Conservation News
Where Have All The Rockfish Gone?
By Dougald Scott
Where Have All The Rockfish Gone?
By Dougald Scott
To those of us who have fished Monterey Bay for years, the supply of rockfish (also known as "rock cod") seemed endless. If you couldn't catch a salmon or halibut, you could always find a reef and catch as many rockfish as needed for dinner. They were so abundant that there was no season limit. I can remember when the bag limit was thirty fish. In the last few years the situation has drastically changed. You now find many times fewer rockfish, and fewer still of suitable size for the table. In addition, a season limit now restricts fishing to four months (July through October). Scientific studies show the total biomass of bocaccio has fallen to about 2% of its 1969 level.
What happened? As with most complex systems in nature, there is no simple answer. And as in other cases of disappearing resources, it's easy to point the finger at someone else. From stories I've heard, the culprits are the commercial fishermen, the sport fishermen, the spear fishermen, the drag boats, or even El Nino, all depending on to whom you are talking. Ironically, scientific studies indicate that all of the above have contributed to the crash in rockfish abundance.
What can be done to bring the rockfish back? The obvious answer is to pinpoint the causes for the crash and develop a management plan that assures their return. Good fisheries management plans are based on the life histories of the fish in question. With this information, a system is designed to allow commercial and sport fisheries a maximum limit that still allows a sufficient number of fish to reach reproductive maturity and replenish the population. Management of rockfish is complicated by the fact that there are more than 60 different species along the U.S. West Coast, with 14 of these commercially marketed as "red snapper."
What all the rockfish species have in common, and what makes them especially difficult to manage, is a very slow growth and maturity rate, and a fragile larval stage. A 12-inch blue rockfish is somewhere between 10 and 20 years old. Fifty year-old rockfish are common.
Reproduction in rockfish occurs by internal fertilization and development of the embryos to larvae inside the female. Larvae are released when they are about 1/4-inch long, and enter a pelagic phase where they drift with the currents in open water. It is at this stage where they are most vulnerable to predation and climatic variations. Only a tiny fraction survive. The pelagic phase ends with settlement (also known as recruitment), when the now juvenile fish are 1-4 inches long, and take up residence in the bottom habitat appropriate to their species.
It has been known for a number of years that older female rockfish produce exponentially more larvae. A 20-inch female bocaccio for example, will produce about 200,000 larvae, while a 31-inch female will produce ten times that - nearly 2 million. Research presented last February cast new light on the important role that older (and larger) females contribute to the survival of their larvae. Steve Berkeley of UCSC, and a team of fisheries scientists from other institutions, found that survival rates were nearly three times higher, and growth rates were 3.5 times faster for larvae from older mothers. The team discovered that older mothers produce larvae with a larger oil globule, greatly enhancing their survival. The older mothers also spawned earlier than younger ones, with the earlier spawning coinciding with more favorable zooplankton blooms, the food of the larvae.
The traditional management tool of simply limiting catch is clearly not working because both commercial and sport fisheries target larger, older fish. This leaves a reproductive pool of younger fish, which are not nearly as fecund as the older ones, and results in fewer fish in the next generation. In some fisheries, a slot limit (allowing a take between a minimum and a maximum size) provides for the survival of older fish and is an effective management tool. This tool is not appropriate for rockfish because the usual methods of take are lethal. Even with a barbless hook sport fishery, the rapid depressurization experienced in bringing the fish to the surface from depths greater than about 40-feet, results in damage for which a released fish cannot compensate. There are techniques for improving survival, but these involve special equipment such as hypodermic syringes, and are not likely to be correctly employed by most anglers.
A management tool, called "ocean zoning," is being promoted by many scientists who study rockfish. According Steve Berkeley, "Some areas might be totally protected, some closed seasonally, some open to commercial fishing, some only open for recreational fishing and so on." "As far as protecting age structure and maintaining big old fish, I canŐt come up with anything better than a marine reserve-type approach where you protect a segment of the population from fishing. There may be other approaches that would work, but I think we know enough to get a good start on a network of marine reserves."
The notion of setting aside areas for special protection from fishing pressures (known as Marine Protected Areas or MPAs) is not new. There are presently about 60 MPAs in California with the oldest right in our back yard in Pacific Grove (the Hopkins Marine Life Refuge established in 1931). In 1999, California adopted the Marine Life Protection Act (MLPA). This legislation directed the state to design and manage a network of marine protected areas in order to, among other things, protect marine life and habitats, marine ecosystems, and marine natural heritage, as well as improve recreational, educational and study opportunities provided by marine ecosystems.
The strategy behind using a network of MPAs as a management tool for rockfish populations is twofold: 1) they will restore depleted populations within the MPAs by protecting older fish; and 2) the MPAs will serve as a source of larvae for recruitment in areas outside the MPAs. A large body of research supports strategy #1, the numbers and size of fish dramatically increase within the MPAs. The research to show that MPAs improve recruitment in surrounding areas is much harder do. Studies using DNA analysis to pinpoint sources of recruitment in areas outside the MPAs are currently underway.
How does all this affect how, when, and where we can fish for rockfish? The answer is it's being worked on. The 1999 legislation called for the establishment of a Blue Ribbon Task Force to, among other things, develop a proposal for alternative networks of marine protected areas in an area along the central coast. Obviously, the most important questions to anglers are: how many; how large are they going to be; and what are their exact locations. The Task Force is still in the process of working out these details. You can keep up on Task Force developments on the internet at: www.dfg.ca.gov/mrd/mlpa/index.html.
None of us like having our favorite fishing spots taken away, but it's clear some action must be taken to restore rockfish to their prominence along our coast. I think this can be fairly accomplished if the MPAs are located in more remote areas, not easily reached by small craft. This will provide continued fishing access for most anglers, and needed protection for the rockfish stocks. There is a chance that a huge MPA could be established from Natural Bridges to Ano Nuevo. In my opinion, this would be excessive and should be opposed. It's very important that we all follow the activities of the Task Force and the specific size and location of the proposed MPAs.