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Fishing for Trouble (02/13/03) - Both marine biologists and chefs are working together to give some fish a break.
image: Milton Love, University of California, Santa Barbara
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Reeling in a big fish promises a tasty meal and of course a fish tale. But as this ScienCentral News video reports, it may be a good idea to let the big ones get away.
Off The Hook
When John Mellor was a teenager, he spent his summers working as a deck hand on one of several party boats that cruised out of San Francisco Bay loaded with rowdy anglers, headed for the Farrallones Islands in search of rockfish. Seven days a week he skipped between guys, setting their hooks, untangling their lines, and dealing with their fish. At the end of each afternoon, as the boat nosed towards the Golden Gate, Mellor passed around a jack pot. Each guest pitched in a dollar and the guy who caught the biggest fish won the cash. But Mellor, now 42 and one of only three remaining commercial rock fisherman in San Francisco, wishes more of those big fish had slipped off their hooks.
New research suggests reeling in the big fish of long ago might have seriously impacted rockfish populations of today. Marine biologist Steven Berkeley, and a team of colleagues from the University of California Santa Cruz and Oregon State University, studied black rockfish---or Sebastes melanops---and reported in the journal Ecology that larvae, or baby fish, from older female rockfish grew faster and survived longer without food than the fish that came from young mothers, suggesting that hooking older, bigger fish could in the long run leave us with fewer fish to fry.
Black rock fish. image: Bill Barss, Oregon Department of Fisheries and Wildlife
Our whole theory of fishing may not be providing [the fish] with enough protection to enable them to survive and reproduce and maintain their population over the long-term, Berkeley warns.
The team spent two years collecting pregnant female black rockfish that they transferred to holding tanks at the Hatfield Marine Science Center at Oregon State University. Just before the fish were expected to give birth, the researchers anesthetized them, removed their larvae and divided the larvae into three groups. One group got no food. The second group was fed a diet of tiny multi-cellular animals called rotifers at a concentration of 1 per mL of tank water, and the third group ate the same diet, but at a concentration of 10 per mL. As the larvae grew, Berkeley and his colleagues determined the ages of their mothers by counting the rings in each fishs otilus, or ear bone, just as you would a tree. "What we found was that the larvae from old fish grew more than three times faster than the larvae of young fish," he says. "The larvae of old fish could survive a period of starvation more than twice as long as the larvae of young fish."
Their survivability, Berkeley believes, is linked to inherited oil globules. When rockfish are born, the only source of food that they contain is in the form of a little droplet of oil, explains Berkeley. Andthe oil droplet in the larvae from the old fish was much bigger than it was in the larvae of the young fish. The droplet---an opaque sphere located in the belly---feeds baby fish until they are big enough to swim against ocean currents and catch their own food. Older fish are able to give their young a bigger droplet is because they're not spending so much energy growing, Berkeley believes. Once you reach your maximum sizeyou have more energy to invest in your larvae, he says.
The droplets are at work in other fish like striped bass, salmon, and Atlantic cod, so if fish need this oil to survive, as Berkeley's work suggests, then it's imperative to protect older fish, just as we protect younger fish. Berkekely says establishing regulations that set an upper limit, not just a lower limit on the size of fish that can be caught, would do the trick.
But boosting rockfish populations is complicated. Because they live in a diversity of habitats, theres no one regulation that can shield all them. Couple that with their slow growth---it takes females ten years to reach sexual maturity before they give to birth live young, not eggs---and baby rockfish either become food for bigger fish, are swept into unfriendly waters, or just starve. Berkeley says fishery management needs to be tailored to each species' life cycle, sexual maturity, larval mortality rate and habitat vulnerability.
Once a West Coast fishing staple, rockfish were over-fished in the 1980s and 1990s. In 2002, the Pacific Fishery Management Council, the federal body that manages fisheries in California, Oregon, and Washington, started regulating the industry. Under current California law Mellor, the San Francisco fisherman, can only catch 500 pounds of rockfish a year, the equivalent of two days fishing. I used to rely on it to support myself for a good part of the year, but he says, Its gone to being just kind of a fill in sort of thing.
Zeke Grader, director of the Pacific Coasts Federation of Fishermans Associations, says one way to help rockfish is to redefine how they're fished. Perhaps focusing more on hook and line or trap fisheries as opposed to trawling for these stocks, would give fish a better chance at survival, he says. Unlike trawl nets, which kill many fish on the way to the surface, hooks and lines or fish traps would allow fishermen to hand select fish and throw back any that are too small or too big. Grader believes that switching to a more artesian way of fishing would allow fishermen to continue fishing while the stocks are rebuilding.
It's worked for other fish in the past. In California, the recreational sturgeon fishery is regulated using upper and lower size limits, known as slot limits, as Berkeley has recommended for rockfish. Californias Marine Life Management Act gave the states Fish and Game Commission permission to set up similar limits for rockfish in 1998 but the regulations are not in place. Even if they were, slot limits probably are not a good idea for rockfish, says Maria Vojkovich a biologist with the California Fish and Game Commission. She says that deepwater dwellers like some rockfish species don't survive the catch, and can't be thrown back, because they have air bladders that can burst as pressure decreases when they're brought to the surface too quickly. Some fishermen, however, have figured out how to use a needle to relieve this pressure and are able to keep fish alive all the way to the market. As a whole, Vojkovich says it is best to try and minimize rockfish catches and clear the waters of fishermen during the spawning season.
Courtesy: Milton Love, University of California, Santa Barbara
It's an approach the state's already taken and one that keeps Mellor off rock fishing grounds ten months out of the year. I see a big improvement in fish abundance than I did even three to four years ago," says Mellor. But don't take that as an endorsement. Mellor thinks the state is being too strict since he says he has no problem catching plenty of fish.
If there's one thing everyone would agree on, it's that the rockfish populations of Mellor's youth will only come back when protections that promote their life cycle are meteven if no one can agree yet on how far those protections should go.
This research was presented at the February 2005 American Association for the Advancement of Science meeting and published in the May 2004 issue of Ecology. The research was funded by NOAA Office of Sea Grant and Extramural Programs, the U.S. Department of Commerce, and the Oregon State Legislature.
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