| Autor: |
Ledgerwood, Richard D., Ryan, Brad A., Dawley, Earl M., Nunnallee, Edward P., Ferguson, John W. |
| Předmět: |
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| Zdroj: |
North American Journal of Fisheries Management; May2004, Vol. 24 Issue 2, p440-451, 12p, 2 Diagrams, 6 Charts, 2 Graphs, 1 Map |
| Abstrakt: |
We developed a surface pair-trawl system to detect juvenile Pacific salmon Oncorhynchus spp. marked with passive integrated transponder (PIT) tags as they migrate through the upper Columbia River estuary. The trawl was fitted with a detection antenna in its cod end and was deployed by two vessels. Fish entering the trawl body exit after passing by the detection antenna. Detection data were recorded by electronic components housed in a small boat tethered to the trawl. The system was modified extensively after its first deployment in 1995 and by 2001 was performing reliably under a variety of weather conditions and river flows. From 1995 to 2001 the device detected 29,699 PIT-tagged juvenile salmon. During extended daily sampling periods, we detected nearly 2% of all PIT tags previously detected at Bonneville Dam, which is located 159 rkm upstream from the study area. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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