Massive Fish Spawning Migration Comes into Focus

Each spring, an immense breeding migration culminates in the northernmost portions of the Gulf of California at a reserve near the Colorado River delta. Synchronized with the tides two to five days before new and full moons in March and April, millions of fish known as Gulf corvina congregate during a spawning ritual in which a single female can produce 1 million eggs.

Fishermen have come to know the migration well. Capitalizing on the time-tested punctuality of the migration, they catch more than 1.5 million corvina in a span of 21 to 25 days every year.

But now fishermen are working with scientists to help ensure that the fragile corvina fishery isn’t harvested into oblivion.

A new research paper in Scientific Reports authored by Brad Erisman, Octavio Aburto-Oropeza, Phil Hastings, and Marcia Moreno-Báez of Scripps Institution of Oceanography at UC San Diego and their research colleagues in Mexico details a collaboration that mixes science, technology, and cooperation among the local inhabitants of the region.

At the core of the report is a description of the use of GPS devices to ascertain details between breeding migration and the fishing activity in the area. The data have provided specific information about the spawning activity and the fishing patterns that follow.

“With such a massive fishing effort, the first step towards a sustainable solution was to quantify the situation there,” said Erisman, a postdoctoral researcher with Scripps’ Center for Marine Biodiversity and Conservation. “This study is the first comprehensive report on the completely synchronized activity of a fish spawning aggregation and its fishing harvest, down to specific space and time details. The results we’ve generated will allow decision-makers to design regulations to balance the health of this vulnerable species with the livelihoods of fishermen.”

The corvina fishery is the main source of income for the community of El Golfo de Santa Clara and the main component of the subsistence fishery for the indigenous Cucapah community of El Indiviso. Both communities have depended on the spawning migration of corvina for nearly a century and are well aware and concerned about the potential negative effects of fishing during the corvina’s breeding period. They are interested in measures that will allow them to continue to harvest the species sustainably for generations to come.

The researchers and the local fishermen see the benefits of the collaborative study as a significant and necessary first step towards creating management solutions that seek to avoid a decline in the fishery, support a healthy population of spawning fish, and thereby support a sustainable and profitable fishery.

“As a fisherman, I want to collaborate so I can help in the fisheries management in my community,” said Miguel Reyes, a fisherman from El Golfo de Santa Clara who has participated in the research studies since 2009. “The government does not have enough capacity to generate data on the field, and this has resulted in our involvement in these types of activities. I consider this information to be so detailed that it can back up any management decision made for corvina golfina.”

Adding to the market value of the fishery is the religious season of Lent, the period prior to Easter during which members of Christian religions increase their consumption of fish in an effort to refrain from eating red meat on certain days.

“It is very important for the leaders of the fishing federations and cooperatives to understand the behavior of the species that we fish,” said Carlos Tirado, president of the Federation Pescadores de la Reserva de la Biosfera. “We need to understand how to fish sustainably; know the days and hours when corvina golfina is most vulnerable. Our fishing federation is committed to the science and we want this information to be public, however, we also need to protect the fishermen’s livelihood.”

“Ultimately, we hope these results demonstrate the endlessly positive aspects of collaborative research and cooperative management for resolving problems of overfishing and creating sustainable futures for marine species and resource use,” said Aburto-Oropeza, coordinator of the Gulf of California Marine Program at Scripps Institution of Oceanography. “From a local perspective it demonstrates that fishing communities in the upper gulf remain serious about marine conservation and they are willing to cooperate with each other, scientists, and government agencies.”

The study also has created interest in young fishers and new generations of student scientists in the community who are interested in participating in the monitoring, management, and enhancement of their fishery and the protection of their natural resources.

“I got involved in this scientific research because I believe it will help us to keep fishing corvina golfina without it becoming a scarce resource,” said Arturo Armenta, a 19-year-old fisherman who has been part of the technical team in the community of El Golfo de Santa Clara. “We have to let the species reproduce so we can fish it and our livelihoods are not affected in the future.”

The findings of the study have been presented to fisheries managers, state officials from Baja California and Sonora, non-governmental organizations, park managers, and scientists from Mexico and abroad in an effort to seek rapid, sustainable solutions.

“This study is important in order to record the health of the corvina golfina population,” said Hilda Hurtado, president of the Pueblo Indígena Cucapá Fishing Cooperative, who participated in research activities inside the channels of the Colorado River delta. “We think the results will be useful for analyzing whether the species is endangered and if the annual fishing ban has been set in the appropriate season. This information is essential to establish suitable regulations that may be different from those commonly used like fishing caps and other legal measures.”

In addition to Erisman, Aburto-Oropeza, Hastings, and Moreno-Báez, co-authors of the study include La Paz, Mexico-based scientists Ismael Mascareñas-Osorio of Centro para la Biodiversidad Marina y la Conservación and Charlotte Gonzalez-Abraham of Centro de Investigaciones Biológicas del Noroeste S.C.

The Walton Family Foundation and the David and Lucile Packard Foundation funded the study.

-- Mario C. Aguilera