Ha-Shilth-Sa
March 11, 2004
In an article in the Canadian Journal of Fisheries and Aquatic Sciences (1984), it was shown that noise has a profound effect on the swimming and spawning patterns of Pacific Herring, particularly if those noises come from boats and fishing gear.
"There is a significant amount of scientific literature on sensitivity of fish to sounds and the effects of those sounds on their behavior," said Central Region Biologist Josie Osborne. "Herring have never been reported to be attracted to any natural or artificial noises, but have responded negatively to some," she said.
According to Osborne, there has been some scientific interest in the effect of seine and gillnet boats on the very fish that they are trying to catch. DFO scientists Abby Schwarz and Galen Greer looked at the responses of Pacific herring to a variety of noises, including boat motors, fishing gear, and natural noises such as rain, gull cries, sea lion barking, and killer whales. They found that herring gave no response to many sounds, but they gave negative responses to many others. The first type of negative response was avoidance; if they were feeding heavily they stopped and sank about 1 metre below the surface, packed up, polarized and slowly moved away from the noise. The second type was alarm; they packed, polarized, and fled away and downward from the noise regardless of their previous behavior. The third type of response was startle; a single powerful flexion of the body followed by a 5 to 10 second period of faster swimming, without changing their original heading. School formation was not affected by the startle response.
Avoidance was the most usual response to playback sounds of motors and fishing gear. Bigger motors had lower frequency sounds and were heard from farther away than small motors. The response was always directional - away from the source.
"Sounds made by large vessels approaching at constant speed were avoided by most groups," said Schwarz and Greer in their 1984 study. "Avoidance ended within 10 seconds after the vessel began departing and its noise began diminishing in intensity, but although the fish returned to the vicinity of the sound source they did not approach the surface again for 1 - 3 minutes more."
The study concluded
the larger the vessel, the greater the distance from which it can elicit
a response from herring. Sounds made by approaching vessels were more
effective in eliciting a response than steady sounds or departing vessels.
Because vessels obviously approach then depart a specific place, the fish
would increasingly react as a boat gets nearer (amplitude of the noise
increases) and "relax" as the vessel departs. The larger the
vessel, the lower frequency noise it emits (the deep throb of an inboard
diesel engine vs. the whiny high pitch of an outboard) - lower frequency
noises elicited stronger responses. Seiners appear to be a major source
of aversive stimuli in the fishing fleet for herring.
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