A note on growth and mortality of trout, Salmo trutta L., in afferent streams of Windermere

Trout were sampled in six afferent streams of Windermere during the spawning season. The main migration of adult trout into the streams took place during early November. Length‐weight relationships and scale‐fish length relationships are given. There was no significant difference in length for age or sex between cohorts within streams. Three groups of fish could be identified depending on whether the fish entered the lake at 1+, 2+, or 3+ years. The percentage number of the population entering the lake at each of these ages was 16, 70 and 14%, respectively. After the fish had migrated from the streams their growth in length fitted the von Bertalanffy growth model. Fish entering the lake at 1+ and 2+ years had similar A.95 values (6·31 and 6·97 years) as the latter grew slightly faster in the lake. Those entering the lake at 3+ years grew at a slower rate to the other two groups but achieved a longer ultimate length. Faster growing fish had higher instantaneous mortality rates. Twenty‐eight to 29% of the males remaining in the stream at 1+ years became sexually mature. Faster growing females became sexually mature earlier. Only those fish which entered the lake at 1+ years grew close, during their early years before sexual maturity, to the theoretical maximum given by Elliott's model.