Mongolia North Korea Afghan- China South Japan istan Korea Iran SnakeheadsNepal Pakistan − (Pisces,India Channidae) PACIFIC OCEAN A BiologicalMyanmar Synopsis Vietnam and Risk Assessment Philippines Thailand Malaysia INDIAN OCEAN Indonesia Indonesia U.S. Department of the Interior U.S. Geological Survey Circular 1251 SNAKEHEADS (Pisces, Channidae)— A Biological Synopsis and Risk Assessment By Walter R. Courtenay, Jr., and James D. Williams U.S. Geological Survey Circular 1251 U.S. DEPARTMENT OF THE INTERIOR GALE A. NORTON, Secretary U.S. GEOLOGICAL SURVEY CHARLES G. GROAT, Director Use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Geological Survey. Copyrighted material reprinted with permission. 2004 For additional information write to: Walter R. Courtenay, Jr. Florida Integrated Science Center U.S. Geological Survey 7920 N.W. 71st Street Gainesville, Florida 32653 For additional copies please contact: U.S. Geological Survey Branch of Information Services Box 25286 Denver, Colorado 80225-0286 Telephone: 1-888-ASK-USGS World Wide Web: http://www.usgs.gov Library of Congress Cataloging-in-Publication Data Walter R. Courtenay, Jr., and James D. Williams Snakeheads (Pisces, Channidae)—A Biological Synopsis and Risk Assessment / by Walter R. Courtenay, Jr., and James D. Williams p. cm. — (U.S. Geological Survey circular ; 1251) Includes bibliographical references. ISBN.0-607-93720 (alk. paper) 1. Snakeheads — Pisces, Channidae— Invasive Species 2. Biological Synopsis and Risk Assessment. Title. II. Series. QL653.N8D64 2004 597.8’09768’89—dc22 CONTENTS Abstract . 1 Introduction . 2 Literature Review and Background Information . 4 Taxonomy and Synonymy . 4 Common Names . 6 Description and Distinguishing Characteristics. 6 Native Distribution . 7 Biology and Natural History . 8 Associated Diseases and Parasites . 13 History in Fisheries and Aquaculture. 15 History of Introductions . 17 Eastern Hemisphere . 17 Western Hemisphere . 19 Uses. 24 Aquarium Trade. 24 Live-Food Fish Trade . 26 Biological Control . 28 U.S. Importations . 28 Regulations as of July 2002 . 31 Potential Range . 32 Risk Assessment Process. 33 Rating Elements of Risk Model. 34 Organism Risk Potential. 40 Species Accounts . 41 Channa amphibeus . 43 Channa argus . 45 Channa asiatica . 53 Channa aurantimaculata . 55 Channa bankanensis . 57 Channa baramensis . 59 Channa barca . 61 Channa bleheri . 63 Channa burmanica. 65 Channa cyanospilos . 67 Channa gachua . 69 Channa harcourtbutleri . 73 Channa lucius . 75 Channa maculata. 77 Channa marulioides. 81 Channa marulius . 83 Channa melanopterus . 89 Contents III Channa melasoma. 91 Channa micropeltes. 93 Channa nox . 99 Channa orientalis . 101 Channa panaw . 105 Channa pleurophthalma . 107 Channa punctata. 109 Channa stewartii. 113 Channa striata . 115 Parachanna africana . 121 Parachanna insignis . 123 Parachanna obscura . 125 Acknowledgments . 127 References. 129 FIGURES 1. Depiction of the Chinese snakehead, Channa asiatica, by Walt Disney Productions in 1959 . 3 2-6. Maps showing: 2. Native distribution of the family Channidae . 8 3. Introductions of snakeheads in the Eastern Hemisphere . 17 4. States where snakeheads have been collected from open waters, were cultured prior to August 2002, or are established . 20 5. States prohibiting possession of live snakeheads as of November 2002 . 32 6. Thermal range of snakeheads (Channidae) based largely on native range of distribution . 33 TABLES 1. Currently recognized species of the family Channidae . 5 2. Parasites of northern snakehead (Channa argus) . 14 3. Species of the family Channidae currently known to be cultured for food 16 and/or aquarium fish trade . 4. Snakeheads of interest to aquarists in the U.S. 25 5. U.S. importations of live snakeheads (Channidae, all species) during 29 1997-2002 . 6. Origin of snakehead shipments (Channidae, all species) during the 30 past 5 or more years. 7. States prohibiting snakeheads as of July 2002 . 31 IV Contents CONVERSION FACTORS, ACRONYMS, and ABBREVIATIONS Multiply By To obtain centimeter (cm) 0.3937 inch meter (m) 3.281 foot kilogram (kg) 2.2046 pound Degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows: °F = 1.8 x (°C + 32) FAO Food and Agriculture Organization of the United Nations FFWCC Florida Fish and Wildlife Conservation Commission U.S. United States USGS U.S. Geological Survey ppm part per million S$ Singapore currency $ United States currency Unless otherwise stated in this report, measurement of fish refers to total length, defined as the measurement made from the tip of the snout to the posterior tip of the caudal or tail fin. Standard length refers to the measurement made from the tip of the snout to the base of the caudal fin. Contents V VI Contents SNAKEHEADS (Pisces, Channidae)— A Biological Synopsis and Risk Assessment By Walter R. Courtenay, Jr., and James D. Williams ABSTRACT Snakeheads (family Channidae) are airbreathing freshwater fishes containing two genera, Channa with 26 species native to Asia, Malaysia, and Indonesia; and Parachanna with 3 species native to tropical Africa. Some snakeheads are small, reaching about 17 centimeters, but most are much larger, the largest reported to be 1.8 meters in length. All are considered thrust predators with most being piscivorous as adults. A few of the smaller snakeheads and colorful juveniles of some larger ones have been available to hobbyists through the aquarium fish trade. Several species are highly valued as food fishes within parts of their native ranges, especially in Asia where they are an important part of capture fisheries and aquaculture. Because of these uses by humans, introductions far beyond native ranges have occurred. One Asian snakehead has been established in Oahu, Hawaii, since before 1900. Another species was discovered established in southeastern Florida in 2000, and a third in a pond in Maryland in 2002. Others have been captured from natural waters of the United States without evidence of reproduction and likely represent released aquarium fishes. That snakeheads at or near sexual maturity were being sold alive in ethnic food markets raised fears that they could be introduced into novel waters. These concerns led to this study on the biology of snakeheads. A risk assessment is included that examines environmental and related aspects of snakehead introductions. 1 INTRODUCTION Snakeheads (family Channidae) are airbreathing freshwater fishes containing two genera, Channa, native to Asia, Malaysia, and Indonesia, and Parachanna, endemic to tropical Africa. Taxonomy of these fishes is in flux, but leading authorities on snakehead systematics currently recognize 26 species of Channa and 3 of Parachanna. A few snakeheads are small, reaching about 17 centimeters; most, however, are much larger, the largest reported to be 1.8 meters in length. All are considered thrust predators with most being piscivorous as adults. Within.