Yellowfin tuna:
The tuna biology
The yellowfin tuna (Thunnus albacares) is one of the largest tuna species, reaching weights over 180 kg (400 lb) and full lengths of more than 2 m (6.5 ft). They live in pelagic waters, in the tropical and subtropical oceans of the planet.
Their body colour goes from a very dark metallic blue in their backs, to a silver on the belly, with about 20 lights coloured, irregular, vertical lines along the body. Their anal fin, second dorsal fin, and the finlets between those fins and the tail are very bright yellow, which give them their common name. In mature specimens, both the anal and second dorsal fin grow exceptionally long, reaching as far back as their tail.
Source: Al McGlashan / Wikimedia Commons. License: CC by Attribution-NonCommercial
Nutritional and economic importance
Fishing represents the main protein source for 3.2 billion people in the world (FAO, 2018). The yellowfin tuna is the second most fished member of the family of the tunas, and this family is the most exploited group of commercial fish species worldwide (Pecoraro et al., 2016). In 2018, it was estimated that the catches of yellowfin tuna had an end value of 15.8 Billion USD (Pew Charitable Trusts). The largest amount of tuna caught in the world comes from the Pacific Ocean (Bayliff et al., 2004).
Ecological importance and current status
Yellowfin tunas are a one of the few “warm-blooded” fish, which enables them to keep their muscles warm, making them extremely fast swimmers. This and a very keen sight make them a formidable predator who feeds rather indiscriminately on fish species like Mahi-mahi, pilchard, anchovy, flying fish, mackerel, lancetfish, and other tunas; as well as on other prey items like cuttlefish, squids, octopodes, shrimps, lobsters, and crabs. Their feeding tends to occur in surface waters during daylight and they compete with other large fish and marine mammals for food.
Due to its role as a top line predator, yellowfin tuna is critical in the regulation of species that could become a problem if they are not kept in check. Removing top predators from the marine ecosystem can cause trophic cascades (a domino effect whereby species throughout the trophic layers are affected), destabilising the entire ecosystem (Worm et al., 2009; Collie et al., 2016).
Public fishery statistics from large-scale fisheries indicate that sustainable commercial populations have been reduced from 90% in 1974 to 66% in 2015 (FAO, 2018). Based on some of these statistics, Worm et al., (2006) estimated that marine commercial populations could disappear by 2048 if no conservation actions were taken. However, Pauly and Zeller (2016) carried out a reconstruction including relevant values from artisanal fisheries and suggested that the number of commercial populations may have declined further.
Some studies (Grewe et al., 2015; Barth et al., 2017; Percoraro et al., 2018) have reported that populations of yellowfin tuna from different oceans have fragmented due to various factors including fisheries. This fragmentation constitutes a threat to the species and its habitat, as it makes them more sensitive to extinction.
History of the project
The project started in 2014 in Súa, a small fishing town in the north of Ecuador as part of the research of two students from Colombia and Ecuador. After working in a cooperative effort with the local community that led us to understand the impact of fisheries in the populations of migrant cetaceans, we centred our attention on this species whose conservation is often overlooked.
During these years we have studied the genetic connectivity, population structure, ecology, and threats yellow fin tuna faces in Galápagos, and the coastal waters of Ecuador and Mexico. Our work requires collecting samples of muscle, gonads, and otoliths from the fish, during seasonal trips to fishing ports and on-board fishing vessels in different areas.
What we pursue and have achieved.
Tunas have been historically disregarded as key components of healthy environments and critical pillars of the economy and culture of coastal communities. Our aim is to understand the biology and ecology of this species, producing as much useful, applicable knowledge as possible, to facilitate the development of efficient conservation and management policies that ensure its survival for the sake of the ecosystems and the peoples that depend on them.
Our work has rendered its first scientific findings, resulting not only in papers in revision, but also in important collaborations with scientists from different countries and institutions on the Pacific basin. More importantly, it has helped us to cement a close relation with the local artisanal fishing communities, who understand that conserving this precious species means protecting they own livelihoods and the future of their communities.
Our next steps
We are currently expanding both the scope and the area of coverage of our study. Starting in August 2021 We will begin collaborations with scientists in Costa Rica, Perú and Chile to replicate our study and complement our findings in Galapagos, Ecuador and Mexico. Likewise, we will start a telemetry study to determine short- and long-range migration patterns of this magnificent fish. For this, we will tag a few individuals[FR1] in the Galápagos Islands, with radio emitters that can be detected by the array of receivers around the islands and along the Cocos-Galápagos corridor.
During these years, our work has heavily relied on funding obtained through grants and scholarships, but as the scale of the project grows, the need for funding increases exponentially. That is why we try to share this insight on the crucial importance tunas have in the health of the marine ecosystems and how valuable they are for the artisanal fishing communities with you and as many people as possible and kindly ask anyone to generously donate to the “Great Fishes of the Eastern Pacific” Project and help us continue working towards the conservation of the yellowfin tuna. The donations can be in form of funds that can be destined to cover analyses, equipment, rent of fishing fiberglass boats, and other logistics; but also, sponsors can buy acoustic tags (for short-range migrations) or satellite marks (for long-range migrations) directly from the provider and have them sent to the Project.
