Inter‐stage survival of wild juvenile Atlantic salmon, Salmo salar L.

• Published in: Fisheries Management and Ecology
• Main Authors: CUNJAK, R. A., THERRIEN, J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1998
• Subjects: Canada; Midwinter; Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.1046/j.1365-2400.1998.00094.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1046%2Fj.1365-2400.1998.00094.x; https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2400.1998.00094.x

A biological model was developed to calculate annual survival between life stages of juvenile Atlantic salmon, Salmo salar L., in Catamaran Brook, a small stream basin (52 km 2 ) in the Miramichi River catchment in New Brunswick, Canada. Seven years’ data (1990–1996) were used in the model. Input variables included: daily fish counts and measurements of parr (3–4 age classes), smolts, and adult salmon at a fish‐counting fence near the stream mouth; biennial quantification of all habitat types along the watercourse; fish density estimated by electric fishing at 30 sites; and estimates of young‐of‐the‐year emigration via stream drift. Continuous recording of stream discharge provided data to assist in interpretation of survival estimates. Annual survival for juvenile salmon in their first 3 years of life in the stream averaged between 31% and 34%. The greatest annual variation (CV = 0.699) occurred at the egg to 0+ (summer) stage with a low of 9.2% survival recorded for a winter with an atypical midwinter flood event; parr and pre‐smolt survival were similarly affected. Survival from egg deposition (after correction for losses caused by predation and retention/non‐fertilization) to smolt emigration was between 0.16% and 0.52%, which is low relative to estimates from many other studies. Survival of smolts to returning 1‐sea‐winter adults (grilse) averaged 8.5%. Potential errors in the computation of the model are discussed, e.g. inaccurate counts of spawning adults during high autumn stream flow. A possible explanation for the low egg to smolt survival was the environmental conditions experienced during various winters. Mean egg survival was 1.3 times higher (39.3%) and egg to smolt survival increased to 1.03% when the two winters characterized by extremely low discharge or midwinter freshets were excluded from the calculation. Density‐dependent factors related to a beaver dam, which limited spawning distribution, may also have contributed to poor survival and increased fry emigration in one year. Environmental ...