The environmental requirements of Atlantic salmon, Salmo salar L., during their passage through the Thames Estuary, 1982–1989

• Published in: Journal of Fish Biology
• Main Authors: Alabaster, J. S., Gough, P. J., Brooker, W. J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1991
• Subjects: Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.1111/j.1095-8649.1991.tb03162.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1095-8649.1991.tb03162.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1095-8649.1991.tb03162.x

An examination of data on both water quality in the Thames Estuary and on the count of salmon. Salmo salar L . trapped in fresh water above the head of the tide in 1982–1989, was carried out to establish statistical correlations. The annual and monthly return of salmon as 1‐sea‐winter fish (grilse) in June to September was negatively correlated with water temperature, a nil catch being associated with a maximum value of 24.2° C, coupled with lower values maintained over substantial lengths of the estuary (e.g. 21.5° C over a distance of no more than 50 km). The annual return was negatively related to the extent to which the estuary was predicted to be lethal from the combination of low concentration of dissolved oxygen (DO) and high temperature, a reduction in DO of 1 mg 1 1 being equivalent to an increase in temperature of 4° C. The annual return for the whole year was directly related to the return in July to September. Depending upon the year, the monthly returns were related to both DO and temperature; they were reduced to a tenth at a 95 percentile DO of 2.7 mg 1 1 , whilst the weekly catches were reduced to zero at 2.4 mg 1 −1 . Weekly catches increased with river flow and daily catches increased with both river flow and tidal height. The few mortalities observed in the estuary in July are generally related to the quality of the water as predicted from the combination of high temperature and low DO.