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<blockquote type=cite class=cite cite=""><font size=4><b>SCIENCE NEWS,
Delta Stewardship Council, Delta Science Program </b></font><br>
J U N E 2 0 1 0<br>
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Tracking Fish</a><br>
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Pick Our Brain</a> <br><br>
<br>
<h3><b>Tracking Fish is More Than Just a Game of Tag</b></h3><br><br>
<b><a href="#table">Coded Wire Tags vs. Acoustic vs. Radio vs.
PIT</a><br>
</b><br>
<h5><b>Different types of tags (radio, acoustic, PIT) </b></h5><br>
As the old saying goes, there’s more than one fish in the sea. But if you
want to know how many fish there are, or where they're going, there’s
more than one way to tag a fish to track its movement and life history. A
number of different tagging options have been used in the Delta. The
following is a look at different kinds of tags that have been used in the
Delta and elsewhere.
<ul>
<li><b>Coded Wire Tag (CWT)</b>
<li>Fish raised in a hatchery have their adipose fin (a small second fin
on the back of a fish directly in front of the tail fin) clipped to
differentiate them from fish raised in the wild. In addition to the fin
being clipped, a CWTa microscopic piece of magnetic wire with a tiny
code engraved on itis injected into the nose of the fish when they’re
young. These tags, which have been used in the Delta for about 20 years,
can track the history of the fish. When they’re caught as adults, the
tags reveal where and when the fish were born. Although these ‘mark and
recapture’ studies can provide a start and end point to a fish’s movement
over a defined period, they can’t provide information on the path taken
by the fish between the two points.
<li>Another drawback with CWTs is that “you have to kill the fish to
remove the tag,” said Chris Holbrook, a biologist with U.S. Geological
Survey (USGS). “You have to physically capture them, which requires an
incredible amount of effort and is usually extremely costly. You have to
drag nets and actually encounter the fish, which is sort of why CWT has
fallen by the wayside in recent years. Due to the low recapture rate in
the Delta, most fish tagged with CWTs are never caught after release,” he
said. Holbrook added that the CWT does last forever. “You could catch
[the fish] any timeeven as a carcass” and extract birth information
from the CWT.
<li><b>Passive Integrated Transponder (PIT) Tag</b>
<li>This tag has no battery, but provides a unique code, like a CWT, yet
can be read without killing the fish. A PIT tag is nearly identical to
the microchips used to identify pets and works the same way. A PIT tag is
a tiny microchip assembly sealed in glass, which is injected into the
body cavity of a fish. If a tagged fish passes within a meter or so of a
scanning device, the scanner reads the unique identification number from
the chip in the PIT tag. As with microchips for pets, a hand held scanner
can also be used in the field to identify fish. Thus PIT tags have many
of the advantages of CWTs (small, relatively cheap and lasts the life of
the fish). “It is more expensive than a CWT, but less expensive and
longer lasting than battery powered tags,” said Dr. John Pizzimenti, a
member of the Vernalis Adaptive Management Plan (VAMP) independent review
panel and a scientist from GEI Consultants in Oregon. “In order to read
the tag, the fish must be recaptured (like CWT) but does not need to be
sacrificed as it can be read using equipment that supplies the
electromagnetic power to make the tag send its unique signal to a special
receiver. Fish passing dams and fish facilities can be read
automatically.”
<li>“PIT tags have become the primary source of salmon recovery data on
the Columbia River where fish return to known locations or must pass
confined spaces in fish passage facilities at dams,” Pizzimenti added.
“Incidentally, PIT tags are being recaptured on Caspian Tern islands
where they are regurgitated by birds after consumption of tagged smolts.
This is leading to estimates of smolt predation by birds there.”
<li><b>Acoustic Tag</b>
<li>Acoustic tags are surgically implanted, battery-operated tags that
send a coded pinging sound signal. Researchers can identify individual
fish by the signal code when they pass near underwater microphone
receivers at various locations. “Acoustic tags provide a better location
accuracy and can even provide 3-D positioning by using triangulating
signals from multiple microphones. This can be useful when designing fish
passage systems and studying fish approach and passage behavior to a
small entrance in a large river,” said Pizzimenti.
<li>Acoustic tags have a battery and emit a signal that can generally be
heard at great distanceshundreds of meters away. “The reason we’ve seen
a lot of acoustic tagging recently is when you tag a fish and release it,
you can be a large distance away from the fish and record its presence,”
said Holbrook from USGS. “We put out sensors throughout the riverlike
listening postswhere you can generally hear across the entire river.
Most of the time if a migratory fish with an acoustic tag swims past your
listening post/receiver, then it will get recorded. None of those other
technologies can do that,” he said. “You can put a post at one place in
the river and essentially know all the fish that pass that site.”
Acoustic tags clearly tell scientists how many fish get through the Delta
and the paths they take.
<li>Acoustic tag microphones are usually submerged at fixed locations.
The California Fish Tracking Consortium
(<a href="http://californiafishtracking.ucdavis.edu/" eudora="autourl">
</a><a href="http://californiafishtracking.ucdavis.edu/" eudora="autourl">
http://californiafishtracking.ucdavis.edu/</a>) has set up arrays of
acoustic receivers extending all the way to Point Reyes to detect
Sacramento River salmon on their way to the ocean. They can also be
carried in a boat, but the boat must stop, set up the microphone, then
record. Potential drawbacks of acoustic tags are that they require many
microphones, are more expensive, and acoustic tag life is limited to the
size of battery, which is limited by the size of fish. “The smallest fish
that can generally be tagged is about three inches and can carry a
battery life of less than a month,” Pizzimenti said. Acoustic tags can’t
be used in smelt; the small size of smelt requires CWT or PIT.
Additionally, noise from boat motors, turbulence and hydroelectric dams
can disrupt or mask acoustic sound signals. <br><br>
<li><b>Radio Tag</b>
<li>This tag consisting of a tiny transmitter and battery pack is
surgically implanted in juvenile fish (or in the gut of an adult fish).
It sends radio waves of a unique signal through the water column to the
air, where they are picked up by a radio antenna. Radio tags can be
tracked using antennae mounted on aircraft, boats, cars and points along
shorelines, at dams and fish passage facilities, and on foot (hand held).
Unfortunately, that signal doesn’t travel very well in water. “The deeper
a fish swims, the weaker the signal in the air,” Pizzimenti said. This
decreases the accuracy for determining the exact location of the fish due
to ‘depth – distance’ signal confusion as both depth and distance weaken
the signal to varying degrees.
<li>Radio tags also have a trailing fine wire antenna, which may affect a
fish’s swimming ability. Like acoustic tags, radio tag life is limited to
the size of battery which is limited to the size of fish. Radio signals
are further weakened by dissolved salts and therefore are less effective
in briny or salt water.
</ul><h3><b>Other Options</b></h3><br><br>
Other sophisticated ways to tag or identify fish include the use of
genetic markers (known DNA type); physical markers including freeze
branding, ocular tags (tiny numbered tag that fits into the eye socket);
and otoliths (the ear bone in juvenile fish that can be read like tree
rings after a fish is killed). Finally, fish are still tagged using
externally placed physical tags in the fish that can be seen. “These
carry limited information and can be lost (as most tags can be lost or
altered) to make them unreadable,” Pizzimenti said. Each tag type has a
cost, benefit and type of application that differs from the
others.<br><br>
“There is no one type of tag that fits all needs for the type of data
being collected,” Pizzimenti said. “In the Bay Delta, CWT have value, but
acoustic and radio tags have been put to greater use in recent years and
tell biologists much more about the behavior and survival of salmon
smolts as they move from the Delta to the ocean.” <br><br>
It’s impossible to pick one form of tagging over another as “the best,”
Holbrook said. “It depends on the studythe question you’re trying to
address. You’ll see studies using multiple telemetry systems sometimes;
one may answer one question very well; but to answer a suite of questions
in the same study, you sometimes need to use a couple different methods,”
he said. One thing is certain though, advances in fish tagging and
tracking technology have greatly expanded our knowledge of the life
cycles of fish. <br>
<b><a name="table"></a>Tag Type</b> <b>Pros</b> <b>Cons</b>
<a name="table"></a><b>Image<br>
Coded Wire Tag</b>
<ul>
<li>Small
<li>Inexpensive
<li>High survival from tagging
<li>Proven technology; long history
<li>Fish must be caught and killed to read tag
<li>Only two data points possible: point of release and point of
recapture
<li>Recapture rate small in Bay Delta
<li>Requires large sample sizes
</ul>
<img src="http://www.science.calwater.ca.gov/publications/images/scinews_0610_tags_wt.jpg" alt="source image courtesy of Marine Institute, Galway">
<br>
<b>Passive Integrated Transponder</b>
<ul>
<li>Small
<li>Inexpensive
<li>No battery; lasts forever
<li>Don’t have to kill fish to read tag
<li>Detection rate low - Very small detection range of about a meter
</ul>
<img src="http://www.science.calwater.ca.gov/publications/images/scinews_0610_tags_pit.jpg" alt="Image courtesy of Michael Melnychuk, University of Washington">
<br>
<b>Acoustic Tags</b>
<ul>
<li>Can use far fewer fish (less than 1,000)
<li>Provide better location accuracy
<li>Can be recorded from large distances away
<li>Cost
<li>Limited battery lifespan
<li>Equipment issues: tags can fail, microphones can fail
<li>Noise interference (boats, pumps)
<li>Issues with identifying when a smolt’s been eaten by a predator
</ul>
<img src="http://www.science.calwater.ca.gov/publications/images/scinews_0610_tags_at.jpg" alt="Image courtesy of Michael Melnychuk, University of Washington">
<br>
<b>Radio Tags</b>
<ul>
<li>Send out radio signal
<li>Useful for tracking movement
<li>Tracking from a distance
<li>Limited battery lifespan
<li>Wire antenna trailing out from fish
<li>Signal doesn’t travel well in water
<li>Need to follow fish around with boat
<li>If predator swallows fish, antenna gets swallowed
</ul>
<img src="http://www.science.calwater.ca.gov/publications/images/scinews_0610_tags_rt.jpg" alt="Image courtesy of Michael Melnychuk, University of Washington">
</blockquote><br><br>
<blockquote type=cite class=cite cite=""><h3><b>Telemetry Studies Results
Given at UCD Symposium at Bodega Bay</b></h3><br><br>
During a Delta Science Program-funded University of California, Davis
symposium May 20-21, participants from the Central Valley and beyond
presented the results of electronic tagging studies of salmon migration.
Highlights included:
<ul>
<li>Results from the California Fish Tracking Consortium receiver network
that can track the movement of tagged salmon and steelhead from Keswick
Dam to Point Reyes
<li>Advances in fish tagging technology including smaller tags and
improved receivers
<li>Effects of tides, river flow, gate operations, and route choice on
salmon survival in the Delta
<li>New discoveries about the movement of salmon, steelhead, sturgeon,
and other fish in rivers and coastal waters
<li>Detailed information about fish use of restored and natural habitats
</blockquote>
</ul><br>
Continued advances in fish tagging technology, including smaller and
longer lasting tags, are providing new opportunities for understanding
the behavior and fate of fish. The new smaller acoustic tag sizes are
allowing researchers to tag smaller fish such as juvenile salmon and
track their movements over long distances. Tagging technology also allows
researchers to identify individual fish throughout their life span. More
than one scientist described the travels of their favorite individual
fish over long distances and several years. It is now common for
researchers to track tagged fish from other studies and share data about
their movements. <br><br>
<blockquote type=cite class=cite cite=""><h3><b>Vernalis Adaptive
Management Plan Final Report Released</b></h3><br><br>
The independent review panel of the Vernalis Adaptive Management Plan
(VAMP) recently submitted its final report. VAMP is a large-scale,
decade-long experimental management program that was designed to protect
juvenile Chinook salmon emigrating from the San Joaquin River through the
Sacramento-San Joaquin Delta while providing scientific information for
the State Water Resources Control Board’s review and potential
modification of the San Joaquin River flow objectives included in the
Water Quality Control Plan (Bay-Delta Plan).<br><br>
During a two-day meeting in March, the panel was charged to provide an
independent review of the science generated by the VAMP and make
recommendations for how this science should be used to inform changes to
the Bay-Delta Plan. Key panel conclusions are:
<ol>
<li>There is evidence that higher flows increase survival of juvenile
Chinook salmon passing through the Delta from the San Joaquin River, but
the situation is complicated by other factors and survival is generally
very poor.
<li>Evidence for improved survival with reduced exports is weak because
of the very narrow range of export flows that occurred during the study.
<li>Placing a rock weir or operable gate at the Head of Old River to keep
salmon out of the Old River channel and in the San Joaquin River channel
improves survival.
<li>The VAMP participants should continue to use acoustic tagging
technology, but should also use coded wire tags or other tagging
technology to track fish throughout their life cycle.</blockquote>
</ol>Given the rapid changes in tagging technologies and recent evidence
of extremely low salmon survival rates, the panel recommended that the
VAMP program continue to collect acoustic tagging data supplemented by
other tagging methods and that the findings be reviewed on a more regular
basisevery three years. The panel was also struck by the high rates of
predation observed in recent years and urged researchers to improve
understanding of predation effects by more broadly characterizing
predator distribution, abundance and feeding habits.<br>
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