Publication Abstract

Orientation and swimming speed of plaice migrating by selective tidal stream transport. Preliminary results from acoustic tracking and ADCP measurements

Orientation and swimming speed of migrating plaice from acoustic tracking and ADCP measurements

A. Buckley and G. Arnold

We tracked 25 large female plaice in the southern North Sea and eastern English Channel during the winters of1994to 1999, using 300 kHz transponding acoustic tags and sector scanning sonar. We determined the position of the research vessel by GPS and measured the speed and direction of the tidal stream using an Acoustic Doppler Current Profiler (ADCP). We are in the process of estimating the swimming speed and direction of the fish by vector subtraction, using data from 53 midwater excursions taken from the tracks of 10 fish that exhibited selective tidal stream transport. We present here the data for one representative track, which agree with theoretical predictions that migrating plaice should head downtide in midwater and swim at a speed close to their optimum. Mean headings for the selected fish were mostly within ± 3 5° of the mean direction of the tidal stream, all were within t 60° and the average down-tide swimming speed was approximately 0.6 fish lengths s1. We discuss our results in relation to the reconstruction of the geographical tracks of fish from pressure records obtained from data storage (archival) tags and the sensory mechanisms involved in the migration of demersal fish in tidal seas. We also compare them with the results of an earlier analysis based on whole-tide ground tracks and average tidal stream vectors derived from navigation charts.

Reference:

A. Buckley* and G. Arnold* (2001) Orientation and swimming speed of plaice migrating by selective tidal stream transport. Preliminary results from acoustic tracking and ADCP measurements. pp263-277 In: (Sibert, J.R. and Nielsen, J.L. (eds)). Electronic tagging and tracking in marine fisheries.

A. Buckley* and G. Arnold*

pp263-277 In: (Sibert, J.R. and Nielsen, J.L. (eds)). Electronic tagging and tracking in marine fisheries