8
in other words
march5
2020
A Word From the Watershed:
The Weird and Wonderful Pacific Lamprey
By Corrie Aiuto
Pacific Lamprey are amazing
animals. An eel-like, boneless, parasitic
fish, they are resilient, older than the
dinosaurs, and have a fascinating life
cycle. They also live in our watershed.
In January the Upper Nehalem Water-
shed Council (UNWC) was happy to
host Christina Wang of the U.S. Fish and
Wildlife Service at the Vernonia Public
Library to speak about Pacific
Lamprey. We at the UNWC
can’t stop talking about her
presentation or these crazy
fish.
There are approxi-
mately 40 species of lamprey
around the world. Four species
are native to our watershed: Pa-
cific Lamprey, Western River
Lamprey, Western Brook Lam-
prey, and Pacific Brook Lamprey. Some
species are anadromous, meaning they
return to fresh water to spawn like salm-
on, and some spend their whole lives in
fresh water. The Western Brook and Pa-
cific Brook are an example of resident
fresh water lamprey. The infamously
invasive sea lamprey, which decimated
trout populations in the Great Lakes, is
thankfully not found in our rivers.
Lamprey, though they look like
eels, are actually fish. They have no
scales, and are boneless, having carti-
lage instead. They have no paired fins on
their sides (as goldfish do), only dorsal
fins and a caudal fin. They have holes for
gills, blue eyes, and depending on spe-
cies they can be 4-33 inches in length.
of their tail.
Lamprey biology is ancient.
Fossils dating 360 million years old
show a recognizable lamprey, its body
and form essentially unchanged, and
they are estimated to have emerged 450
million years ago. That makes lamprey
hundreds of millions of years older than
the dinosaurs, sturgeon, salmon, and hu-
mans. Their survival strategies are so
They are also jawless, having a power-
ful suction cup mouth with teeth used
for feeding, anchoring, and climbing.
Lamprey cannot jump and have no swim
bladder, so they must constantly swim or
use their mouths to anchor themselves.
They also use their mouths to climb over
waterfalls, attaching to a rock, and then
propelling forward with a quick stroke
successful that they lived through at least
four mass extinction events on Earth.
The life cycle of Pacific Lam-
prey is one of many transformations and
long journeys. Their range spans the up-
per Pacific Rim from Mexico to Japan.
When it is time to spawn, adult
lamprey migrate upstream to build nests,
or redds, in habitat similar to what salm-
on prefer, with gravel bottoms and slower
currents. However, rather than returning
to native streams to spawn as salmon do,
lamprey follow the pheromone signals
of live baby lamprey in the larva stage,
called ammocoetes. Because of this, an
Oregon lamprey can eventually spawn
in Russian freshwater, following the
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scent signals of existing larva. Spawning
usually occurs between March and July,
depending on how far they must travel.
Both males and females build the nests,
using their powerful sucking mouths
to move rocks into a circular shape for
the eggs. Spawning males also use their
mouths to hold the female while mating
and can mate with multiple females in
a single spawning event. Female Pa-
cific Lamprey are especially
productive and can lay up to
250,000 eggs. After spawning,
the adults die within 3-36 days.
The eggs hatch in about
three weeks. The tiny ammo-
coetes drift downstream until
they find a low flow area with
loose silt and gravel where
they burrow down beneath the
surface. They look and behave
much like earthworms; sightless, tooth-
less, they grow to be 8 inches long.
They filter feed, pushing their mouths
up above the silt to catch passing par-
ticles and help mix oxygen and nutrients
into the silt. There they stay, hiding in
the streambed, for anywhere from 2-10
years.
Juvenile lamprey, also called
macropthalmia, stop feeding, grow eyes
and teeth, develop their suction mouths,
and the ability to swim freely. They turn
silver and, between July and November,
begin their outward migration to the
ocean. During this journey they can feed
parasitically, preying on larger fish.
When they reach the sea, lam-
prey quickly swim away from shore, and
have been found at depths over 4,800
feet where they feed and survive as para-
sites. They prey on pollock, hake, salm-
on, flatfish, rockfish, and many others.
Much of their life and behavior during
this time is unknown. Some adults return
to fresh water to spawn as quickly as 6
months, while others stay at sea for over
10 years.
Adult lamprey are preyed upon
by sharks, sea lions, birds, and many
other marine mammals. They are calo-
rie dense, which means they are an im-
portant food source for many predators
and their presence brings some relief to
salmon and other fish listed under the
Endangered Species Act.
When lamprey at sea begin
their migration to freshwater, they un-
dergo one final transformation. Return-
ing to fresh water streams in the spring
continued on page 9
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