Population fecundity and reproductive capacity of some food fishes in relation to year-class-strength fluctuations

Population fecundity (PF), i.e. the total number of eggs spawned by a population during the spawning season of a given year, is the fundamental criterion of the reproductive capacity of the population. PF is defined and calculated as a sum of the eggs spawned annually by fish of all age groups composing the spawning section of a population. PF was estimated for Norwegian spring-spawning herring, Barents Sea capelin, and Northeast Arctic cod. Values of PF varied over ranges x5 in capelin, x10 in cod, and x100 in herring. The ratio of the number of fish which survive to age 3 to the total number of eggs spawned in a given year is taken to be an integrated indicator of survival conditions during these first three years of life, and defined as the survival factor (S). There levels of reproductive capacity can be identified; safe; minimal; and critical, and this information is recommended for use as a reference framework when formulating regulatory measures designed to ensure the continuity of an adequate spawning stock.