Quite a number of years ago Earth Island sponsored a “Literature Review” paper on marine animal hearing we called “Fish Ears” It was presented at the US Navy-sponsored “Environmental Consequences of Underwater Sound” (ECOUS) conference in San Antonio Texas and published in the Soundscape – Journal of Acoustic Ecology.
The paper was a systematic examination of acoustic-sensory adaptations of marine critters from the most complex hearing of whales and dolphins to the most rudimentary statocysts of jellyfish; the main point of the paper being that most marine animals have some acoustic relationship to their surroundings – so by extension noises introduced into thier habitat will have some impact on the animals.
One of the commercial consequences of the ECOUS “Fish Ears” presentation was Ron Kastelein’s development of a more efficient way of harvesting clams. Sea-bottom dwelling clams are commercially harvested by excavation with high pressure water jets. Because clams are usually open and filtering food from their surroundings this form of harvesting injects sand and mud into their shells and often damages or kills them.
Cockles (clams) being exposed to sound. Photo: Seamarco
Hearing that clams could hear, Ron got the idea of startling them with sound and getting them to close up before excavating them with the jets. This method significantly decreases the damage to and contamination of the clams, facilitating a less wasteful and much cleaner harvest.
The “Fish Ears” paper did surprise many folks by revealing that clams, crabs, squid, and even jellyfish can sense sound, but the connection had yet to be made that these animals could be damaged by too much sound. While there have been a few papers and some anecdotal evidence describing squid and snow crabs being damaged or killed by seismic airgun surveys there was not a lot of repeatable evidence substantiating problems with noise exposure.
But just last month a paper in Nature journal’s “Scientific Reports” describes work done by Caitlin Night and John Swaddle linking significant deformations in marine larvae caused by the noise of seismic airguns. The paper states that “the results were not subtle: high proportions of malformed larvae were found in all four containers exposed to noise while no malformations were found in the four control flasks.”
Earlier this year another paper in Animal Behavior and described in Science Daily examines how shipping noise compromises predator avoidance and feeding behaviors in common shore crabs.
There have been other papers describing noise impacts on marine invertebrates, but for the most part these have been opportunistic studies done on animals in their natural habitat in the presence of various anthropogenic noises. These recent papers were a result of systematic exposure of animals to controlled noises, yielding repeatable results.
As we understand more about animal’s acoustical relationships to their surroundings, and know more about the various sounds to which these animals are being exposed, some of our intuitions are becoming confirmed: Marine animals that hear noise (most of them) can be exposed to excessive noise with negative and even fatal consequences.