[env-trinity] Hatchery fish greatly outnumber wild Chinook salmon in troubled fall run

[Tom Stokely]

Contact: Tim Stephens
stephens at ucsc.edu
831-459-2495
University of California - Santa Cruz

Hatchery fish greatly outnumber wild Chinook salmon in troubled fall run

SANTA CRUZ, CA--A recent study indicates that wild salmon may account
for just 10 percent of California's fall-run chinook salmon population,
while the vast majority of the fish come from hatcheries. The findings
are especially troubling in light of the disastrous decline in the
population this year, which will probably force the closure of the 2008
season for commercial and recreational salmon fishing.

The role of hatcheries in the management of salmon populations has been
a contentious issue for many years. The new findings appear to support
the idea that including artificially propagated fish in population
estimates can mask declines in natural populations caused by a lack of
suitable habitat.

"Our finding that 90 percent of the fish are from hatcheries surprised
a lot of people," said Rachel Barnett-Johnson, a fisheries biologist
with the Institute of Marine Sciences at the University of California,
Santa Cruz.

Barnett-Johnson and her coworkers published their results in the
December 2007 issue of the Canadian Journal of Fisheries and Aquatic
Sciences. The main focus of the paper is the development of a new
technique for distinguishing between wild and hatchery-raised salmon.
The researchers validated the technique and used it to estimate the
percentage of wild fish among the fall-run chinook salmon caught by
commercial fishing boats along the central California coast in 2002.

"It's a one-time estimate for that year, and these things do change
over time. But it's the most recent and perhaps best estimate we have,"
said Churchill Grimes, director of the National Marine Fisheries Service
Santa Cruz Laboratory and a coauthor of the paper.

In 2002, the fall run of chinook salmon in the Sacramento River was
estimated at 775,000 adults returning to spawn, according to the Pacific
Fisheries Management Council. Fewer than 60,000 are expected this year,
even with no ocean fishing allowed. If the percentage of wild fish is
the same this year as in 2002, it would mean fewer than 6,000 wild
salmon in what has been the largest salmon run on the West Coast.

The researchers were able to distinguish between wild and
hatchery-raised fish by analyzing the banding patterns in fish ear
bones, called otoliths. Like tree rings, characteristic light and dark
bands in the otoliths reflect daily growth increments, and the width of
the bands indicates growth rates. The differences observed between
otoliths from wild and hatchery-raised fish are the result of
differences in the availability of food at a critical transition in the
salmon life cycle, when the young fish (called fry) have used up the
food supply in their yolk sacs and must start feeding themselves,
Barnett-Johnson said.

"In the wild, they hide in the gravel until they use up the yolk sac,
and then there is a period of slower growth while they learn to feed on
aquatic insects. This abrupt transition and slow growth are captured in
the growth bands of the otolith," Barnett-Johnson said. "In the
hatchery, there is an abundant supply of food, so the transition is
smoother and growth bands are wider."

Every fish, therefore, carries an identifier of its origin as a natural
tag in the earbone, which has significant advantages over techniques for
tagging fish, she said. Coded wire tags (CWTs), for example, have been
used to mark fish for some studies. But only a small fraction of
hatchery fish and even fewer wild fish are tagged or marked in
California, according to Barnett-Johnson. Some small hatchery operations
clip the fins of all hatchery fish so they can be distinguished from
wild fish, but fall-run chinook salmon are not marked that way. As a
result, there have not been good estimates of the proportion of wild
fish in the population until this study, she said.

"The only other estimates out there pointed in the other
direction--significantly more wild fish than hatchery fish,"
Barnett-Johnson said. "One study used CWT recoveries from hatchery fish
and estimated that 33 percent of adults returning to rivers in the
Central Valley were from hatcheries. The other number floating around
comes from counting the number of fish returning to spawn in rivers
versus returning to hatcheries, and this estimated the number of 'wild'
fish to be 3.5 times higher than hatchery returns."

One reason these figures are so important is that they could affect the
listing of the fall run under the Endangered Species Act (ESA). The
question of whether hatcheries can help restore threatened and
endangered salmon populations or if they actually harm wild populations
has long been a controversial issue. It became a legal issue in 2001,
when a federal judge revoked the ESA listing of Oregon coast coho
salmon, ruling that the National Marine Fisheries Service (NMFS) should
have included hatchery fish in the population counts.

A more recent federal court ruling, however, concluded that the health
and viability of natural populations should be used as the benchmark for
ESA status determinations. That ruling has been appealed to the U.S.
Court of Appeals for the Ninth Circuit.

"The agency's policy on counting hatchery fish has flip-flopped as a
result of these different legal decisions," Grimes said. "Now the focus
is again on wild fish, and it doesn't appear there are many of them.
That could be bad news for fishing because, if the fall run is listed
under the Endangered Species Act, there would be no legal harvest."

Fisheries experts blame unfavorable ocean conditions for the dismally
low returns of chinook and coho salmon to rivers and streams all along
the West Coast this year. In 2005, when this year's returning salmon
were juveniles just entering the ocean, food production in the
California Current was much lower than usual due to a delay in the
wind-driven upwelling of nutrient-rich water that sustains the food web
along the coast. A similar disruption of the normal upwelling occurred
the following year (see earlier press release at
http://press.ucsc.edu/text.asp?pid=971).

"We expect the returns to be as bad or worse next year as they were
this year," Grimes said. "The years when those fish outmigrated into the
ocean were the worst conditions that we've seen in over 25 years of
observing spring conditions."

Compounding the situation is the degradation of the freshwater habitat
for salmon in the Sacramento River and the rest of the Central Valley
drainage system, he said. "There is no question that the river basin's
capacity to produce salmon--the quality of the habitat--has been
degraded something awful, and it just doesn't produce like it used to,"
Grimes said. "We have these remnant populations--that's all it is
really. We're trying to manage what's left."

Barnett-Johnson said the otolith technique offers a new tool for
monitoring the effectiveness of restoration efforts and tracking the
numbers of wild fish over time. By estimating the numbers of hatchery
and wild fish independently, the technique can help to differentiate
between effects on the population due to ocean conditions and those due
to freshwater conditions. That's because hatchery-raised fish don't face
the same hazards in the initial freshwater phase of their life cycle
that wild fish do, so they would be affected less by freshwater
conditions. Not only are hatchery fish protected and artificially fed in
the hatcheries, they also get a free ride downstream in tanker trucks.
The hazards associated with migrating downstream to the ocean range from
predators to the pumps that siphon water out of the rivers for human
use.

"Most of the hatcheries in the Central Valley put the fish in tanker
trucks and release them into the lower San Francisco Bay Delta, so they
bypass a lot of the mortality that occurs in the rivers,"
Barnett-Johnson said. "If freshwater mortality was a key factor in
population declines, we would expect to see hatchery and wild
populations responding differently."

Barnett-Johnson plans to use the otolith technique to track changes in
the composition of the salmon population over time. Unfortunately,
because her research depends on a collaboration with commercial
fishermen, the possible closure of the fishery this year may mean that
she will not be able to get any salmon otoliths to analyze.

"At a time when we really need more information on the status of wild
populations, a complete closure would mean I can't conduct my research
to provide this estimate," she said.


###

In addition to Barnett-Johnson and Grimes, the coauthors of the paper
are Chantell Royer of Humboldt State University and Christopher Donohoe
of the NMFS Santa Cruz Laboratory. This research was supported by the UC
Marine Council and the Partnership for Interdisciplinary Studies of
Coastal Oceans (PISCO).




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