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Temperature Effects on Eggs and Yolk Sac Larvae of the Summer Flounder at Different Salinities
Author(s) -
Watanabe Wade O.,
Ellis Simon C.,
Ellis Eileen P.,
Feeley Michael W.
Publication year - 1999
Publication title -
north american journal of aquaculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.432
H-Index - 41
eISSN - 1548-8454
pISSN - 1522-2055
DOI - 10.1577/1548-8454(1999)061<0267:teoeay>2.0.co;2
Subject(s) - hatching , biology , salinity , zoology , photoperiodism , yolk sac , broodstock , larva , flounder , yolk , fishery , fish <actinopterygii> , botany , ecology , embryo , aquaculture
The combined effects of temperature and salinity on eggs and yolk sac larvae of summer flounder Paralichthys dentatus were examined under controlled laboratory conditions. Fertilized eggs (early gastrula stage), obtained by induced spawning of captive broodstock at 17°C and 36 g/L salinity, were stocked (60 eggs/L) into forty‐five 5‐L translucent containers at temperatures of 16, 20, and 24°C and at salinities of 22, 28, and 34 g/L. Light intensity was 500 lx, and photoperiod was 12 h light: 12 h dark. At 16°C and 20°C, hatching rate was moderate to high (57.8‐99.0%) at all salinities; at 24°C, hatching rate was high at 34 g/L (75.2%) but poor at 28 g/L (0%) and 22 g/L (30.5%), indicating a high‐temperature‐low‐salinity inhibition ( P < 0.001). At the first feeding stage and at the stage when 97% of the yolk sac was absorbed (YSA), notochord lengths increased ( P < 0.05) with decreasing temperature, from a minimum at 24°C to a maximum at 16°C. Yolk utilization efficiency appeared to show a similar trend (0.05 < P < 0.10). Average time from the first‐feeding to the 97% YSA stage in unfed larvae ranged from 2.4 to 4.3 times longer at 16°C (18.3 h) than at 20°C (4.3 h) or 24°C (7.7 h). At a salinity of 34 g/L, median survival time (MST) was moderate (140‐193 hours postfertilization, hpf) under all temperatures; at 22 and 28 g/L, MST was enhanced (222‐294 hpf) at 16°C and markedly reduced (43.1‐73.2 hpf) at 24°C, indicating low‐temperature‐low‐salinity synergism, as well as high‐temperature‐low‐salinity inhibitory effects ( P < 0.001). A temperature of 16°C, possibly associated with peak abundance of eggs and larvae in nature, is optimal for culture of summer flounder embryos and yolk sac larvae. At this temperature, growth, yolk utilization efficiency, time to initiate exogenous feeding, and tolerance to reduced salinities are maximized. Simultaneous exposure to high temperatures (24°C) and reduced salinities (22‐28 g/L) may increase mortality and affect year‐class strength.