Introduction:The side effects of insecticide which are used forcontrolling the vectors of human diseases are in increase.Manipulating or introducing a predator into the ecosystemmay provide sustained biological control of pest populations(Ayala et al., 2007). Biological control of mosquitoes is animportant component. Naturally there are several predators ofthese insect both as larvae and adults (Shannon & Paul ,2011). Some larval predators include several species ofbeetles, fish, birds and bats. (Gerald et al., 2012). MosquitoFish (Gambusia affinis) are a great way to reduce mosquitopopulations before they become a problem such astransferring malaria disease. Gambusia can be introduced intostreams, lakes, irrigation systems, drainage systems, sloughs,ponds, reservoirs, cisterns, shallow wells, animal wateringtroughs, and seepage areas (Purcell, et al., 2010).2
Mosquito fish have large heads that are flattenedon the upper surface, and their eyes are large relativeto their bodies . The female is bigger than the maleboth in length and girth. (Gerald et al., 2012).Mosquito fish do not lay eggs, they give birth towell-developed active young. Consequently onlyone pregnant female is needed to start a newpopulation. The anal fin on adult females resemblesthe dorsal fin while the male has a modified anal-fin(bottom) for sperm transfer. This pointed fin isreferred to as a gonopodium and is used to depositsperm inside the female. (FAO, 2008). 4Fish Description:
Fish External Anatomy:5GonopodiumFigure(1): male & female distinguish.Source: Boyer et al., (2008).
Table (1) : Stocking rate ofMosquitofish6Small(250m2)Average(1000m2)Big(2000m2Very large(4000m2Pond Size203040-50100No. of fishSource: Robert, et al.,(2013).
Mosquito fish are hardy. They can survive inwaters with:1. Low levels of dissolved oxygen,2. High salinities (up twice that of sea water) and3. Temperatures (between 0.5-42˚C).4. Most common in lower reaches of streams.5. They prefer brackish water with little to no flow(static waters) such as vegetated ponds and lakes,backwaters and quiet pools of streams. (Preston et al.,2012)6. The fry are independent from birth and often seekrefuge among submerging vegetation.Ecology & life history:7
1. Size at birth: (0.8) cm male, (0.9)cm female.2. Reproductive strategy:ovoviviparous (live bearers).3. Sexual maturity: male (43-62)days. Female (21-28) days.4. Brood: 300 fry, usually less than60.5. Brood replications: up to (5broods/year) under favorableconditions.6. Gestation period: (16-28) day.7. Lifespan: 1-1.5 year.Reproduction of fish8Figure(2): male gonopodium.
Mosquito Fish CareWhen you get your fish home, you will need to acclimate the fish to theirnew pond (or other site) by placing the container with fish directly into thewater for 10-15 minutes or until the pond water and the containers water arenear the same temperature. Then release the fish.These fish are opportunistic feeders in that they eat just about anything.During the warmer months they usually do not need supplemental feeding.However, if there is no natural food present (i.e. new pond), some artificialfood, such as crushed dry food will be necessary for fish survival. (Purcell, etal., 2012).Mosquito fish prefer temperatures between (25-30˚C) , and are often foundin the shallow un shaded region of a pond. Algae in limited amounts will notharm fish but may become unsightly. Most pet stores have or can secure foryou a preparation with directions for use in fish pools to control algae.(Geraldet al., 2012)These hardy fish should survive through several seasons and reproduce youfor your help in mosquito control.10
Table (2): Comparingbetween sexes:Characteristics Male FemaleMax Size 5.5 cm 7.5 cmColor Dull grey Grey, patches of bright colorsDiet Mosquito larvae, up to 100 perday, zooplanktonMosquito larvae, up to 100 per day (pregnantconsume more) , zooplanktonHabitat Fresh/salt water, above 5˚C Fresh/salt water, above 5˚CReproduction Mates 4-5 times per year Live bearing, 4-5 broods per yearLocation Fairly warm rivers or lakesacross globeFairly warm rivers or lakes across globe12Source: Purcell, et al., (2010).
Figure(4): Malaria Global Distribution.Source: (Gkenas, et al., 2012).13
Figure (5): malaria transmission cycle.Source: (Mendenhall, et al., 2012)14
Fish adaptation:1. Larvivorous fish.2. Very easily adaptable.3. Mosquitofish are particularly difficult to control.4. Very fecund, they disperse rapidly throughconnected stream networks, and they are stillcommonly used as a biological control agent formosquitoes. (Gerald, et al., 2012).15
Disadvantages of mosquito fish:1. Aggressive feeders.2. Frequently attack native fish, nipping at theireyes and fins.3. Gambusia also competes with native fish forfood & space. (Alcaraz, & García, 2008).4. Have been known to eat native fish eggs.5. A single gambusia female produces severalbroods a year which can reach sexual maturity inas little as 3-4 weeks. (Robert, et al., 2013).16
17Mortalities by Malaria annually.Source: (Preston, et al., 2012).
ConclusionTherefore, this method of controlling mosquitoescontribute a lot of beneficial effects to us especially to themajor problems which involve mosquitoes harmful effectsto humans such as:1. Nuisance mosquitoes: bother people around homes orin parks and creational areas. (Gkenas, et al., 2012).2. Economically important: mosquitoes reduce realestate values, adversely affect tourism and relatedbusiness interests, or negatively impact livestock orpoultry production. (Robert, et al., 2013).3. Public health: is the focus when mosquitoes arevectors, or transmitters, of infectious diseases. Such asmalaria . 18
Alcaraz, C. and García, B. E. (2008). Salinity mediates the competitive interactions betweeninvasive mosquitofish and an endangered fish. Oecologia 155, 205-213.Ayala, J. R.; Rader, R. B.; Belk, M. C. and Schaalje, G. B. (2007). Ground-truthing the impact ofinvasive species: spatiotemporal overlap between native least chub and introduced westernmosquitofish. Biological Invasions 9, 857-869.Bonney, B. (2013). Responses of Gambusia affinis to Changes in Hydrologic Regimes in WallerCreek, Texas -Department of Marine Science-College of Natural Sciencesfirstname.lastname@example.org. Pdf pp77-80.Boyer, M. C.; Muhlfeld, C. C. and Allendorf, F. W. (2008). Rainbow trout (Oncorhynchusmykiss) invasion and the spread of hybridisation with native westslope cutthroat trout(Oncorhynchus clarkii lewisi). Canadian Journal of Fisheries and Aquatic Sciences 65,658-669.Food and Agriculture Organisation of the United Nations (FAO) (2008). Cultured AquaticSpecies Information Programme – Cyprinus carpio (Linnaeus, 1758).http://www.fao.org/fishery/ culturedspecies/Cyprinus_carpio.Gerald, M.; Cynthia, H.; Mieu, N.; Stephen, S.; Gregory, T.; Michael, C. and Claudia, R. (2012).The use of Gambusia to control mosquito larvae in abandoned swimming pools: The NewOrleans experience. New Orleans Mosquito, Termite, and Rodent Control Board:73pp.Gkenas, C.; Oikonomou, A.; Economou, A.; Kiosse, F. and Leonardos, I..(2012). “Life HistoryPattern and Feeding Habits of the Invasive Mosquitofish, Gambusia Holbrooki, in LakePamvotis (Nw Greece).” [In English]. Journal of Biological Research-Thessaloniki :121-36.19References:
Mendenhall, C. D.; Daily, G. C. and Ehrlich, P. R.. (2012).“Improving Estimates of BiodiversityLoss.” Biological Conservation 151, no. 1 :32-34.Preston, D. L., Henderson, J. S. and Johnson, P. T. J.. (2012). “Community Ecology ofInvasions: Direct and Indirect Effects of Multiple Invasive Species on AquaticCommunities.” Ecology 93, no. 6 : 1254-61.Purcell, K. M.; Klerks, P. L. and Leberg, P. L. (2010). Adaptation to sea level rise: Does localadaptation influence the demography of coastal fish populations? J. Fish Biol. 77(6): 1209–1218. doi:10. 1111/j.1095-8649.2010.02727.x. PMID:21039500.Purcell, K. M.; Ling, N.; and Stockwell, C.A.(2012). Evaluation of the introduction history andgenetic diversity of a serially introduced fish population in New Zealand. BiologicalInvasions 14:2057-2065.Robert, D.; Jeffrey D.; Douglas, G.; Claudia, O. and Michael, R.(2013). Gambusiaaffinis effectiveness in New Jersey. Proceedings of the Eighty-Third Annual Meeting of theNew Jersey Mosquito Control Association, Inc.6pp.Shannon, B. M. and Paul, L. L. (2011). Influence of environmental stress on age- and size-at-maturity: genetic and plastic responses of coastal marsh fishes to changing salinities Can. J.Fish. Aquatic. Sci. Vol. 68.Wikipedia. (2012). Mosquito. Available from: http://en.wikipedia.org/wiki/Mosquaito .http://www.ryanphotographic.com/poecilidae.htm.http://catalog.digitalarchives.tw/Exhibition/Detail.jsp?OID=14711.http://www.bio.txstate.edu/~tbonner/txfishes/gambusia%20affinis.htm. 20References: