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18 A. B. M. MOORE ET AL. substantiated record of a devil ray (Mobulidae) from The Gulf (unpubl. data). In addition, the surveys provided material and data on several taxa in need of description or taxonomic resolution that will contribute to an improved understanding of Indo-Pacific Ocean elasmobranch diversity. PATTERNS OF DIVERSITY AND DISTRIBUTION Local patterns of diversity from this study are difficult to compare quantitatively when based on samples of differing sizes from landings of different fleets. Based on a qualitative comparison of the data (and excluding those species recorded on only a handful of occasions), Kuwait was notable in that a number of species (C. leiodon, R. oligolinx, R. granulatus and A. flagellum) were only recorded there, which may be due to the proximity of the Shatt al Arab. These data and those from other studies indicate geographical differences in the abundance of common small carcharhinid species such as the prevalence of C. dussumieri along the coasts of Kuwait, Qatar (this study) and Iran (Blegvad, 1944 as Carcharias menisorrah), but relative rarity off the Omani coast (Henderson et al., 2007; A. Henderson, pers. comm.). Loxodon macrorhinus was absent from Kuwait in both 2008 and 2011 but relatively abundant in Qatar, Abu Dhabi (this study) and in Oman’s landings (Henderson et al., 2007). This may be related to this species apparently preferring low turbidity environments (Gutteridge et al., 2011). Rhizoprionodon oligolinx was only recorded (but relatively abundant) in Kuwait, where the morphologically similar L. macrorhinus was absent. Excluding two species recorded as single individuals from Abu Dhabi that had probably originated from the Gulf of Oman [silky shark Carcharhinus falciformis (Müller & Henle 1839) and scalloped hammerhead Sphyrna lewini (Griffith & Smith 1834)] and the H. uarnak species complex, the number of elasmobranch species recorded in the current study from The Gulf was 36. Again, excluding H. uarnak, this is notably less than the 56 reported from Oman (Henderson & Reeve, 2011) and largely reflects the lack of species associated with deeper waters in the shallow Gulf. Notable temporal differences were observed in the abundance of two species of carcharhinid (R. acutus and C. sorrah) that were common in Kuwait in 2008 but were rare or absent at this location in 2011. This absence could be due to a large number of variables, possibly including windy conditions at sea in 2011 reducing gillnet catches of these species, or temporal variation in estuarine discharges affecting distribution. Surface water temperature was probably not a factor, being similar at the time of both surveys (22·2 ◦ C in 2008 and 21·4 ◦ C in 2011, measured at the same station off east Failaka Island; F. Al-Yamani, unpubl. data). SHARK BIOLOGY There was a highly significant bias towards (mostly mature) males for both C. dussumieri and R. acutus, in both Kuwait in 2008 and Qatar. This may be related to spatial segregation from males by birthing or near-term pregnant females, as both species are reported as having peaks in parturition in spring or summer in the region (Assadi, 2001; Henderson et al., 2006). Interpretation of elasmobranch sex ratio data from landings is, however, problematic, as any significant differences may be due to a number of confounding factors (e.g. gear bias) as well as natural segregation, which is commonly reported in elasmobranchs (reviewed in Sims, 2005). © 2012 The Authors Journal of Fish Biology © 2012 The Fisheries Society of the British Isles, Journal of Fish Biology 2012, doi:10.1111/j.1095-8649.2011.03210.x
ELASMOBRANCHS IN KUWAIT, QATAR AND ABU DHABI 19 Carcharhinus dussumieri in this study attained the maximum reported L T of 100 cm (Compagno et al., 2005), consistent with previous work locally off Iran (Blegvad, 1944, as C. menisorrah) and larger than the maximum of 93·7 cmL T recorded off Indonesia (White, 2007). Male maturity size range of C. dussumieri in the current study was 63–80 cm L T (all mature animals ≥66 cm L T and an L T50 of 72·1 cm) and broadly consistent with male size at first maturity (67 cm L T ) and L T50 (69 cm) recorded off Iran’s Gulf of Oman coast (Assadi, 2001) but slightly smaller than that of c. 74cmL T reported from Indonesia (White, 2007). The size at male maturity recorded for C. sorrah in this study (i.e. all mature by c. 110 cm L T ) is broadly consistent with that for Indonesia and most other locations [recorded and reviewed by White, 2007)]. One female C. sorrah from Qatar of 166 cm L T extends the reported maximum size for this species (160 cm L T ; Compagno et al., 2005; White, 2007, Henderson et al., 2009). Landings of this species were conspicuous in their dominance by juveniles of the 70–85 cm size class (c. 77% of all C. sorrah recorded), indicating that this group is particularly vulnerable to capture locally in spring. Given a reported birth size of 45–60 cm (Compagno et al., 2005) and rapid growth of neonates of c. 20 cm in the first year off northern Australia (Davenport & Stevens, 1988), it is probable that this group represents individuals in their first year or so of life. In Chiloscyllium arabicum maximum L T has been reported as 70 cm (Compagno et al., 2005), yet, in this study, males and females were often larger than this (≤77 and ≤80 cm L T , respectively) which accords with 78 cm L T reported in an earlier study from The Gulf (Goubanov & Shleib, 1980). Maturity in this species was reported to occur between 44·6 and 54·1 cmL T (Dingerkus & DeFino, 1983 as C. confusum, sex not specified), yet in this study all stages were notably larger than this (juvenile 56 and 62 cm L T , n = 2; maturing 62 and 68 cm L T , n = 2; mature 60–77 cm L T , n = 60). In this study, C. arabicum was notable in that it was the only species whose size frequency distribution (pooled samples for both males and females) was normal, indicating that a wide range of life stages are vulnerable to capture locally in April. Loxodon macrorhinus size ranges from the current study are similar to those recorded from Oman (Henderson et al., 2009), although the maximum reported size from both of these studies is smaller than that of 99 cm L T recorded in Indonesia (White, 2007). Further regional differences in the biology of this species are the size at male maturity, which in this study (61–71 cm L T ;64·0 L T50 ) is notably smaller than that recorded from Indonesia (80–83 cm L T ,81·9 cmL T50 ; White, 2007) and southern Africa (73–75 cm L T ; Bass et al., 1975). The highly significant bias towards (large, mature) males in the April sample at Abu Dhabi is consistent with notable sex and size segregation reported for this species from longline surveys in the Maldives (Anderson & Ahmed, 1993). The average size of R. acutus at Abu Dhabi (probably originating from the Gulf of Oman) was significantly greater than at other locations, and the mean size for both males and females of R. acutus from Oman (Henderson et al., 2009) was also greater than that found in this study. While this may simply represent gear bias, it may also indicate that populations of this species from The Gulf and the Gulf of Oman have different size characteristics. The L T50 for males of R. acutus from the current study (61·7 cmL T ) was also smaller than that from Oman (64·7 cmL T ; Henderson et al., 2006), Indonesia (71·8 cmL T ) and other locations in the Indo-West Pacific (White, 2007). Maximum size of R. acutus in this study (89 cm L T ) is at © 2012 The Authors Journal of Fish Biology © 2012 The Fisheries Society of the British Isles, Journal of Fish Biology 2012, doi:10.1111/j.1095-8649.2011.03210.x
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