Latitudinal gradients in growth and spawning of sea bass, Dicentrarchus labrax, and their relationship with temperature and photoperiod

0-group Sea bass, Dicentrarchus labrax, were captured in four estuarine nursery areas along the Portuguese coast, during the spring and summer of 2005. This coast has a North–South orientation which means that it is particularly suited for the investigation of latitudinal trends. Growth and hatch dates were estimated through otolith daily increment analysis. A clear latitudinal gradient in growth rates was detected. D. labrax mean growth rates were 0.48 mm d−1, 0.51 mm d−1, 0.56 mm d−1 and 0.61 mm d−1, from the Ria de Aveiro, the Mondego estuary, the Tagus estuary and the Mira estuary, respectively. A latitudinal gradient also existed in the spawning season of this species, particularly concerning its onset, which occurred earlier in the South. Analysis of sea surface temperature data from the adjacent coastal waters showed that spawning is not triggered by an increase in temperature, as has been argued in other coastal areas at higher latitudes. Photoperiod played a crucial role in the determination of spawning season at the Portuguese coast latitudinal range. The impact of future climate change on the observed patterns is also discussed.