirmed by both the current results and those of other researchers (Kock 1992, de la Mare et al. 1998). Kock (1989) reports that the results obtained by Duhamel also indicate that L m50 is similar for both stocks. The habitats of these stocks are located closer to the Antarctic convergence zone, their environmental conditions are similar and they both differ from those in which the more southerly stocks live. The length at which initial sexual maturity is achieved in relation to maximum length is the shortest for C. gunnari from South Georgia (males – 39.2%, females – 34.9%). The same figures are quoted by Kock (1981, 1992) and de la Mare et al. (1998). It is interesting that the L 50 to L max ratio for fish from Shag Rocks is closer to that of the population located more to the south than that of the of South Georgia, as was the case with L 50 . According to Kock (1981), the L m50 is higher for males than females in stocks from South Georgia and South Shetland Island. Also Kock et al. (2000) reported higher L 50 and L m50 for males than females from South Orkney Island and Elephant Island. In the stock from South Shetland Island, the males have a higher L 50 while L m50 is higher for the females. In the majority of cases, the authors also observed higher L 50 for males, with the exception of stocks from the South Shetland and Kerguelen Islands. The authors observed the tendency of the L 50 value in South Georgia stock to stabilize over a longer period of time. Similar observations were made by Kock and Kellermann (1991) with regard to L m50 . When mature, the majority of fish species spawn annually. However, it was confirmed that some mature C. gunnari do not spawn in a given year (Sosiñski 1985, Kock 1989, 1990, 1992, Everson et al. 1996, Everson et al. 2000). This leads to the conclusion that maturation is
Page 1 and 2: ISSN 1429-2335 Bulletin of the Sea
Page 3 and 4: 4 WIES£AW BLADY, JAN NETZEL and JA
Page 9 and 10: 20 23 26 29 32 35 38 41 44 47 50 53
Page 11 and 12: 12 WIES£AW BLADY, JAN NETZEL and J
Page 13 and 14: 14 WIES£AW BLADY, JAN NETZEL and J
Page 15 and 16: 16 JÓZEF SOSIÑSKI and KORDIAN TRE
Page 25: 26 JÓZEF SOSIÑSKI and KORDIAN TRE
Page 33 and 34: 34 VIDA ŽILIUKIENE The fish fauna
Page 35 and 36: 36 VIDA ŽILIUKIENE Table 1. The ex
Page 37 and 38: 38 VIDA ŽILIUKIENE 1997.06.03 1999
Page 39 and 40: 40 VIDA ŽILIUKIENE Frequency [%] F
Page 41 and 42: 42 VIDA ŽILIUKIENE REFERENCES Anne
Page 43 and 44: BULLETIN OF THE SEA FISHERIES INSTI
Page 45 and 46: Morphomechanic changes during embry
Page 55 and 56: BULLETIN OF THE SEA FISHERIES INSTI
Page 57 and 58: Variability of sprat peak spawning
Page 67 and 68: 70 JÓZEF SOSIÑSKI AND ANDRZEJ KOM
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WSKAZÓWKI DLA AUTORÓW INFORMACJE
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