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"Some people talk to animals. Not many listen though. That's the problem."

-A.A. Milne

Fish and Invertebrate Acoustic Projects

Ambient sounds and intra- and inter-species communication are integral to fish and invertebrate survival. For many, sound plays a key role in navigation, finding food, finding mates, and avoiding predators. The NEFSC passive acoustic research program focuses primarily on the sounds produced by fish and invertebrates in the western North Atlantic Ocean. We are interested in how key soniferous (sound producing) species fit into the broader biological soundscape across different habitats, as well as how they are affected by human- made noise. Our aim is to improve the understanding of fish and invertebrate ecology and help inform conservation and management decisions.

Our various projects, as described in the links below, focus on: identifying spawning grounds and their season duration; acoustic diversity and ecology; evaluating if and how anthropogenic sound sources alter fish and invertebrate communication and behavior.

How do fish produce sound, how do they hear, and why do they do it?

Fish can produce sound in a number of ways. The most common method is by rapid contractions of sonic muscles that are amplified in the swimbladder. Another way is by stridulating - the act of rubbing together hard body parts, such as teeth and bones, to produce sound (e.g., catfishes). Body movements that create water currents or splashes are also used to create sounds. Some clupeids even release bubbles from the anal duct to produce very high-pitched sounds.

Over 50 families of teleost fishes are soniferous (produce sound), and at least 150 of these species are found on the east coast of the U.S. These sounds are usually described onomatopoeically, such as drums, knocks, pops, purrs, growls, etc. Examples of prominent sound producing fish families include: Sciaenidae (croakers), Batrachoididae (toadfishes), Triglidae (sea robins), Haemulidae (grunts), Holocentridae (squirrelfishes) and Pomacentridae (damselfishes).

In order to utilize bioacoustic signals, fish must be able to detect sound. There are two principal components to the sound field - particle motion and pressure. The basal mechanism of detecting sound in fishes is based upon the former. This involves displacement of hair cells in the inner ear by movements of the dense otolith relative to the rest of the fish, which then excites the auditory nerves in the brainstem. The pressure component of the sound field is usually detected via the compression and rarefactions of a gas-filled body (e.g., swimbladder), which is then transduced to the inner ear and displaces the hair cells in the same manner as mentioned previously. However, other parts of a fish can also contribute to sound detection, and "hearing" in fishes often involves a multi-sensory response, which can also include the lateral line. In general, fishes hear in the lower frequency ranges (<500Hz), with some species possessing morphological specializations (e.g., Weberian ossicles in goldfish) creating the ability to hear at slightly higher and/or lower sound levels. Furthermore, there is some evidence that some species can even hear ultrasonic sounds (e.g., shad up to 180 kHz). Ultimately, there is a spectrum of hearing abilities from those that only hear the particle motion component, to those that are also very adept at detecting the sound pressure component.

Producing and detecting sound in fishes is widespread and of great importance. Sound is vital in locating mates, avoiding predators and danger, scaring competitors and predators, and maintaining social cohesion. Some also create sound as a distress call. We are only beginning to understand the full reasons behind the diversity of bioacoustics in fishes.

For more information, see this list of relevant literature on fish acoustics.

How can passive acoustic monitoring (PAM) help?

Passive Acoustic Monitoring (PAM) in the aquatic environment refers to the use of underwater microphones (e.g., hydrophones) to detect and monitor biotic and abiotic sounds in the ocean. PAM can serve as a useful, non-extractive, and cost-effective monitoring tool that complements traditional survey methodologies (e.g., aerial, visual, trawl, telemetry etc.). Recording units, such as marine autonomous recording units (MARUs) and SoundTraps, can be deployed for months at a time, and can gather data in conditions that would otherwise limit survey effort. The data gathered from these recorders provides scientists with information on the acoustic presence of a species of interest with known species-specific signals. Arrays of recorders can allow data to be gathered that track the spatial presence of a species and possibly fine-scale movements.
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