THE BEHAVIOR OF YOUNG SALMON (SALMO SALAR L.) IN THE RIVER LIZHMA (LAKE ONEGO) IN THE SUMMER SEASON

• Published in: Proceedings of the Karelian Research Centre of the Russian Academy of Sciences
• Main Authors: Denis Efremov, Aleksey Veselov, Mikhail Ruch’ev
• Format: Article in Journal/Newspaper
• Language: English; Russian
• Published: Karelian Research Centre of the Russian Academy of Sciences 2019
• Subjects: atlantic salmon; parr; sites; microsites; foraging behavior; territorial behavior; foraging intensity; Science; Q; Atlantic salmon; Salmo salar
• Online Access: https://doi.org/10.17076/eco1070; https://doaj.org/article/8333c6f4d57042648e6908927b4bd7d8

It was found that each age group of young salmon has its own daily foraging activity pattern, mainly regulated by illumination. At the latitude of the Lizhma River (62°22ʹ40ʺ N, 34°29ʹ57ʺ E), which drains to Lake Onego, the foraging activity duration in June and July is 16 h ± 30 min. In twilight hours and in the dark (below 200 lx) it was absent in all age groups. Young-of-the-year (0+) maintained a constant level of foraging activity during the day, making about 900 darts at food. Parr aged 1+ and 2+ foraged the most actively in the morning (18,000 lx), after which the activity declined until 15 h (70,000 lx)and remained low until 19 h (21,000 lx). Then it increased slightly until dusk. The number of darts at food was about 350 per day. For 3+ parr, the activity was the lowest in the morning hours, gradually growing afterwards to reach a peak at around 15 hours, after which a gradual decline was observed. During the day they make about 300 darts at food. The foraging intensity for 0+ fish averages 63 darts per hour. Fish aged 1+ make less than 30 darts/h; 2+ make about 40 darts/h; 3+ salmon make about 25 darts/h. Foraging activity can be reduced by dense clouds and competition. Young fish aged 0+ and 1+ cannot compete with larger parr and other predators for fodder-rich sites. 2+ and 3+ parr occupy the most advantageous feeding microsites, where they perform up to 88 % of all daily darts for food in less than 50 % active time, and thus satisfy their daily nutritive demand. As a result, 2+ and 3+ parr would be more often seen inactive in “shelter” microsites compared to 0+ and 1+ individuals.