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|dc.contributor.author||Larrañeta, M. G.||-|
|dc.identifier.citation||Oceanides 11: 55-187 (1996)||-|
|dc.description.abstract||The main theoretical problem in marine fisheries research is the uncertainty surrounding recruitment. The relationship between the number of fertile eggs and the generation to which they give rise, normally called the >stock-recruitment relationship>, is a problem which embraces a wide variety of aspects, all of them included in marine ecology. In this work, the biological and ecological basics of the pre-recruit stages are dealt with first. There is a general negative exponential relationship between temperature and age of hatching in the planktonic eggs of fish; those which do not float hatch at an older age. There is also a negative exponential relationship on the one hand between the time of hatching and first feeding, and on the other with temperature. The importance of starvation and predation as factors discussed. Cannibalism does not seem to be a significant factor in compensatory mortality except in Peruvian anchovettas. Hypotheses concerning fluctuations in recruitment are reviewed. On short time scales, they are explanations of the success of feeding by pre-recruits due to hydrographic and meteorological causes. On longer time scales, they related variations in recruitment to geophysical, astronomical and climatic factors. Parametric models of the stock-recruitment (S/R) relationship are examined. The best way to introduce environmental factors is by linear regression. Ussing this regression, the amount of variance accounted for by the environmental factors can be studied. Contrary to what is generally accepted, the real instrinsic population parameter is density-independent, while the density-dependent will always be related to the environmental factors which determine the food density. The use of non-parametric models simplifies the study of S/R. All of them have the drawback that they ignore the ecological aspects of year class success. The physical factors (salinity, temperature, wind, etc.) are really >predictors> of the pre-recruit survival values. The geophysical and astronomical factors (nodal tides, polar motion, length of day, etc.) are predictors of the ecological conditions in a particular area. Possible consequences of the risk of greenhouse warming are examined. Alternation of species is a typical phenomenon in the pelagic environment. The principle cause is due to the adults of the dominant species feeding on the eggs and larvae of the secondary species. If the biomass of the dominant species is strongly reduced, by at least half, the secondary species eventually becomes dominant. A massive increase in pelagic species by predation on their eggs and larvae. The alternation of demersal species is less common. The classical collapse of a fishery begins with an enormous recruitment, low recruitment follows, biomass is drastically reduced, and the collapse is maintained if the species becomes sub-dominant. The magnitude of recruitment depends on the ecological conditions in which the pre-recruits develop, but also on the energy stored by the parents. Life-history strategies differ; in pelagic species growth is initially rapid, and variations in energy consumption are reflected in fecundity, but in demersal species variations in energy comsumption influence growth rather than fecundity. In semiparous species, post-spawning survival is sacrified.Different patterns of evolution of the S/R relationship in fish are described. The hypothesis of Shepherd & Cushing (1990) concerning the influence of stochastic processes on recruitment variability is only supported in a minority of the S/R patterns studied.||-|
|dc.title||Ecology of the stock-recruitment relationship in marine fish||-|
|dc.title.alternative||Ecología de la relación stock-reclutamiento en los peces marinos||-|
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