Growth, recruitment, and mortality parameters for Astyanax. (Pisces, Characidae) in the Upper Paraná River floodplain, Brazil

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1 Growth, recruitment, nd mortlity prmeters for Astynx ltiprne Grutti nd Britski, 2 nd A. schurti,, Britski, 196 (Pisces, Chrcide) in the Upper Prná River floodplin, Brzil Mri de los Angeles Perez Lizm* nd Angel Mri Amrosio Núcleo de Pesquiss em Limnologi, Ictiologi e Aqüicultur (Nupéli)/PEA, Universidde Estdul de Mringá, Av. Colomo, 579, 872-9, Mringá, Prná, Brsil. *Author for correspondence. e-mil:lizmmp@nupeli.uem.r ABSTRACT. Dt for the chrcid Astynx ltiprne nd A. schurti, collected from Mrch 1993 to Ferury 199, were used for studies of growth, recruitment, nd mortlity. The results for the A. ltiprne indicted symptotic growth (L ) of 18.cm (stndrd length) nd growth rte (k) of.26; the totl mortlity (Z) estimted from the different methods ws 2.23 nd two recruitment periods were oserved during the yer, one in Mrch nd the other in Novemer, coinciding with the reproductive seson of the species. For A. schurti k vlue of.25 nd n symptotic length vlue of 12.cm were otined; the nturl mortlity rte ws.8; for this species two recruitment periods were lso oserved, the first coinciding with the highest spwning level, nd the second soon fterwrds. Key words: Astynx ltiprne, A. schurti, FISAT, growth, mortlity, Brzil. RESUMO. Crescimento, recrutmento e mortlidde de Astynx ltiprne Grutti & Britski, 2 e A. schurti, Britski, 196 (Pisces, Chrcide) n plnície de inundção do lto rio Prná, Brsil. Ddos dos crcídeos Astynx ltiprne e A. schurti, coletdos entre mrço de 1993 e fevereiro de 199, form utilizdos nos estudos do crescimento, recrutmento e mortlidde. Os resultdos pr A. ltiprne indicrm o crescimento ssintótico (L ) de 18,cm (comprimento pdrão) e tx de crescimento (k) de,26; mortlidde totl (Z) estimd trvés de diferentes métodos foi de 2,23 e o dois picos de recrutmento form oservdos durnte o no, um em mrço e o outro em novemro, coincidindo com estção reprodutiv d espécie. Pr A. schurti o vlor de k foi de,25 e o comprimento ssintótico otido foi de 12,cm; mortlidde nturl foi de,8; pr est espécie dois períodos de recrutmento tmém form oservdos, o primeiro coincidindo com o nível lto de desov e o segundo pós este período. Plvrs-chve: Astynx ltiprne, A. schurti, FISAT, crescimento, mortlidde, Brsil. Introduction Knowledge of the prmeters of growth, recruitment, nd mortlity of fish species is very importnt for studies of fisheries iology, nd it is fundmentl for rtionl mngement of fish stocks (Wetherly nd Gill, 1987; Brothers, 1987; Ferreir nd Russ, 199). According to Antoniutti et l. (1985), growth is the quntittive spect of development; therefore, knowledge of its chrcteristics constitutes importnt informtion out the popultion dynmics. The tmiú, Astynx ltiprne nd the lmri de ro mrelo A. schurti, re fodder species, i.e. mximum length less thn 2cm nd serve s food for mny other species of fishes, irds, nd other nimls. These species re extremely importnt ecuse they re dominnt on the floodplin (Agostinho et l., 1997), in ddition to serving s key link in the food chin nd in mintining the equilirium of this importnt ecosystem. Study of the life cycle of the tmiú is reltively recent. Only one investigtion, on growth of A. imcultus (A. ltiprne ws considered for long time s A. imcultus), ws previously crried out in Brzil, y Sntos et l. (1991). For A. schurti the life cycle ws studied y Nomur et l. (1975,, c) nd Gims et l. (1992). This study is prt of series of investigtions on the iology of the principl fodder species in the Upper Prná River floodplin. Fodder species re so nmed ecuse of their smll size, nd ecuse support mny piscivores of the region. The ojective of this study ws to estimte the growth prmeters nd ptterns of

2 38 Lizm nd Amrosio recruitment nd mortlity of Astynx ltiprne nd A. schurti, from the Upper Prná River floodplin, Mto Grosso do Sul Stte, Brzil. Mteril nd methods The specimens were collected monthly on the Upper Prná River floodplin (22 o '-22 o 5'S nd 53 o 15'-53 o 'W) (Figure 1), from Mrch 1993 through Ferury 199. Stndrdized huls nd sttionry nets of 3cm etween opposite knots were used. A susmple ws used to estlish the length frequency distriution. The stndrd length ws mesured in centimeters. The nlysis ws performed using the progrms ELEFAN I nd II (Gynilo et l., 1989), to estimte the prmeters discriminting growth, recruitment, nd mortlity. For the nlyses, 18 A. ltiprne specimens nd 661 A. schurti specimens were used. t o = ws dopted, since the vlue otined from the empiricl formul of Puly (198) for oth species is improle for them. The eqution of Beverton nd Holt (1957) nd the eqution of Ault nd Ehrhrdt (1991), inclused in the FISAT progrm (Gynilo et l., 1996), ws used to estimte totl mortlity (Z). Nturl mortlity (M) ws clculted y the empiricl formul of Puly (198), nd the eqution of Rikhter nd Efnov (1976) ws otined using FISAT. The mortlity from fishing (F) nd the exploittion rte (E) were derived from the vlues de Z nd M otined using ELEFAN. Results nd discussion 1. Growth The rw dt were restructured with ELEFAN I, plotting the curves (Figure 2) from the growth prmeters determined from the distriution. The growth prmeters permitted us to otin von Bertlnffy's eqution for the species SL=L [1-e k(t-t) ] (SL = Stndrt length), therefore: SL = 18. [ 1-e -.26(t) ] for A. ltiprne nd; SL = 12. [ 1-e -.25(t) ] for A. shurti For A. ltiprne (Figure 2), the results indicted tht this species reched n ge of yers, the lst yer not eing represented. Sntos et l. (1991) oserved for A. imcultus (for long time A. ltiprne ws considered A. imcultus), tht the species presented 17.8cm (L) nd.21 (k). For the sme species, Nomur et l. (1975) oserved similr results. In this work, the vlues k were higher (.26). Results show tht the smll size of the species tht growth rte (k) is typicl of species with short life cycles on the floodplin. SOUTH AMERICA 53º 15 BRAZIL Ivinheim River MATO GROSSO DO SUL Bí River 22º 5 22º 5 Corutu Chnnel N Florest islnd Prná River PARANÁ PORTO RICO Ivinheim River 23º 23º 53º 3 Figure 1. Mp of the Upper Prná River floodplin. km Legend Field Sttion of Nupéli Direction of flow

3 Growth prmeters for Astynx ltiprne nd A. shurti 39 Length (cm) 8 Mr Apr My Jun Jul Aug Sep Oct Nov Dec Jn Fe Ln (N) 8 6 Length (cm) 6 2 Mr Apr My Jun Jul Aug Sep Oct Nov Dec Jn Fe Figure 2. Growth curve superimposed over the reestructured length-frequency dt for ) Astynx ltiprne nd ) A. schurti in the Upper Prná River floodplin (L = 18.cm, k =.25 yer- 1 ) Reltive ge For A. schurti, the growth curves clculted using ELEFAN I indicted three complete nd one incomplete cohort (Figure 2). The species reched n symptotic length (L ) of 12.cm nd growth rte (k) of.25. The numer of cohorts ws similr to tht found for femles of the sme species y Gims et l. (1992) using the method of retroclcultion, ut symptotic length ws lower in this work. It is importnt to emphsize tht the mplitude of size found y the uthors ws higher. The vlue for symptotic length is slightly higher thn the mximum size of.6cm recorded for this species y Vzzoler (1996). Results found y Nomur et l. (1975) showed tht the symptotic length of the mles is much lower thn tht of the femles, s the vlues of k hd een much higher. The results otined cn e relted to the presence of mles in the smpling used for re-nlysis. Higher vlues of k hd een re-nlyzed, ut the results of Rn (etter it djust of the curve) were very low. 2. Mortlity The vlues for totl mortlity (Z), nturl mortlity (M), mortlity from fishing (F), nd the exploittion rte (E) for A. ltiprne nd A. schurti, otined from the length-converted ctch curve (Figure 3) nd y other methods pper in Tle 1. Tle 1. Results for prmeters of totl mortlity (Z), nturl mortlity (M), mortlity from fishing (F) nd exploittion rte (E) for Astynx ltiprne nd A. schurti on the Upper Prná River floodplin, Brzil. Z M F E Species A. ltiprne A. schurti = length-converted ctch curve; 2 = Beverton nd Holt (1957); 3 = Ault nd Ehrhrdt (1991); = Men vlues; 5 = Puly (198); 6 = Rickhter nd Efnov (1976); 7 = Men vlues; 8 = Derived from men vlues F=Z-M; 9 = Derived from mens vlues y the eqution E=F/Z Ln (N) Reltive ge Figure 3. Length-converted ctch curve of ) Astynx ltiprne nd ) A. schurti in the Upper Prná River floodplin. For A. ltiprne, the gretest difference mong vlues ws found for totl mortlity (Z). Z otined y the length-converted ctch curve is high. Other methods did not show gret difference. The men vlue is indicted s the finl result of this estimte. Nturl mortlity is low nd the vlues from mortlity y fishing nd the exploittion rte re higher. For A. schurti the results of the estimtes re lower thn those of A. ltiprne. Men Z is As regrds nturl mortlity, there is no difference etween the diverse methodologies used. Results of mortlity y fishing nd the exploittion rte re lower thn ones for tmiú, ut the vlues re still considered high. Nturl mortlity for oth species is low nd mortlity y fishing nd the exploittion rte hd een very high. These species re poorly exploited nd renews themselves nturlly, nd re the preferred food of mny other species of fish, irds, nd other nimls. The most logicl result to consider tht the nturl mortlity either high nd F nd E is low. In this wy, Z either hd exclusively to M. Therefore, oth species cn consider totl

4 Lizm nd Amrosio mortlity s eing 2.23 for A. ltiprne nd 1.65 for A. schurti. According to Puly (198), nturl mortlity is the result of three components: physiologicl mortlity, cused y disese, old ge, or oth (in the sence of predtors); selective mortlity, cused y diminished performnce of individuls, ecuse of disese, old ge, or oth, mking them ccessile to predtors; nd risk mortlity, unrelted to ny physiologicl mechnism, nd proportionl only to the proility of encountering potentil predtors; this component predomintes in smll fish. Becuse of the smll size of A. ltiprne nd A. schurti, the high rte of nturl mortlity is included in the risk component, which is quite lrge. 3. Recruitment Both species presented two periods of recruitment relted to the reproductive periods. (Figure ). Recruitment Recruitment Mr Apr My Jun Jul Aug Sep Oct Nov Dec Jn One yer Figure. Recruitment pttern of ) Astynx ltiprne nd ) A. schurti in the Upper Prná River floodplin. For A. ltiprne, the results indicted two periods of recruitment, one in Mrch-April nd nother of high intensity in Novemer (Figure ). The monthly distriution of length clss frequencies (Figure 5) implied tht juvenile individuls enter the popultion minly in Mrch-April, when the species is t the end of its reproductive period, nd lso during Novemer, when it is eginning reproduction (Vzzoler, 1996). However, initil length clsses (1.8cm) were present during the entire yer (Figure 5). For A. schurti (Figures nd 5) ws oserved the occurrence of two recruitment periods, one in My-June, nd the second coinciding with the Fe reproductive pek (Novemer). The occurrence of two min recruitment periods in tropicl region ws expected. In this system recruitment is not continuous, since the entry of juveniles follows sesonl ptterns relted to reproduction, which is centuted in floodplin species (Winemiller, 1989). Although the two species cme in mixed schools, the differences oserved in the growth cn e due to diverse fctors, eing possile detch: the genetic drift, gondl development nd the potentil of growth of ech specie, s well s resulting of the difference etween the hit feed (A. ltiprne cn e considered insectivorous nd A. schurti herivorous). Acknowledgements This rticle is prt of the multidisciplinry project "Environmentl studies of the Prná River floodplin in the re encompssing the mouth of the Prnpnem River nd the Itipu Reservoir", undertken with the ssistnce of PADCT/CIAMB. The uthors thnks CNPq for finncil support nd Nupéli (Núcleo de Pesquiss em Limnologi, Ictiologi e Aqüicultur) for logisticl support nd Dr. Jnet W. Reid for trnslting the text into English. References AGOSTINHO, A.A. et l. Composição, undânci e distriuição espço-temporl d ictiofun. In: VAZZOLER, A.A. et l. (Ed.). A plnície de inundção do lto rio Prná. Aspectos físicos, iológicos e socioeconômicos. Mringá: EDUEM, p ANTONIUTTI, D.M. et l. Relção peso totl/comprimento totl, crescimento e idde do Plecostomus lopuncttus Regn, 198 (Osteichthyes, Loricriide) do rio Jguri, São Pulo, Brsil. Boletim do Instituto de Pesc, São Pulo, v., p.5-12, AULT, J.S.; EHRDARDT, N.M. Correction to thew Beverton nd Holt Z-estimtor for truncted ctch length-frequency distriutions. ICLARM Fishyte, Sn Diego, v. 9, n.1, p.37-39, BEVERTON, R.J.N.; HOLT, S.J. On the dynmics of exploited fish popultions. Min. Agr. Fish nd Food, Fish. Invest., v.2, n.9, p.1-533, BROTHERS, E.B. Appliction of otolith microstruturl studies to ge determintion of some commercily vlule fish of rin gulf. Kuwit Bull. Mr. Sci., Slmiy, v.9, p , FERREIRA, B.P.; RUSS, G.R. Age vlidtion nd estimtion of growth rte of the corl trout, Plecostumus leoprdus, (Lcepede 182) from Lizrd Islnd northem gret rrier reef. Fish Bull., Wshington, DC, v.92, n.1, p.6-55, 199.

5 Growth prmeters for Astynx ltiprne nd A. shurti Mrch/93 April My June July August 5 3 Frequency (%) Septemer Octoer Novemer Decemer Jnury/9 Ferury Length clss (cm) 8 Mrch/93 April My June July August 6 Frequency (%) Septemer Octoer Novemer 2 8 Decemer Jnury/9 Ferury Length Clss (cm) Figure 5. Distriution of length clss frequency, y month, for ) Astynx ltiprne nd ) A. schurti on the Upper Prná River floodplin.

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