Black abalone (Haliotis cracherodii) population structure shifts through deep time: Management implications for southern California's northern Channel Islands

Abstract

For over 10,000 years, black abalone ( Haliotis cracherodii ) were an important resource in southern California, first for coastal Native Americans, then beginning in the nineteenth century, as one of the state's first commercial shellfisheries. By 1993, after years of heavy fishing, rising sea surface temperatures (SST), and the spread of withering syndrome (WS), black abalone populations declined dramatically, resulting in the closure of the Alta California fishery. After nearly 25 years of management and recovery efforts, black abalone are showing signs of ecological rebound along some Channel Island shorelines. These include the presence of juvenile abalone and increasing densities, largely from data collected by Channel Islands National Park (CINP) monitoring efforts that began in 1985. In an effort to apply deeper historical perspectives to modern fisheries management and restoration, we analyzed black abalone size data from San Miguel Island at prehistoric and historical archeological sites spanning the last 10,000 years and compared these populations to those described by CINP biologists between 1985 and 2013. We found a statistically significant relationship between SST and black abalone size distributions during the ancient record, along with dramatic shifts in population size structure toward larger individuals between the nineteenth century and modern periods. A pattern of larger mean black abalone sizes was identified during warm SSTs, when compared against intervals of cooler SSTs. Synthesis and applications. Our study provides a deep historical perspective of abalone population size distributions, patterns within these distributions through time, and parallels to modern abalone populations. Our results may help managers determine whether the current (and future) size and age structure of intertidal black abalone populations around the northern Channel Islands are “natural” and healthy, measured against the 10,000 year history of black abalone fishing in southern California.

Unveiling the Ecological Applications of Ancient DNA From Mollusk Shells

“…High mortalities due to infections by the bacterium Candidatus xenohaliotis responsible for the Withering syndrome devastated abalone populations (Crosson et al, 2014) and contributed to the low genetic diversities and population differentiations observed in H. cracherodii and H. rufescens today (Gaffney et al, 1996;Burton and Tegner, 2000;Hamm and Burton, 2000). Conservation efforts are focused in restoring and protecting abalones in the Pacific: shore picking of H. rufescens is allowed only under strict rules, and fishing of H. cracherodii (commercial or recreational) have been suspended (Haas et al, 2019). Management and conservation plans would greatly benefit from shell aDNA analyses that could help better understand the dynamics of genomic diversity and distribution for the two species, the effects of exploitation, infection and predator recovery, and complement archeological studies aimed at helping in abalone restoration (Braje et al, 2009(Braje et al, , 2016Hofman et al, 2015).…”

Bills of Fare, Consumer Demand, Social Status, Ethnicity, and the Collapse of California Abalone

“…For decades, abalone were freed from predation pressure as human harvest dwindled and sea otter (Enhydra lutris) communities were driven to the brink of extinction during the historical fur trade. Abalone populations exploded in coastal California, reaching unprecedented sizes and numbers in intertidal and subtidal systems (Braje et al 2016;Haas et al 2019).…”

Limited genomic signatures of population collapse in the critically endangered black abalone (Haliotis cracherodii)

“…In addition to playing a key ecosystem role, the abundance, accessibility, and size of black abalone have made them a frequent target of human populations for at least 13,000 years (Haas et al, 2019). The meaty foot has served as a food staple for indigenous Californians, and their iridescent shells have been used as adornments, tools, cultural currency, and religious symbols (Erlandson et al, 2008;Kelley & Francis, 2003;Sloan, 2003;Vileisis, 2020).…”