WFD 2022: Protect Aquatic Biodiversity for Fish to prosper

(Feature image: Fish species caught in small Ramganga stream in Pauri Garhwal. Bhim Singh Rawat/SANDRP)

On the occasion of World Fisheries Day (WFD) 2022, this report by SANDRP tracks developments related to aquatic biodiversity in India over the last year.  The first, second, third and fourth parts of the WFD 2022 reports covered positive reports on rivers’ fish and fishermen; mass fish deaths in rivers and emerging threats; mass fish kills in lakes, ponds in the country and issues concerning rights & livelihoods of inland & coastal fishers reported during the past one year.

AQUATIC BIODIVERSITY ISSUES

‘Big golden mahseer to small kudremukh barb, freshwater fish are richly diverse’ Vidyadhar Atkore is a landscape ecologist at SACON. He discusses river biodiversity facing human impacts. He also emphasises need to remove obsolete dams. He says less ecological information is available about riverine systems.

His masters study was about fish community of the Corbett National Park. Doctoral study was about four major river basins: Malprabha, Mhadei, Tunga and Bhadra in Karnataka, covering over 152 riverine stream landscapes. Tunga and Bhadra were less modifies then Mhadei and Malaprabha. He describes the challenges in riverine research. https://timesofindia.indiatimes.com/big-golden-mahseer-to-small-kudremukh-barb-freshwater-fish-are-richly-diverse/articleshow/89510523.cms  (12 Feb. 2022)

Goa Cacra fisherman finds a seahorse in his Zuari bay catch A tiny seahorse netted on March 4 2022 by a fisherman off Cacra in the Zuari bay has triggered interest among fisheries scientists, as they are rare visitors to Indian waters from far east. The seahorses (hippocampus) — hippo in Greek means horse and kampos monster — swim upright like razor fish and very few are found in Indian waters. A juvenile barely three and half to four inches was found in the catch at Nauxi by Sanjay Pereira, a fisherman from Cacra. “We found it on the rocky strata in Nauxi and it was alive in the net,” he said.

An earlier paper co-authored by Sushant Sanaye, Rakhee Khandeparkar and other NIO scientists had recorded at Britona the four specimens — of 47.3mm to 60.1mm in length — as the first records of Japanese seahorses (Hippocampus mohnikei) in Goan waters. The seahorses are one of the slowest swimmers among fish and their journey from the far east to Indian waters over thousands of kilometres has amazed scientists.

The first Indian record of H mohnikei was found along Tamil Nadu coast in 2007. But it was based only on a morphological study. The Japanese seahorse was compared with two out of ten species found in India, H kuda and H trimaculatus and found to be shorter than them. H mohnikei are much darker, but being experts in camouflage, they are known to change colours. But scientists didn’t rule out the possibility of the tiny creatures colonising in their new habitat. “The issue of whether they have already adapted to their habitat after arriving as vagrants needs to be studied,” a scientist said. https://timesofindia.indiatimes.com/city/goa/scientists-intrigued-as-cacra-fisherman-finds-a-seahorse-in-his-zuari-bay-catch/articleshow/90021719.cms  (06 March 2022)

Much-loved ‘khube’ resurface in Chapora after over 15 yrs Goa’s marine biodiversity is witnessing a rejuvenation in the river ecosystems. After certain varieties of shellfish made a comeback in the Zuari and Mandovi rivers during the pandemic, the Chapora river is the latest in this list to throw up a pleasant surprise. Over the past two months, hundreds of people have been flocking to the Chapora river for ‘khube’ (byvalves/ clams), which locals say last surfaced 15 years ago. https://timesofindia.indiatimes.com/city/goa/goa-much-loved-khube-resurface-in-chapora-river-after-over-15-years/articleshow/88700845.cms  (05 Jan. 2022)

Maharashtra Fishermen net Stingray weighing over 100 kg Two brothers from the Bhatebunder in Uttan netted a giant stingray fish (locally known as pakat-maasa) while inshore fishing in the Arabian Sea. Sunil and Raju Patil had ventured on their fishing voyage in their small engineless oar-powered fibre boat and cast their net like normal days. A few hours later, they noticed the stingray that had gotten entangled in the net. After tediously labouring the oars, the duo managed to bring their small boat loaded with the catch to the shores of Bhatebunder. https://www.freepressjournal.in/mumbai/mira-bhayandar-fishermen-net-stingray-weighing-over-100-kg-in-small-rowboat-in-uttan   (03 Nov. 2022)

Caught in fishing nets, sea snakes are dying along the Malvan coast In a recent study, marine biologists forewarn a decline in sea snake populations at the Malvan coast, a major landing port in southern Maharashtra. The authors flag that mechanised vessels are likely to be the main cause of this decline.

“Sea snakes play an intermediary role in the ecosystem. They are prey and predators of marine fauna,” informed Chetan Rao of Dakshin Foundation, Bengaluru, and lead author of the study. Marine snakes are geographically widespread species that are critical to reef and coastal ecosystems in tropical and subtropical waters of the Indian and Pacific oceans. Their removal from the system could warp the trophic balance, Rao added. Being predators, they feed on various herbivorous marine fauna but are mainly piscivores (fish eaters). Sea snakes control the fish populations, preventing over-consumption of planktons and keeping the balance. https://scroll.in/article/1015304/caught-in-fishing-nets-sea-snakes-are-dying-along-the-malvan-coast-of-maharashtra  (19 Jan. 2022)

Karnataka The last clams of Aghanashini Non-sustainable harvesting has not only eliminated the bulk of bivalve resources, an indicator of richness of overall biodiversity of the Aghanashini estuary but also resulted in the migration of clam diggers to urban areas to work as construction labourers or employees in cashew factories and hotels. While the mollusc (meat) was used for dishes, its shell was used in various industries including limestone, paint, chemical, poultry, pharmaceuticals among others, as a rich source of organically sourced calcium. This demand resulted in the unabated collection of clams from mud beds of the river and the sea. Along with traditional clam digging, where collectors would dive deep (at least 10 to 12 ft) into the sea or river during low tide, mechanised clam mining also began at the estuaries, which resulted in the fast depletion of bivalves.

Kali estuary of Karwar and Sharavathi estuary of Honnavar, in the past, were also good centres of various bivalve species. Most of them witnessed a serious decline due to the construction of large hydroelectric projects upstream, which made serious habitat changes, notably for estuarine bivalves and fish, on account of dam-related freshwater releases upsetting natural habitats and salinity decline.

“A similar situation prevailed in the Ashtamudi estuary of south Kerala, once known for rich fishery and clam bivalve production. Under the initiative of WWF, India, the Central Marine Fisheries Research Institute and the Kerala State Fishery Department the fishing community organised and adhered to the norms of sustainable fishery, involving restricting the number of fishing days per week, limiting the family-wise harvest quota, and the minimum size of clams to be collected. These steps ensured clam fishery recovered and reached annual sustainable harvests of about 10,000 tonnes per year, of standard size clams, which fetch premium market prices,” he said.  https://www.deccanherald.com/science-and-environment/the-last-clams-of-aghanashini-1061324.html  (16 Dec. 2021)

West Bengal Endangered fish diversity up in Ganga Fish diversity studies in the river, conducted over the past five decades, reveal a wave-like curve: 207 species in the inaugural study in 1974, rising to 266 in 1991 before witnessing a precipitous decline to just 140 species in 2012 and then making a smart recovery to 190 in 2021. The diversity study has been conducted along the main channel of the Ganga, not its tributaries and distributaries.

The improvement in fish diversity and population follows multiple initiatives taken by CIFRI, including ranching and seed production of indigenous Gangetic fish species. Over 47 lakh fingerlings of major Indian carps have been ranched. The decline between 1991 and 2012, CIFRI scientists said was due to deterioration in the river’s water quality because of effluent from civic bodies and industries, and overfishing. But species like pangasius, pabda catfish, giant river goonch, chitala and silond catfish are less abundant in the river and require more effort. https://timesofindia.indiatimes.com/city/kolkata/west-bengal-endangered-hilsa-kajri-vacha-back-fish-diversity-up-in-ganga/articleshow/91928722.cms  (01 June 2022)

Decline in Hilsa catch In 2021, fishermen in West Bengal could catch only around 6,170MT of Hilsa. The catch has been going down over the years. In 2011, Hilsa catch was around 16,500MT. It went down below 10,000MT over the next three years. In 2017, around 26,000MT of Hilsa was caught, the highest haul in recent times. In 2020, during the Covid-19 pandemic, it went down to 2,085MT, the lowest in recent years.

There are multiple factors ranging from unbridled fishing, pollution, rainfall, decreasing depth in rivers because of siltation and river flush around this time of the year, among others. “They are very sensitive to subtle changes. They would migrate from sea to rivers to breed and would swim in that direction where they get favourable conditions. If they don’t find suitable conditions in River Hooghly in West Bengal, they enter the Meghna-Padma estuary in Bangladesh,” said Shyamsundar Das, joint secretary of West Bengal United Fishermen Association. This year too, the catch has been meagre as a result of which prices have soared. https://www.hindustantimes.com/cities/kolkata-news/wb-fish-traders-request-bangladesh-govt-to-send-2000-mt-hilsa-in-festive-season-101662104676424.html  (02 Sept. 2022)

OTTERS Some basic information World Otter Day is celebrated on the last Wednesday of May every year. Otters keep a check on the population of other aquatic species and signify clean rivers that are free of pollutants. The absence of fish ladders during dam construction is also a contributing factor as it decreases the prey base for otters, impacting local populations. Additionally, water pollution due to pesticide runoff impacts the otters and the fish they prey on. https://www.natureinfocus.in/animals/10-things-you-need-to-know-about-india-s-otters  (04 Oct. 2021)

FISHING CAT Researchers’ proposals to save fishing cat Researchers across the fishing cat’s range are working to save the elusive wetland-dwelling cat, which is declining due to habitat loss and conflict with fishers. https://www.thethirdpole.net/en/nature/fishing-cat-in-troubled-waters/  (20 Oct. 2022)

GANGES DOLPHIN Involvement of communities could help mitigate threats to Ganges dolphin River pollution, dams and indiscriminate fishing are among the threats to the Ganga river dolphin. The fishing community could play an important role in conserving the dolphins in Ganga but there are several challenges such as delayed pay and lack of official recognition of their role. There are various projects by the government to protect the national aquatic animal and transboundary cooperation could help further the species protection in the region. https://india.mongabay.com/2022/08/involvement-of-fishing-communities-transboundary-cooperation-could-help-mitigate-threats-to-ganges-river-dolphin/  (03 Aug. 2022) Janaki Lenin The deliberate killing of these aquatic mammals may have declined, but inadvertent drowning in fishing nets alarmingly continues. https://www.thehindu.com/sci-tech/energy-and-environment/the-day-of-the-dolphin/article38378995.ece  (05 Feb. 2022)

Uttar Pradesh Study on dolphins, hilsa in Ganga The government will now study the life cycles of dolphins and the hilsa population in the Ganga to ascertain the health of the holy river at different sections, a senior NMCG official said. He said for the last four years, around 190 fish species have been recorded from the river which provides livelihood and economic sustainability to the fishers residing in the banks of the river. https://www.business-standard.com/article/current-affairs/govt-to-study-dolphins-hilsa-in-ganga-to-ascertain-river-s-health-122061100217_1.html  (11 June 2022)

MUD SKIPPERS Tamil Nadu Mudskippers spotted at Ennore estuary Almost every weekend, two youth in the city spend their evenings ‘herping’ at Ennore estuary. Since last year, more than their interest in usual reptiles, the duo have found a new amphibious fish, mudskippers, more interesting. They are found only in a few estuaries and mangroves unlike other fish and amphibious species, says Aravind Manoj, a techie. He and his his friend Sudharshan Kuselan are attempting to document mudskippers and their habitats. The duo has been in touch with academicians, who research on the species. They have spotted five species of the reptile during their weekend ‘herping’.

“We were actually looking for the dog-faced water snake in Ennore and that was when we chanced upon the mudskippers. Initially, we were surprised to see the species and had several questions about them. So, I looked for more information about mudskippers and got to know they are rare and are found only in estuaries and mangroves.” They have taken images and are comparing notes with academicians researching mudskippers.

G. Mahadevan, Research Associate in Centre of Advanced Study in Marine Biology in Parangipettai, part of Annamalai University, says 13 mudskipper species are found in India. “My doctorate was in mudskippers and I have surveyed them in estuaries along with entire east coast and up to the Sunderbans. In Tamil Nadu, they are found near Ennore, Pichavaram and Muthupettai.”

Mudskippers are said to be ‘pollution indicators,’ Mr. Mahadevan says. “When the pollution level in that locality rises, some studies suggest that the mudskippers move elsewhere. Since they burrow, they are believed to benefit the entire mangrove ecosystem.” He said he has read reports of mudskippers, located from Gujarat in the north and up to Karnataka in the South on the west coast. https://www.thehindu.com/news/cities/chennai/mudskippers-spotted-at-ennore-estuary/article38338767.ece  (28 Jan. 2022)

RESEARCH

NEW FISH SPECIES Nagaland Scientists discover new fish species A dead fish specimen collected from a fisherman’s net in the Dikhu river turned out to be a new fish species- Pethia dikhuensis to science. It was not as easy as it looks. Pethia dikhuensis is currently known only from the Dikhu River, a tributary of the Brahmaputra, in the Mokochung district of Nagaland. Pethia dikhuensis is unique among all species of barbs because the male fish of this species have reddish-orange fins and bodies. The new fish is consumed by locals but also possesses a good ornamental value due to the attractive colour.

The genus Pethia are small sized-fishes (5-8 cm) commonly called ‘barbs’. These fish are endemic to the Indian subcontinent and Myanmar. A total of 38 valid species of Pethia genus are known to occur in India and its bordering countries, of which 18 species occur in the northeastern states and Bangladesh.

“Last year a small miniature catfish called Pseudolaguvia vespa was also discovered by our team. The discovery of P. dikhuensis suggests that the streams and rivers of this region may harbour many more undescribed species of fish, and therefore deserves increased survey efforts,” J. Praveenraj, a scientist at the Division of Fisheries Science, ICAR-Central Island Agricultural Research Institute, Port Blair, who identified the new fish species said.

Nagaland is drained by 11 major rivers, which are tributaries of the larger Brahmaputra River system. The rivers of Nagaland are relatively less explored compared to other North Eastern states. The fish fauna of this region is poorly studied and this team is taking efforts to explore, discover and describe new species from this region. https://www.eastmojo.com/nagaland/2022/10/05/scientists-discover-new-fish-species-in-nagaland/  (05 Oct. 2022)

NEW EEL SPECIES Scientists discover new eel species A group of Indian scientists have discovered a new species of eel from among specimens collected from the Kalamukku and Digha Mohana fishing harbours in Kerala and West Bengal respectively. Their study was published in the Journal of Fish Biology March 30, 2022. The newly discovered eel belongs to the Congrid eels group and has been named Ariosoma indicum. The term Indicum means that it was found in India, Anil Mohapatra, senior scientist with the Zoological Survey of India’s Gopalpur-on-Sea centre and co-author of the paper said. https://www.downtoearth.org.in/news/wildlife-biodiversity/scientists-discover-new-eel-species-from-kerala-bengal-82475  (20 April 2022)

Tamil Nadu New species of estuarine crab discovered Researchers have discovered a new species of estuarine crab at the mangroves of Parangipettai near the Vellar River estuary in Cuddalore district. The species has been named Pseudohelice annamalai in recognition of Annamalai University’s 100 years of service in education and research. “This is the first ever record of this genus, Pseudohelice, collected from high intertidal areas in front of the CAS. So far, only two species — Pseudohelice subquadrata and Pseudohelice latreilli — have been confirmed within this genus. The species discovered is distributed around the Indian subcontinent and the eastern Indian Ocean,” says S. Ravichandran, Associate Professor, CAS.

“Specimens of Pseudohelice annamalai were collected from the high intertidal areas of the Vellar River estuary, Parangipettai, with sediments composed of mud and sand. The mangroves in the habitats were artificially planted on five hectares along the northern bank of the river, with two distinct zones —  Rhizophora spp. towards the estuary and  Avicennia spp. towards the land in the intertidal area. The recent discovery was the first-ever record of this species,” the researchers said.

This species is not aggressive and can move fast like other intertidal crabs. As many as 17 species of intertidal crabs have been recorded in the same region,” Mr. Ravichandran added. The occurrence of Pseudohelice in India links the distribution gap between the western Indian Ocean and the western Pacific Ocean. The new species provides additional evidence of the geographic isolation of the eastern Indian Ocean for some marine organisms, the researchers said.  https://www.thehindu.com/news/national/tamil-nadu/new-species-of-estuarine-crab-discovered-in-cuddalore-named-after-annamalai-university-centenary/article66110524.ece  (08 Nov. 2022)

By-catch-associated demographics of 2 threatened seahorses from south-east coast of India Abstract: -Seahorses comprise a charismatic, high-value and high conservation-concern group of fishes, whose demographics, including the dynamics of populations, are poorly studied. In this paper, we fill this key knowledge gap by determining the population dynamics of two threatened species, Hippocampus kuda and H. trimaculatus, from the south-east coast of India using samples encountered in trawl by-catch. Hippocampus kuda showed a comparatively greater asymptotic length, whereas H. trimaculatus had a greater growth coefficient and growth performance index. Demographic parameters of the two threatened seahorses indicated that even as ‘incidental catch’, these species are vulnerable to overfishing, and species-specific conservation guidelines need to be developed and their on-ground implementation and enforcement ensured. https://www.publish.csiro.au/MF/MF21127 

Bhim Singh Rawat (bhim.sandrp@gmail.com)