Growth and population structure of brown trout,Salmo trutta farioL., in homeothermous stream conditions from a management point of view

摘要

Abstract.A brown trout,Salmo trutta farioL., population in homeothermous stream conditions was investigated in terms of age, length‐weight relationship, annual and seasonal growth, changes in seasonal condition and specific growth rates, as management variables. The growth of this species in the stream studied was very good, with the most rapid growth in the first year of its life (15·9cm) when the juvenile trout emerged early (April) from the stream bed. The greatest specific growth rate in length was between birth and the first year of life (182·6). There was an agreement between the condition factor (K) and the growth rate. The values of K, for the juvenile trout, increased continuously because these mainly resulted from their growth through the year. The growth of the two sexes was similar except for the period from October to February when the growth of males was higher than that of females. Also the growth for both sexes was well described by the Von Bertalanffy growth model. No effect was found on the growth rate of tagged and untagged fish.The density and biomass were low, ranging between 0·008 and 0·035 fish.m−2and 1·25 and 5·63 g.m2res