THE MOSQUITOFISH Gambusia 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 FISH 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 species of GaInbusia, of t he order Cyprinodontes and the family 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 mosquito 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 minnow 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 animals 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 Illinois. 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, Indiana, 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), Russia, 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 dorsal fin, 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 animal 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 embryos 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 fishes . 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 mosquito control. 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 minnows 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.
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