Survival and growth of salmon, Salmo salar (L.), planted 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 1980
• Subjects: Salmo salar
• Online Access: http://dx.doi.org/10.1111/j.1095-8649.1980.tb03734.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1095-8649.1980.tb03734.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1095-8649.1980.tb03734.x

Salmon eggs and unfed fry were planted in reaches (total length 2.8 km, mean width 4 m) of a Scottish stream between 1971 and 1977 and their subsequent progress was studied by sampling 16 sections (areas 38–126 m 2 ) of the stream. Brown trout are the only fish which spawn in the stream, waterfalls and a dam near its mouth preventing adult salmon and sea‐trout passing upstream. There were no restraints on the downstream movement of fish except in 1977, when a fry trap was operated. In 1971 and 1974 boxes each containing 300 eggs were buried in groups of 3–6. In other years fry were evenly distributed at 3.6–29.3 m −2 . At the end of the first growing season, salmon occurred at decreasing population densities for a distance of 600 m below the plantings, but after two growing seasons there was little remaining indication of their pattern of dispersion when planted. Rates of survival between planting and the end of the growing season were 9.4–31%. Survival when eggs were planted (11.1–14.8%) was not affected by the numbers planted together at one point (900–1800) or the distance apart of groups of boxes (10–85 m). When fry were planted the instantaneous mortality rate ( M ) of the 0 + salmon during their first growing season was related to the initial stocking density ( D p ) by the formula M = 0.00637 + 0.00444 log 10 D p . Twenty‐two to 88% of 0 + salmon present at the end of the growing season were still surviving in the stream as 1 + fish one year later. In 1973–1976 only a small number of 2 + salmon occurred, the majority having migrated between the end of the second growing season and the following spring. There were more 2 + salmon in 1977 and 1978 resulting from higher stocking densities in 1975 and 1976 and slower growth. Trout of several age classes were present but their population densities were never high (<0.6 m −2 ). Salmon reached a greater size than trout by the end of the first growing season. Their mean weight ( W o , g) at this time was inversely related to their population density ( D o No. ...