Are MPAs the Answer?
WSGP-funded researchers explore the many factors that make Marine Protected Areas work.
The basic idea is simple: to allow fish stocks to rebuild, create special no-take zones in the waters off our coasts. In reality, the solution is much more complex. With numerous influences — from the quality of habitats and water conditions to the availability of food and undisturbed breeding sites — there's no guarantee that lessening fishing pressure will, by itself, enable fish populations to replenish themselves.
Still, faced with steady declines of copper rockfish (Sebastes caurinus), quillback rockfish (S. maliger), lingcod (Ophiodon elongates) and other commercially and recreationally important fish species throughout the San Juan archipelago and in Puget Sound, resource managers have established no-take zones in hopes of stemming the tide. Most of these no-take zones have been selected without solid data to support the process.
Basing its decisions on the best available information at the time, the University of Washington's Friday Harbor Laboratories and the Washington Department of Fish and Wildlife (WDFW) jointly established four research sites, where all forms of fishing and shellfishing was prohibited, in the early 1990s. More recently, members of the San Juan County Marine Resources Committee worked with fishermen to identify voluntary "no-take" zones at locales where bottomfish stocks were in noticeable decline.
Steady declines have troubled sport fishers and fisheries biologists alike. Scientists and resource managers are uncertain of the cause of the declines. Lingcod have shown signs of recovery in recent years. Still fishers and managers remain unsure if the protected sites (known to scientists as Marine Protected Areas, or MPAs) in the San Juans are effectively doing their jobs.
"Resource managers who propose MPA networks as a tool in rebuilding and conserving depleted fish stocks are often asked 'What are the goals in establishing MPA networks?' and 'How will we know when those goals have been achieved?'" says Don Gunderson, a professor with the University of Washington's School of Aquatic & Fishery Sciences.
"These questions have frequently been posed by residents of San Juan County and in the six other Washington counties that make up the Northwest Straits Marine Conservation Initiative, charged with restoring bottomfish populations in the area," he notes. "Answering these questions is also important to WDFW as it expands its system of mandatory no-take areas, and it is clear that this will require broad-scale surveys of habitat and fish densities, both inside and outside of the protected areas."
In-Depth Explorations
With funding from Washington Sea Grant, Gunderson and his associates — WDFW's Wayne Palsson and H. Gary Greene of California's Moss Landing Marine Laboratories — have been studying underwater habitats within and adjacent to MPAs in the San Juan Channel.
Using sophisticated multibeam sonar mapping, augmented with data from scuba diver surveys and videotapes from deep-diving remotely operated vehicles (ROVs), the three scientists are exploring spatial relationships and recruitment pathways for larval, juvenile and adult rockfish and lingcod. Representatives of the three life stages require different habitat types, says Gunderson, so the team has been conducting its surveys in comparatively shallow nearshore areas and somewhat deeper open-water passages as well as on deep, sponge-encrusted reefs, several hundred feet below the surface.
While adult rockfish favor deep habitats, their fry spend the first weeks adrift, carried by tidal currents in shallower open-water locales. As they grow, they seek food and shelter closer to shore. Most young-of-the-year rockfish prefer the seaweed-rich nearshore zones, typically in water less than 100 feet deep. "The two-centimeter-long juveniles are well-camouflaged, with colors that resemble the kelp they hide in," says Jessica Hayden-Spear, a UW graduate student gathering study data through scuba surveys. "Press down on the kelp and the rockfish pop up, ready to be counted."
Adult rockfish and lingcod congregate on deep reefs and ledges, often at depths of 600 feet — far beyond the reach of scuba divers. Surveys of these fish must be conducted using ROVs capable of withstanding the extreme pressure, nearly 300 pounds per square foot.
"We're finding that the populations of adult lingcod and rockfish are gradually rebuilding, thanks in large part to the no-take zones," says Gunderson. "However, before we can select any additional MPAs, we really need to understand the connections between juvenile and adult habitats — how they enforce each other's effects on the fisheries."
Plenty of Pieces in the Puzzle
The relationship between habitats for juvenile and adult fish is just one part of the MPA puzzle. Gunderson, Greene and Palsson have already identified several different habitat types, each with its own assemblage of key fish species. Now, they must probe deeper, to determine how these habitats are related and how they affect the ability of beleaguered fish stocks to rebound.
"One of the most promising developments in MPAs worldwide has been the increasing focus on measuring their effectiveness — that is, whether existing sites are achieving their goals," says John Davis, editor of MPA News, a monthly newsletter produced at the University of Washington with WSGP support. "The attention being paid to optimizing existing MPAs, rather than only creating new ones, is a sign of maturation for the field. It bodes well for the ecosystems, and for the human communities that depend on these resources."
Indeed, the work of Gunderson, Greene and Palsson may have relevance beyond the San Juan archipelago and the waters of the Pacific Northwest. Their findings may figure into future models, adopted by resource managers, for determining how to estimate population sizes and carrying capacities of all manner of underwater systems, from deepwater canyons to coral reefs, throughout the world.
Autumn 2005
Contact David G. Gordon, Science Writer for Washington Sea Grant, for further information.