BUILDING ON STOCK ENHANCEMENT SUCCESS IN SOUTHERN CALIFORNIA: CASE STUDY OF A DEVELOPING CALIFORNIA HALIBUT Paralichthys californicus REPLENISHMENT PROGRAM  

Hubbs-SeaWorld Research Institute (HSWRI) has been involved in the stock enhancement of marine finfish in southern California, particularly white seabass (Atractoscion nobilis), for over three decades. In recent years, there has been increasing interest in applying the expertise gained from this to other depleted species. Here, the development of a new angler-funded replenishment program in this region is outlined.

Eighteen candidate species were initially assessed based on management agency and stakeholder input, and a selection procedure involving a broad set of stocking suitability criteria was developed. California halibut (Paralichthys californicus) emerged as a clear front-runner, and HSWRI began focusing research efforts on the technical and regulatory requirements of stocking halibut. An extensive review of flatfish stock enhancement, including large-scale programs for the congeneric Japanese flounder (Paralichthys olivaceus) and experimental releases of species in the US and Europe, was undertaken to identify global stocking practices, successes and information gaps. A quantitative model was also parameterized to represent halibut life-history and fishery characteristics in southern California, to explore population responses to various release strategies and scenarios (e.g. size-at-release, direct release vs. conditioning, economic considerations).

The availability of such diverse background research provides a unique basis for development of the current program-both the literature and theoretical analyses suggest that stocking of California halibut has the potential to be successful. The next phase of our research is to empirically test these findings through a series of experimental releases, and a preliminary broodstock management plan (conservatively assuming spatial population structure) has been put in place in support of this.