Leporinus frederici (Bloch, ) Leporinus friderici friderici (Bloch, ) Salmo friderici Bloch, BioLib link: Leporinus friderici · FishBase. Dorsal soft rays (total): 12; Anal soft rays: Scales in lateral line 35 + circumpeduncular 16; profile over orbits flat; teeth in the upper jaw 4 + 4, the cutting. Leporinus friderici (Bloch, ) (Characiformes, Anostomidae) is a freshwater fish commonly called “piava” or “piau-três-pintas” widely.
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The reproductive strategy of a species depends upon the interaction between intrinsic and extrinsic factors. Size-associated sexual dimorphism was observed, that is females dominated the longer length categories, and males the shorter. The minimum size at which L. In Itaipu, stabilization between the maximum and minimum lengths at first maturation was also noted after year 6 following closure leporinjs continuing until year In general, the breeding season lasted from October through April, although cyclic changes in the duration and intensity of this season were evident.
The formation of Itaipu Reservoir had a greater effect on the reproduction of L. It was concluded that reproductive strategies constitute ecological adaptations that are temporally and spatially altered and are fitted to resource availability and environmental pressure. In aquatic environments, the expression of the reproductive strategy of a species depends on the interaction between intrinsic factors, such as the metabolism of the organisms themselves, and extrinsic factors resulting from existing environmental conditions, such as the quality of reproductive habitats and interspecific relationships, as well as physical factors and flood regimes Nikolsky, ; Lowe-McConnel, ; Wootton, Artificial environmental conditions caused by reservoir construction have led to habitat changes, with consequences for the composition and structure of fish populations Agostinho et al.
The reproductive success of a species is a limiting condition for its maintenance and exploitation in the new environment. In this process, the balance between the advantages and disadvantages in the allocation of energy for reproductive strategy and its variations tactics is the factor determining the characteristics of the life history of an organism, such as age or size at sexual maturation, survival rate, fecundity, and reproductive frequency.
Knowledge of reproductive strategies is frdierici to implementation of management measures and preservation of the populations of native fishes, as well as contributing to knowledge of the species’ ecology. Nevertheless, the changes in populations subjected to the unpredictable conditions of the first years of reservoir formation have rarely been documented.
Information from such studies may also be useful in evaluating the evolutionary pattern and the ecological relationships which make it possible for a species to survive in these environments. It tested whether the environment formed by damming the river promoted different local reproductive modes, and whether temporal changes in reproductive strategy are patterns for the species, or are dependent on the impacted environment.
Itaipu Reservoir was closed in October and eventually attained an area of 1, Km 2 at its maximum level, with mean depth The residence time of the water is 40 days Benedito-Cecilio, Collections were made monthly in both the pre-closure April-August and the post-closure September August phases.
In Itaipu Reservoir, 21 sampling points were established, also grouped into subsystems: Collections were made monthly from November through Octoberand trimonthly from March through Frideruci Leporinus friderici was not recorded in Itaipu before the reservoir was closed. Fishing gear consisted of stationary nets with mesh sizes 3 to 14 cm, and trammel nets with mesh 6 to 9 cm between nonadjacent knots, set out for 24 hours at each sampling station. Standard length Lstotal weight Wtand gonadal weight Wg were measured for each specimen caught.
Fridegici were sexed and the state of gonadal maturation was estimated by macroscopic inspection of the gonads Vazzoler, Data analysis The sex ratio per standard length class, environment, and season was established. Significant differences from 1: Lepofinus datum was calculated for each year of the study. The highest values of this ratio were used as indicators of the breeding season. Lepoinus sites were identified as those with the largest concentration of individuals with mature and emptied gonads and the highest mean GSR values.
The relationships between breeding sites and seasons and fridsrici condition factor were evaluated by ANOVA. Young specimens were considered as those with immature gonads, and adults those with gonads in later stages of maturation.
No common pattern was observed in the predominance of one sex between the environments of either reservoir. Year to year, females were always more abundant in Itaipu, and dominated significantly during most of the study period. Both populations showed differences in the sex ratios in the leoprinus and longer length classes, females being longer than males Fig.
Leporinus friderici – Threespot Leporinus (Salmo friderici) — Seriously Fish
fgiderici The size at which L. In both cases Lpm was greater during the first years after flooding, and then decreased. In Itaipu, following a gradual reduction in size, an increase and stabilization in mean length at first gonadal maturation were observed in the last three years studied years 6, 7, and In both environments, the reproductive investment of the females was much higher than that of the males Figs.
The breeding season extended from September through April, although annual variation was seen in both reservoirs. The relationship between the duration of the breeding season and the reproductive intensity values of mean GSR was also notable: The breeding sites selected by the populations of L.
The relationship between breeding sites and season and the well-being of leporijus species, interpreted as the values of the condition factor Kwas different in the two reservoirs Figs.
This showed that there was no pattern in utilization of stored energy by L. Although adult individuals were abundant in Itaipu, the largest catches of young fish were recorded leporiuns year 3, 7, and 15 following reservoir formation Figs. Deviations from a 1: In many cases food supply is a determining factor, and females predominate when food is abundant, while males predominate in oligotrophic environments Nikolsky, Food would influence the metabolism through hormonal activity, causing friferici in the production of individuals of one sex.
Current velocity did not appear to affect aggregation of the sexes, since no significant pattern of predominance of either sex was friderlci in relation to type of environment lentic or lotic.
Size-associated sexual dimorphism was observed in L. This characteristic has lrporinus been noted for several other teleost species Narahara et al. It is fruderici that more or less preferential criderici of specimens of one sex would reflect different growth rates Munro,which may also be a consideration in the case of L. The minimum size at first reproduction varied annually, and ftiderici larger in the periods immediately after formation of both reservoirs. Although there are no studies on the relationship of fecundity and standard length in L.
Thus the post-closure period may possibly be marked by greater fecundity of the species. On the other hand, the costs of fecundity influence directly or indirectly the availability of energy for future reproduction.
The direct costs of fecundity would over the long term reduce the availability of stored energy used for reproduction, while the indirect costs would reduce growth rate, indirectly influencing future reproduction Schwarzkopf, Decreases in mean length at first maturation of L.
In Itaipu the maximum and minimum mean lengths at first maturation stabilized following year 6 after closure, and continued through year The breeding season established for L.
Nevertheless, cyclic changes in the duration and intensity of the breeding season were observed in Itaipu.
Leporinus friderici, Threespot leporinus : fisheries, aquaculture
Longer or shorter spawning seasons must favor the permanence of a species in reservoirs, since the virtual leorinus losses of a shorter season are compensated by success in the survival of the young in the same or the subsequent season. The continuity of stimuli for initiation and intensity of spawning are, therefore, a consequence of the annual variability of stored and environmental resources available to the individuals.
Biotic as well as abiotic factors are uncouplers of the reproductive process in the environments considered. However we can suppose that the evident cyclical changes in environmental conditions, such as temperature and rainfall, are related to the physiological rhythm of L.
Relationships between the breeding season and sudden rise in river level, changes in current flow, water pressure, and occasionally chemical factors have been observed for L. The habitats selected for spawning by L.
The requirements for spawning necessarily limit the spawning lepornus of fish Santos et al. It is admitted that, of the reproductive tactics analyzed for L.
The resources physiologically stored by L. This condition has been commonly observed for other fish species Santos et frideridi. Nevertheless, the same pattern could not be demonstrated in Itaipu, that is the variations in the physical condition of the species could not be attributed to changes in the breeding season, but coincided only with the spawning sites, possibly reflecting the availability of food in the environment.
The population of L. This might be explained by three suppositions: In those catches there was no evidence of predominance of young fish, which does not support the first supposition. The frriderici suggestion cannot be totally discarded, since fish species have specific tactics for spawning and development of the young and information about these behaviors is sparse, not only for L.
However, the dominance of young fish was observed during the entire period of the rriderici including the river phase, and was not shown to be an effect of reservoir formation.
According to Oduma high proportion of young individuals provides evidence that a population is growing rapidly. This condition may reflect high recruitment in the region flooded by the Itumbiara Reservoir, just friderick the area studied. In spite of the fact that the present fish community there is dominated by species of lentic environments, lotic species such as the dourado, piapara, and piau are still caught by the commercial fishery of Itumbiara Godinho, In Itaipu, the higher incidence leproinus young fish in year 2 the period immediately after closure of the reservoir may reflect the availability of lepoirnus in that unstable colonization period, beside other determining factors such as predation and greater habitat availability.
The highest densities of young fish observed in year 7 appeared to have maintained themselves after 15 years following damming, and were similar to those observed for years 3 and 7.
However, this fact is inconclusive since the abiotic and biotic conditions responsible for the recruitment process were not investigated, and could as well rfiderici from a cyclic environmental process.
In sum, it can be admitted that reproductive strategies are more ecological adaptations than genetic phenomena. These strategies undergo temporal and spatial changes, and are conditioned by resource availability and environmental pressure. The characteristics required for the spawning sites, nevertheless, are among the more limiting and specific reproductive tactics of L.
Reid for the translate the text into English.
Um estudo de caso: Rio Grande do Norte. Cambridge University Press, p.
Academic Press, London, p. Editora Guanabara, Rio de Janeiro, p. Strategies and Tactics, Academic Press, London, p. Services on Demand Journal. All the contents of this journal, except where otherwise noted, is licensed under triderici Creative Commons Attribution License. How to cite this article.