Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Hatchery fish outnumber wild chinook salmon in troubled fall run

07.04.2008
Hatchery controversy takes on new significance as salmon populations crash

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.

Tim Stephens | EurekAlert!
Further information:
http://www.ucsc.edu

More articles from Studies and Analyses:

nachricht New study: How does Europe become a leading player for software and IT services?
03.04.2017 | Fraunhofer-Institut für System- und Innovationsforschung (ISI)

nachricht Reusable carbon nanotubes could be the water filter of the future, says RIT study
30.03.2017 | Rochester Institute of Technology

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Bare bones: Making bones transparent

27.04.2017 | Life Sciences

Study offers new theoretical approach to describing non-equilibrium phase transitions

27.04.2017 | Physics and Astronomy

From volcano's slope, NASA instrument looks sky high and to the future

27.04.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>