| Autor: |
Zedel, Len, Knutsen, Tor, Patro, Ranjan |
| Předmět: |
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| Zdroj: |
ICES Journal of Marine Science / Journal du Conseil; Aug2003, Vol. 60 Issue 4, p846, 14p |
| Abstrakt: |
Observations were made of over-wintering (December 1997) and migrating (January 1998) Norwegian, spring-spawning herring (Clupea harengus) using a moored 307 kHz acoustic Doppler current profiler (ADCP). The location of herring in ADCP data is identified by regions of volume-backscatter strength greater than −60 dB re 1 m−1. The presence of herring was verified using net trawls and 38 kHz, EK500 data. While the ADCP cannot make speed measurements of individual fish, the system does provide a measure of the swimming speed and direction of large herring schools. Herring were observed to move both horizontally and vertically: horizontal speeds were from 0 to 50 cm s−1. Higher speeds were observed during daylight hours for both deployments with somewhat increased activity at both dawn and dusk. At night-time, over-wintering herring demonstrated no well-defined velocity. [Copyright &y& Elsevier] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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