The Lone Abalone
Sea Grant-funded Scientists Look at Ways to Aid this Candidate for Endangered Species Act Protection
Once, they were favorites at beach barbecues throughout northern Puget Sound. Now, however, the continued survival of Washington's prized northern, or pinto, abalone (Haliotis kamtschatkana) is in question. It is currently illegal to harvest one of these mollusks, let alone fry one up.
"Worldwide, abalone stocks have declined dramatically in the past few decades," says Carolyn Friedman, a professor at the University of Washington's School of Aquatic and Fisheries Science. "Those declines are often associated with commercial and, to a lesser extent, sport fishing, as well as disease," she adds.
Although they have never been the focus of a commercial fishery in Washington, the Northwest's primary species of abalone has suffered greatly at the hands of recreational harvesters.
Studies conducted in the 1990s by the Washington Department of Fish and Wildlife revealed that northern abalone densities at 10 underwater sites, or index stations, were "uniformly and alarmingly low," according to Friedman.
"These unsettling data led ultimately to the State's listing of the northern abalone as a 'species of concern' and made it a candidate for the federal threatened and endangered species list," she says.
As a stopgap measure, the Washington Department of Fish and Wildlife closed the northern abalone fishery to recreational harvesters in 1994. WDFW workers began to strategize about ensuring the survival of this small but important shellfish.
Meanwhile, the state's remaining northern abalone stocks were fair game for poachers. Even without such illegal activity, some researchers feared that the numbers of abalone at many index sites were too low and that individual abalone were too widely separated to sustain themselves without outside help. In other countries, such as Japan, that help has included replenishment of wild populations with hatchery stock and the creation of underwater preserves within which abalone hunting is prohibited.
From Egg to Adult
"Dwindling numbers of abalone isn't the only problem," notes Friedman. As abalone are removed from a site, the remaining populations can become too widely scattered to reproduce successfully.
"Abalone are known as broadcast spawners," Friedman explains. "That is, both sexes release their gametes into the water column, relying on a random meeting of their sperm and eggs. Generally speaking, male and female abalone must be within one to two meters of each other for successful fertilization."
Any larvae produced by such chance encounters will drift four to 11 days in the water column, before settling on the seafloor. Research suggests that these youngsters most often settle on beds of non-articulated or crustose red algae--underwater plants commonly found in habitats heavily grazed by sea urchins.
Friedman and others believe that such beds are often located seaward of adult abalone concentrations. Because smaller abalone may colonize deeper waters and are better at playing hide-and-seek than their parents, it can be difficult to locate the juveniles and accurately assess their populations.
As they grow and continue to graze on algae, the abalone cut swathes across rock faces, literally clearing the way for sea anemones, sponges and other, more sedentary forms of life to settle and grow. In this respect, the composition of rocky reef communities is in large part determined by abalone populations and whether they are thriving or declining.
Underwater and in the Lab
With funding from Washington Sea Grant, Friedman and her project partners--UW geneticist Kerry Naish, Taylor Shellfish Farms' Joth Davis and Betsy Peabody of the nonprofit Puget Sound Restoration Fund--are taking a multi-pronged approach to restoring and managing the state's declining abalone stocks.
The four specialists are working with Washington Department of Fish and Wildlife dive team biologists, headed by Don Rothaus, to gather fresh data on abalone densities. At various depths near 10 existing WDFW index sites, they've planted recruitment modules--reinforced crab pots filled with overlapping pieces of cinderblock invented by Bart DeFreitas from the Haida Gwai First Nation in British Columbia. These artificial habitats appeal to the crevice-loving juvenile abalone, which are quick to occupy them. The divers can then disassemble the modules to get accurate counts of their one- to two-inch-diameter occupants.
"This is important information from which we can gain a better picture of juvenile abalone habitat," says Friedman.
Simultaneously, the team is studying genetic variability among the various Puget Sound abalone populations. By comparing the DNA of 60 individual abalone, Friedman and Rothaus hope to gain insights into population structure and growth. Is the genetic makeup of all the Puget Sound populations similar? If so, it stands to reason that abalone from various locales are interbreeding, and those beleaguered populations could be bolstered by recruitment from outside. If the reverse is true, and the DNA from one population is distinctly different from the next, then the notion of outside recruitment would be invalidated. A strategy for managing regional populations as separate entities would make better sense.
Hatchery Hijinx
A third project component is exploring ways to improve hatchery techniques for rearing abalone for subsequent release into the Sound.
"Abalone have already been reared for commercial and research purposes but not to supplement stocks in the wild," says Friedman. "This presents different challenges. For instance, captive-reared abalone may exhibit unnatural behaviors or odd coloration--traits that reduce their chances for survival in the wild. To assess the validity of these potential problems and, if needed to avoid them, we need to devise rearing methods that more closely mirror the selection pressures of the natural environment."
Maintaining a healthy degree of genetic diversity is also a challenge for abalone aquaculturists. Because abalone can release millions of eggs and sperm, it would be easy to produce large numbers of nearly identical offspring from very few matings. This could seriously undercut the genetic makeup of wild abalone stocks--a move that might destroy the stocks' ability to adapt to environmental conditions or its resistance to certain diseases.
Friedman's team is also taking steps to actively involve the public. "Of course, we want to share the results of our studies, and solicit input from other abalone experts in the field," says Friedman. "But just as important, we want to garner the support of local dive clubs and others with stakes in the abalone resource. We all need to work together to preserve one of Washington's favorite shellfish."
To date, the team has cultivated several thousand abalone hatchlings, completed surveys of the 10 index sites and begun the genetics work that will soon shed light on the relationships among wild stocks.
"We're guardedly optimistic about our work with these ecologically important subtidal animals," Friedman concludes.
Winter 2004
Contact David G. Gordon, Science Writer for Washington Sea Grant, for further information.