Designing Marine Protected Areas for the South American Sea Lion (Otaria byronia) in the Argentine Patagonia.

摘要

This work looks into the conservation of South American sea lions (SSL), Otaria byronia by advancing a process of Marine Protected Area (MPA) design targeted for reproductive females during the first weeks of lactation. Focusing on protection of a single species may result in the establishment of a more comprehensive and ecologically functional system for management. SSL is distributed in the Atlantic and the Pacific coasts of South America. Along the coast of the Argentine Patagonian coast, 73 colonies were described, 42 % of which are reproductive. Breeding females give birth during the austral summer (January) and lactation lasts ca. one year. Critical to the annual cycle are the few weeks after birth, when mothers spend 2-3 days nursing and a similar or longer time at sea foraging, while pups remain alone on shore. Satellite tracking and dive recording instruments indicate that females are either coastal or pelagic in their feeding habits, but the latter travel relatively short distances from colony (mean 152 km). SSL are bottom foragers that dive to maximum depths of approximately 80 m. Optimizing travel and foraging time is critical for these animals, as pups left alone fast and are threatened by both starvation and being accidentally crushed by fighting adult males. Foraging areas overlap with fishing grounds, sea lions are caught in fishing gear and competition for food cannot be ignored. Yet, although 20 of the 31 existing breeding colonies are within coastal protected areas, none of the foraging areas have been considered for protection to minimize the consequences of interactions with fisheries. This work draws from very limited data to advance a process of design of Marine Protected Areas that is eminently practical, thus affordable to government wildlife administrators. I selected the most important colonies, based on location and abundance, integrated satellite locations at sea, analyzed potential associations with physical variables, and proposed criteria to decide important marine areas based on distribution at sea. Finally, I estimated the cost for fisheries to comply with the proposed conservation intervention scenarios. Foraging distribution did not follow a pattern consistent with physical oceanographic variables (sea surface temperature, productivity, bathymetry and seafloor composition) to guide conservation intervention. Bathymetry was the best proxy to help in the design of protected areas. Most of the conservation scenarios based on distribution at sea of lactating females did not strongly overlap with fisheries to justify conservation intervention. The colonies that did, however, involved the largest breeding colonies of Argentine Patagonia and Uruguay. In a context of closing the fisheries for the area of overlap and compensate for the loses during one month, I estimate a conservation cost of 2-3 million dollars, as the impact is on the most profitable of all Argentine Patagonian fisheries, targeting Argentine red shrimp, Pleoticus muelleri. I conclude that management that includes MPAs for this species requires a priori spatial planning considerations. Once a fishery is operational, the costs for conservation will not be affordable for the administrators. I identified some areas where an a priori approach would be practical, effective and feasible.