ERNEST A. LACHNER, Exotic Fishes and Other

rr'UADn r>nDT\rc ~~J

Aquatic Organisms

C. RICHARD ROBINS

WALTER R. COURTENAY, „

f Introduced into

North America

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY • 1970 NUMBER 59
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SMITHSONIAN CONTRIBUTIONS TO

ZOOLOGY

NUMBER 59

Ernest A. Lackner, Exotic Fishes and Othe r

C. Richard Robins, and A J • *~^

Walter R. Courtenay, Jr. AquatlC OrganiSHlS

Introduced into

North America

SMITHSONIAN INSTITUTION PRESS

CITY OF WASHINGTON

1970
ABSTRACT

Lachner, Ernest A., C. Richard Robins, and Walter R. Courtenay, Jr. Exotic Fishes

and Other Aquatic Organisms Introduced into North America. Smithsonian Contributions to Zoology, 59:1-29. 1970.—The introduction of aquatic animals from

foreign lands to the waters of the United States is not a new problem, but it is rapidly

accelerating, particularly because of the increase in quantity and in kinds of fishes

entering the aquarium trade. The introduction of each fish species that is judged to be

established is reviewed with respect to place of origin, mode of transport, area of release,

and rationale. Transplants of native fishes from one drainage to another or from one

end of the country to the other, though often resulting in harm to local faunas, are only

reviewed in a cursory manner.

Twenty-five species of exotic fishes are now established in waters of the United

States exclusive of Hawaii. They include one trout (Salmonidae), six minnows

(Cyprinidae), one loach (Cobitidae), one catfish (Clariidae), five livebearers

(Poeciliidae), two drums (Sciaenidae), seven crchlids (Cichlidae), and two gobies

(Gobiidae). Except for the gobies and drums, all are freshwater species. Many other

exotic species have been caught in our waters, but their establishment is not yet

demonstrated.

The areas affected vary considerably, from local warm springs, in which the

exotic species probably could be eliminated, to large and interconnected systems in

which no amount of money or effort could remove the introduced animal.

Introductions have been both purposeful and accidental. Though sometimes well

intentioned, they have never been preceded by a thorough study of the possible effect

of the species in question on the local biota. Where purposeful, introductions have

usually involved a single organization which has acted on the basis of its own limited

interests.

Particular attention is given to Florida and Hawaii, the states most affected by

introductions. They differ markedly in the nature of the problem since in Hawaii

freshwater drainages are isolated and small, whereas Florida's fresh waters are extensive and interconnected by canals. Most of the 64 million fishes imported into the

United States each year enter through southeastern ports, especially Miami and

Tampa. The growth of the aquarium industry in Florida, and careless management of

its holding tanks or ponds, has resulted in the introduction and establishment of species

that serve no useful purpose and can only offer competition with native fishes.

Brief consideration is given to aquatic plants and invertebrates, both groups of

which have created major and expensive control problems.

Although the problems raised by aquatic animals already introduced into our

waters are serious, they threaten to become much worse if meaningful control and

regulation of imported animals is not quickly forthcoming. The biological pathway

involved in the role of introductions is their establishment through reproduction, and

their competition with, and, in some cases, extinction of native fauna. Recommendations are made to assist the control of introductions, and the resolutions of a recent

conference on this subject are repeated.

Official publication date is handstamped in a limited number of initial copies and is recorded

in the Institution's annual report, Smithsonian Year.

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WASHINGTON : 1970

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402 - Price 45 cents (paper cover)
Contents

Page

Introduction 1

Exotic Fishes 3

Review of North American Exotic Fish Introductions 4

Salrnonidae—trouts, whitefishes, graylings 4

Esocidae—pikes 4

Characidae—characins, tetras 5

Gyprinidae—minnows, carps 5

Cobitidae—loaches 7

Clariidae—airbreathing catfishes 7

Trichomycteridae—parasitic catfishes 9

Loricariidae—armored catfishes 9

Poeciliidae—livebearers 9

Sciaenidae—drums 10

Cichlidae—cichlids 10

Gobiidae—gobies 12

Marine Fish Introductions 13

Aquatic Invertebrate Introductions 13

Aquatic Plant Introductions 16

The Florida Travesty 17

Hawaiian Introductions 19

International Exchanges 20

North American Fish Transplantations 21

Discussion and Recommendations 22

Acknowledgments 25

Literature Cited 26
FIGURE 1.—The pike killifish, Belonesox belizanus, an import from Yucatan, is well established

in waters of south Dade County, Florida. This live bearer, although reaching a length of 8 to

9 inches, is an active, predaceous carnivore on small aquatic life.
Ernest A. Lackner, Exotic Fishes and Other

C. Richard Robins, and A * s-\

Walter R. Courtenay, Jr. AquatlC Organisms

Introduced into

North America

Introduction

Many Americans are more conservation minded today

than ever before. They are generally aware of the need

for water and air pollution control, and even of the

developing problems of space pollution. The human

needs for water and air are direct and fundamental to

sustenance. Other constituents of the environment are

more indirectly associated to human uses. In our national directives for environmental control, many areas

of our natural heritage remain unguarded. One of

these areas, our living, native American biota, is being

biologically polluted through the introduction of living exotic (foreign) life. Some of these introductions

contaminate the natural environment as severely as a

dangerous chemical release in water or air. They also

threaten to replace known wildlife resources with

species of little or unknown value. The specific subject

of this paper is to discuss the extent of introductions of

exotic life, especially fishes, into the aquatic environment of North America and to comment, where possible, on the effects of these releases on the environment

and man's economy.

Introductions of the starling, English sparrow, and

the carp have received such publicity as widespread

pests that most North Americans are generally aware

that these species were deliberate, man-effected introductions. A vast number of exotic species, especially

Ernest A. Lachner, National Museum of Natural History,

Smithsonian Institution, Washington, D.C. 20560; C. Richard

Robins, Maytag Chair of Ichthyology, Institute of Marine

and Atmospheric Sciences, University of Miami, Miami,

Florida 33124; Walter R. Courtenay, Jr., Florida Atlantic

University, Boca Raton, Florida 33432.

aquatic animals of which the public is unaware, continue to arrive in North America, and some, through

accidental or deliberate releases, become established

and are competitively dangerous to native species or

ecological communities. Although various federal and

state regulations have been enacted in an effort to control aspects of the importation of living organisms, the

laws are not comprehensive enough or sufficiently enforced to stop their release. Most agents are unable

to judge or verify identifications of aquatic imports

listed on invoices. One of the unique natural North

American communities, that of tropical Florida, has

become a biological cesspool of introduced life.

The kinds of exotic fishes and some of the other

aquatic animals and plants released into North American waters are summarized here in respect to: the

place of origin, mode of transport, area of release, and

use of the species. Many of the species reviewed serve

as examples in understanding some problems that develop from exotic introductions. Few Americans realize

the diversity and numbers of aquatic plants and animals already released in our waters. Too few Americans

realize the biological implications that such releases

may have on the native fauna or flora or the entire

biological community, or on sport and commercial

fishing that the native species support.

Many problems associated with the importation and

release of animals in American waters were discussed

in an invitational Conference on Exotic Fishes and related Problems initiated by the American Fisheries

Society and the American Society of Ichthyologists and

Herpetologists, held in Washington, D.C, 18-19 February 1969 (Stroud, 1969a). The principal portion of

a paper presented by the first author to this conference

1
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

on the kinds of exotic life introduced into American

waters is here included. A statement concerning introductions of aquatic animals into Florida, prepared

by the second writer, was read before the conference

and most of these comments are also included. The

third writer discussed the occurrence and biology of

the walking catfish, Clarias batrachus (Linnaeus), in

Florida before the conference and pertinent aspects of

that paper also are embodied herein. The present

paper, though stemming from the three reports just

mentioned, has been completely reworked.

We follow the conference on the use of the word

"exotic," implying that it refers to an introduced organism from a foreign country. The release of organisms from one drainage system to another within our

American waters is regarded as a transplant. Most of

our data pertain to the freshwater fish fauna of the

United States. Other exotic animal and plant introductions, as well as some transplants, into the fresh and

marine waters of America, and elsewhere, are discussed

for they are pertinent to the problems associated with

releases of organisms.

The use of exotic species by man, or the need for

transplanting species, has changed considerably in

recent years, particularly in North America. Early man

utilized the natural resources about him. As a hunter

he assisted in the extinction of many animals, such as

the woolly mammoths, North American camels, giant

sloths, horses, and the giant cave bear. Early community life and an agrarian existence hastened the domestication of animals and the cultivation of plants. Migration and emigration of man necessitated the transport of basic food items. Any organism useful to man's

survival became an item in the traffic among early

communities. As man advanced socially and technologically he was attracted to natural life for many purposes, not only for its food value but also for his

pursuits in recreation and entertainment and for ornamentation, medicinal, and other uses. Through experience, man became selective, and with increased

economy, an enormous traffic became possible involving animals and plants on a worldwide scale. Intervention in this traffic in the establishment of controls

necessitates consideration of the species involved,

where and how they are utilized, and the dangers,

known or potential, inherent within each particular

species that may become introduced. The task of adequately screening the biological potential of every

exotic species considered for release may be enormous,

but the results of any improper release may destroy,

forever, a natural community or parts thereof, and

ruin a commercial or recreational resource.

Many individuals have expressed concern for the

dangers inherent in the release of exotic species or

transplanting (stocking) within a country. The Department of Lands and Forests, Ottawa, Canada,

recently conducted A Symposium on Introductions of

Exotic Species (1968, Research Report, number 82,

111 pages). The papers by Crossman (pages 1-20),

Christie (pages 73-91), and Regier (pages 92-111)

provide background data to some of the problems we

discuss. Another recent program reviewed problems associated with the release of birds and mammals.1

 General treatments as Alien Animals by Laycock (1966)

provide further stimulating light reading of man's supreme meddling with wildlife. The public is generally

familiar with adventures as those of Captain Bligh and

his quest in establishing breadfruit in the West Indies, but it h often unfamiliar with common, exotic

species living about them. In fact, the "Washington

Conference" on exotic fishes was prompted by an exchange of correspondence among several professional

biologists over the release of various species of cichlids,

the walking catfish in Florida, and the possible release

of the Asian grass carp in several states.

Many conferees were surprised to learn that at least

25 species of exotic fishes had become established in the

United States, and that more species were being released. The conferees were further impressed when

given a compilation of "Wildlife Imported into the

United States in 1968" by the Branch of Wildlife

Permits, United States Department of the Interior.2

This list includes 64,254,190 live fish imports of which

64,218,294 were tropical fish; 120,000 fish eggs;

170,621 amphibians and eggs; 1,950,106 reptiles and

eggs; 494,125 birds of which 478,960 were caged birds;

and 140,858 mammals of which 124,440 were primates.

1

 Symposium. Introduction of exotic animals: ecologic and

socio-economic considerations. Caesar Kleberg Research Program in Wildlife Ecology, College of Agriculture, Texas Agriculture and Mechanical University, College Station, Texas.

1968:1-25.

2

 Branch of Wildlife Permits, Division of Management and

Enforcement, United States Department of the Interior, Fish

and Wildlife Service, Bureau of Sport Fisheries and Wildlife,

Washington, D.C., WL-483, February 1969, 4 pages.
NUMBER 5 9

Exotic fishes

Almost all imported live tropical species of fishes are

destined for the home aquarist. Nearly all other imported species are used by fish culturists and by federal

and state agencies or private parties for food, game, or

forage purposes. Fishes imported for fish culture are

introduced directly and purposefully into our waters,

whereas those intended for aquarium use become established through discard of surplus stock, escape, careless management of rearing and holding ponds or

through release by the buyer who no longer wants his

fishes and is reluctant to destroy them. The exotic

species released in the United States and/or Canada

and that are definitely known to have established

reproductive populations are listed in table 1. Twentyfive species in eight families are included but the number will certainly increase as more field data become

available concerning natural reproduction in our

waters. We know of many other exotic species that have

been released in recent years, especially in Florida, and

these are reviewed below. All species listed in table 1

live in fresh waters except the two estuarine gobies and

drums. The cichlid, Tilapia melanotheron (Riippel),

thrives in fresh and estuarine waters.

TABLE 1.—Fishes introduced and established in the United States and Canada. This

list includes only those species known to have reproductive populations after

release. The Hawaiian Islands are not included.

CotflTTlOTl TKH71C Scientific name

SALMONIDAE—Trouts, whitcfishes, and graylings

Brown trout Salmo trutta Linnaeus

GYPRINIDAE—Minnows and carps

Goldfish Carassius auratus (Linnaeus)

Carp Cyprinus carpio Linnaeus

Ide Leuciscus idus (Linnaeus)

Bitterling Rhodeus sericeus (Pallus )

Rudd Scardinius erythropkthalmus (Linnaeus)

Tench Tinea tinea (Linnaeus)

COBITIDAE—Loaches

Oriental weatherfish Misgurnus anguillicaudatus (Cantor)

CLARHDAE—Airbreathing catfishes

Walking catfish

Pikckillifish

Shortfin molly

Guppy

Southern platyfish

Variable platyfish

Bairdiella

Orangemouth corvina

Black acara

Oscar

Convict cichlid

Banded cichlid

Jewelfish

Blackchin mouthbrooder

Mozambique mouthbrooder

Yellowfin goby

Trident goby

Clarias batrachus (Linnaeus)

PoEcmn>AE—Livebearcrs

Belonesox belizanus Kner

Poeciha mexicana Steindachner

Poecilia reticulata Peters

Xiphophoms maculatus (Giinther)

Xiphophorus variatus (Meek)

SCIAENIDAE—Drums

Bairdiella icistia (Jordan and Gilbert)

Cynoscion xanthulus Jordan and Gilbert

CICHLID AE—Cichlids

Aequidensportalegrensis (Hensel)

Astronotus ocellatus (Agassiz)

Ctchlasoma nigrofasicatum (Giinther)

CicfUasoma severum (Heckel)

Hemickromis bimaculatus Gill

Tilapia melanotheron (Ruppel)

Tilapia mossambica (Peters)

GOBIIDAE—Gobies

Acantkogobius flavimanus (Temmineck and Schlegel)

Tridentiger trigonocephalus (Gill)
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

The importation of tropical fish for the aquarist's

market has been greatly facilitated in recent years by

air transport and in our knowledge of the use of tranquilizers and additives to sustain life during transport.

It is estimated that more than 1000 species of tropical

fishes are available for public purchase from wholesalers in the United States. We have seen almost 500

species on hand at the establishment of one New York

dealer. Illustrated encyclopaedic works on aquarium

fishes, in order to serve as a useful guide, must treat

more than one thousand species. Many more species

will appear on the American market as rapid air travel

invites exploration for different species and transport

from all countries. The supply of different species (not

necessarily quantity) in tropical Asia, Africa, and

South America is immense. The numbers of species,

estimated by systematists, of such tropical freshwater

aquarium inhabitants as the families of characins, minnows, various catfishes, tooth-carps, killifishes or livebearers, and cichlids would exceed 6,000. This does not

include the huge tropical marine fish fauna, for which

an aquarium market is rapidly developing. The possible release of species from this vast supply of tropical

freshwater fishes is a major danger in the southern

United States, especially Florida and isolated North

American warm springs. Most of these species cannot

endure the temperate and cold waters typical of most

of the United States and Canada. In recent years, however, we have learned that some species, such as

Tilapia, can survive colder Floridian winter temperatures than it experienced in its native Africa and that

it thrives in both fresh and marine waters even to the

point of reproducing in high salinities.

The fish culturists have been primarily concerned

with exotic freshwater fishes for pond-food production

(cichlids, carp), for their sport value (brown trout), or

as possible foragers (grass carp) to eliminate unwanted

aquatic vegetation, or for forage. Most of the freshwaters of North America are temperate to cold. Only a

small number of exotic species live in such waters over

the world, probably not many more than the existing

North American native fauna. But the deliberate introduction of one of these temperate species, the

carp, has saddled North Americans with a permanent

pest. In contrast the tropical waters harbor an immense

fauna.

The following review of fish and other aquatic organisms introduced into "new water systems" distinguishes between (foreign) exotics versus (native)

transplants, and between introduced (stocked or released including escapes) species versus released and

established (known reproductive populations) species.

The discovery of an isolated specimen of an exotic

species qualifies it for listing as an introduced but not

as an established species.

Review of North American Exotic Fish Introductions

Salmonidae—trouts, whitefishes, graylings

Probably the most useful exotic release in North

America was the brown trout, Salmo trutta, that arrived in the 1880s. The first shipments were eggs from

Germany (Salmo fario: German trout, European

brown trout, Von Behr trout) and England (Salmo

trutta: Loch Leven trout, Scotch lake trout). At the

time, these shipments were believed to represent different species. Within a few years following its arrival

in America the brown trout was widely transplanted

from local stocks (Smith, 1896:443) and it is today

widespread in North American waters (Dymond,

1955:544-546).

The huchen, Hucho hucho, a salmonid of the

Danube basin, has been introduced into Quebec

(Crossman, 1968) but there is no evidence of an established population through natural reproduction

(personal communication, W. B. Scott, Royal Ontario

Museum, Toronto, Canada).

Esocidae—pikes

North Americans may soon claim all species of this

Holarctic family with the contemplated release of

young of the Amur pike, Esox reicherti, of Asia, in

reservoirs of Pennsylvania by the Pennsylvania Fish

Commission (Food and Agriculture Organization,

1969

 3) and Stroud (1969b: 7). Of four native North

American species of Esox, one, E. lucius, the northern

pike, is also native of Eurasia. The northern pike

greatly resembles the Amur pike, especially when

young (Nikol'skii, 1954:192). A shipment of 60,000

Amur pike eggs was received by the United States

Bureau of Sport Fisheries and Wildlife in exchange

for certain American fish stocks. The egg shipment

was then transferred to the Pennsylvania Fish Com3

 Food and Agriculture Organization Fish Culture Bulletin,

1(2): 12, January 1969.
NUMBER 59

mission. Stroud (1969b) reiterates: "This is the sort

of independent activity, potentially dangerous as well

as possibly beneficial to American fauna and related

sport fishing, that gave rise in mid-February, 1969, to

a Conference on Exotic Fishes. ... " Unless the

Pennsylvania Fish Commission has a great amount of

biological information not available to us, we surmise

that the ecological niche suitable for the Amur pike

in America can be occupied by one or two native

esocids.

Characidae—characins, tetras

Next to the cyprinids, the characins comprise the largest family of freshwater fishes, probably exceeding

1500 species, and are found in South and Central

America and Africa. Most of these colorful tropical

fishes are excellent aquarium pets for they mature at a

small size and many of the species can be bred in small

tanks or jars. Some attain enormous sizes, as the tiger

fish of Africa, Hydrocynus goliath, exceeding 100

pounds in weight. Other species, such as the piranhas,

are voracious carnivores and feed on a wide variety of

aquatic life and sometimes on terrestrial animals that

may enter water, including man. These fishes are not

only dangerous to man but to the balance of an aquatic

community they invade. Herald (1961:111) lists Serrasalmus nattereri as the common and widely distributed species of piranha most often seen in tropical fish

stores and public aquaria. Moe (1964:205) lists the

pirambeba, Serrasalmus rhombeus, as an exotic aquarium import that is in many dealer's stores. Moe (1964)

also reviews the high probability of these Amazon

tropicals' ability to survive the colder Florida winters

and become easily distributed in the Floridian waterways. Herald (1961:111) and Moe (1964:200) review observed reproduction in captivity of the piranha

species Serrasalmus spilopleura, S. nattereri, and S.

niger. Accidental release of these fishes in the warm

freshwaters of America will surely bring about eventual

establishment. No natural reproduction is as yet known

for the piranha in Floridian waters. But as Moe

(1964:206) cautions, their continued release can occur

very easily, irrespective of existing controls, for the

small juveniles of the piranha arrive from South

America in tranquilized shipments with "harmless" or

vegetarian characins, which they may resemble. Only

an experienced ichthyologist could identify them. This

picture is complicated by the sale in Miami of fishes

of the genera Metynnis and Colossoma, under the

name piranha. One member of this family, the Mexican tetra, Astyanax mexicanus, of Central America is

naturally distributed in the Rio Grande River, Texas,

the northernmost North American limit of any

characin.

Cyprinidae—minnows, carps

Of the six exotic cyprinids that are established and

maintain breeding populations in North America, only

one, the carp, Cyprinus carpio, is widespread over

North America and regarded as a serious pest because

of its disturbance of the habitat, its ability to occupy

a wide variety of habitats, and its predation on the

eggs of other fishes. It was imported from Europe in

1831 by private interests for at that time it was highly

regarded in the United States, particularly by immigrants from Germany, as a food fish. Legislation was

passed as early as 1850 in the United States, placing a

fine on those destroying carp. The carp is a native of

Asia, and was introduced and cultivated in Europe for

several hundred years before its appearance in America

(German carp, and morphological variations, as the

leather carp and mirror carp). Because of its long culture in Europe, it received an early and enthusiastic use

in America. It was stocked in California waters as early

as 1872. Before the turn of the century it was already

subject to much criticism (Smith, 1896: 395-403;

1907: 396-398; Crossman, 1968:8). Thriving in temperate rivers and lakes and utilizing these waterways

as pathways for dispersal, as well as smaller creeks and

irrigation or drainage ditches, the carp continues to

invade new river systems. As an example, Dymond

(1955: 543-544) reviews a situation in Manitoba,

where the carp was unknown until 1938, when it was

taken in the Red River, "having presumably spread

northward in that river from the United States." The

carp subsequently moved farther northward and was

taken in Lake Winnipeg and Sturgeon Bay by 1955,

an extension of about 200 miles in 15 years. Its entry

in the Fraser River system of British Columbia from

the state of Washington via the Columbia River is also

cited by Dymond (1955). In recent decades some

states (e.g., New York) have spent considerable sums

to control carps in their waters.

The goldfish, Carassius auratus, was imported as an

ornamental fish, and numerous releases in private

ponds had occurred by 1900. Native to eastern Asia, it
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

is now widely distributed over the world. It prefers

weedy areas of warm ponds, lakes, and low gradient

streams. Although locally abundant in many areas of

North America it has not proved to be a great pest,

compared to its Asian relative, the carp. The goldfish

is bred by aquarists for elaborations of the head and

fins and brilliant gold-orange colors. These characters

do not persist in natural conditions and many of these

delicate varieties cannot survive. Thus the free-living

stocks that are seen are pale to olivaceous, carplike

fishes.

The ide or golden orfe, Leuciscus idus, is another

Eurasian cyprinid that probably made entry into

American waters through private stocks. It is reported

from several areas in the United States and it has definitely established itself in a Connecticut pond since

1962 or 1963 (Whitworth, Berrien, and Keller,

1968: 59).

The bitterling, Rhodeus sericeus, is native to Eurasian temperate waters and it is of some interest as an

aquarium species. This cyprinid was reported as well

established in Saw-Mill River, Lower Hudson watershed, New York, by Myers (1925) and Greeley

(1937:94). The rudd or pearl roach, Scardinius

erythrophthalmus, also a native cyprinid of Eurasia,

was found established in the Lower Hudson watershed

by Greeley (1937). Myers (1925) recorded the rudd

in Central Park Lake, New York City. The rudd,

superficially resembling the golden shiner, Notemigonus crysoleucas, a native North American species, but

attaining a larger size, is caught by anglers in New York

State. The tench, Tinea tinea, another Eurasian cyprinid, was reported as early as 1896 by Smith (1896:403)

as "somewhat extensively planted in the United States

by the national fish commission." Webster (1941:154)

reported it in Winnemaug Lake, Connecticut, and that

it spawned in June at the Cornell University Experimental Hatchery, Ithaca, New York. Dymond (1955:

544) records the tench in two lakes in southern British

Columbia. These were the results of dumping the

tench exhibited at the first World's Fair in Seattle

into a goldfish pond. Some apparently were then taken

to Lake Union. The tench is predominately a lacustrine

fish. It attains a fairly large size, a specimen from Lake

Libava, U.S.S.R, measured 46.5 cm and weighed 1,485

g at an age of 10 years (Berg, 1949:616). Smith

(1896) said native specimens reach "a maximum

weight of 12 pounds" and that the flesh is firm, white,

and palatable. Although the tench is commercially

marketed in the U.S.S.R., its habits are practically unknown to biologists in America. Perhaps the carp is

more aggressive in occupying ecological niches the

tench might otherwise seek. For a history of the tench

in America, see Baughman (1947).

The grass carp, Ctenopharyngodon idella, is a recent cyprinid entry to the American environment. Native to eastern Asia, the grass carp or white Amur is

reared and propagated for the high quality of its flesh

and because of its rapid rate of growth. Because it is

mainly a herbivore, this carp is a valuable pond and

reservoir fish in the U.S.S.R., China, Taiwan, and

other oriental countries. In its native habitat, it occupies the flat areas of rivers and spawns in the river

channels. The pelagic eggs undergo development as

they are carried downstream. The incubation is from

32 to 40 hours at water temperatures of 27° to 29° C

(Nikol'skii, 1954:214). Spawning occurs during the

summer months. The larvae and young stages enter

inlets where they feed on aquatic invertebrate organisms. The adults will not reproduce in ponds and

reservoirs; they require water flow over river beds and

channels. This carp attains a length of over a meter

and 32 kg. in weight (Nikol'skii, 1954). The grass carp

can be bred in hatcheries. Many Asiatics restock their

ponds with young fish at each growing period. The

grass carp is recommended by Aliyev and Bessmertnaya

(1968) for mosquito control because of its feeding upon

the soft aquatic vegetation with which the aquatic

stage of some mosquitos is associated. Other summaries

on the biology, use, and other literature of the grass

carp are given by Avault, Smitherman, and Shell

(1968), Fielding (1968), and Nair (1968). It has been

imported into the United States in recent years and it is

currently being reared in ponds by federal, state, university, and private agencies in many states, such as

Arkansas, Alabama, Louisiana, Oklahoma, Arizona,

and Oregon (data from a communication read, in

part, at the "Washington Conference" by Kermit

Sneed, Fish Farming Experimental Station, United

States Bureau of Sport Fisheries and Wildlife, Stuttgart, Arkansas, and personal communication). At least

one agency, the United States Department of Agriculture Aquatic Weed Laboratory wishes introduction

of this species in Florida {Miami Herald, Broward Co.

edition, 23 September 1969). The grass carp is now

known to be released in open waters in Alabama. The

real danger inherent with the grass carp is not its life

in ponds and reservoirs, but the great possibility of its
NUMBER 59

release, accidental or otherwise, in the large river systems of America. There are many habitats in our rivers

suitable for the growth of juvenile grass carp and many

of our rivers have adequate breeding beds, channels

and alcoves for spawning and growth of the larvae and

young. It would not be presumptuous to predict that

the release of this temperate species in a river, as the

Mississippi, would almost certainly cause its establishment within the next decade. What are the species

with which it will compete for food? Probably, in the

early years of growth, reproduction, and population increase, the presence of this large river species may not

be detected. But if it finds an adequate refuge for reproduction, its numbers could increase enormously

in a few years, for the females deposit many eggs

(over 800,000 by a 76 cm [30-inch] female; Berg, 1949:

598). The grass carp could become a serious pest, perhaps more so than its cyprinid relative, the carp. Unlike other peoples of the world, most North Americans

do not show any immediate interest in the food value

of such soft flesh fishes as the carplike cyprinids. In the

absence of any actual harvest these species increase

rapidly and frequently destroy the habitat of other

species more suited to our present economy.

Cobitidae—loaches

The oriental weather fish, weather loach or dojo,

Misgurnus anguillicaudatus, is a small eel-like loach

of North China and Japan that is established and is

reproducing in a restricted area of Oakland County,

Michigan, and in the Westminster flood control channel, Orange County, California. The Michigan specimens were collected in 1958 by Schultz (1960) in a

private pond on Hy Meadow farm and also over a tenmile area of the Shiawassee River. An aquarium dealer

at Holly, Michigan, had the weather fish in stock as

early as 1939, from shipments received from Kobe,

Japan. The existing wild stock is surely an accidental or

deliberate release from specimens obtained from the

Holly supplier. Reeve M. Bailey, Museum of Zoology,

University of Michigan, captured more specimens in*

1965 from the same locality. This temperate-water

species attains a total length of about 20 cm (8 inches).

It would not be impossible to eradicate this species from

the Hy Meadow farm pond and the Shiawassee River.

It is not known, however, to be a pest or a competitor

in these waters. The California specimens captured,

numbering about 300 and ranging from 16 to 224 mm

total length, were taken from April to July 1968 near

the Pacific Goldfish Farm, over a three-mile area of

a flood channel by St. Amant and Hoover (1969).

The size range, from young to adults, is good evidence

of reproduction. Captured with the loach were other

exotic fishes, three species of exotic snails and the exotic

African frog, Xenopus laevis.

Clariidae—airbreathing catfishes

This family of airbreathing catfishes has accessory

respiratory organs, in addition to gills, enabling the fish

to utilize atmospheric air. Representatives of the family

are found in the warm waters of Africa and southeast

Asia. Clarias batrachus, the walking catfish or pla duk

dam (a Thai name, meaning dull-colored wriggling

fish), has a native distribution from India to the Phillipines (Smith, 1945; 348), where it lives in swamps,

ditches, canals, lakes, and rivers. It is an aggressive,

omnivorous feeder, thriving on the available food supply and, in turn, is eaten extensively by fishermen and

farmers. It may be kept alive in moist baskets or tubs

and is sold in this condition in the markets. Albinism is

fairly common in this species and the pale pink smaller

specimens have been sought by aquarists for years. The

accidental release of the walking catfish in southern

Florida, from outdoor holding ponds of local aquarium

dealers, may be the most harmful introduction to any

North American area so far witnessed because of its

severe competitive habits. In the past few years it has

become abundant from Ft. Lauderdale northward to

Lake Okeechobee and West Palm Beach. Occurrences

in the Miami area apparently resulted from separate

releases. Vernon E. Ogilvie, Florida Game and Fresh

Water Fish Commission (and discussant, "Washington

Conference") says the species is out of control, and that

there is no practical method of eradication. Its invasion

of the Everglades, northern Florida, and Georgia, and

perhaps the Gulf Coast states westward to Texas is

inevitable because of its prolific reproduction, rapid

growth, ability to maintain itself in dense populations,

and to distribute itself easily by the many interconnecting natural and man-made waterways, or by land. Like

some species of Tilapia, this catfish is tolerant of high

salinities. It has been found commonly in parts of the

intracoastal waterway in Palm Beach County. Thus

coastal avenues of dispersal are also open. This aggressive species has no natural Floridian competitor. It can
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

FIGURE 2.—Albino walking catfish, Clarias batrachus, an Asian import, surface at edge of pond

in Brevard County, Florida.

move considerable distances overland, especially on

damp or rainy nights and easily occupy new water

systems. In its voracious food habits it competes with,

and in time may deplete, the native food and game

fishes, particularly the centrarchids, of the warm southeastern freshwaters with which it competes directly

for food. Small natural ponds from which the walking

catfish has been seined in Florida, produced up to 3000

pounds of this species per acre. There is no current

American market for its flesh. Certainly, the food fishes

it replaces are far more palatable. This species is a

severely harmful competitor, for it apparently reduces

the entire freshwater community that it invades to one

common denominator, more walking catfishes. Buckow

(1969) and Idyll (1969) present illustrated accounts

of the invasion of Floridian waters by the walking

catfish.

Following the alarm raised by biologists and conservationists over the introduction of tliis species in

Florida, much publicity was accorded to it with the

result that demand (and prices) for it rose and the

species is now reported from aquarium shops in Alabama, Georgia, North Carolina, Ohio, Connecticut,

Louisiana, and Texas. Possible widespread introduc-
NUMBER 5 9

tion of this species may have been aided by the publicity given it.

Trichomycteridae—parasitic catfishes

The parasitic catfishes, or pygidiids, are small, slender

scaleless inhabitants of tropical South America, most

of which occur only in freshwaters though the family

includes coastal representatives. They enter North

America through the aquarium traffic and, like the

piranha, are traded as novelties. While some species are

free-living, others are parasitic on fishes, feeding on the

blood of the gills. The opercle and preopercle are

armed with retrose spines, and when the opercle is extended, the fish becomes hooked to objects it contacts.

The dreaded candiru (Vandellia cirrhosa and other

species) is feared by the South American natives because these diminutive fishes penetrate the urogenital

openings of men and women bathers (as well as other

mammals in water) causing severe pain, inflammation, and hemorrhaging, often necessitating surgery.

This species should be rigidly controlled and prohibited

from all aquarium trade. No introduction is as yet

positively known for these fishes, but once unknowingly

released they could thrive in the warm waters of the

southern United States, especially in Florida.

Loricariidae—armored catfishes

Many species of loricariid catfishes, as well as the

callichthyid catfishes, native to tropical South America, are favored by tropical fish hobbyists. Rivas

(1965:256) reports a mailed catfish, Hypostomus

plecostomus, from a rock pit pond in West Miami. It

is also known from the Snapper Creek Canal system.

Callichthys species, has also been captured in southern Florida waters, in Palm Beach County. There is no

information on any observed reproduction in Florida

of these fishes. From reports by ichthyologists, several

other species of armored catfishes are also involved

in introductions in the Miami area.

Poeciliidae—livebearers

This New World family is found from the United

States to southern South America. The poeciliids,

viviparous topminnows or livebearing toothed-carps,

number about 150 species and are most abundant in

tropical Central and South America. They are very

popular species with fish hobbyists for they thrive and

reproduce readily in small enclosures. The pike killifish, Belonesox belizanus, an import from Yucatan, is

established in the Miami area of Florida (Rivas,

1965:256), where it is now abundant. The pike killifish, although attaining a maximum size of only 20 cm,

is equipped with sharp teeth and has a vicious disposition. It is an active, predaceous carnivore on small,

aquatic life, including young fishes, and serves only as

a detriment to our native fauna. During periods of

drought when waters are confined to the canals proper,

this species has been observed to eliminate all small

fishes from the area. This introduction seriously impairs the natural control on mosquito larvae by the

mosquitofish, Gambusia affinis.

The shortfin molly, Poecilia mexicana, is established

in Blue Point Spring, and the Moapa River, Nevada,

apparently a release from an aquarium fish-rearing

business at Blue Point Spring, Clark County, Nevada

(Deacon, Hubbs and Zahuranec, 1964). These authors

also list the guppy, Poecilia reticulata, and the southern

platyfish, Xiphophorus maculatus, as introduced into

Blue Point Spring about 1957 and present in 1963, and

also representing releases from a private aquarium

dealer at Blue Point Spring. Deacon, Hubbs, and Zahuranec (1964) and Hubbs and Deacon (1964)

review the effects of exotic introductions competing

with native, endemic fishes in springs of southern Nevada, involving the three introduced species listed

above, an introduced exotic cichlid and the mosquitofish, Gambusia affinis. Decline in numbers and extirpation of local, native fishes, such as the killifish,

Crenichthys baileyi, and the Pahrump killifish, Empetrichthys latos, were shown as a result of these recent

releases. Other local races of native catostomids and

cyprinids are predicted also to be adversely affected

and one species, the Pahranagat spinedace, Lepidomeda altivelis, probably has become extinct through

competition. This spinedace was originally described

by Miller and Hubbs (1960:26) based on twenty four

specimens collected in 1938 from the outflow of Ash

Spring, Pahranagat Valley, Lincoln County, Nevada,

and from Upper Pahranagat Lake, Lincoln County, by

Carl L. Hubbs and party, and three specimens collected by Charles H. Gilbert in 1891 from Pahranagat

Valley, Nevada. Extensive field collecting in 1959 to

verify its presence revealed none (Miller and Hubbs,

1960). These authors found "hordes of carp" and "considerable numbers" of the mosquitofish, Gambusia
10 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

affinis, both introductions, which most plausibly

contributed to the nearly certain extermination of the

Pahranagat spinedace.

Another poeciliid, the variable platyfish, Xiphophorus variatus, an import from Mexico, is reported

by Brown (1962) as established in the Missouri drainage of Montana.

Poeciliids, a cichlid, and other species, which were

introduced into hot springs near Banff, Alberta

(McAllister, 1969:31) were determined to be releases

from local aquarists. Apparently the following species

are successfully reproducing there: Poecilia latipinna,

Poecilia reticulata, Xiphophorus helleri, Gambusia affinis, and Cichlasoma nigrofasciatum. The success of

these releases at such a high latitude demonstrates

that reproduction was not affected by the different

photoperiodism compared with that of lower latitudes.

Gambusia affinis was introduced in ponds in the Columbia Basin of eastern Washington by the Washington

State Health Department in 1968 as a possible control

for the mosquito vectors of encephalitis. This "warmwater" species successfully overwintered in the Pacific

northwest during one of that area's most severe winters

{Palm Beach Times, 3 October 1969).

Sciaenidae—drums

Douglas (1953) and Walker, Whitney, and Barlow

(1961:78-79) list many transplants into the Salton

Sea, California, over a period of 30 years, including

such forms as the striped bass, anchovy, bonefish, pompano, corbina, croaker, mackerel, mullet, mojarra,

shad, grunion, silverside, flounder, opaleye, wrasse,

bairdiella, longjaw mudsucker, thread herring, orangemouth corvina, and others. Of these, nine species survive, including the native desert pupfish, Cyprinodon

macularius. Only four of the stocked fishes are known

to reproduce: the sargo, Anisotremus davidsoni (Pomadasyidae); bairdiella, Bairdiella icistia (Sciaenidae) ; the orangemouth corvina, Cynoscion xanthulus

(Sciaenidae); and the longjaw mudsucker, Gillichthys

mirabilis (Gobiidae). The success of these transplants

is of special interest because of the nature of the environment, for the Salton Sea today is not only saline,

but the relative amounts of the various salts differ from

that of marine water and it is subject to considerable

temperature fluctuations. There was a gradual extirpation of the freshwater species after the Sea was

formed in 1906, such that the most abundant species

in 1916 (the carp, Cyprinus carpio) had disappeared

in 1929 with increased salinity. Today the introduced

orangemouth corvina is an important game fish. This

species abounds in the Sea, attaining weights of 32

pounds. The Salton Sea is an excellent example of an

area where there was good chance to gain and nothing

to lose or harm by trial and error introductions.

Cichlidae—cichlids

This large family of tropical fishes comprises about

850 to 1000 species found mainly in Central and

South America and Africa. One genus occurs in Asia.

One species, the Rio Grande perch, Cichlasoma cyanoguttatum, is distributed naturally from Mexico to

Texas. The cichlids are popular among aquarists because of their brilliant colors and interesting breeding

behaviors. They are hardy species that propagate easily

and they are used widely for commercial food purposes.

Many species adapt both to fresh and estuarine waters

and their predaceous habits make them competitive to

native North American warm-water bass and sunfish.

Many species have been imported and probably more

species than we are aware of have been released. The

study of the systematics of the family is very incomplete and many species are difficult to identify, particularly the juvenile stages, with the existing literature.

Several species have been released, deliberately or

through careless pond maintenance, especially in Florida, by state stocking programs, escapes from tropical

fish dealers or state experimental ponds, or releases by

hobbyists, whose pets outgrow the container. The

senseless introductions and the survival possibilities of

cichlids is compared with early carp introductions in

the United States by Hubbs (1968). The clichlids may

be considerably more tolerant and adaptive to environmental hazards than is now suspected (Hubbs, 1968).

Populations finding refuge in many of our natural,

warmer, southern waters, warm springs, or even in such

artificial water sources as areas of thermal pollution,

may eventually establish and distribute themselves

over most of the southern states.

Eight species, apparently, are established in North

America. The black acara, Aequidens portalegrensis,

and the oscar, Astronotus ocellatus, are South American imports established in south Florida canals and

waterways (Rivas, 1965:256). The convict cichlid,

Cichlasoma nigrofasciatum, a central American import,
FIGURE 3.—Upper: the Mozambique mouthbrooder, Tilapia mossambica, native to Africa, has

been widely distributed in North America. This specimen was taken from the brackish waters

about Hypoluxo Isle, Palm Beach County, Florida.

Lower: the black acara, or port cichlid, Aequidens portalegrensis, a South American species,

is well established in south Florida canals and waterways. This species appears to thrive in Florida

waters occupied by the walking catfish.
12

is established in ponds about Miami (Rivas, 1965), in

Roger Spring and Ash Springs, Nevada (Deacon,

Hubbs and Zahuranec, 1964; Hubbs and Deacon,

1964), and in a hot spring at Banff", Alberta (McAllister, 1969). The banded cichlid, Cichlasoma severum,

a South American species, was released in Roger

Spring, Clark County, Nevada (Hubbs and Deacon,

1964). Recently a well-established population of a

Cichlasoma, the species of which is not yet definitely

determined, was discovered in northwestern Miami.

The jewelfish, Hemichromis bimaculatus, a colorful

African species of the fish fancier, is known to be in a

Hialeah canal, south Florida (Rivas, 1965:256) and

near the Miami airport. The blackchin mouthbrooder,

Tilapia melanotheron, native of Africa, is well established in the Hillsborough Bay area of west-central

Florida (Springer and Finucane, 1963). These authors

report that the blackchin mouthbrooder is marketed

in Tampa as "African sunfish." They refer to a live

commercial catch of 1553 pounds from Bullfrog Creek

on 13—17 December 1962 when water temperatures in

nearby Old Tampa Bay were 9.6 C (49°F). The Mozambique mouthbrooder, Tilapia mossambica, another

species native to Africa has been widely distributed

(Atz, 1954) and was listed as released in Alabama by

Smith-Vaniz (1968), and established in Texas (Hubbs,

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

1961:12) and in a warm spring pond at Bearmouth,

Granite County, Montana, by Brown and Fox (1966).

Other species of cichlids are known to have been

released but no data are currently available concerning their reproduction. The tucanare or peacock cichlid, Cichla ocellaris, native to South America was

released (10,000 juveniles) in the area about Fort

Lauderdale, Florida (Moe, 1964: 205; Ogilvie, 1966);

the firemouth, Cichlasoma meeki, a Central American cichlid was reported from a rock pit pond, Miami,

by Rivas (1965); the blue tilapia, Tilapia aurea, an

African species, is used in pond culture studies in Alabama (Smith-Vaniz, 1968:114) and apparently has

been introduced in Florida {Tallahassee Democrat,

page 6, 20 June 1969); and the Congo tilapia, Tilapia

melanopleura, was released in Alabama and also used

there in experimental pond culture studies (SmithVaniz, 1968:114).

Gobiidae—gobies

Two Asian gobies are well established in the Stockton area, California. The yellowfin goby, Acanthogobius

ftavimanus, native to the estuarine waters of Japan,

Korea, and eastern China, was first reported in the

San Joaquin Delta by Brittan, Albrecht, and Hopkirk

FIGURE 4.—The peacock cichlid, or tucanare, native to South America, attains large sizes. Many

juveniles were released in waters of Dade County, Florida in 1964.
NUMBER 59 13

(1963). The trident goby, Tridentiger trigonocephalus,

also from the coastal waters of China from about Hong

Kong and the northern Philippines, northward to

Japan, Korea, and the Amur River, is known to be

established in the Stockton area (Earl S. Herald,

Steinhart Aquarium, personal communication; M. R.

Brittan, manuscript). Both of these species could be

bilge-water transports from Asia.

Marine Fish Introductions

The ease and speed with which delicate, tropical

freshwater fishes may be transported applies equally

to the transport of marine species, and many colorful,

tropical marine forms are appearing in aquarium

stores. Although it is not now possible to appraise the

extent of marine fish introductions, we can foresee the

exchange and introductions of American Atlantic and

Pacific faunas. Many marine fishes may not reproduce

in the home aquaria, but many beautiful forms can be

kept alive for extended periods of time. This is all

that is necessary for a prelude to establishment in

"new" waters, for releases can be made easily in coastal

regions that provide adequate ecological conditions.

Exotic marine fishes have already been introduced into

the American fauna, either accidentally by bilge-water

transport as the two species of Asiatic gobies in California, or by official, deliberate releases.

Some examples of marine fish introductions and the

method of transport follow: The milkfish or awa,

Chanos chanos, family Chanidae, is an Asiatic species

established in the marine, inshore waters of Pacific

Mexico. Smith (1896:403) reports the release of this

species in California waters as early as 1876-1877 by

the California Fish Commission. Springer (1963:453)

reported on Omobranchus dasson (japonicus), a marine blenniid fish native to East Africa, Australia, and

Japan, from Trinidad. He suspected the Trinidad

record to be erroneous but since then the species has

been collected by Miami biologists at Trinidad and in

Venezuela. In 1969, Robins found this blenny to be

the most common species around the docks north of

Port of Spain. This species is apparently a bilge-water

import. Strasburg (1956; 1966) reported the first

Hawaiian record of another blenniid fish, Omobranchus elongatus, based on four specimens obtained from

a concrete tank located on Coconut Island, Kaneohe

Bay, Oahu. A fifth specimen was taken in Pearl Harbor

in 1963 from an open reef, 18 miles from Coconut Island, and from this single specimen Strasburg assumed

the species to be native of Hawaii. However, the

original four tank specimens could have been imports,

for in 1951 pieces of coralline rock with Tridacna clams

and undoubtedly other organisms were removed from

the Samoan Islands to the Oahu tank by the staff of the

Pacific Oceanic Fishery Investigations, United States

Fish and Wildlife Service, Honolulu. The natural distribution of O. elongatus includes East Africa, East

Indies, and the Central Pacific. Wheeler (1958) demonstrated that the new genus and species described by

Fraser-Brunner as Parviclinus spinosus from the Conway estuary, England, actually represented a small

Caribbean clinid, Stathmonotus stahli. Since this

species was not a British aquarium form, Wheeler

theorized that its transport from its native western

Atlantic habitat was either by a floating dock or hold

of a dredger, or among the fouling organisms of a

ship's hull. The Conway estuary is only 40 miles from

the large seaport, Liverpool. A similar example of

freshwater introduction, which misled a systematise

was the description by Fowler of a new serranid species,

Pikea sericea, from Hong Kong, China, which was

shown by Robins and Bohlke (1960) to represent the

American largemouth bass, Micropterus salmoides.

Boeseman (1954) recorded two specimens of a neotropical catfish found dead near Biezelinge, Zeeland,

The Netherlands, of the genus Sciadeichthys, a group

known to inhabit the salt and brackish shores and

estuaries of northern South America. These specimens

were described as a new species, S. walrechti Boeseman.

Boeseman (1954) remarked that "the present specimens must have been transported by ship."

Aquatic Invertebrate Introductions

Many different groups of exotic aquatic invertebrate

animals follow the same pathways of arrival to American waters as fishes, and probably they often arrive

together. Various species have been imported for their

food value, for aquarium uses, for public displays, as

items of curiosity, and some have arrived accidentally

as ship stowaways by several methods. Only a few

salient examples are discussed to illustrate some of the

modes of transport, common species released, and

dangers involved. Large numbers of an alien crab were

found in the Hillsborough River, Hillsborough County,

Florida, in 1939 by Marchand (1946). These were

saber crabs, Platychirograpsus typicus Rathbun, native
14 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

to Mexico. The type locality was the Macuspana River,

Montecristo, Tabasco, Mexico (Rathbun, 1914:122).

Marchand inspected the deck of a ship at Tampa,

Florida, in 1940, that had just unloaded its cargo of

logs, and several saber crabs and four frogs were found,

and he was informed that a snake had been killed on

deck before his arrival. This ship was loaded at Frontera, Puerta, Mexico, state of Tabasco. Marchand also

learned that the Tampa Box Company, manufacturers

of cedar cigar-box lumber, maintained a logging mill

on the Hillsborough River. Large cedar logs were first

imported from Mexico in 1915, where they were

shipped from the Mexican port of Alvaro Obregon,

state of Tabasco. The Mexicans floated the logs to the

coast; so they were in water for sufficient periods of

time to permit organisms to associate with them.

Marchand found that the log mill employees were

familiar with crabs, snakes, and turtles in the cracks of

the logs. Thus, the saber crab made its debut into Floridian waters through lumber mill operations. Newman

(1963) reported an edible oriental shrimp, Palaemon

macro dactylus, in San Francisco Bay, and suggested its

transport was through the salt water system of a ship.

Kinzie (1968) recorded two species of stomatopod

crustaceans, Gonodactylus jalcatus and G. hendersoni,

new to the Hawaiian fauna as entries from the Philippines-South China-East Indies area by transport of concrete barges towed to Pearl Harbor following World

War II from combat areas in the South and West

Pacific. These barges were towed at slow speeds of

about three knots, and organisms lodged in fissures and

holes in the hull would not become dislodged enroute.

Kinzie (1968) discussed the extirpation of the common, native Hawaiian stomatopod, Pseudosquilla ciliata, by the two introduced species, particularly in the

coral head habitat.

Katkansky, Dahlstrom, and Warner (1969) discuss

survival and growth of the European flat oyster,

Ostrea edulis, in California, a species known to harbor

pathogens. They remark (page 72): "The origin of

microcells in oysters is of considerable interest, for two

reasons. First, if microcells were present in the oysters

before importation to California, their introduction

and apparent pathogenicity create an extreme danger

to existing stocks of oysters and possibly other shell

fish ... " Official transplants of the western Atlantic

lobster, oyster, and soft clam to American Pacific

coastal waters were commenced nearly a century ago

(Smith, 1896). Official oyster introductions in California were attributed to have included two destructive

pests, the slipper shell, Crepidula fornicata, and the

Eastern drill, Urosalpinx cinereus (McMillin and Bonnot, 1932). Enemies of the Olympia oyster, Ostrea

lurida, such as the introduced Japanese oyster drill,

Tritonalia japonica are discussed by Chapman and

Banner (1949). The Japanese oyster drill was introduced into Puget Sound from Japan with the stocking

of the Pacific oyster, Ostrea gigas. The spawning of the

European oyster in the waters of Maine was reported

byLoosanoff (1962).

The introduction, dispersal, and reproduction of the

Asian clam, Corbicula fluminea, is an example of a

single organism becoming an expensive permanent

pest within the span of a few years. Ingram (1948:90)

reported this clam in a number of localities of the

Sacramento and San Joaquin River systems of California and from several localities in the Columbia

River system, Washington. Widely distributed in its

native Asia, it is found in Southeast China, Korea, and

in the Ussuri Basin, southeastern U.S.S.R. Corbicula

clams are marketed and eaten fresh or dried by Asians

and they also provide food for domestic ducks and

wild ducks. When they were released into the United

States waters is not known. Perhaps certain West Coast

ethnic groups imported live specimens for local culture, or perhaps they entered through the aquarium

trade. Their extraordinary dispersal into most of the

main river systems of the United States is reviewed

by Ingram (1959), Ingram, Keup, and Henderson

(1964) and other authors. From the West Coast this

clam has invaded the Colorado, Tennessee, and Ohio

River systems and elsewhere in the eastern United

States to Florida. Because of its reproductive success

and high infestation it has become a serious pest in

various irrigation operations, invading in abundance

the canals, ditches, pumps, and cooling systems. Near

Tracy, California, these clams choked irrigation gates

and valve chambers to the point where they were

inoperable. Ingram, Keup, and Henderson (1964:122)

discuss several possible methods of dispersal of C.

fluminea in American waters. One is by transport on

barges containing river gravel for use in the construction of locks, dams, docks, etc., in building and maintaining navigable waterways. Such gravel is often

shipped several hundred miles and it provides sufficient

moisture to maintain the clam for long periods of time.

Gravel spillage en route could include clams. So many

clams were included with gravel used for concrete in
NUMBER 59 15

the Tennessee River system that the concrete did not

set properly and soon crumbled. Ingram, et al. (1964)

also review the idea of clams hitchhiking a ride on

water fowl, clamped tightly in resistance to desiccation,

or that a clam swallowed by a duck could close itself

enough to avoid digestion, pass through the digestive

tract alive, and be deposited in another drainage system. More probable methods of dispersal included

discard by tourists, by fishermen as bait, or by aquarium

hobbyists.

A well-documented molluscan introduction is that

of the large ampullariid snail, Marisa cornuarietis, into

the drainage canal system of south Florida. This is,

however, only one of many introductions of this snail

outside of its native northern South American habitat. Marisa has been much touted as a biological

control of the molluscan vector of schistosomiasis,

Biomphalaria glabrata, in Puerto Rico and Cuba.

Marisa entered the aquarium trade as the "Colombian

ramshorn," but despite its handsome appearance, it

has proved to be a destructive pest in aquariums. It

is through its release by disenchanted aquarists that

Marisa became part of the Florida biota (Hunt, 1958).

The distribution and biology of Marisa in the greater

Miami (Dade County) area was studied by Hale

(1964) who found that although Marisa's poor tolerance of cold would limit its natural dispersal to

Florida, Marisa was otherwise eminently suited to

survive in South Florida. The damage Marisa can do

in this area, particularly in the Everglades where it

will presumably become established, is major since

Marisa competes with another ampullariid, Pomacea

paludosa, the food of the Everglade kite and the

limpkin. It is not known whether Marisa can be substituted in the diet of these birds since Marisa is

planorbiform and possibly more difficult to extract from

its shell than the globose Pomacea.

Further introductions of Marisa into the United

States as a control of aquatic weeds, particularly water

hyacinth, are being contemplated and investigated

by the United States Department of Agriculture,

Aquatic Weed Laboratory, and the Biology Department of the University of Miami. Hale (1964) found

that the two most rank weeds in South Florida, the

introducted water hyacinth and Elodea species, were

seldom eaten by Marisa because many kinds of other

foods were available. Seaman and Porterfield (1961)

determined that water hyacinths exposed to densities

of Marisa, far greater than naturally occurring, were

not eradicated, although the snails retarded the plants'

growth through root pruning. If Marisa is possibly

an innocuous introduction (in colder parts of the

United States) it is probably also an ineffectual one

in its role as an eradicator of aquatic weeds. In Florida

it can only be viewed as potentially detrimental to two

of our desirable bird species.

Another recent molluscan introduction contrasts the

difficulty of eradicating aquatic introductions and the

relative speed with which terrestrial exotics can be

sometimes controlled. As with Clarias, the walking catfish, it also illustrates some peculiar quirks of human

psychology.

Achatina fulica is a large snail, up to one foot long,

used, if not valued, by the Japanese armed forces and

established as food reserves by them throughout the

Pacific during World War II. A vegetation-devouring

hermaphrodite, it is a scourge in Hawaii. Two years

ago a few were smuggled into North Miami by a

tourist returning from Hawaii and were subsequently

released. By fall of 1969, the restricted population had

"boomed" and had become dense enough for the snails

to be conspicuous and destructive not only to vegetation but to the stucco walls of houses {Miami Herald,

26, 27 September 1969). Fortunately the snail seems

still to be confined to an area encompassing roughly

40 city blocks. A $30,000 program of spraying a calcium-baited arsenic poison has been started by the

Florida State Agricultural Control. (Presumably, the

same bait will be attractive to other snails, notably

the native tree snails of the genus Liguus.) Due to its

terrestrial nature and relatively slow dispersal Achatina

fulica probably will be eliminated. In contrast, most

aquatic and amphibian exotic species, because of their

cryptic nature, rapid dispersal, and the still impossible

task of selective killing, are with us permanently. Despite repeated requests from county and state officials

via all news media, novelty-seekers are apparently removing snails from the area to keep (for how long?)

as a curiosity. Thus, there is a distinct and increased

threat that this snail will be reestablished in Dade

County, conceivably in the multimillion-dollar farming

area.

A potentially dangerous introduction is discussed by

Abbott (1952) involving a melaniid snail, family

Thiaridae, for it serves as an intermediate host of a

human trematode. Thiara (Tarebia) granijera, an

aquatic snail native to the warmer regions of southern

Asia, the East Indies, and the larger islands of Oceania,
16

and an important intermediate host of the oriental

lung fluke, Paragonimus westermani, was found established in Lithia Spring, Hillsborough County, Florida.

This small snail prefers the shallow riffles of fast-flowing

freshwater streams. Abbott reports that it exists in

Lithia Spring in "extraordinary numbers, sometimes as

many as 400 specimens per square foot." He traced its

entry into the United States via California and East

Coast aquarium dealers. Its release at Lithia Spring

could have occurred when a Tampa fish dealer

gathered aquatic plants using tubs that were not

properly washed free of the snails. Thiara granifera

serves as an intermediate host of numerous trematodes,

three of which are known, in their adult stages, to

parasitize man (Abbott: 1952:108). A second intermediate host, such as a freshwater crayfish or crab, is

a necessary part of the life cycle of the fluke, and there

is only a potential menace of human infection, for these

crustaceans must be eaten raw if the fluke is to infest

man. Abbott (1952:113) lists two other species of

thiarid snails that have been raised by aquarists and

that may be confused with T. granifera—Hemisinus

cubanianus from Cuba and Pachychilus glaphyrusfrom

Central America. The magnitude of introductions is

further realized by Abbott's statement (1952, page 12

and Abbott, 1950) that "In the past hundred years approximately 50 species of exotic species of land and

fresh-water mollusks have established themselves in the

United States and Canada." Thousands of living

European land snails, Otala lactea and Cepaea hortensis, were reported to have been sold in Ohio as catfish

bait (Ingram, 1952). He surmised that these species

came from Italy through the port of New York for the

New York Italian market and that the fish bait enterprise was a more lucrative subsequent development.

The presence of the blood fluke, Schistosoma mansoni, in Puerto Rico and other parts of tropical America, should alert Public Health officials in regard to

its potential introduction into North American waters

through its intermediate host, Biomphalaria (Australorbis) (Erdman, 1967).

Many other kinds of animals have been widely distributed through man's activities. The vacationist will

often pick up plants and animals along the highway,

but tire of them before arriving home, and discard

them. Many species of turtles have been introduced

into new North American areas in such a manner.

Aquatic turtles are common items in the aquarist's

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

trade and these are often discarded into open waters

as with aquarian fish. The giant, predaceous fish eater,

the eastern alligator snapping turtle, Macrocheleys

temmincki, was recently reported in Californian inland waters (Murphey, 1969), probably resulting from

an aquarist's release.

Aquatic Plant Introductions

Exotic aquatic plants have had a long history of introductions into North American freshwaters. Many

species have been introduced by dealers for they are

sought by the aquarist and private pond culturists for

their beauty and interest value. Different examples of

some of the common exotic species now growing wild

in the United States and Canada are reviewed below.

Among those treated by Hotchkiss (1967) are:

Flowering rush—Butomus umbellatus: a European

rush found along tidal St. Lawrence River about

1900; known in freshwaters from Michigan to

Quebec, Idaho, Illinois, and Vermont.

Eurasian watermilfoil—Myriophyllum specatum:

known in the United States for about 70 years; inhabits fresh inland waters and fresh-to-brackish

coastal waters; found in California, Wisconsin to

Vermont, Texas, and Florida.

Parrotfeather—Myriophyllum brasiliense: native to

South America; a common aquarium plant growing

wild in freshwater over most of the United States.

Andean watermilfoil—Myriophyllum elatinoides:

native of South America; abundant in the Deschutes

River, Oregon.

Limnophilas—Limnophila indica and L. sessiliflora:

from southeastern Asia; grown as aquarium plants

in North America and they grow wild from Texas

to Florida.

Water starwort—Callitriche stagnalis: a native of Europe; wild from British Columbia to Oregon, and

Wisconsin to Quebec and Maryland.

Naiad—Najas graminea: an Old World native; wild

in California ricefields.

Naiad—Najas minor: Eurasian origin; grows from Illinois to Vermont, Alabama, and Florida; common

in tidal Hudson River and in artificial lakes.

South American Elodea—Elodea densa: a common

aquarium plant; widespread over the United States,

in fresh waters and sometimes coastal waters.
NUMBER 59 17

Curly pondweed—Polamogeton crispus: native to Old

World; known in North America for at least 150

years; ranges from Alberta to Quebec, California,

and Florida; inhabits fresh inland waters and fresh

to somewhat brackish coastal waters.

Salvinia—Salvinia rotundifolia: native to tropical

America; abundant in freshwaters of Georgia and

Florida.

Ottelia—Ottelia alismoides: introduced from southeast

Asia or Australia; wild and abundant in southwestern Louisiana.

European frogbit—Hydrocharis morsus-ranae: escaped

from cultivation at Ottawa, Ontario; since 1932 it

has spread several miles down the Ottawa River

and is near Montreal, Quebec.

Yellow floatingheart—Nymphoides peltatum: a European import; abundant locally, in Washington,

New York, New Jersey, Missouri, Oklahoma, and

Arkansas; inhabits freshwater and, rarely, coastal

areas.

Ivyleaf buttercup—Ranunculus hederaceus: native of

Europe; established locally from Newfoundland to

South Carolina.

Waterchestnut—Trapa natans: native of Eurasia; a

great pest since about 1930 in fresh and some coastal

waters from Massachusetts to Virginia; abundant

growth crowds recreational areas and replaces valuable duck-food plants.

Duckweed—Spirodela oligorhiza: native to southeast

Asia and Australia; known wild since 1930 in California, and from Missouri to Maryland, Louisiana,

and Florida.

Water hyacinth—Eichornia crassipes: an emergent

aquatic, native to South and Central America;

abundant in Florida for many years; found wild

from Missouri to Virginia, Texas, Florida, and California.

Alligatorweed—Alternanthera philoxeroides: an emergent tropical plant, sometimes forming floating mats

over extensive areas and crowding out more desirable species; found in fresh tidal marshes in southeast United States and locally in the Tennessee

Valley.

The Florida Travesty

Nowhere in North America have people been more

neglectful than in tropical Florida in regard to releases

in natural waters. Only Hawaii exceeds Florida in

numbers of introduced exotic animals. King (1968:

103) listed fifty-seven species of exotic vertebrates introduced into the Floridian fauna. The introduced

reptiles lead the list of vertebrates, numbering seventeen species. One of these is the well-known South

American caiman, Caiman crocodilus. There are 15

species of mammals, including the nutria, Myocastor

coy pus, an aquatic rodent; twelve species of birds; and

three introduced amphibians (including the giant toad,

Bujo marinus, from Central and South America). At

least ten species of fishes are recognized as successful releases; of these the cichlids exceed all others in numbers of species, and collectively they may rank with the

walking catfish and carp as the most harmful and

undesirable introductions into the American fauna.

The distressing fact concerning the walking catfish

and the cichlid fishes is that both are relatively recent

introductions. This lack of respect for the natural environment is indicative that the existing laws and regulations are either inadequate or insufficiently enforced,

or both, or that there is disregard of the inherent dangers arising from introductions. Another important

factor concerning the Floridian introductions is their

potential spread northward into the warm waters of

the southern United States. Although the Hawaiian

aquatic fauna has had many more introductions than

Florida, these may not prove as harmful, and also, may

be controlled or contained, because of the insular

geography of the state. The exotic invertebrate introductions into the Floridian fauna, including insects,

Crustacea, mollusks, and other forms, exceed the introduced vertebrates.

Florida's mild climate is so much appreciated by

man that we should not be surprised when animals

that escape captivity or are otherwise introduced into

the fauna, should not only survive, but, in a discouraging and increasing number of instances, succeed in

establishing a breeding population. Florida's climate,

topography, and drainage systems combine to make the

problem of animal releases especially serious, notably

with regard to aquatic resources. First, there is no

longer any real division of stream systems in the state.

The many canals that were first dug for drainage (for

flood and mosquito control) and then for irrigation,

and the recent and essential development of back

pumping systems for water conservation, have resulted

in connected water systems that permit access of any

introduced freshwater animal to most of the drainages

in the state. Secondly, the abundance of springs and
18 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

seeps is sufficient to provide many havens for introduced species with essentially stable water temperatures on a year-round basis. The availability of such

refuges permits survival of tropical species during abnormally cold winters when most other waters cool to

temperatures below the supposed tolerance limits of

some of the released species. Thirdly, because of the

warm climate and in recognition of the abilities of

tropical fishes to live in Florida, a large number of

aquarium fish importers and suppliers are located in

south Florida. It is estimated that about 70-75 percent

of the imports of tropical fishes to the United States

arrive at Miami and Tampa. Importers and suppliers

of other tropical animals, including birds, mammals,

reptiles, and amphibians, similarly find south Florida

to be an ideal site for their commercial activities. Florida thus has three essential factors for establishment of

exotic animals: (1) A large and steady source of exotic

animals is maintained in the state on a year-round

basis. (2) Suitable environment is prevalent for their

survival. (3) Easy dispersal routes are present.

Although many biologists have been concerned

about introductions, programs aimed to study the

spread and impact of exotic species already established,

as in Florida have not been forthcoming. There is no

monitoring of the water systems to detect newly introduced species. Programs to investigate the importation,

release, survival, behavior, competition, and dispersal

of introduced aquatic animals should be commenced

on a broad basis in cooperative studies involving the

universities of the State of Florida, and state and federal organizations. Some of these now bear responsibility for introducing animals that survive in the

state's waters.

Introduced species are no respectors of political

boundaries. The chachalaca, Ortalis vetula, a gallinaceous bird from Central America was introduced

into coastal islands of Georgia, and apparently is established. It could spread southward through lowland

xeric regions to the Florida Keys. The red-whiskered

bulbul, Pycnonotus jocosus, a tropical oriental bird

whose flocks may be seen in southern Miami, could

spread as far north as Virginia. Although game and

fish releases are managed by the states, it is our view

that exotic introductions as well as transplants into

interstate water systems should be recognized as a

federal problem and covered by federal statute. Many

of the Floridian exotic introductions have been accidental, but a number of releases have been planned

and deliberate. Such official introductions were made

without serious consideration and study of the real

benefits to be derived and without any understanding

of the possible detrimental effects of these releases. In

some instances the specific identity of the stocks is

uncertain. The coho salmon, recently introduced into

the Great Lakes, is the type of release where there was

much to gain and little to lose. A large niche in the lake

ecosystem was unoccupied, and the coho salmon filled

this vacuum and occupied a food chain without much

competition to alternate species. None of the animals

introduced into Florida nor any of those contemplated

for introduction, as certain cichlids, is similar to the

coho example.

The walking catfish is of little value as a sport or

food fish in America, certainly less than the native

food and game fishes with which it will compete. The

oscar, well-established in Dade County, having

weathered our coldest and driest weather on record,

similarly, does not compare well with the native bass

or sunfish. Efforts have been made to popularize this

introduction with anglers, but the oscar can only provide competition for the more desirable native species.

The pike killifish, also abundant in Dade County, is of

no benefit and is a serious and capable predator on

small fishes. In some canals, when periods of drought

confine the waters to the dredged portions, this fish

has eliminated such abundant species as the mosquitofish, Gambusia affinis, as well as other young fishes. The

pike killifish may present a problem to the natural

control of mosquitos.

Various species of Tilapia have been introduced

deliberately in several southern states. This speciose

genus is not fully understood—not only in regard to

the identification of species but also in regard to its

ecological requirements and life histories. New species

are still being described in this group. Some of the

species show considerable tolerance toward saline

waters and can disperse through coastal marine waters

of near normal salinity, as well as through freshwaters.

Obeservations of Tilapia occupying typical inshore

marine habitats have been observed by a number of

workers. At least eight species of Tilapia are already

involved in the Floridian fauna. These were reviewed

above in the discusion of the family Cichlidae. The

blackchin mouthbrooder, T. melanotheron, has already

survived temperatures in Florida much lower than

20 C that was supposedly its lower limit of resistance.

Vaas and Hofstede (1952) showed that T. mossambica
NUMBER 5 9 19

reproduces equally well in fresh and brackish water

up to 30 ppt salinity, and that it survives in 40 ppt.

Zaneveld (1959) was able to get this species to reproduce in waters of 36.2 ppt.

Fishes introduced in rivers and ponds in Alabama

and Georgia could easily become a major Florida

headache as well as disperse farther westward. The

grass carp, Ctenopharyngodon idella, is an example of

a species now introduced in Alabama that could

spread to Florida. The Tilapia problem may be one of

the worst fish cultural blunders in the United States

since the introduction of the carp. Neither the economy

of Florida nor the excellent warm water native sport

fishes already present justify introduction of such softfleshed species and highly capable competitors. The

peacock bass was released into restricted ponds by the

Florida Fresh Water Fish and Game Commission on

the basis that it is a superior sport and food fish.

Ichthyologists, who have seen this fish in South

America, view it as a serious competitor to the largemouth bass in Florida, as well as a poor fighting fish for

the angler. Efforts were attempted to stop release of

the peacock bass in Florida. The state program was

conducted without regard to the unresolved biological

problems concerning the peacock bass and other species

from South America.

Hawaiian Introductions

Continental Americans generally associate Hawaii with

Pacific marine waters and do not realize that the six

major islands of that state contain a relative abundance

of fresh water streams, particularly on the windward

slopes, as well as numerous reservoirs and irrigation

canals. Prior to introductions, Hawaiian fresh waters

contained only a few native gobies, several prawns,

and fewer euryhaline forms.

Although Hawaii may lead in the number of introduced species, the freshwater forms are contained by

insular geographic location. Many, if not most of these

introductions involve continental sport fishes, and these

have been generally beneficial since they provide a new

resource without major danger to native forms.

Brock (1952) presents a history of the introduction

of aquatic animals in Hawaii. He lists 28 species as

established, including the giant clam, Tridacna (new

evidence indicates this species no longer exists in

Hawaii, personal communication, John B. Shoup,

University of Miami); the Samoan crab, Scylla serrata; rainbow trout; carp; goldfish; oriental weatherfish; sailfin molly, Poecilia latipinna; largemouth bass;

bluegill; and the snakehead, Ophiocephalus striatus.

About half of the total number of introduced species

have no economic value, but some of these may be of

interest as aquarium forms.

Morita (1965) provides a more recent treatment of

freshwater fish introductions implemented by the Hawaii Division of Fish and Game. Two salmonid introductions, including brown and brook trout failed.

Those that survived and are presently established include rainbow trout (spawning in restricted areas;

supplemented by stocking with eggs from the mainland) largemouth and smallmouth bass; bluegill; and

four nominal species of Tilapia. Most recent are the

channel catfish, the oscar, and the tucunare or peacock

bass. These last two species are protected. Tilapia,

carp, the snakehead, Chinese catfish (cited as Clarias

fuscus), and the native freshwater gobies are listed as

nongame species. A recent Job Completion Report,

Research Projects Segment of the State of Hawaii for

1 January to 31 December 1968, lists the release of

2000 fingerling grass carp, Ctenopharyngodon idella,

that were imported from Taiwan and stocked in the

Waiakea Public Fishing Area for weed control evaluation. Other Job Completion Reports for the same

period record restockings of two nominal species of

Tilapia, oscar, channel catfish, Chinese catfish, and a

large freshwater shrimp, Macrobrachium lar. Brock

(personal communication) reports successful establishment of the tucunare in irrigation reservoirs where it

has become a favored sport fish, and that another

recently introduced freshwater shrimp, Macrobrachium

rosenbergi, is now established.

Brock (personal communication) also cites several

marine introductions. He points out that the Hawaiian

islands have, essentially, a partial western Pacific marine fauna and flora and that beneficial marine introductions can be made from this western Pacific source.

He and John E. Randall are responsible for the successful introduction of two species of snappers, Lutjanus vaigiensis and L. kasmira, and one grouper

species, Cephalopholis argus, all from Moorea, Society

Islands.

While Hawaii stands to gain new sport fishing and

commercial resources from some of these introductions and hopes to obtain solutions to specific internal

problems, as in the case of the grass carp introduction,

the geographic location and unique freshwater situ-
20

ations of that state can tolerate this variety of management and experimentation. The fresh waters of

continental North America, however, cannot afford

such environmental manipulation, primarily because

the ecosystems are vastly different. The results of Hawaiian introductions, therefore, must not be interpreted as unquestionably positive data for continental application; these results, in fact, apply specifically

and exclusively to Hawaii.

International Exchanges

Introductions of exotic species and transplants of native

species into new drainages have occurred for many

years on a broad basis over the world. Myers (1947)

cautions against the indiscriminate use of North

American species in foreign countries. He pointed out

the dangers of the carp ponds in Brazil (the carp is

now established in Brazilian natural waters) as well as

the exportation of fishes from American waters,

labeled for example, bluegills, where actually several

species of sunfishes were involved. Myers (1955) discusses the freshwater fish fauna of Central America in

reference to the pond culture of Tilapia mossambica.

He points out, as others have, that T. mossambica is

extremely aggressive and that in Mexican waters it

could become widely dispersed into new water systems

in a short period of time. De Buen (1959) lists a number of exotic fish species in the waters of Chile, such as:

carp, Cyprinus carpio; goldfish, Carassius auratus;

tench, Tinea tinea; black bullhead, Ictalurus melas;

mosquitofish, Gambusia affinis; rainbow trout, Salmo

gairdneri; brook trout, Salvelinus fontinalis; and

others. Gines, Marcuzzi, and Martin (1952) discusss

the ecological conditions surrounding the introduction of the rainbow trout and the brook trout in Venezuelan waters. Thompson (1940) discusses ten species

of exotic fishes introduced into the Argentine Andes,

from about 1904 to 1931 and includes four species of

trout, four species of North American salmon, the lake

whitefish, Coregonus clupeaformis, and the Atlantic

cod, Gadus morhua. Of this number, four became

established, the brook trout, Salvelinus fontinalis, rainbow trout, Salmo gairdneri, brown trout, and Atlantic

salmon, Salmo salar. Jones and Saronjini (1952) discuss the introductions of exotic fishes into Indian

waters and a history of transplantations. Four general

groups of fishes are involved: game fishes; food fishes;

larvicidal fishes; and ornamental fishes. Exotic fishes

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

introduced into Indian waters include: the gourami,

Osphronemus goramy, native of Indonesia and introduced in India in the early half of the 1800s; the

tench, imported from England about 1870 with the

golden carp or crucian carp, Carassius carassius, both

native of Europe; and the common carp, Cyprinus

carpio, originally native to China, and first introduced

into Ceylonese waters at about 1914. Exotic introduced

game fishes include the rainbow trout and brown trout.

The exotic larvicidal Indian introductions for antimalarial work include the poecilids, the mosquitofish,

Gambusia affinis, from North America and the guppy,

Poecilia reticulata, from South America. Many ornamental fishes have arrived in India through centuries

of contact with Southeast Asia. Examples from Southern Asia and other countries include the goldfish from

China, the angelfish, Pterophyllum, and tetras from

South America, the fighting fish from Thailand, the

jewel fish from Africa, the paradise fish from China,

swordtails and platys from Mexico, and several barbs

from southern Asia. A survey of the introductions and

transplantation of fishes in the Indo-Pacific region is

given by Schuster (1952). Planned transplantations of

fishes between different areas of the region include 18

species. Krumholz (1948) lists fifty-nine different

countries in which the mosquitofish has been released.

Amoult (1952) gives several exotic introductions for

Madagascar, the earliest one being a gourami, an

anabantid fish from Indo-Malaysia, introduced as

early as 1857. The American cyprinodont fish, Jordanella floridae, was reported in Borneo by Myers (1940).

Maitland and Price (1969) cite a North American

monogenetic trematode new to the British Isles that

probably entered Britain with the largemouth bass,

Micropterus salmoides. A review of the American

crawfishes introduced into foreign lands is given by

Penn (1954), and Thompson (1952) discusses the acclimatization of the American Pacific oyster in Australian waters. Dementiev (1960) reviews the introduction and transplantation of fishes in the U.S.S.R.

relevant to a discussion of the protection of the fauna.

In recent FAO Fish Culture Bulletins (volume 1,

number 1, 1968 and volume 1, number 2, 1969) introductions and transplantations are given for various

countries of the world in which species, such as the

grass carp, various Tilapia, and salmonid fishes are

being widely used for experimental culture and breeding purposes. Erdman (1967) lists nineteen species of

fishes introduced into Puerto Rico, most of which were

from North America.
NUMBER 5 9 21

North American Fish Transplantations

The problems related to exotic introductions into the

American aquatic environment are often similar to

those involved in transplanting native forms into new

drainage systems. The inherent results may be the

same. We know considerably more about the biology

of our native freshwater fish fauna than any foreign

one. Nevertheless, we have stocked or caused the release of fishes in some of our river systems or ecological

areas to the point of no return, with the result that

we can never completely realize the nature of our

original fauna. Intensive and widespread stocking has

created competition leading to or hastening extirpation

of many of our indigenous species.

Elton (1958) reviewed the destruction caused in land

and water habitats through the introductions of plants

and animals in his "ecology of invasions." The Welland Canal, constructed in 1829 as a bypass from the

St. Lawrence River into Lake Erie and opening the

Great Lakes seaways for midwest grain shipments, also

opened the waterways for the sea lamprey, Petromyzon

marinus, for dispersal and population of the lakes and

subsequent damage to the fisheries in a time span of

about 100 years.

Many states followed the United States Fish Commission, organized in 1872, in its early practice of widescale stocking programs, with little or no apprehension

of the ensuing results. Only a professional ichthyologist

may recognize all of the introduced species in parts

of backyard America. The State of Connecticut has

29 native species of freshwater fishes and 24 stocked

species (Whitworth, Berrien, and Keller, 1968:120).

Of 87 fish species listed for Colorado by Beckman

(1952), 33 were introduced or transplanted. Shapovalov, Dill, and Cordone (1959) list 67 freshwater fish

species for California, of which 32 were introduced.

Miller (1961) points out that there are more introduced fishes in Arizona than "natives," and his discussion of the changing fish fauna of the American

southwest gives the following numbers of native versus

introduced forms for several southwestern states based

on his field data and other published accounts: New

Mexico, 61 native, 22 introduced; Arizona, 28 native,

37 introduced; Utah, 26 native, 24 introduced; and

Nevada, 41 versus 21. Miller (1961) links the period

of intensive introductions, between 1930 and 1950,

with the construction of major dams and water diversions and marked increase in human population. Most

of the 36 alien species in the southwestern states came

from eastern United States in "large part as intentional

plants of game fishes." Only eight introduced species

were known as established in the area before 1930.

Miller (1961) further comments that "many of the

established aliens have affected the native species either

directly—through predation, competition, and hybridization—or indirectly by altering the habitat (as carps

have done)." The Mohave chub, Gila mohavensis,

is endangered because it has been reduced in numbers

by hybridization and competition with an introduced

minnow, G. orcutti. The Little Colorado spinedace,

Lepidomeda vittata, faces extinction because of competition from introductions and by environmental

modifications. Most countries are weak in protecting,

by law, their rare and vanishing fishes (Myers, 1953).

Many of our indigenous western trout were extirpated,

or otherwise lost their identity forever through endless

transplantation of new stocks, interbreeding in hatcheries or in nature, introduction of competitive species,

and through environmental modification (Miller, 1950;

Myers, 1953). At least 33 nominal species of trouts

were described (Miller, 1950) mostly from only one or

a few specimens, and the biology and ecology of many

remain unknown. Among those forced to extinction

were the emerald trout of Pyramid Lake, Nevada,

Salmo smaragdus, and the royal silver trout, Salmo

regalis, of the deep waters of Lake Tahoe, California

and Nevada. Many subspecies and headwater races are

today trout genomes resulting from frequent introductions of other native stocks into natural populations

where extensive intraspecific interbreeding has

occurred.

There is little documentation of North American

marine fish transplantations. The alarm expressed by

many biologists over the dangers of continued intermixing of natural populations of animal and plant life,

however, is based on an enormous amount of data. That

many individuals complacently refuse to recognize the

destruction, as well as the benefits, resulting from introductions is even more alarming. Briggs (1969) and

others have reviewed the biological effects related to

the completion of a sea-level canal in Central America.

It is not possible to estimate today what effect a sealevel canal will have on the marine biota of both oceans

for we know very little about the biology of almost all

of the marine inhabitants of the area. Because these

areas repeatedly have been connected through natural

portals as recently as a few million years ago scientists

disagree on the fauna! effects of opening a sea-level
22 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

canal. Based on the history of introductions elsewhere,

it is not presumptuous to predict that considerable

faunistic changes will occur. Because drifting and swimming organisms tolerant to both fresh and salt water,

and those clinging to the hulls of ships or in ballast

tanks, can make their way through the existing canal

is little reason to assume that there is unnecessary

alarm over a sea-level canal (Sheffey, 1969). Unless

some barrier (thermal, electrical, freshwater, chemical,

etc.) is included in the plans of the new canal, many

different kinds of organisms with many different capabilities will utilize the open passageway. Again there is

disagreement concerning the numbers that will successfully establish populations on the opposite side.

The present Panama Canal with its fresh-water barrier

and the Suez Canal with a high salinity barrier only

permitted passage of certain types of animals, and in

relatively limited numbers. It took 100 years for the

Mediterranean to acquire 26 known species (BenTuvia, 1966, and manuscripts of B. B. Collette, and A.

Ben-Tuvia and A. Lourie) of fishes from the rich Red

Sea fauna, and none is known to have made the reverse

route. The relatively depauperate Mediterranean fauna

may have unoccupied ecological niches available today

for the Red Sea migrants. Ben-Tuvia (1966) reported

that the Red Sea species constitute 9 percent of Israel's

Mediterranean coastal fish fauna and "their ecological

importance is fairly great since 18 species are among

the more common in this area, and nine are commercially exploited." Each canal (Welland, Suez, and

Panama) is in areas where the faunas differ qualitatively and quantitatively, and where the ecological associations were also quite different opposite the canal

sites. It is unfortunate that we still lack basic, detailed

studies on what organisms may be moving through the

current Panama Canal. Certainly all biologists agree

that extensive studies of the marine faunas of both

coasts of tropical America are long overdue.

Discussion and Recommendations

In our review of North America introductions several

facts are apparent that are useful in drafting recommendations that will curb the release of exotic organisms into our waters and, hopefully, permit the development of an overall program useful in preventing many

other aquatic releases. Most introduced species of fishes

have occurred through the importation and sale of

tropical pond and aquarium fishes. Many of the fish releases are caused by American citizens, who carelessly

dispose of their live fish in water systems near their

homes. Other tropical fish are accidentally and carelessly released by importers, dealers, and culturists who

do not maintain escape-proof ponds or otherwise do not

isolate their culture and maintenance activities. Other

releases, including some which may result in great ecological damage, have been through official activities of

the federal and state governments in their quests for

food, game, or forage species. The biology and identification of many of the exotic fishes imported into North

America that are used for commercial and sport fishing purposes, or for the aquarium hobbyist, are not

properly understood. Most official releases while satisfying certain political wishes have not served effective

biological purposes. The release of exotic fishes by fish

culturists has in all cases been made without regard to

the existing natural ecosystem. Stocking has been

carried out independently by state officials without

regard to the open waters in which the fishes are placed

and their free passage to many other states. Very little

attention has been given to the disease and public

health problems associated with the importation and

release of exotic organisms. Dangerous fishes such as

the piranhas and the Vandellia-like catfishes are released by individuals with complete ignorance of the

hazards involved. Official releases have been made of

species, such as those of Tilapia, with complete disregard of their competitive ability and aggressiveness.

The competitive ability of many introduced exotic

terrestrial vertebrates is well known and publicized.

Many exotic terrestrial releases have caused extinction

of large numbers of native forms. The extinction of

about 100 species of birds in which exotic introductions

played an important role, particularly in insular areas,

is treated by Greenway (1958) and Ziswiler (1967).

Our endemic fish fauna, particularly in southwestern

United States, is in many ways restricted to a confined

habitat, much like insular endemic species. Many of

these endemics could easily become extinct through

exotic introductions, or continued transplants of more

aggressive native species, as has been done in the past.

We reiterate Miller's (1964) statement that "the deterioration of the native fish faunas can also be plausibly attributed to the construction of dams, water

diversions, pollution, mining operations, use of toxic

chemicals, depletion of ground water, and the introduction of alien species."

The dangers to our native flora and fauna can arise

from many direct and indirect sources. Most of our
NUMBER 59 23

popular editorial articles such as the discussion in Life

by Jackson (1969) on "Threatened America" are insufficient to cover details of our threatened native

species. Man's encroachment directly on large natural

habitats, such as the Pine Barrens of New Jersey, may

lead to its destruction. In a similar manner the introduction of a few (or even one) aggressive exotic

aquatic organisms may alter the entire ecosystem.

The administration of the "Lacey Act of May 25,

1900," has proved inadequate in controlling the hazards resulting from the importation and use of live,

exotic aquatic life. The release of organisms is not

treated in this Act. Current national activities, such as

studies on environmental quality, or those concerned

in "The Wilderness Act," may be effective in maintaining some semblance of the natural environment,

but the problems of the release of organisms into the

very lands and waters preserved by official action are

unsolved.

The Bureau of Land Management, the United

States Department of the Interior, reviewed the advisability of introducing exotic big game species on

public lands and drafted guidelines in 1966 to be followed in considering such proposed releases. These

guidelines, presented by Craighead and Dasmann

(1966), and approved by the Secretary of the Interior

as public land policy, are presented here because of

their applicability to the control of releases in the

aquatic environment: (1) It should be objectively

determined that there is a real need for a proposed

introduction, and it should appear likely that the introduction will have desirable ecological, recreational,

and economic impacts. (2) The introduction should

fill a definite vacant ecologic niche, one not filled or

suitable for a native species. The probable existence of

such a niche should be reasonably well documented.

(3) An introduction should not be considered if there

is any danger, even apprehension, over the action leading to drastic reduction or regional displacement of

indigenous populations. Pending future study, the

introduction of exotic big game species on federal lands

should be governed by the necessity for protecting the

native biota and for preventing conflict with other

existing or proposed land uses. (4) Studies of the

ecology of the animal considered for release should

precede and guide introductions. Studies should, likewise, be made to determine the suitability of the proposed release area. (5) Every effort should be made to

study disease interrelationships and to take steps for

assuring effective quarantine resulting in disease-free

game. (6) Precautions against hybridization should be

taken by selecting animals that do not have close relatives in this country and rejecting those that do.

(7) Small trial introductions in suitable areas using

adequate numbers of stock should first be conducted on

an experimental basis under controlled conditions such

as in a fenced area (or for fishes, escape-proof, and

storm-proof ponds, etc.). The results should be carefully studied using the latest and best research methods.

An evaluation of this introduction should serve as a

basis for further action. (8) Before an exotic is introduced, positive assurance should be obtained that adequate control methods can be instigated to prevent

overpopulation or spreading. Further recommendations were that all exotics from national parks, wilderness areas, wildlife preserves, etc., be excluded and

that individuals or organizations be held liable for

damages caused by releases that become pests.

The resolutions and recommendations of the Washington Conference published in the Sport Fishing Institute Bulletin (Stroud, 1969a: 3-4) are repeated

below (with brief additions) in order that these guidelines may be reviewed with greater perspective because

of the data presented in this paper on the kinds of

exotic aquatic introductions, and their source, release,

behavior, and establishment.

Resolutions:

1. Open water release of exotic fishes.

Whereas, there is a possibility that benefits may result

from well-planned introductions, there is, however,

continuing possibility of intentional releases of undesirable exotic fish species in North American waters,

resulting from indiscriminate importations and related

ill-informed actions because of insufficient taxonomic

and ecologic evaluations, and the consequences of such

releases to the fishery resources of North America may

well prove disastrous;

Be it herewith resolved, that the Conferees on Exotic

Fishes and Related Problems, meeting this 19th day

of February, 1969, in Washington, D.C., and representing the American Fisheries Society and the American

Society of Ichthyologists and Herpetologists, as well as

a broad spectrum of user and governmental interests,

do strongly recommend that each state, province, or

federal agency, or academic, scientific, commercial

groups, and individuals, should voluntarily submit to

a Joint Committee on Introduction of Exotic Fishes

and Other Aquatic Organisms, all proposals to in-
24 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

troduce into open waters any exotic species for prior

evaluation and recommendation before consummating

such introductions;

Be it further resolved, that the said Joint Committee

shall, with their concurrence, be advisory to the International Association of Game, Fish and Conservation

Commissioners and shall include membership representation from the United States, Canada, and Mexico,

the Chairman of the Names of Fishes Committee of

both the American Fisheries Society and the American

Society of Ichthyologists and Herpetologists, and, in

addition, include broad representation of the various

concerned disciplines, government agencies, user interests, etc., such as are reflected in the present conference,

as shall be jointly appointed by the two societies sponsoring this conference;

Be it further resolved, that said Committee shall, as

first order of business, compile and cause to be publicized, a list of exotic species of fishes and other aquatic

organisms considered to be undesirable for import into

North America other than for scientific and educational purposes. (The American Fisheries Society,

May-June Newsletter, 1969, vol. 13, no. 61 carried the

report from President Elwood A. Seaman announcing

Dr. James E. Deacon, University of Nevada, Las

Vegas, as the Chairman of the Exotic Fishes

Committee.)

2. Delayed release of grass carp.

Whereas grass carp are now present in several

hatcheries, fish farms, and experimental facilities in the

United States, and there is considerable doubt as to the

desirability of releasing this species into the waters of

North America;

Be it resolved, that the Conference on Exotic Fishes

and Related Problems meeting this 19th day of February, 1969, in Washington, D.C., and representing the

American Fisheries Society and the American Society

of Ichthyologists and Herpetologists, as well as a broad

spectrum of users and governmental interests, do recommend that no further releases of grass carp be made

into the open waters of North America until the proposed Joint Committee on Introduction of Exotic

Fishes and Other Aquatic Organisms has an opportunity to study the matter;

Be it further resolved, that the conferees recommend

that all agencies do not release grass carp in the

interim.

3. Effect in country of origin.

Whereas, in excess of 64 million fishes were imported

into North America in 1968;

Be it resolved, that the conferees express their concern over the possible impact of the removal of these

organisms on the biota of the countries of their origin,

which was brought most forcibly to attention with particular regard to Latin American countries.

Recommendations:

1. The conferees recognized widespread concern

about the effects on natural ecosystems of the rather

widespread practice, past and present, of transplanting

species native to North America. In some situations

such transplants may have effects comparable to those

resulting from the introduction of exotic species.

The conferees urged that all agencies treat such

transplants as matters for serious study, for careful

planning and, where adjacent jurisdictions are involved, as matters for consultation with those agencies.

In cases of transplants where exotic species are involved, the conferees further urge consultation with

the proposed Joint Committee on Introduction of

Exotic Fishes and Other Aquatic Organisms.

2. The conferees recommend that no living fishes

or other aquatic organisms be imported except under

a Federal license or permit to the importer and that a

suitable license or permit be issued by the appropriate

government agency to each importer. The specific purpose is to establish his responsibility for the protection

of the native fauna of the recipient country. It is recommended that irresponsible activities, as determined

by the government agency, shall result in the suspension or revocation of said license or permit. The conferees further recommend that each State or Province

consider the development, continuation, and/or enforcement of similar regulations.

3. The conferees recommend that, after consultation with the proposed Joint Committee on Introduction of Exotic Fishes and Other Aquatic Organisms,

the appropriate federal governments limit the number

of approved Ports of Entry in order to help control

the introduction of exotic species in North America.

(There were 279 Ports of Entry in 1968.)

4. The conferees strongly recommend that the appropriate government agencies augment their current

inspection and enforcement service with a competent

identification service in order to accurately determine

the composition of the importations of exotic species

of fishes and other aquatic organisms and thereby assist
NUMBER 59

the aquarium and bait fish importers to comply with

State, Provincial, and Federal regulations.

5. The conferees recommend that agencies and individuals maintaining fishes and other aquatic organisms initiate and maintain adequate safeguards

against accidental release of nonindigenous organisms.

6. The conferees recommend that the government

agencies and professional organizations work with the

importers of exotic fishes and fish farmers in developing literature to point out and publicize the dangers

inherent in unauthorized releases of exotic fishes and

other aquatic organisms, and that this industry assist

in the dissemination of this information to their

customers.

Recommendations are of little value if they receive

no intelligent and timely implementation. The "Joint

Committee on Introduction ... " should be cognizant of the various recommendations in forming guidelines useful to the respective governmental agencies in

enacting and enforcing reasonable and effective measures that will assist in curbing the senseless tide of North

American animal and plant invasions. There is a great

task before the official agencies responsible for control

of traffic involving the importation of living organisms.

There may be no fool-proof set of regulations that will

prevent release and establishment of alien species. But

we can try to curb the flow of traffic in a manner agreeable to all involved individuals. The recent prohibiting

of entry of the catfish family Clariidae {Federal

Register, volume 34, number 158, 19 August 1969)

other than by permit is a useful regulation, and if it

had been enacted a few years earlier, it might have

prevented the establishment of the destructive walking

catfish in Florida. Entry of other undesirable aliens may

not be dealt with so easily. If we did "blacklist" several

of the harmful characins and cichlids from importation by law, identification must be planned at several

hundred possible ports of entry. The problems of control are immense, and it may require extensive, educational programs similar to those related to land and

water conservation. The public should be thoroughly

informed of the dangers and damages that release of

their home aquarium animals may cause. They should

be informed of the damage already done to the world

environment through introductions. Ziswiler (1967)

showed a remarkable positive correlation when he compared extinctions with increase in the world human

population. The only real safeguard toward the pre25

vention of unnecessary releases may be a well-informed

public respectful of its environment and natural heritage, accomplished through effective, diverse educational activities. The fact that outcries against the walking catfish in Florida have hastened its establishment

and popularity elsewhere and that current efforts to

eliminate the destructive African land snail, Achatina,

in Miami may be frustrated by curiosity seekers, emphasizes the importance of education. Cooperative

national and state study teams might be useful in pinpointing developing hazards associated with the importation of living organisms and they could signal

attention to harmful imports, and possible dangerous

releases and transplants. Study and evaluaion of proposed introductions probably should not rest with any

one agency, for some of them already bear responsibility

for our current problems.

Acknowledgments

We generously acknowledge the participants of the

Washington Conference—for we have freely borrowed

information discussed before the conferees—and the

encouragement received from many conferees to complete this manuscript. We are especially grateful to:

Catherine H. Robins, University of Miami, for reading the manuscript and for providing the section on

Marisa and Achatina; Neil Hotchkiss, Patuxent Wildlife Research Center, for providing a list of non-native

water plants now growing wild in North America; E. J.

Crossman, Royal Ontario Musuem, for information

concerning Canadian fish introductions; to Martin L.

Wiley, Chesapeake Biological Laboratory, for helpful

suggestions in reading the manuscript; and to the following for providing various information: James E.

Bohlke, Academy of Natural Sciences, Philadelphia;

Earl S. Herald, Steinhart Aquarium; Joseph P. E.

Morrison, National Museum of Natural History; and

Kermit E. Sneed, Fish Farming Experimental Station,

Stuttgart, Arkansas.

Reeve M. Bailey, Chairman, Committee on Names

of Fishes, American Fisheries Society and the American

Society of Ichthyologists and Herpetologists, provided a

provisional list of fishes introduced and established in

the United States and Canada.

This paper represents Contribution No. 1207, by C.

Richard Robins, from the Institute of Marine and

Atmospheric Sciences, University of Miami.
26

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