Читать книгу Fish and Fisheries in Estuaries - Группа авторов - Страница 41

Recruitment in estuarine fish is variable, with annual variability sometimes exceeding a factor of ten. In a review, recruitment success of anadromous and estuarine fishes varied on a scale similar to that for marine fishes (Rothschild & DiNardo 1987). Recruitment levels and patterns over time are often adopted by fishery managers as measures of reproductive success. It is probable that estuary‐dependent spawners and pre‐recruit fishes that utilise estuaries have evolved and are adapted to the variable habitats and unstable water‐quality conditions that are common in estuaries and which can threaten reproductive success. On the other hand, the high productivity of estuaries may act positively to support reproduction and recruitment. The nature of spawning migrations by adults of estuary‐dependent fishes and cues that trigger spawning are properties that have evolved to ensure eggs are spawned in appropriate habitat and under favourable environmental conditions (Secor 2015). The sources of variability that act on eggs and larvae, followed by processes acting during the lengthy life stages of juveniles and, finally, adult spawning processes combine to generate the observed variability in reproductive success.