The goal of this project is to gather essential fisheries information needed to evaluate the feasibility of a sustainable fishery for the brown box crab, Lopholithodes foraminatus, in California. Our objectives are threefold and include: 1) generating basic life history information on growth; 2) assessing reproductive capacity; and 3) exploring the trophic position and role in ecosystem functioning. We will use a combination of field surveys and laboratory analyses to achieve our objectives. For our first objective, we will determine molting seasonality by molt staging a monthly sample of crabs from each region and calculating the proportion of pre- and postmolt animals. Growth rates will be investigated through analysis of gastric mill growth bands, size frequency distributions, and studies of molt increments and intervals. We also will determine size at maturity (physiological and functional) for each region through examination for mature gametes and readiness to mate as determined through presence of eggs for females and setae wear on gonopores for males. To access reproductive capacity (Objective 2), we propose to evaluate reproductive seasonality, fecundity, and brood duration and mortality. Reproductive seasonality will be determined through the analysis of reproductive status for the same samples used for evaluation of molting seasonality. Size-specific fecundity and brood duration and mortality will be assessed through laboratory studies on subsamples of gravid females. Lastly, we propose to investigate the trophic position of L. foraminatus through laboratory studies using a combination of stomach content analysis (SCA) and stable isotope analyses (SIA). Together these methods will provide information on recent (SCA) and cumulative (SIA) diets over time, something not previously evaluated for this species. This information will help identify the role box crabs play in deep water ecosystems.
We will work with commercial fishermen to obtain samples of box crabs throughout the year. We will rely on monthly samples from trappers that are interested in this fishery, including those that have submitted a request for an experimental fishing permit. We also will seek supplemental samples from trawl fishermen that may encounter box crabs while they are fishing. Obtaining samples from both gear types will ensure information on active and inactive stages. Crabs caught in traps represent the target of the fishery and include only active crabs – those that are attracted to bait and may enter traps. Trawls are able to sample inactive animals.
The information we gather on growth, maturation, reproduction and trophic level will be synthesized to summarize the life history of the box crab in California and potential implications for management. We will hold a workshop at the end of the project to share the results with fishermen, resource managers and others interested in the fishery and to discuss management options and future research needs.