THE BEHAVIOR OF YOUNG SALMON (SALMO SALAR L.) IN THE RIVER LIZHMA (LAKE ONEGO) IN THE SUMMER SEASON
| Autor: | Denis Efremov, Aleksey Veselov, Mikhail Ruch’ev |
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| Jazyk: | English<br />Russian |
| Rok vydání: | 2019 |
| Předmět: | |
| Zdroj: | Transactions of the Karelian Research Centre of the Russian Academy of Sciences, Iss 11 (2019) |
| Druh dokumentu: | article |
| ISSN: | 1997-3217 2312-4504 |
| DOI: | 10.17076/eco1070 |
| Popis: | 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 activityduring 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 lessthan 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” micrositescompared to 0+ and 1+ individuals. |
| Databáze: | Directory of Open Access Journals |
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