Harvesting geo-spatial data on coastal fish assemblages through coordinated citizen science

In response to repeated complaints from recreational and commercial coastal fishermen about declining fishing opportunities in inner Danish waters, focus was directed to inshore fish stocks. However, without data targeting inshore areas, it was not possible to investigate potential changes in fish distribution or abundances, or their causes.

As a first step, a voluntary catch registration system was initiated in 2002, in collaboration with locally organized recreational fishermen. Using citizen science as a methodology, scientists and the fishermen developed a protocol for data collection, which the fishermen then implemented. The aim was to establish regular monitoring of fish catches from gill net and fyke net fisheries in coastal waters around Denmark in order to provide data that could inform management.

After three years, during which time recreational fishermen could use their own gear and fish where they normally fished, the data was evaluated. As a result, the fishing method was switched in 2005 to fixed gears and fixed positions, to enable comparison between areas, years and season. The project has been very successful in recruiting highly motivated fishermen, who register their entire catch regularly.

The time-series of data spans more than a decade and covers over 16,000 instances of fishing. The data from this project are now being used to create coastal fish indicators for managers to assess environmental status at a regional scale. Here we present an analysis of a subset of the data on one species, the European flounder (Platichthys flesus), to illustrate how the spatial and seasonal coverage can be utilized further for investigation of coastal ecosystems and to inform management.