Growth and Maturation of Southwest Nova Scotia Atlantic Herring (Clupea harengus harengus)

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Abstract
Juvenile and adult growth rates, and the maturation schedule, for the southwest Nova Scotia herring stock (NAFO SA 4WX) were investigated over the period 1968–78. The variance in juvenile (age 2) summer growth is not well accounted for by initial weight, juvenile population abundance, and temperature unless a discontinuity in growth pattern starting in 1970 is accounted for. Length at maturity and at recruitment to the adult schools appears to be inversely related to the population abundance experienced during juvenile growth. However, at very low juvenile population size, maturation appears to be inhibited. Somatic growth rate and its year-to-year variability decreases close to an order of magnitude with the onset of maturation. Because of this decrease with age and the radical shifts in age, composition with time, population growth rate fluctuates markedly. Because high population abundance parallels downward shifts in age composition, there is a clear, positive relationship between population growth rate and population abundance. There is a dome-shaped relationship between cohort somatic growth rate and cohort size at intermediate ages, suggesting that over a broad range in population size, adult growth rate is not density-dependent. This growth response is interpreted in relation to planktivorous feeding in a patchy environment. Strong year-class strength variability coupled with a marked decline in somatic growth rate with age results in non-steady state population production. When the age composition is biased towards older ages, catch (defined by F0.1 guidelines) exceeds population production resulting in rapid stock declines. The growth characteristics of herring are discussed in relation to the literature and "analytical" yield models.Key words: Atlantic herring, growth, maturation, production

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