Applied of acoustics to the assessment of the pacific hake population in port susan, Washington, 1969-1973

Acoustic surveys of the spawning population of Pacific hake (Merluccius productus) in Port Susan, Washington have been conducted annually since 1969. Analog echo voltage and voltage-squared integrators were used in conjunction with 38-kHz echo sounders for the 1969 and 1970 surveys. In 1971 a digital echo integration system was developed and applied to the surveys in conjunction with a 105-kHz echo sounder. Surveys were expanded in 1972 to the areas adjacent to Port Susan to evaluate the importance of the spawning behavior and timing in the assessment of the stock size. Surveys in 1972 and 1973 used the digital system in conjunction with both 38-kHz and 105-kHz echo sounders. The acoustic surveys, supported by data from net catches, indicate considerable variation in the hake population during the five years.