Seascape Genomics and Phylogeography of the Sailfish (Istiophorus platypterus).

Permeable phylogeographic barriers characterize the vast open ocean, boosting gene flow and counteracting population differentiation and speciation of widely distributed and migratory species. However, many widely distributed species consists of distinct populations throughout their distribution, evidencing that our understanding of how the marine environment triggers population and species divergence are insufficient. The sailfish is a circumtropical and highly migratory billfish that inhabits warm and productive areas. Despite its ecological and socioeconomic importance as a predator and fishery resource, the species is threatened by overfishing, requiring innovative approaches to improve their management and conservation status. Thus, we presented a novel high-quality reference genome for the species and applied a seascape genomics approach to understand how marine environmental features may promote local adaptation and how it affects gene flow between populations. We delimit two populations between the Atlantic and Indo-Western Pacific oceans and detect outlier loci correlated with sea surface temperature, salinity, oxygen, and chlorophyll concentrations. However, the most significant explanatory factor that explains the differences between populations was isolation by distance. Despite recent population drops, the sailfish populations are not inbred. For billfishes in general, genome-wide heterozygosity was found to be relatively low compared to other marine fishes, evidencing the need to counteract overfishing effects. In addition, in a climate change scenario, management agencies must implement state-of-the-art sequencing methods, consider our findings in their management plans, and monitor genome-wide heterozygosity over time to improve sustainable fisheries and the long-term viability of its populations.

Blue shark (Prionace glauca) occurrence and relative abundance in the western South Atlantic Ocean influenced by spatiotemporal variability, environmental variables, and oceanographic processes.

The aim of this study was to evaluate spatiotemporal patterns in the distribution and relative abundance of blue sharks and their relationship with environmental variables and oceanographic processes in the southwestern Atlantic Ocean. We modeled data on catch records from the Brazilian pelagic tuna longline fleet using generalized additive models (GAMs). The distribution of Prionace glauca was influenced by salinity, chlorophyll-a and temperature. Our models showed that both the catch per unit of fishing effort (CPUE) and the probability of presence increased mainly between March and August. The CPUE was also influenced by ocean depth and sea surface height, and the probability of occurrence by ocean fronts and slope. The highest CPUE values and probability of occurrence of blue sharks tended to occur mainly in parts of the continental slope off Brazil and at the Rio Grande Rise, characterized by the presence of seamounts. Such hotspots for P. glauca could potentially be considered in fisheries management plans.

Short-term movements and habitat preferences of sailfish, Istiophorus platypterus (Istiophoridae), along the southeast coast of Brazil

Pop-up satellite archival tags (PSATs) were deployed on four sailfish, Istiophorus platypterus, in the coastal waters of Rio de Janeiro State in southeast Brazil during January and February of 2009 (sailfish I and II) and between November 2010 and January 2011 (sailfish III and IV). The total number of days monitored (i.e., time that the tags remained attached) were 12 (sailfish I), 51 (sailfish II), 16 (sailfish III) and 43 days (sailfish IV). The results indicate a clear pattern of vertical habitat utilization with the majority of the time spent concentrated near the uniform sea surface layer occupying a relatively narrow temperature range. Despite the clear preference for epipelagic surface waters, sailfish regularly undertook vertical excursions into deeper waters (>50 m) within three to six hour intervals. "Most Probable Tracks" (estimated from raw geolocations using the state-space Kalman filter model) and linear displacements suggested that tagged sailfish did not move significant distances from the tagging site. In brief, our report provides information regarding the biology of sailfish in the southwestern Atlantic and how vertical distributions during the day and night are influenced by water temperature and how this information can improve sailfish stock assessments in southwestern Atlantic Ocean.

Quatro exemplares de agulhão-vela foram marcados com marcas eletrônicas monitoradas por satélite ('Pop-up satellite archival tags - PSATs') nas águas costeiras do Rio de Janeiro, sudeste do Brasil, durante janeiro e fevereiro de 2009 (agulhão-vela I e II) e entre novembro de 2010 e janeiro de 2011 (agulhão-vela III e IV). O número total de dias monitorados (ou seja, o tempo que as marcas permaneceram implantadas nos peixes) foram 12 (agulhão-vela I), 51 (agulhão-vela II), 16 (agulhão-vela III) e 43 dias (agulhão-vela IV). Os resultados demonstram um padrão claro de utilização do hábitat com a maior parte do tempo despendido predominantemente próximo à superfície do mar ocupando águas com uma faixa de temperatura restrita. Apesar da preferência por águas superficiais, os agulhões frequentemente realizaram mergulhos para águas mais profundas (ca. > 50 m) em intervalos de três a seis horas. A "rota mais provável" estimada a partir dos dados brutos de geolocalização e o modelo 'State-Space Kalman Filter' sugerem que os agulhões marcados não realizaram migrações significativas a partir do local de marcação. Em resumo, nossos resultados apresentam informações sobre a biologia da espécie no Atlântico Sudoeste e como as migrações verticais durante o dia e a noite são influenciadas pela temperatura da água e como essa informação pode auxiliar as avaliações de estoques de agulhão-vela no sudoeste do Atlântico.