African Tilapia in Lake Nicaragua Author(S): Kenneth R

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African Tilapia in Lake Nicaragua Author(s): Kenneth R. McKaye, Joseph D. Ryan, Jay R. Stauffer, Jr., Lorenzo J. Lopez Perez, Gabriel I. Vega, Eric P. van den Berghe Source: BioScience, Vol. 45, No. 6 (Jun., 1995), pp. 406-411 Published by: University of California Press on behalf of the American Institute of Biological Sciences Stable URL: http://www.jstor.org/stable/1312721 . Accessed: 29/08/2011 17:58

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http://www.jstor.org African Tilapia in Lake Nicaragua

Ecosystem in transition

Kenneth R. McKaye, Joseph D. Ryan, Jay R. Stauffer Jr., Lorenzo J. Lopez Perez, Gabriel I. Vega, and Eric P. van den Berghe

L ake Nicaragua contains more (1.17 x 105 km2) flow into the Car- than 40 species of fish, in- ibbean Sea and discharge an im- cluding 16 recognized spe- Swift, aggressive mense amount of fresh water (ap- cies (Thorson 1976) of native management of tilapia proximately 2.6 x 1011 m3) and cichlids and additional undescribed suspended sediments along the 450 cichlids.1 The lake is also inhabited is needed to mitigate km of coast. Ten biologically rich by several large marine predators, estuaries, whose waters oscillate be- such as the bull shark (Charch- the negative impacts of tween fresh in the rainy season to arhinus leucas), sawfish (Pristis moderately saline during the dry perotteti), tarpon (Tarpon atlan- their introduction season, act as nursery areas for many ticus), grunt (Pomadasys spp.), and marine species. These highly pro- snook ductive fisheries a livelihood (Centropomus parallelus; cated in a tectonic which provide Thorson Eleven of the 16 depression, for the of the 1976). extends northwest from the mouth people region. Popula- cichlid are confined to San tions of of the fish species of the Rio San to the Gulf of many species which contains the Juan extend into Lake and Juan Province, Fonseca in the Pacific. The Nicaragua, lake The most depres- hence that occurs (Miller 1966). heavily sion also includes the smaller Lake any perturbation resources have tra- in one can exploited fishery called system severely impact been the native Managua (also Xolotlan). the other. In order for a coastal ditionally cichlids, Numerous rivers flow into these two upon estimated to constitute 58% to be effective, it currently but the Rio San management plan of Lake fish biomass. lakes, only Juan must both the estuarine Nicaragua's drains this into the Carib- encompass Lake 1), the system systems and Lake Nicaragua (Ryan Nicaragua (Figure bean Sea. The Rio San Juan passes largest (8264 km2) tropical lake out- et al. 1993). through the productive Atlantic side of Africa (Incer 1976), is lo- The Lake Nicaragua ecosystem is Coast-region of Nicaragua. This of Lake Nicara- currently undergoing major ecologi- ecosystem cal changes. An extensive stocking is, therefore, intimately con- Kenneth R. McKaye is a professor of gua program introduced African tilapia and fisheries and coor- nected with the Caribbean Sea and tropical ecology (genus Oreochromis) into the lake dinator of international research pro- adjacent coastal habitats. The most in the 1980s. Native cichlid D. is a re- popula- grams, Joseph Ryan faculty famous result of this connection is tions have declined as introduced search Lorenzo Perez assistant, J. Lopez the migration of a shark, known as invade lake areas. The col- is a research assistant, and Eric P. van tilapia the freshwater shark of Lake Nica- of one of the world's den Bergheis a professor of fisheries at which in is the Carib- lapse unique Labo- ragua, reality freshwater is imminent the Appalachian Environmental bean bull C. leucus. ecosystems Center for Environmental and shark, if corrective measures are not taken. ratory, The Caribbean Coast of Nicara- Estaurine Studies, in the University of gua is biologically one of the most Maryland System, Frostburg, MD Historical 21532, and Universidad Centroamer- productive and speciose systems in perspectives Gabriel the world 1992, et al. icana, Managua, Nicaragua. (Ryan Ryan Lake Nicaragua and the Rio San I. Vega is an ecology student at 1993). It receives a large amount of have attracted the atten- Centroamericana. Juan long the Universidad Jay yearly rainfall, estimated at 4-6 m. tion of the world due to their strate- R. Stauffer is a of Jr. professor ichthyol- Fourteen primary rivers, drain- location for an in- at the School of Forest Resources, gic constructing ogy ing 90% of the country's watershed teroceanic canal. Such a Pennsylvania State University, Univer- project sity Park, PA 16802. ? 1995 American would require deepening portions Institute of Biological Sciences. 1K. R. McKaye, personal observation. of the river and lake and cutting

406 BioScience Vol. 45 No. 6 . T6; ig,

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BRITIMECANAL CE.

R,No CAqGC-oF CRA 1902X

Figure 1. Map of the proposed canal route through Lake Nicaragua in 1902.

through the low-lying mountains of and thus a tempting target for pi- kilometer road was constructed to the Isthmus of Rivas (20 km wide at rates. his new port of San Juan del Sur on its narrowest section) to the Pacific After the end of the colonial era, the Pacific coast. Greytown (San Ocean (Figure 1). The project, how- the possibility of an interoceanic Juan del Norte), located at the mouth ever, never materialized. In 1903 connection and the emergence of of the San Juan River, was to remain Panama, with help from the United the United States as a commercial the most important port in Nicara- States, achieved independence from power generated renewed interest in gua until the turn of the century Columbia. The United States then Nicaragua. With the discovery of (Incer 1976). took control of the construction of gold in California in 1848, a rapid With the enhanced importance of the Panama Canal and was no longer route to the gold fields was required, the canal route came increased po- interested in a possible second ca- and Commodore Cornelius Vander- litical interest by the great powers nal. bilt, the US shipping tycoon, real- of the day-Great Britain and the During the Spanish colonial rule ized immediately the importance of United States. William Walker, a (1520-1821), Lake Nicaragua and a Nicaraguan route. He organized filibuster invited by the Nicaraguan the Rio San Juan served as the pri- the Accessory Transit Company Liberals, arrived in Nicaragua in mary highway through which gold, (ATC) and paid the Nicaraguan gov- 1855 and shortly thereafter declared cacao, indigo, and other products of ernment $10,000 for the right to himself president of Nicaragua. Central America reached the Span- cross the country by river and lake. Walker's goal, with the support of ish galleons, which were constantly The creation of this new route would men and material from the slave- being pursued by British and other cut 800 km and several days off the owning US South, was to annex European buccaneers. Several times trip of the anxious prospectors. Nicaragua to the United States. His these pirates, including Sir Francis The first man-made alteration to presidency was initially recognized Drake, sailed up the Rio San Juan to Lake Nicaragua's ecosystem oc- by the US ambassador in Nicara- attack Granada (located on the fur- curred at this time as Vanderbilt gua. This initial recognition was sub- thest northwestern shore of the lake), arranged for portions of the Rio San sequently withdrawn from Wash- where our primary study sites are Juan to be dredged and for large ington, DC, due to pressure from now located (Figure 1). During co- boulders, sand bars, and other ob- Great Britain and the Central Ameri- lonial times Granada was a world- stacles to be blasted away. Docks can governments that recognized the renowned and exceedingly rich port, were built on both coasts and a 20- Nicaraguan Conservative govern-

June 1995 407 of the Sandinista revolution in 1979. Both Japanese and Soviet interest in a canal route in the 1980s stimu- lated research on the lake ecosystem, the results of which remain unpublished in the scientific litera- ture2 (MEPURSS1983). A plan for a canal, however, was eventually pre- sented by the Japanese with an estimated cost of $25 billion (Estrada et al. 1994). The US government began to view with alarm these initia- tives for developing another canal outside of US control and continued to arm and aid the contra movement in its efforts to overthrow the Sandinista government. Many proposals are still being considered, and even today the possibility of a canal through Lake Nica- Figure 2. Common cichlids of Lake Nicaragua. The two large individuals on the ragua and the Rio San Juan is a right are African Oreochromis spp. All others are native to Lake Nicaragua. continuing dream of many Nicara- guans (Estrada et al. 1994). Any ment. Nevertheless, it was to be the the army of Honduras when he tried such project, be it a sea-level canal beginning of a long period of inter- to reconquer Central America. that turns Lake Nicaragua into a vention of the United States in Nica- At the end of the nineteenth cen- marine ecosystem or one that uses raguan affairs. tury, competition over the location atomic explosives to dig a canal that The following year, however, of an interoceanic canal became in- requires locks (Estrada et al. 1994), Walker seized the boats and other tense. Heavy lobbying of the bank- is likely to have an immense and property of ATC in the name of the rupt French Canal company headed most likely detrimental impact on Nicaraguan government. His action by Ferdinand-Marie de Less resulted the ecosystem of this region. caused a drop in ATC stock and in the construction of the Panama infuriated Vanderbilt. This conflict Canal, and the Lake Nicaragua eco- Introductionof tilapia had a profound effect upon the fu- system was left untouched. ture history of Lake Nicaragua be- Nevertheless, the idea of a canal Even without the construction of a cause thereafter Vanderbilt kept his in Nicaragua never died. Modern sea-level canal, the Lake Nicaragua ships idle and supported the Pacific ships grew larger, and traffic through ecosystem is undergoing major Mail Line, which was doing busi- the Panama Canal increased and changes. An attempt to increase the ness in Panama. Supplies and new need for a second canal became ap- fishery and to develop an export recruits to man Walker's army in parent after World War II. In the market during 1983 and 1984 re- Nicaragua dried up, and the major 1970s plans were drawn up to dredge sulted in an extensive stocking pro- route between the coasts shifted back the Rio San Juan and create major gram of non-native tilapia in Lake to Panama. Walker, the only US lake ports at Granada in Lake Nica- Nicaragua and cage culture of tila- citizen to ever be president of an- ragua and the capital Managua in pia in a region known as the isletas, other country, eventually fell from Lake Managua. Such plans, how- near Granada, Nicaragua (Figure 1). power and was executed in 1860 by ever were shelved with the coming Between 1987 and 1988, fishermen in the Granada region began report- catches of in their nets. Table 1. Possible characteristicsof potential invaders.Adapted from Ehrlich1989. ing tilapia They correlated the catching of tila- Successful invaders Unsuccessful invaders pia with a decline in the catch of native cichlids (Figure 2). Local Large native range Small native range people initially avoided fishing for Abundant in Rare in original range original range the introduced tilapia because their High genetic variability Low genetic variability Associated with humans Not associated with humans muddy taste was disliked. As tilapia Female able to colonize alone Female alone unable to colonize populations increase, their poten- Gregarious Solitary tial impact on the unique Lake Nica- Vagile Sedentary raguan ecosystem is becoming a Broad diet Restricted diet source of concern. Short generation time Long generation time Shift between r and K strategies Unable to shift strategy A preliminary survey in 1990 re- Larger than most relatives Smaller than most relatives Tolerates wide range of conditions Narrow range only 2The Nicaraguan Center for Fish Investiga- tion, unpublished reports.

408 BioScience Vol. 45 No. 6 vealed that three species of tilapia- Oreochromis aureus, Oreochromis mossambicus, and Oreochromis niloticus-were being caught throughout the shallow coastal regions, including the southern islands of Solentiname and Lake Nicara- 2.5 gua's outlet on the San Juan River, near San Carlos (Figure 1). Collec- 2 tions in the northern region were taken at the isletas near Granada, the region of the first presumed in- 1.5 and at a site near Pt. troduction, KG Mayales (Point Mollales in Figure 1). The more isolated region of Ometepe Island has subsequently been invaded by tilapia. As shown i~ I f~TBa~~~ 1983 in Figure 3, at Ometepe Island na- 0METE5 ~ OMETEPE tive cichlids averaged 4.34 kg per 100 m of experimental net, a value 0 I NORTHERN comparable with the 4.66 kg (stan- AFRICAN CIT NIC LON ROS OTHER dardized per 100 m) that a 1983 Soviet study (MEPURSS1983) found Figure 3. Average wet weight of cichlids captured by gill nets. Three sites were throughout the lake. Along the sampled 75, 9, and 12 times respectively for two 5-hour periods (0700-1200, northern shore (isletas and Pt. 1300-1800) and one 12-hour period (1800-0600). The numbers of individuals Mayales combined), however, na- and their standard lengths and combined weights were recorded for each species. tive cichlids averaged only 0.80 kg NORTHERN = Northern Lake Nicaragua, 1991-1992; OMETEPE = Ometepe central Lake = per 100 m. Of the total biomass of Island, Nicaragua, 1991-1992; 1983 data from MEPURSS(1983, p. cichlids the north- 79); AFRICAN= Oreochromis sp.; CIT = Cichlasoma citrinellum; NIC = Cichlasoma captured along LON = Cichlasoma = ern 54% consisted of nicaraguense; longimanus; ROS Cichlasoma rostratum; and shore, tilapia, OTHER = all other native cichlids. whereas the tilapia made up only 1.5% of the catch at Ometepe. No tilapia had been collected in Lake high degree of morphological plas- growth rates, broad diets, and the Nicaragua during the Soviet study ticity and genetic variability is dem- ability to withstand crowding (MEPURSS1983). onstrated by the presence of several (Hanley 1991). Most tilapine fishes Furthermore, in our study the species that are endemic to particu- are gregarious schooling species and total catch of fish at Ometepe was lar areas (Fryer and Iles 1972, are likely to migrate long distances 1.8 times greater per set than in Trewavas 1983); furthermore, many (Fryer and Iles 1972, Stauffer 1984, areas with the higher concentration of the species (e.g.,O. mossambicus) Trewavas 1983). Introduced popu- of tilapia. Cichlasoma citrinellum, have adapted to a multitude of envi- lations of tilapia, although prima- Cichlasoma nicaraguense, and ronments and, in fact, occupy both rily herbivores, feed on insects, zoo- Cichlasoma longimanus were caught freshwater and estuarine areas in plankton, phytoplankton, vascular significantly more frequently at their native ranges (Trewavas 1983). plants, and larval/juvenile fishes Ometepe Island than on the north- Tilapine fishes are hardy and can (Hensley and Courtenay 1980). ern shore (Mann Whitney U: P<0.01; thrive in a wide range of water quali- Species in the genus Oreochromis Figure 3). Catches of the primarily ties (Philippart and Ruwet 1982, are maternal mouthbrooders, thus a sand-dwelling C. nicaraguense, C. Stauffer et al. 1984, Welcomme single female is able to colonize a longimanus, and Cichlasoma ros- 1984). They have been domesticated new environment by carrying her tratum and C. citrinellum/labiatum by humans and are the primary spe- young in her mouth (Fryer and Iles were inversely associated with catches cies used in aquaculture throughout 1972). Furthermore, because they of the tilapia species (Figure 4). the tropics (Pullin 1991), and they are mouthbrooders, they do not have These data confirm the reports of are becoming increasingly impor- strict habitat requirements for re- Nicaraguan fishermen that native tant in temperate aquaculture fa- production. Under laboratory con- cichlid yields declined with the ar- cilities. For example, 0. niloticus ditions, we have observed them to rival of tilapia. These African exot- has been identified as an important spawn in gravel depressions and on ics possess the attributes listed by species in global aquaculture (FAO clay pots, glass bottoms, and rock Ehrlich (1989) as potentially con- 1980). slabs. Introduced populations can tributing to the rapid expansion and Many of the attributes that make literally occupy all available habitat success of invading species (Table 1). these fish suitable organisms for in- with their spawning sites (Figure 5). Many of these tilapine fishes have tensive production facilities also al- Moreover, they are larger than all of large native ranges and are abun- low them to colonize and thrive in the native cichlids (Figure 2) and are dant in their natural habitat. Their new surroundings. They have rapid likely to displace them in territorial

June 1995 409 ecological disaster in Lake Nicara- ) gua, such as those experienced in 3.0 0 C. nicarraguense other tropical and semitropical freshwater ecosystems (Barel et al. 1985, Baskin 1992, and * C. Courtenay 2.5 longiImanus Stauffer 1984, Zaret and Paine 1973). If these species move down CD 0) A C. rostiratum the Rio San Juan and invade saltwa- 2.0 -c ter habitats along the Atlantic coast, C,) -0 the productive marine fisheries and 0 valuable estuarine nursery grounds (Ryan 1992) could also be affected. () The presence of tilapia could di- - 4OA rectly affect not only Lake Nicara- z 1.0 gua's fish community but also the general aquatic environment (Wel- }o o comme 1984). In Lake Victoria, for 0.5 1? 0 example, where the Nile perch, Lates sp., has devastated the native cichlid fauna, the entire ecosystem z I =rkI ,^A |A I I has dramatic u I XS R -Z\ax ' ! ) DI ' I I i ^_ undergone changes 0 1 2 3 4 6 6 7 8 9 10 11 (Barel et al. 1991, Baskin 1992). cascade African cichlids Trophic theory (Carpenter kg/set et al. 1985) predicts that the alter- Figure 4. Weights of catches of each of the four native cichlids in relation to ation of Lake Nicaragua's ecosys- tilapia catches. tem is likely to have effects on the and ? , :y%.,.. X ..; ? ...... planktonic community primary productivity of the lake. Besides the destruction of the native fish populations and loss of genetic diversity, the environmental degradation of Lake Nicaragua may have conse- quences not yet anticipated. We still have cause for hope that the tragedy of Lake Victoria (Kauf- man 1992) will not be repeated in the great lakes of Latin America. Twenty years elapsed from the time the Nile perch was introduced into Lake Victoria until it began elimi- - ...... : ; nating the native cichlid population. ). ;' Swift and aggressive management has :.:: of tilapia in Latin America could ?0 hmitigateFew'e fi. the negative impacts of their i:: I-.~:.. .introduction. ?'.,,...:x.:.;otA;~, : .. Immediate actions hypothesized ?.:,",' . to protect the native fauna include: x...... ""itheestablishment of a fishery that Figure 5. Aerial view of spawning sites of Oreochron nis aureus in a lake in focuses upon capturing tilapia in southern Florida. The spawning sites are depressions i n the sand. the coastal regions; the development of management plans to protect the conflicts or severely interfere in the able habitat and food resources large predatory marine species that defense of their young (McKaye would be avaiilable to tilapia on the inhabit Lake Nicaragua, because 1977, 1984, McKaye and McKaye coral reefs fc)und off the Nicara- these fishes can easily prey upon 1977). Finally, they have a short guan coastlin e. In support of this adult tilapia that venture into open generation time, reaching reproduc- contention, vye note that Oreo- portions of the lake; and the moni- tive maturity in six months and hav- chromis zilli h as established a popu- toring of the Rio San Juan and the ing multiple broods each year lation in the Salton Sea (Hensley establishment of a tilapia fishery to (Stauffer 1984); or conversely they and Courtena y 1980) and that O. prevent or slow the movement of the can delay reproduction and breed at mossambicus has invaded a Pacific tilapia toward the Atlantic coast. larger sizes (Trewavas 1983). atoll (Lobel 1 980). Few fish species have been success- We, therefore, predict that suit- There is a \great potential for an fully eradicated once they have be-

410 BioScience Vol. 45 No. 6 come established (Courtenay and Hopkins University Press, Baltimore, MD. Managua, Nicaragua. Stauffer Stauffer et al. Ehrlich, P. 1989. Attributes of invaders and Miller, R. R. 1966. Geographical distribu- 1984, 1988). the tion it is that markets and invading processes. Pages 315-327 in of Central American freshwater Therefore, key J. A. Drake et al., eds. Ecology of Bio- fishes. Copeia 1966: 773-802. other economic incentives be pro- logical Invasions: A Global Perspective. Norton, B. G., ed. 1986. The Preservation of vided to convince local fishermen to Wiley, New York. Species: The Value of Biological Diver- prey upon these exotics and thus Estrada, E., H. Mairena, E. Martinez, and D. sity. Princeton University Press, Prince- their at a level Garcia. 1994. Un Canal para Nicaragua? ton, NJ. keep populations Mundo Financiero 16-17. and Ruwet. 1982. that allows coexistence with the 1(5): Philippart, J-Cl., J-Cl. Food and Agriculture Organization of the Ecology and distribution of tilapia. Pages native species. United Nations (FAO). 1980. Report of 15-59 in R. S. V. Pullin and R. H. Lowe- The value and importance of a the Ad Hoc Consultation on Aquaculture McConnell, eds. The Biology and Cul- unique ecosystem as diverse as that Research. FAO Fisheries Report 238, FIR ture of Tilapia Vol. 7. International of Lake is well R238. FAO, Rome, Italy. Center for Living Aquatic Resources Man- Nicaragua recog- Fryer, G., and T. D. Iles. 1972. The Cichlid agement, Manila, the Philippines. nized (Norton 1986, Wilson 1988). Fishes of the Great Lakes of Africa: Their Pullin, R. S. V. 1991. Cichlids in aquacul- The lesson of Lake Victoria (Baskin Biology and Evolution. Oliver and Boyd, ture. Pages 280-309 in M. H. A. 1992, Kaufman 1992) is simple: Act Edinburgh, UK. Keenleyside. Cichlid Fishes: Behaviour, now before it is too late. Hanley, F. 1991. Effects of feeding supple- Ecology and Evolution. Chapman and mentary diets containing varying levels Hall, London, UK. of lipid on growth, food conversion and Ryan, J. 1992. Medio ambientes marinos Acknowledgments body composition of Nile tilapia, 0. de las Costa Caribe de Nicaragua. niloticus (L). Aquaculture 93: 323-334. WANI, Revista de Caribe nicaragiiense This work was supported by the Hensley, D. A., and W. R. Courtenay Jr. 12: 34-47. National Science Foundation, the 1980. Tilapia mossambica (Peters). Page Ryan, J., L. Gonzales, and E. Parrales. 1993. US for International Devel- 774 in D. S. Lee, C. R. Gilbert, C. H. Diagnostico y Plan de Accion de los Agency Hocutt, R. E. Jenkins, D. E. McAllister, Recursos Acuaticos en Nicaragua. Plan opment, and the US Information and J. R. Stauffer Jr., eds. Atlas of North de Acci6n del Ambiente Nicaragiiense, Service Fulbright Program. We thank American Freshwater Fishes. North Caro- Ministerio del Ambiente y Recursos the Nicaraguan Ministry of Natural lina State Museum of Natural History, Naturales, Managua, Nicaragua. the Center Raleigh, NC. Stauffer, J. R. Jr. 1984. Colonization theory Resources, Nicaraguan 1976. of Lake Nicara- relative to introduced for Fish and the Ecol- Incer, J. Geography populations. Pages Investigation, gua. Pages 3-7 in T. B. Thorson, ed. 8-21 in W. R. Courtenay Jr. and J. R. ogy Department of the University of Investigations of the Ichthyofauna of Stauffer Jr. eds. Distribution, Biology, Central America for their assistance. Nicaraguan Lakes. University of Ne- and Management of Exotic Fishes. The Walter R. Courtenay provided the braska, Lincoln, NB. Johns Hopkins University Press, Balti- of 0. aureus Kaufman, L. 1992. Catastrophic change in more, MD. photograph spawning freshwater R. D. K. and C. H. sites in south Florida. We thank species-rich ecosystems. Stauffer, J. Jr., Vann, J. BioScience 42: 846-858. Hocutt. 1984. Effects of salinity on pre- Ebersole, L. Kaufman, S. Kraak, and Lobel, P. W. 1980. Invasion by the ferred and lethal temperatures of the A. Lopez de Perez for their com- Mozambique tilapia (Sarotherodon blackchin tilapia, Sarotherodon mela- of a Pa- notheron. ments on the manuscript. mossambicus; Pisces; Cichlidae) Water Resour. Bull. 20: cific Atoll Marine Ecosystem.Micronesica 771-775. 16: 349-355. Stauffer, J. R. Jr., S. E. Boltz, and J. M. Boltz. Referencescited McKaye, K. R. 1977. Competition for breed- 1988. Thermal tolerance of the blue tila- ing sites between the cichlid fishes of pia, Oreochromis aureus, in the Susque- Barel, C. D. N., et al. 1985. Destruction of Lake Jiloa, Nicaragua. Ecology 58: hanna River. N. Am. J. Fish. Manage. 8: fisheries in Africa's lakes. Nature 315: 291-302. 329-332. 6014. .1984. Behavioural aspects of cichlid Thorson, T. B., ed. 1976. Investigations of Barel, C. D. N., W. Ligtvoet, T. Goldschmidt, reproductive strategies: Patterns of terri- the Ichthyofauna of Nicaragua Lakes. F. Witte, and P. C. Goudswaard. 1991. toriality and brood defense in Central University of Nebraska, Lincoln, NB. The haplochromine cichlids in Lake Vic- American substratum spawners versus Trewavas, E. 1983. Tilapiine Fishes of the toria: an assessment of biological and African mouth brooders. Pages 245-273 Genera Sarotherodon, Oreochromis and fisheries interest. Pages 258-279 in M. in R. J. Wooton and C. W. Potts, eds. Fish Danakilia. British Museum of Natural H. A. Keenleyside, ed. Cichlid Fishes: Reproduction: Strategies and Tactics. History, London, UK. Behaviour, Ecology and Evolution. Academic Press, London, UK. Welcomme, R. L. 1984. International trans- Chapman and Hall, London, UK. McKaye, K. R., and N. M. McKaye. 1977. fers of inland fish species. Pages 22-44 in Baskin, Y. 1992. Africa's troubled waters. Communal care and kidnapping of young W. R. Courtenay Jr. and J. R. Stauffer Jr., BioScience 42: 476-481. by parental cichlids. Evolution 31: eds. Distribution, Biology and Manage- Carpenter, S. R., J. F. Kitchell, and J. R. 674-81. ment of Exotic Fishes. The Johns Hop- Hodgson. 1985. Cascading trophic inter- Ministerio de la Economica Pesquera de la kins University Press, Baltimore, MD. actions and lake productivity. BioScience Union des Republicas Socialistas Sovie- Wilson, E. O., ed. 1988. Biodiversity. Na- 35: 634-639. ticas (MEPURSS). 1983. Investigaciones tional Academy Press, Washington, DC. Courtenay, W. R., and J. R. Stauffer Jr., eds. economicas de pesca de los depositos de Zaret, T. M., and R. T. Paine. 1973. Species 1984. Distribution, Biology, and Man- aqua interiores de la Republica de Nica- introduction in a tropical lake. Science agement of Exotic Fishes. The Johns ragua (el lago de Nicaragua). MEPURSS, 182: 449-55.

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