Some aspects of the biology of the speckled trout Salvelinus Fontinalis (Mitchill) 1815, in the waters of insular Newfoundland

Abstract

Some broader aspects of the biology of speckled trout in the waters of insular Newfoundland were examined in the light of both geographic separation and variation in habitat type. -- Size composition, age composition, maximum sizes attainable and growth rate were found to be dependent on habitat size, with mean size, mean age, and rate of growth increasing with increased spatial allotment. -- Growth of Newfoundland trout taken from small bodies of water is comparable to that of its mainland counterpart in a similar habitat; in larger bodies of water, however, mainland trout show a faster growth rate. -- The length-weight relationship was determined for Newfoundland trout, and the cube law was closely followed. The ratio of weight to length reaches a maximum or optimum and then decreases as the habitat progresses in size from stream to lake. Seasonally, there is an increase in the weight to length ratio from spring to fall. -- Condition factors were calculated to indicate the suitability of the different habitats. The mean condition coefficient bears a similar relationship to habitat size as the length-weight relationship. The condition factor was found to either increase or decrease with increased length, with a decrease indicating a deficiency or limitation of the environment. -- Meristics were used to determine population differences due to geographical separation. Vertebral numbers followed Jordan’s Rule. Gill raker number was correlated with fish size and geographical comparison was of little value. Dorsal and anal fin ray counts showed no consistent variation with fish size of latitude. There was no sexual dimorphism in meristic counts. -- Male trout mature sexually at both an earlier age and smaller size than females. The relationship between egg number and size and age was examined for Newfoundland trout and compared with data for mainland trout. There was little evidence of a deviation from the 1:1 sex ratio under natural conditions. -- The food of speckled trout was examined both qualitatively and quantitatively. The food includes the adults, larvae, and pupae of terrestrial insects, the larvae, annelids, and forage fish. Benthic organisms are generally utilized relatively more than either pelagic or terrestrial forms. Food intake decreases from spring to fall, and forage fish, when available, form the bulk of the diet of larger trout. -- Speckled trout were found to be heavily parasitized by five macroscopic forms, one of which (Salmincola sp.) has been shown to cause death. Two others (Echinorhynchus lateralis and Philonema sp.) were shown to at least cause serious injury. The known distribution of Philonema sp. and Argulus canadensis was extended.