Feasibility of intertidal bottom culture of the penshell Atrina maura in Bahia Magdalena, Baja California Sur, Mexico

Variable and declining catches, high prices and a growing demand have raised interest in the cultivation of penshells in Mexico, and recent studies showed that Atrina maura has fast growth rates and is a potential candidate for aquaculture in Baja California Sur. This study aimed to generate more information on growth, production and mortality of A. maura and to evaluate if a low cost intertidal bottom culture can be economically feasible. Wild specimens were planted into two plots at two different tide levels in a mangrove channel called Estero San Buto, in Bahia Magdalena, Baja California Sur, Mexico. From September 2007 to May 2008, size increment data was recorded monthly, as well as weight, mortality and environmental conditions. From the data obtained and interviews with aquaculturists about costs and potential benefits, a bioeconomic model was constructed to evaluate the profitability of the investment. Growth data from A. maura was fitted to the specialized Von Bertalanffy model, a fixed L_∞=33.5 was used and the growth parameters were calculated as K=0.48 and 0.35 for the lower and mid-intertidal, respectively. Muscle and gonad condition indices showed significant correlations with temperature. Gonad maturation of A. maura initiated from January to March and the main spawning season started at the end of March. Survival after transplantation from suspended trays was high (99%) and after eight months of culture the average survivorship was 78%. The bioeconomic model simulating a 14year culture operation showed that the main costs were related to labor and that the capital equipment costs were high during the first and eighth year, due to the lifespan of Nestier trays. A batch of 200,000 seeds each year was needed to achieve positive returns under the study conditions, with a payback period of seven years. The higher risk associated with longer periods of culture would probably discourage fishermen from this type of investment. The study highlights the importance of considering economic aspects before committing to this type of venture.