The distribution,diversity and abundance of elasmobranch fishes in a modified subtropical estuarine system in Kuwait

To address the paucity of information on the spatial and temporal composition of elasmobranch fish assemblages in the Arabian region, data from fisheries surveys around Kuwait's Boubyan Island, in the Tigris‐Euphrates‐Karun delta at the head of the Arabian (Persian) Gulf were examined. A total number of 461 elasmobranchs consisting of at least 13 taxa were captured by gillnets (300 m length, 4, 4.5, 5.5, and 5.75 inch stretch mesh) and otter trawls (5‐m chain line length, 34 and 10 mm stretch mesh in body and cod end, respectively) from February 2004 to March 2005. Seventy‐nine gillnet sets averaged 24 min soak time, while 431 5‐min trawl tows averaged 4.1 km h^?1 for a swept area of 1025 m² tow^?1 with a net spread of 3 m. Most taxa were infrequently recorded. Of the six species that accounted for over 90% of individual abundance, the longheaded eagle ray Aetobatus flagellum (170, 269.5 kg) and the scaly whipray Himantura imbricata (137, 17.3 kg) ranked first and second, respectively. Most sharks were Arabian carpetshark Chiloscyllium arabicum (22, 7.7 kg) and milk shark Rhizoprionodon acutus (21, 2.3 kg). Species richness for gillnets was greatest along the main Gulf coast (H' = 1.87), although H. imbricata and A. flagellum were widespread. Based on published birth sizes, neonates or young‐of‐year of several species were recorded. Results indicated that the water temperature strongly determined seasonal distribution: no elasmobranchs were recorded in the winter following a 14°C drop after October, and diversity, abundance and biomass generally increased in summer. While salinity varied from 28.4 to 39.8, major anthropogenic modifications in the upper Tigris‐Euphrates watersheds and development of Boubyan Port will result in higher salinities, which in turn will influence longer‐term patterns of elasmobranch distribution.