SALMONID LIFE-CYCLE MONITORING
DESCRIPTION
Trap adult and juvenile salmonid migrants (all species) in selected index streams.
RESPONSIBLE PARTY
The Salmonid Life-Cycle Monitoring Project of the Western Oregon Fish
Research and Monitoring Program is responsible for this work. This program is
administered by the Northwest Region, and is supervised by Tom Nickelson
[(541) 757-4263 Ext. 223; email: nickelsont@fsl.orst.edu].
Project staff are:
Project Leader: Mario Solazzi [Corvallis, (541) 757-4263 Ext. 242
e-mail: solazzim@ucs.orst.edu]
Assistant Project Leader: Jeff Rodgers [Corvallis, (541) 757-4263 Ext. 231
e-mail: rodgersj@fsl.orst.edu]
Assistant Project Leader: Steve Johnson [Newport, (541) 867-0300 Ext. 238;
e-mail: johnsost@ccmail.orst.edu]
Assistant Project Leader: Bruce Miller [Charleston, (541) 888-5515;
e-mail: ]
Assistant Project Leader: Tim Dalton [Tillamook, (541) 842-2741;
e-mail: ]
QUESTIONS ADDRESSED
 Are there trends in abundance of adult or downstream migrant anadromous
salmonids in selected index streams?
 Are trends in abundance of adult coho salmon in selected index streams
primarily due to changes in freshwater survival or to changes in marine
survival?
 Are there geographic differences in the patterns of freshwater and marine
survival of coho salmon?
 Are trends in freshwater and marine survival of coho salmon in western
Oregon correlated?
 Are geographic patterns of freshwater survival of coho salmon associated
with differences in habitat quality? (Addressed in conjunction with the Aquatic
Inventory Project)
 What are the influences of climate and land-use activities on coho salmon
survival rates?
 How do survival rates of wild and hatchery coho salmon compare?
Addressed in conjunction with the Stock Assessment Project)
 What are the life history characteristics (time, size, and age at juvenile and
adult migration) of the anadromous salmonids in the index streams?
 How accurate are methods of estimating spawning abundance of different
anadromous salmonid species? (Addressed in conjunction with the Coastal
Salmonid Inventory Project)
CONSIDERATIONS
1. Because of life history differences among anadromous salmonid species, the
questions addressed by life-cycle monitoring vary by species. The following
is a species-specific description of the type of information that the program
will provide.
Coho Salmon
Juvenile coho salmon, (at least the large majority of those life history types
that still exist), spend their entire freshwater residence in or near their small
natal streams. If trapping sites are located on large enough streams such
that juvenile rearing occurs primarily above the trap sites, adult and juvenile
migrant trapping will provide information on the freshwater and marine
survival of coho salmon. Marine survival, as we use it here, encompasses
the survival of fish from the time the smolts1 migrate out of the study stream
until the adults return to the stream. Thus, this survival includes migration
through mainstems and estuaries as both smolts and adults. With the
survival information, the trapping program for coho salmon can address the
following question that is critical to evaluating the effectiveness of plan
measures:
Chinook Salmon
In Oregon coastal streams, most fall chinook juveniles migrate out of their
natal stream by the early summer, and continue rearing in the mainstem
rivers and estuaries before migrating to the ocean in late summer and fall.
Because of this life history pattern, the trapping program will not be able to
estimate marine survival rates for chinook salmon. Trapping will provide
estimates of the number presmolt chinook leaving the streams each year. In
addition, information on size of migrants and the timing of the migration will be
collected.
Chum Salmon
Chum salmon may occur in some of the northern index streams. They have
the shortest freshwater life history of any of the anadromous salmonids in
Oregon, with juveniles migrating to the estuary shortly after emergence from
the gravel. Thus, it will be possible to make estimates of marine survival.
Steelhead
Steelhead juveniles may move and rear considerable distances from their
natal streams before they make their seaward migration. Therefore, unless
trapping operations are located near the ocean, no estimate of the total
number of ocean migrating juvenile steelhead produced from a known
number of adult spawners can be obtained. Consequently, in most cases
trapping will not provide information on the marine and freshwater survival of
steelhead. Those sites located in the lower portions of river basins will
1
Coho Smolts are defined as age 1+ spring migrants and in some cases, age 0
coho that are silvery in appearance and have fork length >80mm. in late spring.
provide information on smolt abundance each year. The sampling will also
provide information on the migration timing, and the size and age of the
migrants.
Searun Cutthroat Trout
The freshwater life history of searun cutthroat trout, which is similar to that of
steelhead, presents similar obstacles to using trapping information to estimate
their freshwater and marine survival. In addition, the small size of returning
searun cutthroat trout adults makes them difficult to trap. Most returning
searun cutthroat are small enough to swim through the upper picket fence in
the adult trap. In most cases the spacing of the bars in the picket fence
cannot be reduced to insure the capture of all searun cutthroat because it
would result in the adult trap clogging with debris during high stream flows.
Therefore, in most cases, trapping will only enable monitoring of trends in the
number of downstream juvenile migrant cutthroat trout. Experiments are
currently being conducted with an infrared fish counter that may enable us to
count returning adult searun cutthroat trout without actually capturing them in
a trap.
2. The selection of streams for salmonid life-cycle monitoring is of critical
importance to the success of the program. To provide the most useful and
accurate information, the trapping program must select sites in the most
unbiased way possible. Unfortunately, there are a number of obstacles
preventing the implementation of a totally unbiased trap site selection
process. One obstacle is the reality that not all streams have sites that are
conducive to successful trap operation. For example, streams may either be
too large for traps to accurately estimate migrant numbers, or too small so
that the degree of error associated with the abundance estimates masks any
trends in abundance or survival. Other factors such as bank and substrate
stability, stream gradient, site access, and landowner cooperation also
impairs the unbiased site selection process. Funding realities and the
logistics of maximizing the amount of information obtained in relation to the
dollars spent are another obstacle. For example, on a daily basis, one person
can run two downstream migrant traps successfully during most streamflow
events only if the sites are located within a 30-minute drive or less from each
other. This reality means that in some cases, some sites may be selected or
rejected based on their proximity to another site, rather than on their overall
merit as being the most “representative” of other streams in the area.
All of these obstacles mean that only a limited number of streams will
effectively be a candidate for trapping. Because the number of sites is limited
in relation to the diverse nature of coastal streams, it is impossible to pick a
suite of study streams that “represent” all of the other streams present in each
of the five Gene Conservation Group Areas (GCG Areas).
LOCATIONS
Based upon a preliminary review of potential candidates, many potential streams
have been identified for salmonid life-cycle monitoring). As a first cut, sites for
monitoring both smolts and adults are being established at the following locations
(See attached map):
North Fork Nehalem River
Little Nestucca River
Mill Creek (Siletz River)
Bales Creek (Yaquina River)
Cascade Creek (Alsea River)
West Fork Smith River
North Fork Coquille River
These streams will provide a relatively good latitudinal representation of streams
in four of the five Coho GCG Areas along the Oregon Coast. In addition, smolt
trapping is beginning in two Tillamook Bay tributaries (South Fork Kilchis River
and Little North Fork Wilson River) with the hope that funding can be secured for
adult monitoring. We are also considering other possibilities near the Smith
River and Coquille River sites.
Trapping Site Selection Criteria
1. Good geographic spread of sites coast-wide. Currently, ODFW has partial
funding for field crews to be based in Tillamook, Newport, and Charleston.
Without additional funding, it will be difficult for ODFW to operate traps that
are long distances from these three areas (e.g. South Coast streams).
2. One person can run two traps. Paired sites should not be more than a 30minute drive apart so that trap watcher can cycle between traps during high
streamflows. This is particularly important during smolt trapping. Trapping
sites do not necessarily need to be within 30 minutes of the field crews office
if travel trailers, or some other means of housing can be arranged.
3. Candidate streams should have spawning populations of coho, steelhead,
and cutthroat, and where possible, chinook.
4. To maximize the number of fish sampled, streams should be as large as
trapping technology allows. In practice, this generally means fourth to fifth
order streams that are no wider than approximately 30 meters active channel
width.
5. Existing fish ladders should be used where possible as adult trap sites. This
will reduce construction costs and enable more adult traps to be operated,
improving the geographic range of the monitoring effort.
6. Sites must be of sufficient depth (> 2.5 feet) and of sufficient velocity (> ft/sec)
at low spring stream flows to allow operation of rotating screw smolt trap (or
the site must be amenable to modification to meet these criteria). The site
should also be neither too constrained or high gradient so that the smolt trap
will be damaged due to excessive water turbulence, or be too unconstrained
so that the stream becomes too wide and slow for efficient screw trap
operation during high stream flows.
7. Land owner willingness to allow access to site for long term (> 10 years)
monitoring.
8. Candidate streams without existing fish ladders need to have sites with the
following characteristics to enable the construction of an adult weir:
a) Uniform (preferably bedrock) bottom and stable streambanks.
b) 1-2 percent gradient.
c) Road access (close enough for delivery of materials needed to construct
weir).
PROTOCOLS
Estimating Abundance of Downstream Migrants
1. Trap Design
Downstream-migrating juveniles salmonids are trapped each spring using
either a rotary screw trap or an inclined plane trap. In small streams, a
revolving screen trap identical to that described by McLemore et al. (1989) is
used. These traps consist of a revolving screen suspended between two
pontoons. A 12-volt DC motor turns the screen. Downstream migrants are
swept onto the screen by the stream current and transported to the back end
of the trap with the aid of perforated L-shaped cups that are attached to the
screen at two-foot intervals. Fish reaching the back of the trap are dropped
into a live box where they can later be enumerated. The revolving screen
traps currently in use have either 2 ft or 3 ft wide screens.
In larger streams a floating trap that relies on an archemedes screw built into
a screen covered cone that is suspended between two pontoons is used.
The large end of the cone, (either 5 ft or 8 ft in diameter, depending on the
size of the stream) is placed upstream into the stream current. With the lower
half of the cone in the water, the water pressure forces the cone to turn on a
central shaft, much like a turbine. Downstream migrating fish that enter the
cone are trapped by the rotating screw and forced into a holding box at the
end of the trap.
Neither of these two trap designs is appropriate for all streams or flow
conditions. The type and size of trap used is both a function of the size and
flow characteristics of the stream being sampled, and the size and species of
the fish that are targeted for trapping. In general, the screw trap is more
effective in larger streams because it requires adequate water depth to
accommodate the fixed fishing position of the screw as well as adequate
water velocity to turn the screw. Because of their smaller size and adjustable
screen depth, the revolving screen traps are best suited to smaller streams.
The passive capture design of the screw trap generally means that it is more
effective in catching larger steelhead and cutthroat trout than the revolving
trap because these larger fish are sometimes strong enough to swim off the
revolving screen before being deposited in the trap live box.
Because these traps must operate during high streamflows, there is a risk
that the traps will become jammed with debris and thus not fish the entire time
between trap checks. For the revolving screen traps, a 12-volt clock is
connected to a fuse inline with the trap motor. If the trap is jammed with
debris, the fuse is blown, stopping the clock. By recording the starting and
ending time on the clock, the length of time the trap was fishing before
becoming jammed can be determined. The fuse has the additional benefit of
preventing motor burn out by cutting off power to the motor if the trap
becomes jammed.
For the screw traps, a hubodometer, identical to those used by the trucking
industry is used. The hubodometer is placed on the front spindle of the screw
trap. The hubodometer records the distance that the screw turns between
trap checks. By monitoring the number of revolutions per minute, and
knowing the distance that the screw turned, the length of time the trap fished
before jamming can be estimated.
Predation by larger fish on smaller fish can be a problem in the trap live box.
To minimize this, fir boughs or other hiding cover are often placed in the trap
live box to give smaller fish a place to hide. Fish mortality can also occur in
the screw trap live box during high streamflows. The resulting high water
velocities can push smaller fish to the back of the live box, eventually
exhausting them and leading to mortality. To reduce water velocities in the
screw trap live box, a v-shaped plywood deflector that creates a pocket of
calm water for small fish is sometimes placed in the live box.
2. Site Selection
Regardless of the type of trap used, the selection of the site to place the trap
is critical for successful trapping. The traps should generally be fished near
the head of a pool, just below a section of fast flowing water. Streamflow
should be moving in a straight line as it enters the trap. Pools with sharp
changes in direction that result in large back eddy currents should generally
be avoided. In smaller streams, small boulders, sandbags, or screened weir
panels can be used to improve the hydrodynamics of the site.
Both trap designs require streamflows that with a minimum water velocity to
allow traps to function properly. For revolving screen traps, McLemore et al.
(1989) suggests a minimum water velocity of 0.9 meters/second, with most
efficient operation at 1.5-2.0 meters/second. We have found an optimum
water velocity of 0.8-2.0 meters/second for the screw traps operated in
Oregon coastal streams.
Other considerations important in the site selection process are the
availability of large trees or other suitable anchor sites, and anticipation of
how well the trap will function at different streamflows and how easy it will be
to monitor at high streamflows. Special attention should be given to insuring
that the trap has a safe refuge during extreme high streamflow events.
3. Sampling Duration
Sampling begins by the first week in March and continues until the catch
decreases to low levels, usually by the first of June. Traps generally are
operated 24 hours per day seven days per week and are monitored daily.
4. Trap Efficiency Estimates
Because neither trap samples 100 percent of the water column, only a portion
of the total number of downstream migrants are captured. A variety of
factors, including changing streamflow, changing fish size, behavior, and
species composition can influence the proportion of the total migrant
population that is captured by the trap (trap efficiency). To accurately
estimate the number of downstream migrating juvenile fish, trap efficiency
must be measured on a regular basis. To accomplish this, up to 25 fish of
each age class/species (see data sheet, appendix A) are marked and
released each day. To insure that the fish used for trap efficiency estimates
are migrating fish, they are selected from those fish captured in the trap the
previous night. Because frequently not enough fish are caught in certain
species/size classes to enable an accurate trap efficiency estimate on a daily
basis, a weekly estimate is calculated instead using the following formula:
Ni = (ni) / (mrecapi/mreli)
Where Ni = total number of migrants passing trapping location in week I,
ni = number of unmarked fish caught in trap in week i (Monday-Sunday
trap catches),
mrecapi = number of marked fish recaptured in trap on week i
(Monday-Sunday trap catches)
mreli = number of marked fish released above the trap in week i
(Sunday- Saturday)
The total number of fish migrating past the trap site for the season is then
estimate by:
Ntot =  Ni
The importance of expanding trap counts by appropriate measures of trap
efficiency is illustrated in tables 1 and 2. In the examples shown,
misinterpretation of the data would have resulted if trap efficiency estimates
based on species and size class characteristics had not be used to adjust the
estimate of downstream migrants.
To obtain the most accurate estimate of trap efficiency, marked fish are
released at dusk. This is done for two reasons: 1) most downstream
migrating juvenile salmonids on the Oregon coast migrate at or a few hours
after dusk, and; 2) daytime releases of marked fish at the same spot every
day can lead to increased predation by resident cutthroat trout that establish
feeding stations at the release point. Dusk releases appear to reduce this
predation by reducing the exposure time of marked fish to predators.
Fish marked for efficiency estimates are given adequate time to recover from
handling prior to release. Because the smolt traps are typically checked in
the morning, a timer-activated, self-releasing live box is used that enables
marked fish to recover all day before being released at dusk. This device
consists of three dark-colored five-gallon buckets that are suspended
between two small floating pontoons. A spring wound timer is connected to a
12-volt automobile door lock actuator. At the appropriate time, the timer
energizes the door lock actuator, which pulls a pin releasing the buckets. The
buckets pivot on a pipe inserted through holes in their base, turn upside
down, and release the fish. Each bucket has wire mesh panels along their
sides to allow transport of oxygenated water into them. To avoid predation
problems in the holding buckets, fish are separated by size. Typically fry are
placed in one bucket, coho smolt sized fish in another, and larger trout in a
third bucket. Periodically the fish are examined just prior to release to make
sure that there is no mortality and that the buckets dump at the appropriate
time.
The release location for marked fish for trap efficiency estimates is located far
enough upstream so the fish can evenly mix with unmarked fish moving
downstream, yet not be so far upstream as to cause an extracted period of
migration of marked fish over multiple days. Marked fish are typically
released at least two pool/riffle units, but no more than 300 meters, above the
trap. This is based on our experience and is consistent with the
recommendations of Roper (1995).
5. Fish Handling
Generally all fish handled for marking or length measurements are
anesthetized with MS222. When anesthetizing fish, it is important to
remember that water temperature, anesthetic concentration, and fish density
and size can all increase the stress load on the fish. Care is taken that no
more fish are anesthetized at one time than can be safely processed. During
warm water periods or when large numbers of fish are being processed, the
anesthetic water is regularly changed to keep it cool and well oxygenated.
Several methods of marking fish for trap efficiency estimates are used.
Usually, a small scissors or a razor blade is used to remove a portion of a fin.
When using fin clips, typically the tip of the upper or lower caudal fin is
removed. This technique is the only reliably safe way to mark small fry. For
larger fish, a Panjet needleless injector is typically used to inject a small
amount of colored acrylic paint under the skin.
All newly marked fish are placed in the timer actuated release device, and a
count is made of unmarked and recaptured marked fish. Each week, up to 25
length measurements are made for each species/size class (see data sheet
instructions). Once all recaptured marked fish and unmarked fish are
processed, the unmarked fish are released far enough downstream to
minimize the potential of them swimming back upstream and reentering the
trap.
6. Data Analysis
During the early or late portion of the migration period, only a few fish may be
caught during the week, and no marks may be recovered, making it
impossible to calculate a weekly trap efficiency (note that this is the case for
the first two week and the last week of trapping in Table 3.). To expand trap
catches for these weeks a trap efficiency estimate based on the entire season
is used. While this may not be extremely accurate, the total catches for these
weeks are generally small, and their expanded estimates of migrants
represent a small portion to the total population.
For some streams, the number of migrants of a particular species that are
caught in the trap are not sufficient to obtain a weekly trap efficiency estimate.
This may result from a low number of migrants, a low trap efficiency for this
particular species, or a combination of both. For these fish, a trap efficiency
for the entire season is calculated based on the total number of marks
released and recaptured while the trap was in operation (Table 4). This
seasonal trap efficiency estimate is used to expand the number of fish caught
in the trap during the season to obtain an estimate of total migrants.
This approach may lead to a less accurate estimate, because most marked
fish may be released under different flows than when the majority of marks
are recovered. More importantly, if the total number of marks recovered is
low (say less than 5), the expanded estimate of migrants may change
significantly if the number of marks recovered is changed by even one fish. In
some streams, trap efficiencies and total number of fish caught can be
improved by adding weir panels to force more of the stream flow in front of
the trap.
ADD SECTION ON BOOTSTRAP?
Trapping Adults
Protocols under development.
Estimating Adult Abundance
Protocols under development.
REFERENCES
McLemore, C.E., F.H. Everest, W. R. Humphreys, and M.S. Solazzi. 1989. A
Floating Trap for sampling downstream migrant fishes. Research note PNWRN-490, Pacific Northwest Research Station, United States Forest Service,
Corvallis, Oregon.
Roper, B.B. 1995. Ecology of anadromous salmonids within the Upper South
Umpqua Basin. Doctoral Dissertation. University of Idaho, Moscow, Idaho.