Biology Reproductive of Migratory Fish of the Sorocaba River, SP, Brazil
Andréia Camargo Portella1, Anderson Dalmolin Arsentales2, Welber Senteio Smith3
1
Graduate Student in Biological Science from Universidade Paulista and scholarship of scientific initiation PIBIC/CNPq. E-mail: andreia_portella@hotmail.com
2
Graduate Student in Biological Science from Universidade Paulista and scholarship of scientific initiation by “Pró- Reitoria de Pós Graduação e Pesquisa da Universidade Paulista”. 3
Doctor in Environmental Engineering Science by the Universidade de São Paulo and teacher of the Biological Science course of the Universidade Paulista.
Introduction
The biological knowledge is essential for the conservation, management and exploitation of the species (Theodore et al., 2002). In the case of fish farming potential, the value as a natural resource, the irrational exploitation and degradation of their environments become urgent and imperative that knowledge (Takahashi, 2006).
Among the many important biological aspects, the study of the reproductive process is a fundamental element, once its success depends on the recruitment and, consequently, the maintenance of viable populations, maintaining the environmental balance (Cavalcanti, 1994, Esper et al., 2000). According to Vazzoler (1996), know the strategies and tactics of the life cycle of fish allows better understand how these adapt to the environment and how they interact with the biotic and abiotic factors of the environment in which they live.
Despite the interest that migratory species arousing for several decades and the previous studies, few studies have investigated the biological aspects, especially the reproductive strategies of the reofilics species present in the Sorocaba River (Takahashi, 2006). However, this type of study is fundamental for understanding the ecological aspects of fish life. According to Vieira (1994) analysis of the behavior of the species appears to be of paramount importance because it is the reproductive migration that ensures the renewal of populational stocks and also ensures the preservation of such species.Thus, the knowledge of the dynamics of fish populations is of importance as scientifically as economically and socially. With the intention of contributing to the knowledge of reproductive aspects of fish communities, the objective of this work was to investigate aspects related to the reproduction of migratory species in the Sorocaba River, such as: breeding season, sex ratio, stage of maturation and migration efficiency.
Material and Methods
The Sorocaba River is the most important tributary of the left margin of the Tiête River, having 180 km of extension in a straight line and 227 km milk considering its natural path. Throughout of his journey, suffer two impoundments, the first in Votorantim, for the energetic use of Itupararanga leap and the second in Cerquilho, in the old San Juan power plant, where there is a ascent of the fish ladder (Smith, 2003; Smith et al., 2007; Smith et al.,
2009) (Figura 1). The stretches studied are located in the municipalities of Sorocaba and Cerquilho (23K0250022 UTM7395901 and 23K0214002 UTM7437161 respectively), where samples were collected monthly at a point on the river in each municipality during the period between September 2010 and April 2012.
Figure 1: Schematic map of the Sorocaba River basin, SP
The sample capture was realized with the utilization of castnets, after which were anesthetized with benzocaine and after tagged using a manual sewing needle with a 0,25mm nylon thread. The tag was inserted below of the dorsal fin, provided with at least two and at maximum four colored beads, which each color and amount of beads determined the specimen code. In the tag local it was applied methylene blue to prophylaxis. Were obtained the biometric data (standard length and total weight) and realized the sex identification. After these procedures these individuals were dropped at the capture local.
Some captured individuals were taken to laboratory where were obtained biological (maturation stage) and biometric data (standard length and total weight). The gonadal stage was determined using a stereomicroscope, or when possible, macroscopically, considering the following traits: colour, transparency, surface blood vessels, and oocytes aspect. According to a previously established scale, gonadal stages were classified into four categories: A = immature, B = in maturation or resting, C = mature and D = empty (Vazzoler, 1996).
Subsequently, these specimens were fixed in formalin (10%) and preserved in alcohol (70%). All material was properly identified with collection date, location and type of device used. Species identification was made through appropriate identification keys, and later confirmed by specialists. The research has a permanent license for collection of zoological material no. 24151-1 issued on 21/06/2010 by SISBIO.
Results and Discussion
During the study period were captured 391 individuals, distributed in 7 species, 4 families and one order. Of the total of captured individuals 257 specimens were tagged and dropped at the capture local and 134 were taken to the laboratory to obtain the biological and biometric data. The species sample were: Astyanax altiparanae (lambari-de-rabo-amarelo), Astyanax fasciatus (lambari-de-rabo-vermelho), Leporinus obtusidens (piava), Parodon nasus (canivete), Prochilodus lineatus (curimbatá), Salminus hilarii (tabarana) and Triportheus nematurus (sardinha).
Among the sampled environment the most abundant specie was the A. fasciatus with 154 captured individuals, representing 39,38% of the sample, of these 53,24% were captured in January and March 2012. Other captured species were A. altiparanae with 90 individuals, representing 23% of the sample, P. nasus with 67 individuals, representing 17,13%, P. lineatus with 39 individuals, representing 9,97%, S. hilarii with 35 individuals, representing 8,95%, L. obtusidens with 5 individuals, representing 1,2% and T. nematurus, with only 1 individual captured, representing 0,25% of the sample (Figure 2).
Figure 2. Abundance of species captured in the two sampling sites of the Sorocaba River.
As shown in the Figures 3 and 4, the greatest reproductive activity occurred in the months of November to January 2011 and January to March 2012, with the greater increase in catches of reofilics species, being then related to the months in which rainfall and temperature was elevated. According to Lowe-McConnell (1999) in tropical environments, it is clear the relationship between changes in precipitation levels and the migratory movements of fish, associated with increased reproductive activity during the floods (Vazzoler, 1996, Agostinho et al., 2000). According to Bye (1984), abiotic factors such as light and temperature are the most common triggers, since they control the rate of gonadal development, but other conditions (environmental, physiological and behavioral) are important in the period before to spawning.
Figura 4. Distribution of monthly medium values of air temperature and monthly medium values of rainfall level in the sampling period (September of 2010 to April of 2012).
According to Vazzoler and Menezes (1992), the reproductive period for the species of the Paraná River basin begins in October, when the temperature is elevated and the water level begins to rise, reaching the peak in December-January, when the rainfall level is high. This relationship between abiotic factors and gonadal maturation was observed during the study, with December as the month with the greatest reproductive activity. However not all years have uniform climate. Rains delay or good are in different years and this can alter the biological processes of reproduction (Takahashi, 2006).
The Table 1 shows, that the bigest frequency of captured species were in B stage gonads (in maturation) or in C stage (mature), already that the most individuals were captured during the piracema, when the abiotic factors (temperature and rainfall level) were highest favoring the gonadal maturation of the reofilics species. According to Vazzoler (1996) most of the species displays a periodicity in its reproductive process, beginning its gonadal development in a time previous to that of reproduction, and completing its gonadal maturation when the environmental conditions are appropriate to fecundation and offspring development (Vazzoler, 1996). June (1977) discusses the reproductive patterns found in some species of fish, and draws attention to the regularity of spawning, affirming the existence of a fundamental connection between the physiologic rhythm of the fish and environmental fac-tors.
Table 1. Frequency of maturity gonadal stages of the abundant species in the system during the whole sampling period and sampling sites (N = number of captured individuals, % A = percentage of individuals with immature gonads, % B = percentage of individuals with gonads in development, % C = percentage of individuals with mature gonads, % D = percentage of individuals with empty gonads).
Species N Maturity gonadal stages
%A %B %C %D Astyanaz fasciatus 44 9,09 31,81 38,63 20,45 Astyanax altiparanae 37 10,81 35,13 32,43 21,62 Parodon nasus 31 12,90 41,93 29,03 16,12 Prochilodus lineatus 10 10 40 40 10 Salminus hilarii 9 11,11 55,55 33,33 0 Leporinus obtusidens 2 0 0 100 0 Triportheus nematurus 1 0 0 100 0
In this study, as well in other work carried out with migratory species, there was a greater number of collected females compared to males (Morais-Filho & Schubart, 1955, Barbieri et al., 2001; Feitosa et al., 2004; Rodriguez & Taphorn-Olarte, 2006) (Table 1). It is verified that the seven species studied, the females were significantly predominant in three species - A. altiparanae, and S. P.lineatus hilarii. For A. fasciatus and P. nasus there was a balance in the sex ratio, not occurring, then, the predominance of females or males. For piava and sardinha because of the small sample was not possible to determine the sex ratio. According to Vazzoler (1996), the sex ratio of fish can change over its life cycle, with the mortality and growth the factors that act differentially on the sexes, at different stages of growth.
Table 2.Frequency of males and females captured during the sampling period (September 2010 to April 2012)
Species Sex %M %F Astyanax fasciatus 50 50 Astyanax altiparanae 44,44 55,55 Parodon nasus 49,25 50,74 Prochilodus lineatus 38,46 61,53 Salminus hilarii 42,85 57,14 Conclusions
It is evident for the reofilics species of the Sorocaba River, a standard of reproductive seasonality, resulting from the interaction between biotic and abiotic factors, because these factors act at gonad maturation, preparing them for reproduction. The advance or delay of the right conditions might influence and/or change the time that these species migrate to spawning.
Acknowledgements
The authors would like to thank PIBIC/CNPq and Pró-Reitoria de Pós Graduação e Pesquisa da Universidade Paulista - UNIP for the Scientific Initiation scholarship conceded.
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