Shark Census

This project is aimed at developing a baseline of shark distribution and abundance at dive sites in the Marine Protected Areas of the region. To this end, the Migramar network is developing a unique partnership with dive guides, who spend countless hours underwater each year, and as such, are keenly aware of the changes in shark abundance.

Over the last decade, there has been a growing concern that shark populations around the world are declining due to overfishing. According to Bonfil (1994) [1], 50 % of world shark catches are as bycatch, and do not appear in official landing statistics, so the reported catch of 760 000 t in 1996 is probably closer to 1.5 mt. Industrial and artisanal longline and seine fleets are largely responsible for these declines.

The Shark Census Project team.

Lack of information has masked declines in shark populations which are only now being brought to light. Whereas in many areas, stock assessments are based on catch data from industrial vessels, such ANALYZEs are not possible in the protected areas of Galapagos, Cocos and Malpelo, where industrial fishing is banned, and sharks are fully protected. It is therefore necessary to find alternative indicators of abundance.

The obvious choice is to work with dive guides. Dive guides are experienced, they have an innate awareness of the marine life around them, and they spend many hours underwater each year. They are deeply concerned about a perceived drop in shark numbers over the last decade, and committed to maintaining current populations, which attract tourists from all over the world.

Training

In December 2007, a workshop involving shark researchers from all over the Eastern Tropical Pacific was carried out in the Galapagos Marine Reserve, in order to develop a standardised technique for identifying, counting, and estimating the size of sharks. A shared database was developed as an online tool, and training of local dive guides began in early 2008.

Specially trained dive guides become excellent collaborators, adding newly acquired skills to their years of experience in maine protected areas.

Cut-out sharks of different sizes were built and used in underwater training exercises to determine the range of size estimates at different distances between divers and sharks.

Dive guides are asked to carry a small PVC armband on which they can note down shark abundance per species, sex and size of individual sharks, and physical aspects of their dive (dive time, currents, visibility, depth and position of thermocline).


[1] Bonfil R 1994. Overview of the world elasmobranch fisheries. FAO Fisheries Technical Paper 341, Rome. 119 pp.