Optimizing abalone outplant strategies using larval Haliotis kamtschatkana in the San Juan Archipelago, Washington

Prior studies testing the use of Haliotis kamtschatkana larvae as a means of stock enhancement in the San Juan archipelago have shown no success in inducing larvae to settle in densities required for successful reproduction. I conducted an experiment to test the effectiveness of new methods for outplanting larval abalone in hopes of creating a protocol Puget Sound Restoration Fund could use to restore wild populations. Using two sites within the San Juan archipelago, I outplanted abalone into pre-constructed larval abalone modules (LAMs) and sampled over four months, testing retention strategies. Three types of LAMs were used at each site to determine whether 125µm Nitex tenting was necessary for retention of larvae after outplanting. In total, nine LAMs were placed at each site: three with Nitex tenting (tented LAMs), three without tenting (open LAMs), and three which received no larval abalone (control LAMs). All larval abalone were treated with 5µM of settlement cue gamma-aminobutyric acid (GABA) at time of outplanting to stimulate metamorphosis into their benthic life phase. Larvae of the same families that were outplanted were also reared in LAMs at Shannon Point Marine Center so that survival could be compared to survival in field LAMs and so that emigration could be estimated. Shell lengths of field abalone were measured four months after outplanting and were compared to hatchery reared individuals of the same families to better understand if hatchery life compromises early growth. Four months after outplanting abundance counts of settled pinto abalone were significantly greater (p < 0.001) in LAMs with 125µm Nitex tents encasing the LAMs for 24 hours after seeding, compared to open and control LAMs. Open LAMs had some settlement (0-12 abalone), while tented LAMs all contained settled juveniles (16-35 abalone). Control LAMs (which had not been seeded during outplanting) remained unsettled by any abalone, suggesting no adult reproductive abalone were present at my study sites. Emigration measurements from laboratory LAMs showed 8% (tented) and 14% (open) of total seeding densities settled on aquarium walls during final sampling, often clustered together. Shell length measurements during final sampling showed no size difference in outplanted abalone compared to hatchery controls suggesting hatchery conditions do not stunt growth rates of newly settled pinto abalone, however, more research needs to be done in order to better understand if behavioral differences exist between hatchery-reared juveniles and juveniles that were outplanted as larvae. In conclusion, I believe outplanting pinto abalone as larvae has significant potential to supplement current wild stocks in the San Juan archipelago as a cost-effective alternative to traditional juvenile outplanting.