Natal Homing and Connectivity in Atlantic Bluefin Tuna Populations

Abstract

Atlantic bluefin tuna populations are in steep decline, and an improved understanding of connectivity between individuals from eastern (Mediterranean Sea) and western (Gulf of Mexico) spawning areas is needed to manage remaining fisheries. Chemical signatures in the otoliths of yearlings from regional nurseries were distinct and served as natural tags to assess natal homing and mixing. Adults showed high rates of natal homing to both eastern and western spawning areas. Trans-Atlantic movement (east to west) was significant and size-dependent, with individuals of Mediterranean origin mixing with the western population in the U.S. Atlantic. The largest (oldest) bluefin tuna collected near the northern extent of their range in North American waters were almost exclusively of western origin, indicating that this region represents critical habitat for the western population.

Spatio-temporal population structuring and genetic diversity retention in depleted Atlantic Bluefin tuna of the Mediterranean Sea

“…Nonetheless, tagging experiments and fishery data analyses have unraveled an unexpected and complex interplay of ecological, behavioral, and reproductive factors that could affect the spatial and temporal population dynamics at the large scale (11,16). Microchemical signatures in otoliths of yearlings (i.e., young-of-the-year) unequivocally identified two main spawning areas [i.e., the Mediterranean Sea for the Eastern Atlantic population, the Gulf of Mexico for the Western Atlantic population (13)]. Because of high rates of natal homing of spawning adults to their native areas (95.8% for the Mediterranean Sea and 99.3% for the Gulf of Mexico) and limited and more complex movements in sexually mature ABFTs (11,17), the two populations show significant genetic divergence at both microsatellite (12) and mtDNA (18) loci.…”

“…The assessment of population dynamics, environmentally driven changes, and levels of exploitation in large pelagic fish is crucial for both stock management and conservation of marine ecosystems dominated by these oceanic top predators (6). Although fisheries still remain the chief source of data for assessing spatiotemporal population dynamics of these fish (7-10), whenever possible, their findings should be compared with those of fishery-independent approaches, such as genetic, electronic, and microchemical tagging experiments (11)(12)(13), to have more accurate data on the key features of population dynamics, such as spawning and migrations (10).…”

Sources, factors, mechanisms and possible solutions to pollutants in marine ecosystems

“…Top pelagic predators such as bluefin tuna, Thunnus thynnus, are often found in the Mediterranean Sea, Black Sea, Atlantic Ocean, and Pacific Ocean, but they have undergone a substantial decline (Farley and Davis, 1998;Fromentin and Powers, 2005;Carlsson et al, 2007;Rooker et al, 2008;Yamada et al, 2009;Kimura et al, 2010;Kitagawa et al, 2010;Riccioni et al, 2010;Teo and Block, 2010;Muhling et al, 2011a;MacKenzie and Mariani, 2012). Atlantic bluefin tuna (ABFT) is a highly migratory species that feeds in cold waters in North Atlantic and migrates to tropical seas to spawn (Muhling et al, 2011b) The reason for such a decline is for the most part commercial overfishing, because bluefin tuna is a highly prized fish and it is the favorite one for sushi and sashimi in Japan and, to some extent, also in other countries such as USA, EU and Russia (Bestor, 2000;Hutchings, 2000;Teo and Block, 2010).…”

“…Unfortunately, the substantially increasing demand of fish proteins for an increasing world's populations is being met by a combination of industrialscale commercial fishing, various netting techniques, as well as illegal and unregulated or unreported fishing (Table 2; Rotschild et al, 1994;Pauly and Christensen, 1995;Tegner and Dayton, 1999;Jackson et al, 2001;Burkhardt-Holm et al, 2002;Daskalov, 2002;Pauly et al, 2002;Platt et al, 2003;Bascompte et al, 2005;Block et al, 2005;Fromentin and Powers, 2005;Dulvy et al, 2006;Rooker et al, 2008;Srinivasan et al, 2010).…”

“…• Overfishing depletes ecosystems and has led to a global decline in fish catches (Jackson et al, 2001;Block et al, 2005;Fromentin and Powers, 2005;Dulvy et al, 2006;Rooker et al, 2008;Srinivasan et al, 2010).…”