|
|
|
A Review of Salmon and Steelhead Supplementation
June 4, 2003 | document ISAB 2003-3
Read the report in 3 parts:
Related links:
Overview
The report was completed in response to NOAA Fisheries and Northwest
Power Planning Council requests for the ISAB to consider the benefits and
risks of supplementation to natural populations of salmon and steelhead,
and whether natural and artificial production could be integrated to
increase the capacity and productivity of the combined population for the
foreseeable future.
The ISAB reviewed the genetic risks, and models of the demographic
benefits, of supplementation, performance indicators to evaluate
supplementation, decision-making tools for supplementation risk-benefit
assessment, and surveyed the status of Columbia River Basin
supplementation projects.
The ISAB's primary conclusions are:
- While supplementation is ongoing, it can often be expected to
increase the number of salmon and steelhead spawning naturally in the
target population, and this may provide additional harvest
opportunities, compared to the situation with no artificial
production.
- The increased population size and productivity attributable to
supplementation will likely not persist once supplementation ceases.
- Supplementation can reduce the natural spawning fitness component in
the integrated population and this reduction in natural spawning
fitness will persist in the natural spawning population for some
number of generations after the termination of supplementation.
- Data to calculate the correct performance indicators are not being
collected regularly in supplementation projects. Because of the
widespread lack of reference populations, neither benefits to
abundance, nor risks to natural spawning fitness, can be effectively
quantified at present.
- Except for critical cases where a natural spawning population is
literally on the verge of extinction with no credible options for
rescue by habitat improvements or harvest management, a technically
valid risk-benefit assessment of supplementation to decide upon
whether supplementation should be undertaken in any particular stream
will be dominated by uncertainty because the data needed for the
assessments are largely unavailable.
The ISAB recommends:
- Use supplementation sparingly, and only implement in a subset of the
locations where unharvested natural populations are not replacing
themselves, where habitat capacity is believed to be able to
accommodate additional production, and where landscape conditions and
institutional considerations are suited to maintaining the integrity
of the experimental design.
- Where supplementation is used, it should follow a protocol that uses
natural-origin adults from the target population as parents in
hatchery spawning.
- Establish and monitor performance standards for each project for
natural-origin and hatchery-origin adult abundance and per capita
production rates.
- Conduct all supplementation projects with explicit experimental
designs to reduce uncertainty and contain supplementation risks.
Establish reference populations, adequate monitoring, and objective
means to assess when supplementation should be terminated (due to
either success or failure).
- Coordinate the multiple supplementation projects across the Columbia
River Basin so that in aggregate they constitute a basinwide adaptive
management experiment. The Fish and Wildlife Program should include
mechanisms to ensure that individual projects are collecting the data
necessary to test their effectiveness and ensure regional coordination
of the multiple experiments.
Implementing these more rigorous experimental protocols should improve
the scientific understanding of whether supplementation can contribute to
salmon and steelhead recovery at a tolerable cost to natural spawning
fitness of wild populations.
September 24, 2003 follow-up report (see also in
PDF format)
To: Judi Danielson, Chair, Northwest Power and Conservation Council
Olney Patt, Jr., Executive Director, Columbia River Inter-Tribal Fish
Commission
Usha Varanasi, Director, NOAA-Fisheries Northwest Fisheries Science Center
D. Robert Lohn, Regional Administrator, NOAA Fisheries
From: Eric J. Loudenslager, Chair, Independent Scientific Advisory
Board
The ISAB thanks the Northwest Power and Conservation Council for the
opportunity to report on the findings and conclusions of our
supplementation report at the Council's June 2003 meeting in Boise. We
also thank the Northwest Fisheries Science Center and the Columbia River
Inter-Tribal Fish Commission for their review comments.
Supplementation is a complicated topic. There is an ongoing debate
among managers and scientists as to whether this strategy increases the
abundance of natural origin adults and what effect it has on the natural
spawning replacement rates-both quantities are critical to the recovery of
self-sustaining salmon and steelhead populations. For these reasons the
ISAB supplementation report was lengthy and detailed.
Council members had many questions for the ISAB during our
presentation. Based on these questions, the ISAB concluded that a brief
summary of our conclusions and recommendations could assist the Council,
NOAA Fisheries, and CRITFC in identifying the priority issues in our
report. That summary follows. If Council, NOAA Fisheries, or CRITFC
executives or staff scientists request, the ISAB would be pleased to
provide further elaboration of the summary points.
Hatchery fish are not the same as wild fish. Fish adapt genetically
(evolve) to the conditions of hatchery rearing, a process termed
domestication. They also will evolve new life history strategies as they
adapt to completing their life cycle in the wild after their release from
the hatchery. When compared against wild stocks, production hatchery
stocks usually have lower adult-to-adult reproductive success when
breeding in the wild. Because many of the traits associated with
domestication are determined genetically, allowing domesticated salmon to
interbreed with wild salmon will reduce the fitness of the integrated
(mixed hatchery/wild) population spawning in the wild.
The degree of domestication for any given population depends on the
number of generations that the population has spent in hatchery breeding
and the strength of domestication selection. In a hatchery population
maintained by deliberately isolated (closed) breeding, the level of
domestication is generally high. For this reason it is to be expected that
a supplementation program that simply allows large numbers of individuals
from a closed hatchery line to interbreed with a self-sustaining wild
stock of the same species will have considerable negative effects on the
natural spawning productivity and viability of that wild stock. This
conclusion formed the basis for the ISAB recommendations in the hatchery
surplus report (ISAB 2001-3).
Some supplementation programs propose to maintain their lines by an
integrated breeding protocol that uses some wild-spawned fish for
broodstock in each generation and that limits the numbers of
hatchery-spawned fish that are allowed to breed in the wild in each
generation. Such a protocol results in a pedigree in which some of the
recent ancestry is from hatchery breeding and some is from natural
breeding. These types of protocols will cause less domestication than
long-term exclusive (closed) hatchery breeding, but they do not eliminate
domestication. For that reason these programs still pose a risk to the
viability of wild stocks.
There has not yet been enough experience with supplementation programs
that are based on defined integrated breeding protocols to quantify how
much domestication will occur in such programs or how much damage they
will cause to the natural spawning life cycle performance of wild stocks,
as measured by adult-to-adult replacement rates of the wild spawning fish.
It also is not yet clear how effective such programs will be at increasing
the number of naturally spawning fish of naturally spawned origin, if they
comply with the defined broodstock and outplanting constraints.
It is for these reasons that the ISAB and ISRP have recommended that
supplementation of an existing wild stock should be implemented only on an
experimental basis, in settings where some probability of damage to the
wild stock can be tolerated, and where the progress of the experiment can
be monitored. Effective monitoring is critical to ensure that we will
learn from the experiment how much domestication really occurs, what is
the effectiveness of such a program for increasing recruitment from
natural spawning, and what is the cost to natural spawning fitness. To be
effective for this purpose, monitoring in each such experiment must
measure, over time: 1) the actual rates of drawing naturally spawned and
hatchery spawned fish for broodstock, 2) the actual proportions of
naturally spawned and hatchery spawned fish on the spawning grounds, 3)
the natural spawning replacement rates in the supplemented population and
in an unsupplemented control, and 4) the number of naturally spawning fish
of naturally spawned origin in the supplemented population and an
unsupplemented control. Because of natural variation in salmon
productivity from one year to the next, and imperfect matching of
treatment and control stocks and environments, reliable conclusions will
require results from a number of implementations of this design. At
present the experimental design(s) of the supplementation projects in the
Columbia River Basin, based on the projects reviewed in our report, will
not resolve these uncertainties.
These concerns about scale, experimental design, experimental control,
and monitoring needs have been at the heart of the issues raised by the
ISRP in their reviews of specific supplementation programs. These same
concerns were explained in detail in the ISAB general review of
supplementation.
Public enthusiasm over the record returns of salmon of the last few
years further challenges us as scientists and managers to adequately
communicate why these large current returns of mostly hatchery fish are
not a sufficient measure of success at restoring wild populations. The
critical evidence will be determining whether natural spawning by these
returning adults is more or less productive than unsupplemented wild
stocks, under equivalent conditions. We must bear in mind that even though
present ocean conditions are good, they are expected to continue to cycle.
As a result, it is important to determine not whether hatchery-based
production has supplemented the natural returns in these recent years (it
generally has), but whether these natural spawners (hatchery and wild)
produce increased numbers of adult progeny in future years.
^ top
 |
Use Adobe Reader to
view PDF documents |
|
|
home