Spawning Time and Egg Stage Duration in Northwest Atlantic Haddock (Melanogrammus aeglefinus) Stocks with Emphasis on Georges and Browns Bank

Abstract

Literature data was used to examine the hypothesis that variation in the spawning time, defined as the peak in egg abundance, of Northwest Atlantic haddock (Melanogrammus aeglefinus) stocks is explained by water temperature and to derive calibration curves relating incubation temperature to haddock egg stage duration. Spawning times occurred, on average, in March on Georges Bank, late April/early May on Browns Bank, and in June/July on the Grand Banks. Temperatures at peak spawning overlapped considerably but differed in terms of phase in the annual temperature cycle. Inter-annual variation in spawning time of Georges Bank haddock varied by 3 mo and was significantly correlated with water temperature. Browns Bank haddock spawning varied by only 1 mo and was not correlated with water temperature. Egg stage duration varied with incubation temperature. A power curve best described the relationship and was used to estimate the historical, annual variation in haddock egg stage duration which ranged from 10 to 20 d (mean = 16 d) on Georges Bank and from 10 to 30 d (mean = 18 d) on Browns Bank during 1946–80. Collectively, our analysis calls into question the generality of the assumption of constant spawning times for marine fish species and provides essential information for field measurement of haddock egg production rates, mortality, advection, and dispersal.