Five new fish species found in Sundarbans

Five new species of fish have been found in the Sundarbans of Bangladesh. Among them, one was discovered for the first time in the world. This discovery has brought the number of fish species in the largest mangrove forest up to 322.

This discovery was made in a two-year study conducted on fish biodiversity and its conservation status in the aquatic habitats of Sundarbans.

The research was carried out by the fisheries biology and genetics department of Sher-e-Bangla Agriculture University in association with the country’s forest department. South Korea's ocean science and technology institute assisted in the research. The research report was published in the Journal of Threatened Taxa on 26 January. 

Fish samples were collected from the main rivers of Sundarbans including Baleshwar, Shibsha, Pashur, Shyala, Kalindi, and Kholpetua between June 2015 and July 2017. Samples were also collected from areas that are inundated during tides in Khulna, Bagerhat and Satkhira. Fishes were collected from local markets too.

The species of the fish were determined after a comparison with the information with the international gene bank following a DNA barcoding system, said Kazi Ahsan Habib, head of the research team and professor of fisheries biology and genetics at Sher-e-Bangla Agriculture University. DNA barcoding has been used for first time for surveying Sundarbans fish diversity, he said and added that, in the traditional method, researchers generally identify the name and species of a fish according to its structure and appearance, but changes of external characteristics due to life cycle changes make it difficult.

The International Union for Conservation of Nature (IUCN) publishes the updated list of world biodiversity which is known as the Red List. Among the latest surveyed fish species 13 were nearly extinct, 10 threatened and eight endangered, according to the latest Red List.

The barcoding system used to identify the fish species has added a new dimension to Sundarbans biodiversity research, said Raquibul Amin, country representative of IUCN in Bangladesh. He said the study will contribute in the plan to save the forest’s biodiversity.

The research also noted that a 1994 IUCN study conducted in the Sundarbans, Bangladesh found 177 fish species while a FAO project surveyed the number as 196 in 2001. No large-scale researches were conducted over fish diversity at Sundarbans since then. In 2015, the IUCN Red List identified 64 among 153 local fresh water fish species in the country endangered.

Five new species
The scientists have found five new fish species along Alorkol area of Dublar Char adjacent to Bay of Bengal.

Mustelus mosis: Body colour reddish-grey above and dull white ventrally. Small sized shark, with an elongate and slender body; snout markedly pointed and long. Mouth triangular, with well-developed labial folds. Skin fairly smooth.

Lagocephalus guentheri: Colour of dorsal side of the body is brown with several dark bands crossing over the back; a silver-white band running on the side of the body was found in the holotype. The dorsal fin dusky. The caudal fin dark brown or almost black with the dorsal and ventral white tips. The pectoral and anal fins pale. Body stout and small sized fishes, covered with small spinules on back, abdomen and throat; caudal fin rounded.

Carangoides hedlandensis: Body color bluish-green above and silvery white below; dorsal fin dusky; filamentous soft rays black, soft dorsal fin yellow; pectoral and anal fins silvery; caudal fin yellowish green; pectoral fin dusky. A black opercular spot present. Body strongly compressed and very deep. Eye diameter about equal to or larger than snout length. Central rays of dorsal and anal fins elongated. Scales small; breast naked. Lateral line anteriorly with a moderate regular arch.

Uranoscopus cognatu: Body colour grayish above and minute black dots on upper third body; sivery below; opercle golden. Body compresses; anterior moderately and posterior deeply. Head flat above. Caudal fin slightly emarginated. Lateral line absent. Scales ctenoid.

Chelonodon bengalensis: Named after the Bay of Bengal. Skin is blackish and net like marks on the back. This species has not been found anywhere else in the world.

*This report, originally published in Prothom Alo print edition, has been rewritten here in English by Nusrat Nowrin.