Diversity, abundance, behaviour, and catchability of fishes from trap catch and underwater video in the Arabian Gulf

摘要

Underwater camera systems can be a valuable tool for evaluating fish assemblages and estimating relative abundance of stock, assessing behaviour of marine species, and monitoring ecosystem change. Within the Arabian Gulf waters of the United Arab Emirates (UAE), overall fish species diversity and distribution and frequency of occurrence were determined from baited underwater video (BUV) and trap video in commercial fish traps (gargours). A total of 75 species or species groups were recorded, with the highest species diversity recorded on BUV (70 species or species groups, compared with 58 and 55 species or species groups on trap video and in trap catch, respectively). Most frequently recorded species included Nernipterus peron11, catfishes (Netwna spp.), Echeneis naucrates, Himantura uarnak, and Lethrinus microdon. Sightings of 8 key species of commercial interest and Echeneis naucrates were found to be similar between season and method, but observations of some species appeared to vary by survey area (inshore, offshore trawlable, offshore untrawlable). Arrival time for key species to reach maximum numbers (MaxN) occurred between 50 and 100 min of trap deployment, indicating that the video observation length (up to 180 min) and trap deployment length (about 360 min) were appropriate for estimating abundance. Escapement within the observed period (about 180 min) varied from zero for Diagramma pictum and Lethrinus borbonicus to 13% for Epinephelus cololdes and 20% for L. lentjan. Escapement post video reached 71% for Lethrinus borbonicus. The presence of the commercially important and predatory fish Epinephelus coioides appeared to affect the catchability of fishes with behaviours that included territoriality and predation.