Do capital breeders like Atlantic herring (Clupea harengus) exhibit sensitive periods of nutritional control on ovary development and fecundity regulation?

A laboratory study was undertaken to investigate whether Northeast Atlantic herring (Clupea harengus), i.e., Norwegian spring-spawning herring, exhibit a sensitive period during the feeding season in which ovary development is particularly susceptible to food availability and (or) energy reserves. Groups of herring received similar amounts of food over the restricted summer - early autumn feeding season but the food availability was varied temporally between groups. The herring, an extreme capital breeder, did not exhibit a sensitive period, as there was no difference in fecundity or ovary maturation between groups. However, individuals that did not reach a Fulton's condition factor (K) above 0.70 during the feeding season were less likely to begin ovary maturation. Those below this threshold showing ovary development began later and had a higher intensity of atresia than fish in better condition. To maximize fecundity, females recruited significantly more oocytes than they could support through to spawning, thus the oocytes were subsequently down-regulated. Some would have skipped spawning in the coming spawning season; these fish had a very low K. Taken together, this study demonstrates that this capital breeder has developed a suite of reproductive strategies to synchronize the production of the highest number of eggs energetically possible.