ANALYSIS OF SIDE-LOOKING DEPLOYMENT OF HYDROACOUSTIC TRANSDUCERS IN FISHERIES SCIENCE

ABSTRACT Side-looking (SL) deployment,of hydroacoustictransducers isan effective approach to manage,the issue of the near-field effect that limits abundance estimation of fish near the surface (<2 m) when using down-looking (DL) deployment,in acoustic surveys. However, determining appropriate target strength (TS) thresholds for SL is more difficult due to the greater variability of orientation of fish and thus greater variability in the TS compared to DL. In this paper, I derive appropriate TS thresholds for SL acoustics in two alewife (Alosa pseudoharengus) dominated lakes, one in New York and the other in Pennsylvania.I use ex situTS distribution of alewife from a net cage experiment as well as in situTS distribution of alewife from the lakes to determine the