Reproductive resilience of ice‐dependent Antarctic silverfish in a rapidly changing system along the Western Antarctic Peninsula

The Western Antarctic Peninsula (wAP) is globally one of the systems most heavily impacted by climate change, notably steep declines in sea ice extent. In forage species, reproductive resilience to change is particularly important because population fluctuations are rapidly communicated through the system via trophic interactions. The reproductive traits of the ice‐dependent forage species Antarctic silverfish (Pleuragramma antarctica) from different areas along the wAP and at the tip of the Antarctic Peninsula were investigated through macroscopic and histological analyses of gonads, with the aim to assess its reproductive potential and to test for spatial differences in fecundity and spawning season. Fish samples were collected in late summer off Charcot Island, in Marguerite Bay and off Joinville Island; no fish were caught in the central wAP. Samples from Charcot Island and Marguerite Bay consisted of adults in developing gonad stage, whereas those from Joinville consisted almost exclusively of juveniles. Mean GSI was relatively low (2–3%) and similar in both sexes, as specimens were still far from being actively reproducing. Developing females exhibited two discrete, though partially overlapping modes of oocytes of different size, with vitellogenic oocytes measuring 0.5–1.0 mm. Absolute and relative fecundity ranged between 3000 and 12,000 eggs per female and between 80 and 190 eggs·g^?1, with a strong relationship between absolute fecundity and body size. These results were consistent with a single population at Charcot Island and Marguerite Bay and indicated substantial reproductive potential, which may mitigate population isolation and reductions in habitat availability but cannot ultimately offset catastrophic loss of spawning habitat linked to sea‐ice retreat.     

三种南极鱼种分布的研究

根据英国南极考察中心（ＢＡＳ）在南极半岛水域（１９８８／１９８９）调查资料分析了三种南极鱼种（南极多线鱼（Ｐｌｅｕｒａｇｒａｍｍａａｎｔａｒｃｔｉｃｕｍ），南极电灯笼鱼（Ｅｌｅｃｔｒｏｎａａｎｔａｒｔｉｃａ），博氏原灯笼鱼（Ｐｒｏｔｏｍｐｅｔｏｐｈｕｍｂｏｌｉｎｉ）的分布．南极多线鱼分布于受韦岛（Ｗｅｄｄｌｅ）海水影响的水域（丰度值：０．０５４至１．７７５４尾／１０００ｍ３），指出绝大多数幼鱼（２６．０至５４．０ｍｍ，ＳＬ）发现在上层水域．南极电灯笼鱼和博氏原灯笼鱼分布于东南太平洋水域和贝令施森（Ｂｅｌｌｉｎｇｓｈａｕｓｅｎ）水域（丰度值：０．０５１２至０．９９３５和０．０３９４至０．３９０９尾／１０００ｍ３）．此两种灯笼鱼种的分布水深一般大于５００ｍ。     

Length frequency analysis ofPleuragramma antarcticum,Electrona antarctica,Protomyctophum bolini

British Antarctic Survey (BAS) data collected near the Antarctic Peninsula area were used in this 1988/1989 study on the length frequency of three Antarctic fish species (Pleuragramma antarcticum, Electrona antarctica and Protomyctophum bolini) showing that the standard length (SL) ofP. Antarcticum ranged from 26.0 mm to 161.0 mm, that the 26.0 mm to 54.0 mm SL juveniles could be considered to be the age group 1 fish, and that the SL ofE. antarctica ranged from 39.4 mm to 89.7 mm for the males and 48.0 mm to 118.0 mm for the females, which may contain at least 6 age groups. This is more than previously thought.P. Bolini had 29.2 mm to 60.2 mm SL and complicated age composition.     

LENGTH FREQUENCY ANALYSIS OF PLEURAGRAMMA ANTARCTICUM,ELECTRONA ANTARCTICA,PROTOMYCTOPHUM BOLINI

British Antarctic Survey(BAS)data collected near the Antarctic Peninsula area were used in this1988/1989 study on the length frequency of three Antarctic fish species(Pleuragramma antarcticum,Electrona antarctica and Protomyctophum bolini)showing that the standard length(SL)of P.Antarcticumranged from 26.0 mm to 161.0 mm,that the 26.0 mm to 54.0 mm SL juveniles could be considered tobe the age group 1 fish,and that the SL of E.antarctica ranged from 39.4 mm to 89.7 mm for themales and 48.0 mm to 118.0 mm for the females,which may contain at least 6 age groups.This ismore than previously thought.P.Bolini had 29.2 mm to 60.2 mm SL and complicated age com-position.