The RNA, DNA, and protein content of larval cod Gadus morhua reared in the laboratory at 3 temperatures and 3 densities of prey was measured. The data were used to define a quantitative relationship between RNA/DNA ratio (R/D), water temperature (T ), and protein-specific growth rate (SGR, % d -1 ). The nucleic acid content of each larva was determined with both a 2-dye flow-injection fluorometric assay (FIA) and a 1-dye/1-enzyme fluorometric microplate assay (MFA) in order to calibrate each methodology. The resulting equations were: SGR = 3.65 R/D + 1.02 T -13.05 for FIA, and SGR = 4.03 R/D + 0.88 T -11.16 for MFA. Measured growth rates ranged from negative (-8% d -1 ) to 20% d -1 . Water temperature and larval R/D explained 37 to 39% of the variability in the observed growth rate. The models are applicable over temperatures ranging from 2.5 to 9.5°C and can be used to determine short-term growth rates of cod larvae collected from both the laboratory and field.

Beginning 2, 19, and 30 d after hatching, larvae of sand lance Arnmodytes americanus were reared for 1 or 2 wk between 2 and 9 "C in the absence of food and at nominal feeding levels of 200 to 1,000 rotifers 1-' (0.16 to 0.80 cal I-'). Mortality of all age groups was unaffected by temperature. The mean daily instantaneous mortality coefficient of newly hatched larvae was 0.01 to Day 16 and was unaffected by feeding level. Mean daily instantaneous mortality coefficients of older larvae ranged from 0.2 to 0.02 and decreased with increasing feeding level. Growth rate and RNA-DNA ratio increased with increasing feeding level. A direct linear relation observed between RNA-DNA ratio and growth rate was improved by adding temperature as a second independent variable. The relation between RNA-DNA ratio, temperature, and larval growth rate was insensitive to either larval size (protein content) or age.

Vital statistics and embryo and larval viability were determined for winter flounder Pseudopleuronectes americanus spawning in Narragansett Bay, Rhode Island, USA, over the course of the spawning season. Fish approaching spawning condition were collected throughout the spawning season and hand-stripped in the laboratory. Larvae were reared through the first month of life. Female size affected most of the reproductive parameters examined, including both absolute and relative measures of total reproductive output (reproductive rate and gonadosomatic index), e g g size, fecundity, and viability. Spawning time was found to affect e g g size, fecundity, and viability, but not reproductive rate or gonadosomatic index. Egg size increased with increasing female size and decreased as the spawning season progressed. Spawning time and female size explained 61 O/ O of the observed variability in egg size among females. Female size explained 95 % of the variability in reproductive rate and 90 % of the variability in fecundity. Female size and spawning time combined explained 9 4 % of the variability in fecundity. The effects of female size and spawning time on both fertility and hatch rate were non-additive. Embryos produced earlier in the spawning season appeared to have a survival advantage over those produced later in the spawning season. Embryos produced by small, latespawning fish appeared to be at a pronounced disadvantage.

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Ammodytes americanus adults were captured and transported to the laboratory and spawned. Eggs and larvae were successfully incubated at 2 , 4 , 7 and 10 'C. Speclfic growth rates in dry wt per day were 2.4 % at 2 "C, 3.23 % at 4 ' C . 4.75 % at ? 'C and 5.62 % at 10 "C. This was the first successful attempt to spawn sand lance in the laboratory and to rear the larvae through metamorphosis. The early life history of this fish can be completed under controlled laboratory conditions.