Daily striae on the shell of the scallop, Argopecten purpuratus, were used to investigate its growth in a protected population within La Rinconada Bay, near Antofagasta
(2nd Region, Northern Chile), and to determine how environmental
forcings control shell growth. This sclerochronological approach was useful
to describe daily shell growth a posteriori. Mean shell growth rates were calculated
daily between February and October 1999 from shells of six specimens
harvested on 15 October 1999. A multiple regression analysis performed on
shell growth and environmental data shows that a temperature increase
stimulates shell growth whereas particulate organic carbon concentration
might be stressful above 2.5 mg L−1. The lunar cycle might also have an
effect on growth, most potent around New Moons, by synchronizing an
endogenous oscillator. The age at commercial size (90 mm) was only 10–11
months in La Rinconada Marine Reserve and the von Bertalanffy growth
parameters were K = 2.24 y−1 and H∞ = 117 mm. Differences in
shell growth performances between this study and previous ones dealing with
A. purpuratus growth may be explained by the different methods used for shell growth
modelling, higher growth rate on the seabed compared to suspended cultures,
and particular environmental forcings (e.g. El Niño Southern
Oscillation-ENSO events). Growth performance seems better during La Niña
than during El Niño events, probably because of the large temperature
increase (above the highest temperatures recorded in “normal” conditions)
and the decline in coastal upwelling (which affects food availability)
during El Niño. La Rinconada Marine Reserve appears as a very favourable
site for A. purpuratus growth, probably because of the active upwelling zone off
Antofagasta. These new insights on A. purpuratus shell growth confirm the importance of
La Rinconada Marine Reserve as an area supporting repopulation of endangered
wild stocks and scallop aquaculture in Chile.