300,000 Chinook salmon smolts from Mokelumne River splash into strange, dangerous new world of Delta waters
Cynthia Pierce, of the Department of Fish and Game, steadies a pipe as thousands of fish are loaded into a truck for transportation at the Mokelumne River Hatchery on Tuesday, April 26, 2011.
- Coded-wire tagging program
Putting nearly 2 million Chinook salmon into the Delta over the
course of a week is all well and good, but how do you keep track of
them? The Coded-Wire Tagging program, which East Bay Municipal
Utilities District has participated in since 1990, aims to resolve
The program is based around a small piece of wire inserted into
a salmon’s snout. The wire features a repeated numerical code
printed on all of its sides. Each hatchery has a corresponding
code. The tagging is done several weeks before the fish are
released into the wild. The coded wires come in handy when it comes
time to make population estimates, understand migration patters or
calculate life spans.
“The simplest way to put it is to think of it as a Social
Security number for a fish,” said Braden Buttars, a supervising
fisheries biologist for the California Department of Fish and Game.
“We tag one out of every four fish.”
The wires are smaller than the short side of an office staple,
and are generally hidden in opaque tissue in the salmon. To
retrieve the coded-wires, specialized magnetic detectors are
required. The wires can be extracted from live or dead fish.
Before a coded wire can be injected into a fish, it first must
be sorted by size. To accomplish this job, the hatchery uses a $1.2
million trailer. Cameras, sensors and switches are everywhere
inside the 25-foot long trailer that operates along the same
principle as a spare change sorter.
The fish are pumped into the trailer where high-speed cameras
sort the fish by size. They are then sent to one of several tagging
stations determined by the length of the fish.
Once sorted by size, the Chinooks then are sent single-file
through a tagging device before returning to the raceway. The
mechanism features plastic clips that fit around the fish’s snout.
When the salmon activates the sensor, the coded wire is quickly
attached and the fish’s adipose fin is clipped. Clipping the fin
doesn’t cause the animal any disadvantage in the wild and merely
helps workers quickly identify salmon that have received a tag when
More than 5 million hatchery salmon have been coded and released
at the Mokelumne Hatchery since EBMUD began the program.
— Source: East Bay Municipal Utility District
Posted: Wednesday, April 27, 2011 12:00 am
Updated: 11:21 am, Fri Apr 29, 2011.
It was nearly noon. The time had come.
They’d been swimming around in a giant stainless steel tank on
the back of a truck for nearly two hours.
Wednesday, April 27, 2011 12:00 am.
Updated: 11:21 am.