The occurrence of skipped spawning and its importance for population dynamics in Northeast Arctic gadoids

The life history strategies of individual fish determine their growth potential and reproductive output. Thus, the life history strategy determines the stock?s dynamics and the potential yield that it can sustain. Life history traits directly affecting th e schedules of growth, survival, and reproduction, and are influenced both by fishing, which changes the population?s demography, and external forcing from the environment. With exploitation over a longer period of time, the fishery also exerts selective pressures that can lead to evolutionary changes. This project will investigate the impact of skipped spawning on Northeast Arctic cod and haddock populations. The still largely overlooked phenomenon of skipped spawning, whereby mature fish skip one or mor e of their spawning opportunities, might exert similar influences on dynamics and productivity of exploited fish stocks as caused by changes in age-at-maturity. Quantifying skipped spawning will allow the development of more realistic population dynamic m odels that underpin management. We will first establish phenotypic relationships between skipped spawning and age, condition, and environment in recently collected data, backed up by theory, life history models, and otolith analyses. From the otolith anal yses we can see if skipping is solely related to insufficient energy reserves or if, as predicted by models, can also be caused by an increased investment in growth. Second, we will document the historic occurrence of skipped spawning in these populations . Third, using models that incorporate and simulate the empirical results, we will evaluate the importance for management of skipped spawning and other life history changes that affect stock reproductive potential, egg production, and ultimately recruitme nt. Recent life history models indicate that highly exploited fish stocks have undergone evolutionary change due to the selective mortality.