Spatial and seasonal variation in a target fishery for spotted eagle ray Aetobatus narinari in the southern Gulf of Mexico

Abstract

The target fishery for the spotted eagle ray Aetobatus narinari in the southern Gulf of Mexico is little known. The landings of four small-scale vessels at two fishing localities were sampled and fishermen were interviewed in 2009. Rays landed at Campeche [mean ± standard deviation (SD) 1204 ± 225.3 mm disc width (DW)], fished at 30-50 km from the shore, were larger than rays landed at Seybaplaya (924 ± 206.5 mm DW), fished at 8-15 km from the shore. Ray catches were male biased off Campeche and female biased off Seybaplaya. Catch rate off Campeche was 6.6 (±4.9) rays per vessel trip and off Seybaplaya was 3.0 (±2.9) rays per vessel trip. Fishermen stated that catches of A. narinari are positively influenced by winter cold fronts, turbidity, low sea temperature, and new moon phase, and negatively influenced by the presence of cownose rays Rhinoptera bonasus. Spatial variation in size composition, and sex and maturity ratios of A. narinari were evident between sites. Catch rates of A. narinari varied with individual fisherman and seasonally between months with winter cold fronts versus warmer months. Fishermen reported a general decline in catches of A. narinari over recent decades in this region.

Reproductive parameters of the southern stingray Dasyatis Americana in southern gulf of Mexico

“…Temperature was not provided by Henningsen (2000), however, Henningsen & Leaf (2010) indicate that temperature was maintained at 24-25°C in their study. Surface temperatures ranges between 23.9-28.7°C in the western Campeche Bank (Cuevas-Zimbrón et al 2011) and are closely similar to the northern Campeche Bank where they fluctuate between 23.5-29.5°C, while bottom temperatures, in the second region, ranges between 22.9-24.5°C (Piñeiro et al, 2001). If the same bottom temperatures were observed in the western Campeche Bank, specimens of D. americana are apparently exposed to slightly lower temperatures in the wild, which could explain that gestation is longer in wild specimens.…”

Site affinity of whitespotted eagle rays Aetobatus narinari assessed using photographic identification

“…The majority of A. narinari sightings were of adult‐sized individuals, suggesting that the rays may separate by life stage around South Caicos. Catch data from both targeted and by‐catch A. narinari fisheries in Mexico and Brazil suggest that the rays segregate by size (Yokota & Lessa, ; Cuevas‐Zimbrón et al, ). Data from the Southern Gulf of Mexico show that juvenile rays account for a significantly higher proportion of the catch at a site only 8–15 km offshore, compared with the site 30–50 km offshore (Cuevas‐Zimbrón et al, ).…”

“…Catch data from both targeted and by‐catch A. narinari fisheries in Mexico and Brazil suggest that the rays segregate by size (Yokota & Lessa, ; Cuevas‐Zimbrón et al, ). Data from the Southern Gulf of Mexico show that juvenile rays account for a significantly higher proportion of the catch at a site only 8–15 km offshore, compared with the site 30–50 km offshore (Cuevas‐Zimbrón et al, ). In north‐east Brazil, juvenile and neonate rays were caught by gillnets in depths <10 m (Yokota & Lessa, ).…”

“…Images would require a ventral view to confirm the lack of claspers, which is extremely difficult to accomplish while snorkelling. Collectively, results from this study and aforementioned studies suggest that sex composition in A. narinari varies by species and location (Schluessel et al, ; Cuevas‐Zimbrón et al, ; Naylor et al, ; Tagliafico et al, ; Bassos‐Hull et al, ).…”

“…Some species of sharks frequently segregate by sex (Springer, 1940;Klimley, 1987;Stevens & McLoughlin, 1991;Sims et al, 2001), while the pelagic stingray Pteroplatytrygon violacea (Bonaparte 1832) is also known to segregate by sex (Wilson & Beckett, 1970). Previous studies that examined targeted A. narinari fishery catch data in Mexico and Venezuela also reported differing sex ratios (Cuevas-Zimbrón et al, 2011;Tagliafico et al, 2012), with two fishing sites in Mexico dominated by the opposite sex (Cuevas-Zimbrón et al, 2011) and one fishing site in Venezuela dominated by females (Tagliafico et al, 2012). In south-west Florida, scientific boat-based surveys demonstrated overall catch was biased towards males, but on a month-to-month basis the sex ratio only differed significantly during one of the six study years (Bassos-Hull et al, 2014).…”