By Megan Herring
Southern California’s beaches, sun, tranquility, and other resources makes it a prime area for people looking for a new place to plant roots and make their fortune. For this reason, California has seen a rapid growth in population and commerce, which has led to a number of positive effects on the California people and economy. With more people living and traveling to the state the economy has seen a huge boom leading to an increase in industry and comforts for those who live in California. Unfortunately, this success hasn’t come without a price; the golden state has begun to experience some of the negative consequences of its economic and social growth. Unsustainable resource extraction and environmental damage have become worrisome topics to many environmentalists as well as business owners who rely on these resources to sustain their livelihoods.
One such consequence of California’s economic and population boom involves the decrease in population of abalone, a type of mollusk, in southern California. There are many different species of abalone including the white, black, red, and green abalone, which can all be found off the coasts of California and Mexico. Using a muscular foot, the marine gastropod is able to hold onto a rocky surface where they scrape off algae from the ocean floor for food.
Abalone were once a common site for divers in the area, especially around Catalina Island, just off the coast of Los Angeles, but they have seen a large decrease in population. Species such as the white and black abalone are now listed as endangered. As abalone have begun to decrease in numbers the health of coastal food webs has deteriorated as well. The abalone help to keep the population of algae low enough so as to decrease the chance for algal blooms in the ocean, which can block sunlight to the ocean floor resulting in a decrease in the amount of oxygen created by photosynthetic organisms, which is essential for other animals. Also, with the decreasing number of abalone, secondary predators such as sea stars and sea lions that rely upon them as a source of food will be forced to find other prey or starve. This could lead to a decrease in both the number of predators and a decrease in other animals that become targeted prey in the absence of the abalone. By taking abalone out of the food chain the oceans are facing serious risks, and many of these risks are, as in many situations, anthropogenic. In addition, due to their slow growth rate and inefficient spawning, abalone in general find it challenging to recover from recent traumas, such as overharvesting and disease, that have damaged populations of the mollusk (Stierhoff et al., 2010).
Abalone are economically important for two major reasons. First, abalone shells are beautiful when polished and are often used for ornaments or jewelry. Second, their muscular foot that is used to attach to substrate is considered a delicacy, making the mollusk popular among consumers. As demand has increased for abalone, though, the abalone has been at risk of being overharvested. Species like the white and black abalone are now endangered, while others such as the green and red abalone are steadily decreasing in number.
These declines have led to a number of laws that strive to protect the small number that remain from being harvested to a point where they cannot recover (Stierhoff et al., 2012). One such law is that abalone may only be harvested via skin diving, or diving under the water on one breath of air, and must be a certain size depending on the area—no SCUBA equipment may be used to harvest abalone. There are also a number of abalone fisheries that have been set up within California to help meet the increasing demand for abalone meat. Fisheries allow for the abalone to be raised and harvested through aquaculture to help mitigate the amount of wild abalone that are harvested each year (California Department of Fish and Wildlife).
That being said, the road to saving the abalone is not an easy one. Abalone are easily overharvested as they take a long time to grow and have low reproductive success. Few abalone can now be found in the two to five inch range, which shows that little significant reproduction has occurred. Off the coast of Northern California the growth rate of the red abalone is so slow that many will not be of legal harvest size for another ten years. Many fishermen poach abalone and in many fishing areas abalone shells can be found that are well below the legal size that fisherman can take, leading to the death of many undersized abalone that have not even reached reproductive age (Daniels and Floren, 1998).
Another major obstacle to abalone recovery that does not involve humans is an infectious disease called withering shell syndrome. This disease is almost impossible to detect in abalone until the mollusk actually dies. Caused by the bacterium Candidatus Xenohaliotis Californiensis, the disease has been studied in a number of laboratories and fisheries. A cure has not been found because the disease is hard to detect until the mass mortalities of abalone begin in certain areas. The disease has been seen mostly in the black abalone populations in Southern California and in the red abalone populations in Northern California. Currently there is a great push for more research into this disease and the possible ways to save the abalone population, which includes establishing more protected habitat, as well as better protecting “non-threatened” abalone species. Over the last decade, white abalone populations have decreased by as much as 80% leading many researchers to label this species as ‘functionally extinct’ along the Southern California coast (Friedman and Finley 2003).
Marine protected areas or MPAs have been created within Southern California in order to try and conserve many endangered species, including the abalone, from overharvesting, allowing for many species to recover from past harm. The goals of MPAs are to sustain the biological community in that area as well as allow for economic resources, such as sought-after fish, to recover from past traumas. There is one MPA located on Catalina Island near Two Harbors where the USC Wrigley Marine Center is located, allowing for better collection of scientific data. There are also two other MPAs on the coast of southern California that were carefully chosen to protect abalone and other vulnerable species while limiting the economic impact to the local community (Stockstad, 2010). Some believe that more research needs to be focused on where to locate MPAs so as to create the best environment to try and stabilize the abalone populations (Rogers-Bennett et al., 2000). Finding suitable locations should be a priority because researchers are now trying to culture wild abalone to foster viable offspring, especially for the endangered white abalone. Unfortunately, unless these juveniles have a protected habitat to settle and grow, such propagation efforts may be futile. Abalone play an important role in subtidal benthic marine ecosystems; without them a crucial part of the marine food web will potentially be lost forever.
California Department of Fish and Wildlife. “California Abalone Information.” Web. 24 May 2013.
Daniels, R., and R. Floren. “Poaching Pressures on Northern California’s Abalone Fishery.” Journal of Shellfish Research. Vol. 17. National Shellfisheries Association, 1998. 859–862. ProQuest. Web. 22 Mar. 2013.
Friedman, Carolyn S., and Carl A. Finley. “Anthropogenic Introduction of the Etiological Agent of Withering Syndrome into Northern California Abalone Populations via Conservation Efforts.” Canadian Journal of Fisheries and Aquatic Sciences 60.11 (2003): 1424–1431.
Rogers-Bennett, L., P. Haaker, and K. Karpov. “Selecting and Evaluating Marine Protected Areas for Abalone in California.” Journal of Shellfish Research. Vol. 19. National Shellfisheries Association, 2000. 530–531. ProQuest. Web. 22 Mar. 2013.
Stierhoff, Kevin L., Melissa Neuman, and John L. Butler. “On the Road to Extinction? Population Declines of the Endangered White Abalone, Haliotis Sorenseni.” Biological Conservation 152 (2012): 46–52. ScienceDirect. Web. 25 Mar. 2013.
Stokstad, Erik. “Science Meets Politics Off California’s Coast.” Science 327.5973 (2010): 1574–1575. www.sciencemag.org.libproxy.usc.edu. Web. 26 May 2013.
Editor’s note: Scientific Research Diving at USC Dornsife is offered as part of an experiential summer program offered to undergraduate students of the USC Dana and David Dornsife College of Letters, Arts and Sciences through the Environmental Studies Program. This course takes place on location at the USC Wrigley Marine Science Center on Catalina Island and throughout Micronesia. Students investigate important environmental issues such as ecologically sustainable development, fisheries management, protected-area planning and assessment, and human health issues. During the course of the program, the student team will dive and collect data to support conservation and management strategies to protect the fragile coral reefs of Guam and Palau in Micronesia.
Instructors for the course include Jim Haw, Director of the Environmental Studies Program in USC Dornsife, Assistant Professor of Environmental Studies David Ginsburg, Lecturer Kristen Weiss, SCUBA instructor and volunteer in the USC Scientific Diving Program Tom Carr and USC Dive Safety Officer Gerry Smith of the USC Wrigley Institute for Environmental Studies.