The Regularity of the Spawning Season of Some Fishes

Chronobiology: implications for marine resource exploitation and management

“…In further support of this interpretation of the control of fish annual spawning rhythms is the comparison made (Cushing, 1969) between the precise spawning times of plaice, cod, herring and sockeye salmon on the one hand and the irregular spawning times of Californian sardine and Pacific tuna on the other. The last two species breed at low latitudes where seasonality is much less pronounced than in the higher latitude breeding grounds of the first four species of fish.…”

“…Whereas the four species of annual spawning fish reported by Cushing (1969) appear to spawn at a set time of year, apparently fairly precisely timed by their internal physiology, the annual spawning times of polychaetes may vary somewhat from year to year, though in a predictable manner. The latter are envisaged as being under the control of "gated" rhythms of circa-annual periodicity (Olive, 1984;Bentley et al, 2001).…”

“…Early studies of this problem sought to determine whether fish spawning seasons exhibited regularity that was in some way related to cyclical events in the environment. Cushing (1969) addressed the question using long time-series of spawning dates from fisheries records for southern North Sea plaice (Pleuronectes platessa), Norwegian herring (Clupea harengus), Canadian Fraser River sockeye salmon (Onchorhynchus nerka) and Arctic cod (Gadus morhua). Each of these fish was shown to have a characteristic spawning time of a few days only each year, and for three of the species their spawning times were constant from year to year.…”

“…Indeed, Cushing (1969) concluded that since fish can only link their spawning times to plankton production cycles in an indirect manner, it is to their advantage if they spawn at a relatively fixed season. In this way, he argued, a fish population has the best chance of profiting from the variability in the timing of the production cycle.…”

Growth rate and heterozygosity in the plaice, Pleuronectes platessa

“…In our calculations of fish age, we have assumed a nominal fertilisation date of February 14 for each year. Cushing (1969) has estimated the standard error of the mean date of spawning in the North Sea as 25 days.…”