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The U.S. Fish and Wildlife Service has implemented
the National Fish Hatchery program for
over century and annually stocks
over 5 million national fish hatchery
lake trout into the Great Lakes.
But what happens to hatchery fish
after they are released into the wild?
Where do they go?
How long do they survive?
To answer these questions and more,
the U.S. Fish and Wildlife Service is
implementing the Mass Marking Program.
On a quiet morning at Jordan River National Fish Hatchery
in northern Michigan an unassuming white trailer
sits under a blue August sky.
From the outside there are only a few clues
that something extraordinary is taking place.
Inside thousands of lake trout
are being coded-wire-tagged
and fin-clipped at a rapid pace.
Once done entirely by hand,
the sophisticated computers and finely tuned machinery
have a throughput of between 6 and 7 thousand fish an hour.
Juvenile lake trout begin their journey
in the mass marking trailer by being sorted
by size into different processing lines.
The computers show each fish being measured and sorted.
Once measured, fish are put into
holding areas where they wait their turn to be tagged and have their adipose fin clipped.
Fish are tagged and clipped one at a time.
To orient the fish nose first,
the machine is designed so that
fish swim into the chambers
where they are clipped and tagged.
A chamber of the machine houses
a clipping mechanism that precisely removes
a small fin found on the back of each lake trout,
known as the adipose fin.
The removal of these fins makes
the fish easily identifiable as hatchery
raised fish if and when they are caught later on in life.
The blue box is the coded wire tag
injector where the wire is cut before it is injected.
The coded-wire-tags are 1.1 mm
lengths of wire injected into the nose
of each juvenile fish that identify
where the fish were raised and tagged.
Six video monitors provide live images
of what is going on in the processing chambers.
Once tagged and clipped,
the juvenile lake trout exit the trailer
via a long tube that deposits them into
a holding area at the hatchery
where they will await their turn
to be loaded onto a boat and released into the wild.
Not all fish are cooperative.
Those that are irregularly sized
or that fail to go through the automated processors
are separated out and have to be tagged and clipped by hand.
The mass marking program is currently
in its infancy, but in the years to come
it will reveal many unanswered questions regarding
the life of fish after they leave the hatcheries.
The mass marking program represents
a paradigm shift in fisheries management
for the Great Lakes.
First of all it allows us to
identify all stocked lake trout
and salmon stocked in the Great Lakes,
and allows us to measure and better
the efficacy of our stocking efforts.
Secondly it brings the Fish and Wildlife Service
directly in a cooperative management setting
with the states and the tribes
in inter-jurisdictional sportfish management, which
is really not where we’ve been before.
It’s new territory for us, and the states and tribes.
It’s a great opportunity for the Service
to provide a higher level of technical assistance
and we are going to learn a lot more about our stocked fish.
It will also start to get a handle on
some of the other predators that are stocked
in the Great Lakes—the Chinook salmon, the Coho salmon, the steelhead.
And what type of interactions they
have on the predator and prey base in the lakes.
That is a huge thing that we really do not understand yet.
All the lake trout, which we have been
doing for the past couple years using
the mass marking technology, we’ll be able to tell
when we catch a lake trout in the wild,
you will be able to tell what hatchery it was raised at,
how old the fish is, what strain it is, where it was stocked,
when it was stocked all from just pulling that tag.
It is important that we document the potential impacts
of climate change on fish stocks in the Great Lakes,
and our mass marking tool may
be the best means we have to do that.
The mass marking program is in part
funded by the Great Lakes Restoration Initiative.
The U.S. Fish and Wildlife Service currently
owns four mass marking trailers,
including the one seen in this video,
two of which were purchased with Great Lakes Restoration Initiative funding.
To learn more, please visit the
U.S. Fish and Wildlife Service’s