raphy-bathythermograph-type data including depth of the surface mixed layer. Light levels are used for 'light-based geolocation' which is a way of estimating an animal's position, because radio signals do not penetrate sea water. The data is seldom in real time-even the Argos data is delayed by a few hours prior to being relayed to the user," says Holland. For fish that do not break the surface, GPS and Argos fixes are not feasible. However, for air breathers, such as turtles, whales and seals, there are now 'fast GPS tags' that collect and send GPS derived locations." Holland says future capabilities of these sensors will "add conductivity and chlorophyll sensors to tags but these are not yet ready for prime time. For fish that occasionally come to the surface and air breathers there are simple radio beacons that rely on the Argos satellites to figure out the location of the animal carrying the transmitter. The tricky part is that these transmitters transmit with very low power, between 1/2 and 1.0 watts. That's a very tiny signal for a satellite to detect." Au says the Dtag sensor has been employed with sperm whales, beaked whales Blainville's Beaked Whales, Cuvier's Beaked Whale, killer whales, humpback whales, and the list continues to grow. B-Probes have
been attached to elephant seals, blue, fin and humpback whales. Of course the tricky part is getting the device onto the animal. "Most animals are restrained after being caught on hook-andline or for mammals, in nets," Holland says. Surgical techniques are used to attach and/or implant transmitters. For some large marine mammals such as whales, tags are attached using air guns, cross bows or poles. Seals, walruses, and other such mammals are usually captured on their haul-out beaches and the tags are glued to their fur." In addition to these tags, there is a whole other line of tagging that places acoustic transmitters in fish, including marlin, tuna, tiger sharks, great white sharks, and others. These tags allow pursuit vessels to follow the fish or for moored receivers to detect the fish as they swim by. "This is the technology underpinning the Ocean Tracking Network (OTN) that is just getting launched and of which University of Hawaii is a part," says Holland. Some of the data received has been surprising. "Almost all tagged animals -- seabirds, marine mammals and fish -- go much deeper than previously expected and can tolerate lower oxygen levels and ambient temperatures than would have been predicted," according to Holland.
HiOOS
The Hawaii Ocean Observing System (HiOOS) is a part of the larger Pacific Islands Ocean Observing System (PacIOOS), a regional integrated system designed to collect and disseminate timely, reliable, oceanographic information and products to a broad range of agency, private, and community stakeholders. Says Chris Ostrander Regional Coordinator of HiOOS at the University of Hawaii, the intent of their tracking and tagging efforts, such as those of Holland and Au, is to provide data to support forecasts of environmental fluctuation, habitat degradation, human pressures, and long-term climate change on living marine resources. "A better understanding of the ecosystem in its current state and the factors that may influence its stability in the future will allow resource managers to better preserve populations for generations to come," Ostrander says.
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Marine Technology Reporter 19
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