Huge quantities of sharks and rays being caught by fisheries in Tunisia

The Gulf of Gabes lies on the east coast of Tunisia and supports many small scale fisheries. Here artisanal fisheries commonly set trammel nets to catch shrimp (Melicertus kerathurus) from May to August each year. Now a team of researchers has been researching the impact of these fisheries on the local shark and ray populations.

The scientists, based at Institut National des Sciences et Technologies de la Mer in Tunisia, spent 3 months recording the number of elasmobranchs caught in fishing nets of the artisanal shrimp fisheries in the Gulf of Gabes. They took note of species, sex and total length (or disc width in rays).

In total 926 elasmobranchs were caught during this 3 month period; the overwhelming majority of the sharks and rays caught was made up by the common smooth-hound (Mustelus mustelus) but six other species (blackspotted smooth-hound (Mustelus punctuatus), common stingray (Dasyatis pastinaca), marbled stingray (D. marmorata), common torpedo ray (Torpedo torpedo), sandbar shark (Carcharhinus plumbeus) and spinner shark (C. brevipinna)) were also retrieved. Despite the fact that the sheer numbers of elasmobranchs caught in 3 months is fairly jaw dropping, what's really shocking about the results is that all of the captured sharks were either neonates or juveniles.

Removing immature specimens from a population can have huge implications for conservation owing to the fact that the organisms in question have not had the opportunity to reproduce. This is especially true for sharks who tend to have slow growth, low fecundity and long reproductive cycles making it difficult for most species to recover their stocks once depleted. The results here led the researchers to believe that the Gulf of Gabes might be an important nursery area for several species of elasmobranch.

Whilst large commercial fisheries are barred from many marine protected areas, small scale artisan fisheries are often permitted to operate. Recently there has been more attention paid to the impact of these smaller fisheries with the result that some marine protected areas are prohibiting all fishing activity within their waters (see The Shark Post: New marine sanctuary in the Galapagos will protect a variety of shark species).

Studies such as this are critically important as they provide scientists with the evidence to convince policy makers that key areas need protecting either by closing fisheries or creating a marine protected area. Considering that one of the above species is listed as Near Threatened in the IUCN Red List and two as Vulnerable (including the most commonly caught common smooth-hound), protecting elasmobranchs in this region should be of high importance.

Saidi, B., Enajjar, S. and Bradai, M. N. (2016), Elasmobranch captures in shrimps trammel net fishery off the Gulf of Gabès (Southern Tunisia, Mediterranean Sea). Journal of Applied Ichthyology. DOI: http://dx.doi.org/10.1111/jai.13061