Diminishing Returns:

e
v
i
t
u
c
Exe
y
r
a
m
Sum

Salmon Decline andPesticides

A publication of theOregon Pesticide Education Network (OPEN)■ Oregon Environmental Council■ Northwest Coalition for Alternatives to Pesticides■ OSPIRG Foundation■ Institute for Fisheries Resources

We gratefully acknowledge the support of:■ The Pew Charitable Trusts■ The Bullitt Foundation■ Turner Foundation■ The Tides Center■ Rockefeller Family Fund
■ True North Foundation■ The Educational Foundation of America
as well as numerous individuals who have supported the work of theOregon Pesticide Education Network.

We sincerely appreciate the special contributions that the following individuals made to this report:
Jeff Allen, Lev Anderson, Robie Honeyman-Colvin, Caroline Cox, Georgia Ewing, Lita Furby, Norma
Grier, Neva Hassanein, Jacob Kann, Maureen Kirk, Becky Long, Kay Rumsey, Glen Spain, and Laura
Weiss.
We also value the following individuals and agencies who contributed photos and graphics that are
reproduced here with permission: Nancy Allen of Corvallis Environmental Center, K. Born, Andy
Duncan and Lynn Ketchum of OSU Extension and Experiment Station Communications, Institute forFisheries Resources, Kathryn Kostow, Tom and Pat Leeson, Oregon Dept. of Environmental Quality,
Oregon Dept. of Fish and Wildlife, Public Interest GRFX, Oregon Sea Grant, Ana Soto, Steve Stoneof National Marine Fisheries Service, and the US Fish and Wildlife Service.
The opinions expressed in this report do not necessarily reflect the views of the supporting
foundations and individuals.

Copies of this report can be found at:
http://www.pond.net/~fish1ifr/salpest.pdf

Diminishing Returns: Salmon Decline and Pesticides

Diminishing Returns:
Salmon Decline and Pesticides
Executive
Summary

TOAM AND PAT LEESON

By Richard D. Ewing, PhD
February 1999

About the Author:
Richard D. Ewing is a native Oregonian who graduated from Reed College in 1962, andreceived his Ph.D. in cellular and molecular biology from the University of Miami at Coral
Gables in 1968. After conducting research at Oak Ridge National Laboratory and at Oregon
State University, Dr. Ewing joined the research team at the Oregon Department of Fish andWildlife where he worked as a physiologist and hatchery specialist from 1975-1992. He left
ODFW to form Biotech Research and Consulting, Inc., a Corvallis-based consulting company
that specializes in hatchery operations and chemical analyses relating to fisheries. Dr. Ewing
has published widely in professsional journals and written many reports for the Oregon Department of Fish and Wildlife.
1Diminishing Returns: Salmon Decline and Pesticides

Executive
Summary
Pacific salmon are in serious trouble.
The enormous runs of migratory salmon of
the past have slowly diminished to thetrickle of adult spawning salmon that
presently inhabit western rivers. Althoughsalmon recovery efforts are underway,
scientists, policy makers, and interest
groups have thus far given insufficientattention to the role that pesticide contamination of our watersheds may play in salmon
decline. Accordingly, the purpose of Diminishing Returns: Salmon Decline and Pesticides isto review scientific literature on the effects ofsublethal concentrations of pesticides on
salmonids (see full report for documentation and references). The report places
special emphasis on how pesticides canalter the biology of fishes in subtle waysthat decrease their chances for reproduction
and survival.

Dynamics of Pesticides in theEnvironment
Pesticides include a broad class ofchemical and biological agents that are
purposefully introduced into the environment to kill or damage organisms, including insecticides, herbicides, and fungicides. Once applied, pesticides move into
streams and rivers throughout watersheds and may pose problems far fromthe site of application. Movement often
occurs through the medium of water,
thereby exposing all aquatic organisms
during this transport. Where water quality monitoring has been done, a great
variety of pesticides are typically found insalmon habitat. Federal and state agencies have established few criteria or stan2

dards for the protection of aquatic life
from short-term (acute) and long-term(chronic) exposure to pesticides.
Pesticides do not necessarily disappear
with time. They transform into other compounds that may be less toxic, of equal
toxicity, or of greater toxicity than theoriginal compound. The toxicity of thesebreakdown products is not well understood, and in general how they affectaquatic life has not been studied. All thewhile, fish and other aquatic organisms
must continue to cope daily with pesticides(and their breakdown products), some ofwhich are no longer used but remain inwatersheds.
Although pesticides are diluted bytransport in rivers and streams, a numberof mechanisms concentrate the chemicals,
often to toxic levels. In a process known
as bioaccumulation, pesticides absorbed
into plant and animal tissues may become
concentrated and reach levels manytimes higher than those in surrounding
water.

Diminishing Returns: Salmon Decline and Pesticides

Pesticide detections in the western United States as measured by the
U. S. Geological Survey NAWQA program.
State, region# Pesticides
Examined# Pesticides
Detected# Exceeding
Aquatic Life
Criteria1# For Which
Aquatic Life
Criteria
Are Available_______________________________________________________________________________________________

OregonWillamette Basin2
86
36
4
22
Washington
Puget Sound Basin3
NA
23
4
NA
Central Columbia
84
45
5
18
River Plateau4
California
San Joaquin Basin5
83
49
7
16
Idaho
Snake River Basin6
80
36
2
17
______________________________________________________________________________________
NA, not available.
1

Aquatic life criteria set by the National Academy of Sciences and National Academy of Engineering or by
the Canadian Council of Resources and Environment Ministers.
2
Data from Anderson et al. (1997).
5
3
Data from Dubrovsky et al. (1998).
Data from Bortleson and Davis (1997).
6
4
Data from Clark et al. (1998).
Data from Wagner et al. (1996).

Fish Kills and Acute Toxicity ofPesticides to Salmon
Pesticides are capable of killing salmon
and other aquatic life directly and within ashort period of time. For example, in 1996
the herbicide acrolein was responsible forthe death of approximately 92,000 steelhead, 114 juvenile coho salmon, 19 resident rainbow trout, and thousands ofnongame fish in Bear Creek, a tributary of
the Rogue River. Deaths of threatened
and endangered species from accidental
contamination of waterways are of grave
concern. The loss of each individual in asensitive population makes recovery
efforts that much more difficult. Fortunately, these deaths are relatively
infrequent.

Behavioral Effects of Pesticides
at Sublethal Concentrations
In contrast to dramatic fish kills, theeffects of sublethal concentrations of pesticides are more subtle and go largely unseen
and unregulated. Sublethal concentrationsof pesticides do not cause immediate death,but can interfere with the biology of theorganism in other ways and can ultimately
impact the survival of the species. Laboratory studies show that sublethal concentrations of pesticides can affect many aspectsof salmon biology, including a number ofbehavioral effects:• Long-term exposure to certain
pesticides can increase stress in juvenile3

Diminishing Returns: Salmon Decline and Pesticides

salmonids and thereby render them more
susceptible to predation.

examining sublethal effects of pesticides
because the effect is so common.

• Certain pesticides can alter swimming ability, which in turn can reduce theability to feed, to avoid predators, to defend
territories, and to maintain position in theriver system.

• Several pesticides (and other pollutants) have been shown to cause fish to seek
suboptimal water temperatures, thus subjecting them to increased dangers of disease
and predation.

• Many pesticides interrupt schoolingbehavior, a critical tactic for avoiding predation during salmon migration. Disruption of schooling behavior is thought bysome researchers to be a classic method for• Some herbicides have been shownto inhibit normal migration to the sea,
resulting in severe disruption of the life
cycle. There is a dearth of research looking
at this effect for common insecticides.

Sublethal effects of selected pesticides found in the WillametteRiver Basin Study by USGS.1__________________________________________________________________________________________________________
Herbicides
Insecticides
Atrazine
Simazine
Malathion
Chlorpyrifos
Carbaryl____________________________________________________________________________________________________________
Negative Effects on:
Food Supply
GrowthReproductive success
Bone Abnormality
Endocrine Disruptor
Immune System
Behavior
Schooling
Predator Avoidance

+2
+2
+2

+3
+6

+16
+20

+11
+14
+15
+17,18

+4
+7
+9
+12

+5
+8
+10
+13
+13,14+12,17

+12
+19

+18

____________________________________________________________________________________________________________________
Plus indicates a detectable response from sublethal concentrations of pesticide. Blanks indicate thatstudies were not found analyzing these effects. Superscripts are references.
1. Anderson et al. 1997.
2. Macek et al. 1976.
3. Naqvi and Hawkins 1989.
4. Washino et al. 1972.
5. Burdick et al. 1960.
6. Hermanutz 1978.
7. Brazner and Kline. 1990.
8. Arunachalam and Palanichamy 1982.
9. Jarvinen et al. 1983.
10. Carlson 1971.

4

11. Weis, P. and J. S. Weis. 1976.
12. Holcombe et al. 1982.
13. Weis, J. S. and P. Weis. 1976.
14. Bruckner-Davis 1998.
15. Plumb and Areechon. 1990.
16. Dodson and Mayfield. 1979b.
17. Hansen 1969.
18. Hansen 1972.
19. Weis, P. and J. S. Weis. 1974.
20. Lorz et al. 1979.

Diminishing Returns: Salmon Decline and Pesticides

OREGON DEPT. OF FISH AND WILDLIFE• Several studies suggest that certain
pesticides can impair salmonid’s ability totransition from freshwater to seawater.
There is a need for further research in thisarea, placing particular emphasis on thecritical period of transition that takes placein the estuary.
• Adult salmon adjust their migration
patterns to avoid polluted areas, resulting
in delayed spawning.
During early development, fish are especiallyvulnerable to pesticides that can mimic natural
hormones.

Compromised Immune Systems
In addition to changes in behavior,
exposure to relatively low concentrations ofpesticides can disrupt the immune systemof salmon. Evidence for these effects insalmonids is not as extensive as for disruption of behavior, but the data available
suggest that pesticides can have serious
negative impacts on the immune system.
Such disruption results in the onset of
disease and even death.

Endocrine Disruptors
Fish and other organisms are especiallyvulnerable to endocrine-disrupting effects
during the early stages of development.
Pesticides at low concentrations may act as
mimics or blockers of sex hormones, causing abnormal sexual development, feminization of males, abnormal sex ratios, andunusual mating behavior. The uniqueplasticity of sex differentiation in fish suggests that these animals may be very susceptible to disruption of sexual characteristics by pollutants. Pesticides can also interfere with other hormonal processes, such as
thyroid functioning and bone development.

OREGON DEPT. OF FISH AND WILDLIFE

Indirect Effects of Pesticides on
SalmonPesticide exposure at the fry stage can cause
feminization of male fish or even sterility.

Pesticides can indirectly affect fish byinterfering with their food supply or altering the aquatic habitat, even when theconcentrations are too low to affect the fishdirectly. Such indirect effects greatly reduce
the abundance of food organisms which inturn reduces the growth and probability ofsurvival of the fish. In addition, removal of5

Diminishing Returns: Salmon Decline and Pesticides

aquatic vegetation can decrease habitat
suitability and increase the salmon’s susceptibility to predation. These indirect effects
are subtle, but evidence suggests that incomplex ecosystems indirect effects can beeven more important than direct effects.

Recommendations

Ecoepidemiological investigations in the
Great Lakes have established the relationship between chlorinated hydrocarbons andthe decrease in lake trout populations. An
ecoepidemiological approach for salmon in
the Pacific Northwest would be particularly
valuable because it is designed to attributecausality to events occurring in real-world
situations.

From the evidence available at present,
there is a plausible basis for considering
pesticides to be one of the causes of declining salmon populations in the PacificNorthwest. Based on this review, we offer
several policy recommendations and identify areas for further research:
1. Address the impacts of pesticides
on salmon when developing and implementing recovery plans for threatened andendangered species. To date, efforts torecover salmon have devoted insufficientattention to pesticides as a contributing
factor in salmon decline. We must act now
using available information to formulate
management strategies that will minimize
the potential danger from sublethal concentrations of pesticides.

2. Conduct ecoepidemiological studies in critical salmonid habitat. Most of
the effects of pesticides referred to in thisreport have been determined in experimental laboratories. In the field, however,environmental conditions are not controlled, and many factors interact to confuse
the determination of direct relationships.
6

3. Create comprehensive pesticidetracking systems in the Pacific Northwest.
To better understand the relationship between pesticides and salmon decline, wemust have accurate, site-specific data on thepatterns of pesticide use in the watershedsof the Northwest. State and provincial
governments need to collect data on which
pesticides are used where, when, and inwhat amounts. Such data can then be
combined with watershed-specific information on indicators of salmon health. (Currently, California is the only state withPacific salmon habitat where such information is collected.) Pesticide use information
will also enable efficient instream monitoring for pesticide contamination.
4. Establish instream monitoring
programs in critical salmon habitats. A
systematic monitoring program for pesticides and their breakdown products needs
to be undertaken. Not all pesticides can betested for in all locations, but current testing
is woefully inadequate for understanding
the role of pesticides in salmon decline.
In conjunction with pesticide use data,
these analyses can be targeted to theDiminishing Returns: Salmon Decline and Pesticides

pest management approaches that do not

NEVA HASSANEIN

Ordepend
egon’son pesticide use in agricultural andoceannon-agricultural settings should be encourgoingaged and further developed. There issalmonample evidence that ecologically sound andeconomically viable methods can be successfully implemented. The adoption ofsuch alternatives can be encouraged
through technical assistance, financial
incentives and disincentives, demonstration programs, and information exchange
opportunities.

compounds of most concern. Such targeting can greatly improve the cost-effectiveness of monitoring.
5. Err on the side of caution whensetting water quality standards for pesticides. There are few established criteria forthe protection of aquatic life from pesticides. Moreover, evidence reviewed here
shows that sublethal effects on salmonids
have not been fully appreciated, that juvenile salmonids succumb more easily totoxins in the water, that laboratory studies
do not reflect the natural life cycle of thefish, and that little is known about how
pesticides affect aquatic ecosystems. These
factors must be considered when setting
standards, and a precautionary approach
must be adopted.
6. Prevent pesticide contamination of
salmonid habitat by reducing pesticideuse. Once contaminated, water is difficult
if not impossible to clean up. Therefore,

7. Adopt state and provincial programs in the Pacific Northwest to phaseout pesticides that persist andbioaccumulate in the environment. Numerous pesticides, including some that are
no longer used and many that are currently
used, are known to persist in the environment and to bioaccumulate in aquatic
systems. Washington State’s Departmentof Ecology is now considering a plan toend the release of such toxins, including
certain pesticides, into the environment.
To ensure salmon recovery, all state andprovincial governments in the PacificNorthwest should adopt similar
programs.

7

For more information…
Northwest Coalition for Alternatives to Pesticides
P.O. Box 1393
Eugene, OR 97440-1393(541) 344-5044; fax (541) 344-6923
www.efn.org/~ncap
Oregon Environmental Council
520 SW 6th Ave., Suite 940
Portland, OR 97204(503) 222-1963; fax (503) 222-1405
www.orcouncil.org
OSPIRG Foundation
1536 SE 11th Ave.
Portland, OR 97214(503) 231-4181; fax (503) 231-4007
www.pirg.org/ospirg
Institute for Fisheries Resources
PO Box 11170
Eugene, OR 97440-3370(541) 689-2000; fax (541) 689-2500
www.pond.net/~fish1ifr