Retrospective analysis of the influence of environmental drivers on commercial stocks and fishing opportunities in the Irish Sea

Irish Sea fisheries have undergone considerable change in recent years following the decline of commercially important finfish stocks and their slow response to management’s recovery plans. In 2015 the fishing industry called for a holistic exploration into the impact of environmental change and food web effects to identify the drivers underpinning stock dynamics. In this study we identify correlations between large scale climatic indicators, temperature, primary and secondary productivity, and fish recruitment in the Irish Sea and incorporate them into an Ecopath with Ecosim food web model co-created by scientists and fishers. Negative correlations were found between the North Atlantic Oscillation winter index (NAOw) and large zooplankton abundance, and between the Atlantic Multidecadal Oscillation (AMO) and the recruitment of cod (Gadus morhua) and whiting (Merlangius merlangus). Using correlation analyses to direct the addition of environmental drivers to the Irish Sea ecosystem model improved the models fit against observed biomass and catch data and revealed the indirect impacts of environmental change as mitigated through trophic interactions. Model simulations suggest that historic environmental change suppressed the overall production of commercial finfish, limiting opportunities for the fishing industry, whilst also dampening the rate of stock recovery despite marked reductions in fishing effort. These results suggest that failure to account for ecosystem information may lead to misconceived expectations and flawed fisheries management, therefore there is a need operationalise ecosystem information through management procedures to support fisheries advice.