Atlantic Fisheries Research Document 1996/096

Preliminary report of an acoustic survey of inner Placentia Bay, November, 1995

By G.A. Rose

Abstract

An acoustic survey was conducted in Placentia Bay (NAFO 3Ps) with cod as the principal target species in early November 1995. The survey was conducted with two frequency (38 and 120 kHz) Biosonics digital echosounders from the 10 m vessel Innovation (Marine Institute of Memorial University of Newfoundland). The two survey blocks utilized spanned most of the inner part of the Bay. A sub-block, random transect design was used. Analysis employed the new FSIS software developed at Memorial University and CCORE for digital data processing. These techniques enabled bottom and fish resolution much superior to that possible with older and analogue acoustic equipment. Raw densities were converted to absolute using a scaling factor of -32 dB/fish based on previous work. Within sub-block variance was estimated by repeated transect methods, but has not been completed for this preliminary report. Fishing using automatic jigs was conducted at 32 sites. Cod were concentrated over much of the study area at depths of 15-100 m. Densities varied considerably (orders of magnitude). In the west block, densities ranged up to 2 fish/m² and biomass was estimated at 8,500 t. In the east block, densities ranged up to 4.7 fish/m² and biomass was estimated at 16,000 t. Fish sampled ranged from 37 to 82 cm and 3 to 10 years of age. Most adults were in the early stages of maturation

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