In male sand smelt Atherina boyeri, from three coastal brackish lagoons of southern France, the duration of the reproductive season differed according to fish size: larger fish exhibited an extended reproductive season from February to August while smaller males reproduced only
from April to June‐July. Smaller and larger fish showed differences in their seasonal pattern of reserves. Through the cold season, energy content was exhausted for over‐winter maintenance and reproductive needs, and was restored just after fish ceased reproducing. In smaller
fish, however, reserves were more rapidly restored than in larger fish, and exhibited a decrease in autumn. This result suggested that small fish invested their energy into growth and winter survival rather than reproduction while older fish invested in reproduction. These results are discussed
in terms of life history Strategies.