Influence of water depth on dispersion of juvenile salmonids, Salmo salar L. and S. trutta L., in a Scottish stream

• Published in: Journal of Fish Biology
• Main Authors: Egglishaw, H. J., Shackley, P. E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1982
• Subjects: Salmo salar
• Online Access: http://dx.doi.org/10.1111/j.1095-8649.1982.tb03995.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1095-8649.1982.tb03995.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1095-8649.1982.tb03995.x

The dispersion of salmon and trout of 0 +, 1 + and 2 + age classes was examined by electrofishing 12 sections of a stream in Perthshire, Scotland at the end of the growing season in September to October in 1972 and 1976. In 1972 sections ranged in surface area from 21 to 122 m 2 and had volumes of 5.0–17.3 m 3 and when surveyed in 1976 surface areas were 15–106 m 2 and volumes 2.1–6.7 m 3 . In 1976 widths and areas of sections were 63–87% of the values for 1972, depths were 39–68% and volumes 28–52% of the earlier values. These differences were due to 1976 being drier and warmer. In both years, all sections contained 0 + and 1 + age classes of salmon and trout and some sections contained 2 + age salmon and trout. The total density of fish in a section ranged from 1.9 to 3.9 m −2 in 1972 and from 3.72 to 6.08 m −2 in 1976. There was an inverse relationship, significant in 1972 only, between the density of 0 + salmon and that of 1 + trout in the different sections. Densities of both 0 + and 1 + salmon in the sections were inversely correlated, and those of 0 + and 1 + trout were directly correlated, with area of water deeper than 10 cm.