Reclutamiento del abulón azul (Haliotis fulgens) en baja California, México, y su relación con la temp eratura del mar

Current abalone landings in Baja California (BC), Mexico, represent 7% of those observed in 1950. Such catch reduction supposes that the populations are far below the stock size estimated for the first half of the 20th century; therefore, at present, abalone populations could be governed by density independent processes. In order to test this hypothesis, two stock-recruitment models (Ricker, and Beverton and Holt models) were fitted to juvenile and adult historical data (1997-2008) of green abalone (Haliotis fulgens). Likewise, three non parametrized models (linear, exponential and polynomial) were fitted to local sea surface temperature data (SST) versus observed recruitment. With either Ricker or Beverton and Holt models we found no significant relationship between adult stock size and recruits. Regarding the relationship between SST and recruitment, the best model was a parabolic one (R2= 0.5, p<0.01), indicating the existence of an optimum temperature around 21°C with lower recruitment values in 19 and 23°C. The weak stock-recruitment relationship and the population dependence of environmental factors might be the result of density- independence processes, which tend to increase the population variability of exploited resources at low population levels, as it is the case of the green abalone in BC. On the other hand, given that the California Current System entered into a multidecadal cold phase since 1997, the recruitment of green abalone will probably decrease in the forthcoming years. A continuous monitoring of recruitment for this population may prove key for future management.