Sportfishes Benefit in La Jolla Marine Reserve
Researcher:
Philip A. Hastings
Scripps Institution of Oceanography
University of California San Diego
9500 Gilman Drive
La Jolla CA 92093-0208
E.: phastings@ucsd.edu
T.: (858) 822-2913
Relevant Links:
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Revised:
September 26, 2008
A kelp bass in the La Jolla Ecological Reserve. Credit: Brad Erisman
September 10, 2008
Contact: Christina S. Johnson, csjohnson@ucsd.edu, 858-822-5334
According to results of a four-year diver survey, the marine reserve at the La Jolla Cove, established in 1971, has created a haven for sportfishes.
UC San Diego marine biology professor Phil Hastings, who led the survey, also reports finding the highest long-term average density of kelp bass recorded in the Southern California Bight in the last four decades in the reserve.
The results are especially noteworthy given the relatively small area of the San Diego-La Jolla Ecological Reserve, only 210-hectares, or .81 square miles.
“We were surprised by our results,” Hastings said. “We knew the La Jolla reserve protects important habitats but we did not necessarily expect to see measurably higher densities of reef fishes because the reserve is so small. Our results tell us the reserve and surrounding area are important habitats for these fishes and should receive continued and even expanded protection from fishing.”
Map of the reserve. Credit: P. Hastings
For the project, which was funded by California Sea Grant, divers swam set 50-meter transects at multiple depths in the reserve, at an adjacent site known as Boomers and at a control site off Palos Verdes in Los Angeles and counted the numbers of each species of fish observed. Boomers is a shallow reef area adjacent to the reserve known for its pounding surf, hence its name, and is not heavily fished. The area off Palos Verdes has high-relief reef and kelp forest similar to that of La Jolla but is heavily fished.
In all, 252 transects were swum within the reserve, 248 at Boomers, and 188 at Palos Verdes for the four-year period beginning in 2002. On these, divers counted 52,520 fish at the reserve, 41,330 at Boomers and 16,080 at Palos Verdes. Fifty-two species were counted at the reserve, compared to 50 species at both Boomers and Palos Verdes.
Not only was the diversity of fish life comparable at all three sites but so were the relative abundances of species. Eight of the twelve most common species were the same at all three sites, as were the two most common species, blacksmith (Chromis punctipinnis) and senorita (Oxyjulis californica).
Sea Grant Trainee Brad Erisman counting fishes in the La Jolla Ecological Reserve. Credit: Matt Craig.
“The main difference between the sites is that Palos Verdes has fewer fish,” Hastings said, including two of the region’s most popular sportfish, California sheephead (Semicossyphus pulcher) and kelp bass (Paralabrax clathratus).
Based on the diver counts, sheephead and kelp bass were three to four times more numerous at Boomers and the reserve than at Palos Verdes. In addition, divers recorded the highest reliable density estimate of kelp bass – an average of 0.15 fish per square meter in the reserve over six sampling periods during 2004 – higher than any other estimate from more than 30 comparable quantitative surveys in the Southern California Bight during the last four decades.
The higher density in the La Jolla reserve does not necessarily extrapolate to large population sizes for these species because of the small size of the reserve. “Considerably larger reserves are needed to significantly increase the overall populations of these sportfishes. Based on this and other studies, the La Jolla region should be seriously considered in plans to expand marine reserves in southern California,” Hastings said.
Hastings and Sea Grant Trainees Matthew Craig and Brad Erisman, both of whom earned doctorates in marine biology from UC San Diego, are preparing manuscripts on their findings for peer-reviewed publication.
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