A program to develop and promote the application of new electronic tagging technology to study usage of marine environments and migration routes of Pacific Salmon.

George Jackson

Project Leaders:

Dr. George Jackson, University of Tasmania/Vancouver Aquarium, Vancouver, British Columbia

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Visit the POST web site

The Pacific Ocean Shelf Tracking (POST) program, one of seven initial field projects of the Census of Marine Life (CoML), is a major program designed to develop and promote the application of new electronic tagging technology to study the marine life history of Pacific salmon. One of the two major areas of focus in the POST project involves the development of a permanent continental-scale marine telemetry system. POTENT (Pacific Ocean Tracking and Evaluation NeTwork) will sit on the seabed of the continental shelf and slope and be used to monitor fish movements along the shelf and into the open ocean. POTENT array data can then be applied toward the development of fishery management policies aimed at the sustainable harvest of Pacific salmon resources, and the technology can be applied to other species of marine fish as well.

METHODS AND TECHNOLOGY

Acoustic tags implanted in Pacific salmon will allow the movements of individual fish to be tracked for the duration of their residence on the continental shelf, and thus, in principle, for the entire life history of shelf-resident salmon stocks. Juvenile salmon caught in rivers can be implanted with archival or acoustic tags. Archival tags are passive devices which measure and store information on temperature, depth, or light levels, allowing a reconstruction of the movements of the tagged salmon; however, the fish must be caught again to retrieve this information. In contrast, acoustic tags transmit the serial number of a tagged animal. The signal is detected and recorded by a receiver on the seabed when a tagged fish passes within range. Acoustic receivers would be placed across the continental shelf in a series of lines so that the detection ranges for the receivers overlap, ensuring high probability of detection and eliminating the need to recapture the fish. From the information obtained from the array, the direction, speed, and timing of movements of individual animals can be reconstructed; it should also be possible to determine the regions of the coast and the times of the year when survival is good or bad.

SCIENTIFIC OBJECTIVES

While much is known about the freshwater life history phases of Pacific salmon, very little is known about their marine life history. Using the POTENT array, researchers expect to address previously unresolved questions such as:

• Do different salmon stocks form stock-specific aggregations at sea, or do they share common migration pathways and foraging areas? If such aggregations or pathways occur, where are the boundaries and how long do salmon remain in these areas?
• Do distributions and migration patterns fluctuate with annual and long-term changes in ocean productivity, such as spring bloom cycles and El Niño/La Niña conditions?
• How do different salmon species respond to changes in ocean conditions?
• What are the winter movements and habitat usage of juvenile salmon?
• What differences exist between the movement patterns and habitat use of wild and hatchery salmon?
• Do shelf migration behaviors correlate with changes in annual stock success?
• How do distribution and habitat use differ among species and stocks?
• Is there stock-specific, life-stage specific, or location-specific mortality in the ocean?
• Is it possible to follow an individual salmon's marine movements over a complete life history cycle?

Many fundamental questions about the ocean life of Pacific salmon remain unknown. Because the ultimate goal is the wise, sustainable use of Pacific salmon resources, there is a need to fill these information gaps. Developing a better understanding of the ocean biology of Pacific salmon will not only help salmon managers in determining which actions will enhance ocean survival, but may also eventually aid governments in developing policies to increase survival in the marine habitat.

2002 CoML TRIAL

In 2002, a total of 35km of acoustic listening lines were deployed off the east and west coasts of northern Vancouver Island in two large-scale experiments. These complementary two-month studies were designed to allow scientists to track 120 tagged steelhead smolts from two populations with very different marine survivals as they migrated into the ocean. Initial estimates from the West Coast (Quatsino Sound) study demonstrate that successful tracking of the movements of 100% of the tagged animals entering the ocean is possible, and showed that apparently all the young steelhead survived after entering the ocean-the opposite of long-standing scientific belief. An additional study conducted on marine survival of coho smolts in 2003 found the same high survival.

The findings from our pilot studies have been very positive for the POST project and the CoML, indicating that a future continental-scale acoustic tracking array should be successful in providing extensive data on the habitat use and marine survival of Pacific salmon. Long-term collection of this type of information has never before been possible in the marine environment; the building of a permanent continental-scale tracking array expands the horizons of studying the biology of many marine animals in new ways.

THE FUTURE

The existence of a tracking array will assist in resolving a number of important management questions. Managers need to know where their stocks move, how long they stay in different areas, and how ocean conditions affect growth and mortality. The eventual expansion of pilot studies into a full acoustic array, eventually combined with archival tagging studies, will allow scientists and managers to monitor salmon movements and habitat usage along coastal North America, from California to the Aleutian Islands, year-round. Once these tagging methods are proven to work on salmon, they can be applied to a virtually unlimited range of marine species. At its full potential, the system can track up to 256,000 different animals at the same time.

Visit the Pacific Ocean Shelf Tracking Project web site