Aaron C. Henderson

Whale Sharks, Rhincodon typus, Aggregate around Offshore Platforms in Qatari Waters of the Arabian Gulf to Feed on Fish Spawn

Whale sharks, Rhincodon typus, are known to aggregate to feed in a small number of locations in tropical and subtropical waters. Here we document a newly discovered major aggregation site for whale sharks within the Al Shaheen oil field, 90 km off the coast of Qatar in the Arabian Gulf. Whale sharks were observed between April and September, with peak numbers observed between May and August. Density estimates of up to 100 sharks within an area of 1 km2 were recorded. Sharks ranged between four and eight metres’ estimated total length (mean 6.92±1.53 m). Most animals observed were actively feeding on surface zooplankton, consisting primarily of mackerel tuna, Euthynnus affinis, eggs.

Marine Turtles in the Turks and Caicos Islands: Remnant Rookeries, Regionally Significant Foraging Stocks, and a Major Turtle Fishery

Abstract This study reviews the status of marine turtles in the Turks and Caicos Islands (TCI) using data gathered during a multidisciplinary study involving field surveys, questionnaire-based interviews, and molecular genetics between 2002 and 2006. Large aggregations of foraging turtles in the archipelagos waters are dominated by juvenile green (Chelonia mydas) and hawksbill turtles (Eretmochelys imbricata), with provisional mixed-stock analysis of these species suggesting that the aggregations originate predominantly from larger and relatively proximate source rookeries in the Wider Caribbean region. This study also suggests that the islands host remnant nesting populations of turtles, with hawksbill turtle nests recorded more frequently than green and loggerhead turtle (Caretta caretta) nests. The TCI islanders retain a culture of turtle use, with the current regulated and legitimate harvest likely to be one of the largest among the Caribbean Islands. This study suggests that historic and current harvest of turtles and their eggs in the TCI may have contributed to the apparent decline in the countrys nesting populations. In order to address this conservation concern, changes to the regulation and management of the TCIs turtle fishery are necessary, but further research is needed to inform these changes.

Noteworthy elasmobranch records from Oman

Records of 11 elasmobranch species previously unreported from, or uncommon in, Omani waters are presented. Records new to Oman include Carcharhinus altimus, C. leiodon, Centrophorus isodon, Ctenacis fehlmanni, Himantura fai, Mobula eregoodootenke and Sphyrna zygaena, whereas noteworthy records of uncommon species include Himantura imbricata, Paragaleus randalii, Rhinobatos salalah and Taeniura meyeni – some of which are confirmed from the Gulf of Oman for the first time. These records bring to 57, the number of elasmobranch species confirmed in Omani waters.

Shark diversity in the Arabian/Persian Gulf higher than previously thought: insights based on species composition of shark landings in the United Arab Emirates

Although fish fauna in the Arabian/Persian Gulf have been studied for decades, shark diversity has only been recently investigated in the region. Here, we present a first comprehensive account of shark diversity from the United Arab Emirates based on fishery-dependent data collected at market and landing sites over a two-year period of field sampling. Landings across the country were dominated by carcharhinids, and six species were found to be most abundant, including the spot-tail shark, Carcharhinus sorrah, and the milk shark, Rhizoprionodon acutus, contributing 31.8xa0% and 29.9xa0%, respectively, of the total number of sharks. While observed landings varied among regions and across seasons, results showed that shark landings were dominated by small-sized species, which may be a reflection of overexploitation. We are now expanding the existing checklist of shark species in the Persian Gulf from 27 to 31, having utilized both morphological identification and genetic barcoding in validating the existence of the grey bamboo shark, Chiloscyllium griseum; the tawny nurse shark, Nebrius ferrugineus; the silky shark, Carcharhinus falciformis; and the sandbar shark, Carcharhinus plumbeus, in these waters. This inventory provides an urgently needed assessment of current regional diversity patterns that can now be used as a baseline for future investigations evaluating the effect of fisheries on shark populations. Results emphasize the need for research on life history traits of the various species in order to determine their regional conservation status, but also reveal that a precautionary approach to conservation will be necessary to mitigate anthropogenic impacts.

Size distributions and sex ratios of sharks caught by Oman’s artisanal fishery

Omans fishery resources are exploited by artisanal and industrial fisheries, but the former accounts for almost 90% of landings. Within the artisanal fishery, sharks have traditionally been harvested for their flesh, but the development of a valuable export market for shark fin has led to increased utilisation of this resource, and anecdotal information suggests that shark abundance has decreased in recent years. Whereas management of the shark fishery is desirable, the biological and socio-economical data on which to base any management plan are lacking. The present study was undertaken to collect size frequency and sex ratio information from the shark species most commonly encountered in the artisanal landings, namely Carcharhinus falciformis, C. limbatus, C. macloti, C. sorrah, lago omanensis, Loxodon macrorhinus, Rhizoprionodon acutus and Sphyrna lewini. The occurrence of large female sharks in the landings, combined with a high proportion of juveniles of certain species, suggests that species-specific size restrictions should be considered in any management plan for Omans shark fishery.

Population genetics of four heavily exploited shark species around the Arabian Peninsula

The northwestern Indian Ocean harbors a number of larger marine vertebrate taxa that warrant the investigation of genetic population structure given remarkable spatial heterogeneity in biological characteristics such as distribution, behavior, and morphology. Here, we investigate the genetic population structure of four commercially exploited shark species with different biological characteristics (Carcharhinus limbatus, Carcharhinus sorrah, Rhizoprionodon acutus, and Sphyrna lewini) between the Red Sea and all other water bodies surrounding the Arabian Peninsula. To assess intraspecific patterns of connectivity, we constructed statistical parsimony networks among haplotypes and estimated (1) population structure; and (2) time of most recent population expansion, based on mitochondrial control region DNA and a total of 20 microsatellites. Our analysis indicates that, even in smaller, less vagile shark species, there are no contemporary barriers to gene flow across the study region, while historical events, for example, Pleistocene glacial cycles, may have affected connectivity in C. sorrah and R. acutus. A parsimony network analysis provided evidence that Arabian S. lewini may represent a population segment that is distinct from other known stocks in the Indian Ocean, raising a new layer of conservation concern. Our results call for urgent regional cooperation to ensure the sustainable exploitation of sharks in the Arabian region.

Population Structure, Abundance and Movement of Whale Sharks in the Arabian Gulf and the Gulf of Oman.

Data on the occurrence of whale sharks, Rhincodon typus, in the Arabian Gulf and Gulf of Oman were collected by dedicated boat surveys and via a public-sightings scheme during the period from 2011 to 2014. A total of 422 individual whale sharks were photo-identified from the Arabian Gulf and the northern Gulf of Oman during that period. The majority of sharks (81%, n = 341) were encountered at the Al Shaheen area of Qatar, 90 km off the coast, with the Musandam region of Oman a secondary area of interest. At Al Shaheen, there were significantly more male sharks (n = 171) than females (n = 78; X2 = 17.52, P < 0.05). Mean estimated total length (TL) for sharks was 6.90 m ± 1.24 (median = 7 m; n = 296). Males (7.25 m ± 1.34; median = 8 m, n = 171) were larger than females (6.44 m ±1.09; median = 7 m, n = 78; Mann-Whitney U test, p < 0.01). Of the male sharks assessed for maturity 63% were mature (n = 81), with 50% attaining maturity by 7.29 m and 100% by 9.00 m. Two female sharks of >9 m individuals were visually assessed as pregnant. Connectivity among sharks sighted in Qatari, Omani and UAE waters was confirmed by individual spot pattern matches. A total of 13 identified sharks were re-sighted at locations other than that at which they were first sighted, including movements into and out of the Arabian Gulf through the Strait of Hormuz. Maximum likelihood techniques were used to model an estimated combined population for the Arabian Gulf and Gulf of Oman of 2837 sharks ± 1243.91 S.E. (95% C.I. 1720–6295). The Al Shaheen aggregation is thus the first site described as being dominated by mature males while the free-swimming pregnant females are the first reported from the Indian Ocean.

Microanatomy of the male and female reproductive tracts in the long-tailed butterfly ray Gymnura poecilura, an elasmobranch with unusual characteristics

The anatomy of the male and female reproductive systems was investigated in the long-tailed butterfly ray Gymnura poecilura using gross observation and light microscopy. The testes are highly asymmetrical, to the extent that only the left testis is functional and the right testis is completely absent. Both of the male genital ducts are present and symmetrical, although spermatozoa only occur in the left duct. The genital ducts are straight and unconvoluted, with regular incomplete internal partitions throughout. Females do not possess a right ovary, nor do the oviducal glands exhibit distinct club and papillary zones, and the baffle zone lacks baffle plates. In all sections of the gland, the tubules display different secretory activities depending on the proximity to the gland lumen. The gland produces a thin egg membrane that encases each egg individually, while the endometrium is formed into trophonemata.

Preliminary assessment of a possible lemon shark nursery in the Turks & Caicos Islands, British West Indies

Abstract. n Juvenile lemon sharks, Negaprion brevirostris, were captured at shallow-water sites around South Caicos over a 16 month period. Capture and recapture rates were relatively low, and residency time appeared to be short, possibly indicating that South Caicos is just part of a larger nursery area. Nonetheless, the presence of neonates with fresh umbilical scars confirms that parturition did take place within the study area. It is suggested that the juvenile sharks utilise a larger activity space than in previously studied areas, and that this is facilitated by strong tidal movements over a large expanse of contiguous habitat.

Acroteriobatus omanensis (Batoidea: Rhinobatidae), a new guitarfish from the Gulf of Oman

The recently resurrected genus Acroteriobatus is represented in the western Indian Ocean by eight species, including a new guitarfish Acroteriobatus omanensis sp. nov. This small species (reaching ~60 cm TL) was discovered off Oman in an investigation of the chondrichthyan fauna of the Arabian in 2002 and 2003. Its distinctiveness from other members of the genus Acroteriobatus is strongly supported by molecular data. Acroteriobatus omanensis sp. nov. differs from all other members of the genus by its very narrowly pointed snout and having a dense pattern of small, symmetrically arranged ocelli each consisting of a white spot surrounded by a darker rim. Acroteriobatus annulatus and A. ocellatus have axa0xa0xa0xa0xa0xa0 more-or-less ocellated dorsal colour pattern but the markings are larger and differ in form (ocelli consisting of a small dark central spot surrounded by a dark-edged pale ring in A. annulatus; larger, irregularly shaped ocelli with pale centres surrounded by a dark brown rim in A. ocellatus).