800 species of fishes worldwide are known to be vocal, though this is
likely to be a great underestimate. Of these, over 150 are found in the
northwest Atlantic. Amongst these families are some of the most abundant
and commercial fish species, including the herring, cod and haddock. Passive
acoustics offers a unique tool to study these fishes, which often live
in dark and turbid waters and are difficult to observe by other means.
Passive acoustic techniques can be used to locate concentrations of particular
species, especially during their vulnerable spawning stage. This in turn
allows spawning habitat to be identified, mapped, and protected. It can
allow the numbers of fish to be assessed. And it can be used to gain a
better understanding of fish behaviour, including fish migrations. Passive
acoustics can also be used to simultaneously monitor sources of noise
pollution, and to study the impact of mans activities on marine
communities. Anthropogenic sources include noise generated by boating
activity, seismic surveys, sonars, fish-finders, depth finders, drilling
for oil and gas, and military activities. These all have an unknown but
potential important impact on marine fauna.
are difficult to see and study in the ocean. SCUBA techniques can help
in shallow waters and a range of active acoustic and optical techniques
can assist in deep water, but we are still largely ignorant of the distribution
and behaviour of the great majority of marine fish. Possibly one of the
greatest challenges to researchers attempting to study the behavioural
ecology of fishes is that of finding the fish in the first place. Often
a scientist must go to great lengths conducting expensive and time consuming
biological surveys simply to determine the locations or habitats where
a fish can be found, before any attempt to study its biotic and abiotic
interactions can be made. After all, you can't study something you can't
find. Any tool that can help scientists to locate fish is therefore valuable.
Fish too face the problem of assessing their environment, navigating through
it, and communicating with others of their kind. A surprisingly large
number use sound to overcome the problem of living in a visually opaque
Sounds travel much farther
in water than light and underwater sounds, including fish calls, can often be
heard over much greater distances than fish can be seen. Listening to fish can
contribute a great deal to our knowledge of their abundance, distribution and
behaviour. Already significant strides have been taken:
- in the northern Adriatic,
workers at the WWFs Miramare Nature Reserve have searched for spawning
concentrations of the corvina Sciaena umbra. Passive listening from
a sailing boat has revealed that large number of this threatened species are
associated with harbours and marinas (many of them newly constructed) along
the coasts of Italy, Slovenia and Croatia. (Bonacito, Costantini, Picciulin,
Ferrero & Hawkins, 2001).
- in an Arctic fjord in
northern Norway, workers from the FRS Marine Laboratory, Aberdeen and the
University of Tromsø have located a spawning ground of haddock, Melanogrammus
aeglefinus. Passive listening has revealed that this species thought
to spawn offshore in deep water can form large spawning concentrations
close to shore. (Hawkins, Casaretto & Picciulin, 2001).
- a number of studies
in the estuaries of the eastern United States have helped to localise the
spawning areas of drum fishes. (Saucier and Baltz 1993; Connaughton, Fine
& Taylor, 2001; Luczkovich & Sprague, 2001).
- for the first time in
the United States passive acoustics are being explored as a tool to census
marine fishes on the continental shelf. A two-year study to catalogue soniferous
fishes in the Stellwagen Bank National Marine Sanctuary was begun in October
2001 (Rountree, http://www.fishecology.org). One goal of the study is to determine
the feasibility of using passive acoustics as a supplemental tool in the census
of fish diversity and habitat use patterns in the sanctuary.
- an ongoing survey of
soniferous fishes of Cape Cod, Massachusetts has resulted in a significant
range extension for the cryptic estuarine and inshore fish the striped cusk-eel,
Ophidion marginatum. Extensive sampling over many decades with conventional
gears in the region had failed to recognise the importance of striped cusk-eel
to the fauna, while passive acoustics revealed it to be widespread and abundant.
This study demonstrates that even a low budget, low tech, approach to passive
acoustics can contribute significantly to the census of marine life.
These studies, using
relatively simple techniques, have confirmed that passive listening can
locate concentrations of important fish species, opening the way for further,
more detailed studies of their behaviour, distribution and habitat use.
developments for further research to take place are:
- the preparation
of descriptive catalogues of the sounds produced by the fish faunas
of given areas, taking account of seasonal changes, to be based on both
field and aquarium studies. A start has been made in the eastern North
Atlantic by Rodney Rountree of the School for Marine Science and Technology,
UMASS Dartmouth, together with the establishment of a National Archive
of Fish Sounds at Cornell University.
- the development
of sound recognition systems, based on wavelet analysis and other new
techniques to enable the automatic discrimination of different species.
For a north Atlantic species, the haddock, it has already proved possible
to distinguish the voices of individual male fish. (Wood, Casaretto,
Horgan & Hawkins, 2001)
- automatic event
detection/analysis software to quantify temporal patterns of sounds
over long time periods
- software allowing
simultaneous analysis of video and audio data in behaviour studies (i.e.,
click on the sound wave of a fish call and view the corresponding video
frame in a second window). This capability would allow rapid correlations
of individual sounds and sound components with behaviour and functional
- the improvement
of passive listening technology for systematically detecting and recording
sounds at sea, including:
- ship based listening
systems, with dangling and towed hydrophones
- bottom mounted
listening systems based on underwater vehicles and pop-up buoys.
- drifting sonobuoy
systems, either storing the data, or telemetering data to ships or shore-based
- large hydrophone
arrays, capable of localising sound sources.
- measurement of
source levels, and calibration techniques for measuring the distance
of sound sources.
- back-yard science:
Perhaps of equal importance to passive acoustics systems for use in
the open ocean is the development of technology to aid in small scale,
low budget studies of marine fishes in estuarine and inshore habitats,
- archival acoustic
recorders - unmanned recorders for use on ships of opportunity in many
types of habitats
- homing devices
to locate sound sources (research underway)
- devices that allow
simultaneous recording of both audio and video data
- hand-held devices
for shore based, or small boat surveys in shallow water
- miniature ROV
designed for both video and audio recording of fish behaviour from small
boats and from shore
- application of
these techniques in a range of habitats, where fish may aggregate to
spawn, for example:
- mangrove areas,
which are especially difficult to survey by conventional means, but
where the diversity of fishes may be especially high.
- coral reefs and
rocky reefs, where again many species aggregate.
- oceanic and inshore
banks, where the mass spawning of sound producing species, like cod
and haddock, takes place.
- the deep sea,
where many species like the morids and macrourids are suspected to be
vocal from anatomical evidence.
- estuaries - the
primary spawning grounds for many economically important fishes
- development of
local, regional, national and international networks of "listening posts"
especially in estuarine and inshore waters. Incorporation of listening
posts into local and regional environmental data networks like GoMOOS
and the NOAA/OCRM/NERR's System Wide Monitoring Program
- a better foundation
for the management of exploited species by mapping their distribution
and pinpointing their spawning grounds.
- a better understanding
of the habitat preferences of key fish species (e.g., Essential Fish
Habitat "EFH" assessment in the US), giving a better focus for their
of baselines for the abundance and distribution of key fish species,
allowing examination of the effects of future environmental change.
- obtaining a wider
knowledge of the behaviour of those fish that cannot readily be studied
by any other method.
non-destructive census of marine life
- works at night
without bias (versus video and other techniques that require lights)
- can provide continuous
monitoring of fishes
- determine the
daily and seasonal activity patterns of fishes including determination
of discrete daily spawning times
- provides remote
- can be used to
monitor environmental noise and determine their sources
- can be used to
examine the impact of anthropogenic noise on fish, especially on spawning
- networks of listening
posts can provide synoptic data on the occurrence of fishes and spawning
activities on local, regional, national and global scales
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