Life history and seasonal occurrence of the spotted eagle ray, Aetobatus narinari, in the eastern Gulf of Mexico

摘要

The spotted eagle ray, Aetobatus narinari, is listed on the IUCN Red List of Threatened Species as Near Threatened with a decreasing population trend, but many aspects of this ray's biology and population status are unknown. Aerial and on-water surveys were conducted in the eastern Gulf of Mexico off southwest Florida 2008-2013, to document seasonal occurrence and life history characteristics of this species. Aerial surveys documented spotted eagle rays mostly in spring, summer, and autumn months with larger aggregations observed near inlet passes. Boat-based surveys documented rays on 152 out of 176 survey days, mostly as solitary individuals but sometimes in aggregations of up to 60. More rays were observed when water temperatures were 23-31 A(0)C. A total of 393 rays (231 males, 161 females, 1 unrecorded sex) were captured, measured, sampled, tagged, and released. Sizes ranged 41.4-203.0 cm disc width (DW) and weight 1.1-105.5 kg. Male size at 50 % maturity was 127 cm DW. Five percent (19) of tagged rays were recaptured after 5-1,293 days at liberty and recaptured rays exhibited faster growth than previously estimated from vertebral readings. Based on observations of rays relative to survey effort, numbers of observed rays declined after 2009 for reasons not yet understood. This observation, together with concerns about sustainability of fisheries targeting these rays in nearby Mexico and Cuba, underscore the need for investigations into stock structure, population trends, growth, and critical habitat of spotted eagle rays throughout the Gulf of Mexico, Caribbean Sea, and elsewhere in their range