Download Invasive Species of the Susquehanna Basin

SUSQUEHANNA RIVER BASIN REPORT
Submitted by John Seitz
Basin Director, PA-AWRA, Susquehanna Basin
Invasive Species of the Susquehanna Basin
Invasive species are plants and animals that have been
introduced to an ecosystem and cause economic,
environmental, and health problems. The problem of
invasive species is not unique to the Susquehanna Basin,
but it is important to understand that a plant or animal
may be native to one Pennsylvania watershed, but be
invasive in the Susquehanna Basin.
One of the problems with understanding invasive
species is determining the impacts resulting from their
introduction. Much time and research is often required
to understand the consequences of the introduced
invasive species. In order to properly manage an invasive
species, important environmental, economic, and
social questions need to be answered. According to
biologist Geoffrey Smith of the Pennsylvania Fish &
Boat Commission (PFBC), many invasive species are
causing multiple issues in the Susquehanna Basin, but
several specific species hold a higher priority concerning
a management strategy at the present time. A few
invasive species of concern in the Susquehanna Basin are
described below.
Rusty Crayfish
predation, the rusty crayfish will displace entire
populations of native crayfish. According to Smith,
the rusty crayfish has essentially extirpated the native
crayfish from the main stem Susquehanna and many of
its warm water tributaries.
Very difficult to control once introduced, the most
efficient management technique to control rusty
crayfish populations is to prevent their introduction.
Almost all invasive crayfish introductions result from
actions of humans, such as emptying bait containers or
pet aquariums. Educating people on identification of
crayfish species, methods and ramifications of spreading
non-native crayfish, and techniques to be used to
prevent/reduce the spread of rusty crayfish are critical to
the management plan to control this invasive species.
Flathead Catfish
Flathead catfish is a species that is native to some
Pennsylvania river systems, but invasive in others,
including the Susquehanna Basin. Named after its broad
flat head, flatheads have
a distinctive lower jaw
that projects out past its
upper jaw. It grows larger
than the Susquehanna’s
native catfish. Differing
from most catfish
species, the flathead
is not a scavenger and
preys primarily on live
fish. According to the
Susquehanna River Basin
Commission (SRBC),
Flathead catfish were first
found to be reproducing
in the lower and central
Susquehanna River in
Photo: Casey Swecker - Marshall University
2005.
Rusty crayfish are an
aggressive species that
grow very rapidly,
thereby greatly
reducing the amount
of time this species
is most susceptible
to fish predation.
Occurring at very high
densities compared
to native crayfish, the
rusty is an efficient
omnivore. Rusty
crayfish eat aquatic
vegetation, benthic
macroinvertebrates,
detritus, and fish eggs, potentially resulting in lower
fish productivity. Through direct competition and
10 | | InInthe
8
theFlow
Flow- -Winter
Spring/Summer
2012 - Spring
2012
2013
PFBC’s Smith notes that flatheads appear to grow
much faster in the Susquehanna River Basin when
compared to growth rates in those basins where the
flathead is native. In the Ohio River, a fish the size it
would take 20 years to attain may reach that same size
in the Susquehanna within10 years. Management of
this species must take into account any detrimental
impacts to the natural balance of the Susquehanna, but
must also weigh an important social aspect, increased
angling opportunities the flathead presents. Although
it appears that the flathead catfish is “here to stay” in
the Susquehanna Basin, any management plan for this
aquatic predator must consider its detrimental impacts
to the ecosystem, as well as, the positive recreational
impacts.
It is unlawful to possess, introduce, transport or sell
Asian carp in Pennsylvania. According to the PFBC,
the only way these fish would occur is if transported
and released. Asian carp are a threat due to their large
size, reproductive success, habitat damage and large,
year-round food consumption. They can constitute up
to 90% of the biomass in infested waters, wiping out
native fish and mussel populations. Also, certain species
of Asian carp, when startled, jump out of the water
causing safety issues for boaters and skiers.
Hemlock
Wooly
Adelgid
The hemlock
wooly adelgid
is an invasive
insect that lacks
natural enemies
in the Basin.
Photo: U.S. Forest Service
An example of
a terrestrial invasive having detrimental impacts on
aquatic resources, this insect uses the eastern hemlock
tree as its host, sucking sap from its branches and often
causing death of the tree within a few years. Smith
explains that the loss of the eastern hemlock could be
concerning because most of Pennsylvania’s brook trout
streams are located in heavily forested drainages, where
hemlock trees protect streambanks and shade the water.
Brook trout need clean cold water to survive and such
conditions depend heavily on the adjacent hemlocks.
As the hemlock wooly adelgid threatens the eastern
hemlock, so too it threatens the brook trout.
Management of Invasive Species
Andar Rehm, 2010 (caught at York Haven)
Once introduced, invasive species can be next
to impossible to eliminate. Many times, the best
management technique is to prevent introduction
and/or spreading of unwanted species. Education and
awareness may well be the most effective means of
keeping invasive species in check.
Asian Carp
Selected Resources
This aquatic invasive species is not yet found in
Pennsylvania, but due to the devastating impact it
has had in the Mississippi River and the threat it now
poses to the Great Lakes, heightened efforts to prevent
introduction to Pennsylvania waters are necessary.
PFBC: Clean Your Gear - http://fishandboat.com/
cleanyourgear.htm.
SRBC: Invasive Species TIP Sheet; How You Can
Help - http://www.srbc.net/anniversary/assets/pdf/
Invasive%20Species%20Tip%20Sheet.pdf.
In the Flow - Winter 2012 - Spring 2013 | 9