Lack of genetic differentiation in yellowfin tuna has conservation implications in the Eastern Pacific Ocean

Abstract

Yellowfin tuna, Thunnus albacares, is an important global fishery and of particular importance in the Eastern Pacific Ocean (EPO). According to the 2019 Inter-American Tropical Tuna Commission (IATTC) assessment, yellowfin tuna within the EPO is a single stock, and is being managed as one stock. However, previous studies indicate site fidelity, or limited home ranges, of yellowfin tuna which suggests the potential for multiple yellowfin tuna stocks within the EPO, which was supported by a population genetic study using microsatellites. If numerous stocks are present, management at the wrong spatial scales could cause the loss of minor yellowfin tuna populations in the EPO. In this study we used double digestion RADseq to assess the genetic structure of yellowfin tuna in the EPO. A total of 164 yellowfin tuna from Cabo San Lucas, México, and the Galápagos Islands and Santa Elena, Ecuador, were analysed using 18,011 single nucleotide polymorphisms. Limited genetic differentiation (FST = 0.00058–0.00328) observed among the sampling locations (México, Ecuador, Peru, and within Ecuador) is consistent with presence of a single yellowfin tuna population within the EPO. Our findings are consistent with the IATTC assessment and provide further evidence of the need for transboundary cooperation for the successful management of this important fishery throughout the EPO.

Acute thermal stress increased enzyme activity and muscle energy distribution of yellowfin tuna

“…As a result, tuna has become an important source of income for many countries, including Japan, the European Union, and the United States [ 9 ]. However, overfishing is one of the biggest threats it will face, with numbers in decline and the development of yellowfin tuna in captivity [ 10 ]. Similarly, rising water temperatures due to human-caused climate change may also reduce the oxygen supply of Marine organisms such as tuna [ 11 ].…”

Elevated Mercury Concentrations and Isotope Signatures (N, C, Hg) in Yellowfin Tuna (Thunnus albacares) from the Galápagos Marine Reserve and Waters off Ecuador

“…These studies support research using satellite marks that indicate yellowfin tuna are restricted to an area with a radius of approximately 1852 km (Schaefer & Fuller, 2022; Schaefer et al, 2014). Although we found a difference between Hg isotopic signatures between both locations, which suggests a distinction of foraging sites, it is possible that the sampled individuals might have inhabited the entire region, because we found no differences in THg concentration between tuna from the Ecuadorian mainland coast or the Galápagos Marine Reserve and because the areas where the fish were caught are only separated by approximately 1500 km (Muñoz‐Abril et al, 2022). Likewise, as previously stated, the favorable oceanographic conditions (i.e., upwellings providing food) would allow individuals to have access to stable resources and permanently inhabit this area.…”

Movement and vertical habitat use of yellowfin tuna Thunnus albacares in a vertically compressed habitat: the Galápagos Marine Reserve

“…With an average 13.9 km day −1 covered for all tags combined, a yellowfin tuna could have moved to mainland Ecuador in just over 2 months, but no such long‐distance movements were recorded, similar to results from other regions (Nimit et al, 2020; Richardson et al, 2018; Schaefer et al, 2011). While genetic studies suggest a single stock exists in the Eastern Tropical Pacific (Muñoz‐Abril et al, 2022), the longer time scale and the few migrants required for gene exchange mean that contemporary tracking results may be more applicable for fisheries management. As such, stocks may be vulnerable to regional overexploitation and environmental change.…”

“…While genetic studies suggest a single stock exists in the Eastern Tropical Pacific (Muñoz-Abril et al, 2022), the longer time scale and the few migrants required for gene exchange mean that contemporary tracking results may be more applicable for fisheries management. As such, stocks may be vulnerable to regional overexploitation and environmental change.…”