Modelagem do crescimento do tambaqui (Colossoma macropomum Cuvier, 1816): Seleção de modelos e inferência multimodelos

The tambaqui, Colossoma macropomum, is one of the most commercially valuable Amazonian fish species, and in the floodplains of the region, they are caught in both rivers and lakes. Most growth studies on this species to date have adjusted only one growth model, the von Bertalanffy, without considering its possible uncertainties. In this study, four different models (von Bertalanffy, Logistic, Gompertz and the general model of Schnüte-Richards) were adjusted to a data set of fish caught within lakes from the middle Solimões River. These models were adjusted by non-linear equations, using the sample size of each age class as its weight. The adjustment evaluation of each model was based on the Akaike Information Criterion (AIC), the variation of AIC between the models (Δi) and the evidence weights (wi). Both the Logistic (Δi = 0.0) and Gompertz (Δi = 1.12) models were supported by the data, but neither of them was clearly superior (wi, respectively 52.44 and 29.95%). Thus, we propose the use of an averaged-model to estimate the asymptotic length (L∞). The averaged-model, based on Logistic and Gompertz models, resulted in an estimate of L∞=90.36, indicating that the tambaqui would take approximately 25 years to reach average size

Light intensity affects the survival and growth of matrinxã larvae, Brycon amazonicus (Spix & Agassiz, 1829)

We evaluated the effect of light intensity on survival rate and zootechnical performance in matrinxã larvae (Brycon amazonicus) that is an important species for fish farming in the Amazon region. For this, the larvae were submitted to three experimental stages: Stage I—10–72 hr after hatching (HAH), Stage II—72–168 HAH and Stage III—168–288 HAH. The animals were submitted to three treatments of different light intensities: low (±20 lx), intermediate (±200 lx) and high (±2,000 lx). The low light intensity increased the survival rate in 24, 48, 72, 120, 168 and 288 HAH. The size of the animals was homogeneous in 72 and 168 HAH in the low and intermediate treatments. The high light intensity increased the zootechnical parameters in 288 HAH. We suggest the use of low light intensity in the initial periods of observation (24 and 48 HAH) to reduce aggressiveness and increase the survival and homogeneity of the animals. On the other hand, it is possible to suggest an increase in the light intensity in the final period of observation (288 HAH), as the increase in intensity stimulated growth and affected the survival rate of the matrinxã larvae. © 2019 John Wiley & Sons Lt

Lower light intensity reduces larval aggression in matrinxã Brycon amazonicus

Brycon amazonicus shows a high frequency of aggressive behavior, which can be a limiting factor in intensive farming systems. Environmental changes can modulate the social interactions of fish and reduce aggression during the different stages of production. Groups of three larvae at 12 h after hatching (HAH) were subjected to different levels of light intensity: low (17 ± 3 lx), intermediate (204 ± 12.17 lx) and high (1,613.33 ± 499.03 lx), with eight replicates for each level. The lower light intensity reduced the frequency of aggressive interactions and locomotor activity exhibited by the animals. Based on these results, light intensity modulates aggression in B. amazonicus larvae. Manipulation of this factor could improve the social conditions of this species during farming and contribute to the development of new production technologies. © 2018 Elsevier B.V

Stocking density and water temperature as modulators of aggressiveness, survival and zootechnical performance in matrinxã larvae, Brycon amazonicus

The matrinxã (Brycon amazonicus) presents zootechnical potential for commercial production, it is considered a species of interest due to its rapid growth and high-quality meat. However, one of the difficulties this species faces in the breeding system is the reduced supply of juveniles, mainly due to aggressiveness during larviculture. The purpose of the study was to evaluate the effect of stocking density and water temperature on the aggressiveness, survival and performance of matrinxã larvae. Two experiments were carried out: Experiment I: 12 h after hatching (HAH) were kept at three stocking densities (low: 20 larvae/l, intermediate: 40 larvae/l and high: 60 larvae/l), up to 72 HAH, with 5 replicates each. During the experimental period, 10-min videos were made in both periods (12 and 72 HAH) to quantify the behavior of the larvae and to evaluate the zootechnical performance. Experiment II: the 72 HAH larvae were submitted to six experimental treatments for up to 132 HAH. These derived from the association of three stocking densities (low: 20 larvae/l, intermediate: 40 larvae/l and high: 60 larvae/l) with two temperatures levels (low: 24.09 ± 0.15 °C and high: 28.33 ± 0.12 °C). The same procedure used in experiment I was used here in order to analyze the aggressiveness, survival and zootechnical performance. The results showed that the higher stocking density increased the aggressiveness, however, without affecting the other parameters up to 72 HAH. Nevertheless, after 72 HAH, the density did not affect the aggressiveness, it stimulated increased biomass and production instead. It was observed that the lowest temperature of the water reduced the aggressiveness and provided more homogeneous sizes among the animals in the group, nonetheless, it reduced the growth of the larvae. The results obtained indicated that the use of different densities is recommended depending on the period of larval development, that is, the density of 40 larvae/l in the initial stages of life (up to 72 HAH) and 60 larvae/l after this period; the maintenance of larvae at temperatures close to 24 °C is also recommendable since it provides less aggressive individuals with lower differential growth within the group, which may increase the survival rate in the medium and long term during the matrinxã larviculture. © 2018 Elsevier B.V

Sperm abnormalities in matrinxã Brycon amazonicus after hormonal treatment with carp pituitary extract and Ovaprim™

The aim of this study was to evaluate if hormonal treatment causes changes in the morphology of matrinxã Brycon amazonicus spermatozoa. Twelve males were randomized into three treatment groups: 1, Ovaprim™ (0.5 ml/kg); 2, carp pituitary extract (CPE; 2.0 mg/kg); and 3, NaCl solution 0.9% - control group (0.5 ml/kg); with four replicates. Morphological sperm analysis was performed using an optical and scanning electron microscope. The percentage of normal spermatozoa (49.6±4.6% to 60.8±2.8%), with primary (26.1±6.4% to 45.3±4.5%) and secondary abnormalities (4.4±2.9% to 13.9±3.5%) did not differ significantly between treatment groups. There were no significant differences between treatments in relation to the primary abnormalities found in the head (10.5±3.8% to 25.5±6.3%), the midpiece (0.1±0.1% to 0.2±0.2%) and in the flagellum (18.9±3.8% to 15.5±3.1%), as well as in the secondary abnormalities, located in the head (0.8±0.4% to 7.8±4.6%) and in the flagellum (2.2±1.1% to 6.1±1.5%). When each abnormality was evaluated individually, only the percentage of degenerated head was higher in the CPE-induced group (24.9±5.9%) than the control group (7.2±3.1%). We concluded that the use of pituitary extract of carp or Ovaprim™ under the conditions of this experiment does not influence the percentage of sperm abnormalities in B. amazonicus. © Cambridge University Press 2018

Aggressiveness and locomotion activity related to hatching time in Matrinxã, Brycon amazonicus (Spix and Agassiz, 1829)

Since agonistic interaction has been a major obstacle for fish hatchery and represents great economic losses for fish farmers, aggressiveness during the different post-hatching stages of the matrinxã, Brycon amazonicus, is analyzed and compared. Each group of three larvae was observed at six different sessions: 12, 24, 36, 48, 60 and 72. ±. 2. h after hatching (HAH) for 20. min, with 10 repetitions for each treatment. Aggressive behavior and motor activity were described by an ethogram: approach, attack, chase, flight, frontal display, mouth fight, mouth opening, threat, circular and linear swimming, contact and Ω-posture. Biometric measurements have indicated an increase in total length and mass (P<. 0.001). Number of aggressive behaviors (12 HAH: 95.80. ±. 14.68; 24 HAH: 53.40. ±. 20.99; 36 HAH: 12.40. ±. 9.44; 48 HAH: 22.80. ±. 18.89; 60 HAH: 35.20. ±. 17.57 and 72 HAH: 92.40. ±. 28.54, P<. 0.001) and duration of motor activity (12 HAH: 1446.70. ±. 160.70; 24 HAH: 453.10. ±. 184.95; 36 HAH: 100.50. ±. 42.18; 48 HAH: 22.8. ±. 110.30; 60 HAH: 99.10. ±. 23.83 and 72 HAH: 822.90. ±. 361.28, P<. 0.001) in the group was higher at 12 and 72 HAH. Results suggest that lower motor activity reduced the probability of encounters between larvae and, therefore, social interactions between group members of B. amazonicus. © 2014 Elsevier B.V

Fish communities in central Amazonian white- and blackwater floodplains

In Amazonian floodplains, the flood cycle of the river is becoming the dominant season al factor, and fish communities are found to fluctuate greatly over the year. During inundation, fish migrate into floodplain forests to feed on fruits and seeds, in an area more than 300 000 km2 in size. To document patterns of species diversity, distribution, abundance and temporal dynamics and in order to describe the ecological importance of the inundated forest, floodplain fish were captured using variously sized gill nets in white and black water areas inside and outside the floodplain forests during low, rising, high and falling water level in 1990 and 1991. Dominance varies to some extent in white water between floodplain forest (0.06) and open water (0.11) while it is unchanged in black water (0.04). Black water fish communities were more diverse. Most abundant among white water fish were Liposarcus pardalis, Pygocentrus nattereri, and Pellona flavipinnis, for example, or Plagioscion squamosissimus, Serrasalmus rhombeus, and Serrasalmus manueli in black water. Among the most abundant white water fish, Colossoma macropomum, Mylossoma duriventre and Osteoglossum bicirrhosum occurred almost exclusively in inundated forests. Of the black water species there were a large number of species which were captured only in inundated forest, such as Geophagus cf. altifrons, Hoplias malabaricus, Osteoglossum bicirrhosum and Uaru amphiacanthoides. Catches varied with sample site, water level and direction of water level change. The average CPUE in white and black water was 190 and 41 g fish m-2 and day, respectively, with maximum yields at low water and minimum yields at high water. Comparing rising and falling water levels, a significantly higher quantity of fishes was captured at falling water level. In black water, fish catches from the floodplain forest exceeded the open water catch by 183 to 550%, depending on season. Differences in respect of white water are smaller (106-281%). Fish communities in the area under investigation seem to be stochastically assembled, with significant differences between white and black water only. Many fishes move into the floodplain forest not only to feed but probably also for other reasons to seek shelter, for example