APPENDIX D
Archival Tag Technology

A novel type of tagging technology provides a new and promising avenue for obtaining data on the movements of bluefin tuna in the Atlantic Ocean. Until recently, two types of tagging technologies have provided a limited picture of the movements and behavior of individual bluefin tuna in the Atlantic Ocean. Data obtained from conventional tag and release programs are vital for discerning the rate of movement and the extent of mixing in the Atlantic Ocean. Acoustic or sonic tags have provided information on daily behavior, depth and temperature preference, and body temperature. Acoustic tags provide data at a time resolution of seconds for periods of up to five days. The acquisition of such data is technically challenging and requires extensive ship time. Recently, a new type of tag called an archival tag has been developed by separate engineering efforts in four nations. The tag offers a powerful tool for discerning the movements, geoposition, and behavior of individual highly migratory fishes. The tags will get wide use in the coming five years in fisheries that have a proven tag and recapture program (the archival tag must be retrieved to obtain data).

Archival tags are miniature data loggers that have been specifically designed for use on fishes, sea turtles, and marine mammals. The tags are currently being used on tunas, plaice, salmon, whale sharks, sea turtles, and seals to study behavior, movement, and physiology. The archival tag records and stores environmental and behavioral data. In fish, the tags are designed to be returned like conventional tags, via the commercial and sportfishery. A series of sensors provides information on temperature, depth, and irradiance. The recording of irradiance can establish the time of sunrise and sunset in each day as well as the day length that is currently being used for geopositioning. Software provides



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OCR for page 135
An Assessment of Atlantic Bluefin Tuna APPENDIX D Archival Tag Technology A novel type of tagging technology provides a new and promising avenue for obtaining data on the movements of bluefin tuna in the Atlantic Ocean. Until recently, two types of tagging technologies have provided a limited picture of the movements and behavior of individual bluefin tuna in the Atlantic Ocean. Data obtained from conventional tag and release programs are vital for discerning the rate of movement and the extent of mixing in the Atlantic Ocean. Acoustic or sonic tags have provided information on daily behavior, depth and temperature preference, and body temperature. Acoustic tags provide data at a time resolution of seconds for periods of up to five days. The acquisition of such data is technically challenging and requires extensive ship time. Recently, a new type of tag called an archival tag has been developed by separate engineering efforts in four nations. The tag offers a powerful tool for discerning the movements, geoposition, and behavior of individual highly migratory fishes. The tags will get wide use in the coming five years in fisheries that have a proven tag and recapture program (the archival tag must be retrieved to obtain data). Archival tags are miniature data loggers that have been specifically designed for use on fishes, sea turtles, and marine mammals. The tags are currently being used on tunas, plaice, salmon, whale sharks, sea turtles, and seals to study behavior, movement, and physiology. The archival tag records and stores environmental and behavioral data. In fish, the tags are designed to be returned like conventional tags, via the commercial and sportfishery. A series of sensors provides information on temperature, depth, and irradiance. The recording of irradiance can establish the time of sunrise and sunset in each day as well as the day length that is currently being used for geopositioning. Software provides

OCR for page 135
An Assessment of Atlantic Bluefin Tuna graphical representation of all data. Tags currently on the market weigh 25 g in air, have up to one megabyte of memory, can retain data for 20 years, and have a lifetime of four to five years. The tags cost approximately $1,000 each. Development teams are concentrating on reducing the size of the package, increasing the memory, and reducing the cost. An additional area of experimentation is in the attachment methodologies. The requirement for long-term attachment necessitates development of attachment methods that can hold the package in place for years. Methods for mounting the tags will vary widely, depending on the species being examined. Archival tags typically contain a data logger board with a microcontroller, a mass data store with up to one megabyte of memory, and an analog sensor board. The tags vary between development teams but range from having one to seven sensors. This flexibility is designed to allow the user to be able to tailor the tag to the different requirements for studies on a given species. Tags are coated in an epoxy resin to keep the weight of the unit as low as possible. Programming and data retrieval are done with PC-based software. Communication is via a serial RS232 infrared optical link in both the English and Australian tags (the most advanced available). The Australians have recently put archival tags on bluefin tuna. Use of the tag followed an extensive conventional and acoustic tagging effort that provided data suggesting that archival tagging would be successful. From 1990 to 1993, over 27,000 southern bluefin tuna were tagged with conventional techniques. To date, over 900 have been returned via Australian and Japanese fisheries. Acoustic tagging efforts have provided approximately 16 days of depth and temperature preference data from 11 individual bluefin tuna. The success of handling the fish in both programs with positive results (returns and survival upon acoustic tag and release) led to a recent experiment with archival tagging on one-and two-year-old bluefin tuna. Archival tags have been placed in numerous bluefin tuna over the past year. The tags are inserted invasively with the light sensor trailing outside the fish. To date, three tags have been returned with several months of data. Implementation of this program with successful attachment and recovery bodes well for the use of this technology on the northern bluefin tuna in the Atlantic Ocean. The conventional tag and release program in the Atlantic Ocean provides encouraging numbers which indicate that archival tagging would be successful in the Atlantic Ocean. The recovery of just a few tags would exponentially increase our knowledge of where these fish go, and a major effort in this area should be encouraged. Problems that need to be solved before archival tags are put on bluefin tuna in the Atlantic Ocean are the following: In what geographic location would we see the highest recovery of tags? This is vital to making sure the experiment works (i.e., survival with the tag is ongoing). Where and how should a tag be attached to a fish that has enormous

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An Assessment of Atlantic Bluefin Tuna growth potential, i.e., externally or internally? On what year class should emphasis be placed? How well will the geopositioning-light sensor technology that is irradiance based work in areas close to the equator? Efforts should be concentrated at latitudes where the technology is proven. Develop programs for recovery of tags once placed on fish. Awareness of the value of the tag and its importance to scientists will require a large education effort. Design a program that will yield maximum results.

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An Assessment of Atlantic Bluefin Tuna This page in the original is blank.