Sea Technology

SEP 2012

The industry's recognized authority for design, engineering and application of equipment and services in the global ocean community

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marineresources Abalone Study Shows Marine Reserves Are Key to Regeneration A study has revealed that after a mass mortality of marine life in the waters off Baja California, Mexico, egg production of pink abalones in the marine reserves increased 40 percent, while being cut in half in fished areas. A significant amount of larvae also spilled over into unprotected areas open to fishing, which helped them re- bound more quickly. The study backs the idea that marine reserves are vital to jump-start the recovery of species following a mass mortality. Starting in 2006, the study, which was published in PLoS ONE in July, used data from abalone fishing areas around Isla Natividad, Mexico, includ- ing new marine reserves hard hit in 2009 and 2010 by hypoxic events, epi- sodes of low dissolved oxygen in sea- water that weaken and kill marine life. Because it preceded the 2009 mor- tality event, the study allowed obser- vation of its demographic effects in the reserve and fished areas. After the 2009 hypoxic event, abalone biomass declined by 75 percent at fished sites but only 50 percent in reserves. The rate at which juvenile abalone are ready to be harvested in the reserves remained stable but was nine times lower in fished areas. The large size of the protected abalone and population density influenced resilience. The study focused on abalone for its high commercial value and population depletion in recent years. Abalone har- vesting around the North Pacific has declined from a high of 24,000 to 115 metric tons in 1995. Since 1997, aba- lone has been closed to fishing south of San Francisco, California. Toxic Cyanobacteria Linked to California Sea Otter Deaths Federal and state entities confirmed this summer the connections between freshwater Microcystis blooms and sea otter deaths in California, the Depart- ment of the Interior reported in August. Microcystis is a cyanobacteria that produces the potent liver toxin micro- cystin. Once produced in freshwater lakes and rivers, microcystin can travel downstream and bioconcentrate in clams, oysters and mussels, and other invertebrates that filter feed in contam- inated water. Dead sea otters were examined by the California Department of Fish and Game, based in Santa Cruz. The gums and the whites of the otters' eyes were bright yellow, and it was later con- firmed that acute liver failure was the cause of death. A common-culprit bac- teria was ruled out as the cause of the liver failure, so scientists looked to the high concentrations of cyanobacteria that had been reported from a nearby lake as a possible cause, which was eventually verified. Human-associated pollution con- tributes to cyanobacterial blooms and microcystin production via runoff con- taminated with fertilizer and animal waste, or leakage from sewage or sep- tic systems. Thirty-one microcystin-positive sea otters have been identified in California. Sea otters, a state and federally protected threatened species, could be exposed to microcystin through the shellfish they eat, which could also affect humans. 74 st / SEPTEMBER 2012 www.sea-technology.com

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