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Sea Otters, Abalone May Need Separate Reserves
SEATTLE, Washington, January 28, 2003 (ENS) - Predators and prey, such as sea otters and abalone, may need separate reserves to protect them, a new study suggests.
California's red abalone population is so low that all of the commercial fisheries and all but one of the recreational fisheries are closed. Meanwhile, California's sea otter population is at about 2,000 and is dropping by about one to two percent each year.
While the state has two marine reserves that protect the otters from people, there are none that protect the abalone from otters.
"We conclude that coastal marine protected areas off California cannot enhance abalone fisheries if...they also contain sea otters," said Samantha Fanshawe, who did this work while at the University of California at Santa Cruz, and is now at the United Kingdom's Marine Conservation Society. Fanshawe and her colleagues - Glenn VanBlaricom of the University of Washington in Seattle and Alice Shelly of TerraStat Consulting Group in Seattle - report their findings in the February issue of the journal "Conservation Biology."
To see if reserves can both protect the sea otters and rebuild the red abalone fisheries, the researchers studied red abalone at six sites, four with and two without sea otters. The sites with otters were off Monterey County and the sites without otters were off Sonoma County, and abalone harvesting is prohibited at all six of the sites.
The researchers determined the abundance and size of red abalone at two depth zones: "shallow," about 10 to 15 feet deep, and "deep," about 25 to 33 feet. Sea otters can dive as deep as 330 feet and so can reach abalone on both zones.
Fanshawe and her colleagues found that red abalone were far more abundant at the sites without sea otters: there were about seven times more of the abalone in the "deep" zones, and almost 20 times more in the "shallow" zones. In addition, the abalone were an average of almost two times bigger at the sites without sea otters.
The work shows that "calls for management of marine protected areas for multiple human uses may be ecologically naive, creating unattainable expectations for performance," write Fanshawe and her colleagues. The researchers call instead for single use marine reserves that focus either on ecosystem restoration or on fishery development.
This approach has been adopted in the Florida Keys National Marine Sanctuary, where managers have split a former multiple use protected area into smaller areas with goals that are less likely to conflict.
SEATTLE, Washington, January 28, 2003 (ENS) - Predators and prey, such as sea otters and abalone, may need separate reserves to protect them, a new study suggests.
California's red abalone population is so low that all of the commercial fisheries and all but one of the recreational fisheries are closed. Meanwhile, California's sea otter population is at about 2,000 and is dropping by about one to two percent each year.
While the state has two marine reserves that protect the otters from people, there are none that protect the abalone from otters.
"We conclude that coastal marine protected areas off California cannot enhance abalone fisheries if...they also contain sea otters," said Samantha Fanshawe, who did this work while at the University of California at Santa Cruz, and is now at the United Kingdom's Marine Conservation Society. Fanshawe and her colleagues - Glenn VanBlaricom of the University of Washington in Seattle and Alice Shelly of TerraStat Consulting Group in Seattle - report their findings in the February issue of the journal "Conservation Biology."
To see if reserves can both protect the sea otters and rebuild the red abalone fisheries, the researchers studied red abalone at six sites, four with and two without sea otters. The sites with otters were off Monterey County and the sites without otters were off Sonoma County, and abalone harvesting is prohibited at all six of the sites.
The researchers determined the abundance and size of red abalone at two depth zones: "shallow," about 10 to 15 feet deep, and "deep," about 25 to 33 feet. Sea otters can dive as deep as 330 feet and so can reach abalone on both zones.
Fanshawe and her colleagues found that red abalone were far more abundant at the sites without sea otters: there were about seven times more of the abalone in the "deep" zones, and almost 20 times more in the "shallow" zones. In addition, the abalone were an average of almost two times bigger at the sites without sea otters.
The work shows that "calls for management of marine protected areas for multiple human uses may be ecologically naive, creating unattainable expectations for performance," write Fanshawe and her colleagues. The researchers call instead for single use marine reserves that focus either on ecosystem restoration or on fishery development.
This approach has been adopted in the Florida Keys National Marine Sanctuary, where managers have split a former multiple use protected area into smaller areas with goals that are less likely to conflict.
