The catch rate is a poor indicator of the health of the fishery in the lakes.

Fishing industry collapses can be difficult to forecast and prevent due to hyperstability, a phenomenon in which catch rates remain high even as fish abundance declines. In a recent Canadian Journal of Fisheries and Aquatic Sciences In the study, the researchers conducted a lake-wide experiment to reveal the causes of hyperstability in recreational fishing. Fish habitat preferences were found to make them vulnerable to overexploitation.

Chris Solomon, an aquatic ecologist at the Cary Institute for Ecosystem Studies, authored the article. He explains: “The few previous studies on hyperstability in recreational fisheries, such as commercial fisheries, have been based on observational data. Using an experimental approach, we were able to reveal the underlying cause of a problem that has bothered managers fishing “.

By manipulating the abundance of largemouth bass in a northern Wisconsin lake, Solomon and his colleagues conducted the first experimental hyperstability test. Within three months, the research team changed the abundance of bass in Camp Lake weekly, from more than 350 to just 25 fish. Electro-fishing was used to temporarily move animals from the main lake basin to an isolated side basin.

Once a week, three fishermen fished for two hours in the morning and two hours in the afternoon, boating along the shore. They targeted the shoreline, preferred bass habitat, and recorded the location of each hooked fish. When their catch rates were compared to the known abundance of sea bass in the lake each week, the team documented that the angler’s success remained high until only a few fish remained.

Mechanisms believed to cause hyperstability are habitat aggregation and stress classification. Habitat aggregation refers to the tendency of fish species to cluster in areas with preferred habitat characteristics such as downed trees or aquatic vegetation. Effort rating refers to the skill of the angler, with less skilled anglers advancing as the fish decline, resulting in high catch rates for the remaining expert anglers.

Lead author Colin Dassow, Ph.D. University of Notre Dame candidate explains: “Previous studies have linked hyperstability with effort rating. Using a fixed set of fishermen, we excluded this variable. Habitat aggregation was the engine of the collapse of hyperstability at Camp Lake Hyperstability increases the risk of fishing collapse because fishermen receive no sign that fish are in trouble until it is too late. “

Solomon explains: “We found that hyperstability can occur simply because fishermen know where the fish gather, even at times of the year when the fish are not densely grouped to spawn. That is concerning because most fish species have preferences of habitat, suggesting that many recreational fisheries may be susceptible to hyperstability. “

According to the authors of the article, limiting the effort of the fisherman is the main way to protect fish that are vulnerable due to habitat aggregation. This could take the form of shortening the fishing season, lowering catch limits, or prohibiting fishing when and where fish gather to spawn. These are not always popular policies, but could be essential to conserve fish stocks and quality fishing opportunities.

“Protecting the economic, social and ecological benefits of healthy fisheries requires closer monitoring,” says Dassow. “Unfortunately, the data reported by fishermen is patchy and the data collected by investigators and state agencies is too expensive to scale. Both types of data inform our understanding of how the system as a whole is working, but we do not have enough of any kind. “

Solomon concludes: “It is important for fishermen to understand that what comes out of the water is not always representative of what is below the surface. Even if the fish are biting, this does not mean that there are many of them. Fishermen, fisheries managers And other stakeholders must work together to advocate for better monitoring and effort sensitive limits if we want to maintain good fishing opportunities now and in the future. ”