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Instrumented Buoys as Autonomous Observatories of Pelagic Ecosystems

See also Investigation of Aggregation Behavior of FAD-Associated Small Yellowfin Tuna and Size Dependant Vertical Stratification

Progress reports (PDF): FY 2009, FY 2008, FY 2007, FY 2006, FY 2005, FY 2004

Project Overview
Associative behavior is a major component of the life of pelagic fishes. Tropical tunas and other fish species are frequently found in association with a variety of floating objects and with topographic features such as seamounts. Increasingly, fishermen exploit these associations to expand their catches and each year, modern industrial tuna fisheries release thousands of floating fish aggregating devices (FADs) throughout the world's oceans. Although structure-associated aggregations are typically comprised of tunas, there are also sharks, rays, billfish, dolphinfish, sea turtles, and other species caught at FADs. These species, together with the high numbers of sub-adult tunas, are usually not retained but discarded at sea by industrial fisheries. With the increase in catch rates occurring at FADs, including from increased purse seine activity, the standard methods for fishery stock assessment and management have been significantly impacted. Fisheries exploiting these FADs can no longer be managed species by species and the need exists for an ecosystem-based approach to fishery management. These changes require the development of new techniques for stock assessment and fishery management that take into account these structure associated aggregations and their importance to the fishery.

Project researchers believe that appropriate observations and understanding of the aggregation/association phenomenon of fish at FADs will enable fishery researchers in developing fishery-independent indices of local abundance. Earlier fish tracking studies indicate that tunas are usually not located immediately beneath FADs but rather 'orbit' around FADs at varying distances. Hence, researchers propose that an accurate underwater observatory must be able to collect scientific data by "sweeping" the entire circumference of the FAD in order to estimate the size of the aggregation and to eventually distinguish different species and size classes of fish. With the rapid evolution in electronic tag design and capability, project researchers will study the feasibility of developing a tag capable of using acoustic information to determine the 'ecological' circumstance surrounding the tagged fish. Such as whether the fish is participating in collective (schooling) behavior or whether the fish is associated with a floating object. If new sensors on schooling or association can be developed they could be coupled with a recent telemetry innovation - CHAT tags (Communicating History Acoustic Transmitters). These devices remotely transfer archived data from the fish to the listening stations deployed on the seabed or on buoys. Data transfer from the fish to the buoy is achieved by "sonic modem" technology. This would represent a major advance because 'ecological' tags with CHAT capabilities could provide insight into the behavioral and physiological history of many fish species without requiring research ship time.

The main objective of the project is to develop prototypes and methods for creating observatories of pelagic ecosystems. This will be achieved through specific objectives:

1. Development of autonomous 'smart FADs. To be equipped with:
a 360° sonar to observe the collective components of aggregations
• a listening station to observe the individual components of the aggregations
• an appropriate power system for an autonomous operation of these instruments
data storage capacities
• uplinks to download stored data to land-based stations

Eventually, the observatories will also accommodate other oceanographic sensors such as doppler current meters, temperature sensors, as well as down-looking sonar systems designed to observe scattering layer organisms (corresponding to some components of the diet of large pelagic fishes).

2. Identification of specifications for ecological sensors and transmitters
This would help determine the types of marine acoustic signatures that could be used to design an 'ecology tag' that would indicate whether a fish was in a school of conspecifics or in the vicinity of a floating object. CHAT versions of this tag could eventually be used in conjunction with the smart FADs.

3. Co-occurence of large pelagic species at FADs
To use coded transmitters to document the individual behavior of non-tuna species in networks of FADs. Fish carrying the individually coded tags will be detected by data collectors ("listening stations") mounted on FADs in the Hawaiian waters. This will constitute the first network of instrumented buoys for studying residence times, patterns of visitation to the FADs, spatial dynamics, and species interactions.

Research Activities
The research activities of the project are distributed into four main tasks:

1. Organization of an international workshop on the concepts of pelagic observatories
Scientists studying small pelagic fish and those working on large pelagic fishes do not use the same tools and methods to observe their animals. A main objective of this workshop is to gather specialists from each of these groups, as well as scientists and engineers involved in acoustic and electronic tags, to exchange ideas and develop tools to advance the concept of observatories of pelagic ecosystems. This workshop was convened in October 2002, see project page "Workshop on How to Improve Studies on the Collective Behavior of Pelagic Fish".

2. Development, testing and validation of the hardware and software components required to produce an autonomous 360° sonar
Design and development of sonar hardware and software will be headed by Dr. Jules Jaffe of Scripps Institution of Oceanography. Dr. Jaffe is a marine biophysicist specializing in underwater bioacoustics research. He will oversee the selection of hardware sonar components including the transducer, power supply, 360° 'sweep' mechanism, and buoy design.

Split-beam ship-borne acoustic surveys will be conducted to document school distributions around FADs and to calibrate synchronous data recorded by the side-scan system being evaluated for the FAD-based prototype. Prior to incorporation of the side-scan system into a buoy with 360° capabilities, the side-scan system will be deployed from a vessel moored adjacent to a FAD. Side-scan surveys of associated tuna schools will be conducted simultaneously with the use of a SIMRAD sonar system deployed on a separate vessel. In this way validation and interpretive software can be developed prior to the incorporation of the sonar into an autonomous platform. Synchronous experimental fishing at the FAD will also be conducted to cross-validate the split-beam and FAD sonar data. Data storage and transmission capabilities will be addressed by Wildlife Computers, Inc. of Seattle, Washington.

3. Development of criteria for designing 'ecology tags'. Acquisition of specifications for the development of new electronic tags with 'ecological' sensors
For development of new 'ecological' sensors, identifying the types of sounds produced by schools and floating objects is necessary. This task will consist of identifying underwater sounds produced by schools of tuna and FADs and will be under the direction of Mr. Miguel Pol (New Caledonia) who is an expert in the collection and analysis of underwater sounds. Precise recordings of groups of tunas and a single fish swimming in a tank will be recorded to allow design of a hydrophone and filtering system that will exclude sounds produced by fish carrying the tag but that will be sensitive to sounds generated by a large school. School signatures will be obtained from the field by recording sounds produced by tuna schools associated with coastal FADs. Estimates of sizes and composition of the schools will be made using appropriate sonar systems. Similarly, recording of sounds produced by FADs will be done to identify the characteristics that should be detected by the future integrated hydrophone.

4. Electronic tagging of non-tuna species associated with Hawaiian FADs
Throughout the duration of the project an intensive study of the dynamics of pelagic species in networks of FADs will be conducted. More than a dozen of the Hawaii FADs have been equipped with listening stations and tropical tunas are currently being equipped with ID electronic tags. Project researchers plan to install listening stations at other FADs around O'ahu Island and the neighbor islands as well as tagging other species such as sharks, marlins and mahimahi. This large network of listening stations will expedite optimal future deployment of the smart FADs and will also provide very useful novel data on species interactions, e.g., timing of associations.

Year 1 funding for this 2-year project to be available mid 2003.


Principal Investigators:
Dr. Kim Holland
Hawaii Institute of Marine Biology (HIMB)
University of Hawaii at Manoa
Coconut Island
P.O. Box 1346
Kaneohe, Hawaii 96744 USA
Phone (808) 236-7410/533-4110
FAX (808) 236-7443
email: kholland@hawaii.edu
Dr. Laurent Dagorn
BP 5045
34032 Montpellier Cedex 1
Phone 33-0-4-67-41-94-00
FAX 33-0-4-67-41-94-30
email: dagorn@mpl.ird.fr
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This page updated March 24, 2010