Comparison of the two alternative early life-history strategies of the Antarctic fishes Gobionotothen gibberifrons and Lepidonotothen larseni

Abstract

ABSTFUCT: Two major early life-history strategies of notothenioid fishes in the lower Antarctic are identified based upon the length of pelagic development: species that complete pelagic development within 1 summer season ('summer larvae') and species with extended pelagic development that continues over winter months ('winter larvae'). These 2 life-history strategies were compared using otolith techniques to reveal growth histories, hatching periods, and development rates of larval Gobionotothen gibberifrons (summer larvae) and Lepidonotothen larseni (winter larvae) from the Antarctic Peninsula (summer 1986/87) and South Georgia (summers 1987/88 and 1988/89). Back-calculated growth over the first 40 d after hatching was modeled exponentially and instantaneous growth rates (r) were calculated. Both species grew at similar rates with respect to length (r = 0.01) and with respect to weight (r = 0.02 to 0.03). The hatch period of both species was delayed off the Antarctic Peninsula (lateNovember to mid-December) compared to South Georgia (early to mid-November), as is the onset of the productive season at higher latitudes. Summer larvae have no growth advantage but do develop more quickly than winter larvae, offering the ability to reduce the time spent in a vulnerable life-history stage. As currently hypothesized, winter larvae may take advantage of an extended period for growth. using pelagic resources unavailable to summer larvae, or recruiting to the demersal environment when competition from summer recruits is lowest.