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P.L. Colin
devices are not designed specifi cally for the rather limited “fi sh spawning market”.
In the last two decades the advent of GPS positioning and digital video and still
cameras has resulted in a major increase in information that can be gathered from
aggregations. While new technological methods are appealing, great care needs to
be exercised in deciding whether such methods are feasible in view of their generally greater costs and sometimes limited scope of measurement.
In diving technology increased ease and reduced costs of using mixed gas
rebreathers, which produce no noise and few bubbles hold promise for less disturbance of aggregated fi sh while making observations. Given that many aggregations
are located in shelf edge areas at depths of 25–40 m, the ability to control oxygen
levels in breathing gas, either through use of enhanced oxygen mixtures (nitrox) or
rebreathers, will increase limited bottom times for researchers.
The resolution and low light capabilities of digital still photography and videography allow new documentation of aggregations. The use of stationary autonomous
monitoring stations equipped with cameras will allow new insights into fi sh behaviour. Stations which pan and tilt while taking photos could regularly cover the
entire visible area around the station. Cameras could also be developed which
sense motion, either through optical means or sonar, and photograph whatever is
passing by. Deploying a series of these along migration pathways would provide
remarkable information. Such could even be triggered by passage of an acoustically tagged fi sh, so that any other individuals accompanying it would also be
documented.
Current meters and other electronic instruments will become less expensive and
consequently sites can be instrumented with more sensors to allow fi ner resolution
of physical factors. It would be amazing to have a large transient aggregation instrumented with an array of current meters to detect the movement of water throughout
the site, rather than relying on a single meter at sites now.
The use of an AUV (autonomous underwater vehicle) to document an aggregation area at Glover’s Reef (Shcherbina et al. 2008 ) opens a new avenue of investigation. Such vehicles are rapidly evolving and it would be instructive to deploy
custom-designed AUVs at aggregation sites for documentation of sites in the
absence of divers. Such a vehicle could have a hydroacoustic sonar system oriented
horizontally to the vehicle which scans 180° ahead of the vehicle while simultaneously taking video or still images of the area as well as monitoring physical parameters in the water. Such a vehicle could be silent and slow-moving to avoid disturbing
fi shes. It could even have artifi cial intelligence to remain with an aggregation,
detected by its sonar, and monitor it over a period of hours. Drawbacks to using
AUVs for aggregation monitoring are the typical short durations of data gathering
on dynamic water column properties and lack of complimentary measurements during and after deployments. AUVs should generally be used as part of a large programme with long-term monitoring objectives and capabilities.
Remote sensing is unlikely to become a signifi cant method for discovery of
aggregation sites given the limits of habitat visibility where most shelf edge aggregations occur. Satellite observations hold great promise for increased information
on currents in the vicinity of aggregation sites and oceanic regions. High frequency
P.L. Colin
devices are not designed specifi cally for the rather limited “fi sh spawning market”.
In the last two decades the advent of GPS positioning and digital video and still
cameras has resulted in a major increase in information that can be gathered from
aggregations. While new technological methods are appealing, great care needs to
be exercised in deciding whether such methods are feasible in view of their generally greater costs and sometimes limited scope of measurement.
In diving technology increased ease and reduced costs of using mixed gas
rebreathers, which produce no noise and few bubbles hold promise for less disturbance of aggregated fi sh while making observations. Given that many aggregations
are located in shelf edge areas at depths of 25–40 m, the ability to control oxygen
levels in breathing gas, either through use of enhanced oxygen mixtures (nitrox) or
rebreathers, will increase limited bottom times for researchers.
The resolution and low light capabilities of digital still photography and videography allow new documentation of aggregations. The use of stationary autonomous
monitoring stations equipped with cameras will allow new insights into fi sh behaviour. Stations which pan and tilt while taking photos could regularly cover the
entire visible area around the station. Cameras could also be developed which
sense motion, either through optical means or sonar, and photograph whatever is
passing by. Deploying a series of these along migration pathways would provide
remarkable information. Such could even be triggered by passage of an acoustically tagged fi sh, so that any other individuals accompanying it would also be
documented.
Current meters and other electronic instruments will become less expensive and
consequently sites can be instrumented with more sensors to allow fi ner resolution
of physical factors. It would be amazing to have a large transient aggregation instrumented with an array of current meters to detect the movement of water throughout
the site, rather than relying on a single meter at sites now.
The use of an AUV (autonomous underwater vehicle) to document an aggregation area at Glover’s Reef (Shcherbina et al. 2008 ) opens a new avenue of investigation. Such vehicles are rapidly evolving and it would be instructive to deploy
custom-designed AUVs at aggregation sites for documentation of sites in the
absence of divers. Such a vehicle could have a hydroacoustic sonar system oriented
horizontally to the vehicle which scans 180° ahead of the vehicle while simultaneously taking video or still images of the area as well as monitoring physical parameters in the water. Such a vehicle could be silent and slow-moving to avoid disturbing
fi shes. It could even have artifi cial intelligence to remain with an aggregation,
detected by its sonar, and monitor it over a period of hours. Drawbacks to using
AUVs for aggregation monitoring are the typical short durations of data gathering
on dynamic water column properties and lack of complimentary measurements during and after deployments. AUVs should generally be used as part of a large programme with long-term monitoring objectives and capabilities.
Remote sensing is unlikely to become a signifi cant method for discovery of
aggregation sites given the limits of habitat visibility where most shelf edge aggregations occur. Satellite observations hold great promise for increased information
on currents in the vicinity of aggregation sites and oceanic regions. High frequency