THE affinis

Adult male (above) and adu lt female (below) Cambusill affinis affinis. Courtesy of Or. L ouis .4. Krumholz .

UNITED STATES DEPARTMENT OF THE INTERIOR AND WILDLIFE SERVICE BUREA U OF COMMERCIAL FISHERIES Fishery Leaflet 525 (

THE MOSQUITOFISH, Gambusia affinis

By Lola T. Dees Branch of Reports Divi ion of Resource Development

CONTENTS

Page Int roduction. . • . . • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 1 Range. . • • • • • . • . • • . . • • • • • • • • • • • • • • . • • • • • • • • • • • • • • • • • 1 Fo reign introductions. . • • • • . • • . • . • • • • • • • • • • • • • • • • • • • • • • • 2 Habitat . • . • . • • • • • • . • . . • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 2 Li fe history. • • • • • • • • . • • • • • • • • • • • • • • • • • • • . • • • • • • • • • • • • 2 Description •••••••••••••••• •••.•••••••••••.••. 1 • • • 2 Food . • . . . • • • • • • • • • • • • • • • • • • . • • • • • • • • • • • • • • • • • • • 3 Reproduction . • • • • • • • • • • • • • • • • . • • • • • • • • • • • • • • • • • • • • 3 TIle young . • • • • • . • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 3 Enemies . • • • • • • . • • • . • • • • • • • • • • • • • • • • • . • • • • • • • • • • • • • • 3 Cu lture. • • • • • • • • • • • • • • . • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 3 Dealers . • . • • • • • • • • • • • • • • • • • • • • • • • . • • • • • • • • • • • • • • • • • 4 References . • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 4

INTRODUCTION Several of GaInbusia, of t he Cyprinodontes and the Poe­ An insignificant-looking little fish, Cant ­ ciliidae, occur in the warm or tropical i",ir1 '1 r(ini" i s largely responsible for mak­ areas of the United States, Mexico, and ing many parts of the world livable for man. Central AInerica. The species used to con­ In 1918 the great value of Gambusia as an trol mosquitoes is Gambusia affinis (Baird and eradicator of the aquatic stages of the Girard). This species has two subspe­ was first clearly shown when cies: Gambusia a.ffi71is flffinis and Gambusia affinis these fish were used at Camp Hancock in holbrooki. They are known also as mosquito­ Augusta, Georgia. fish, because they feed on mosquito larvae, GaInbusia eat aquatic l arvae of mos­ and as topminnows , since they are shaped quitoes, including the species that cause like a and feed at the surface of the malaria and yellow fever . One female, water. 2 1/ 3 inches long, ate 225 large mosquito larvae within 1 hour, and a male, 1 1/4 RANGE inches long, ate 28 larvae during the same period. At birth Gambus ia commence feed­ The natural r ange of G. a. affinis extends ing on newly hatched mosquito l arvae, which, along the Gulf of Mexico coast from the when i irst hatched, are threadlike mouth of the Rio G r ande as far west as a l most microscopic in size. Bay St . Louis, M i ssissippi, and through the If the r e are no aquatic plants or debris Mississippi River a nd its tributary waters (whlch furni sh hiding places for mosquito as far north as central . Introduc­ larvae) or predators, GaITlbusia will con­ tions have extended the range of G. a. affinis trol a mosquito population . Experiments northward, even into Canada. Theyhave been extending over two summers in Michigan successfully introduced into Arizona, Cali­ r evealed that Gambus i a reduced mosquito fornia , northern Illinois, , Kansas, p r oductlon 80 to 95 percent in ponds where Massachusetts, Michigan, Missouri, Ne­ natural conditlOns we r e simul ated (Krum­ vada, New Jersey, New Mexico, New York, holz. 1948b) . When introduced into a fish­ Ohio, Pennsylvania, Utah, Washington, Wis: free pond at the helght of the mosquito consin, and probably other States. breedIng season, these mosquitofish brought The other sub s p e c i e s, G. a. holbrooki, about an 80 pe rcent reduction in mosquito ranges from southern New Jersey along the rep roductlon wlthln a week. Atlantic coast to the Florida Keys and along ( 2 the Gulf of Mexico coast as far as Apa­ sewage . In this enviro nm.e nt they stayed at lachicola, Florida. It is not hardy enough the surface at all tim.es a n d appeared to b e to survive northern winters (Wascko, 1950) . respiring at the a irwate r interface.

FOREIGN INTRODUCTIONS LIFE HISTORY Both subspecies have been introduced into m.any foreign lands (Hildebrand, 1931; Description Krum.holz, 1948b). In about 1920 the Inter­ national Red Cross asked the United States The two subspecies are alm.ost identical Bureau of Fisheries for brood stocks of in color, fo r m. , and s ize . While the color is Gam.busia for Italy and Spain. The ship­ usually olive o r dull s ilvery, darkest on m.ent of G. a. holbrooki from. Augusta, Georgia, the head and lightest on th e belly, it varies to Italy failed . However, the fish of the according to the cha r a cter of the habitat. sam.e species sent to Spain arrived in Individuals livin g in ditches and drains are fairly good condition and m.ultiplied rapidly. usually pale , a nd those in dark-colored Within a year or so Italy obtained a brood wat er of s w am.p s are dark green, with a stock from. Spain but the fish were unable d i stinct purple b ar b elow the eye . There to withstand the winters in northern Italy. i s f r equently a fine dark line along the In1927, G.a. affinis, hardierthan G. a. holbrooki, s id e s , s om.etim.es a dark blotch below the were shipped from. Carbondale, Illinois , e y e ; a d a r k purplis h blo tch is usually pres­ to Trieste, Italy. These fish survived and e n t on t h e side a bove the vent in the fem.ale. m.ultiplied. The dorsal f in has 2 or 3 transverse rows From. the original intr oductions into of f ine b l a ck spo ts. The anal fin in the Spain and Italy, Gam.busia h a v e been d i s ­ f em.a le i s d ark-edged; the caudal fin has 3 tributed to nearly all south European coun­ o r 4 irre gular transve rse rows of dark tries and to Germ.any and Austria. They s p o ts; the o ther fins are dusky. The fins were introduced also into Palestin e, the a re sm.a ll, and the scales large in propor­ Philippine Islands (from. thence to China tion to the size of the fish. Dark pigm.ent and Japan), , Thailand, Union of outlines each scale . South Africa, Haw aii an Isl ands , th e We st There are a few differences between the Indies , and Argentina. F r om. these pla c e s two subspecies. G. a. holbrooki, has 8 rays in of intr oduction, Gam.busi a sprea d f ar and the d orsal fin, and the third ray of the wide u nti l they have becom.e a lm.ost cos ­ gonopodium. (sexual organ) shows a deep m.opolitan in the warm.er secti on s of the split when exam.ined unde r the m.icro·· world. scope (Innes, 1956) . G . (/. affinis has only 7 rays in the , and the split in the HABITAT third ray of the gonopodium. is lacking. The s exes of the sam.e species differ in The two subspeci es are found in m. any fo rm. and structure . The fem.ale has a types of water whose tem.perature m.ay d eeper body than the m.ale. Fem.ales, whose range from. 400 to 1000 F . They flour ish m. axim.um. size depends on the fertility of in sluggish and standing water, f r esh, th e wat er in which they live, grow through­ brackish or m.arine , clear or m.uddy, deep out life and m.ay reach a length of 2 1/2 or shallow, open or overgrown, but p r efer inches . Males grow little after the gono­ clear shallow water . They probably seek podium. is fo rm.ed (Turner, 1941) and do shallows to escape lar ge p r edacious fish, n ot exc eed 1 1/2 inches. The fem.ale has a such as largem.outh black bas s , and t o feed s m. a ll, r ounded anal fin with the rays con­ on m.osquito larvae , which a r e m.or e nected b y a m.em.b rane, and the m.ale has num.erous there than elsewhere. the th ird , fourth, and fifth anal fin rays Mosquitofish occur in ditches and pool s unit ed a nd lengthened to fo rm. the gono­ containing either hard or bracki sh wat er. podium. (picture on cover). Com.m.on characteristics of these envir on­ G e ne r a lly m.os quitofish, which are rela­ m.ents are a relatively high m.ineral content tively f r ee from. disease, die during the in the form. of dissolved solids and an sum.m.e r in which theym.ature . Som.e fem.ales abundant supply of plant and anim.al food . m.ature in t h eir first sum.m.er of life; others They thrive too in artesian well dischar ges , do not m.atu re until their second sum.m.e r cisterns, water tanks, potholes , and r a in and die w h e n ab out 15 m.onths old . Le s s barrels. They have been known to liv e also har d y tha n f e m.ales, m.ales die at an earlier in an open m.unicipal septic tank containing age.

3 Food ( While adult Gambusia eat princip ally larvae and nymphs of aquatic insects, they also eat plant food such as diatoms, desmid s 1 and fil amentous algae . The young feed mostly on plankton (the passively floating or weakl y swimming and plant life). Reproduction Gambusia are OVovlvlparous ; that is, a female p r oduces eggs that hatch within her body. The male fertilizes the eggs in the female b y using the gonopodium to deposit sperm in her genital tract . A female is a b l e to produce several broods of y oung a fter being fertilized once. Studies of 30,093 specimens of G . a . affinis collected during 1938, 1939, and 1940 from e ight ponds in northeastern and central Fignre 1.--Pregnant female Cambus ia a{{illis a{{inis. The brood Illinois reveal much about their breeding of 79 were removed late r. The yo lk s ac has been habits (Krumholz , 1948b) . Males matured completely absorbed, and the embryos are nearly fully ueveloped and n il. at smalle r sizes and at slightly earlier ages abom ready for bi Co urtesy of Dr. Louis A . Krumholz. than females. Some females in two ponds became sexually mature for the fi r s t time early in their secon d summer of life when 8 to 10 months old and 1 t o 2 inche s long. They reproduced fo r 10 to 15 weeks , u sually bearing 3 to 4 broods . The offspring of their first a nd possibly their second brood became s e xually mature during their f i rst summer of life when 4 to 6 weeks old and a bout 1 inch long. They reproduced for 4 to 10 w e e ks, generally bearing onl y 1 or 2 broods . In the first b r ood, m ales and females were in almost equal numbers, but in suc­ ceeding broods the f emales g r adually out­ numbe r ed the males . The average number of y ou ng in a bro od decreased as the length of the mother increa&ed. Some metabolic f acto r, coincident with the approaching end of t he reproductive season, may control th e number of young.

The young Figu re 2.--Adulr male (above) and adult female (below) Cambusia Fe rtilized eggs hatch in 21 to 28 d ays. affinis affinis and young. The young are about 4 hours old. Within several hours a female expels from Co urtesy of Dr. Louis A. Krumholz. a few to several hundred live young (figs . 1. and 2) . About three-eighths of an inch long ENEMIES at b i rth, they are well developed and c o m­ Bi r ds , frogs , lar ge fish , and water snakes pletely formed . They have prominent black dev our Gambusia. e yes and are often uniformly yellowish. The fins are dusky, and the caudal fin usually has a cross series of dots. At birth CULTURE t hey are abl e to swim. Gambusia c a n be easilyb r ed in aquariums Growth of mosquitofish is rapid, depend­ at w ate r t emperatures of about 750 F. ing on the food supply and to a lesser extent While t hey p r efe r liv e foods , they will eat o n the water temperature. prepar ed foods . ( 4 They should not be m ixed w ith othe r 1925. A study of he op minnow Gn II 10 species in aquariums, because Gambusia 1,(Jlb o(Jkz In Its rela Ion 0 mo qUI 0 will often attack othe r fish by nipping cont rol. U. S. Pubhc Health Se rVlc , p i eces from the fins and tails. Bulletin No . 153, 36 p . In nature, female Gambusia seldom eat 1931. Gambus la 10 foreign land SCI- their young because a good supplyofnatural ence, vol. 74, no . 1930, p. 655- food is usually available . In aquariums, howeve r, the young mus t hide among the Howard, H. H . plants to escape the mother. For protec­ 1920. Use of top minnow (f, I b" J 0 'Inl ) tion' the young should be separated from as an agent In mosqui 0 con rol the adults . There a re two methods to Rockefelle r Foundation Inte rna lonal accomplish this . One is to provide the young Health Board, Report No. 7486, 59 p with hiding plac es, such as dense growths of plants, and the othe r is to us e a pa rti ­ Inne s, Willi am T. tion to separate the mother from her off­ 1956. Exotic aquarium . 19th ed . spring (Innes, 1956). Innes Publishing Company, Phila­ delphia, Pennsylvania, 541 p . DEALERS Krumholz, Louis A . Most tropical fish dealers either have 1944. Northward acclimatization of th Gambusia in stock or can order them. western mosquitofi sh, GnTllbu. ia n fIn" a((ini, Copeia, 1944, no . 2, p . 82-85 . REFERENCES 1948a. The mosquitofish, Gambus la, es­ tablished in the Great Lakes reglOn. Barnickol, Paul G . Copeia, 1948,no. 2,p. 144 . 1941. Food habits of Cambusia a((ini from 1948b . Reproduction in the w te rn Reelfoot Lake, Tennessee, with spe­ mosquitofish, Gambusin nffini nfflnl. cial reference to malaria control. (Baird &. Girard). and its use In Report of the Reelfoot Lake Bio­ . Ecological Mono­ logical Station, vol. 5, p . 5 -13. graphs, vol. 18, no . I, p . 1-43 .

Gerberich, John B . Mail, G . Allen. 1946. An annotated bibliography of [298] 1954. The mosquito fish Gambu. in nff n papers relating to the control of (Baird and Girard) in Alberta . Mos­ mosquitoes by the use offish. Ameri­ quito News, vol. 14, no . 3, p . 120 . can Midland Naturalist, vol. 36, no . 1, p . 87-13l. Moore , J . Pe rcy. 1922. Use of f ishe s for control of mos­ quitoes in northern fresh wate rs of Hess, A. D., and Clarence M . Tarzwell. the United States . Report of the U. S. 1942. The feeding habits of Cambusia a((ini Commissioner of Fisheries for 1922, a(finis, with special reference to the app. 4, 60 p . malaria mosquito, .4nophele au (uiri­ maculatus. Ame rican Journal of Mosquito News . Hygiene, vol. 35, no . I, p. 142-1 51. 1960 . The ability of the top minnow, Cambll in nffini~ (Baird & Gira rd) to reproduce and ove rWlnte r In an ou - Hildebrand, Samuel F . door pond at Winnipeg, ManItoba, 1921 . Top in relation to malaria Canada. Its vol. 20, no I, p . 5 - 5. control, with notes on their habits and distribution. U. S . Public Health Phillips, W . J. Se r vice , Bulletin No . 114, 34 p. 1930. Use of fishes for control of mo - quitoes . ew Zealand Journal of 1922. Fishes as guardians of health . Science and Technology, vol. 12. Outlook, vol. 130, no . 12, p .465-467. no . I, p . 19 - 20 .

5 Rees, Don M . Rice , Lucile A . 1934. Notes on mosquito fish in Ut ah, 1941 . Ga mbusia affinis in r elation to food ( G(1.mbusia affinis (Baird and Girard) . habits from Reelfoot Lake, 1940, Copeia, 1934, no . 4, p. 157-159. w ith special emphasis on malaria control. Report of the Reelfoot Lake 1945a. Supplemental notes on m o squ ito B iologi cal Station, vol. 5, p. 77-87 . fish in Utah, Gambusia affini 8 (Baird and Girard) . Copeia, 1945, no. 4, Tur ner, C . L . p. 236. 1941. Morphogenesis of the gonopodiurn in Gambusia affinis affinis . Journal of 1945b. The utilization of fish by amos­ Morphology, vol. 69, no. 1, p. 161- quito abatement district; their ef£ec­ 185. tiveness and limitations. Proceed­ ings of the Thirty-Second Annual Wa.cko, Harold. Meeting of the New Jersey Mo. quito 1950. Gambus ia in no rthwea te rn Ohio. Extermination Auociation, p. 211- Ohio Department of Natural R e ­ 216. s ources, Bulletin No. 240, 4 p.

MS #1093

5 5 915 ( 6