Even small-scale fisheries can destroy marine ecosystems

For thousands of years, fisheries have been a source of subsistence for humans, and they remain so today. And while the impact of small-scale fisheries on ocean life has often been considered negligible, a new study in Nature Communications suggests otherwise.

Small-scale fisheries might really have a minor impact when it comes to local effects, yet when the global scale is considered small-scale fisheries catch amounts to millions of tons every year, often in places of high biodiversity, the authors observe.

They suggest that we need to direct more attention to how those small-scale fisheries are managed if these hotspots of biodiversity are to continue sustaining thriving local ecosystems. Regulations are in place to constrain catch sizes or protect particular fish species. Yet the researchers argue that a more nuanced approach is required if we want small-scale fisheries to remain sustainable.

There are many ways to go about fishing: from choosing its timing and frequency to selecting places and equipment. Some of the choices are far more sustainable than others. In a featured case, from a decade-long study carried out in the Wakatobi National Park in Indonesia, researchers identified over 500 species of fish caught, many of them even before they had the chance to reproduce.

Threats also come from artisanal fish fences, which were previously considered as an environmentally benign way to catch fish. Scientists have revealed, however, that seagrass and corals are often destroyed during installation, while fences themselves are built using large quantities of mangrove wood, which together leads to ecosystem degradation both on land and in water.

Moreover, large catchment areas previously available to all fishermen become unofficially privatized as a result of the fences, which can lead to conflicts and greater ecosystem degradation in nearby areas. Another drawback is great quantities of little-regulated bycatch about which fence owners have little incentive to worry.

Dr. Richard Unsworth, a marine ecosystem researcher at Swansea University and a co-author of the study, emphasizes the global nature of the phenomenon. “These fences which are common across the Pacific, Atlantic and Indian oceans are so large they can be seen from space using Google Earth,” he says. “It’s not surprising that these fisheries are having a disastrous impact on tropical marine ecosystems such as seagrass meadows, mangroves, and coral reefs.”

Troubled by such outcomes, the researchers argue that to really understand the impacts of various fishing techniques, we need to bring together knowledge from both social and natural sciences. As one possible improvement, the considered impacts should be estimated based on the relative compositions of different species within an overall catch. That would allow for a better understanding of the actual impacts of fishing on ecosystem dynamics.

Assessments should also include how fisheries directly influence nature and communities locally; for example, whether they are linked to conflicts or lead to inequalities.

Only by considering all those factors can we make conclusions on how sustainable small-scale fisheries are. While the researchers argue for better regulating the use of fish fences, they also argue against bans that don’t consider local peculiarities because that can often lead to immediate ecosystem degradation in nearby and less regulated areas.

Importantly, incorporating more factors into decision-making can actually be beneficial to local fishermen. For example, greater care for seagrass meadows, mangroves, and coral reefs can improve ecosystem resilience and boost the productivity of small-scale fisheries. That can help ensure local fishing businesses are not only profitable but also sustainable in the long term.