A study published in the scientific journal Frontiers in Marine Science identified genetically different populations of mahi mahi in the Tropical Eastern Pacific Ocean (TEP), suggesting at least three independent genetic groups are present in the region. This has implications for the development of tailored and coordinated fisheries management plans for the mahi mahi populations in the region.
The study was conducted by scientists from the Universidad Nacional Autónoma de México (UNAM), the Centro Interdisciplinario de Ciencias Marinas (CICIMAR) of the Instituto Politécnico Nacional (IPN) of Mexico, the Instituto Público de Investigación de Acuicultura y Pesca (IPIAP) of Ecuador, the Instituto del Mar del Perú (IMARPE), and the Instituto Costarricense de Pesca y Acuicultura (INCOPESCA).
The mahi-mahi (Coryphaena hippurus), also known as dorado or mahi-mahi, is a highly migratory fishery resource inhabiting tropical and subtropical waters worldwide. In the TEP, its distribution ranges from California (United States) to Antofagasta (Chile). It is part of artisanal fisheries using longlines and gillnets, as well as recreational fishing. It is also incidentally caught by industrial tuna purse-seine and longline fisheries.
According to the Food and Agriculture Organization of the United Nations (FAO), during the period 2010 – 2021, Peru and Ecuador together contributed more than 56% of the total global mahi-mahi catches, totaling more than 715,000 tons. Despite significant advances in fishery management, key elements are still needed to develop a comprehensive catch strategy ensuring fishery sustainability, such as explicit management objectives, biological reference points, and catch control rules.
One of the main limitations facing countries in achieving effective mahi-mahi management is the uncertainty about the population’s genetic structure. Being a resource distributed in international waters and within the jurisdictions of TEP countries, failure to objectively define the appropriate unit for fishery management complicates understanding the level of collaboration required among different countries to ensure sustainable management.
Therefore, to reduce these uncertainties, researchers from Ecuador, Peru, Costa Rica, and Mexico conducted this investigation, which involved collecting mahi-mahi samples from different areas in the TEP. These samples were processed and analyzed using genetic techniques, yielding the following findings:
- At least three genetic groups were identified: one in the northern distribution zone of mahi mahi, another in the southern zone, and a third in international waters (oceanic), mainly operated by the tuna fleet.
- A greater gene flow connection was observed in tropical latitudes (Central America, Peru, and Ecuador), where the species is highly abundant for both juveniles and adult individuals. In contrast, gene flow barriers were observed between Mexico and Central America.
- The distribution range of these populations may expand or contract according to oceanographic conditions. It has been observed that as sea surface temperature increases, the location of mahi mahi populations at distribution limits expands, while populations decrease as sea temperature decreases, causing expansion-contraction cycles that leave a genetic fingerprint on these populations.
Based on these results, researchers recommend developing management strategies to preserve the viability of mahi mahi populations in the TEP, considering that their distribution range depends on environmental factors and is also highly impacted by fisheries. Likewise, considering at least three genetic groups (oceanic, north, and south) in a vast and complex geographic area represents the first step toward implementing a comprehensive management and conservation plan for the species.
This research was supported by the Walton Family Foundation (WFF) and the Global Sustainable Supply Chains for Marine Commodities (GMC) project. GMC is an interregional initiative implemented by the Fisheries and Planning Ministries and Offices of Costa Rica, Ecuador, Indonesia, and the Philippines, with technical support from the United Nations Development Programme (UNDP), facilitated by the Sustainable Fisheries Partnership (SFP), and supported by the Global Environment Facility (GEF). Sample collection was carried out with the support of members of the Regional Mahi Producers and Processors Committee (COREMAHI).
The study is available at the following link:
https://www.frontiersin.org/articles/10.3389/fmars.2023.1294509/full