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Tracking the Secret Lives of Salmon

ID tags surgically implanted in salmon may help scientists and resources managers solve critical questions concerning salmon conservation

Puget Sound marine scientists may be one step closer to solving the mystery of where salmon swim after they leave their natal freshwater systems, migrate to the ocean and eventually return to their home rivers to spawn. In an ambitious project that involves over 20 agencies collaborating on a Puget Sound Biotelemetry Project, researchers are working to track the migratory patterns of salmon, trout and other marine fishes of Puget Sound.

Using sound transmitters and underwater receivers, the project partners are attempting to trace the marine movements of several species of fish in Puget Sound, including four listed or at risk – Chinook salmon, bull trout, steelhead (proposed for listing), and Sacramento Green Sturgeon. What these researchers uncover may not only help to fill important gaps regarding salmon and other fish movements and habitat use, but could also help resource mangers to better manage and protect salmon and their habitats.

Until now, the migratory lives of salmon in the Puget Sound and ocean have largely remained a mystery. As a result scientists have relied upon assumptions to help predict everything from acceptable harvest levels to where salmon live in nearshore environments. With the information gathered from the Biotelemetry Project this may soon begin to change.

By implanting electronic tags, each of which has its own unique number, in the abdomen of salmon smolts and using receivers to detect and record signals, local researchers are tracking salmon and collecting data as salmon migrate through their various habitats from river, to estuary, to Puget Sound and ultimately to the Pacific Ocean.

For researchers on the Project the implications are far reaching, “Biotelemetry is opening an exciting new world of estuary and marine research of salmonids and marine fishes. It’s work that’s leading to a whole new understanding of what habitats fish reside in or use of as they move through waters in our area and in the Pacific Ocean,” says Fred Goetz, US Army Corps of Engineers scientist. 

According to Goetz, initial results from various biotelemetry studies in Puget Sound are promising in that researchers are reporting good success in tagging salmon smolts with very few observed mortalities and that retrieving data from the submerged sensors is proving feasible. But this sort of submarine sleuthing isn’t easy says Goetz.

First there’s the surgical procedure. Implanting tags requires performing surgery on each fish, anesthetizing them, placing a battery powered implant in their belly — the battery powered tags last from 4 months (smolt-sized tag) to years (shark-sized) — and then successfully releasing them back to their natural environment. Next it’s critical to be able to retrieve the acoustic receivers, or data loggers that have been submerged along the sea floor recording signals from tagged fish as they swim by. “It can be a real challenge to successfully collect receivers,” says Goetz.

“In our steelhead studies, we’ve downloaded initial information from our receivers in rivers and estuaries, but receivers in marine waters are proving more difficult to reach.”  The receivers are located on the bottom of Puget Sound, they can be found at depths from 50 ft to 900 and they must be physically hauled to the surface to be able to retrieve the fish data.  

Despite the challenges, Goetz and others working on the Puget Sound Biotelemetry Project are continuing to make steady headway studying fish that range in size from Chinook, coho salmon, and steelhead smolts (approximately 6 inches or 150 mm) to as large as green sturgeon and six-gill sharks (nine-ft).

At Lake Washington and the Ballard Locks, the City of Seattle, Corps of Engineers and US Fish Wildlife Service (USFWS) are currently collecting and analyzing information gathered in 2005-2006 on the migration and habitat use of juvenile Chinook salmon.  As part of this study the USFWS is assessing how juvenile Chinook use urban shoreline areas in Lake Union, how many survive to the Locks, and how many juveniles may be eaten by predatory fish.  This work will help define what actions the City and the Corps can take to improve habitat at specific locations in the Ship Canal, improve fish passage at the Locks, and determine if there are options for reducing predation.       

At several locations throughout Puget Sound, NOAA, Seattle City Light, Corps and the University of Washington began a multi-year study of Chinook salmon smolts and resident Chinook in Puget Sound to determine how many smolts survive to reach the ocean. Do some decide to stay in Puget Sound and become a resident Chinook, if they stay in Puget Sound where do they reside and what habitats do they use?

Chinook salmon smolts were tagged in Skagit Bay in 2005 and 2006 and resident post-smolt Chinook salmon were tagged in Port Madison in 2005 and in Central Puget Sound and the Whidbey Basin in 2006.   Data is just beginning to be recovered from receivers in Puget Sound, but one early finding showed that several Skagit Bay smolts took a left turn away from the Straits and ocean waters and went south into Puget Sound being heard off of Bainbridge Island.  This behavior might indicate these fish are going to overwinter and may be become resident Chinook rather than migrating to the Pacific Ocean.  

Though biotelemetry technology is still in its infancy, Goetz notices a rapidly increasing interest in using it to answer many of the biological questions currently beleaguering fish experts in Puget Sound. Where do salmon swim in the ocean? How do they return to spawn? How many survive their migratory travels? For many scientists, biotelemetry offers an innovative and more accurate way to answer these questions.

Since 2002, the number of fish tagged per year has increased from 50 to 900 per year, the number of receivers from 20 to 220, and the number of species studied from 2 to 13.

“What’s amazing,” says Goetz, “Is that organizations working on this research are doing so voluntarily and in a collaborative fashion — sharing and purchasing equipment, assisting each other in the field, organizing study plans and sharing data.”

There are currently around 20 collaborating agencies involved in the Puget Sound Biotelemetry Project, which includes five tribes, three universities, two sportfishing groups, watershed groups, state, federal and local agencies, and the POST program (Pacific Ocean Shelf Tracking Project).

In addition to salmon, there has been a groundswell of interest in several research areas in the last couple of years, including steelhead, six-gill shark and even the first tagged invertebrate, the Pacific squid.

This winter will be a very busy season for the biologists as they begin analyzing new information on a large number of different species and salmon populations. The biologists will use this information to design the upcoming years’ work with the hopes of providing even better information for fish management agencies and habitat planners in protecting and recovering Puget Sound fish stocks.

With the help of additional funding support, the researchers hope to continue collaborating on work that provides the basis for ongoing nearshore and marine studies in Puget Sound.
As they analyze the results of their findings, a new window of opportunity opens for resource mangers working the conserve salmon stocks. For many, including Goetz, better information means better policy, and that translates into good news for people and for fish.

For more information on the Puget Sound Biotelemetry Project contact Fred Goetz, Contact info:  (206) 764-3515,

-p. chambers, Shared Strategy for Puget Sound


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