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Beach Seine_ lotic environment_ non-wadeable - Nonindigenous by xiaopangnv


									Beach Seine -- Lotic Environment, Non-wadeable                      ver 2. 7-1-04
Contributing Author(s): Richard Bailey

Background and Objectives
The earliest form of seining was drag netting, or beach seining, which was introduced
about 1900. Seining is a fishing technique that is traditionally done in areas where there
are large schools or groups of fish. In the early years seine nets were set from large
rowboats where the fishermen would use beach seines to catch salmon. They would haul
the nets in by hand, either rowing their boats to the fishing grounds or hitching a tow
from a steam-powered cannery tender. The typical seine net has weights on the bottom
and buoys on the top to keep it afloat. These weights and floats enable the net to remain
vertical when pulled through the water to entrap fish. The net is set to encircle a school of
fish, and is then closed off to trap them.
Today, seines can be employed in non-wadeable systems by drift boat or powered boats
to capture both juvenile and adult salmonids in a variety of habitat types. Hayes et al.
(1996) describes generic applications of beach seining for fish capture. Specific beach
seine applications include capturing fish to estimate abundance, determine diversity of
fish assemblages and fish distribution (Farwell et al., Allan et al, Rawding and Hillson,
2002), broodstock capture, and collection of biosamples. Abundance estimates can be
refined by the use of tagging and a mark-recapture approach. Fish that are tagged on the
first catch effort, and recaptured on the second catch effort can indicate the percentage of
the total population that is captured by any single catch effort. Beach seines are also used
to capture juvenile fishes across a wide variety of habitats including rivers, estuarine, and
nearshore habitats.
Beach seining is an efficient method to capture salmonids and non-salmonid fishes in a
wide variety of habitats. It permits sampling relatively large areas in short periods of
time, and capture of fish without significant stress or harm. Selective capture and
subsequent release are possible with beach seines. It is the preferred method of capture to
provide fish for mark-application for many mark-recapture based salmon assessments.
This method is also most frequently used for sampling juvenile salmon in nearshore and
estuary habitats.
Determination of specific study objectives (the questions you want the data to answer) is
critical to developing an appropriate monitoring program using beach seining. Objectives
may range from sampling the fish diversity within a given habitat (low precision
requirements) to being able to estimate population abundance with high accuracy and
precision. The specific study question will also determine what size of fish are the target
and what habitats will be sampled. These elements (fish size and sample habitat
conditions) drive the selection of mesh size for a beach seine, as well as the best set
technique to use.

Table 1. The range of mesh sizes appropriate for various salmonid fork-lengths
Table 2. Set techniques used for various habitat conditions and target species.
Description of Set techniques
Can techniques be tied to specific objectives? (one is better for abundance than
How do we determine the net efficiency? What is the best calibration method?

   I. Sampling Design
                                         Site selection
Seining may be carried out in a variety of habitat types, within the area of residence of
the fish, depending on the population and life stage being targeted. Adult salmonids are
seined from pool (holding) habitats adjacent to and on the migratory routes to spawning
grounds. Juvenile salmon can be fished in stream habitats, estuarine habitats, or
nearshore areas. Sites with irregular bottom topography, significant accumulations of
debris or larger rocks may be problematic. Current velocity and depth influence site
selection and choice of net design. Faster current generally requires a larger mesh size to
reduce drag; while deeper waters require longer nets to reach from the surface to the
substrate. Sites with firm sloping beaches are favoured.
                                     Sampling frequency
Seining for adult salmon is carried out throughout the return run, such that returning fish
are captured in a manner proportional to their abundance within the river (Farwell et. al,
Harrison ref; Rawding and Hillson, 2002). These fish can be marked to establish the
percent of the target population sampled using a mark-recapture approach. For some
species such as sockeye, this may involve deployment of gear at passage sites below
spawning areas. For other adult salmon species, this may involve fishing at a variety of
pool and glide locations throughout the spawning range (Allan and Bailey, in press).
To determine assemblage diversity or provide fish for biosampling one to many sets may
be employed, either on one day or throughout a longer period. To establish an abundance
estimate, generally more than one set is used to try to establish sampling efficiency.
These sets may occur in a single habitat or a wider range of habitats. Peck et al. (2003)
provide sampling schedules for use of beach seines in habitat assessments associated with
juvenile salmon.
The following assumptions from (Rawding and Hillson 2002) are made if a mark-
recapture approach is used to estimate abundance:
      Equal catchability: every animal in the population whether tagged or untagged has
       the same probability of being caught in the I-th sample (pi) given that it is alive
       and in the population when the sample is taken.
      Handling mortality: every animal caught in the I-th sample has the same
       probability of being tagged and returned to the population
      Tag loss: tagged animals do not lose their marks and all marks are recognized on
      Instantaneous sampling: all samples are instantaneous, i.e. sampling time is
       negligible and each release is made immediately after the sample.

   III. Field / Office Methods
Several steps are needed prior to the sampling season to ensure a smooth implementation
of a beach seining program.
In order to accomplish these steps, initial questions about the program have to be
answered. The first question is to determine the specific objective of the sampling effort
– what is the question to be answered by this effort. Other issues that drive the set-up
process are: Where do you want to sample?; What are the habitat conditions there (e.g.
lotic vs lentic, fast vs. slow currents, substrate type, beach angle, depth....others?); What
is your target species/lifestage/size range?

Preseason Activities for Beach Seining
         1. Inspection of seining sites, access points, and routes for boat travel where
         2. Choosing appropriate net designs, deployment vessels, and requirements for
            winches or other mechanical aids to recover nets
         3. Inspection of nets to ensure mesh, lines, floats and weights are all secure and
         4. Determination of required crew size
         5. Preparation of data sheets
         6. Preparation of tags to apply (if needed)
         7. Permitting (where required)
         8. Preparation of vessels, including safety equipment

In non-wadeable lotic habitat, seines are typically set from unpowered rafts such as drift
boats, or jet/propeller-driven boats. Seines may be deployed from the stern (forward
travel) or bow (reverse travel) of the vessel; however, where speed is required, setting
from the stern is preferred. For maximum efficiency of setting, a seine table is desirable.
For powered boats when setting from the stern, a centrally mounted tow post equipped
with a quick-release device is desirable, as is a cowling around outboard motors to reduce
the chance of nets tangling (Fig. 1).
Typical net constructions for capture of adult salmon vary between 15 m and 100 m in
length; 3 m to 12 m in depth with lead lines varying between 4lbs and 7lbs per fathom.
Floats are typically installed at 50 cm intervals on the cork lines. Stretched mesh sizes
vary but 5 cm (2”) mesh is commonly employed. Twines used in mesh construction
range in gauge from 48 to 96; 96 being heavy and 48 being light. Twines are frequently
tarred to increase durability.

Need specifications for juvenile fish approach-Kurt Fresh?
Figure 1.  Fisheries and Oceans Canada stock assessment crew and beach seine boat, ready to make a set on the
Lower Shuswap River, October 2001.

Figure 2.    Making a set in a downstream arc.

                                                     Events Sequence
During daily operations, crews arrive at the seining site, and proceed to organize and
sampling equipment, prior to deploying the net. Once equipment is ready, and the crew
is ready to proceed, the net is loaded onto the seine deck.
First, the towline, connecting the upper and lower bridles is attached to the quick release
mechanism on the tow post. If needed, extra lengths of rope may be added to the towline
to facilitate passing the line to the crew on shore, prior to release from the post. Then, the
net is flaked back and forth on the seine table, corks forward and lead line to the rear,
more to the side of the vessel that the line will exit. For downstream sets from river left,
the line should exit on the port side of the vessel; for sets from river right, the line should
be arranged to exit from the starboard side of the vessel. In Figure 1, the crew is
preparing for a set from river left, thus the line is arranged from the port side of the stern.
When the net has been fully stacked, the beach line should be tied off to a solid
attachment point, preferably close to the waterline. Sets are typically made in a
downstream arc, at speeds up to 20 km/hr. The boat operator should attempt to run out of
net just as he or she reaches the beach, closing the set.
Seine sets are made by deploying the net in either a downstream or upstream arc. In
slower moving, deep water, sets may also be made by stretching the net slowly, part way
across the river, and securing it to rope tensioned bank to bank manually. The shoreward
end of the net is secured to the beach, while the net (and boat) beyond the attachment to
the tensioned line then drift downstream until the limit of the net is reached. At this
point, the crew maintain the boat and net in place by use of ropes to each shore. The net
is left in place, and the crew observe as fish swim up into the area sectioned off by the
net. Once sufficient fish have entered the net, the midpoint attachment of the net is
released and the net is drawn manually to shore by crew members.
With all seine sets, lead and cork lines should be withdrawn at equivalent rates until close
to shore. Once the lead line approaches the shore, it should be withdrawn more than the
cork line, until a secure “pond” is formed in the bag of the net and the lead line is on the
beach. Fish may then be allowed to rest within the bag until they are withdrawn for
sampling, tagging, or transport to hatchery for use as broodstock.
Depending on bottom topography and the presence of debris or large rocks, nets may
become trapped during retrieval. Slacking tension on lead lines and use of a gaff hook on
a long pole from a boat is one method of freeing the line. If repeated sets are made
around such obstacles, rebar devices can be assembled and placed over the debris to
facilitate smoother passage of the net (See Figure 3).
Need description for juvenile fish approach- Kurt Fresh?
Figure 3.      Devices built out of rebar to bridge over rocks, boulders, snags, LWD etc to allow beach seining for
capturing adult Chinook salmon in the Green R., Washington in 2000-2002. Welded washers allowed nailing the
devices to wood, otherwise the ends were jammed into the substrate, pointing upstream. The seine would slide over
such devices. Snorkeling was still necessary in some cases to free the net; obviously this is safe only in certain
flows/river sizes. Snorkeling or SCUBA was required in advance to find suitable sites, and install devices (Peter Hahn,

Once all fish have been withdrawn from the net, the net is cleaned of all leaf litter, sticks,
rocks and other debris, checked for damage, and re-loaded onto the seine deck. Damage
to seines can be repaired following instructions in Gebhards (1996 in Murphy and Willis

    IV. Data Handling, Analysis and Reporting

    V.     Personnel Requirements and Training

                                     Roles and Responsibilities
There are a number of crew requirements associated with successful operation.
Depending on the size of seine net being deployed, the force required to recover the net
and method of deployment, the number of crew required to deploy and retrieve the net
will vary between a minimum of four persons up to crew sizes over 10 persons. Further,
where currents are strong, and/or large nets are used, power winches may be used to
assist in net retrieval.
The boat operator is typically the crew supervisor, and is responsible for ensuring that the
net is properly loaded and will deploy freely from the boat. The boat operator is also
responsible for securing the boat at the end of the set and ensuring all applicable safety
regulations are met. An assistant on board the boat is responsible for throwing the tow
line to shore crews as the set is closed, and once the tow line is under control on shore,
releasing it from the tow post. Where sets are made at speed, it is strongly recommended
that boat crews wear swiftwater helmets to prevent head injuries from rapidly moving
cork and lead lines.
Shore crews are responsible for attaching the head end of the net securely to the shore,
and for net retrieval once the set is closed. Shore crews also clean, repair and load the net
with assistance from and under supervision of the boat crew. All personnel assist with
sample processing.

All crew operating in swiftwater environments should have experience in safe swiftwater
operations including safe wading techniques. Boat operators should be experienced in
operating that vessel type in riverine environments. All crew need to physically fit, and
willing to work.
          Swiftwater operations
          Swiftwater boat operations for boat operator
          Wilderness First Aid (all crew)
          Valid medical clearance for field operations

   VI. Operational Requirements

                                Workload and field schedule
          Seining for adult salmon continues throughout the run of salmon past seining
          Seining can be continued all day by making sets at multiple sites or by
           allowing fish to re-enter the seine site prior to making another set.
          Night seining is also possible if conditions are safe to do so. Night seining is
           more frequently used for juvenile salmon.
          Seining activity may be reduced as migrations taper off, and crews re-assigned
           to other activities associated with the study.

                                           Equipment needs
          Vessel suitable for setting seine. Vessel choices are jet-powered riverboats,
           propeller powered riverboats, rafts, and drift boats. Choices are governed by
           the operating environment, size of net and species to be seined. Fish that are
           capable of fleeing rapidly require powered boats.
          Fuel and oil for powered craft
          Beach seines suitable for the operating environment
          Spare ropes
          Net repair equipment
          Dip nets
          Polarized glasses for boat operators
          Waders
          Life jackets
          Rain gear
          Swiftwater operation helmets for boat crews
          Throw bags
          Marking, tagging and sampling supplies (as needed), data sheets, and pencils
          Hydraulic winch (optional)
          Anti snag devices (optional)
          Long handled gaff hook

                                 Budget considerations
          Manpower costs
          Capital costs for boat
          Net acquisitions
          Expendable field equipment (waders etc.)
          Fuel

   VII.    References

Allan, D.C. and R.E. Bailey (in prep.) Estimating the 2000 escapement of Chinook
salmon to the Lower Shuswap River, B.C. Can. Manuscript. Rep. Fish. Aquatic S

B.C. Ministry of Environment, Lands and Parks, 1997. Fish collection methods and
standards, Version 4.0. Prepared by the B.C. Ministry of Environment, Lands and Parks,
Fish Inventory Unit for the Aquatic Ecosystems Task Force, Resources Inventory

Backiel, T. and R.L. Welcomme (editors) 1980. Guidelines for sampling fish in inland
waters. EIFAC Tech. Paper #33.

Farwell, M.K., R. Diewert, L.W. Kalnin, and R.E. Bailey. 1998. Enumeration of the 1995
Harrison River Chinook salmon escapement. Canadian MS. Rep. Fish. Aquatic. Science.

Flotemersch, J.E., and S.M. Cormier. 2001. Comparisons of boating and wading methods
used to assess the status of flowing waters. US EPA, 600/R-00/108, April 2001.
Hayes, D.B., C.P. Ferreri and W.W. Taylor. 1996. Active fish capture methods. Found in
Murphy, B.R. and D. W. Willis, editors. 1996 Fisheries Techniques. (Pp. 193 to 220).

Klemm, D.J., Stober, Q.J., and Lazorchak, J.M., 1993. Fish Field and Laboratory
Methods for Evaluating the Biological Integrity of Surface Waters, Office of Research
and Development, U.S. Environmental Protection Agency, Cincinnati, Ohio, Report

Meador, M.R., et al. 1993. Methods for sampling fish communities as part of the National
Water Quality Assessment Program. USGS open-file report 93-104, 1993.

Moulton, S.R., et al. 2002. Revised protocols for sampling algal, invertebrate, and fish
communities as part of the national Water Quality Assessment Program. USGS open-file
report 02-150, 2002.

Murphy, B.R., and D.W. Willis. 1996. Fisheries Techniques, second edition. American
Fisheries Society.

Nickelson, T.E. 1998. ODFW Coastal Salmonid Population and Habitat Monitoring
Program. Oregon Department of Fish and Wildlife report, 1998.

Peck, D.V., J.M. Lazorchak, and D.J. Klemm (editors). 2003. Environmental Monitoring
and Assessment Program- Surface waters: Western pilot study field operations manual
for wadable streams. EPA, Washington D.C. 2002.

Rawding, D, and T. Hillson. 2002. Population estimates for chum salmon spawning in the
mainstem Columbia River, 2002. BPA report, contract # 200105300.

WSFRB 2003. Monitoring and evaluation strategy for habitat restoration and acquisition
projects. Washington Salmon Recovery Funding Board, Olympia, WA. Draft 5/16/2003.

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