Oceanic and Estuarine Transport of Fish Eggs and Larvae: A Review

Abstract

Oceanic or coastal spawning grounds of fish are often distant from nursery areas. Fish larvae require appropriate currents and sufficient and suitable food during transit to reach the nursery area at the proper time, size, and condition. Meteorologic and oceanographic factors influence food availability and transport direction and time. Annual variation in these controlling factors could affect recruitment success. Certain generalizations can be made that apply to marine and estuarine systems. Reproduction occurs in a selected portion of the speciesˈ total range. Spawning often takes place close to gyral, upwelling, or other directional circulations that frequently are associated with major current systems. The coupling of spawning to natural oceanographic transport systems for eggs and larvae is advantageous to a species as long as those systems operate normally. The details of such coupling, and the consequences for eggs and larvae of deviations from usual transport mechanisms, remain poorly understood. Investigation of year‐class success requires a clearer understanding of the natural variability and periodicity inherent in these physical processes. Further research is needed to resolve these details, including environmental cues to reproductive behavior and relative importance of passive and behaviorally mediated transport; to statistically analyze atmospheric and oceanographic cycles; and to quantify transport mechanisms for spawner‐recruit models and predictions of year‐class success.

Flux of larval fish around Cape Hatteras

“…The effect of similar conditions has, in fact, been demonstrated to affect large-scale recruitment patterns at similar points where boundary currents converge (see Cowen 1985;Caputi et al 1996). The distribution of fish larvae with depth is known to affect retention and export, and behavior affecting distribution is probably selected for on the basis of mechanisms common over a species range (Norcross and Shaw 1984;Boehlert and Mundy 1988;Govoni and Pietrafesa 1994). It is not likely, therefore, that many species can respond evolutionarily to such a highly variable flow regime, at the edge of their range, in such a way as to prevent episodic expatriation.…”

Is the timing of spawning in sparid fishes a response to sea temperature regimes?

“…For example, if timing of spawning and subsequent recruitment changed, reefs or estuaries relying on seasonal hydrographic patterns for larval supply could see impaired recruitment and/or the recruitment of diVerent species (Gucinski et al 1990). In addition larvae relying on seasonal hydrographic patterns for transport to juvenile habitats, could be transported to inappropriate areas (Norcross and Shaw 1984). This is because the appropriate distribution of eggs and larvae requires precise coupling between spawning and oceanographic transport systems (Norcross and Shaw 1984).…”

“…In addition larvae relying on seasonal hydrographic patterns for transport to juvenile habitats, could be transported to inappropriate areas (Norcross and Shaw 1984). This is because the appropriate distribution of eggs and larvae requires precise coupling between spawning and oceanographic transport systems (Norcross and Shaw 1984). Such changes in recruitment patterns could lead to major shifts in Wsh communities and patterns of biodiversity.…”

“…These are not mutually exclusive, and each category of reasons could operate either through its eVect on adults, gametes, eggs, larvae, juveniles, or a combination of these. Ecological factors such as predation, competition, or food availability (quantity or quality), can inXuence the timing of spawning (Johannes 1978;Norcross and Shaw 1984). For instance, spawning of the herring, Clupea harengus, seems to be timed so that larvae hatch at times when phytoplankton abundances are likely to be high (Winters and Wheeler 1996).…”

“…A spawning period during or subsequent to this time would be likely to optimize reproductive output. Perhaps even more likely, spawning may be constrained to coincide with environmental conditions suitable for gametes, eggs or larvae, or targeted so that juveniles are produced at a time when conditions are suitable for survival and growth (Bye 1984;Norcross and Shaw 1984). For instance, spawning of the puVer, Takifugu niphobles, is timed to both accommodate the needs of developing embryos and to provide the conditions needed for successful hatching (Yamahira 1997).…”