Effects of vessel noise on fish density estimates from hydroacoustic surveying

Session: Poster session

Justin Trumpickas, ON Ministry of Natural Resources & Forestry, [email protected]
Erin Dunlop, ON Ministry of Natural Resources, Trent University, [email protected]

Abstract

Hydroacoustics is an effective means of estimating fish density, particularly for pelagic species rarely targeted by traditional assessment netting methods.  On the Great Lakes, hydroacoustic surveys are typically conducted on relatively large vessels (>15 m) using downward-looking transducers.  The use of large vessels can potentially lead to underestimates of fish density, if vessel noise causes fish to swim away from the ensonified area under the vessel.  Furthermore, pelagic trawling conducted simultaneously with hydroacoustics, for the purposes of ground-truthing, can be an additional source of noise.  Smaller vessels with less engine noise and not conducting trawling may cause less fish avoidance. To test this hypothesis, parallel hydroacoustic surveys were conducted on Parry Sound, Lake Huron during July 2017using a large (18.3 m) and a small (7 m) vessel.  Both vessels surveyed the same transects using downward-looking Simrad EK-60 120 khz transducers with identical data collection settings.  The large vessel conducted pelagic trawling while hydroacoustic surveying, whereas the small vessel did not.  The results showed whether fish avoidance differed between the vessels, and whether this caused biased fish density estimates.

1. Keyword
acoustics

2. Keyword
fish populations

3. Keyword
Lake Huron