Spatial variability of the reproductive cycle and physiological condition of Patella spp. (Mollusca Gastropoda) in the NW of the Iberian Peninsula: Implications for exploitation

Abstract

The reproductive cycle and the physiological status, measured through a standardized condition index, of limpets Patella depressa and Patella ulyssiponensis were studied along the Galician coast (NW of the Iberian Peninsula) from July 2010 to June 2011. The observed data were adjusted using linear and nonlinear general models. This allowed analyzing and quantifying the influence of independent factors, such as individual size and degree of wave exposure, on the cycles. Populations of P. depressa showed mature individuals nine months a year with a resting period from June to September. The amplitude of the fertile period increased with limpet size and with wave protection. On the other hand, the condition index decreased with increasing limpet sizes and, for a given size, it was higher in sheltered areas than in exposed ones. P. ulyssiponensis showed mature individuals eleven months a year with a small resting period in May or June. The amplitude of the reproductive cycle increased with limpet size but this variable did not show any significant influence on the condition index. No size/sex relation was observed either for P. depressa or P. ulyssiponensis. The results have contributed some valuable information to help design exploitation plans: Given that the limpet exploitation in these coasts is multispecific and includes a third species Patella vulgata, in case the resource is intended to be managed by temporal closures during the fertile period, it should be established following the fertile period of P. vulgata, which is restricted to 3–4 cold months, while the studied species show mature individuals throughout much of the year. It is recommendable to not harvest the largest individuals, since energetic condition decreases with size; in addition, larger individuals show longer maturity periods and might therefore contribute to recruitment to a greater extent. Size distribution observed in sheltered areas showed a lack of juveniles. This can be pointing to lower recruitment, suggesting caution in order to avoid overexploitation in these areas.