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McDonald Lake Sockeye:
Background:
The
McDonald Lake stock is the
largest “local” sockeye stock in southern
SE Alaska. Over time escapement goals have been generally met or
exceeded with the exception of the past 8 years when the escapement goal has
only been met two times. In some of these years escapement has fallen
significantly below the goal. During the Board of Fish Meeting in
Sitka in 2009
the stock reached the official status of “Stock of
Concern”. While the adult sockeye returning to McDonald Lake pass through
several intensive traditional net fisheries, current shortfall seems most likely
the product of poor natural survival rather than the result of over harvest.
Regardless, the most powerful tool of fishery managers is to constrain harvest.
In order to effectively constrain fisheries so that the goal of rebuilding this
stock is met with minimal restriction on common property harvest, it is
important to know where and when these fish are harvested so that effective time
and area closures can be used to protect this stock.
The location of SSRAA’s
enhancement projects was determined by the local fishermen. If the fisheries
where these enhanced fish are caught are significantly constrained, this action
will have a strong negative impact on the value of local harvest. Likewise, if
the constraints on fisheries are only placed on some of the currently “known”
corridors for McDonald Lake sockeye, these constraints may prove ineffective and
could consequently represent an unfair harvest allocation against one gear
group. It is in the best interests of all parties to restore the McDonald Lake
sockeye stock as quickly as possible; and it is also in the best interest of all
parties to constrain fisheries in an effective and fair fashion related to the
consequences of these actions to existing harvest allocations between gear
groups. In other words, all areas where these fish are harvested must be
identified and each constrained related to its impact on this stock – not just
the primary local fishery historically believed to harvest these fish, unless
that belief proves to be correct.
SSRAA and ADF&G anticipated
this problem in 2007. Encouraged by local harvesters SSRAA made a proposal to
the Northern Fund to place a large number of tagged sockeye in the lake. We
called these fish sentinel fish as their presence, when and where they were
harvested, as returning adults would most probably represent the presence of
naturally produced sockeye in the same harvest. Perhaps even more importantly,
this project will add adults to the annual spawning population at McDonald
Lake.
The goal was to take eggs
from the wild stock for incubation and rearing at Burnett Inlet Hatchery and
then return these fish, 100% thermally tagged, to the lake to outmigrate side by
side with the wild smolt. After extensive experiences with sockeye and coho
presmolt enhancement, we are confident that returning smolt-sized presmolt to
McDonald
Lake
will increase the number of adult sockeye returning to
McDonald
Lake. In addition, if the presmolts are released from pens immediately adjacent
to the primary spawning tributary in McDonald Lake, we are confident that most
of these fish will return to spawn in the desired location.
Project Overview:
We collected eggs from spawning adults in 2007, 2008 and 2009. We intended to collect approximately
450,000 eggs each fall, but poor returns of adults have forced us to take fewer
eggs than intended. The eggs have been successfully incubated in an “isolation
module” at Burnett Inlet Hatchery. All embryos were thermally tagged. The
emergent fry from each brood year (2007 & 2008) were reared for a year at
Burnett and returned to McDonald Lake during the spring as presmolt ready to
migrate to sea in several days. This will be repeated again for a final
transport of presmolt back to McDonald Lake during the spring of 2011.
These yearling smolt are returned to McDonald Lake by aircraft . They are
placed in a net pen near the primary spawning tributary in McDonald Lake for a
short period to influence adult homing. After
holding for several days, they will be released and allowed to feed naturally
for a short time (3 to 5 weeks) and leave the lake with the naturally occurring
smolts.
Adults returning from this
planting, estimated annually between 20,000 and 40,000 fish, will pass through
several significant net fisheries in southern SE Alaska where they will be
harvested in the normal conduct of those fisheries. SSRAA and ADF&G staffs will
collect otoliths from harvested sockeye to identify the thermally tagged fish,
which in turn can be used to identify area of harvest and to some degree time of
harvest. The fish escaping harvest will return to McDonald Lake and add to the
spawning population in the lake. Post spawning collection of dead adults will
be used to estimate the participation of the enhanced fish in the reproduction
of this population.
Summary,
the purpose of the project is to add a significant number of thermally tagged
McDonald Lake sockeye to the adult return to McDonald Lake. This will allow the
fish to be specifically identified in commercial harvest related to harvest gear
and district and to some degree harvest timing. The project will also add a
number of adult sockeye to the spawning population in McDonald Lake. The project
will improve information needed for effective resource management, specifically
to address a current serious problem with the McDonald Lake sockeye stock that
has been labeled a “stock of concern” by the ADF&G. This project will also add
adult McDonald Lake sockeye to the spawning population utilizing a technique
that does not require new hatchery facilities or high operating costs. Existing
facilities and staff will be utilized and very little staff time or equipment is
required at McDonald
Lake.
Photogallery
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1st of eight loads staged on the dock at Burnett Inlet awaiting transport to McDonald Lake.
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Preparing to load the 300 gallon tank in the Dehavilland Turbo Otter.
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Sockeye smolts were loaded into a hopper and then gravity fed into the transport tank on-board the plane.
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Leaving Burnett Inlet, transit time to McDonald Lake 20 minutes.
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Getting airborne at Burnett Inlet.
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The net pen anchored at the mouth of Walker Creek, the main spawning tributary of McDonald Lake.
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Arriving McDonald Lake.
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Crew on-board the flight, also standing by at the lake to assist unloading.
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Gravity feed off-loading at the lake.
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Discharging the smolts from the airplane tank through a 3" hose into net pen.
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After eight roundtrips 280,000 sockeye smolts fill the net pen. The smolts were allowed to acclimate 2 days in pen prior to release in McDonald Lake.
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