The Gulf Corvina
A thriving fishery on a fishing aggregation in the Upper-Gulf of California
The Gulf Corvina (Sciaenidae: Cynoscion othonopterus) is endemic to the Gulf of California and every year migrates to the Upper Gulf region to spawn in the delta of the Colorado river estuary at which time it is heavily exploited. The fishery of this species is being studied to develop a sustainable fishery and to understand the impact of the fishery on the population, and its reproduction, as well as on the ecology and biology of the species.
The Colorado river once reached the sea at the northern-most Gulf of California, but today only a remnant reaches the delta in very wet years. However, the habitat conditions and food available in this region are still plentiful, and a number of species come each year to reproduce in large numbers. This species is extremely important because its arrival in the Upper-Gulf (UG) coincides with Lent, a time of major consumption of fish in Mexico. The Corvina fishery thrived until the 1950s, but then disappeared for several decades before reappearing in the early 1990s. Today the annual production ranges between 1,500 tons and 4,500 tons, and this enormous amount of fish is collected over a period of just a few days during the months of February, March and April. Because of the behaviour of the species, fishermen only have a small time window to find and catch fish. Traditional knowledge indicates that the adults start arriving just after the quarter moon phase. Around that time, the aggregations move around the Gulf of the Santa Clara region before traveling north to enter the Colorado River delta. Spawning takes place in the river estuary right before the strongest tides and closer to full and new moons. Soon after, within a matter of hours, all the fish leave the region with the tide. This process is repeated for three months.
Researchers from the Center for Marine Biodiversity and Conservation (CMBC) at the Scripps Institution of Oceanography are working with Alto Golfo Sustentable (AGS), a consortium of NGOs, government and local fishermen, to study the species and collectively propose alternatives to improve the Gulf Corvina fishery. The government implemented new regulations in 2007, including a fishing season, a total landings quota, restricted fishing areas, and fishing gear restrictions. Although enforcement is implemented with some level of effectiveness, much work remains to create a sustainable fishery.
This year we are collecting and analyzing samples to determine the spawning cycle, batch fecundity, and population structure, and to fill in remaining gaps in general life history. We are interviewing fisherman to better understand the socio-economic aspects of the fishery and to increase public awareness on the value of generating information to improve management. We are also monitoring other components of the fishery, including daily landings, market prices, and the entire economic structure of the fishery. Landings information is provided by the government, and, together with the local fish buyers, we aim to estimate total fishing effort.
Gustavo A. Paredes, Brad Erisman, Octavio Aburto-Oropeza