Resumo: O estudo descreve a composição e estrutura da comunidade de larvas e juvenis de peixes associada a bancos de macrófitas aquáticas e avalia a importância dessas vegetações para o desenvolvimento dos estágios iniciais de vida da ictiofauna em uma ilha aluvial no Baixo Amazonas, Pará, Brasil. As amostragens foram realizadas durante os momentos de cheia/vazante de 2017 (ciclo I) e enchente de 2018 (ciclo II) em bancos de macrófitas por meio de um peneirão (malha 500 µm). Em laboratório os indivíduos foram identificados e classificados quanto ao seu estágio de desenvolvimento e verificada a abundância, a composição das espécies e similaridade entre os ciclos de amostragens. Uma análise de variância e teste t foram utilizados para constatar diferenças das densidades entre os estágios de desenvolvimento e ciclos hidrológicos, respectivamente. Foram capturados 2.193 indivíduos, dos quais 87,91 % ainda em fase larval e 12,08 % juvenil, classificados em 84 táxons e distribuídos em nove ordens, 24 famílias, 50 gêneros e 72 espécies. Durante o ciclo I, houve maior predominância de indivíduos juvenis de espécies de pequeno porte, que possuem importante função na transferência de energia no ecossistema aquático, enquanto no ciclo II os maiores valores de abundância foram registrados para as espécies de interesse econômico e de médio porte capturadas em estágios iniciais de desenvolvimento. Não foi observada diferença significativa na densidade de indivíduos entre os ciclos de amostragem, porém através da análise de similaridade foi registrada uma variação na composição de espécies entre os ciclos. A maior riqueza de espécies, dominância e densidade de indivíduos foram registradas durante a enchente. A cheia/vazante apresentou maiores valores de equitabilidade e diversidade de espécies. Assim, a comunidade de larvas e juvenis de peixes em vegetação aquática em várzea do Baixo Amazonas demonstra ser influenciada pelo ciclo hidrológico, garantindo a manutenção e renovação da ictiofauna. Palavras-chave: Diversidade; ictiofauna; vegetação flutuante; inundação; Amazônia Oriental. AQUATIC MACROPHYTE STANDS AS EARLY STAGES OF FISH DEVELOPMENT SITES IN THE FLOODPLAIN OF THE LOWER AMAZON: The study describes the composition and structure of the larval and juvenile fishes' community associated with aquatic macrophyte stands and it evaluates the importance of this vegetation for the development of early life stages of the ichthyofauna in an alluvial island in the Lower Amazon River, state of Pará, Brazil. The sampling was conducted during the phases of full flood/receding water of 2017 (cycle I) and rising water of 2018 (cycle II) in aquatic macrophyte stands using a fishing sieve (500 µm mesh). In the laboratory, specimens were identified and classified for their development stage and verified the species composition, abundance and similarity between the sampling cycles. Variance analysis Oliveira et al. | 645
Many Amazonian fi sh' reproduction is associated to seasonality and to the conditions of habitat integrity. In a Neotropical fl oodplain lake of the Amazon region, the temporal structure of ichthyoplankton was investigated and the hypothesis that the density of fi sh eggs and larvae and the diversity of species vary between two areas with different levels of environmental changes occurred was tested. The sampling occurred monthly between September 2017 and August 2018. Six sampling stations were used, distributed in locations close to and far from the altered area. 195 eggs and 1,785 larvae from nine orders and 27 species were captured. The eggs were from nonmigratory fi sh species and occurred during two moments. The larvae presented different abundance peaks during the sample months and all the initial stages of development occurred. Clupeiformes was the most abundant and Characiformes the species richest.The density of the ichthyoplankton and the diversity of species presented temporal variation. However, only the larval density varied between the areas of the lake. The Lake Juá is a spawning area for resident fi sh and is a nursery and growth area for larvae of species with different ecological categories and socioeconomic importance during different periods of the year.
Maicá lake is located in várzea area, in the floodplain of the low stretch of the Amazon River, being considered a fishy environment that guarantees food and income for several communities and surrounding residents. The objective of the study was to know and expand information about the occurrence and temporal distribution of Clupeiformes larvae in Maicá lake, Santarém, Pará, located five km from the city of Santarém, in the Lower Amazon region. 12 monthly collections were carried out during 2015, with sampling cycles during the day and night, distributed in nine georeferenced stations. The biological material was collected by means of horizontal dragging on the subsurface of the water column, with the aid of a 300 μm conical plankton net. To check for possible differences in larval density between the sampling months, analysis of variance (ANOVA One-Way) was used. A total of 2,191 individuals belonging to the order Clupeiformes were captured, distributed in three families, four genera and seven species. The larvae density varied and differed between the months of the year, with the highest value recorded in the month of October, indicating the end of the low season the period of greatest reproductive activity of this group of fish in the region, that is, under conditions of high temperatures and low levels of dissolved oxygen in the water. The information demonstrates the relevance of Maicá lake as a nursery and development area for larvae of Clupeiformes, highlighting the importance of maintaining the integrity of this aquatic ecosystem and proposing conservation actions to maintain the populations of these species that currently occupy this source.
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