On the Biology of the Stone-Loach Nemacheilus barbatula (L.)

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Abstract
Stone-loach fish, Nemacheilus barbatula, is locally distr. in vicinity of Windermere, mainly in lower reaches of rivers and streams and is usually absent from lake shores. Collections at 2 stations were made at monthly intervals from Nov. 1948 to July 1950. Ext. and int. characters and obs. on behavior and movement of fish are descr. Fish is nocturnal, lying dormant under stones in daytime. Field obs. suggest that fish is tolerant of organic pollution. Age was detn. from otoliths and supported by length-frequency data. Fish which have attained 2 years grow faster in beck than in lake, a difference probably associated with eating more food. Mean length, in cm, attained at end of each yr. of life is as follows 4.7 (0), 8.0 (I), 9.9 (II), 10.8 (III), 11.4 (IV), 11.5 (V). For first 2 yrs. of life fish in Esthwaite Water and Black Beck grow similarly, but in third yr. of life, fish in Black Beck grow significantly faster than fish in ''Esthwaite Water. Male and female grow at a similar rate throughout life. Food, which consists chiefly of chironomid larvae, varies with size of fish, season of yr., and place of capture. Amt. of food eaten seasonally showed a winter minimum at both stations, but whereas in Black Beck there was a summer maximum, in Esthwaite Water there were maxima in spring and autumn. Spawning takes place in May in Lake District. Some fish attain 5.0 cm by winter of their first yr. of life and spawn when 1 yr. old; others less than 5.0 cm do not spawn until next season.