Abstract
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.
Highlights
In the Atlantic Ocean, sailfish Istiophorus platypterus (Shaw, 1792) are widely distributed in subtropical and tropical waters and are occasionally found in temperate waters, as well as the Mediterranean Sea
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
The results indicate a clear pattern of near surface habitat utilization in sailfish, with the majority of the time spent near the sea surface within a relatively narrow temperature range
Summary
In the Atlantic Ocean, sailfish Istiophorus platypterus (Shaw, 1792) are widely distributed in subtropical and tropical waters and are occasionally found in temperate waters, as well as the Mediterranean Sea. Sailfish are caught as bycatch in most commercial longline fisheries targeting tunas (Thunnus spp.) and swordfish (Xiphias gladius Linnaeus, 1758) throughout the Atlantic Ocean (Restrepo et al, 2003). The advent of fishery independent pop-up satellite archival tags (PSATs) in the late 1990s, provided a new tool to research the movements of large pelagics, including sailfish. The first experiment using PSATs on sailfish was conducted in the Gulf of Arabia (Hoolihan, 2004). Prince & Goodyear (2006) deployed pop-up tags on sailfish in the Northwestern Atlantic and in the Eastern Central Pacific to assess the vertical distribution of this species. Hoolihan & Luo (2007) tagged 18 sailfish with pop-up tags which provided detailed information regarding summer residence patterns in the Gulf of Arabia The first experiment using PSATs on sailfish was conducted in the Gulf of Arabia (Hoolihan, 2004). Prince & Goodyear (2006) deployed pop-up tags on sailfish in the Northwestern Atlantic and in the Eastern Central Pacific to assess the vertical distribution of this species. Hoolihan & Luo (2007) tagged 18 sailfish with pop-up tags which provided detailed information regarding summer residence patterns in the Gulf of Arabia
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