Demonstrations of maternal effects of Atlantic cod: combining the use of unique mesocosm and novel molecular techniques - a new EU-project

One of the effects of fishing is a reduction in average age and size in exploited fish stocks, leading to an increasing proportion of recruit spawners in the stock. Current management practice assumes equal viability of offspring from first time spawners and from repeat spawners, despite the fact that that first time spawners often produce smaller eggs than older spawners. The aim of this EU-project is to follow offspring from families of first time spawning and older cod, reared under identical and semi-natural conditions in marine enclosures (mesocosms). The parental origin of the larvae is identified using microsatellite DNA methodology. The advantage of this approach, compared to traditional laboratory rearing, is that rearing conditions are close to natural conditions, and all larvae are reared in the same environment. This eliminates the tank-to-tank variability often observed in traditional rearing experiments. The fish are reared from hatching, through the larval and juvenile stages, until sexual maturity. Growth rates, survival and nutritional condition will be measured using methods such as RNA/DNA ratio and otolith micro increment analysis. The results will be related to parental origin and quality measures of the eggs. It is intended to incorporate the results into management models for improvement of fishery management strategies. In this paper we will focus on a description of the projec