Intraspecific variation in the life history tactics of Atlantic herring (Clupea harengus L.) stocks

Abstract

Annual and lifetime reproductive outputs were calculated for individual female Atlantic herring (Clupea harengus L.) from nine stocks. Reproductive outputs were related to reproductive lifespan, maturation, growth and mean environmental temperature. Herring from cooler environments exhibited lower annual reproductive outputs but had longer reproductive lifespans than those from warmer environments. Although annual reproductive output increased with increasing temperature there was a corresponding decrease in reproductive lifespan. As a result, individual lifetime reproductive output did not change appreciably with temperature. Low annual reproductive output was associated with late maturity and slow post-maturational growth towards a large maximum size. High annual reproductive output was associated with early maturity and rapid postmaturational growth towards a smaller maximum size. These intraspecific differences in reproductive tactics may be influenced by phenotypic and genotypic factors. For Atlantic herring it was concluded that phenotypic influences were dominant, and had provided the stocks with an adaptive flexibility free from the constraints imposed by the slower process of genetic change.