Species, sex, size and male maturity composition of previously unreported elasmobranch landings in Kuwait, Qatar and Abu Dhabi Emirate

Abstract

This paper presents data from the first major survey of the diversity, biology and fisheries of elasmobranchs in the Persian (Arabian) Gulf. Substantial landings of elasmobranchs, usually as gillnet by-catch, were recorded in Kuwait, Qatar and the Emirate of Abu Dhabi (part of the United Arab Emirates), although larger elasmobranchs from targeted line fisheries were landed in Abu Dhabi. The elasmobranch fauna recorded was distinctive and included species that are undescribed, rare and have a highly restricted known distribution. Numerical abundance was dominated by sharks (c. 80%), of which carcharhinids were by far the most important. The milk shark Rhizoprionodon acutus and whitecheek shark Carcharhinus dussumieri together comprised just under half of all recorded individuals. Around 90% of recorded sharks were small (50-90 cm total length, L(T) ) individuals, most of which were mature individuals of species with a small maximum size (<100 cm L(T) ), although immature individuals of larger species (e.g. Carcharhinus sorrah and other Carcharhinus spp.) were also important. The most frequently recorded batoid taxa were cownose rays Rhinoptera spp., an undescribed whipray, and the granulated guitarfish Rhinobatos granulatus. The first size, sex and maturity data for a wide range of Gulf elasmobranch species are presented (including L(T) at 50% maturity for males of four shark species) and include some notable differences from other locations in the Indo-West Pacific Ocean. A number of concerns regarding the sustainability of the fishery were highlighted by this study, notably that most of the batoid species recorded are classed by the IUCN Red List as vulnerable, endangered, data deficient or not evaluated. Despite their considerable elasmobranch landings, none of the three countries sampled have developed a 'Shark Plan' as encouraged to do so under the FAO International Plan of Action: Sharks. Furthermore, Kuwait and Qatar currently report zero or no elasmobranch landings to the FAO.

Reproductive biology and diet of the grey sharpnose shark Rhizoprionodon oligolinx Springer, 1964 (Chondrichthyes: Carcharhinidae) from the north-eastern Arabian Sea

“…The average size of females of this species was significantly larger than males and 37.3% of recorded landings were pregnant females. Moore et al (2012) reported similar results in Kuwait waters where females (mostly pregnant stage) dominated the landings.…”

“…The differences could be the result of several factors like fishing gear selectivity and/or sample size, regional differential growth based on habitat (Motta et al, 2005). Furthermore, R. oligolinx from this study attained a greater maximum size (93.0 cm TL) than previously reported from elsewhere (80 cm TL by Abdul Nizar et al, 1988; 70 cm TL by Compagno et al, 2005; 85 cm TL by Moore et al, 2012). The difference detected between size-frequency distributions of females and males is probably a consequence of sexual segregation, a general characteristic of shark populations that is normally associated with reproduction, migration or competition (Springer, 1967;Klimley, 1987;Stevens and Mcloughlin, 1991;Motta et al, 2005).…”

“…The size range of R. oligolinx observed in the gillnet fishery of northern Arabian Sea (27-93 cm TL) differed slightly from those reported from other regions, by Moore et al (2012) in Kuwait waters, (45-85 cm TL for females and 45-64 cm TL for males) and by White (2007) in Indonesian waters (26-65 cm TL for females, 29.5-52.0 cm TL for males). The differences could be the result of several factors like fishing gear selectivity and/or sample size, regional differential growth based on habitat (Motta et al, 2005).…”

“…Length at maturity of males were estimated at 29-38 cm TL in India (Appukuttan and Nair, 1988); 43-45 cm TL with Lm 50 at 53 cm in Indonesia (White, 2007), Lm 50 at 53 cm TL in Kuwait (Moore et al, 2012) and 55 cm TL in Bahrain (Moore and Pierce, 2013).…”

“…In the north-eastern Arabian Sea of Indian EEZ, R. oligolinx is one of the most common sharks having a relatively high economic value for fin and salted meat, caught dominantly by gillnetters operating in the inshore waters. Studies on the distribution and taxonomic account of R. oligolinx are limited (Springer, 1964;Nair et al, 1974;Talwar, 1976;Raje et al, 2007) and studies on biology are rare (Appukuttan and Nair, 1988;White, 2007;Moore et al, 2012) that can support management decisions.…”