Fish species around the world navigate complex ecosystems based on habitat conditions and life histories. Fish do not pay attention to national borders, swimming instead to areas that meet temperature, nutrient, oxygen and other needs. While marine species distribution follows environmental needs, these “transboundary species” present challenges to fisheries management — which primarily adheres to man-made international boundaries — and may be more abundant than we previously realized.
“I am Brazilian, which means that I’ve always needed a visa to go to another country. Marine fish do not need visas,” said Juliano Palacios-Abrantes, a Ph.D. candidate at the University of British Columbia Institute for the Oceans and Fisheries. Palacios-Abrantes is the lead author of a paper published today in Scientific Reports.
“What we found is that most commercial species cross international borders as they please, requiring countries to collaborate in the management of these species,” Palacios-Abrantes continued. The paper estimates there are 633 transboundary species – nearly double that of previous estimates.
“Our updated estimates underscore just how important transboundary species are to global fisheries,” said COS research associate Colette Wabnitz, a co-author on the study. “Sustainably and equitably managing transboundary species is fundamental to the sustainable and equitable management of global fisheries — their ‘divided’ ownership requires cooperation in governance.”
After analyzing geographic distributions of fish species and catch data from fisheries around the globe, the researchers found that transboundary species account for over 80% of total catch from national waters and more than three-quarters of global fishing revenue. Insights from the analysis emphasize the central role of shared species to global fisheries capture and economies as well as healthy food systems.
Warming waters and other climate change impacts will likely continue shifting species distributions in the ocean. Anticipating these shifts can promote the development of more equitable and climate-resilient fisheries management strategies and international treaties.
As global populations climb toward a projected nine billion people by 2050, climate-resilient fisheries will become increasingly important. “Blue foods” from the ocean provide protein and essential nutrients that can support growing populations and demands on food systems.
“The cooperative and adaptive management between two countries that share a valuable exploited species is likely to support the sustainable stewardship of the resource over the long term,” explains Wabnitz. These management measures may include collaborative regulations and management plans, shared transboundary marine protected areas, and increased data sharing. For example, the Pacific Salmon Treaty, an agreement established in 1985 between the United States and Canada, has explicitly acknowledged climate change and committed to supporting long-term monitoring and science-based management of Pacific salmon stocks. Through cooperative management, coastal nations could more effectively accommodate future climate change impacts while meeting food and nutritional needs.
These findings are part of ongoing efforts to increase equity and resilience in global fisheries. As the authors conclude, “identifying existing transboundary species is the first step towards joint management frameworks that are precautionary, strive for sustainability, and can be flexible to accommodate the uncertain future driven by climate change.”