期刊名称：Informationen aus der Fischereiforschung (Formerly Informationen für die Fischwirtschaft aus der Fischereiforschung)
印刷版ISSN：1860-9902
电子版ISSN：1861-2164
出版年度：2011
卷号：58
出版社：Bundesforschungsanstalt für Fischerei
摘要：E nvironmental changes may have an impact on life conditions of the fish, e.g. food supply for the fish. The prevailing envi-ronmental conditions apply evenly to all age groups of one s tock. Small fish have high growth rates, whereas large fish grow with low rates. But, it can be shown on the basis of the von Bertalanffy-growth model that it is sufficient to know only the growth rate of one single age group to compute the growth rates of all other age groups. The growth rate of a reference fish GRF (e.g. a fish with a body mas s of 1 kg) was introduced as a reference growth describing the current food condition of all age groups of the stock. As an example a time series of the reference- growth rate of the northern cod stock (NA FO, 3K) was computed for the time span 1979 to 1999. For the northern cod stock it can be observed that environmental conditions caus ed growth rates below the long-term mean for seven years in a row. After a prolonged hunger period the fish s tock collapsed in 1992 also by the impact of fisheries - and this was probably not a coincidence. Now, with the reference-growth rate GRFa sim-ple and handy parameter was found to summarize the influence of the environmental conditions on growth and other derived models and therefore makes it easier to compute the influence of environmental changes within s tock assessment
