- Scientists have discovered a new species of shark found in the Indian ocean and have named it Planonasus indicus.
- It is a two-feet long, deep-sea shark found at a depth of 200-1000 metres under the sea.
- The shark was first spotted by scientists studying fish by-catch at the Kochi fishing harbour in 2008. After that, it was observed again in 2018 in Trincomalee in Sri Lanka, again as by-catch.
- Monitoring fisheries and by-catch is an easy and cost-effective method to study the diversity of marine animals.
On 26 April 2008, a never-before-seen species of shark arrived on the fishing harbour in Kochi. It was accidentally caught while fishing for economically important sharks from the deep-sea waters. The fishermen were not interested in this unfamiliar fish. However, when researchers from the Central Marine Fisheries Research Institute (CMFRI) came for their weekly observations of fish landings at the harbour, their curiosity was piqued.
The scientists examined the single sample in detail and then stored it at CMFRI. They also pointed out that the fish’s accurate taxonomic identity was unknown and similar specimens had been seen only twice before – from Socotra Islands, Gulf of Aden, in the northwestern Indian Ocean and the other from the Maldives.
A decade after the scientists found the shark in Kochi, it was caught again off Trincomalee in Sri Lanka on March 15, 2018. It was then that scientists from three countries, the USA, India and Germany, joined forces to understand what this fish was.
The first thing the researchers found was that the shark from Socotra Island was different from the two specimens found at Kochi and Sri Lanka. These two specimens were of the same shark and the researchers named it Planonasus indicus. The researchers could not access samples of the sharks seen at the Maldives, but they guess that it belongs to the same species. The researchers have published their findings in the journal Marine Biodiversity. Also, it turns out that the fish from Socotra Island, although slightly different, is part of the same genus and is called Planonasus parini.
Planonasus indicus is slightly over two feet long, dark brownish-black in color, and without any noticeable patterns (spots or stripes) on the skin. It belongs to the deepwater shark family Pseudotriakidae and is found under the sea at a depth of 200-1000 m. The name Planonasus refers to the shark’s flat, soft snout and ‘indicus’ refers to its availability in the Indian Ocean.
Though the researchers have learned quite a bit about the morphology and anatomy of Planonasus indicus from the Indian and Sri Lankan samples, their understanding “would improve greatly with additional material from different sexes and size classes,” write the researchers in their paper. They also say that “the species appears to be rare and opportunities to obtain additional material are extremely limited.”
Therefore, the researchers felt compelled to describe the species based on the information they had and hope that their work will increase awareness about this species and will help them access more specimens in the future.
About 88 species of sharks are known from India and Planonasus indicus is just one of them. Several more are “out there waiting to be discovered in Indian waters,” said K.V. Akhilesh, a scientist at CMFRI and one of the authors of the present study. Deep-sea sharks are particularly hard to study because specialised exploratory vessels, dedicated to exploring these organisms, are needed.
“India’s only deep-sea fishery survey vessel is FORV [Fishery Oceanographic Research Vessel] Sagar Sampada,” said Akhilesh. Though many new species have been discovered based on its collections, there are challenges in using its facilities. “The vessel was bought in 1984 and it is time now to acquire new high-class vessels. Additionally, getting a confirmed research survey berth is quite tough as many institutions are requesting for the same,” he added.
The other way to study these deep-sea animals is to depend on fishing vessels and their catch. Studying sharks that are landed by fishing vessels, while not charismatic or a happy sight at all, is “fairly easy and requires minimal finance and logistics at [the] site,” said Dipani Sutaria, an ecologist studying marine animals in India.
The discovery of Planonasus indicus is itself a testimony to how new species can be discovered by studying fish landings on harbours or by going on fishing trips. As Indian fisheries expand to newer and deeper areas, we can expect to find more unknown species feel both Akhilesh and Sutaria.
“India’s commercial fishery is widely monitored by the CMFRI and many new species discoveries have been made by monitoring the fish landing on the harbours,” said Akhilesh.
The expansion of fisheries, however, also means increased threats to the fishes. Sharks, particularly because of their low rates of population growth, are severely threatened by overfishing and habitat destruction. Even Planonasus indicus, both in India and Sri Lanka was caught by fishing vessels looking for another group of deep-sea sharks called Gulper sharks, belonging to the family Centrophoridae. The Gulper sharks are prized for their liver oil and meat and therefore are overfished and endangered.
“Several Indian shark species, such as river shark, sawfish, shovelnose ray, etc. have gone missing or appear in reduced numbers in regular monitoring programs. These were once very common along the country’s coastal waters,” said Akhilesh.
As the numbers dwindle, our chances of getting to study these animals in the wild and their role in the trophic system will reduce drastically. There is an immediate need to scale up our efforts in studying sharks and other related animals.
“Our island systems – Lakshadweep and Andaman Nicobar – if kept free from mechanised commercial fisheries, will be the perfect places to study and conserve sharks,” said Sutaria. “We can still manage these island systems from being overfished, it is not yet too late, and the government needs to think about this seriously. We should not be allowing trawlers, purse seiners and long lines in these island systems,” she added.
Banner image: A lateral view of the new identified species of shark, Planonasus indicus. Photo by Marsha Englebrecht.