|NEW VOL 20
|PAS - GDANSK DIVISION
pp. 15-20, vol. 2, 1999
Sea Fisheries Institute, Gdynia, Poland
Abstract: Acoustic methods could play an important role in monitoring vertical and horizontal fish distribution; including fish stock assessment, however the fish as acoustic target is not precisely specified still. The paper describes a new type of approach to express diel variability of acoustic parameter sv, characterizing fish volume density. Multi-depth-channel integration of fish echoes was applied to estimate the average diel models of sv dependence on time of a day. The final characteristics was calculated by computer as a vectoral field, showing quasi-continuous diel transformation of depth distribution of sv values. Example based on data collected during October 1996 RV "Baltica" research cruise was given and discussed. Strong variability of sv values with time and depth was exposed and clearly different diel phases of fish behaviour were separated. Results indicate a necessity of further research on fish target strength within separate periods of a diel cycle, to define more accurately biomass conversion factors. The method shown could enreach significantly systematic physiological studies on fish behaviour also.
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© Polish Acoustical Society - Gdansk Department, Polish Academy of Sciences. This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported. (CC BY-NC-SA 3.0)