The dissolved oxygen and temperature requirements of Atlantic salmon, Salmo salar L., in the Thames Estuary

• Published in: Journal of Fish Biology
• Main Authors: Alabaster, J. S., Gough, P. J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1986
• Subjects: Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.1111/j.1095-8649.1986.tb04977.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1095-8649.1986.tb04977.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1095-8649.1986.tb04977.x

An improvement in water quality in the estuary of the River Thames in recent years, coupled with the return of adult Atlantic salmon following artificial stocking of the headwaters with parr and of the lower river with smolts, has provided an opportunity to define the dissolved oxygen requirements of adult fish ascending the estuary to reach fresh water. Between July and September 1984 the fish traversed a length of 30 km where the concentration of dissolved oxygen was at its lowest, the 5‐percentile and median values being 1.6–2.6 and 3.5–5.9 mg l −1 , respectively, depending upon exact location. Within this zone there was a length of about 20 km in which the minimum at any one time during the period was always less than 5mg l −1 and a shorter length of 15 km in which it was always less than 4.7 mg l −1 , and it is likely that some fish experienced even lower values during their upstream passage. Over lengths of 1, 10 and 30 km, for example, the 10‐percentiles were 2, 2.2 and 2.8 mg l −1 , respectively, the medians were 3.6, 3.8 and 4.3 mg l −1 , respectively and the 90‐percentiles were 4.8, 4.9 and 5.3 mg l − , respectively. The water temperature during August, when most of the fish were caught, was never lower than 19°C and there was a length of estuary of at least 20 km where it exceeded 22°C.