Seaward migration of hatchery-reared Atlantic salmon (Salmo salar) smolts in the Penobscot River estuary, Maine: open-water movements
During May and June, 1975 and 1976, nine hatchery-reared Atlantic salmon ( Salmo salar ) smolts were followed by means of ultrasonic telemetry in the open waters of a bay on their seaward migration. Tracks averaged 25·3 km and 13 h 41 min. Smolts in the bay moved rapidly seaward on ebb tides. In the...
| Published in: | ICES Journal of Marine Science |
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| Main Authors: | , , |
| Format: | Text |
| Language: | English |
| Published: |
Oxford University Press
1978
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| Subjects: | |
| Online Access: | http://icesjms.oxfordjournals.org/cgi/content/short/38/2/257 https://doi.org/10.1093/icesjms/38.2.257 |
| Summary: | During May and June, 1975 and 1976, nine hatchery-reared Atlantic salmon ( Salmo salar ) smolts were followed by means of ultrasonic telemetry in the open waters of a bay on their seaward migration. Tracks averaged 25·3 km and 13 h 41 min. Smolts in the bay moved rapidly seaward on ebb tides. In the upper part of the study area some reversed movement occurred on flood tides, but in the lower part seaward movement occurred on both ebb and flood tides. Migrating smolts were usually in the upper few metres of water and away from shore. Ground speeds of smolts averaged 51 cm s−1 (2 body lengths s−1), and were about twice as high on ebb tides as on flood tides. Vector analysis of fish movement direction showed significant clustering around the water current direction, and water current drift drogues at 2 m and 5 m closely approximated the routes of smolts. Evidence from current drift drogues suggests that water currents are the major transport factor in seaward migration of smolts, but is inconclusive on the question of whether smolts actively swim in addition to seaward transport due to water currents. Routes and rates of travel were apparently not affected by diel changes or environmental factors other than water current. |
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