Interannual differences in hatching times and growth rates of pelagic juvenile cod in newfoundland waters

摘要

Year-by-year differences in age, hatching period, growth rate, and estimated size at settlement of pelagic juvenile cod were examined for the northern cod stock (NAFO 2J3KL) over a 6-year period, 1992-1997. Cod ranged in length from 24 to 70 mm TL and in age from 41 to 99 days. Mean hatching times varied by 7 weeks among years, ranging from June to August. Mean annual growth rates ranged from 0.52 to 0.62 mm per day among years, and wee significantly different (p=0.0018). Hatching occurred significantly later when water temperatures were colder,indicating that spawning was delayed during years of cold water temperatures and extensive ice cover. However, over the 6 years there was no general relationship between growth rates and ambient water temperatures experienced by larvae and pelagic juveniles. For example, lower growth rates in 1994 and 1996 were associated with high ambient water temperatures. Length of pelagic juvenile cod on common dates in the autumn varied among years. and was primarily a function of age, not growth rate. The largest year-class (1994) coincided with the earliest spawning, low growth rates, a large size at settlement, and seasonally warm water temperatures.