Discovering a species that is completely new to science is always exciting, so we're excited to get involved in two new six-gill sharks (known as maxillary sharks and maxillary sharks) found off the coast of East Africa.
Very little is known about sawsharks at the moment. So far, only one species of six-gill shark has been found. But we know that sawsharks are carnivores, feeding on fish, crustaceans and squid. They kill their prey with their jagged beaks, then quickly cut them left and right, tearing them into small pieces.
Sawsharks look a lot like sawfish (actually rays), but they're much smaller. Sawfish can reach a body length of about 1.5 meters, while sawsharks can reach a body length of up to 7 meters, in addition, they also have tentacles that sawfish do not have. The gills of the sawfish grow on one side of the head, while the gills of the sawfish grow under the body.
Together with our colleagues, we discovered these two new species of sawsharks while studying small fisheries off the coast of Madagascar and Zanzibar. While the discovery of these extraordinary and intriguing sharks is a miracle in itself, it also highlights how much biodiversity remains unknown in coastal waters around the world, and how vulnerable it may be to poorly monitored and mismanaged fisheries.
Fishing in the dark
Although their names may imply that small-scale fisheries employ 95% of the world's fishermen and are a very important source of food and funding, especially in tropical developing countries. In some of the world's most important biodiversity hotspots, such as coral reefs, mangroves and seagrass beds, these fisheries are usually close to the coast.
For most small fisheries, there is very little information about their fishing efforts, that is, how many fishermen there are, where, when, how they fish, and what exactly they catch. Without this, it is difficult for governments to develop management plans to ensure sustainable fishing and to protect ecosystems and the livelihoods of fishers and the communities that depend on them.
While small-scale fisheries in East Africa and nearby islands are not well documented, we do know that at least 500,000 small-scale fishermen use more than 150,000 boats. A lot of fish to catch. While every fisherman and fishing boat may not catch as many fish per day, this number is really starting to increase because there are so many fishing boats in operation. Many people use nets — either floating nets floating on the surface of the sea or stinging gill nets close to the seabed. Both methods are cheap, but they are not very picky about the prey caught. Some people use longline fishing, which is effective in catching big fish, including sharks and rays.
In 2019, our team reported that the fishing record significantly underestimated the number of sharks and rays caught in East Africa and nearby islands. With the discovery of two new species – a global hotspot for shark and ray biodiversity – it has become more urgent to properly assess the impact of small-scale fisheries on marine life.
How many unidentified sharks and other species are caught in these fisheries? Species are in danger of extinction before they are discovered.
Efforts to monitor and manage fisheries in the region and globally must be expanded to prevent the loss of biodiversity and the development of sustainable fisheries. There are some simple methods that can be used on small boats that currently lack surveillance, including using cameras to record what is captured.
The two newly discovered sawsharks also demonstrate the value of scientists' collaboration with local communities. Without the involvement of fishermen, we may never have found these animals. From simple assessments all the way to developing ways to change the amount of fishing and manage fisheries, our goal is to make fisheries sustainable, to protect the long-term future of species like sawsharks, to protect the ecosystems in which they live, and the communities that have depended on them for generations.