A meta-analysis on alternative mating tactics: when the main and the alternative yield similar reproductive success.

In many species, individuals of the same sex exhibit different mating behaviours, a phenomenon known as alternative mating tactics (AMTs). These AMTs may occur in species in which morphology prevents individuals from adopting different tactics (fixed expression of AMTs) as well as in species in which individuals can alternate between them (flexible expression of AMTs). Regardless of the way different mating tactics are expressed, a key point to understanding the selective forces driving AMT evolution relies on identifying differences in the reproductive success between tactics. Empirical studies often indicate that individuals adopting the main tactic (generally the more aggressive) have higher mating success than those adopting the secondary tactic. However, while this is expected for species showing flexible expression of AMTs, the same should not hold for species showing fixed expression of AMTs. In species with fixed expression of AMTs, individuals adopting each tactic have morphological specialisations in acquiring mates that may be responsible for eliminating differences in reproductive success between tactics. Despite such expectations, a comprehensive investigation across species regarding differences in the reproductive success of AMTs is lacking. Using a meta-analytical approach, we investigated if there is a difference in the reproductive success between tactics and whether this difference is related to how these tactics are expressed (fixed or flexible). We focused on males since information on reproductive success for females with AMTs is still scarce. We hypothesised that (i) males adopting the main tactic have higher reproductive success than males adopting the secondary tactic, and (ii) the difference in reproductive success between tactics will be higher in species with flexible rather than fixed expression of AMTs. When all species were pooled, we found that males adopting the main tactic had a similar reproductive success to males adopting the secondary mating tactic. However, this trend changed between species with fixed and flexible expression of AMTs. In species with flexible expression of AMTs, males exhibiting the main tactic have higher mating success than those adopting secondary tactics, while in species with fixed expression of AMTs, males adopting distinct tactics have similar reproductive success. Thus, the widespread assumption that males adopting the main tactic have higher reproductive success than males adopting the secondary tactic may be restricted to species in which individuals can alternate between tactics during their lifespan. However, we found that most data on the reproductive success of males adopting AMTs is restricted to short reproductive windows and may not reflect differences in lifetime reproductive success between tactics. Therefore, we highlight the importance of examining the selective pressures associated with fixed and flexible expression of AMTs on lifetime reproductive success to attain a deeper understanding of AMT evolution.

Reproductive biology of harvestmen (Arachnida: Opiliones): a review of a rapidly evolving research field.

Harvestmen are a major arachnid order that has experienced a dramatic increase in biological knowledge in the 21st century. The publication of the book Harvestmen: The Biology of Opiliones in 2007 stimulated the development of many behavioral studies. Although the book is relatively recent, our understanding of the reproductive biology of harvestmen is already outdated due to the fast accumulation of new data. Our goal is to provide an updated review of the subject to serve as a benchmark for the following years. In the pre-copulatory phase, we explore the evolution of facultative parthenogenesis, the factors that may affect the types of mating system, and the role of nuptial gifts in courtship. Regarding the copulatory phase, harvestmen are unique arachnids because they have aflagellate spermatozoa and a penis with complex morphology. We discuss the implications of these two features for sperm competition and cryptic female choice. In the post-copulatory phase, we connect oviposition site selection and climate conditions to the widespread occurrence of resource defense polygyny, alternative reproductive tactics, and sexual dimorphism in several clades of tropical harvestmen. Finally, we present the different forms of parental care in the order, and discuss the benefits and costs of this behavior, which can be performed either by females or males. Throughout the review, we indicate gaps in our knowledge and subjects that deserve further studies. Hopefully, the information synthesized here will stimulate researchers worldwide to embrace harvestmen as a study system and to improve our effort to unravel the mysteries of their reproductive biology.

A cascade of dams affects fish spatial distributions and functional groups of local assemblages in a subtropical river

Dams reduce the longitudinal connectivity of rivers and thereby disrupt fish migration and the spatial distribution of species, impacts that remain poorly studied for some Neotropical rivers from mega-diverse basins. We investigated the spatial distribution of fish species with different trophic and movement/reproductive/size characteristics to assess how functional groups have responded to a cascade of dams on the Uruguai River in southern Brazil. Fish abundance, biomass, and species composition were evaluated at eight locations along the longitudinal gradient. The fish assemblage in the upper stretch was mainly characterized by small and medium-sized species at higher trophic levels, whereas the sites located furthest downstream displayed more medium and large-sized species, including many carnivorous species. Species with high fecundity, seasonal migrants, and catfishes with internal fertilization were common in the river´s middle and lower reaches. Detritivorous species dominated areas distant from the dams. Overall, functional diversity of local fish assemblages was greater in lower reaches. The cascade of dams has impacted the distribution of functional groups of local fish assemblages of Uruguai River. The alteration of functional groups in upper reaches of the river has potential consequences for ecosystem processes and services, such as nutrient cycling and fisheries.(AU)

As barragens reduzem a conectividade longitudinal dos rios e interrompem a migração e a distribuição espacial das espécies, configurando impactos pouco estudados para alguns rios Neotropicais megadiversos. Investigamos a distribuição espacial de espécies de peixes com diferentes características tróficas e reprodutivas para avaliar como grupos funcionais responderam a uma cascata de reservatórios no rio Uruguai, sul do Brasil. Abundância de peixes, biomassa e composição de espécies foram avaliadas em oito locais ao longo do gradiente longitudinal. A assembleia de peixes no trecho superior foi caracterizada principalmente por espécies de pequeno e médio porte em níveis tróficos mais elevados, enquanto que os ambientes localizados mais a jusante apresentaram mais espécies de médio e grande porte, incluindo muitas espécies carnívoras. Espécies com alta fecundidade, migradores sazonais e bagres com fertilização interna foram comuns no curso médio e inferior. Espécies detritívoras dominaram áreas distantes das barragens. A diversidade funcional das assembleias de peixes locais foi maior nas partes inferiores. A cascata de barragens impactou a distribuição dos grupos funcionais das assembleias de peixes locais no rio Uruguai. A alteração da diversidade funcional no curso superior do rio tem consequências potenciais para a dinâmica e serviços do ecossistema, como ciclagem de nutrientes e pesca.(AU)

A cascade of dams affects fish spatial distributions and functional groups of local assemblages in a subtropical river

Dams reduce the longitudinal connectivity of rivers and thereby disrupt fish migration and the spatial distribution of species, impacts that remain poorly studied for some Neotropical rivers from mega-diverse basins. We investigated the spatial distribution of fish species with different trophic and movement/reproductive/size characteristics to assess how functional groups have responded to a cascade of dams on the Uruguai River in southern Brazil. Fish abundance, biomass, and species composition were evaluated at eight locations along the longitudinal gradient. The fish assemblage in the upper stretch was mainly characterized by small and medium-sized species at higher trophic levels, whereas the sites located furthest downstream displayed more medium and large-sized species, including many carnivorous species. Species with high fecundity, seasonal migrants, and catfishes with internal fertilization were common in the river´s middle and lower reaches. Detritivorous species dominated areas distant from the dams. Overall, functional diversity of local fish assemblages was greater in lower reaches. The cascade of dams has impacted the distribution of functional groups of local fish assemblages of Uruguai River. The alteration of functional groups in upper reaches of the river has potential consequences for ecosystem processes and services, such as nutrient cycling and fisheries.(AU)

As barragens reduzem a conectividade longitudinal dos rios e interrompem a migração e a distribuição espacial das espécies, configurando impactos pouco estudados para alguns rios Neotropicais megadiversos. Investigamos a distribuição espacial de espécies de peixes com diferentes características tróficas e reprodutivas para avaliar como grupos funcionais responderam a uma cascata de reservatórios no rio Uruguai, sul do Brasil. Abundância de peixes, biomassa e composição de espécies foram avaliadas em oito locais ao longo do gradiente longitudinal. A assembleia de peixes no trecho superior foi caracterizada principalmente por espécies de pequeno e médio porte em níveis tróficos mais elevados, enquanto que os ambientes localizados mais a jusante apresentaram mais espécies de médio e grande porte, incluindo muitas espécies carnívoras. Espécies com alta fecundidade, migradores sazonais e bagres com fertilização interna foram comuns no curso médio e inferior. Espécies detritívoras dominaram áreas distantes das barragens. A diversidade funcional das assembleias de peixes locais foi maior nas partes inferiores. A cascata de barragens impactou a distribuição dos grupos funcionais das assembleias de peixes locais no rio Uruguai. A alteração da diversidade funcional no curso superior do rio tem consequências potenciais para a dinâmica e serviços do ecossistema, como ciclagem de nutrientes e pesca.(AU)

Reproduction of fishes of the Verde River, upper Paraná River Basin, Brazil / Reproducción de peces del río Verde, cuenca alta del río Paraná, Brasil

Introduction: Understanding the various aspects of the reproductive biology of fish is a key step towards applying effective strategies for sustainable management of fishery resources. Objective: We aimed to evaluate the sex ratio, reproductive period and lengths at first maturity for 30 fish species caught in the Verde River, upper Paraná River Basin, Brazil. Methods: Fish were sampled monthly from November 2010 to March 2011 and from October 2011 to February 2012, and sampled quarterly from May to August in 2011 and 2012; totaling 14 samples. Fish were measured and weighed in the laboratory. In addition, gender and gonadal developmental stage were identified macroscopically. Subsequently, the sex ratio was determined and significant differences were tested using the chi-square (χ²) method. The reproductive period was determined with the use of gonadal developmental stages and the gonadosomatic index. Lastly, length at first maturity was estimated only for the species that presented individuals with sufficient immature and mature gonads to adjust the model. Results: Of the captured individuals, 51.5 % were male, and 48.5 % were female. Fifteen species showed significant differences in their sex ratios. The reproductive period for most species occurred from October to February, with reproductive peaks in November, December and January. The length at first maturity was estimated for only five species, including Salminus brasiliensis, a keystone species. Conclusions: The sex ratios revealed that for many species, there is a predominance of males over females, which was not expected for this parameter. The reproductive period follows the same pattern observed in Neotropical fish. However, it is noteworthy that some species are starting their reproduction in August. Lastly, estimating length at first maturity for most Neotropical fish remains a challenge, which may lead to difficulties in the use of protective measures to maintain fisheries and conserve fish species.

Introducción: Comprender los aspectos de la biología reproductiva de los peces es un paso fundamental para la aplicación de estrategias efectivas para la administración sostenible de los recursos pesqueros. Objetivo: Este estudio tuvo como objetivo evaluar la proporción sexual, el período reproductivo y la longitud en la primera madurez para 30 especies de peces capturados en el río Verde, cuenca alta del río Paraná, Brasil. Métodos: Se tomaron muestras de peces mensualmente de noviembre 2010 a marzo 2011 y de octubre 2011 a febrero 2012, y trimestralmente de mayo hasta agosto de 2011 y 2012; totalizando 14 muestras. En el laboratorio, los peces capturados fueron medidos y pesados. Además, el sexo y la etapa de desarrollo gonadal se identificaron macroscópicamente. Posteriormente, se determinó la proporción sexual y se analizó si había diferencias significativas utilizando el método de chi-cuadrado (χ²). El período reproductivo fue determinado con el uso de las etapas de desarrollo gonadal y el índice gonadosomático. Finalmente, la longitud en la primera madurez fue estimada solamente para las especies que presentaron individuos con suficientes gónadas inmaduras y maduras para ajustar el modelo. Resultados: De los individuos capturados, el 51.5 % fueron machos y el 48.5 % hembras. Quince especies presentaron diferencias significativas en la proporción sexual. El período reproductivo para la mayoría de las especies ocurrió de octubre a febrero, con picos reproductivos en noviembre, diciembre y enero. La longitud en la primera madurez fue estimada solamente para cinco especies, incluyendo Salminus brasiliensis, una especie clave. Conclusiones: La proporción sexual reveló que para muchas especies hay predominio de machos sobre hembras, lo cual no se esperaba para este parámetro. El período reproductivo sigue el mismo patrón observado en peces neotropicales. Sin embargo, vale la pena señalar que algunas especies están comenzando su reproducción en el mes de agosto. Por último, estimar la longitud en la primera madurez para la mayoría de los peces neotropicales sigue siendo un reto, lo que puede llevar a dificultades en el uso de medidas de protección para mantener la pesca y conservar las especies de peces.

Behavior of "Intermediate" Males of the Dimorphic Squid Doryteuthis pleii Supports an Ontogenetic Expression of Alternative Phenotypes.

The expression of alternative reproductive tactics (ARTs) by different-sized males of loliginid squids has been extensively investigated. In loliginids, alternative phenotypes are characterized by discontinuous differences in behavior, body size, sperm deposition site, and morphology and functioning of ejaculates. Large consort males guard females, display agonistic behaviors toward rival consort males, and mate with females in the male-parallel (MP) position. Small sneaker males avoid fighting contests and instead adopt furtive behaviors to access females guarded by consort males, mating with females in the head-to-head (HH) posture. Recently, the reappraisal of preserved material from the loliginid squid Doryteuthis pleii showed that intermediate-sized males (so-called "intermediate" males) had both sneaker- and consort-like ejaculates, leading to the hypothesis of them being a transitional stage between both phenotypes. Here, we describe observations made in captivity showing that intermediate males can display agonistic behaviors toward consort males and mate with females in both mating positions, depending on the male's current reproductive context, i.e., generally in HH, but switching to MP when the female is laying eggs. Such unusual findings of intermediate males simultaneously displaying behaviors of both sneaker and consort males comprise additional evidence corroborating the ontogenetic hypothesis for phenotypic expression of ARTs in this species. Taken together, our results indicate that (1) instead of competing with large consort males for female access and monopolization, small/young males adopt sneaker tactics to obtain mating opportunities, and (2) as they continue to grow, they gradually modify the morphology of their ejaculates and their mating behavior, going through an "intermediate" stage, before becoming large consort males.

Dimorphic ejaculates and sperm release strategies associated with alternative mating behaviors in the squid.

Sperm competition is a powerful postcopulatory selective force influencing male adaptations associated with increasing fertilization success, and it is usually related to the evolution of different strategies of ejaculate expenditure between individuals. Ejaculates may also be influenced by additional selective pressures associated with sperm competition, such as timing between insemination and fertilization, female reproductive tract morphology, and fertilization environment. Also, males that adopt alternative mating tactics may face distinct sperm competition pressures, which may lead to the evolution of intraspecific diversity in ejaculates. In loliginid squids, males with alternative reproductive tactics (sneakers and consorts) differ not only in mating behavior, but also transfer spermatophores into two distinct sites within the female. Here, we compared structure and functioning of spermatophores between sneakers and consorts in the squid Doryteuthis plei applying microscopy techniques and in vitro experiments. Sneakers and consorts exhibit differences in spermatophore structure that lead to distinct spermatophoric reactions and spermatangium morphologies. Moreover, in sneakers, sperm release lasts longer and their sperm show an aggregative behavior not detected in consorts. Slow sperm release may be a strategy to guarantee longer sperm provision, given the wide interval between sneaker mating and egg release. For consorts, in turn, intense and quick sperm discharge may be advantageous, as timing between mating and egg-laying is relatively short. Within the complex squid mating system, factors such as (i) different fertilization sites and (ii) interval between mating and egg release may also influence sperm competition, and ultimately shape the evolution of divergent ejaculates between dimorphic males.

Gonadal development and fecundity of the smooth weakfish Cynoscion leiarchus (Teleostei: Perciformes: Sciaenidae) in a tropical Brazilian bay

Cynoscion leiarchus (Cuvier, 1830) is a coastal fish species that is widely distributed along the Western Atlantic coast, from Belize to Southern Brazil. In Brazil, C. leiarchus It is an important resource for commercial and artisanal fisheries. Our objective was to describe the oogenesis and spermatogenesis stages of the species and to estimate batch size and relative fecundity of a population at a tropical bay in southeastern Brazil. The examined specimens were obtained from artisanal catches that took place from July 2013 to June 2014. A total of 18 individuals (11 females and 7 males) were examined for histological analysis and 20 spawning-capable females were used to estimate fecundity. Five stages of oocyte development (primary growth, pre-vitellogenic, vitellogenic, oocyte maturation and atresia) and four stages of spermatocytes (spermatogonia, spermatocytes, spermatids, spermatozoa) were described in different phases of gonad development (immature, developing, spawning capable and regenerating), suggesting that spawning happens in batches, oocyte development is asynchronic and fecundity is indeterminate. Batch fecundity ranged from 100 × 10(3) to 866 × 10(3) oocytes undergoing final oocyte maturation, and relative fecundity ranged from 232 to 1,225 oocytes, averaging 467 oocytes per gram of ovary-free body weight. Fecundity tended to increase linearly with gonadal weight, total weight, total length, and age, but the highest linear correlation obtained was between fecundity and gonadal weight. This study provides the first information on the gonadal development of C. leiarchus from the Brazilian coast and is a baseline to compare with other populations and/or congeneric species.(AU)

Gonadal development and fecundity of the smooth weakfish Cynoscion leiarchus (Teleostei: Perciformes: Sciaenidae) in a tropical Brazilian bay

Cynoscion leiarchus (Cuvier, 1830) is a coastal fish species that is widely distributed along the Western Atlantic coast, from Belize to Southern Brazil. In Brazil, C. leiarchus It is an important resource for commercial and artisanal fisheries. Our objective was to describe the oogenesis and spermatogenesis stages of the species and to estimate batch size and relative fecundity of a population at a tropical bay in southeastern Brazil. The examined specimens were obtained from artisanal catches that took place from July 2013 to June 2014. A total of 18 individuals (11 females and 7 males) were examined for histological analysis and 20 spawning-capable females were used to estimate fecundity. Five stages of oocyte development (primary growth, pre-vitellogenic, vitellogenic, oocyte maturation and atresia) and four stages of spermatocytes (spermatogonia, spermatocytes, spermatids, spermatozoa) were described in different phases of gonad development (immature, developing, spawning capable and regenerating), suggesting that spawning happens in batches, oocyte development is asynchronic and fecundity is indeterminate. Batch fecundity ranged from 100 × 10(3) to 866 × 10(3) oocytes undergoing final oocyte maturation, and relative fecundity ranged from 232 to 1,225 oocytes, averaging 467 oocytes per gram of ovary-free body weight. Fecundity tended to increase linearly with gonadal weight, total weight, total length, and age, but the highest linear correlation obtained was between fecundity and gonadal weight. This study provides the first information on the gonadal development of C. leiarchus from the Brazilian coast and is a baseline to compare with other populations and/or congeneric species.

O tamanho de primeira maturação como parâmetro para estabelecimento de tamanho mínimo de captura para corvina no sudeste do Brasil / Size at first maturation as parameter for establishment of the minimum size of capture for the white croaker in Southeastern Brazil

Micropogonias furnieri is one of the most important fishery resources in Southeastern Brazil. However, the Brazilian law for exploitation of this resource is incipient. Our main aim was to assess whether reproductive tactics developed by Ubatuba populations are consistent with the available information and to evaluate their suitability to support measures of protection. A total of 359 individuals were examined, with unbalanced sex ration (1 female:1.56 male). Negative alometry (b 3) was found for both sexes. Spawning occurs during most of the year. Size at first maturation (L50 = 341 mm; 329 mm TL; for females and males, respectively), was higher than previous information for the region, and higher than the minimum size of allowed capture established by the law (TL = 25 cm). We recommend consider this new size at first maturity as the minimum allowed capture size as a measure to help protect this fishery resource in Southeastern Brazil.

A corvina Micropogonias furnieri é um dos recursos pesqueiros mais importantes das pescarias artesanais costeiras do Sudeste do Brasil. Entretanto, a legislação pesqueira é incipiente no que diz respeito à regulamentação da pesca desta espécie. Objetivou-se investigar se as táticas reprodutivas da população de corvinas de Ubatuba-SP são consistentes com as informações disponíveis na literatura e adequadas para suportar medidas de proteção da espécie. Foram examinados 359 indivíduos, com proporção sexual desbalanceada (1 fêmea:1,56 macho). Ambos os sexos apresentaram alometria negativa (b 3). Observou-se longo período reprodutivo. Os comprimentos de primeira maturação gonadal (C50 = 341 mm; 329 mm para fêmeas e machos, respectivamente), foram superiores aos reportados para a região Sudeste e ao tamanho mínimo de captura estabelecido por lei (Ct = 250 mm). Recomenda-se revisar a legislação considerando os valores de C50 do presente estudo como medida de proteção a este recurso na região Sudeste do Brasil.

O tamanho de primeira maturação como parâmetro para estabelecimento de tamanho mínimo de captura para corvina no sudeste do Brasil / Size at first maturation as parameter for establishment of the minimum size of capture for the white croaker in Southeastern Brazil

Micropogonias furnieri is one of the most important fishery resources in Southeastern Brazil. However, the Brazilian law for exploitation of this resource is incipient. Our main aim was to assess whether reproductive tactics developed by Ubatuba populations are consistent with the available information and to evaluate their suitability to support measures of protection. A total of 359 individuals were examined, with unbalanced sex ration (1 female:1.56 male). Negative alometry (b 3) was found for both sexes. Spawning occurs during most of the year. Size at first maturation (L50 = 341 mm; 329 mm TL; for females and males, respectively), was higher than previous information for the region, and higher than the minimum size of allowed capture established by the law (TL = 25 cm). We recommend consider this new size at first maturity as the minimum allowed capture size as a measure to help protect this fishery resource in Southeastern Brazil.(AU)

A corvina Micropogonias furnieri é um dos recursos pesqueiros mais importantes das pescarias artesanais costeiras do Sudeste do Brasil. Entretanto, a legislação pesqueira é incipiente no que diz respeito à regulamentação da pesca desta espécie. Objetivou-se investigar se as táticas reprodutivas da população de corvinas de Ubatuba-SP são consistentes com as informações disponíveis na literatura e adequadas para suportar medidas de proteção da espécie. Foram examinados 359 indivíduos, com proporção sexual desbalanceada (1 fêmea:1,56 macho). Ambos os sexos apresentaram alometria negativa (b 3). Observou-se longo período reprodutivo. Os comprimentos de primeira maturação gonadal (C50 = 341 mm; 329 mm para fêmeas e machos, respectivamente), foram superiores aos reportados para a região Sudeste e ao tamanho mínimo de captura estabelecido por lei (Ct = 250 mm). Recomenda-se revisar a legislação considerando os valores de C50 do presente estudo como medida de proteção a este recurso na região Sudeste do Brasil.(AU)

Dominance, access to females, and mating success among coresident male mantled howlers (Alouatta palliata) at La Pacifica, Costa Rica.

The priority-of-access (POA) model posits that high dominance rank increases male mating success by increasing access to fertile females. However, the relationship between rank, access to females, and subsequent mating success is variable in primates, and there are few studies representing Neotropical taxa. The purpose here was to test the parameters of the POA model in an asynchronously breeding Neotropical primate, Alouatta palliata, to contribute to our understanding of the relationship between dominance and reproductive strategies in platyrrhines. I collected data on adult males within two large, multimale-multifemale groups exhibiting clear dominance hierarchies at La Pacifica, Costa Rica. Females were classified as sexually receptive (SR) or potentially cycling (PC) based on behavioral and birth data. Access to mates was measured based on total time in proximity to SR/PC females, and mating success was measured based on copulation frequency. Results did not support the predictions of the POA model in that first-ranked males maintained lower than expected time in proximity to SR females, did not consistently maintain the greatest proportion of time in proximity to PC females, obtained lower than expected copulation rates, and did not obtain the highest copulation rates compared to subordinates in either group. Deviations from the POA model were significantly affected by varying operational sex ratios only when considering the lower numbers of available SR females in one group. Alternative reproductive tactics by subordinate males such as tolerance by first-ranked males appeared to be operating, allowing subordinates to obtain mating success when they would otherwise be unable to do so. The study also highlighted how factors such as operational sex ratio may limit the willingness or ability of dominant males to monopolize access to females, and can vary both within and between groups in a population.

Efeito das modificações ambientais naturais e antropicas na reprodução de peixes amazônicos / Effect of natural and anthropogenic changes in Amazonian fish reproduction

Alterações de táticas reprodutivas em peixes podem ser provocadas por vários fatores como as mudanças ambientais naturais ou aquelas provocadas pela construção de grandes empreendimentos como o caso de hidrelétricas. Para verificar como as condições ambientais impostas influenciam na reprodução dos peixes, parâmetros reprodutivos populacionais como tamanho médio de primeira maturação sexual (L50), menor fêmea madura capturada, tamanho máximo da fêmea (L∞), tamanho relativo da primeira maturação (L50/L∞) e intensidade reprodutiva (IR), foram determinados para assembleias de peixes de uma área não impactada de várzea e da UHE Balbina. Os resultados mostraram um padrão sazonal de reprodução durante a enchente, indicando a importância da sequência seca/enchente/cheia para o sucesso reprodutivo das espécies em ambientes de várzea e da precipitação para as espécies em reservatório. Ainda, foi observado mudança na intensidade reprodutiva da assembleia nas duas situações e nas táticas reprodutivas das espécies do reservatório. Eventos climáticos drásticos podem influenciar a atividade reprodutiva, o recrutamento e consequentemente a manutenção dos estoques pesqueiros, assim como a interrupção do curso natural de um rio pode provocar mudanças nas táticas reprodutivas de espécies como mecanismo adaptativo ao novo ambiente.(AU)

Changes in reproductive tactics in fishes can be caused by several factors such as natural climate changes or those caused by the construction of large projects as it is the case of hydroelectric plants. In order to evaluate environmental conditions on fish reproduction, a few reproductive parameters such as size at first maturation (L50), smallest ripe female captured, maximum female size (L∞), relative size at first maturation (L50/L∞) and reproductive intensity (IR) were determined for fish assemblages in a non impacted floodplain area and in a neotropical reservoir, Balbina hydroelectric plant. The results showed a seasonal pattern of fish reproduction during the rising of the water and indicate the importance of the flood pulse to the reproductive success of species in the floodplain as well as precipitation for the species in the reservoir. Still, changes in the reproductive intensity in both sites and in the reproductive parameters of the reservoir fishes could be observed. Drastic climate events may influence the reproductive activity, recruitment, and consequently the maintenance of fish stocks, as well as the interruption of the natural course of a river can cause changes in the reproduction of species as an adaptive mechanism to the new environment formed.(AU)

Efeito das modificações ambientais naturais e antropicas na reprodução de peixes amazônicos / Effect of natural and anthropogenic changes in Amazonian fish reproduction

Alterações de táticas reprodutivas em peixes podem ser provocadas por vários fatores como as mudanças ambientais naturais ou aquelas provocadas pela construção de grandes empreendimentos como o caso de hidrelétricas. Para verificar como as condições ambientais impostas influenciam na reprodução dos peixes, parâmetros reprodutivos populacionais como tamanho médio de primeira maturação sexual (L50), menor fêmea madura capturada, tamanho máximo da fêmea (L∞), tamanho relativo da primeira maturação (L50/L∞) e intensidade reprodutiva (IR), foram determinados para assembleias de peixes de uma área não impactada de várzea e da UHE Balbina. Os resultados mostraram um padrão sazonal de reprodução durante a enchente, indicando a importância da sequência seca/enchente/cheia para o sucesso reprodutivo das espécies em ambientes de várzea e da precipitação para as espécies em reservatório. Ainda, foi observado mudança na intensidade reprodutiva da assembleia nas duas situações e nas táticas reprodutivas das espécies do reservatório. Eventos climáticos drásticos podem influenciar a atividade reprodutiva, o recrutamento e consequentemente a manutenção dos estoques pesqueiros, assim como a interrupção do curso natural de um rio pode provocar mudanças nas táticas reprodutivas de espécies como mecanismo adaptativo ao novo ambiente.

Changes in reproductive tactics in fishes can be caused by several factors such as natural climate changes or those caused by the construction of large projects as it is the case of hydroelectric plants. In order to evaluate environmental conditions on fish reproduction, a few reproductive parameters such as size at first maturation (L50), smallest ripe female captured, maximum female size (L∞), relative size at first maturation (L50/L∞) and reproductive intensity (IR) were determined for fish assemblages in a non impacted floodplain area and in a neotropical reservoir, Balbina hydroelectric plant. The results showed a seasonal pattern of fish reproduction during the rising of the water and indicate the importance of the flood pulse to the reproductive success of species in the floodplain as well as precipitation for the species in the reservoir. Still, changes in the reproductive intensity in both sites and in the reproductive parameters of the reservoir fishes could be observed. Drastic climate events may influence the reproductive activity, recruitment, and consequently the maintenance of fish stocks, as well as the interruption of the natural course of a river can cause changes in the reproduction of species as an adaptive mechanism to the new environment formed.