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Conventional wisdom among marine fisheries managers is that while overfishing can lead to the collapse of a fishery, it cannot bring about the extinction of a species. Managers assume that for prolific spawners, such as abalone and rockfish, size limits well above size at first maturity should protect enough individuals to perpetuate the species. Recent evidence suggests that, at least for white abalone (Haliotis sorenseni), managers were wrong on both counts. White abalone may soon gain the dubious distinction of being the first marine invertebrate driven to extinction by human activities. Discovered in 1940, the white abalone is the deepest dwelling
of eight species of California abalones, ranging from 80 to 200 feet deep.
Scripps Institution of Oceanography biologists conducted surveys of white
abalone deep water habitat in the early 1970’s, finding high concentrations
of about one white abalone per square yard. Such densities were comparable
to abundance of shallower species of abalone found in previously unfished
or protected areas. Unfortunately, high demand for this species led to
a Following collapse of the fishery (from 1979-1992) relatively few scientific studies were directed at determining the abundance of remaining populations of white abalone. The fishery was allowed to continue under the assumption that size limit alone would protect enough spawners to perpetuate the species. Increasing demand for abalone on the world market during the 1980’s
led to a minor increase in take that peaked in 1985 at 0.75 metric tons
(1,700 lbs.)(Figure 2). Increased take probably reflected an In 1992, DFG biologists Peter Haaker and Ian Tanaguchi joined
forces with Channel Islands National Parks biologists Gary Davis, Dan Richards,
David Kushner and others to survey remaining abundance of white abalone.
From 1992 to 1993 they conducted extensive deep surveys, using SCUBA to
the limits of
This information alone was not considered sufficient evidence to close the fishery. Anecdotal reports by sport and commercial fishermen continued to suggest that deeper populations still existed beyond SCUBA diving depths. These reports further delayed efforts by state biologists to close the fishery. Peter Haaker and Gary Davis were able to arrange a survey of deep water white abalone habitat using the Delta, a two-man submarine provided by the National Undersea Research Program (NURP) of the National Oceanographic and Atmospheric Administration (NOAA). Unfortunately, survey of white abalone habitat at depths of 139 to 280 feet also produced low densities. In 27 hours of diving, only 5 live white abalone were found in 3 to 5 hectares of deep water habitat. Last year, another deep water survey was conducted in the Delta by Haaker and Davis, in the center of the former white abalone range. Again, comparable low densities were found. During 1995, commercial landings had fallen to less than 100 white abalone. The Fish and Game commission closed the white abalone fishery in 1996. Based on these findings, white abalone are soon likely
to be listed as an endangered species. Unless found elsewhere, such as
at the southern end of their range off Baja California in Mexico, the white
abalone may well be on its way to extinction. Loss of any species as the result of human activity is tragic since it could have been prevented. All of us, managers and fishermen alike, need to learn from past failures to prevent the potential loss of other species. Currently, green and black abalone populations have fallen to dangerously low levels. These declines are exacerbated by the current El Niño conditions, which have reduced the abundance of kelp, a major food source. Are these species, like the white abalone, also on the brink of extinction? What has been learned by managers of marine resources? For one thing, we now know that humans are capable of causing the extinction of a marine species. We also know that size limits alone do not protect abalone stocks. If we allow a fishery to grow, sufficient resources must be provided to monitor stock abundance independent of the fishery. Fishery statistics such as CPUE can be misleading, indicating increased success as the last of a population is removed. Perhaps a proactive assessment of resources is needed before a fishery is allowed to develop. Ultimately, our goal as stewards of marine resources must be to sustain populations at levels that can withstand periods of recruitment failure or harsh environmental conditions such as those brought about by El Niño. If sport and commercial take is to be sustainable, only truly “surplus” populations can be harvested. Some of the preceeding material was extracted from: Davis G., Haaker
P. and Richards D., Status and Trends of the White Abalone at the California
Channel Islands, Transactions of the American Fisheries Society 125:42-48;
Haaker, P. 1998 White abalone - off the deep end...forever? Outdoor
California, January-February; for additional reading see also: Tegner M.J.,
L.V. Basch, and O.D. Dayton (1996). Near extinction of an exploited
marine invertebrate TREE. 11(7):278-279; CDFG (1998) California
Abalone Envrionmental Document, DFG publication. - KK |
“boom-and-bust”
fishery that was essentially fished out in seven years (Figure 1). White
abalone’s tender, delicious, easy-to-prepare meat commanded higher prices
than other abalone, and consumer demand remained high. Landings peaked
in 1972 at 65 metric tons (144,000 lbs.) dropping rapidly to less than
0.7 metric tons (1,500 lbs.) by 1979 (Figure 1).
increase in demand during a period when abalone prices world-wide tripled
in just over a decade. During this period, catch per unit of effort (CPUE)
in number of white abalone and dollar value per landing showed a deceptive
increase as the last aggregations of the species were picked out (Figure
3). In 1985, a few fishermen took the last remaining aggregations of white
abalone, averaging $1000 per landing.
