Temporal variation in reproductive phenology of Patella spp.: past and present.

World Congress of Malacology, Universidade dos Açores, Ponta Delgada, 21-28 de julho.

Global changes occurring in the biogeochemistry o f the oceans may influence the ecology of the biota. There is evidence that species are reacting to changes in climate through variations in the abundance and phenology with many species showing a poleward shift in their distributional range. The rocky intertidal is a relatively simple ecosystem but highly susceptible to anthropogenic activities and is thus an excellent model system for the understanding of the consequences of change in climate. This study presents a preliminary analysis of the changes in gonad phenology of Patella aspera over time. Patella aspera is being collected in various locations of the São Miguel Island (Azores) and their gonad development assessed visually using a trained observer. These data are then compared to unpublished data on gonad development collected in the period of 1985-1987 through a chi-square test of independence. Overall, in contrast to the period of 1985-87, there was a much lower number of individuals reaching maturity (gonad development stages IV and V) in 2012-2013 and there was no clear peak in spawning. In addition, the resting period appears to be starting in june, one month delayed compared to data from 1985-87. These variations are important and may affect the population dynamics of the species.