International Journal of Agricultural Science Research Vol. 3(2), pp. 019-024, February 2014 Available online at http://academeresearchjournals.org/journal/ijasr ISSN 2327-3321 ©2014 Academe Research Journals Full Length Research Paper Abundance of vulnerable ray species Himantura undulata in the Bay of Bengal Bikram Jit Roy*, Nripendra Kumar Singha, S.M. Hasan Ali, Gaziur Rhaman and Fokhrul Alam Marine Fisheries Survey Management Unit, Agrabad, Chittagong, Bangladesh. Accepted 30 October, 2013 This study was carried out during July, 2009 to June, 2013 continually on the vulnerable ray species, Leopard whipray - Himantura undulata (Bleeker, 1852), and its total landing, total landed number and parentage contribution were recorded from the selected two fish landing centers at BFDC Fish Harbour, Cox’s Bazar and Fishery ghat fish landing center, Chittagong District. The highest landing volume was recorded as 0.420 MT in the month of March, 2010 and the lowest was 0.112 MT in August, 2011 period. The average highest and lowest landing of H. undulata were 52.5 and 2.88 kg in the months of November, 2012 and March, 2009 period respectively. During 2009-2010, H. undulata contributed only 0.560 MT (0.33%) followed by 2010-2011, 2011-2012 and 2012-2013 periods, where it contributed 0.893 MT (0.28%), 0.882 MT (0.23% ) and 0.434 MT (0.12%) of the year wise total landing volume of sharks and rays respectively. Month wise maximum and minimum recorded numbers of landed H. undulata were 59 and 4 in the month of November, 2012 and July, 2009 respectively. The highest and lowest percentage contribution were analyzed as 2.54% and 0.28% in July, 2009 and March, 2013 respectively in the month wise total landing amounts of sharks and rays. However, its commercial importance and fishing pressure is now in a vulnerable position by The International Union for Conservation of Nature (IUCN). Key words: Abundance, total landing, percentage contribution, commercial importance, The International Union for Conservation of Nature (IUCN). INTRODUCTION The shark fisheries (shark and ray species) in Rays are caught and sold at a reasonable price; they Bangladesh are mostly artisanal. Sharks are harvested appear predominantly in the shallower strata up to 50 m as target species mainly by shark net (modified gill net) depth (Malaysia, NOPA-Shark, 2006). Rays are not and hook and lines, and as a by catch in other homogeneously distributed over the whole area but are commercial fishing; whereas rays are captured only as by mainly found in two zones, one of which is near Elephant catch in hook and lines and sometimes exploits in point and the other in the center of the middle ground trammel net and set bag net as well (Roy et al., 2007). area (near Mohipur) (Lamboeuf, 1987). Only 80-100 numbers of mechanized boats are engaged In Bangladesh, there are only a few small shark in commercial fishing for sharks and rays at Cox’s Bazar fisheries processing plants in the form of cottage industry and Chittagong districts. The fishing took place in the operated mostly by fisher flocks due to the irregular eastern and western part of the Bay of Bengal in supply of shark and ray species (Roy et al., 2007). Rays Bangladesh region. Large numbers of small size are mostly consumed as a fresh meat, while some are juveniles or new born sharks and rays are caught by processed as salted fish and in dried form. During 2011- shrimp and fish trawlers, which were not recorded or 2012, the total marine fish production was 578,620 MT of reported for small size and low market value, and which shark fishery contributed only 0.80% (4205 MT) thereafter discarded as a trash (Roy et al., 2007). (DOF, 2011-2012). The International Union for The multi species coastal fisheries, at both artisanal and commercial levels, comprise 56 species of sharks and rays (Day, 1969), though Roy et al. (2011) recorded 35 species for both sharks (11 species) and rays (24 *Corresponding author. E-mail: [email protected]. species) in our marine territory. Tel: 00 88 01815509464. Roy et al. 020 Conservation of Nature (IUCN) (2009) has assessed the study period, the recorded highest length and weight of Leopard whipray as vulnerable, as it faces heavy fishing H. undulata were 110 cm (DW) and 55.0 kg respectively. pressure and habitat degradation across much of its During these periods, newly born H. undulata (small size) range (Internet, July, 2011). So this study was was recorded as 22 cm (DW) and the weight was 170 undertaken to know the present status of the species in gm, whereas the mother’s body weight was 0.132 kg and Bangladesh. the DW was 110 cm in the month of March, 2010 which is nearly similar to the report of White et al. (2006). During MATERIALS AND METHODS the study period, abundance of H. undulata was very rare. It was found only in 12 months out of 60 months (5 The field study was conducted from July, 2009 to June, years study period) from the selected two landing centers 2013 in two shark and ray fish landing centers at BFDC and it contributed less than 3.0% of the total month wise Fish Harbour, Cox’s Bazar and Fishery ghat fish landing catch of sharks and rays landing volumes. So, for the center, Chittagong district. These sampling centers were vulnerable elasmobranches species, there is need for selected in order to cover a wide range of the landing proper management plan. Roy et al. (2011) reported that centers, retail and whole sale markets, target and the very rare ray species of H. undulata contributed 1.54 incidental catches of the species, from the Bay of Bengal and 2.17% abundance, which was observed in the month of Bangladesh region. of July, 2009 and March, 2010 respectively. In the study The total numbers of month wise landing data were period, it was observed that in the immature stage of the recorded at the two landing stations and a formal face to species, H. undulata was seen to have many black spots face interview of boat owners/divers of commercial from the dorsal view of the whole body and in the virtual fishing vessels was conducted by a scientific officer (total side, dark line was present in the anterior lobe, whereas of five) and field officer (ten) alternately. The data were in the mature stage of the species, reticulate dark brown collected in new-moon, full-moon, first quarter, last rings were present in the dorsal side of the body (Figure quarter and other days of the moon month from the 1). landing centers. Sampling days are 8 in each month of Most rays are viviparous, bearing live young “litters” of the year continuously by the Marine Fisheries Survey five to ten. It is listed as vulnerable on the IUCN Red List Management Unit, Chittagong. Data processing and due to over harvesting and loss of its preferred shallow analysis were done manually and with the use of water inshore habitats near mangrove (Wild Fact Sheet, computer. 2013). RESULTS AND DISCUSSION Landing Species description and distribution Year wise The Leopard whipray - Himantura undulata (Bleeker, In the year 2009-2010, a total of 172.266 MT of exploiting 1852) is a species of stingray in the family Dasyatidae, sharks and rays were recorded, among which H. distributed widely in the shallow waters near the shore, undulata contributed only 0.33% (0.560 MT). During close to land than the breaking waves and in Indo-pacific 2010-2011, the total landing of H. undulata was recorded region from Bay of Bengal to Northern Australia. It is not as 0.893 MT (0.28%), where the landing volume of total found at all in the western Indian Ocean (Internet, July, sharks and rays was 314.367 MT. In 2011-2012 periods, 2011). Distribution by depth strata rays ranges as follows: H. undulata contributed 0.23% (0.882 MT) of the total 10-20 m-899, 20-50 m-71, 50-80 m 08, 80-100 m-2, Av landed (382.670 MT) shark and ray species. During 10-100-214. According to the F/V Jalwa survey, the 2012-2013, the total landing of sharks and rays was highest however was not confirmed by any of the other 362.406 MT, on which landing amounts of H. undulata surveys (Lambeouf, 1987). was 0.434 MT or 0.12% (Table 1). The species has a disc width of 140 cm, while its size at birth is 20 cm DW (White et al., 2006); however, it has Month wise a diamond-shaped disc with rounded corners and a projecting, pointed snout. Its tail is long and whip like During July, 2009 to June, 2010, the month wise total without fin folds. Adults have a striking dorsal color landing volume of H. undulata was recorded as 0.140 MT pattern consisting of large, dark brown rings and in the month of July, 2009 and in March, 2010 the total reticulations delineated by thin yellow lines, while landing was 0.420 MT. In July, 2010 to June, 2011 juveniles have a pattern of large dark spots. Mating period, the total landing amount was 0.218 MT in the season occurs in the winter. In the years 2009-2010, month of November, 2010 followed by 0.400 MT in 2010-2011, 2011-2012 and 2012-2013, a total number of January, 2011 and 0.275 MT in May, 2011. During July, 158 H. undulata were landed and their total weight were 2011 to June, 2012, the total landing was 0.350 MT in the recorded as 2769.0 kg from these landing centers.