Caretakers versus Exploiters: Impacting Biodiversity in the Age of Humans

Historical Background

In 1921, the State of California Fish and Game Commission released a report titled The Edible Clams, Mussels and Scallops of California. At the time, approximately 500 different species of clams, mussels, and scallops were found along the United States Pacific coastline. Over a century ago, the report notes that bivalves along the California coastline were “a source of food now distinctly neglected.⁷” A list of 43 species found along California coasts deemed to be edible by humans includes a variety of clams, mussels, geoduck, cockles and oysters (Figure 2). Goals of the report included a survey of the variety and abundance of edible species, to be a comprehensive guide for citizens to identify types of bivalves, and also to promote “the possibilities of food in the clams, mussels and other bivalves of the California coast, for these animals are at their best when freshly taken.⁸” People were encouraged to educate themselves about the varieties of bivalves such that “the attention of the camper to the interesting adaptations and beauties of these little known animals, his pleasure in the great out of doors will be correspondingly increased.”⁹ The guide also includes recipes for clam and tomato bisque, fried clams, fried croquettes, clam sauce, steamed mussels (or clams), savory clams en casserole, and scalloped clams.

Figure 2: List of Edible Bivalves of California published in 1921.¹⁰

California’s Marine Biotoxin Monitoring Program began in 1927 as a response to a large paralytic shellfish poisoning (PSP) event. Over a hundred people became ill and several died after eating contaminated wild mussels. The California Department of Public Health established an annual mussel quarantine prohibiting the collection and resale of mussels from California coastlines in 1942 from June 1 through September 30. The current annual mussel quarantine now includes the period from May 1 through October 31, and dates can be extended if necessary, based on detected levels of marine biotoxins. The quarantine period is determined by examining historical records which show this time frame typically has higher levels of biotoxins and 99 percent of all PSP illnesses in California since 1927 have occurred during these months.¹¹

Nearly a century after the California report encouraging the public to consume more bivalves, on July 1, 2020, the California Department of Public Health issued a warning advising consumers to not eat sport-harvested mussels, clams, or whole scallops from the waters in San Francisco, San Mateo, Santa Cruz, and Monterey counties in Northern California. Naturally occurring biotoxins along the California coastline, and in waters and coastlines across the United States and world have increased in prevalence. Changes in climate and increased water temperatures have enabled biotoxin producing phytoplankton, algae, to expand their territory and proliferate. Bivalves and small fish consume these phytoplankton; although many species are unknown to be harmed, they become reservoirs for biotoxins. Larger species in the food web such as crustaceans, sea lions, otters, and humans can consume contaminated sea creatures and suffer seafood borne illnesses.