Fishers' knowledge as an indicator of spatial and temporal trends in abundance of commercial fish species: Megrim (Lepidorhombus whiffiagonis) in the northern North Sea

The need for alternative strategies to assist in the monitoring and sustainable management of many commercially important fish stocks is widely recognized. In recent years, greater utilization of fishers' knowledge has been advocated as a potentially valuable source of ecological data in the assessment and management process. In this study changes in the distribution and relative abundance of common megrim Lepidorhombus whiffiagonis in the North Sea were investigated by comparing three data sources: fishers' knowledge collected through a structured questionnaire; a vessel's haul-by-haul catch data from the personal diaries of a single skipper over a 10-year time-series, and catch rates from fishery-independent surveys (IBTS Q1 and Q3). Trends in the distribution and relative abundance of megrim were broadly comparable between the three data sources. The results of the study indicate that, in the northern North Sea, fishers' knowledge and catch data can provide valid data sources which can contribute to the assessment and management process. A structured approach consisting of a formal agreement, full transparency and commitment between all stakeholders is needed to provide and utilize the necessary data required to provide the most effective and inclusive approach to resource management.