Six blastomere morphology parameters indicative of cell development abnormalities, egg diameter, dry weight, total lipid, lipid classes and fatty acids were determined for egg batches collected daily from three Atlantic cod (Gadus morhua) broodstock groups over the course of one spawning season. Egg batches were incubated to hatch and each morphological and biochemical parameter was tested as a predictor of hatching success. Five of the six blastomere morphology parameters were significantly positively correlated with each other. Correlation coefficients among several fatty acid parameters were also significant but correlation coefficients among the various lipid classes were mostly not significant. No significant correlations were found between blastomere morphology and lipid class or fatty acid parameters. Egg dry weight was negatively correlated with cell clarity, %docosahexanoic acid (DHA), DHA:eicosapentaenoic acid, and Σ polyunsaturated fatty acids. Fertilization success was not significantly correlated with any of the morphology or biochemistry parameters. Within‐population variability in several morphological and fatty acid parameters was related to elapsed time since onset of first spawning. However, the occurrence of such relationships with elapsed time was highly variable and inconsistent among the three broodstocks, typically being significant for only one or two broodstocks but not all three. Mean hatching success rates were high (>75%) in all three broodstocks but hatching success was not significantly related to any of the morphological or biochemical parameters nor to elapsed time from onset of first spawning. The implications of these results are discussed in terms of the utility of the various morphology and biochemistry parameters as measures of egg quality in marine finfish hatcheries.

Spawning activity in two captive Atlantic cod broodstock groups previously captured from the wild stock fishery was monitored over three spawning seasons. Both groups spawned under ambient photoperiod (PP) in the first year, after which photomanipulation was applied to compress the PP cycle of one broodstock group, while the second group was maintained on natural PP. Increased total egg volumes, number of egg batches, total egg production, and duration of the spawning season were observed in both ambient PP and advanced PP groups in the second and third spawning seasons. Compared to ambient controls, the photoadvanced group commenced spawning earlier, had a longer spawning season, produced a lower total volume of eggs over the entire spawning season, and had lower mean daily batch volumes of eggs, and the eggs were of smaller mean diameter. Fertilization success was .90% in all years, increased in both groups in the first year after photomanipulation but declined to prior levels in the following year. No consistent difference in fertilization success was observed between advanced PP and ambient PP groups. Rates of cell development abnormalities were low (,10%) in both groups over the three spawning seasons. Abnormalities of cell symmetry and clarity increased in both ambient PP and advanced PP groups over the three spawning seasons. However, no consistent differences in rate of cell abnormalities were observed between advanced PP and ambient PP groups within years. We conclude that PP advancement is an effective technique to compress the time between successive spawning periods in Atlantic cod and does not negatively affect fertilization success or rates of cell developmental abnormalities. However, it has a negative effect on both volume and size of eggs produced.

We report on the proximate composition, lipid class, and fatty acid content of fertilized eggs during the course of one spawning season from two broodstocks of Atlantic cod Gadus morhua: One group was maintained under ambient photoperiod (PP), whereas for the second group the natural photoperiod cycle was compressed by approximately 4 months by PP advancement from ambient. We tested the hypothesis that PP compression, which reduces the time between successive spawning seasons and therefore reduces the time available for vitellogenesis and maturation, might also impair nutrient transfer to the eggs, causing reduced egg quality as measured by biochemical indices. Advanced PP eggs were significantly larger than ambient control eggs (absolute mean values for dry weight = 109.2 and 97.9 μg, respectively). Advanced PP eggs also had significantly greater mean total protein (60.0 versus 49.4 μg), mean total lipid (15.1 versus 9.7 μg), and greater mean values for several major lipid classes (hydrocarbons, triacylglycerols, sterols, diacylglycerols, and phospholipids) than ambient controls. Proportionally (percent of dry weight), mean total lipid, ash, triacylglycerols, total saturated fatty acids, and total polyunsaturated fatty acids, including total ω‐3, total ω‐6, docosahexaenoic acid, eicosapentaenoic acid, and arachidonic acid, were all significantly greater in eggs of the advanced PP group than in ambient controls. The latter contained proportionally more monounsaturated fatty acids. Mean dry weight of eggs declined over time from onset of first spawning in the ambient PP group but not in the advanced PP group, and none of the measured biochemical indices varied significantly over time from onset of first spawning in either PP group. We conclude that with the PP advancement technique used here, compression of time between successive spawnings by up to 4 months in Atlantic cod does not negatively affect biochemical indices of egg quality associated with normal development or survival performance.