Invasive Species: What are they? Crustacea Fishes

The zebra mussel is a freshwater bivalve native to the

Black and Caspian Seas. These mussels, however, are

adapting and becoming salt-tolerant. They first ap-

peared in the Mississippi

River in 1991. They are

one of the most wide-

spread molluscan aquatic

invaders in the United

States, travelling from

the Great Lakes to the

Gulf of Mexico. They are

not very large, averaging

approximately one inch

in total length. Like other mussels and clams, they are

filter-feeders, preying upon plankton and algae. They

feed by pulling water and nutrients through their bod-

ies, “siphoning out” the water, and absorbing the plank-

ton. This species will frequently live in the pipes of

power plants due to the constant source of water and

nutrients. The zebra mussels are able to grow so densly

that they will congest the pipes and restrict water flow.

The zebra mussels are extremely prolific, producing

approximately one million young in a season. The aver-

age lifespan of the zebra mussel is four to five years.

While in their native environment, the zebra mussels

have many predators. However, the introduced zebra

mussels do not have the same predators. Fish species

such as bass and drum have been reported to feast up-

on these mussels in the Gulf of Mexico. Crayfish and

muskrats are also available predators in the Gulf States.

Because the zebra mussels are very adept at “taking-

over” new environments, in many states it is illegal to

be in possession of one of these mussels. It is very im-

portant that all boats and boating equipment be cleaned

and inspected after trailering and dry-docking. Many

states have begun to use chemical controls to eradicate

these mussels.

Zebra Mussels

Dreissena polymorpha

Asian Tiger Prawn

Penaeus monodon

Indo-Pacific Lionfish

Pterios volitans and P. miles

The Asian tiger prawn, also called the black tiger

prawn, is native to the Asian continent, as well as the

Pacific Ocean. There are several theories of how the

prawns were introduced to the Gulf of Mexico. One

theory states that they were brought to the region in the

ballast pumps of ships. Another theory states that they

first originated from a farmer in South Carolina who

allowed his stock to be “put out to sea.” Their numbers

in the Gulf of Mexico have increased dramatically within

the past few years. There were six reported captures of

tiger prawns in 2006; howev-

er, there were more than 200

reported in 2011. Asian tiger

prawns reach lengths of over

one foot and weigh approxi-

mately one pound each. They

are easily identified by their

black color with white stripes.

The tiger prawn will take

every advantage to feast upon

other crustaceans. These tiger

prawns are extremely prolific.

A single female may produce

“up to” one million eggs in a season and these eggs typi-

cally hatch within 24 hours. These introduced prawns

frequently carry diseases that affect native white and

brown shrimp. Tiger prawns are considered edible and

marine regulating agencies are encouraging human

consumption. However, many marine resource depart-

ments are trying to collect small amounts of tissue sam-

ples from these prawns. Tissue analysis can help differ-

entiate whether they are reproducing in the Gulf of Mex-

ico or being imported into the area. Once their capture

is reported, enjoy these delicious shrimp!

nola.com

An invasive species is considered a non-native organism

in an area where it is introduced. These species can cause

devastation to the introduction area, environmentally eco-

nomically, or both. An invasive species may be either ter-

restrial or aquatic;

plant, animal, or

micro-organism. It

is estimated that

aquatic invasive

species cost the

United States (and

its territories) 140

billion dollars a

year. There are

primarily two methods of introduc-

tion: accidental and intentional. An accidental introduction

is one caused by a natural disaster or moving an organism

without one’s knowledge. Intentional introduction is the

known releasing of organisms in a non-native environ-

ment. This often occurs with very little thought to its po-

tential effects. Any species considered “invasive” must be

capable of quickly reproducing, able to maintain a popula-

tion, and able to establish a place among native organisms.

In many cases, this means displacing the native organisms

which cause competition. The problem with non-

indigenous (invasive) aquatic species is they often “out

compete” native

animals for food

and/or space.

Many invasive

species have no

natural preda-

tors in their in-

troduced ranges.

sites.duke.edu

Zebrafish, firefish, butterfly cod…call them what you like,

but a lionfish is a fish best observed and not handled!

These fish are found predominately throughout the Indian

and Pacific Oceans. They are usually distinguished by

their maroon stripes overlaying a light colored body. Li-

onfish have several

means of catching

their prey. Tentacles

above the eyes and

under the mouth and

fanned pectoral fins

help to lure and

“corral” their prey.

Lionfish possess

several sets of venomous

spines on their dorsal and anal fins, which are utilized for

protection as well as hunting. This neurotoxic venom is

not usually fatal to humans; however, allergic reactions

can occur. As an invasive species, lionfish are voracious

predators, consuming nearly everything in their path.

They have been the most devastating on small reef fishes.

The warm Gulf waters allow them to breed year-round. A

female lionfish may produce 30,000 eggs a month! Lion-

fish were first reported in the Gulf of Mexico in 2009.

Since then, there has not been a collective population esti-

mate on these species. However, scientists observed a

grand explosion in their numbers in the summer of 2012.

Prized as aquarium fishes, despite their venomous spines,

they were likely introduced this way. Hurricane Andrew,

in 1992, released six “pet” lionfish into the bays around

Florida’s Keys. They are also capable of moving in the

ballast waters of ships, in egg and larval forms.

This brochure is funded with qualified

outer continental shelf oil and gas reve-

nues by the Coastal Impact Assistance

Program, United States Fish and Wildlife

Service, U.S. Department of the Interior

through a grant award to the Mississippi

Department of Marine Resources.

seagrant.umn.edu

As well as chemical “mulluscicides,” many organizations

also use “elbow grease” (manually removing the mussels),

electrical currents, and acoustic vibrations to rid them-

selves of these mussels.

Though they may be having a detrimental effect on native

shrimp, some dealers have begun marketing the tiger

prawns as a commercial commodity. However, this com-

mercial crop will be at the expense of our native stocks.

As they are established in the Gulf of Mexico, several

marine organizations (NOAA included) have docu-

mented the best approach to controlling the lionfish

population in Gulf is to eat them! Once the venomous

spines are clipped, the fish has been highly acclaimed

for texture and flavor.

Water Hyacinth

Photographed by Melissa Welsh

Asian Carp

nature.org

Aquatic Aliens:

Invasive Species of the

Gulf of Mexico

Remember

The Institute for Marine Mammal Studies (IMMS) is

a non-profit organization established in 1984 for the

purposes of public education, conservation, and

research of marine mammals and sea turtles in the

wild and under human care. Located in Gulfport, MS,

IMMS has been an active participant of the National

Stranding Network since its inception. IMMS is a

premiere organization in the Mississippi-Louisiana-

Alabama sub-region of the Gulf Coast with the

capability and expertise to care for sick and injured

marine animals. Additionally, IMMS promotes

public awareness of marine conservation issues

through its involvement in the community.

Mammalia Cnidaria

The white-spotted jelly is native to the continent of Aus-

tralia. They are considered large jellies, reaching approxi-

mately 20 inches in diameter in their natural habitat. They

are usually clear to light brown in color, with evenly

spaced white

spots on top of a

rounded bell.

Even though jel-

lies are known to

sting, the white-

spotted jelly has

very mild venom.

If one happens to

brush against

these creatures, the sting is nearly unnoticeable. As an

invasive species, the white-spotted jelly is not a newcomer.

They were first found in Atlantic waters in the 1950s.

They have been known to be a wide-spread phenomenon

in the Caribbean for at least the past 40 years, likely mov-

ing by ballast waters. They were first discovered in the

Gulf of Mexico in 2000. In the Gulf, these species have been

known to be larger than in their native environment. Some

single jellies have been reported to be over two feet across

the bell. These jellies do not use their venom to hunt food

like many other jelly species. The white-spotted jelly is a

filter feeder, primarily feeding on zooplankton. However,

they will also feed upon the larval stages of crabs and

shrimp thereby contributing to the declines in these spe-

cies. In the Gulf of Mexico, both shrimp and crabs

(especially blue crabs) are a very important commercial

commodity. These jellies are not within range of their nat-

ural predators (snails that live in the Pacific Ocean) in the

Gulf of Mexico.

jellyfishfacts.net

Nutria Rat

Myocastor coypus

White-Spotted Jelly

Phyllorhiza punctata

The nutria rat is native to South America. It was intro-

duced to the Gulf coast in the 1930s primarily around

Avery Island in Louisiana. They were originally

brought to the area for use in the fur trade. In fact, the

name “nutria” refers to the fur found on their bodies. It

was noted the nutria was helpful in controlling the wild

populations of another non-indigenous species, water

hyacinth. After they were first introduced, hurricanes

further dispersed them across the Gulf States. Nutrias

are a problem to the local wildlife and wetlands due to

their destructive behaviors. By eating the wetland flo-

ra, the nutrias are exposing the soil beneath to erosion.

It is estimated that nearly 6,300 acres of wetland have

been impacted by nutria damage in the past three years

across Louisiana. Like other rodents, nutrias are

known to reproduce in high numbers and frequencies.

Female nutrias may birth approximately five young per

litter, and are

capable of pro-

ducing as many

as 13 young per

litter. They also

reach sexual

maturity at a

fairly young age,

four to five

months. Be-

cause nutrias have been a long-standing invasive spe-

cies, many native predators have begun to prey upon

them. Predators in the nutrias’ introduced range in-

clude: large fish, birds, and reptiles, like alligators and

turtles. In regulated hunting environments, nutrias are

also a suitable food source for humans.

nola.com

References:

coastalscience.noaa.gov/documents/factsheet_lionfish.pdf

el.erdc.usace.army.mil/elpubs/pdf/ansrp05-4.pdf

“Executive Order 13112 of February 3, 1999: Invasive Species.” Federal Register 64:25 (8 February 1999) pp. 6183-6186.

fl.biology.usgs.gov/Nonindigenous_Species/zebra_mussel_FAQs/zebra_mussel_faqs.html

icwdm.org/handbook/rodents/nutria.asp

news.nationalgeographic.com/news/pf/76205791.html

nutria.com

nwrc.usgs.gov/factshts/020-00.pdf

oceanservice.noaa.gov/education/stories/lionfish/factsheet.html

oceanservice.noaa.gov/education/stories/lionfish/lion04_biology.html

www.ccfhr.noaa.gov/stressors/tiger-shrimp.aspx

www.chron.com/news/houston-texas/article/Asian-tiger-prawns-invade-the-Gulf-of-Mexico-2424242.php

www.gsarp.org/pubs/Initial Survey of Invasive Species.pdf

www.iowadnr.gov/Linkclick.aspx?fileticket=7Bs3FUtdyPk=&tabid=1045

www.issg.org/database/species/ecology.asp?fr=1&si=1050

www.nature.nps.gov/water/marineinvasives/assets/PDFs/Phyllorhiza_punctata.pdf

www.sms.si.edu/irlspec/Phyllorhiza_punctata.htm

www.usatoday.com/news/nation/environment/story/2012-05-07/asian-tiger-shrimp-gulf-mexico/54816844/1

Institute for Marine Mammal Studies

P.O. Box 207 Gulfport, MS 39502

Phone:228.896.9182 Fax: 228.896.9183

Email: contactus@imms.org

Website: www.IMMS.org

Prepared by Melissa Welsh,

2012

In addition to feeding on shrimp and blue crab larvae,

white-spotted jellies are also obstructing trawl nets. Each

jelly may weigh 25 pounds, and this increased weight is

causing nets to tear. This, in turn, is leading to millions of

dollars lost in the Gulf Coast’s fisheries.

There is a current bounty on the nutria’s tail. In Louisi-

ana, wildlife agencies are offering registered trappers

and hunters $5 for each nutria tail brought to

representatives. In the 2011-2012 nutria season, over

350,000 tails were accounted and paid.

Prepared by Melissa Welsh, 2012

gulfallianceeducation.edu