Transcript
Introduction
an
ecosystem it's a community of plants and
animals
but what we see at the surface is only
part of the picture
in an ecosystem everything is related
and those relationships have evolved
over thousands
even millions of years
we use the resources of ecosystems
we need the resources they provide and
so we
are also linked to the organisms that
call these natural places
home over time
some members of the ecosystem disappear
and new ones come in
these are changes that have taken place
at nature's pace
the system had time to adjust to the
loss and the gain of new species
that is until we started looking at
ecosystems with an
eye for change and began introducing
organisms into waterways
beyond their natural range
introducing aquatic organisms into new
areas
is a widespread phenomenon that takes
many forms
while some species are shipped from
distant places
others are carried to a nearby drainage
some are introduced for economic reasons
some for recreational pursuits and some
are the unintended result of our
activities
but no matter what the method the
distance or the purpose
a species that gets into a waterway as a
result of human activities
is a non-native species an aquatic
Carp
introduction
the chinese first introduced aquatic
animals
about 3000 years ago they domesticated
the carp
and began placing them into rivers
throughout the country
by the middle ages asian carp had been
introduced in europe
first in monastery ponds where the fish
became a food source from monks who
didn't eat red meat
and eventually into natural waters
throughout the continent
across the atlantic it was barely 100
years after columbus arrived
that the first foreign fish were
introduced to the new world
goldfish a relative of the asian carp
were planted into north american waters
in the mid-1600s
the first large-scale aquatic
introduction to north america came in
1872
again it was the cop brought from
germany to northern california by a
businessman with a dream
julius pope was an entrepreneur who
hoped to raise carp and sell them across
the country
he was sure americans would come to love
carp as the europeans did
only five of his fish survived the trip
but that was all it took
carp are hardy and these five were ready
to breed
and breed they did in no time pope began
selling hundreds of his carp to farmers
everywhere
thanks to the railroad and fish
transport cars
carp were soon raised in ponds
throughout the country
but before long spring storms and flash
floods
washed carp out of their ponds and set
them free
in america's rivers and streams they
adapted quickly to the wild
it wasn't long before they could be
found in almost any suitable body of
water
but in less than 20 years many saw the
carp introductions
as a huge mistake americans didn't take
to their taste
as europeans did anglers complained the
fish were bony and hard to clean
and carp were also unpopular for the
damage they did to natural ecosystems
Feeding
to feed carp suck in a mouthful of mud
insects clams and other invertebrates
found along the bottom of a waterway
they spit out the mixture so the
particles are suspended
and then suck in the food in the process
they stir up silt and mud
making the water cloudy and lowering the
visibility
the habitat becomes less suitable for
other fish who need
clear water to find their prey as the
problems created by
carp became more apparent agencies began
looking at ways to get rid of the fish
in a number of states seining trapping
and even
adding toxins to the system have been
tried with little success
it seems carp are here to stay
Zebra mussels
this practice of taking a species and
planting
it into an area beyond its normal range
continues today
since the lessons learned from the carp
introductions
it's hoped all introductions are well
studied and well
planned but sometimes they're not
sometimes we don't even know we've
introduced an organism
until it becomes a nuisance
probably the most dramatic example of
our time has been the accidental
introduction of the zebra mussel
a small mussel from europe's caspian sea
it most likely arrived here in the
ballast water of a ship
since its discovery in lake saint clair
in the great lakes basin in 1988
its numbers have exploded within a year
colonies of 30 to 40 000 per square
meter
were found in lake erie by 1994
zebra mussels had spread to all of the
great lakes
throughout the mississippi valley and
east to new york's hudson river
and as they've spread zebra mussels have
left a path of serious problems
the little organisms can attach
themselves to any solid surface
including each other in some places
they've been found in layers
8 to 12 inches thick these layers have
clogged
intake pipes of industrial facilities
power plants and municipal water
suppliers
in the short time they've been in this
country their damage has cost
millions the potential ecological
impact of zebra mussels is equally
dramatic
each mussel filters about a quarter of
water a day
feeding on microscopic organisms
organisms that are food
for small fish who are eaten by larger
fish
and eventually humans given their
voracious feeding habits and the
tremendous numbers
zebra mussels have the potential to
alter entire ecosystems
and disrupt aquatic food webs
while the ballast water introductions
are an unintentional result of human
activities
other organisms are introduced into our
waters on purpose
often the reason is simply to add a
species in hopes it'll survive
to produce something that's desirable to
a group of people
however in the zebra mussel example
introduced species
are not isolated from the community of
plants and animals they now
share a home with all
introductions change communities
whether that's bad or good depends upon
our perspective
of the function of those communities it
does bring
change they are different and then the
consequences have to be weighed through
time as to how that new community
can function and what that does to the
previously existing community
Flathead Lake
while we know a community will be
affected by an introduction
it can be difficult to accurately
predict what those changes will be
including any potential negative impacts
flathead lake in northwestern montana is
the largest natural
freshwater lake in the western united
states in 1916
kokanee salmon were introduced for sport
fishing
their numbers increased dramatically
over the years
by the 1950s there were so many fish
spawning on the shoreline
that after they died
after spawning these fish die after
spawning
and there were so many dead carcasses on
the shoreline that they had to be
collected and
carried away in a dump truck in order to
make the areas suitable for for people
to be around
a landlocked form of the red salmon
kokanee
generally lived for three to four years
in the lake and then
spawned either along the shore or up
mcdonald creek
one of the lake's tributary streams as
the salmon population grew
so did the number of anglers flathead
lake became one of the most popular
fishing spots in the west
but the kokanee boom was a phenomenon
destined to change
when another non-native species the tiny
opossum shrimp or mysis shrimp was
introduced into the flathead lake basin
mice's shrimp were introduced into lakes
upstream from flathead lake where
kokanee were also
introduced previously in attempt to
elevate the populations
of the kokanee and make a more viable
fishery for people to harvest
unfortunately water flows downhill and
gradually and
after a period of several years the
misis
showed up in flathead lake and
established a population here
and like most exotic species this
little shrimp became very abundant in
flathead lake in a matter of just a few
years
i think we first found it in the lake
around 1981
or two and by 1984 and five the numbers
were
up to about mices per square meter of
the surface area of the lake
so they just exploded in numbers
meanwhile biologists were counting the
salmon migrating of mcdonald creek
well this is a typical bar for red
salmon to spawn on
in some years more than a hundred
thousand salmon made the trip
the highest number recorded was four
hundred thousand
but in 1987 something went wrong
only 330 salmon made it to the creek
that year
the next year only 50. and while anglers
had been taking up to 200 000 kokanee a
year
not a single coconie was caught in 1988
or 89 the flathead lake salmon
population
crashed and it hasn't come back despite
restocking efforts
Two Problems
university of montana researchers found
two problems
in this complicated situation first of
all
kokanee and mysis were not at the same
place
at the same time how can you live in the
upper layers of the water column of this
big deep
lake they don't go into the deep layers
because it's too cold for them the mices
on the other hand are adapted
to living in the deep layer
i have a layer of mysis right here
they were about 68 meters misis
do come up to the surface to feed but
only at night
and they return to the lake bottom
during the day
but kokanee only feed during the day so
when it came time for the salmon to eat
the mices
weren't there a second problem was in
the food supply
coconi eat zooplankton tiny organisms
that drift in currents
and so do mices that gave the mices a
distinct competitive advantage because
they could feed on the
on the zooplankton very effectively
their population grew
to large numbers very quickly and almost
before we
knew it they had eaten the entire food
supply
of the kokanee salmon the effects of the
shrimp introduction were felt throughout
the ecosystem
flathead lake and its tributaries had
become a gathering place for
a variety of animals who had one thing
in common
they ate salmon bald eagles were among
the most prominent
hundreds gathered along mcdonald creek
to eat dead and dying salmon
but when the kokanee population
collapsed the animals who had come to
depend on salmon as a source of protein
either disappeared or declined
dramatically
Biological Control
most introductions are made with the
best of intentions
most are based on perceived social or
economic needs of the day
and sometimes well-planned and well-run
introductions can make a positive
difference
some of the benefits include an
increased food supply
recreation and pest control
but in some cases the needs of the past
aren't necessarily the needs of the
present or the future
and what we're learning is that while
the intentions of past introductions
were well-meaning
non-native organisms can create
unforeseen
complications in natural ecosystems
in one type of introduction a species is
added to a community in the hopes that
it'll control or eliminate an
undesirable species it's a type of
introduction called biological control
for example mosquito fish are used as a
biological control species
in rice fields where mosquitoes can be a
serious health problem
mosquito fish are not a pure all it's
not a panacea
it's an effective tool and if used
properly
it can be a very effective biological
controller mosquitoes
but like all introduced species we have
to be very careful
and very concerned that we use it in the
right way
in the desert southwest mosquito fish
introductions
have threatened the native species along
the colorado river the gila top minnow
flourished until
mosquito fish were introduced the top
minnow population is now
on the brink of extinction one reason
for the decline
mosquito fish eat young top minnows
in some areas top minnows have
disappeared within two years of a
mosquito fish introduction
it's a similar story in arizona mosquito
fish are one of the several species that
have been introduced into desert pupfish
habitats
since these introductions the number of
pup fishes
has rapidly declined ironically
some of the species mosquito fish are
helping to eliminate
also eat mosquito larvae both gila top
minnows and desert pup fishes if left
alone
are quite effective at mosquito control
in their natural habitats
another reason for introducing species
beyond their natural range
is to develop or improve a fishery
either the game species themselves
or bait for game species
today anglers may try their luck on bass
crappie catfish and many others hundreds
of miles from their native streams
in fact more than one quarter of all the
freshwater fish caught by anglers in the
united states
are not native but what are the effects
of these introductions on the receiving
ecosystems
introduced species interact with natives
in a number of ways
and introduce species may breed with a
related native species
apache trout were abundant in the
streams of arizona's white mountains
but when introduced rainbow trout bred
with the native apache trout the native
population plummeted
hybridization can affect the fitness of
the native species
it has a more difficult time coping with
environmental stresses
in the case of the apache trout where
once they occupied
600 miles of streams today they can be
found on only 30 miles
Fish
california's state fish the golden trout
nearly disappeared when brown trout made
their way into the kern river system
the golden trout couldn't compete with
the larger browns
and they were easy prey for the newcomer
largemouth bass are another predatory
game fish that can
impact a native species largemouth bass
are native to the mississippi river
drainage and the southeast
but they've been stocked outside their
native range for sport fishing
more than any species except perhaps the
rainbow trout
bass are a great fighting fish and fun
to catch
but that aggressive instinct means
trouble for native organisms
that haven't evolved to deal with this
newcomer
bass are good predators and competitors
and their introductions have been linked
to the decline of many fish
now listed as threatened or endangered
historically fishery managers have given
people what they wanted they've stocked
and restocked ecosystems with the
desired species
but success has often led to increased
expectations for more and more fish
yet today we understand that some of
these introductions
have led to a decline and in some cases
even a complete loss of a native species
and the loss of even a single species
can make a difference
it's important to have many different
life forms
not only for the multitude of functions
that they provide
but also for the functions that they
provide that we aren't aware of
we don't know everything about our world
and we don't know everything that these
species provide for us
and actually there are probably
organisms in the environment
that are vital to our very existence
we know that natural ecosystems support
human life
by providing purified air fresh water
soil production
waste disposal a supply of nutrients and
energy
and the high quality of our atmosphere
so while it may be tempting to add our
favorite game species to waterways
everywhere
we don't have a clear understanding of
how our actions will change
ecosystems that all living organisms
including humans depend upon
Escapees
direct introductions aren't the only way
non-native species enter our waterways
some organisms find their way by
escaping from holding ponds or
aquaculture facilities
one escape route is to ride on the crest
of a storm or flood
as we saw very plainly from hurricane
andrew
and from the recent mississippi river
floods that things don't always stay
where you
think they're going to stay or where you
want them to stay
some species escape by swimming through
unscreened pipes in aquaculture
facilities
or during transport and sometimes
they've been mixed up with other species
being removed from a pond
tilapia for example are native to africa
and parts of the middle east they were
originally introduced into north america
as aquarium pets
today the tasty fish are grown
commercially for food
but tilapia have escaped from holding
facilities and entered natural waters
many times
in warm water states like california
arizona florida and texas
escapees have successfully adapted to
the wild
some tilapia species are very aggressive
and compete with native fish for
spawning sites in space
they may dig holes to spawn and in the
process
uproot plants and increase the silt in
the river
which can destroy the nests of other
fish and lower the visibility
adding to all this certain tilapia
species can breed
every month and because the parents
guard them
the young have a high chance of survival
resulting in explosive populations
many aquaculture facilities are careful
and follow precautions
to prevent species from escaping and
entering adjacent waterways
if all the facilities use the same care
the problem of species
entering natural ecosystems as escapees
could be virtually eliminated
Nonnative Species
often established non-native species are
organisms
imported for the aquarium trade some
have been released by home aquarium
owners
just dump that fish although people's
intentions may have been good when they
release their pets
these introductions haven't been without
their adverse effects
goldfish for example have been found in
the waterways of nearly every state in
the union
but the pretty little fish can revert to
their wild state
and develop feracious appetites feeding
mostly on aquatic plants
goldfish can remove significant amounts
of vegetation
they increase turbidity and contribute
to the decline of invertebrates
living in a community introduced plants
can also pose problems hydrilla is an
aquarium plant that was apparently
introduced in florida
presumably by individuals cleaning out
their home aquariums
native to asia hydrilla flourishes in
the wild
once established hydrilla grows quickly
the plant has taken over 90 percent of
this florida lake
and covers large areas of other lakes in
the region
it clogs waterways and has become a
nuisance to navigation
since its introduction hydrilla has
spread throughout the southeast
and beyond to california iowa and
virginia
the reason why exotic species
take off and explode it's because
they come over without the system
that provides the natural checks and
balances on the population growth
in other words these species have
adapted
to predators competitors
and diseases in another ecosystem
and whether transferred to a new one the
rules of the game
are different as a matter of fact it may
be
that the new ecosystem doesn't have a
way
to check its population growth
and when that happens the aliens become
pests
Bait Release
bait bucket introductions are another
way individuals have transplanted fish
into america's waterways
toss this bait let's throw it over sure
an end of the day bait release is
presumably how red shiners
showed up in nevada's lake mead the red
shiner is a popular bait fish native to
the northeast
but sold as live bait in some areas of
the west
once in the lake the red shiners
traveled up into the virgin river
and with the shiner came a parasite
the asian tapeworm found its way to
north america
when asian grass carp were introduced
and while shiners have been able to
adapt to the effects of the tapeworm
the native species in the virgin river
have not
the wound finn minnow in particular is
now an endangered species
partly because it's not able to deal
with the effects of the asian tapeworm
Fat Head Minnow
at klamath lake in southern oregon
oregon state university researchers are
monitoring another bait species
the fat head minnow the fat egg minnows
are a species of the family cyprina day
which are native to the eastern and
midwest states
of the united states and they have been
brought out west
as people moved out west either as uh
for use in fishing as bait fish
or to uh feed the fish like largemouth
bass and crappies that they've brought
out to raise themselves
from the midwest they were first
captured in oregon in the late 70s in
the klamath river
south of the city of klamath falls and
they were first collected in 1982
here in upper klamath lake by oregon
department of fish and wildlife
uh since 1982 they have become the most
abundant fish in upper klamath lake
not only are the number of minnows
increasing they're also spreading to
other waterways
leaving researchers wondering what the
effect will be on two
native suckers i'm seeing a lot of
larval suckers
some laboratory experiments by some
local biologists have indicated that
at least under laboratory conditions the
fat head minnows
will attack and kill and eat larval
suckers whether that happens in the wild
we don't know the answer to that yet but
one thing seems clear
once an introduced species establishes a
successful breeding population in a new
ecosystem
there's almost no way to get rid of it
and as we've seen
introductions often threaten the
cornerstone of an ecosystem
biodiversity it's like the analogy of
the watchmaker
and the person that tinkers with the
watch if you lose
parts of the watch the watch won't work
anymore
and with the ecosystem it's the same way
all of the parts are important and for
the whole
ecosystem to function it needs all of
its parts
the story of aquatic introductions isn't
simple
there are benefits there are costs
and there are impacts that we don't yet
understand
the aim in aquatic management is not to
try and return to the pristine
environments that existed 500 years ago
we cannot undo past mistakes but by
carefully researching proposed
introductions
we can better understand the system and
the species we want to introduce
we can evaluate potential impacts and
benefits of the introduction
both short and long term only then
can we make informed decisions about
non-native species
to learn more about this topic and other
osu extension resources visit the web at
extension.oregonstate.edu
tv
you
This video reveals how the introduction of non-native organisms—fish, shellfish, and even aquarium plants—has affected native organisms in and around our waterways.
Want to learn more about this topic? Explore more resources from OSU Extension:
Fish and aquatic life, Riparian areas
