California Sea Grant College Program

Marine protected areas (MPAs) are widely used to rebuild depleted populations for exploited species, but their effectiveness hinges on adequate knowledge of the factors dictating population dynamics for target organisms. Estimates of connectivity via larval dispersal often are included in MPA design, but movement patterns, habitat associations, and habitat-specific survival rates of juveniles and adults, which often are unknown, also will influence MPA effectiveness. California spiny lobsters (Panulirus interruptus Randall) are the target of intense commercial and recreational fishing in southern California, but we lack basic information about home range and habitat use of lobsters to determine if MPAs planned for the region will enhance abundance. Working within and outside of the La Jolla Ecological Reserve (LJER) in southern California, we (i) quantified lobster movement patterns and home ranges over short (nightly – weekly) and long (1 – 14 months) time scales using acoustic telemetry, (ii) surveyed lobsters to determine day and night habitat associations, and (iii) tethered lobsters to assess habitat-specific predation risk. Lobsters exhibited high site fidelity, proclivities for homing, and small home ranges (geometric mean of 651 m2 and 5,912 m2 per week based on 50% and 95% Kernel Utilization Distributions (KUDs), respectively) that encompassed only a fraction of a small MPA, even over periods of several months. Lobsters were strongly associated with rocky habitat during the day (when in shelters) but were associated with the red algae Plocamium cartilagineum at night (when feeding). Lobster relative survival rates were high across vegetated and unvegetated habitats at night, but lobsters were protected from predators by surfgrass (Phyllopsadix torreyi) habitat during the day. Our results highlight the need to consider how movement patterns vary over short and long time scales, and how patterns of habitat use may vary from day to night for nocturnally active species such as spiny lobsters when planning MPAs.