Abstract
Isla Mujeres, Mexico is home to one of the most well-known aggregations of sailfish. Despite its fisheries prominence, little is known about this sailfish assemblage, or its relationship to other aggregation sites in the western Atlantic. In January 2012, April 2013 and 2014, we deployed 34 popup satellite archival tags on sailfish in order to study their behavior, population connectivity and biophysical interactions. Sailfish were monitored for up to one year, and displayed (1) predominantly shelf associated activity (2) occupancy of the Yucatán Current near Isla Mujeres for up to five months and (3) subsequent dispersals from the Yucatán to productive coastal areas in the Gulf of Mexico, the Caribbean Sea and along the South American coast. Tagged sailfish occupied a median temperature of 26.4°C (interquartile range, IQR = 2.5 °C; range = 12.3–33.3 °C) and median depth of 4.4 m (IQR = 19 m; range = 0–452 m). Diel activity was present and individuals made distinctive descents before sunrise and sunset. Tracking missions of sufficient duration (~1 year) revealed previously undetected connectivity between western Atlantic sailfish fisheries and pelagic longline catches, and highlighted how fishery independent tagging can improve understanding of sailfish migrations and behavior for assessment and management.
Highlights
Sailfish (Istiophorus platypterus), an epipelagic billfish, are prized by recreational fishermen[1,2,3,4], and provide major nutritional, economic and cultural benefits for artisanal fishing communities[5,6,7,8]
Of the nine reported at term, one MiniPAT reported at four months, three X-Tags at six months, and five X-Tags at a full year, one of which was carried by the smallest tagged sailfish (137 cm lower jaw fork length (LJFL)) in this study
These represent the longest deployments of PSATs on sailfish to date
Summary
Sailfish (Istiophorus platypterus), an epipelagic billfish, are prized by recreational fishermen[1,2,3,4], and provide major nutritional, economic and cultural benefits for artisanal fishing communities[5,6,7,8]. Both eastern and western stocks are considered likely overfished, with biomass below, and fishing mortality above, maximum sustainable yield[9], uncertainties are recognized in the stock assessment conducted by the International Commission for the Conservation of Atlantic Tunas (ICCAT)[10]. To shed light on these issues, we present the first long-term (up to one year) records of dispersal, depth, temperature and oceanographic associations of sailfish collected via electronic tags over three field seasons off Isla Mujeres, Mexico
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