Edgardo Ernesto Di Giacomo

Identification of Egg-Laying Areas for Chondrichthyan Fishes in a Coastal Zone of San Matías Gulf, Northern Patagonia, Argentina

Diving process.

Egg case with embryos.

Separated from the contiguous continental shelf, San Matías Gulf (41°– 42°S; 64°– 65° W) is one of the most conspicuous Patagonian marine environments. This gulf is a relatively isolated ecosystem. In its waters, a small-scale trawl fishery has been developing since 1971. The target species is the hake, Merluccius hubbsi; nevertheless, 18 skates, 11 sharks and 1 holocephali species are captured as bycatch. These species are key components of their marine ecosystem and are also particularly vulnerable to fishing pressure. In recent years, 33% of these species were included in various IUCN Red List categories. Besides the risk of extinction of some species, a further concern is the ecosystem impacts that may result from the strong depletion of their populations.

The northern region of San Matías Gulf has been identifed (1st. Rufford results) as a sensitive area for the conservation of these species. Here is where the highest concentrations of the holocephalan, Callorhinchus callorhynchus,occur. In the departures during the 2nd. Rufford was possible to found eclosed egg cases of ray, Sympterigia acuta and one capsule with live embryo inside in the intertidal zone. Until now no eggs capsules of these species were found in coastal waters by diving. The location of a possible spawning area of this species will contribute to the development of conservation plans and fishery management politics of these species highly vulnerable.

The growing concern about the fishing exploitation level of chondrichthyan species expressed by international organisms like FAO and IUCN is directly related to their vulnerability as fishing resources. In the last years, many cases of overexploitation and even local extinctions of some of these species have been detected. Being able to identify and to delimit the egg-laying areas for the cockfish and skates, as well as to register the presence of individuals recently hatched, will be essential to develop specific management plans. These could include the closure of areas during the reproductive season in order to protect the growth of embryos within egg cases and the newborns from human activities. The estimation of biological parameters such as fecundity and predation mortality will help to design management plans for the local fishery that ensure the conservation of the resource. Beyond the local impact, the information obtained will be incorporated into national and international data bases to make it available to the scientific community and to fisheries administrations. Information will also be published in local magazines and journals in order to raise community awareness of the research activities and the need for care of natural resources.

Read about Edgardo's previous work in the Golfo San Matías http://www.ruffordsmallgrants.org/rsg/projects/edgardo_ernesto_di_giacomo or for more information contact edgardodigiacomo@gmail.com or visit www.condros.com.ar