• Multiple spawning;
  • batch fecundity;
  • ovulatory rhythms

The strategy of multiple spawning is examined in several commercially important species—in particular turbot, Scophthalmus maximus (L.); halibut, Hippoglossus hippoglossus (L.); cod, Gadus morhua L.; and northern anchovy, Engraulis mordax Girard. Aspects of special relevance to fishery science and commercial and experimental cultivation are discussed. These include changes in batch fecundity and egg size as the spawning season progresses; the timing and methodology of fecundity estimations; ovulatory/spawning rhythms; the effect of temperature on the ageing rate of retained ovulated oocytes and the interovulatory period; ovulation prediction in hand-stripped broodstocks to facilitate the collection of good quality, freshly ovulated eggs, and the effect of maternal stress on the ovulatory/spawning rhythm. The implications of these phenomena are discussed in terms of recommended practices for the culturist, experimentalist and fisheries scientist.