Investigation of the temporal effects of spawning season and maternal and paternal differences on egg quality in Atlantic codGadus morhuaL. broodstock

Abstract

A better understanding of the parameters a¡ecting egg quality and larval survival is of importance for continued development of cod broodstock and e⁄cient husbandry practices. Decision tree analysis (DTA) was applied to analyse 3 years of egg quality data in an e¡ort to extract the most important variables (i.e. predictors) in explaining di¡erences in egg quality. The e¡ect of three predictors (spawning time, maternal and paternal di¡erences) has been studied on early cleavage pattern parameters, egg diameters, fertilization and hatching rates and has shown that females are the dominant variable and that time has a limited and inconsistent impact on the data.When using maternal, paternal di¡erences and batch number (instead of spawning time) as predictors, the results con¢rm that no particular relationship is found between batch order (i.e. order in time) and egg quality. Moreover, batches with a higher egg quality show a consistency in the parameters assessed (i.e. batches with higher rates of normality in any parameter tend to be normal for other parameters). This is con¢rmed by the signi¢cant correlations found between cleavage parameters. Our results highlight that spawning time is of less importance than female parent contribution in ensuring high rates of fertilization and larval hatch, and maximizing general egg quality.Maximum and minimum values are provided between brackets. Length and mass were recorded at paired mating. N, total number of spawners considered, n, total number of ¢sh weighed and measured.Data were transformed using arcsin square root transformation. Numbers underlined indicate a signi¢cant correlation (probability levels for statistical signi¢cance are Bonferroni-adjusted for multiple comparisons). Egg £oat, % £oating eggs (% live eggs), Fert.

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