Relative Abundance of Pelagic Sharks in the Western North Atlantic Ocean, Including the Gulf of Mexico and Caribbean Sea

• Published in: Gulf and Caribbean Research
• Main Authors: Cortes, Enric, Brown, Craig A., Beerkircher, Lawrence R.
• Format: Text
• Language: unknown
• Published: The Aquila Digital Community 2007
• Subjects: pelagic sharks; North Atlantic Ocean; Gulf of Mexico; Caribbean Sea; Marine Biology; North Atlantic
• Online Access: https://aquila.usm.edu/gcr/vol19/iss2/6; https://doi.org/10.18785/gcr.1902.06; https://aquila.usm.edu/context/gcr/article/1415/viewcontent/Pages_from_vol19.2_7.pdf

Little information exists on the status of pelagic shark populations in the Atlantic Ocean, especially in the Gulf of Mexico and Caribbean Sea. We derived indices of relative abundance for pelagic sharks based on mandatory logbooks and observer reports from a scientific observer program of the United States (US) pelagic longline fleet. Time series data from the pelagic longline logbook program (1986-2005) and the pelagic longline observer program (1992-2005) were standardized with Generalized Linear Model (GLM) procedures. Declines in relative abundance for the 6 pelagic shark species or genera examined in the logbook data analysis ranged from 43% for mako sharks, Isurus spp., to 88% for blue sharks, Prionace glauca, whereas declines in relative abundance obtained from the observer data analysis were less accentuated than those in the logbook data analysis, with the trend being positive for night sharks, Carcharhinus signatus, and thresher sharks, Alopias spp. There was no significant change in the fork length at capture over the time period considered for blue sharks, shortfin makos Isurus oxyrinchus, or night sharks. The trends obtained must be viewed cautiously given recognized shortcomings, especially of the logbook dataset, and the highly migratory nature of pelagic sharks, which requires a more comprehensive evaluation of trends throughout their range.