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Marine Resources


September 2012 Issue

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 rebound 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, including new marine reserves hard hit in 2009 and 2010 by hypoxic events, episodes of low dissolved oxygen in seawater that weaken and kill marine life.

Because it preceded the 2009 mortality event, the study allowed observation 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 harvesting around the North Pacific has declined from a high of 24,000 to 115 metric tons in 1995. Since 1997, abalone 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 Department of the Interior reported in August. Microcystis is a cyanobacteria that produces the potent liver toxin microcystin. 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 contaminated 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 confirmed that acute liver failure was the cause of death. A common-culprit bacteria 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 contributes to cyanobacterial blooms and microcystin production via runoff contaminated with fertilizer and animal waste, or leakage from sewage or septic 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.

Regional Extinction Risk on the Rise for Parrotfish, Surgeonfish
A study conducted for the International Union for Conservation of Nature (IUCN) Red List of Threatened Species found that 86 percent of the populations of parrotfish and surgeonfish face a low risk of extinction globally but face a heightened risk regionally, especially in areas like the Coral Triangle. The results were published in July in PLoS ONE. Parrotfish and surgeonfish are important to fisheries and tourism, and are vital to the health of coral reefs, as they feed on and limit the growth of algae on coral.

The Greenback Parrotfish, listed as endangered, and the Bumphead Parrotfish, listed as vulnerable, are large-bodied, long-lived species experiencing significant population declines from fishing pressure. The Kapingamarangi Surgeonfish, provisionally listed as vulnerable, is only found in the Kapingamarangi Atoll, Caroline Islands.

The Rainbow Parrotfish is presently listed as data deficient but has been proposed for listing as near threatened. It was previously listed as threatened because it had historically been fished to low numbers. Although the Rainbow Parrotfish has been found to have stabilized in small numbers, it continues to suffer from decline due to destruction and loss of its mangrove habitats and overfishing.

Researchers also conducted a survey of parrotfish and surgeonfish in the Coral Triangle region, which encompasses much of Indonesia, Malaysia, the Philippines, Brunei, Timor L'Este, Papua New Guinea and the Solomon Islands. Of the 105 species of parrotfish and surgeonfish in the Coral Triangle, 18 are targeted by fisheries and 13 are at higher risk of extinction regionally versus globally.

Conservation International said 120 million people in the Coral Triangle rely on fish as a primary protein source, and 95 percent of Southeast Asian coral reefs are threatened, particularly by fishing.

Marine Organisms Lighten Shells And Skeletons as Ocean Acidifies
A study published in Global Change Biology in August suggested that increased ocean acidity is affecting the size and weight of shells and skeletons of marine organisms. These animals are an important food source for marine predators, as well as a valuable ingredient in human food production.

Scientists from the British Antarctic Survey, the U.K.'s National Oceanography Centre, Australia's James Cook and Melbourne universities, and the National University of Singapore investigated the natural variation in shell thickness and skeletal size of clams, sea snails, lampshells and sea urchins living in 12 different environments, ranging from the tropics to the polar regions.

The researchers found that as the availability of calcium carbonate decreased, skeletons got lighter and accounted for a smaller part of the animal's weight. The same effect occurred consistently in all four marine-life types studied, which suggests the effect is widespread across marine species and that increasing ocean acidification will progressively reduce the availability of calcium carbonate. The effect is strongest at low temperatures.

The study suggests that given enough time and a sufficiently slow rate of change, marine life could evolve to survive the acidifying oceans.


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