Temporal trends (1989–1999) in populations of Haliotis fulgens and H. corrugata (Gastropoda: Haliotidae) from Cedros Island, Baja California, Mexico

Abstract

 This work analyzes the temporal trends (1989–1999) of populations of Haliotis fulgens and H. corrugata from Cedros Island, Baja California (Mexico). The mean total density of H. fulgens in the northern (Punta Norte) and southwestern (San Agustín) points of Cedros Island showed a significant decreasing trend, while H. corrugata showed that trend only at San Agustín. Only the mean density of the legal-sized stock of H. fulgens presented a significant decreasing trend at the island. The density extracted due to fishing of H. corrugata at Punta Norte showed a significant increasing trend, but the abundance of its legal-sized stock did not show a significant decreasing trend. Authorized extraction levels for both species at Cedros Island have been lower than the maximum allowed in Mexico (30% of the legal-sized stock of each species for each fishing zone). Recent percentages of recruitment of both species are low and show no significant temporal trends. Apparently, recruitment of both species at Punta Norte decreases when the water temperature increases. A significant negative relationship was found between the physiological condition of both species and increased water temperature at Punta Norte, but such a relationship was absent at San Agustín, suggesting that the effect of warm events may differ among neighboring locations or that the populations differ in physiological tolerance. The magnitude and frequency of fluctuations in the physiological condition of both species should be taken into account when fishing quotas are assigned, since they will surely influence the magnitude and quality of spawning and natural mortality.