Maternal and seasonal differences in egg sizes and spawning activity of northwest Atlantic haddock (Melanogrammus aeglefinus) in relation to body size and condition

Egg and larval production of 22 captive spawning pairs of northwest Atlantic haddock (Melanogrammus aeglefinus) were monitored. Females spawned an average of nine egg batches (range 3–16) with a mean batch fecundity of 60 000 eggs and mean total fecundity of 535 000 eggs. Mean spawning duration was 37 days with a mean batch interval of 5.4 days. In multiple linear regression, male Fulton's condition factor (range 1.10–1.55) and mean batch interval explained 56% of variation in fertilization rate (33% and 23%, respectively). Seasonal composite egg diameter spanned 1.37–1.53 mm among females. Mean egg diameter within females declined seasonally by an average of 10.4% (37% by volume). Females produced 46 larvae per gram body weight. Body weight was the single best predictor of fecundity (r2 = 0.57), with Fulton's condition factor (range 1.04–1.76) explaining no significant additional variation over length or weight. Length and condition explained 39% of variation in seasonal composite egg diameter (22% and 17%, respectively) and body weight independently explained 32%. Sex-specific parental condition and body size acted through large egg size and elevated fertility to enhance reproductive output. Male spawning success was more sensitive than egg production to changes in condition.