Shark Week 2019

Shark Fisheries in the Western Indian Ocean Are Headed for Deep Water

A shortfin mako shark landed in Tanzania. ©Mike Markovina

By Rhett Bennett
July 31, 2019

Across the Western Indian Ocean (WIO) there is a large contingent of artisanal fishers who fish near the coast. They use a diverse range of simple but effective fishing gears — handlines, longlines, monofilament gillnets, and even baited monofilament gillnets — all of which have an impact on shark and ray species.

Owing to overexploitation in these artisanal fisheries, as well as commercial and industrial ones, 27% of shark and ray species in the WIO are now classified as threatened (Critically Endangered, Endangered or Vulnerable) on the IUCN (International Union for the Conservation of Nature) Red List of threatened species.

Most of these fisheries are also unregulated and their catches are largely unmonitored. This lack of fishery data, combined with significant gaps in our knowledge of the animals’ biology and ecology, prevents improved management.

A fisher deploys a monofilament gillnet in Tanzania. ©Mike Markovina

WCS (Wildlife Conservation Society) has thus initiated surveys of artisanal fishers’ catches at landing sites in Madagascar, Kenya, Tanzania and Mozambique, in order to quantify the impacts of these fisheries on shark and ray species.

“27% of shark and ray species in the Western Indian Ocean are now classified as Critically Endangered, Endangered, or Vulnerable on the IUCN Red List of threatened species.”

So far, we’ve seen that artisanal fishery catches comprise a large proportion of sharks and rays, including several highly threatened species, such as zebra sharks, great hammerhead sharks, and bottlenose wedgefish. Zebra sharks and great hammerhead sharks are classified as Endangered on the IUCN Red List and, as such, are “considered to be facing a very high risk of extinction in the wild.”

Wedgefishes have recently been reclassified as Critically Endangered, and thus their risk of extinction is considered extremely high. The fins of these shark-like rays fetch some of the highest prices in the shark fin trade, making them highly sought after globally. Consequently, wedgefishes are now considered the most threatened marine fish family globally (including sharks and rays).

A zebra shark caught in a monofilament gillnet in Madagascar. ©Regis Andriamisoma/WCS

Our surveys also indicate that artisanal fishers are landing 13 of the 20 shark and ray species in the area that are listed by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), as well as five species that have recently been proposed for CITES listing. Considering that the artisanal fisheries are poorly monitored and that few (if any) of these catches are reported, the impacts of artisanal fisheries on these species are not currently being considered and the total catches of these CITES-listed species are being significantly underestimated.

In Kenya, catches include Critically Endangered bottlenose wedgefish (including juveniles), Endangered hammerhead sharks, and Vulnerable thresher and silky sharks. However, most sharks (and even most of the wedgefishes) are landed without fins, or these are removed soon after landing, indicating a valuable trade in these products.

In Tanzania, fishers in certain areas are targeting large pelagic shark species, such as mako, oceanic white tip, silky and thresher sharks, which are all threatened. Mako sharks were proposed for CITES listing in 2019, and have very recently been reclassified as Endangered on the IUCN Red List. More than half of the shark landings at some sites in Tanzania come from threatened species. At other sites, such as in Zanzibar, elasmobranch catches comprise almost exclusively rays, including inter alia wedgefishes and Endangered ornate eagle rays and manta rays, with very few sharks landed. This could mean that rays are being targeted in certain areas in response to shark declines.

“Our surveys indicate that artisanal fishers are landing 13 of the 20 shark and ray species in the area that are listed by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).”

In Mozambique, the most dominant shark species in the artisanal catches is the scalloped hammerhead shark, which is classified as Endangered and is currently listed by CITES. Of great concern is that nearly two-thirds of those caught are juveniles, meaning that they have not yet had an opportunity to reproduce.

There are also several threatened ray species being caught — the Critically Endangered whitespotted wedgefish and the Vulnerable reticulate whipray. The high proportions of juveniles in the catch, and the fact that pregnant females are also frequently landed, indicates that fishing is taking place in shark and ray nursery areas. This can have severe negative impacts on the population’s reproductive potential.

The finless, headless trunk of a bottlenose wedgefish landed in Kenya. ©WCS Kenya

In Madagascar, fishermen have told us that they’ve been forced to fish further offshore as the inshore catches have become depleted. Some fishers sail or paddle their pirogues up to six miles offshore to target hammerhead sharks, including pregnant females, at known aggregation sites. Dedicated targeting of these and other Endangered or Critically Endangered species is not sustainable.

Taken on the whole, it’s fairly obvious that shark fisheries in the WIO are heading for deep water, both figuratively as the stocks get into deeper trouble and literally as the fishers move further offshore and into deeper water in search of less exploited stocks.

“All is not lost. Governments in the WIO are starting to consider the plight of sharks and rays in new and updated management plans and regulations.”

All is not lost, though. Governments in the WIO are starting to consider the plight of sharks and rays in new and updated management plans and regulations. Seychelles, South Africa, and Mauritius have all developed formal national plans of action for shark and ray conservation. WCS is now assisting Madagascar, Kenya, and Tanzania in their attempts to do the same.

There is no overnight cure for overexploitation, particularly for shark and ray species. Sharks and rays tend to have slow growth rates, low reproductive rates, and long population recovery times. However, results from our surveys and those done by others are being used to inform policy development, species- and gear-specific regulations, and for the design of marine protected areas to improve protection of threatened chondrichthyans in these countries. Furthermore, this kind of positive support at the government level lays the foundation for a wave of change in shark and ray management and conservation across the region.

Dr. Rhett Bennett is the Western Indian Ocean Shark Program coordinator for the Wildlife Conservation Society.

Our Ocean, Our Future

Conserving and managing the marine biodiversity of our oceans is a monumental task that few countries have the capacity to do on their own. WCS is responding by investing in ocean protection, sustainable fisheries, and marine species conservation where the need is greatest

Wildlife Conservation Society

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WCS saves wildlife and wild places worldwide through science, conservation action, education, and inspiring people to value nature.

Our Ocean, Our Future

Conserving and managing the marine biodiversity of our oceans is a monumental task that few countries have the capacity to do on their own. WCS is responding by investing in ocean protection, sustainable fisheries, and marine species conservation where the need is greatest

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