UC Marine Council

Southern California has historically supported 5 species of commercial abalone. Within the past fifteen years, all of these species have seen dramatic declines in population. Now, abalones occur at such low population densities that in 1996 the California Fish and Game Commission was forced to order an emergency closure to all abalone harvesting in southern California. For abalones, fertilization takes place externally after males and females spawn their gametes into the water column. Currently, the numbers of mature adults are so low that fertilization may be a critical bottleneck for population recovery. In this proposal, we seek to determine the effects of population size and distribution, and hydrodynamic conditions on fertilization success. This will be accomplished through three phases of this project: (i) through abalone cruises sponsored by the California Department of Fish and Game, we will take flow measurements and determine the population densities and distributions of naturally occurring abalone populations in the Channel Islands, (ii) measurements, taken at sites that have historically supported large populations of abalone, will allow us to scale our laboratory flume experiments to examine the effects of fluid motion on the transport and mixing of gametes, and (iii) we will determine the necessary number and spacing of spawning abalones for successful fertilization, under conditions similar to those in the field. The first phase of this project will bring critical information on the current abalone population demogrpahics, and allow us to scale our laboratory experiments. The second and third phase of this project will allow predictions to be made on the minimum population size necessary for successful fertilization, and the influence of fluid motion and habitat on fertilization. Such information will be critical for marine resource managers to establish proper procedures to aid in the recovery of the remaining abalone populations in southern California.