Size-Selective Harvesting and the Long-Term Effect of Reduced Body Size in Rocky Intertidal Gastropods

EPA Grant Number: FP916322
Title: Size-Selective Harvesting and the Long-Term Effect of Reduced Body Size in Rocky Intertidal Gastropods
Investigators: Fenberg, Phillip B.
Institution: University of California - San Diego
EPA Project Officer: Michaud, Jayne
Project Period: January 1, 2004 through December 31, 2006
Project Amount: $103,444
RFA: STAR Graduate Fellowships (2004) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Aquatic Ecosystems , Fellowship - Aquatic Ecology and Ecosystems


Humans have harvested marine organisms from rocky shores since prehistoric times, but exploitation of these resources is far more intense and wide-ranging today compared to subsistence collecting in the past. Because humans preferentially select the largest individuals in a population for consumption, an overall reduction in body size of the harvested species is to be expected. Indeed, size-selective harvesting has resulted in a significant decrease in mean body sizes of a number of rocky intertidal gastropod species in southern California over the last century (Roy, et al., 2003), but the effects of such declines on the life history and population biology of individual species remain poorly understood. The Owl limpet (Lottia gigantea) is one of the most highly exploited rocky intertidal mollusc species in California and its unique life-history characteristics (e.g., L. gigantea sequentially changes sex from male to female, with the large size classes being predominantly female) provide an opportunity to study the long-term effects of size-selective harvesting on population dynamics. The objective of my research is to use L. gigantea as a model organism to study the effect of size-selective harvesting on the ecology and population viability of rocky intertidal gastropods and other marine invertebrate species. I will test the hypotheses that human exploitation of L. gigantea leads to: (1) temporal and spatial changes in body-size, growth rates, and longevity; (2) alterations of sex ratio and reproductive output of exploited populations; and (3) changes in community structure of the intertidal habitat of California. I will use this information to investigate the long-term viability of exploited populations of L. gigantea along the California coast.


I will use the museum collections (dating back to the mid 1800s) for L. gigantea to obtain a historical baseline of body size, growth rates, and ages of individuals within populations. I also will survey and quantify size, growth rate, age, sex ratio, and reproductive output of L. gigantea in modern populations. Using a comparison of historic versus modern data from exploited and nonexploited sites, I will quantify the ecological effects of exploitation in L. gigantea. I will quantify the extent of population connectivity using genetic techniques. This will help determine the degree of connectedness between the majority of highly exploited sites and the few well protected reserves.

By focusing my study on one of the most exploited species of intertidal molluscs in California (L. gigantea), I hope to develop a better understanding not only of how human harvesting is affecting this species but also of the future demographic trajectories of these populations. Once completed, my study should provide the scientific basis for the development of better management strategies for this and related species.

Supplemental Keywords:

Supplemental Keywords: fellowship, Lottia gigantea , intertidal, ecology, gastropods, limpets, size-selective harvesting,, RFA, Scientific Discipline, ECOSYSTEMS, Ecosystem Protection/Environmental Exposure & Risk, Aquatic Ecosystems & Estuarine Research, Aquatic Ecosystem, Aquatic Ecosystems, Environmental Monitoring, Ecology and Ecosystems, coastal ecosystem, aquaculture, ecosystem monitoring, intertidal gastropods, marine biology, size selective harvesting, anthropogenic impact, coastal environments

Relevant Websites: Exit

2004 STAR Graduate Fellowship Conference Poster (PDF, 1p., 143KB, about PDF)

Progress and Final Reports:

  • 2004
  • 2005
  • Final