Population aspects of Bryconamericus stramineus in streams of the upper Paraná River basin, Brazil

Abstract

Abstract:In order to describe some aspects of the population ecology of Bryconamericus stramineus in the Guiraí River basin, upper Paraná River basin, samples were taken bimonthly from October 2006 to August 2007 at seven sites in the basin. A total of 960 individuals, including 532 females, 316 males, and 112 of undetermined sex, were collected. A significant variation in the sex ratio was observed (χ 2 = 32.82; p < 0.001). Females were larger (59.7 mm) than males (58.9 mm); however, males showed a larger angular growth coefficient (b) than females. It was estimated that 50% of females were sexually mature at 36.4 mm. The highest rate of ovary development was observed in October, while in June 2007 no mature females were found. Mean fecundity was estimated at 313 eggs, and the relative fecundity was 184.6 eggs/g. The asymptotic was estimated at 62.8 mm and the growth rate at 0.76. The growth performance index was calculated at 3.47, the longevity at 3.94 years and the mortality (M) at 1.18 years. The recruitment pattern of the species showed peaks concentrated in periods of low rainfall. Keywords: length-weight relationship, mortality, reproductive strategy, sex ratio. Neotrop., vol. 11, no. 2 In which season does reproductive activity of B. stramineus increase in the streams sampled? 5) What is the mean standard length at which females reach first maturation? 6) Is there any relationship between fecundity and the size of females? 7) Are seasonal differences in recruitment patterns for studied population? 8) What are the growth and mortality parameters for B. stramineus in sampled streams? Material and Methods Study siteThe Guiraí River basin (22° 45' S, 54° 30' W and 22° 15' S, 53° 30' W), occupies an area of approximately 2,248 km 2 and includes seven municipal districts. The mouth of the Guiraí River is located at an altitude of 370 m a.s.1., and the river flows for approximately 100 km until it enters the Ivinhema River, at 238 m of altitude. In its lower portion, it forms the boundary of the Parque Estadual das Várzeas do rio Ivinhema. Field and laboratory methodsThe fish samples were taken bimonthly from October 2006 to August 2007 at seven sites in the Guiraí River basin (Figure 1). The streams were selected for their location in the basin and ease of access.The samples were taken during daylight, with a rectangular sieve measuring 1.2 × 0.8 m (2 mm mesh size) and standardized effort (20 throws) at each site, with approximately 100-m long hauls. The equipment was slide to sweep the substrate toward the banks of the stream. This technique was used because of the difficulties of using the electric fishing in these streams, such as low electrical conductivity and high turbidity, and also due to difficult access. The permission for fish retrieval was granted by IBAMA (#13458-1).Specimens were fixed in 10% formalin and preserved in 70% ethanol for subsequent identification. Voucher specimens were deposited at the Coleção de Peixes do Nupelia (NUP/UEM # 9322).In the laboratory, some biometric data were mea...

Life-history traits of Farlowella hahni (Siluriformes, Loricariidae) in streams of the Ivinhema River Basin, Upper Paraná Basin

“…The positive relationship between fecundity and female length is common (Vasconcelos et al, 2011); on the other hand, the lower fecundity observed for F. hahni is consistent with that observed for F. vittata (mean=46 oocytes). The higher mean values for F. hahni suggest that this could be a characteristic trait of this fish group.…”

Relationships Between Environmental Conditions And Fish Assemblages In Tropical Savanna Headwater Streams

“…This behavior can explain its ability to exploit the watercourse substrates, which are covered by fine sediments 56 that are transported by water, and its capacity to survive in streams that have remarkable seasonal oscillation in turbidity, with lower values during the dry period and higher values in the rainy period 82 . On the other hand, the characin B. stramineus is a predominantly insectivorous 83 active swimmer 84 that is abundant in shallow streams of the Upper Paraná basin with elevated turbidity 83,85 and water velocity 85 . The relationship of C. zebra with water turbidity is unexpected considering that it is an indicator species of pristine environments, with a sit-and-wait behavior for capturing prey 86 and rheophilic preferences that can be affected by high levels of suspended sediments in the water column and the resulting siltation of the substrate 54 .…”

Maturity, fecundity, and reproductive cycle of Conodon nobilis (Actinopterygii: Perciformes: Haemulidae) in tropical waters of the Atlantic Ocean

“…Higher proportions of adult females in natural populations may be associated with many factors, such as the birth rate, growth characteristics, mortality, and fish behaviour (Dala-Corte and Azevedo 2010). This predominance of one sex in fish populations, however, may also be an indicator of stress caused by natural and anthropogenic activities (Vasconcelos et al 2011). Specifically, when faced with high predation rates and/or overexploitation, a species may display differences in the sex ratio as a compensatory response to the quickly increasing population size (Súarez et al 2017).…”