Cyprinus carpio – An Invasive species?
By Dave Votaw
For at least the last
100 years environmental scientists have been concerned about invasive
species in North
America. Ask any
Midwestern fisherman if he knows any invasive species and he’ll probably
list zebra mussels, round gobies, and asian carp without hesitation. Taking
the long view, these are truly invasive species that are going to
dramatically affect warm water ecosystems if left unchecked. And these
three are far from alone, which begs question: what is an invasive species?
Here are three of many
definitions quickly found on the Internet:
Non-native plants and
animal species; plants and animal species that have been introduced to an
area where they do not occur naturally.
Species which, once
established, are difficult to eliminate. They are often exotic, but there
are native invasive species as well.
A species is regarded
as invasive if it has been introduced by human action to a location, area,
or region where it did not previously occur naturally (i.e., is not
native), becomes capable of establishing a breeding population in the new
location without further intervention by humans, and becomes a pest in the
new location, threatening the local biodiversity.
These three definitions
illustrate that the term invasive can be defined simply or more complexly,
and it is not immediately obvious which organisms, in our case fish, are
invasive and which are not.
fishing today may be the most popular form of fishing on the planet. Google
carp fishing and you get 1.3 million hits, and North American fishermen are
just beginning to catch on.
likes to refer to our time as the Bronze Age because of the tremendous
explosion of smallmouth bass across the continent. The next handful of
decades may well come to be known as the Carp Age; they are literally
everywhere in North America – Canada to Mexico, Maine to Hawaii – much to
the delight of a growing number of anglers of every stripe. Wade a
Midwestern creek or river on a regular basis and you will see them, quietly
gliding by your waders, oblivious to your presence until spooked, making the
bass and sunfish you’ve been catching look like fry in comparison to the
carp’s incredible size in even small flows. And every fisherman has an
opinion too: hated trash fish that ruins game fish habitat, or fabulous new
sport fish and table fare.
The introduction of the
common carp (Cyprinus carpio) to North America
is not complicated. The fish’s native range is the Caspian and Aral seas of
eastern Europe and western Russia.
The exploitation and decline of native North American fish stocks had
reached a point by 1870 that the U.S. Government established the U.S.
Commission of Fish and Fisheries to address the problem, particularly in
light of the need to feed the growing population. The Commission selected
the common carp over native fish for replenishing American fish stocks due
to the species ability to reproduce and live in a diverse variety of
habitats; the fish was also considered a delicacy in other parts of the
world. In 1877 the Commission imported common carp from Germany and began
propagating and distributing them as food fish with the assistance of state
fish commissions. The active stocking of common carp, including mirror and
leather carp, continued for approximately 20 years, with the fish often
being released from railroad tank cars at bridge crossings. The U.S.
Commission discontinued stocking in 1897 because common carp had been
distributed to almost every state and territory and were well established.
Efforts to eradicate carp began almost immediately.
carp are most at home in lakes and impoundments, as well as sluggish,
somewhat turbid streams and wetlands. Typical lifespan is approximately 15
to 20 years. Trautman, in Fishes of Ohio, notes that common carp are
most abundant in streams receiving sewage or substantial runoff from
agricultural land, which describes almost every flow in the Midwest.
However, he found them to be rare in clear, cold waters and streams of high
gradient. Common carp are known to eat almost anything, including detritus
from plants, vegetation, plankton, crustaceans, gastropods, and
significantly, fish eggs. Their feeding behavior is active, often
disturbing and uprooting vegetation and sediments and thus increasing
turbidity. The impact of this behavior can be extensive and dramatic; in
addition to adversely affecting the growth of aquatic vegetation, important
to the life cycles of everything from zooplankton and insects to fish and
birds, silt re-suspension can disturb the spawning of native fishes, inhibit
sight feeding species, and decrease photosynthesis. Under these conditions
phytoplankton (algae) populations tend to increase due to the increased
release of nutrients from sediments and the decrease in zooplankton
predation. While the negative impact of common carp on biodiversity and
water clarity has been regularly documented in shallow lakes and ponds,
large and deeper systems seem to be less dramatically affected; also, rivers
and streams appear to have been studied less extensively than lakes and
Carp management and
eradication efforts have been underway in the U.S. for over 100 years, which
gives some immediate insight into their ineffectiveness and the incredible
adaptability of this fish. These efforts have included physical barriers,
harvesting, and rotenone poisoning. State regulated commercial fishing may
hold the greatest potential for controlling common carp populations. In
Australia, concern over expanding common carp populations has led to the
testing of a potential reproduction control plan - the introduction of
“daughterless carp,” one component of Australia’s National Management
Strategy for Carp Control. Daughterless carp, as the name implies, are
genetically manipulated to produce only male offspring despite breeding
normally. With fewer and fewer females produced with each succeeding
generation, a population can become mostly male. The expectation for the
river where this technology will be tested is a sharp reduction in carp
numbers within 20 – 30 years of release. This technology is species
specific and will not affect native fish.
North America, the common carp seems to have been incorporated effectively
and harmoniously into many aquatic ecosystems, particularly rivers and
larger lakes; they have become an integral part of the food web. History
demonstrates that this species is here to stay despite its detractors and
efforts to control or eliminate populations. Is Cyprinus carpio
still an invasive species today? Federal and state government agencies and
conservation groups do continue to list the common carp among invasive
species, and the fish remains disreputable among a majority of anglers.
Fishermen should ask themselves if they’ve ever chased brown trout in the
U.S. If so, they’ve fished for and admired a species that came from Europe
and is not native to North America – an invasive species. The National Park
Service notes that native species can be invasive also. Consider largemouth
Mexico, smallmouth bass in Oregon, walleye pike in South Dakota, northern
pike in Colorado, salmon in the Great Lakes, and so on. These are examples
of enormously popular sport fish enthusiastically pursued in waters outside
their native ranges – invasive species.
It would seem that carp
populations need to be controlled, but may as well be enjoyed as the
amazing, difficult to catch sport fish that they are. If you catch one this
season, keep it, take it home and prepare it with one of the recipes found
on the Web, for example at
www.activeangler.com. Try the recipe for carp tacos there, as well as
other preparations! If you don’t like the fish as food, use it for
fertilizer in your vegetable garden or feed it to the cat. There are plenty
more where that one came from!