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OCR for page 275
11
Salmon-Fishery Management Concepts
While Pacific salmon fisheries developed rapidly during their early history,
our ability to manage them did not. Much of the basic biological understanding
of Pacific salmon and information that could be used to manage salmon fisheries
were being developed as the fisheries developed, but their application to manage-
ment developed much more slowly. In his review of salmon management during
the first century of Pacific salmon fisheries, Larkin (1970) suggested that almost
from the beginnings of the industry two ideas were implicit in attempts at man-
agement: that salmon returned to their home stream to spawn and that catches in
each river had to be limited. Those continue to be the biological bases for
management, and we continue to struggle with their incorporation into a sustain-
able management concept.
Papers by McHugh (1970) and Larkin (1970) provided historical perspec-
tives on the development of fishery science and management of Pacific salmon in
North America. Initially, scientific investigations consisted largely of descriptive
biology and examination of the "home-stream concept." The scientific basis of
that concept was debated long after its acceptance in management (see, for ex-
ample, Jordan 1925, Moulton 1939~. But acceptance, coupled with the early
recognition that salmon eggs were easily cultured, resulted in hatcheries' becom-
ing the major management activity during the first 50 years of the industry. By
the late 1930s, however, management of Pacific salmon was in transition. Larkin
(1970:226) reported that "regulations for controlling harvest were inadequate,
but insufficient information existed on which to construct better techniques; hatch-
ery practices were fairly advanced but of dubious value; inroads on salmon
production as a consequence of the development of other resources were begin
275
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276
UPSTREAM: SALMON AND SOCIETY IN THE PACIFIC NORTHWEST
ning to cause concern." The 1930s began a period of more-quantitative assess-
ment in fishery management (Cushing 1988, McHugh 19701. The quantitative
basis of salmon management was provided by Ricker's 1954 seminal paper on
stock and recruitment. Since then, management of Pacific salmon fisheries has
been premised on his stock-recruitment theory.
STOCK1 AND RECRUITMENT
Salmon-fishery management assumes that there is surplus production below
some upper size of the spawning population. Surplus in the case of salmon
means that a given number of spawners in an adult generation produces, on
average, more progeny than needed to replace the parents and overcome all
natural mortality sources from the time fertilized eggs are deposited in the gravel
of natal streams, through juvenile and immature life phases, to adulthood. The
number of surplus animals varies with the size of the population and the natural
mortality rate. Smaller populations tend to have higher productivity than larger
populations (i.e., number of progeny returning per adult spawner), and their total
production is limited mostly by the number of eggs deposited. In larger popula-
tions, production depends more on the interactions between spawners and habitat
required for sustaining survival and growth of progeny.
Ricker (1954) noted that factors that become more effective at high densities,
called "compensatory" factors by Neave (1953), control or regulate salmon popu-
lations. Compensatory mortality factors place more pressure on high-density
than on low-density populations. For example, when large numbers of pink
salmon reach their spawning grounds, some adults are forced to use less-suitable
gravels at stream margins; in crowded conditions, late spawners might even dig
out developing embryos deposited by earlier spawners. Those factors decrease
the number of progeny produced per female. When chinook or steelhead spawn-
ers are less abundant, the resulting fry, fingerlings, and pre-smolts have more
access to feeding positions and cover, so they may grow faster and be less vulner-
able to predation.
Ricker (1954) termed the relationship between the number of spawners (stock
or S) and the production of progeny (recruitment or R), the stock-recruitment
function. The term recruitment refers to the potential availability of fish to a
fishery or to form the next spawning generation. The stock often is referred to as
the escapement, because these fish escaped capture by a fishery and return to
spawn.
Fishery managers have attempted to maximize surplus production (i.e., an
iThe terminological difficulties associated with the word stock are discussed in Chapter 4. To
permit comparison of the discussion in this chapter with much of the published literature on fisheries,
we use the term stock here. although we use the term population in most of the rest of the report.
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SALMON-FISHERY MANAGEMENT CONCEPTS
277
mats available for catch) by maintaining the number of spawners at an abundance
at which, according to Ricker's stock-recruitment theory, they are likely to pro-
duce the largest sustainable catch. Figure 11-1 is an example of a hypothetical
Ricker stock-recruitment function. In reality, the function would be fitted statis-
tically through a scatter of data points collected over time. The function repre-
sents the average response expected given an escapement under the environmen-
tal conditions that existed when the data were collected. If escapements merely
replaced themselves in the next generation, those returns would fall along a
"replacement line" where R = S (line A in Figure 1 1-13. However, if the function
value Rat expected for a particular So exceeds the replacement value, then a
surplus production (R~ - Sit could be caught and the population maintained in
equilibrium at the same future S and R numbers. Salmon populations can main-
tain themselves at several levels of abundance, and different salmon populations
have different stock-recruitment curves. In Figure 11-1, curve B describes a
population with greater productivity than curve C, but one with greater density-
dependence at large spawning stocks. Populations with greater productivity can
sustain their production at higher exploitation rates.
The S number that, on average, maximizes the catchable number of fish
generation after generation is referred to as the optimum escapement, and the
associated catch is the maximum surplus reproduction or maximum sustained
yield (MSY). The escapement expected to provide MSY is indicated as SMSY in
Figure 1 1-1. It occurs where the slope of the recruitment curve is 1.0, the tangent
to the curve parallel to the replacement line. Once SMSY is determined, the rate of
exploitation that can be sustained by the population to maintain MSY can also be
determined' i e ~ (RMSY - SMsY)/RMsY In this figure, the surplus production
(R~ - Sly is equal to MSY.
Other stock-recruitment models have been proposed. The Beverton-Holt
model (1957) predicts that the number of recruits increases with spawning stock
ever more slowly and never exceeds a particular value (asymptote). This model
does not turn downward at high S. as with Ricker's model.
Stock-recruitment functions, whether Ricker's or Beverton-Holt's, share sev-
eral serious limitations for application to salmon management. The principal
limitations are related to
· The estimation of the biological production function in a highly variable
natural environment.
lions.
· Differences between populations and change over time within popula
· The necessity for accurate data on total fishing mortality by age and
population over all fisheries, on number of spawners by age, and on future pro-
duction.
An individual data point (i.e., the recruitment from a parental spawning
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278
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
!
o (,k,
0 0.2
-
S MSY
UPSTREAM: SALMON AND SOCIETY IN THE PACIFIC NORTHWEST
R1
-
/ MSY = R1- S1\ ,
/ ' TIC
.,
ROB
0.4 0.6 0.8 1
Spawners (S)
1.2 1.4 1.6
FIGURE 11-1 Hypothetical Ricker stock-recruitment curves relating number of animals
reproducing (spawners) and production of mature progeny (recruitment). Other letters
explained in text.
stock) reflects biological processes, effects of environmental variability, and ran-
dom events. Determining an appropriate production function in the presence of
this variability requires a long series of data on returns over a wide range of
spawning-stock sizes. The uncertainty about a recruitment function is usually
high. For example, even in a sockeye population with 41 years of good assess-
ment information, a characteristic recruitment function is not evident (Figure 11-
2a). The relationship between spawners and juvenile production in freshwater is
more evident (Figure 1 1-2b', but variability in marine survival weakens both the
relationship between spawners and adult returns (Figure 11-2a) and between
downstream migrants (smelts) and adult returns (Figure 11-2c). The latter rela-
tionship would already account for variation in returns attributable to variation in
freshwater survival. Even in the population modeled in Figure 11-2, the estimate
of SMSY is uncertain; SMSY = 332,000 with a 90% confidence range between
203,000 and one million spawners. This confidence range was estimated from
1,000 computer simulations of the relationship between adult spawners and adult
recruitment. The distribution of the simulation results (Figure 11-3) indicates the
uncertainty associated with estimates of the optimal escapement value for this
population. Furthermore, the scatter plot of alpha versus beta values (SIR param
OCR for page 279
SALMON-FISHERY MANAGEMENT CONCEPTS
in
o
x
in C\]
Hi:
CO
o
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X
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in
O
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0
.
O ~
· ~
·,W'.
~ -
7.'. ~
-
-
.
.
0 1 2 3
Spawners (x 105)
; "I
.
.
· /'
,/e'
At, .
,/
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0 1 2 3
Spawners (x 105)
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, , , , , , , 1
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10 15 20 25 30 35
Smolts(x106)
279
A
B
C
FIGURE 11-2 Ricker stock-recruitment
data and functions for Chilko Lake sock-
eye salmon from Fraser River. A, adult
spawners and adult recruitment; B. adult
spawners and juvenile downstream mi-
grants (age 1 + smelts); and C, migrants
and adult returns.
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280
o CO
o
x
_ o
o
UPSTREAM: SALMON AND SOCIETY IN THE PACIFIC NORTHWEST
~ . ~ ~ out 1~1ll
0 2 4 6 8 10 12
ESCAPEMENT (x 100,000)
4 6 8 10
OPTIMAL ESCAPEMENT (x 100,000)
·`
_ ,~.- , . ,
Z~-
.
.
o.o 0.2
0.4 0.6
FIGURE 11-3 A, results of 1,000 bootstrap simulations of Chilko sockeye Ricker stock-
recruitment function. B. distribution of 90% confidence interval for optimal spawning-
stock sizes determined by simulations. C, bivariate scatter plot of Ricker stock-recruit-
ment parameters determined from each simulation.
eters in the Ricker function) indicates that these parameters are correlated (the
oval shape of the 90% joint confidence limit indicates correlation). The wide
variation in the alpha value is associated with wide variation in beta; this results
in a highly uncertain stock-recruitment function for this population. In salmon
populations in which recruitment and spawning stock sizes have been monitored,
annual variation in the ratio of returns to spawners can vary by a factor of 10.
Recently the marine survival rate of chinook salmon released from Robertson
Creek Hatchery (on the west coast of Vancouver Island, B.C.) has been shown to
vary by a factor of more than 100 (0.1%-13.7% survival to the second year).
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SALMON-FISHERY MANAGEMENT CONCEPTS
281
Many years of data would assist in accounting for that variability, but long-
term data can involve another problem. The function calculated reflects returns
per spawner under past environmental conditions. If the environment changes,
the stock-recruitment function changes. An obvious example is deterioration of
freshwater environments, as evidenced in increased deaths associated with dams,
reduction in area available for spawning or rearing because of water abstraction,
or sedimentation in spawning gravels. Change in marine survival (see Chapter 2)
also can alter the stock-recruitment function. Environmental variability makes
questionable how representative any stock-recruitment function will be for cur-
rent and future environmental situations. Limiting data to periods considered to
be more "typical" of existing conditions might be possible, but the resulting
decrease in data points would increase uncertainty substantially.
The most common concern about managing for MSY in salmon fisheries is
that stock-recruitment functions vary among populations. The MSY for a popu-
lation is determined by its productivity and sources and magnitudes of density-
dependent mortality rates, which reflect the life history of the species and the
specific habitat in which the population lives. Stock-recruitment functions are
expected to vary, but the paucity of reliable data on population-specific functions
makes it hard to account for the differences. An obvious example is the compari-
son of wild-spawned versus hatchery-reared salmon. A hatchery population can
sustain its maximum catch at substantially greater exploitation rates than can a
natural population because mortality associated with spawning and freshwater
rearing is much lower in a hatchery than in natural systems. Assuming that after
release marine mortality sources do not compensate, fewer parents are needed to
reproduce the recruitment from a hatchery population (see Chapter 121. Direct
comparisons of stock-recruitment functions for hatchery and wild populations (in
the same geographic area and period) are rare. One good comparison involves
sockeye salmon in the lower Fraser River f Figure 1 1-4), where an artificial spawn-
ing channel in Weaver Creek enhances the fry productivity of that population but
later rearing occurs in the natural environment. Two other populations, from
Birkenhead and Cultus lakes, are produced naturally and have the same adult run
timing as Weaver Creek; all three populations are fished simultaneously. The
catchable surplus from Weaver Creek is greater than that in the natural popula-
tions. The exploitation rates to sustain these populations at MSY are 0.76 for
Weaver Creek, 0.70 for Birkenhead Lake, and 0.62 for Cultus Lake. The spawn-
ing channel has increased the productivity of the Weaver Creek sockeye, but
fishing to maximize the catch from Weaver Creek would mean overfishing re
turns to both natural populations.
The hatchery-wild dichotomy presents an extreme example of the "mixed-
stock" fishing problem. If fishing responds to apparent abundance without con-
sideration of the stock composition (i.e., the mixture of portions of stock from
source populations) or if fishing levels are based on hatchery production, the
natural population will be overfished and its production will, on the average,
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282 UPSTREAM: SALMON AND SOCIETY IN THE PACIFIC NORTHWEST
1.2
~_
so
. ~
~ 0.6
o
cat
0.8
0.2
-- Birkerlhead
Cultus Lake
---- Weaver Creek
- ' S = R
.1 '.N
I.
I,
I.
0 0.125 0.25 0.375 0.5 0.625 0.75
Spawners (S)
FIGURE 11-4 Ricker stock-recruitment curves for three Fraser River sockeye salmon
populations. Weaver Creek population is enhanced but Cultus and Birkenhead popula-
tions are both naturally spawning. Source: Data collected 1946-1990 by International
Pacific Salmon Fisheries Commission and Canada's Department of Fisheries and Oceans.
decline. Alternatively, if the fishery is managed to sustain the natural population,
substantial surplus production will return to the hatchery or could be caught in a
single-population, terminal fishery.
The example of mixed-stock fishing represents a much more general prob-
lem. Differences in productivity between natural populations cause the same
problem, and by-catch of other species in fisheries that are directed at a more
productive species is an analogous problem. When fishing occurs on a mixture
of populations with different stock-recruitment functions and fishing cannot be
regulated at a rate appropriate for each component population, the stage is set for
overfishing of the less-productive components (Ricker 1958, 1973; Hilborn
19853. For example, extinction of wild coho salmon in the lower Columbia River
has occurred as fishing pressures at sea and in the lower Columbia increased to
take hatchery returns; catch levels of 85-95% were directed at the returning fish
(Cramer et al. 1991~. The less-productive stocks are referred to as "weak stocks,"
but that term leads to confusion. "Weak" cannot be equated with "small," nor
does it imply anything maladaptive, inferior, etc., about animals in the popula
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SALMON-FISHERY MANAGEMENT CONCEPTS
283
lion. The "mixed-stock" (or mixed-population) fishery problem is related to
differences in production rates, not the relative size of populations.
Apart from natural variability and variation among populations or over time,
estimating the SMSY for just one population raises a serious question. Larkin's
(1977) discussion of MSY as a management concept identifies the issue of the
poor quality of the data available for use in stock-recruitment analysis, and re-
cently the joint U.S.-Canada committee on chinook salmon stated (PSC
1993b:87~:
At present, complete information necessary to determine stock productivity is
not available for any individual chinook stock! For a few stocks, enough infor-
mation has been available to apply stock-recruitment type analyses to estimate
productivity parameters, but even these had to involve some major assumptions
about age structure in catch and/or escapement and about the error structure of
these data. And none include environmental factors, which are known to pro-
duce variability in annual production.
To determine stock-recruitment functions is data-intensive, expensive, and statis-
tically nontrivial. Data and cost issues are related to accurate determination of a
population's mortality in each fishery and its spawning escapement by age so that
production can be related to the parental generation. Salmon tend to be caught in
many sequential, mixed-stock fisheries, and their escapement is not determined
easily. There are few cases in which this challenge has been met to study salmon
population dynamics, and the sensitivity of stock-recruitment analyses to errors
in the data is poorly understood. Hilborn and Walters (1992) stated that stock-
recruitment analyses can provide "terribly misleading answers" and that (p. 287)
the types of misleading answers produced by stock and recruitment analysis are
almost always the same; the answers mistakenly lead you to believe that recruit-
ment will not decline very much with spawning stock. We think that bad stock-
recruitment analyses have been a significant factor leading to over-exploitation
and stock collapse for some major fisheries.
Hilborn and Walters reviewed the problems associated with stock-recruitment
analyses in greater detail than is appropriate here, but the committee has devel-
oped an example of the consequences of such analyses (Box 11-11. The most
common outcome of simple stock-recruitment analyses is that the optimum ex-
ploitation rate is overestimated and the SMSY underestimated. The consequence
of this outcome could be management advice that unintentionally would lead to
overfishing and contribute to declining production.
Although MSY concepts have provided the basic paradigm for salmon man-
agement since the l950s, the paradigm has been inadequate, given the fishing
pressure and economic development in the Pacific Northwest. Mixed-population
fisheries, habitat change, and uncertain assessment advice have all contributed to
overfishing and loss of less-productive populations. The committee reiterates
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UPSTREAM: SALMON AND SOCIETY IN THE PACIFIC NORTHWEST
Larkin's caution about the inadequacy of the MSY concept for salmon manage-
ment (Larkin, 1977:91:
The foregoing has demonstrated, I hope, that MSY is not attainable for single
species and must be compromised: (1) to reduce the risk of catastrophic decline
and reduction of genetic variability; and (2) to accommodate the interactions
among the species of organisms that comprise aquatic communities.
Given that the limitations of stock-recruitment analyses have been known for
many years, why are management strategies based on those models? Part of the
answer is that technical improvements in analyses has led to unjustified confi-
dence in abilities to compensate for deficiencies. Much of the answer, however,
lies in the socioeconomics of fisheries and fishery management. In the United
States and Canada, marine fish are generally viewed as "common property"
resources, owned by no one-or by the public until they are caught. Such a
situation is well known to lead to excessive investments in capital and labor and
to pressures to overfish resources, particularly when there is open entry (i.e., no
limit on the number of people who can fish) (Gordon 1954, Scott 1955,
Crutchfield and Pontecorvo 19691. However, salmon fishing in the Pacific North-
west is not now (and has not been for a long while) an open-entry fishery. The
states of Washington, Oregon, and Alaska and the province of British Columbia
have limited entry into the salmon fishery since the 1960s; this has not prevented
overcapacity in boats, gear, and fishing technology, but it has raised greatly the
costs of participating in the fishery and reduced overall numbers of people and
boats in it. Higher costs of entry and higher investments increase the needs of
fishers to pressure regulatory agencies to allow higher catches at the expense of
spawning requirements.
The problem has long been recognized (e.g., Wright 1981, Ludwig et al.
19935. Wright stated (p. 38)
Fishermen make poor management allies due to their perpetual optimism
about strengths of the salmon runs and their understandable preoccupation with
short-term economic considerations.
There can be little doubt, however, that the salmon fishery lobbyists are
currently winning the battle against the spawning-escapement protectors. A
team of fishery scientists formed by the Pacific Fishery Management Council
concluded that 40% more chinook salmon and coho salmon were needed to
meet spawning-escapement requirements, under existing habitat conditions, for
the combined areas of California, Oregon, and Washington (PFMC 1978:39).
Similar appraisals can be found in Fraidenburg and Lincoln (1985), Walters and
Riddell (1986), and National Research Council (NRC 19941. The remedies sug-
gested most commonly, besides complete but preferably temporary closures of
the fisheries (as occurred in 1994), include restructuring managing bodies to
remove apparent conflicts of interest (NRC 1994) and privatizing rights of access
to salmon stocks through individual transferable quotas or similar devices, per
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SALMON-FISHERY MANAGEMENT CONCEPTS
285
haps combined with buyouts or other compensations for displaced fishers. A
third approach, paradoxically, is to strengthen the involvement of fishers in the
management process so that they are encouraged to take more responsibility as
stakeholders in either a common property or a privatized fishing situation (cf.
Scott 1993~. Hanna (in press) suggested that the Pacific Fishery Management
Council (PFMC) has already moved a long way toward involving fishers in the
management process, at least for other species of fish.
The application of stock-recruitment theory and MSY as the basis of salmon
management is complex and of limited applicability. The multitude of popula-
tions and habitats, the extent of enhancement programs, and the variability and
uncertainty in the data make determining an accurate optimal escapement goal
elusive. However, where the necessary data are available, stock-recruitment
relations can be clear (see Box 11-21. The definition of the relationship depends
on the degree of environmental variability, the causes of density-dependent mor-
tality, and data quality. Given the poor quality of the data available on almost all
Pacific salmon populations, we cannot test the stock-recruitment theory rigor-
ously. We have learned that the theory is more applicable in freshwater phases of
salmon life history and that environmental variability in the marine habitat ulti-
mately can determine the number of returning adults. Principal lessons are that
salmon stock-recruitment relationships are inherently uncertain, that the determi-
nation of a specific escapement goal (SMSY) is seldom justified by available data,
and that the MSY concept has been inadequate for conserving population diver-
sity or production.
FISHERY MANAGEMENT IN THE FUTURE
The committee explored four general options for managing fisheries to help
frame the process of developing a new management paradigm: status quo, no
fishing, limited entry, and terminal fisheries.
The Status Quo
One management option is to continue to use the MSY concept while work-
ing to improve its predictive powers. The committee has concluded, however,
that the MSY concept by itself is inadequate and impractical as a basis for salmon
management because the model implies the existence of a continued surplus
production, which is fundamentally inconsistent with historical data. In over-
fished populations, most stock-recruitment data will be from the lower range of
escapement numbers. We can adjust for biases in data, but we cannot correct for
the absence of data at larger escapements without actual observations. If we
estimated SMSY on the basis of historical data and managed perfectly by annually
achieving this value, we would learn nothing about the productive potential or
dynamics of a population; we would learn more only about natural variability in
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SALMON-FISHERY MANAGEMENT CONCEPTS
291
stop all ocean recreational, charter, and commercial fishing for salmon in Alaska
and the Pacific Northwest. Such a ban would have favorable effects on negotia-
tions with Canada in the PSC. However, it would be fought by all those affected.
Another variant of this option would be to close all ocean fisheries in the Pacific
Northwest. A complete ban of ocean fishing is close to being realized. It was
proposed in 1993 for coho by the PFMC. It was proposed again in 1994 and
implemented for coho, leaving only limited fishing periods for chinook. That
was not the first time a no-fishing option has been proposed. In 1904, J.P.
Babcock, the British Columbia fisheries commissioner, unsuccessfully proposed
closing fishing on the Fraser River during 1906 as a conservation measure to
build up sockeye stocks. The problem with any partial closure is that, although it
might allow some increased escapement, it also redistributes catch among differ-
ent fishing interests.
Canada and the United States have many points of complementary and coop-
erative interest that might be negotiated on a smaller, more-specific scale, rather
than simple wide-scale closures. One point of complementarily is the catches of
Pacific Northwest coho and chinook off the west coast of Vancouver Island and
Puget Sound catches of Fraser River sockeye. Another point of complementarily
is the possibility of opening ocean fishing areas to a joint fishery of trollers from
Alaska, Canada, and the Pacific Northwest.
The Limited-Entry Option
If cessation of fishing is too strong an option, limiting the number of fishers
might be helpful. All West Coast commercial salmon fisheries have some form
of limit on the number of gill-net and troll licenses. The underlying idea is that
the number of fishers should be limited to correspond to the size of catch that can
be taken. The objective of the license-limitation program is to restrict fishing
capacity to a level closer to the effort that can be maintained. One problem with
limited entry is that it has many of the same elements as the status quo. Limiting
entry to the degree necessary to produce the needed effect is perceived as a severe
step.
A second problem that limited entry does not solve is the natural tendency of
fishers to become more effective. New technology, knowledge, and fishing
methods make fishers more efficient with the gear that they have. Thus, a
limited-entry program must continually reduce the number of fishers in accor-
dance with both resource availability and the capacity of fishing vessels and
fishers to catch salmon (Smith and Hanna 1990~; a reliable way to do this has not
been perfected.
A third problem is that, as with open-access fisheries, successful application
of limited entry depends on the ability to calculate accurately the quantity avail-
able for fishing. People want a consistent number, but fisheries are inherently
variable; no stable number can be given. A safe number would have to be
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UPSTREAM: SALMON AND SOCIETY IN THE PACIFIC NORTHWEST
conservative, and fishers would probably complain that it is too low. The MSY
mode of management has continually overestimated the amount available for
fishing. With management for genetic diversity, as we have been recommending
throughout this report, the focus is on achieving spawning escapements. That
will mean highly variable catch opportunities for a much smaller fleet of vessels.
The Terminal-Fishery Option
Catching salmon closer to the place where they spawn allows greater separa-
tion of hatchery from wild and threatened from nonthreatened populations. A
way to achieve that separation is to allow only terminal fisheries. The separation
can be even better achieved with live traps. With live-trap, terminal fishing,
salmon needing protection can be released if they are identifiable with minimal
potential for harm. Because natural mortality in the ocean, after early transitions
to ocean life, reduces biomass more slowly than body growth adds biomass to the
population, fishing closer to the spawning grounds would increase salmon yields.
Ocean fishers might question the quality of salmon taken in terminal fisher-
ies; the meat of fish caught nearer to their spawning grounds will tend to be less
oily and the skin more colored, and they will be less preferred by some consum-
ers. Salmon do deteriorate in quality as they get closer to spawning, but terminal
fisheries in estuaries and river mainstems would not necessarily decrease quality
and the average size of the fish would be greater. Two advantages of live-trap,
terminal fisheries are the potential to separate populations from one another and
the ability to set catch rates for what each population can sustain. For example,
salmon from threatened populations could be released. The treaty fishery in the
middle Columbia would be a place to experiment with terminal fishing. Shifting
to a live-trap fishery also has the potential to increase employment. Recreational
fishers view set nets as wasteful of the resource and as yielding lower-quality
fish. Live traps would improve the perception of Indian fishing on both conser-
vation and quality grounds.
A major problem with the no-fishing option is at least partially solved by
adopting terminal fisheries. Alaskan fishers catch salmon destined for Alaska
and British Columbia streams, as well as for the Columbia River and the north
coastal area. Alaskan ocean fishers question why their opportunity to fish for
healthy Alaskan populations should be jeopardized by habitat and hydropower
problems in the Pacific Northwest. Canadian fishers who fish mixed U.S., Cana-
dian, and Alaskan populations do not see a reason to limit themselves when the
problem is not theirs. They have not built dams on the Fraser River, and in
British Columbia the habitat is less altered.
Although the current catch situation which is unbalanced between areas-
will make it politically difficult to restrict fishing to locations of origin, the
committee concludes that it is worthwhile and important. Salmon management-
especially population-specific management-is likely only practical if catch were
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SALMON-FISHERY MANAGEMENT CONCEPTS
293
allowed only near the point of origin, and in the long run, the salmon and many
fishers would benefit once production increased, although which fishers benefit
most would involve social factors.
Developing a New Management Paradigm
Given the complexity and scope of the salmon problem, developing a new
management concept will be difficult and contentious. The committee starts by
identifying several premises based on its experience:
· In Pacific salmon, the presence of many diverse, spatially distributed
spawning populations is closely aligned with genetic diversity, maximal use of
available habitat, and potential for increasing production from natural spawners.
The sustainable exploitation rate is a function of a population's productiv-
ity determined over all life phases. Catch is only one of numerous mortality
sources and cannot be viewed as independent or as an alternative to other sources
over which we do not have control. The fishable portion of a return is determined
by the brood-year survival to the time of the fishery and the desired spawning-
stock size.
.
.
Salmon are a component of ecosystems and they exist in a dynamic evo-
lutionary process. Their production is variable and interconnected with the con-
dition of their communities and habitats.
· Catch is a function of the fishing rate exerted by a fishery and the abun-
dance of salmon recruited to the fishery. A low fishing rate and a high abundance
can yield the same catch as higher fishing rate and a lower abundance.
· Productivity varies among populations and over time. The projected
return from any population and brood year is highly uncertain. Any management
process must acknowledge and account for limitations and uncertainty in assess-
ment information and management capabilities.
Those premises consider only biological aspects of fishery management. But the
sustainability of salmon in the Pacific Northwest also is inextricably linked to
economic development and societal values. Society in the Northwest has ex-
changed natural salmon populations for economic development or argued about
who was to blame as the resource declined. Figure 11-5, based on data from
Matthews and Waples (1991), demonstrates the decline in Snake River spring
and summer chinook salmon since the late 1950s. In spite of a progressive
decline, major corrective actions were not taken until 1992, when the chinook
were listed as threatened under the Endangered Species Act. The greater the
decline in the resource, the greater the disruption will have to be to correct the
problem. The committee believes that a stronger societal commitment to the
biological-resource base must be established if salmon are to be sustained. For
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5
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UPSTREAM: SALMON AND SOCIETY IN THE PACIFIC NORTHWEST
14
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FIGURE 11-5 Trend in spawning-escapement index for Snake River spring and summer
chinook salmon. Trend in annual read counts and 5-year sum (for smoothing) are pre-
sented. Data from Matthews and Waples (1991) for Snake system minus Grande Ronde
returns.
the fishery-management process to be effective, a strong commitment to the
salmon must be an integral part of the process.
A management cycle for fisheries involves four activities: stock assessment
to provide the biological advice, development of management plans, conducting
the fisheries, and evaluation. The critical elements are sound biological advice,
explicit and assessable management objectives (biological, social, economic,
etc.), an institutional process for developing management plans, control of fisher-
ies, and accountability in achieving management objectives. We consider those
elements below, except for institutional processes and accountability, which are
discussed in Chapter 13.
Stock Assessment and Biological Advice
Biological advice is only as sound as the information on which it is based.
Advice must recognize limitations and uncertainties in knowledge and in abilities
to predict recruitment. For example, the committee suggests that the concept of
"optimum escapement" be replaced with a more conservative notion of a mini-
mum sustainable escapement (MSE). An MSE concept avoids a single target
escapement value and acknowledges that estimates of SMSY are often biased low
and rely on weak historical data. The committee emphasizes that MSE is a
minimum and that actual escapements would exceed it and not be scattered about
it. The committee's notion was based on protecting against the continued decline
in salmon production and on concern about the use of an uninformative, possibly
misleading, statistic.
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SALMON-FISHERY MANAGEMENT CONCEPTS
295
The MSE level could initially be determined from historical stock-recruit-
ment data. When the data are not available, initial escapement levels may be
derived from habitat assessments and/or historical escapement trends. This infor-
mation may then be incorporated in demographic or life history models to deter-
mine MSE at a particular level of confidence. In explicitly accounting for uncer-
tainty in achieving the target, the concept of MSE is analogous to minimum
viable population size (Shaffer 1981, Simberloff 1988) and population viability
analysis (Gilpin and Soule 1986, Shaffer 1990~. It acknowledges that the longer-
term sustainability of salmon populations depends on reducing the risk of extinc-
tion due to overfishing and stochastic events (environmental and demographic
variability) and imprecision in fisheries management. However, in assessing
these risks, society must determine the level of security desired for salmon popu-
lations over what time period (i.e., how confident do we want to be that an MSE
is achieved annually and that a population will exist in 100 or 200 hearse.
In many cases, the appropriateness of the initial MSE will be unknown.
However, under the MSE concept, populations would generally be at less risk
than under the earlier MSY approach, because escapements should exceed the
MSE rather than fluctuate around it. MSE would be expected to lead to greater
escapements, on the average, than achieved by the conventional application of
the MSY concept. In practice, it will be important to allow variability in escape-
ments above MSE in order to examine the productive capacity of populations and
habitats, and the appropriateness of the MSE value.
Estimates of MSE should ideally include information about the composition
of spawning populations, the maintenance of connections between salmon domes,
the role of carcasses as nutrient sources for freshwater ecosystems, intraspecific
competition in reproduction, mate selection, and gene flow, but relatively little
attention has been given to these factors. The need for levels of escapements that
promote competition and fertilization or that maintain niches used by salmon is
not well demonstrated with direct research.
In summary, the committee recommends the establishment of minimum safe
levels of spawning escapements to reduce the risk of continued loss of salmon
populations and production. Actual escapements should always exceed this value,
with allowances for assessment error for abundances near this minimum level.
Escapements would vary above the minimum depending on the population abun-
dance and sources of mortalities. Escapements substantially above these minima
will be needed to maintain salmon productivity (and therefore, sustainable ex-
ploitation rates) in many more populations than are presently available. These
increased escapements are also likely to have benefits in expanding the number
of spawning populations, increasing genetic diversity within populations, and
enhancing natural ecological processes.
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296
Management Objectives
UPSTREAM: SALMON AND SOCIETY IN THE PACIFIC NORTHWEST
The major change in objectives related to the sustainability of salmon must
be to broaden the set of biological objectives. That does not imply a priority of
biological objectives over socioeconomic objectives, but socioeconomic objec-
tives should complement biological objectives. The committee concludes that
the resource base necessary to sustain salmon production consists of genetic
diversity (both within and between natural breeding populations) and the habitat
used by all life stages of the species. Genetic diversity provides for the continu-
ing evolutionary process and is the biological basis of future salmon production.
Therefore, the committee recommends managing for the joint biological objec-
tives of MSE and increased diversity within and between local breeding popula-
tions, which will result in increased production in the long run. Increasing the
size and number of spawning populations will, on average, increase the abun-
dance of salmon. The committee acknowledges that increasing diversity will
require initial reductions in catch because animals must survive to reproduce.
However, catch in future years should increase as salmon production increases,
even though fisheries probably would be managed at lower catch rates to main-
tain the diversity within local breeding populations and promote the development
of interpopulation diversity.
Figure 11-6 shows what is expected in accordance with MSE. Graphs A, B.
and C represent what has occurred commonly in the past. Natural or wild (N) and
hatchery (H) populations have been fished simultaneously, but the hatchery popu-
lation has higher productivity. As total population (N + H) increases, catch often
increases to a maximum (Figure 11-6b), but the catch rate (i.e., the portion of the
available salmon abundance that is caught) may not be sustainable by N. Conse-
quently, the catch of N + H begins to decrease because of the declining produc-
tion from N. Eventually, management responds to conservation concerns for N
and reduces the catch to conserve N. If that situation is visualized over many
natural populations, loss of population diversity can be characterized by Figure
11-6c. Diversity, if measured simply by the existence of spawning populations,
would be maintained for a longer period than the catch (N + H). But under
increased fishing pressures, the less-productive N will begin to be lost. Diversity
would probably stabilize as catch is curtailed to conserve population diversity.
Under a management policy to increase interpopulation diversity and achieve
minimum escapement levels, the expected outcomes would be increased habitat
use by spatially and temporally more diversified salmon populations and an
increased catch achieved at a lower, sustainable rate of fishing (Figure 11-6d).
The potential cost of this plan is an initially decreased catch of N while diversity
is increased. The magnitude of initial loss depends on the specific situation.
A useful analogy of this plan is the idea of salmon runs as a tree. Each stem,
branch, and twig on the tree is a potential home for a local breeding population,
an isolated reproductive group adapted to the conditions of that particular stem,
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297
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OCR for page 298
298
UPSTREAM: SALMON AND SOCIETY IN THE PACIFIC NORTHWEST
branch, or twig. Some salmon climb mighty trees like the Columbia and Sacra-
mento with complex branching. Others climb much smaller, less-complex trees
like coastal streams. Cutting limbs from the dendritic structure of these salmon
trees or placing obstructions on major limbs prevents local breeding populations
from filling out the evolutionary potentials offered. That reduces the genetic
diversity and viability of the salmon population as a whole and reduces habitat
use and the potential production of salmon. A more holistic approach in salmon
management would focus attention on filling out the trees' foliage so that viable
local breeding populations of salmon inhabit as many branches as possible.
How could those joint biological and socioeconomic objectives be imple-
mented in a management plan? The committee has considered only a general
process because details of implementation would involve societal values and
decisions. For example, how quickly diversity increases will be associated with
how much societal change is acceptable or with the array of economic alterna-
tives in a specific area. A possible process would involve the following:
· Identification of natural populations with the quantitative information
needed for a credible population assessment and determination of an MSE and
exploitation rate that, on average, would be allowable at this level of spawning-
population size. Currently there are few of these "assessment" populations, but
the application of a safe escapement level will reduce the risk of misapplication
to other populations and should provide reasonable starting points in the plan
development. Total fishing mortality would initially be limited to the exploita-
tion rates at the MSE.
· Predictions of available abundance to fisheries. The methods might vary
between regions, species, etc., but should account for spawning-population sizes,
environmental variation, and interceptions in fisheries outside the management
zones. Abundance forecasting also might prove to be highly uncertain, but
methods to incorporate in-season information with pre-season estimates (see
Noakes 1989) could be useful in controlling fishing impacts.
· Establishment of survey designs for estimating diversity within local
breeding populations. The essential need is to measure diversity and how it
changes over time. Surveys would be designed to be repeatable annually and to
measure quantitatively the spatial and temporal diversity of local breeding popu-
lations.
· Conduct of annual evaluations involving quantitatively assessed indicator
populations, surveys of the spatial and temporal diversity of local breeding popu-
lations within geographic areas, and fishery dynamics. The indicator populations
would include natural populations on which accurate stock-recruitment data can
be collected and whose dynamics (e.g., freshwater and marine survival rates,
productivity, etc. Esee Holtby and Scrivener 19891) can be studied, natural popu-
lations that are conducive to repeatable annual estimates of spawning escape-
ment, and hatchery populations whose exploitation rates can be determined. Fish
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SALMON-FISHERY MANAGEMENT CONCEPTS
299
ery dynamics are assessed to understand units of effort, relationships between
catch and effort, and effort responses to abundance and ultimately to estimate
catch levels for a fishery.
· Assessment of progress toward the biological objectives and incorpora-
tior~ of what is learned from evaluations into future management plans. Given the
limitations in our knowledge and the inherent variability in the environment, the
committee strongly endorses adaptive management (Walters 1986) to achieve
sustainability for salmon. For example, the response of natural populations to
management changes can be confounded by environmental variability. Experi-
mental designs can be useful in controlling this interaction (see Walters et al.
1988) and in improving detection of changes in diversity over time and under
different management plans or fisheries. The use of adaptive management, how-
ever, emphasizes the reed for effective institutional processes for communication
and participation in the development of longer-term management plans.
Control of Fisheries
Meeting the joint management objectives of achieving the MSE and increas-
ing diversity of local breeding populations diversity will not resolve the mixed-
population fishing problem or settle allocation debates. Without greater control
on fishing impacts, meeting the objectives could even exacerbate these problems.
Furthermore, the sequential alignment of fisheries in the Pacific Northwest, from
ocean mixed-population fisheries to more terminal fisheries involving fewer
populations, -could result in inequitable disruption of fisheries. But sequential
fisheries also present an opportunity to compensate for fishing impacts among
fisheries. Given the complex of fisheries, variations in population size, and the
need for social decisions in establishing a fishing plan, the committee felt that it
was impractical to comment on any specific fishing options. There are only two
general kinds of strategies for meeting the objectives through Dishing controls:
~ Reducing exploitation rates over all populations in a fishery fishery-
oriented strategies.
· Increasing the specificity (in time, area, gear, species, etc.) of a fishery to
avoid or minimize impacts on particular populations population-oriented strat-
eg~es.
There are many ways to implement each kind of strategy.. Fishery strategies can
vary from no fishing through allowing exploitation only in specific fisheries to
reducing exploitation rates in all fisheries. Population strategies can divert fish-
ing effort to another time or area, develop a selective fishery for only marked
animals (i.e., prohibit retention of unmarked fish), or develop selective fishing
gear, such as live traps and fishwheels. Strategies can also be combined to limit
exploitation of some populations while maintaining a fishery on others. For
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UPSTREAM: SALMON AND SOCIETY IN THE PACIFIC NORTHWEST
example, an ocean troll or recreational fishery might be managed at low exploita-
tion rates that are sustainable by most populations. Terminal fisheries could then
be managed to compensate for these ocean-fishery mortalities by either increas-
ing or decreasing further exploitation on a population.
In developing a fishing plan, managers have to balance fishing capacity
(number of vessels, effort, market prices, etc.), availability and quality of biologi-
cal data (on abundance, stock composition, previous fishing impacts, etc.), and
societal agreements (allocation requirements, treaty vs. nontreaty, ocean recre-
ational vs. ocean troll, etc.J. Each balance has problems. In the Northwest, more
people would participate in fisheries if there were more fish. The potential for
additional fishing pressure is an important source of uncertainty in how a fleet
will respond to a particular fishing plan. The quality of biological data varies
among fisheries, but the catch rate is seldom known until after the fishing has
ended for the season. Achievement of allocation agreements is uncertain because
population-specific fishing mortalities often are unknown or a substantial portion
of the allowable catch might be taken in fisheries outside the management region,
e.g., in Canada or southeastern Alaska. The most common problem, though, is
our limited ability to control in-season fishing impacts, especially on a popula-
tion-specific level. In the absence of reliable pre-season predictions of popula-
tion and fishery abundance, fishery managers have developed in-season estima-
tion procedures to monitor abundance and run timing. These procedures normally
compare historical test-fishery catches or catch-per-unit effort from specific fish-
eries, with run-size estimates to develop in-season prediction models. These
models frequently also have large uncertainties due to variation in run timing,
stock compositions, and environmental conditions; or simply due to measure-
ment error in historical data. In summary, the quality of biological data varies
widely between fisheries, and exploitation rates in fisheries are seldom known.
This uncertainty places the objective of increasing genetic diversity at risk and
argues for the continued application of conservative fishing plans, particularly in
the mixed-population ocean fisheries. Fishers should recall, however, that fish-
ing at a lower rate on an increasing population will eventually restore catch
levels.
Developing fishing plans for each of the Pacific Northwest regions will
necessitate consideration of specific resource problems, distribution of fisheries,
and social groups. Choosing a strategy requires establishing priorities and mak-
ing a number of difficult societal choices. But fishing is only one mortality
factor. Fishers can enhance the spawning population by forgoing catch, but
salmon also require habitat for long-term sustainability. The control of fishing as
a means to approach sustainability in salmon will be only as successful as our
ability to address the freshwater-habitat issues. We would also expect greater
support from fishers if they could see a successful return on the spawners in-
vested. Presumably, the same would be true of Canada's participation in the
Pacific Salmon Treaty.
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SALMON-FISHERY MANAGEMENT CONCEPTS
CONCLUSIONS
301
Cumulative effects of fishing activities have contributed to depressed pro-
duction. Fishing must be managed on the basis of total fishing mortalities (catch
plus incidental fishing mortalities) and operate at sustainable exploitation rates.
Even after a population has recovered, managers and users should not expect a
return to historic exploitation levels, because those were based on excessive
fishing rates. The exploitation levels might be achieved again only if population
sizes were rebuilt to their former numbers and survival were good. Large catches
could still result from fishing at low sustainable exploitation rates, but on larger
abundances of salmon.
Representative terms from entire chapter:
pacific salmon
