Print version ISSN 1516-8913
Braz. arch. biol. technol. vol.42 no.4 Curitiba 1999
Marina Faria do Amaral; José Marcelo Rocha Aranha*; Márcia Santos de Menezes
Departamento de Zoologia, Universidade Federal do Paraná, CP 19020, CEP 81531-990, Curitiba, Paraná - Brasil
Studies were performed to determine the growth curves in length and weight for Pimelodella pappenheimi in the "das Pombas" stream, a coastal stream susceptible to the flash flood phenomenon. Samples were collected from September-95 to February-97, monthly, using electric fishing. The fishes were measured in total length and weight. A total of 156 pairs of otholits were taken for ring reading. The Ford-Walford transformation allowed the use of von Bertallanffy expression. The pale ring formation was annual, and it occurred between the summer and the autumn. This species grews in length according to Lt=15.86 (1-e-0.57(t+0.1551) ) equation and in weight according to Wt= 24.23 (1-e-0.57(t+0.1551) )3.12. The increase in length was faster until the second year of life, whereas the increase in weight was more noticeable between the first and fourth years of life.
Key word: Growth, Coastal Stream, Pimelodidae.
O crescimento de uma espécie é um mecanismo adaptativo da população em relação às características e às variações do meio ambiente. Este trabalho visa determinar as curvas de crescimento em comprimento e peso de Pimelodella pappenheimi no rio das Pombas, um rio costeiro sujeito a trombas d’água frequentemente. As coletas foram mensais de setembro/95 a fevereiro/97 usando pesca elétrica. Os peixes foram medidos no comprimento e peso total. Foram retirados 156 pares de otólitos para leitura dos anéis de crescimento e foi utilizada a expressão de von Bertallanffy. A formação dos anéis é anual e ocorre entre o verão e o outono. P. pappenheimi cresce em comprimento de acordo com a expressão Lt=15.86 (1-e-0.57(t+0.1551) ) e em peso conforme a expressão Wt= 24.23 (1-e-0.57(t+0.1551) )3.12. O aumento no comprimento é maior até o segundo ano de vida enquanto o aumento em peso é maior entre o primeiro e o quarto ano de vida.
The variable conditions of freshwater streams must have played a decisive role in the selection of flexible features, like fecundity, age at first maturation, and longevity, for example, so that the populations that live in those systems could be adjusted to the instability of the habitat (Mann et al., 1984). This heterogeneity makes these environments excellent models of studies in populations’ life histories and are useful for the understanding of the adaptative mechanisms to different environmental conditions.
The life histories of fish are strongly influenced by biotic and abiotic features of the environment. Several authors have demonstrated the capacity of the fish assemblage in adapting its population dynamic to the local conditions (e.g. Kramer, 1978; Lobon-Cervia et al., 1991). Considering the life history that characterises the ecology of fish, the study of growth can aid a lot in the understanding of the population structure and dynamic as a whole.
The rate of an individual's growth depends on the energy obtained by it and how this energy is used. The periods in which growth is slow are registered in some bony structures, as opaque rings, that are a result of a larger deposition of minerals. The periods in which growth is more accelerated correspond to hyaline areas in these structures. The periodicity of the ring formation is generally associated to seasonable factors, being the temperature a factor of larger prominence (e.g. Lagler et al., 1962), or as a result of internal and external processes simultaneously (e.g. Nikolsky, 1963). In tropical areas, where temperature variations are less strong, it has been more difficult to identify the responsible factors for the periodicity of ring formation. In these situations, it is important to study the possible parameters that should be acting in the formation of rings in these populations. Lagler et. al. (1962) mentioned the droughts as main factors of the periodicity of growth in tropical waters. Other authors related the formation of rings with the spawning (e.g. Gurgel & Barbieri, 1991).
There are few studies related with the growth of Pimelodidae fishes. Gurgel & Barbieri (1991), defined the age and growth for Rhamdia branneri; Fenerich et al. (1975) worked with Pimelodus maculatus, Nomura et al. (1972) with Pimelodus clarias, and Trajano (1991) with a troglobitic catfish Pimelodella kronei. The biology of Pimelodella pappenheimi was studied in relation to the feeding and space occupation (Aranha et al., in press) and to the reproductive strategy (Amaral et al., in press).
This paper aimed at of estimating the growth of Pimelodella pappenheimi in the "das Pombas" stream. More specifically, the objectives were to define the length-weight relationship and estimate the growth in length and in weight, defining its growth curves.
MATERIALS AND METHODS
In the "das Pombas" stream (Basin of the "Guaraguaçu" river, Municipal district of Paranaguá-PR, Fig 1), monthly samplies were collected between September/95 and February/97, with electric fishing. Approximately 15 fishes a month of P. pappenheimi were measured in total length (centimeters), weighed (milligrams) and dissected.
In laboratory, we chose individuals of various sizes to remove the Lapillus otholits pair.
The length-weight relationship was initially obtained for males and females separately, by the expression Wt = a .Lt b, by the minima square method. The straight lines estimated for males and females were compared to each other by the interval of confidence of the straight line (95% of confidence) estimated for all the contained data. These straight lines were obtained by the logarithmic transformation of the data. Using this methodology analysis was made if the straight lines obtained for males and females separately were contained in the interval of confidence for the straight line obtained for both sexes together. In case they were contained, it was considered that there were no differences between the equations of the straight lines of males and females. Otherwise, the sexes should necessarily be analysed separate.Otholits from small, medium and large size fishes were washed with water and detergent. These were immersed in xylene for clarification and observed in glycerine in order to read the rings. The material was observed on dark bottom, under stereoscopic microscope with reflected light. The reading of the rings was made according to Jones & Hynes (1950). The graphic of the segments was built according to the methodology proposed in Vazzoler (1981). The data were grouped in quarters and the number of rings was determined considering the formation of opaque rings. The Ford-Walford transformation was used according to Vazzoler (1981). The growth curve in length was obtained by the von Bertalanffy expression Lt = L∞ [ 1-e-k(t-t0)] . The growth curve in weight was obtained from the length-weight relationship associated to the expression of the curve of the growth in length Wt= W∞ [ 1-e-k(t-t0)] b.
The length of males ranged from 3.6 cm to 14.8 cm; and for females it ranged from 4.4 cm to 15.0 cm. The minimum and maximum values of total weight for the males were respectively 0.299 g and 16.853 g whereas for females, 0.388 g and 21.450 g.
The analysis of the length-weight relationship for males and females did not present differences, as the straight lines were in the same interval of confidence (Table I). This made it possible to analyse of the length-weight relationship for both sexes together, as represented in Figure 2.
We took out 156 pairs of otholits: 35 with zero opaque rings, 56 with one ring, 61 with two rings, and 4 with three rings. The formation of the ring was annual, occurring between summer and autumn.
The Ford-Walford transformation (r2=0.97) allowed the use of von Bertalanffy model. The individuals grew in length according to the expression Lt = 15.86 [1-e-0.5782(t+0.1551)] represented graphically in Figure 3. The growth in weight was according to the expression Wt = 24.23 [1-e-0.5782(t+0.1551)]3.12, represented in Figure 4.
Pimelodella pappenheimi in the "das Pombas" stream, did not present difference in the length-weight relationship for males and females. For this reason, the data of P. pappenheimi were analysed considering the sexes together, differing from the analysis of the Rhamdia branneri data (Gurgel & Barbieri, 1991), in which the sexes were analysed separately.
Even though analysed only 156 pairs of otholits, (against 977 pairs of otholits by Gurgel & Barbieri, 1991 and 1321 vertebrae by Agostinho et al., 1991). Even so, we obtained a high value for the coefficient of determination (r2), which was a strong evidence that the data were representative, and this allowed the application of von Bertalanffy expression. Besides that, collected samples in streams must be certainly smaller than those obtained in large rivers, as in the researches mentioned above. In streams, the populations are smaller and the individuals' excessive capture could be harmful for the whole community.
The period of formation of the rings coincides with the end of the reproductive period of the species (Amaral et al., in press). However, we believe that the strong environmental changes at the end of the summer, as flash floods changing the assemblage and the food availability, should be determining the formation of rings.
The growth curves demonstrated that P. pappenheimi grew faster than Rhamdia branneri, whose growth was verified by Gurgel & Barbieri (1991). P. pappenheimi presented rate of growth of 0.57, whereas in Rhamdia branneri, it was 0.21 for females and 0.28 for males. It was observed that the growth in length of P. pappenheimi was more accentuated until the second year of life, becoming slower in the following years, while the growth in weight was more accentuated between the first and the fourth years of life.
The values obtained for L∞ and W∞ were very close to the values found for the biggest fishes collected in the "das Pombas" stream. It is a reason for reliability in the data.
Vazzoler (1971), reported that there was a relationship between the values of K, longevity, and L∞ . The individuals in which the growth was faster (K is high), the longevity was shorter and the maximum lengths reached were smaller too. This can be verified when P. pappenheimi was compared with the troglobitic Pimelodella kronei (Trajano, 1991). P. pappenheimi, presented K=0.57, its asymptotic length was 15.86 cm and the species lived until approximately four years. P. kronei, whose K=0.0898; presented L∞ = 15.4 cm and lived approximately from 10 to 15 years.
In unstable environment, it was important that the species develop tactics to survive and to leave offspring. Pimelodella pappenheimi presented fast growth and development. These tactics were of great importance for species with a short life period. The fast development leads to facts as, for example, a great swimming capacity in young, and precocious reproduction. The species in subject reproduced early, its length at the sexual maturation was 6.3cm (Amaral et al., in press), which corresponded to individuals of approximately one year of life.
The authors thank Denise de F. Takeuti and other friends who helped during samplings, Dr Carlos Lucena (PUC-RS) for identifying the species and CNPq for the scholarship to M.F. Amaral and for partial financial support (process number 52.1597/95-1)
Agostinho, A. A., Barbieri, G. & Verani, J. R. (1991). Idade e crescimento do cascudo preto Rhinelepis aspera (Siluriformes, Loricariidae) no rio Paranapanema, Bacia do rio Paraná. Revista UNIMAR, Maringá 13(2), 259-272p [ Links ]
Amaral, M.F., Aranha, J.M.R. & Menezes, M.S. (in press) Reproductive aspects of the freshwater catfish Pimelodella pappenheimi in Southern Brazil. Studies on Neotropical Fauna and Environment 33 [ Links ]
Aranha, J.M.R., Takeuti, D.F. & Yoshimura, T. M. (in press). Habitat use and food partitioning of the fishes in a coastal stream of Atlantic Forest, Brazil. Revista de Biologia Tropical 46(4), 955-963 [ Links ]
Fenerich, N. A., Narahara M. Y. & Godinho H. M. (1975). Curva de crescimento e primeira maturação no bagre Pimelodus maculatus. Bolm Inst. Pesca 4, 15-28 [ Links ]
Gurgel,H. C. B. & Barbieri G. (1991). Idade e crescimento do bagre amarelo, Rhamdia branneri Haseman,1911 (Siluriformes, Pimelodidae) do rio Iguaçu/Paraná. Revista UNIMAR 13(2), 248-258 [ Links ]
Jones, J. W. & Hynes, B. N. (1950). The age and growth of Gasterosteus aculeatus, Pygosteus pungitius and Spinachia vulgaris, as shown by their otoliths. Journal Animal Ecology 19, 59-73 [ Links ]
Kramer, D.L. (1978). Reproductive seasonality in the fishes of a tropical stream. Ecology 59(5), 976-985 [ Links ]
Lagler, K. F., Bardach, J. E. & Miller, R. R. (1962). Ichthyology. Jonh Wiley and Sons, Inc. New York [ Links ]
Lobon-Cervia J., Montanes C. & Sostoa A. de (1991). Influence of environment upon life history of gudgeon, Gobio gobio (L.): a recent and successful colonizer of the iberian peninsula. J. Fish Biol. 39, 285-300 [ Links ]
Mann, R.H.R., Mills,C.A. & Crisp, D.T. (1984). Geographical Variation in the Life-History Tactics of some Species of Freshwater Fish. In.: Fish Reproduction: Strategies and Tactics (Wootton, R.J. & Potts, G.W, ed.), Academic Press, 171-186p [ Links ]
Nikolsky, G. V. (1963). The ecology of fishes. Academic Press Inc., London [ Links ]
Nomura H., Pozzi R. & Manreza F. A. (1972). Caracteres merísticos e dados biológicos sobre o mandi amarelo, Pimelodus clarias (Bloch, 1782) do rio Mogi Guaçu (Pisces, Pimelodidae). Revista Brasileira de Biologia 32(1), 1-14 [ Links ]
Trajano, E. (1991). Population ecology of Pimelodella kronei, troglobitic catfish from Southeastern Brazil (Siluriformes, Pimelodidae). Environmental Biology of Fishes 30, 407-421 [ Links ]
Vazzoler, A. E. A. de M. (1971). Diversificação fisiológica e morfológica de Micropogon furnieri (Desmarest, 1822) ao sul de Cabo Frio, Brasil. Bolm. Inst. oceanogr. São Paulo, 20(2), 1-70 [ Links ]
Vazzoler, A. E. A. de M. (1981). Manual de métodos para estudos biológicos de populações de peixes reprodução e crescimento. Brasília, CNPq. Programa Nacional de Zoologia [ Links ]
Received: December 21, 1998
Revised: January 11, 1999
Accepted: May 14, 1999.
* Author for correspondence