Rev. Biol. Trop., 48(2/3): 473-485, 2000 www.ucr.ac.cr Www.ots.ac.cr www.ots.duke.edu

A management plan for the sport fishery of dovii (Pisces: Cichlidae) in Hule lake, Costa Rica

2 Farid A. Tabash B. ¡ and Emilier Guadamuz S. Est¡¡ción de Biología Marina, Universidad Nacional. P. O.B. 126-5400, Puntarenas, Costa Rica. Fax (506) 661-3635 ([email protected]) 2 Centro Naútico Pesquero, Instituto Nacional de Aprendizaje, Puntarenas, Costa Rica.

Received 28-IV"1999. Corrected 18-1-2000. Accepted 4-Il-2oo0.

Abstraet: A first attempt to regulate tbe fishing activity while preserving the and its habitats is presented for Hule lake. We intensively sampled the "gu¡¡pote" between March 1996 and April 1997 using monofilament gill nets and a floating line, collecting 421 individuals. P. dovii biomass was relatively low; this species had a long life cycle (8-10 years) and tbe growth oscillation was low (C=O.3). Maximum life expectation was estimated at 12 years and the point of mínimum growtb coincided with the spawning that takes place between November and December. After (54.6 mm). sp¡¡wning, P. dQviítake around seven montbs to reach recruitment size The length for sexual rnaturity was 134 mm Lt, whichjndicates that this s¡ieciesis viable for reproduction soon afterleaving the protection zones around the lagoon. "Guapote" sport fishing in the Hule lake is in equilibrium, the renewal rate is 80%. An increment in the actual fishery effort is not recommended, siilce it could seriously affect tbe natural renewal capacity of the stock.

Key words: Cichlasoma, Parachromis, Costa Rica, stos.:k assessment, management plan, conservation, sport fishing, Hule lake.

The Cichlidae family consists of numerous Rica's mountain ranges (Miller 1966, Alpírez genera and species distributed in Africa, where 1985). Its cornmon name is "guapote" and it their adaptive radiation in the great lakes has is the largest species of the family, reaching a been investigated in detail (McKaye 1977). In total length of 650 mm (Anonymous 1996). the America's neotropical zone its distribution In lake Arenal, the species prefers moder­ extends from Texas, United States, to Chileand ate currents and rocky areas with bathymetric Argentina (Darlington 1957, McKaye 1977, De zonation accordance to the age (Bussing and Silva et al. 1984 and Bussing 1989). López 1977 .aJld Moya 1979). The majority' of the of Latin In general, P. dovii can be found in environ­ America belong to the. Parachromis ments rangingfrom shallow waters to rapidcur­ (Bussing 1998); are extremely heterogeneous in rents where it hides behind rocks or over­ their feeding pattems (Yañez-Arancibia 1978, growths. It occurs in streams waters and lakes 1984), McGinthy habitat selection (McKaye between heights of O to 600 m., and tolerates 1977b, Rosales 1980), morphology (Meyer temperatures from 21 to 31°C. It is highly pis­ ' 1987) and population dynamics (Fields 1986, civorous, eating tetras, poeciliids and cichlids, Gaspra-DiIlanes et al. 1995 and Morales­ but it also ingest crustaceans and insects Bojórquez 1995). (Bussihg 1987, 1998). P. dovii is distributed in Central America Most of the investigations on P. dovii refers from middle to the great lakes and to , biology and ethology. Aldave lagoons of Nicaragua and the slopes of Costa (1985) presented some research on "guapote" 474 REVISTA DE BIOLOGÍA TROPICAL biology in lalceArenal, including a brief study of the sampling zone until 4 p.m when it was theirpopulation dynamics. Campos (1986» esti­ moved to the following sampling zone, to that the "guapotes" occupy all of lalce mated repeat the procedure. Arenal, preferringbays withvegetable cover and Parallel to this,a floatingline containing25 zones with an abundance of fallen trunks. fishhooks #7, 25 fishhooks # 8, 25 fishhooks # McKaye (1977) reported the reproduction pat­ 9 and25 fishhooks# 10 placed in altemate form tem of in thelalce Jilaloa, Nicaragua.. P. dovii it was located in the west sector of thelagoon, a In this assessment plan we present a first zone of shallow waters with a, dense plant cover attempt to regulate the fishingactivity while, at and many macroalgae trunks. The floating and the same time, preserving the species and its line remained in this area during three days. habitat. Every 8 the line was checked and the bait hours, (sardine and "guapote") was changed. Each"captured "guapote" was placed in an MATERIALS METHODS ANO ice box and, at the operation center, total length total weight (g), sex, maturation (inm), Between March 1996 and Aprll 1997, state, and stomach content were estimated. specimens of were collected in three "guapotes" captured were identified P. dovii All sampling zones (Fig.l) in the Hule Ialce using using the keys of Astorqui (197i) and 0.6 monofilament gill nets with a mesh size of Bussing (1977). 6.985 and.7.62 cm. with a height of 3.8 m. "Guapotes" were pooled according with the Feeding patterns: In all the 1. mesh size that they were captured. "guapotes" analyzed, the gut was removed by Each month the sampling perlod were 3 dissection. Data on sex and maturlty were col­ days, the nets were placed in each one of the lected. The gut content was removed directly sampling zones during the night. Between 7 the stomach and placed in a vial contain­ from a.m and 8 a.m, they were lifted to collect the ing ten-percent formalin as a fixative. Before catch of "guapotes". Then the net was left in samples were examined in detail, excess formaldehyde was removed by soaking the samples in several changes of water. Then, the samples were preserved a 45-70% aqueous in solution of alcohol. For quantitative descrlp­ tion of the diet, the method of frequency of occuiTence was used.

2. Sex ratio, maturation patterns and size at tirst maturity: mean size at first The maturlty was determined at 95% confi­ (ML) dence limits using the method of Udupa (1986), based on accumulative percentage fre­ quency curve of maturation stages. The matu­ ration stages of each guapote analyzed was

Fíg. 1. Study areas. "The collection stations are shown in determined using the method of Holden and relation to the dock location. Raitt (1975). INTERNATIONAL JOURNAL OF TROPICAL BIOLOGYAND CONSERVATION 475

Stock assessI11ent:. Length frequency occurrence. The rest of fishes represented 37% ·3. analysiswas applied to estimate growth parame­ of the diet, while the insects presented 26.8% ters, using the von Bertalanffy growth curve (Table 1). The category, rest of fishes, was incorporated in FiSAT software (Gayanillo et al. composed mainly of tetras aeneus), (Astyanax 1996). It was assumed that the length frequency "olominas" (Poecilia gillii) and juveniles data arerepresentative of the population, that the of P. dovii. growth pattems are repeated from year to year, TABLE 1 that the von Bertalanffy formula describes the mean growth in the population and that all fish Presence of several categories offood in stomaches ofP. in thesamples have the same growth parameters. dovii, frecuency of occrrence in the Hule lalce, during the period March to Apri11997. The seasonal oscillation (C) and the point of 1996 minimum growth wete also calculated. Feeding category Proportion Frecuency (WP) Parameters of the length-weight relation­ of occurrence ship were estimated using least squares regres­ Rest of fishes 0.09 175 sion on log-transformed data with bias correc­ Insects 0.28 124 tion. total of 421 fishes ranging from 100- Microcrustaceans 0.23 39 A Vegetable tissue 0.05 27 630 mm were used for the analysis. Sediment 0.03 19 Total mortality (Z) wa& estimated fromdata Digested material 0.32 79 corrected for gearselectivity using themethod of Moureau (1988), taking into account the com­ plete length frequencydistribution obtained with P. dovii size affected the composition of the gill-net plus the "guapotes" caught with the stomach contents. The juveniles consumed floating lineo Natural mortality (M) was estimat­ more poecilids and microcrustaceans than the ed fromthe empírical equation ofPauly (1980a). adults, the latter supplemented their diet with Fishing mortality (F) was estimated by subtrac­ insects (Table 2). tion of and M. The optimum exploitation Z rate( E = FfZ), was computed for a preliminary TABLE 2 assessment of whether the stock is lightly (E< 0.5) or heavily exploited (E>0.5). Presence of several feeding categories inP. dovii, according with the size classes sampled in the Hule Identification of selection pattems were lagoon. estimated by backward projection of the straight portion of the catch curve. Feeding category < 100 100-400 400-630

Recruitment pattems were obtained projecting Rest of fishes 8.6 19 12.2 the length frequency data available backward Insects 65.5 47.6 19.5 into the time axis. Estimations of yield and Microcrustaceans 41.4 33.3 18.3 Vegetable tissue 8.6 14.3 4.9 biomass per recruit were plotted. Sediment 1.7 4.7 4.6 Using the results of the assessment and Digested material 43.1 47.6 32.4 statistics on the number of visits by occasional and sport fishermen, recommendations were made. for the management of the "guapote" in temporal and spatial variations that The P. the Hule lagoon. dovii presented in the composition their diet of (Table 3), demostrate that even when the sam­ pling zones are relatively close, the availabili­ RESULTS ty of food was different;. this could influence the distribution of the population of "guapote" 1. Feeding patterns: Of the six feeding along the sampling stations in the lake. categories that were determined, rest of fishes Similar results were reported by Aldave and insects presented the major frequency of (1985) in lake Arenal. 476 REVISTA DE BIOLOGÍA TROPICAL

Proportions of food categorles in the diet Sex ratio, maturation patterns and ·2. tended to change with length class, but there size at first maturity: 421 individuals Froín didn't seems to be a definitivepattem. The num­ collected durlngthe sampling perlod 47% ber of "guapotes" with empty stomach were males and 53% females. The sex ratio increased with thematuration stage; maybe the in the population sampled was 1: 1 (Fig.2). occurrence of prey capture will decreases when There were significantly (Mann-Whitney U­ the "guapote" approach their maturation peak. test, p< 0.1) more inmature males and females in the sample perlod in the rainy sea­ TABLE 3 son than in the transition and dry season (Table 4). With respect to maturlty, Proportions of frequency of occurrence of several food P. dovii categories in P. doviifor the sampling stations ubicated presents successive maturation pattems with in the Hule lagoon. seasonaI spawning peaks. Sexually mature guapotes made up the largest proportion dur­ Food category Station 1 Station 2 Station 3 ing November and February. McKaye (1977) Rest of fishes 10.6 9.4 8.5 reported a maturation peak of "guapotes" in Insects 18.8 23.7 18.8 Jilaloa lake, Nicaragua during February and Microcrustaceans 22.1 21.2 16.0 April; Campos (1986) in lakeArenal, indicat­ Vegetable tissue 8.2 4.4 O 6.5 2.5 0.9 ed that probably during Sediment P. dovii Digested material 31.1 41.8 25.5 August or September.

TABLE 4

Percentage of each gonadic maturation phase in P. dovii population. during (he sampling period in the Hule lagoon.

MontblYear Phase 1 Phase II Phaseill Phase IV

March/96 5.8 O 8.8 6.4 April 17.4 O 11.3 7.6 May O 1.2 Iune 14.2 O O O Iuly 17.9 O 6.2 O August 5.8 O 5.0 O September 9.5 O 11.9 O October 6.3 O 5.0 4.6 November 2.6 O 25.1 5.5 December O 17.6 4.6 Ianuary/97 O O 6.9 25.2 February 4.2 O 1.9 19.8 March 1.6 O 5.0 12.4 April 14.7 O O 15.6

However, 42% of the population was Length.at firstmaturity oscillated for the immature (phase 36% was mature (phase males between 144 and 154 mm Lt. and for n, III) and 22% had spawned (phase IV). Phase is a the females between 134 and 142 mm Lt, II stage slightlyprevious to the stage of fullmatu­ which corresponds with an age of 8.3 months rlty, probably thisstage overlaps with phase and 7.6 months respectively. The maximum m. The increments in the frequency of life expectation was estimated between 10 spawned guapotes during December and and 12 years, based on the growth rate calcu­ February, indicate that the more important lated from the modal progression analysis. spawning peak coincides with the transition perlod between rainy and dry season. INTERNATIONAL JOURNAL OF TROPICAL BIOLOGY AND CONSERVATlON 477

35 60

30 50

# 25 40 n d I # m 20 a i t n 30 u d r I i 8 15 t e x y 8. 20 t 10 a g e

10 5

o o 3 4 5 6 7 8 9 1011 12 1 234 I 96 I 97 Month/Year

Males - Females _ Inmature

IiItijjtl Spawned CJ Mature

Fig. 2. Variations in the relation male: female and in the maturation stages obtained during the sample perlod in P. doviiin the Hule lalce, Costa Rica.

3. Stock assessment: 'According to the weak growth seasonality (C). The perlod of growth parameter estimates with the von mínimum growth was between November (WP) Bertalanffy growth equation, obtáined through and December, the same perlod of maximum the FiSAT program, in the Hule lake P. dovii maturation stage. Thegrowth equation obtáined present a long life span, slow growth rate and in was: P. dovii 00:I:J Lt = Fig.3, the length frequency distribution 621 In shows that "guapote" populationis composed l_e-O.64 (1 +0.88)-0.3 • 0.64/2n (t-0.42)-SIN2 n (0.88-0.42» the [ J of approximately two cohortsand that thematu­ rationpattems are continuous, suggesting that the where Loo = 621 mm K = 0.64 year-1 = = populationwas composedof definiteage groups. e 0.3 WP 0:92 year1

. 56 1 1 52 � (/) 48 � _.- o .44 tri __ _ --- 1- �.--f t:lJ _ 40 [.-J. -- L -;--{: --- -'-­ � '? l <:) -!. [ ;;' � � ­ E,::-;;o�J�· - - [ �-",·1· � 20 [=[---1L __ �_� 16 L_! 1- ! 1 .. .-' - ! 12

M-SS A J J A s o N o J-97 f M

Fig. 3. Length frequency distribution and growth curves obtained for P. dovii popuJation in the Hule Jalce, Costa Rica. INTERNATIONAL JOURNAL OF TROPICAL BIOLOGY AND CONSERVATION 479

Biometry: Hartnoll (1974) showed that ation of the "a" and "b" parameters. This the growth rate of any organ usually changes means that in order to control the annual estab­ during ontogeny and that the growth constant lishment of closed seasons, it is possible to use is characteristic within each growth phase. For the biometric relationship. Staff can be easily the "guapote" population, the relation was trained to collect this type of information. established with 421 data pairs. The mínimum Mortality and exploitation levels: It is length was 120 mm Lt. and the maximum was clear that "guapote" biomass initially depends 560 mm Lt, while the weight oscillated on the level of fishing effort, which increases between 41 g. and 2053,6 The length-weight considerably during the season (January to g. dry relationship was: April). During the rainy season (May to October), the survival of the juveniles is rela­ W = 0.0000241 Lt2.95 (r = 0.98, s.d = 0.19) tively stable in the reproduction zones, consid­ ering that maximum spawning occurred during Aldave (1985) and Campos (1986) report the transition of rainy to dry season (November similar results in their analyses of the guapotes to January) the spawning was presented. of lake Arenal. In the females the equation Therefore, for a resource management profes­ was: sional to predict with confidence the maximum exploitation levels, it is necessary to predict = 0000354 Lt2.96 (r = 0.93, s.d = effectively the annual levels of abundance, on W O. 0.29) which recruitment pattems are dependent. Total mortality (Z= 3.14 year-I) is quite The minimum length was 110 mm Lt. and influenced by fishing than natural mortality the maximum 532 Lt., while weight varied (FIM = 0.91 year -I)which coincides with the from 39 g. to 1741.8 g. In males the lengths exploitation rate obtained CE= 0048). It is evi­ varied between 110 mm and 564 mm Lt., cor­ dent that the population is close to the responding to weight between 37 g. and Maximum Sustainable Yield, in the equilibri­ 2063,6 g. respectively. The length-weight rela­ um point, this means that recruitment barely tionship for males was: replaces the "guapotes" fished. The length first capture (Lc =149.6 of SO% = 0.0000541 Lt2.79 (r = 0.95, s.d = 0.19) was quite close to the female length at first W mm) maturation (138 the males, is the mm) and in Taking into account that the values "a" same length. This is a reflectionof the exploita­ and "b" obtained with the exponential equation tion level that the guapotes are being subjected. have a biological interpretation, where "a" is The probability that they are fished before the condition factor and "b" is a relative reproducing one time in theirlife is almost 50%. growth coefficient representing the isometry Population/Recruitment relationship: that each guapote has in its growth, then "a" Taking into account that the population of and "b" show an inverse relationship (FigA). guapote in the Hule lake was exactly in the The condition factor ¡ncreases from equilibrium point and that the death probabili­ November to February, while the isometry fac­ ty by different causes than natural mortality is tor decreases, during the months of maximum high, the recruitment levels are relatively low. maturatíon stage. During those months the During the year, between August and guapotes using more energy for the generation September, 45% of the recruits enter the popu­ of sexual products, and therefore decrease their lation that is subject to fishing. This leads to relative growth. the estimate that after spawning, larval devel­ In terms of resource management, it is opment in the protected areas of the lake takes possible to detect the maturation and spawning approximatelyseven months until the juvenile periods and relate them with the monthly vari- stage is reached (Fig.5). 480 REVISTA DE BIOLOGÍA TROPICAL

0.001 3

0.0009 _-1 .... , -- "'�.- \ \ 2.5 \ 0.0008· \ \ \ \ 0.0007· \ \ \ 2 \ ].. \ 0.0006 \ \ \ \ á \ 0.0005 \ � \

- iSe ------8 0.0004

0.0003·

0.0002 0.5

0.0001

o - --'---r o ---,------,------.--- �T -'�-_.,.-----'...... __.____,.----__,_---_,..-'--___.____".-.-....,__r�-- - o M-OO A M J A s O N o E-97 F M A month

Fig. 4. Condition factor (-) and isometry value e _ .)relationship obtained in P. dovii in the Hule lake, Costa Rica. INTERNATIONAL JOURNAL OF TROPIC AL BIOLOGY AND CONSERVATION 481

Recruitment (OJo) 60

50

40

30

20

10

o J J A s o N o E F M A M 1996-1997

Fig. 5. Recruitment pattems for P. dovii population, obtained during the sampling period in the Hule lake, Costa Rica.

Relative Yieid and Biomass per Recruit: explains how recruitment and biomass are This assessment and yield model describes affected by an increase in the fishing mortality changes in the "guapote" stock between 1996 level (F) or fishingeffort (f). and 1997, as a result of the change in the fishing The natural renewal rate under the actual effort applied duringthat periodo The models of conditions already is about 80%, meaning that yield per recruit and biomass per recruít under the actual level effort, 80% of the 482 REVISTA DE BIOLOGÍA TR OPICAL recruits have to replace the "guapotes" fished. according to the fishery effort that at this Therefore, yield per recruitment under the moment is applied without controls over sport actual exploitation rate is too low (Fig.6), (E) fishing licenses.

Fig. 6. Relative yield per recruitment (Y' I R) estimated for P. dovii population in the Hule lake,Costa Rica.

Recommendations for management: 4. The environmental variables that affect the Actions snggested. abundance and distribution pattems of P. Assessment of the P. dovii stock should be dovii n l. in the lagoo and their relationship carried out periodically to detect changes in with the dry and rainy season, should be thedynamics of the stock, including variables examined. like the number of cohorts, the spawning 5. With the cooperation of the Association of process, growth rate and environmental vari­ Communal Development and the staff of ables that can serve as "quantitative marks of the Area de Conservación Cordillera thestate of the "guapote" population. Volcánica Central (ACCVC) of the 2. 1s necessary to start biomass studies, using Ministerio del Ambiente. Energía y a capture-recapture model. This allows to (MINAE), a pilot catch and effort dat.a know the abundance level, relative growth recording system (CEDRS) should be and survival ofthe "guapotes". established. 3. According with the results of the assess­ 6. The minimum length of capture for the men! process, a restocking project be "guapotes" of the Hule lake, should be will 150 implemented. rnmLt. INTERNATIONAL JOURNAL OF TROPICAL BIOLOGY ANO CONSERVATION 483

7. According to the census of weekIy numbers 12. one of these fishing sectors it isrec­ In each of sport fishers in the lake, carried out during ornmended to constrilct two bases of cement two years (1996-1997), the prime fishing with a c1early visible ruler incorporated. The were Saturday andSunday, with anaverage of ruler will be of 20 cm. length, highlighting a dry season. 35 fishennen per day, during the length of 15 cm, with the legend ''length of the rainy season, the average of number of capture allowed, if your fish doesn 't In minimum fishennen for those same days, decreased to reachthis length, remove the hook and retum 10 per day. This informatión, related to the fish the water". the to analysis of relative yield and biomass per 13. It is imperative to construct a control stall, recruit and to the mean number of fish per where the park-guard has the allowing day/fisherman (3 fishes), allows a maximum responsibilities: number of fishennen perday of 15. - restrict the access of sport fishermen to 15 8. The only type of fishhookto be used is the per day. "O'Shaughlessy (1/0 or 2/0); line resistance hand out the control and registration sheet can be left for the fishermen to choose. to each sport fisherman. 9. A closed season ofthree months (November infonn thefishermen about the nshing regu­ 15 to January 15) should be established in lations. 2001. During this c10sed season, assessment - collect the basic biometric information on should be started, mainly on maturation and the catches. spawning pattems. Depending on the results of this study, in 2002 one or two mobile c10sed seasons of 1 month each should be ACKNOWLEDGMENTS establishedto protect the spawning peaksof "guapote" stock. We thank Elizabeth Ramírez, head of pro­ the ject: "Use plan of the Hule ,ahd Cuarto IO.The areas of the Hule lake indicated in Fig. Río 7, should be permanent1y c10sed to the sport lagoons by Sustainable Development" for the grants provided. Universidad Nacional fishery, because between 25% and 35% of At the fingerlings develop in these areas and (UNA) Instituto Nacional de Aprendizaje and possibly are reproduction zones. (INA) for the financial support and other facili­ 11. It is recornmended to allow the fishing of ties. To Anne Van Dam and Roxana Víquez for only the·sectorsindicated (Fig.7). their suggestions and style corrections. guapóte in

RESUMEN

Un primer intento para regular la actividad de la pesca deportiva para el guapote lagunero, Parachromis dovii mediante los resultados de un programa de evalu­ ación del recurso y ,del estudio de la dinámica poblacional de esta especie se presenta. La biomasa del guapote es rel­ ativamente baja. La especie presenta un ciclo de vida largo (8 a 10 años) con una baja oscilación en el crecimiento (C= 0.3), la expectativa de vida máxima estimada fue de 12 años y el punto de mínimo crecimiento coincidió con el período de desove (entreNoviembre y Oiciemb�). Luego del desove, P. dovii permanece en las áreas protegidas cerca de 7 meses haSta alcanzar la talla deteclutarniento (54.6 mm Lt). La longitud de primera maduración fue de Fig. 7. Fishing and permanently closed areas suggested in 134 mm Lt, lo que indica que esta especie es apta para the Hule lake, for the sport fishery of the "guapote . reproducirse poco tiempo después de haber abandonado " lagunero". las"áreas de protección, ubicadas alrededor de la laguna. 484 REVISTA DE BIOLOGÍA TROPICAL

También se describen algunos aspectos de su biología. La ficas de Arenal, Bebedero y Tempisque, Costa Rica. pesca deportiva del guapote en la laguna Hule mantiene Rev. Biol. Trop. 25: 13-37. aún a la población en equilibrio, la tasa de renovación nat­ ural se estima en 80%, por lo que no se recomienda per­ Campos, J.A. 1986. El recurso pesquero del guapote mitir un incremento en los niveles actuales de esfuerzo (Cichlasoma dovii) en el embalse de Arenal, Costa pesquero, dado que esto afectaría seriamente la capacidad Rica. Rev. Biol. Trop. 34: 215-219. de re'l1ovación natural de P. dovii. Darlington, S.L 1957. Comportamiento parental en Cichlasoma facetum (Jenyns) (Pisces: Cichlidae) REFERENCES Rev. Biol. Urug. 6: 31-38.

De Silva, J.T. 1984. Size and shape in ontogeny adn phy­ Aldave, G.T. 1985. Algunos aspectos biológicos del logeny of!he cichlids in !he world. Paleobiology 5: guapote Cichlasoma dovií (Gunther 1864) (Pisces: 296-317. Cichlidae) en el embalse Arenal, Guanacaste, Costa Rica. Reporte de investigación, Escuela de Ciencias Gaspar-DiJlares, M.T., A.S. Iturbide., P.G. Yoval & D.L. Biológicas, Universidad Nacional 29 p. García. 1995. Dinámica poblacional y biomasa desovante de la anchoa (Anchoa mitchilli) en la Alpírez, O. 1985. Ictiofauna de la vertiente del Pacíficode laguna de Tamiahua., Ver., México en 1985 y 1986. Costa Rica. Brenesia 23: 2-10. INP-SEMARNAP., México.Ciencia Pesquera 11: 21-27. Anonymous. 1996. Concepts, design and data source. ICLARM., Manila, Phillipines. 179 p. Gayanillo, F.C., D. Pauly & P. Sparre. 1994. The FAO­ ICLARM Stock Assessment Tools (FiSAT) User's Astorquí, LS. 1971. Peces de la cuenca de los grandes guide. FAO computerized Information Series lagos de Nicaragua. Rev. BioL Trop. 16: 86-99. (Fisheries)., No. 6. Rome, FAO. 186 p.

Bertalanffy, L. von. 1934. Untersuchengen uber die Hartnoll, J.L. 1974. Species interaction in assessment of Gesetzlichkeiten des Wachstums. l. Allgemeine fish-stocks with special application to the North sea. Grundlagen der Theorie. Roux' Arch. Entwicklungs Dana. 5: 1-44. mecho Org., 131: 613-653. In: Sparre, P. y S.e. Venema. 1994. Introducción a la evaluación de Holden, M.J. y D.F.S. raitt (eds.). 1975. Manual de recursos pesqueros tropicales. Parte Manual FAO L Ciencia Pesquera. Parte 2. Métodos para investigar Doc. Téc. Pesca. No. 306.1. Rev.!. 498 p. los recursos y su aplicación. Doc. Téc. Pesca. FAO. 115: 21 p. Beverton, RJ.H. & SJ. Holt. 1957. On the dynamic of exploited fishpopulations. Fish. Invest. 2: 533 p. McGinty, G.V. 1984. Biologicalversatility, evolution and food resource exploitation in African cichlids fishes. Bussing, w.A. 1987. Peces de las aguas continentales de Amer.Zool. 15: 427-454. Costa Rica. Editorial UnL Costa Rica., San José, Costa Rica. 271 p. McKaye, K. 1977. Competition of breeding sites between

Bussing, W.A. 1989. Cichlasoma loisellei, a new nandop­ the cichlids fishes of the Lake Jilaloa, Nicaragua., sis group fish from Central America. Rev. Ecology 58: 291-302. Biol. Trop. 37: 153-161. McKaye, K. 1980. Seasonalityin habitat selection by the Bussing, W.A. 1998. Peces de las aguas continentales de color morph of Cichlasoma citrinellum and its rele­ Costa Rica / Freshwater fishes of Costa Rica. vance to sympatric speciation in the family Editorial de la Universidad de Costa Rica. San José, Cichlidae. Env. Biol. Fish. 5: 75-78. Costa Rica. 2da. edición, 468 p. Meyer, A. 1987. Firts feeding success with two tytpes of Bussing, w.A. & M. Martin. 1975. Systematic status, vari­ prey by the Central American cichlids fish, ation and distribution of four Middle American cich­ Cichlasoma managuense (Pisces: Cichlidae): lids fishes belonging to the Amphilaphus species Morphology versus behaviour. Env. Biol. Fish. 18: group, genus Cichlasoma. Na!. Hist. Mus. L.A. Co., 127-134. Contrib. Sci. 269: 1-41. MilIer, R.R. 1966. Geographical distribution of Bussing, W.A. & M.L López. 1977. Distribución y aspec­ Central America freshwater fishes. Copeia 141: tos ecológicos de los peces de las Cuencas hidrográ- 773-802. INTERNATIONAL JOURNAL OF TROPICAL BIOLOGY AND CONSERVATION 485

Morales-Bojórquez, E. 1995. Estimación del tamaño Rosales, J. 1980. Un estimado preliminar sobre la densi­ poblacional y el coeficiente de capturabilidad de la dad por unidad de área y selección del tipo de hábi­ tilapia (Oreochromis aureus)por varios métodos de tat del guapote tigre Cichlasoma dovii en el sector de extracción sucesiva. INP-SEMARNAP. Ciencia Caño Negro. Trab. lnv. Tut. Esc. Cienc. Bio!. Pesquera 11: 40-44. Universidad Nacional. 56 p.

Moreau, J. 1988. Estimation of natural mortality from Sparre, P.E., S.C. Ursin and S.C. Venema. 1989. selection and catch length-frequency data: a modifi­ Introduction to tropical fish stock assessment. Part cation of Munro's method and application example. 1. Manual FAO.Fish. Tech. Pap., No. 306. 1., Rome, Fishbyte 6: 10-12. FAO. 337 p.

Moya, M.R. 1979. Estudio sistemático de los guapotes de Yáñez-Arancibia, A. 1980. Taxonomía, ecología y América Central (Osteichthyes: Cichlidae: Cichlasoma). estructura de las comunidades de peces en las lagu­ Tesis de grado Universidadde Costa Rica 79 p. nas costeras con bocas efímeras del Pacífico de México. Centro Cienc. Mar. Limno!., UNAM. Ricker, W.E. 1975. Computation and interpretation of bio­ Pub!. Esp.2: 1-306. logical statistics of fishpopulations. Bul!. Fish. Res. Board. Can. 382 p.