Carlos Edwar de Carvalho Freitas

The influence of flood pulse on fish communities of floodplain canals in the Middle Solimões River, Brazil

The functioning of large river systems with adjacent floodplains is strongly influenced by the flood pulse. This phenomenon is the main structuring force for the biota, including fish communities that use floodplain environments for spawning, feeding, nursery and refuge. In floodplains and in the entire basin, the volume of water controls internal flows. During rising water, the high discharge of the river acts as a natural barrier to the canals that connect floodplain lakes and the Solimoes River, because the water flows from river to lake. During the dry period, there is a reduction of discharge and the water flow is reversed or stationary. These canals are environments with distinct ecological characteristics such as differentiated limnology and water level variation intensely affected by the hydrological cycle. Therefore, we surveyed the influence of the flood pulse on fish communities that inhabit two canals that connect floodplain lakes to the Middle Solimoes River. Particularly, we evaluated the hypothesis that the Solimoes River flow direction is not perfectly parallel to its banks, which creates peripheral flows that direct water from the rivers to the floodplain lake canals. Our analysis indicated that the seasonal pattern is stronger than the spatial. Beside this, we observed that the positions of the canals in relation to the main river flow somehow affect the fish assemblages. Finally, we conclude that the flood pulse is the main structuring force acting on these fish communities. A dinâmica dos sistemas de grandes rios com areas inundadas adjacentes e fortemente influenciada pelo pulso de inundacao, sendo este fenomeno o principal agente estruturador da biota, inclusive dos peixes, que utilizam este ambiente para a desova, alimentacao, bercario e refugio. Nesta regiao e em toda a bacia, a intensidade da vazao controla os fluxos internos. Na epoca da cheia, a forte vazao atua como uma barreira natural nos canais de ligacao entre os lagos de varzea e o rio Solimoes, com um fluxo no sentido rio-lago. Enquanto na seca, com a reducao da intensidade da vazao, o fluxo se inverte. Estes canais sao ambientes com caracteristicas ecologicas especiais, profundamente afetadas pelo ciclo hidrologico. Neste trabalho, estudamos a influencia do pulso de inundacao sobre as comunidades de peixes existentes nos canais entre dois lagos de varzea e o Medio rio Solimoes, avaliando a hipotese de que a direcao do fluxo do rio Solimoes nao e perfeitamente paralelo as margens criando, desta forma, fluxos preferenciais que direcionam o sentido da correnteza para os canais dos lagos de varzea. Nossas analises indicaram que padroes sazonais predominam sobre padroes espaciais. Alem disso, observamos que a posicao do canal em relacao ao fluxo da corrente do rio principal afeta de alguma maneira as assembleias de peixes. Finalmente, concluimos que o pulso de inundacao e a principal forca responsavel pela estruturacao destas comunidades de peixes.

Alimentação de Triportheus angulatus (Spix & Agassiz, 1829) no lago Camaleão, Manaus, AM, Brasil

Periodical flooding cause strong modifications in Central Amazonian floodplain. Periodical rising and decreasing of the water level influences abiotic and biotic factors of the aquatic environments. During the flooding season, there is a high feed availability, in contrast with dry season in which feed availability is at the lowest level. Limnological parameters also change seasonally. Oxygen concentrations vary both daily and seasonally, sometimes even showing hypoxic conditions. Despite these alterations, floodplain lakes are inhabited by several fish species, having the most diverse and abundant fish fauna among the Amazonian environments. This study focused on Triportheus angulatus feeding in temporal distribution in order to understand the influences of hydrological changes on individual size, diet composition and feeding even in low oxygen concentrations. In rising waters season, small individuals are predominant while the decreasing and the dry seasons there are mostly larger ones. There is a seasonal change on diet composition and this is related to feed type that is more available: during the rising, fishes eat mainly insects and zooplankton; in the flood season and drying season, seeds and fruits are predominant, and at the dry season they eat mainly insects. Feed ingestion was higher in the rising waters and mostly in the flood, and it was lower in the drying season. Feeding activity was not related with oxygen concentrations.

An initial assessment of drought sensitivity in Amazonian fish communities

The Amazon River Basin encompasses the world’s largest remaining tropical rainforest, and the largest freshwater system with the highest fish species diversity on earth, but global climate change is predicted to cause the loss of 7–12% of fish species by 2070. The severe drought anomaly of 2005, caused by warming of Atlantic surface waters, provided a unique opportunity to examine the impact of a major climatic disturbance on a tropical fish assemblage. We monitored fish species diversity in six Brazilian floodplain lakes along the Solimões River from 2004 to 2007 (before, during, and after drought). Statistical analysis revealed changes in species composition of these lakes following the drought, with both positive and negative responses observed. The response to drought was not uniform among species with regard to trophic guild or migratory behavior. SIMPER analysis showed that planktivores on the average increased in abundance in the years following the drought, carnivores and omnivores decreased, and herbivores and detritivores increased. Some of these changes were transitory, others persisted through monitoring. Migratory species disproportionately increased in abundance post-drought compared to non-migratory species. Interlake (β) diversity of fish declined during the drought year, indicating that lakes were becoming less heterogeneous in species composition, but showed a trend toward recovery of pre-drought level in the following years. According to both global climate change models and recent experience, the intensity and frequency of droughts in this region of the world is increasing. Given the sensitivity of resident fish species to the single, short-term, perturbation reported here, assessment of how tropical freshwater fish populations respond to drought will be crucial to understanding the consequences of this kind of perturbation to these communities and to the human inhabitants who depend upon this important protein source.

Abundância e distribuição das larvas de peixes no Lago Catalão e no encontro dos rios Solimões e Negro, Amazonas, Brasil

ABSTRACT The abundance and monthly distribution of fish larvae in Catalao Lake, situated near the confluence of the Solimoes and Negro R iver wasevaluated between January and May 2001. The samples were obtained using a conical plankton net (350 µm, O 0.3, 2 m long), with aflow meter attached to the opening of the net. The categorical variables were: position in the lake (margin and center), period of the day (dayand night) and depth (surface and bottom). The analysis was made with Fatorial Correspondence Analyses (FCA) using the larval d ensity(larvae.m -3 ) as answer variable and the months as descriptors. The feeding activity of larvae was also studied. Most of them were protolar vaefeeding in the margin of the lake, on the surface as well as on the bottom. These results indicated that Catalao Lake is an imp ortant nurseryground for to the larvae of fishes that spawn in the Solimoes River. KEY WORDS Solimoes River; Catalao lake; fish-larvae; abundance; distribution; feeding. 1 Instituto Nacional de Pesquisas da Amazonia - INPA

Interconnectedness during high water maintains similarity in fish assemblages of island floodplain lakes in the Amazonian Basin

We conducted a study to test the hypothesis that interconnectedness among island floodplain lakes and the adjacent Solimoes River during the flood stage of the hydrologic cycle is enough to maintain similarity in fish species assemblages. Gill net samples were collected during high and low water periods for three consecutive years (July 2004 to July 2006) in four lakes on Paciencia Island. Two lakes, Piranha and Ressaca, are connected to the river all year, and the other two, Preto and Cacau, which are in the center of the island, are isolated during low water periods. The abundance, species richness and evenness of the fish assemblages in these lakes did not differ according to their relative positions or the season of the hydrological cycle, which confirmed our hypothesis. However, fish abundance during the dry season was greater than in the flood season. Apparently, the short period of full connection between the lakes is enough to allow the colonization of all fish species, but not to cause similar abundances. Our study indicates that persistence of the species composition of island floodplain lakes is primarily due to the annual replenishment of fish to the lakes during the flood season.

Desembarque e esforço de pesca da frota pesqueira comercial de Manicoré (Médio Rio Madeira), Amazonas, Brasil

The adaptation of the strategies of the fisherman to the seasonality in the Amazonian attests the level of traditional ecological knowledge in relation to the fish and to the variations of the fishing in that environment, as it happens in other regions of Brazil. In that sense the present work aimed to analyze the use of the fishing grounds and the distribution of the fishing effort by the commercial fleet in relation to the hydrological cycle. Data of fishing landings and fishing expeditions of the Medium Madeira River region were collected daily, from June of 2003 until May of 2004, and submitted to the descriptive statistics. The results showed that there was a tendency towards an increase in the fishing effort during the rising water season for the vessels of the local fleet, to compensate for the decrease in the captured production. The fishing boats and motorized canoes presented medium values of CPUE 22.9 and 20.6 kg/fisherman*day, respectively. It was also shown that fishermen of motorized canoes utilized the stream and lake environments the most, where as boat fishermen relied mainly on the river environment.

A pesca de pequena escala no rio Madeira pelos desembarques ocorridos em Manicoré (Estado do Amazonas), Brasil

The study aimed to analyze the landing of commercial fishing in Middle Madeira River, near Manicore city, identifying the exploited species, fishing grounds and the contribution for the local supplying of fish. Fish landings were sampled daily, using questionnaires, given to fishermen after the fish sale. In 2002, 225.4 tons of fish were landed in Manicore city. Motorized canoes undertook more fishing trips, but the higher fish landings were accomplished by boats. Mean values of fish landings were 11.2 tons/month, 5.4 tons/month and 2.4 tons/month for boats, motorized canoes and fish purchasers, respectively. 32 species or group of species were landed, with a predominance of jaraqui (Semaprochilodus spp), pacu (Mylossoma duriventre), curimata (Prochilodus nigricans), sardinha (Triportheus spp) e jatuarana (Brycon spp), responsible for 75% of fish production. 32 fishing grounds were identified and the most exploited were the Madeira and Manicore rivers, Acara and Boquerao lakes and the Matupiri stream.

Fish diet from Manacapuru Big Lake complex (Amazon): a approach starting from the traditional knowledge

In the Amazon fishing is one of the main economic activities and higher value to traditional riverine communities of the region. Considering this importance is to suppose that the riverine populations have knowledge about fish fauna explores for them, because their forming culture that maintain a strait relationship with natural resources. This study aim to elevate the traditional knowledge of the fishermen from the riverine communities in the Big Lake Complex about the fish alimentary diet caught for commercialization and consumption. This study was realized in the Manacapuru Big Lake Complex through interview jointed with 62 fishermen. The results presents a detailed knowledge about the tambaqui, tucunare, pacu, acara-acu, curimata, aruana, matrinxa, piranha and pirapitinga fish feeding compatible with the laboratory analyzes and with the specifics literature. Finally the traditional ecological knowledge from the fishermen about the fish ecology in the Big Lake must be used as a subsidy study of lakes management, establishing in this way, an information resource for scientific works at the same time to minimize the cost with a long research.

Intra- and inter-annual changes in the condition factors of three Curimatidae detritivores from Amazonian floodplain lakes

The flood pulse is a key factor that drives the biota of large rivers with adjacent floodplains, but the direction and intensity of its effects are not uniform for all trophic guilds of fish. In this study, we tested the existence of intra- and inter-annual changes in the relative condition factors (kn) of three Curimatidae: Potamorhina altamazonica, Potamorhina latior, and Psectrogaster rutiloides. We used weight and length data from fish that were caught in eight floodplain lakes of the Rio Solimoes. These data were from experimental fisheries during each season of the hydrological cycle: flooding, flood, drying, and dry from 2004, 2005, and 2006. In general, there are similar patterns of intra-annual changes for these three species, with the highest estimates of kn during high water conditions. The lowest values were observed during the drying and dry seasons of 2005, when an extreme drought occurred in the Amazon basin. Higher values were observed during the same seasons in the year post-drought. We hypothesized that these patterns would be explained by the biological characteristics of these species and the effects of intra-annual hydrological changes, mainly the flood pulse effect, and by inter-annual climatic events, which are determined by global climate phenomena.

A composição dos custos de armação e a renda das expedições de pesca da frota pesqueira artesanal da região do Médio rio Madeira, Amazonas, Brasil

Studies emphasizing the physical, operational and economics characteristics of the fishing fleet were realized, focusing the fleet based in Central Amazon but with gaps about the characteristics in peripheral regions. In this sense the work aimed to analyze the necessary costs to entry of new vessel on activity and to provide information in relation to the costs of fishing expeditions and economic revenue of fishing activity. The study was realized in the Medium Madeira River region and collected information about maintenance, cost and income of fishing expeditions, from June 2003 until May 2004, using questionnaires applied to skippers and fishers of boats and motorized canoes. The gear it was most expensive item on acquisition and the fishers the financer. The fishing expeditions of vessels were financed by six agents, fishers and ice plant owner were the principal financers. Fuel was the main items of cost on fishing expeditions of boats, fuel and ice to motorized canoes. The skippers and owners of fishing boats had a clear gain of 0.6 and 0.5 living wages by fishing expeditions and the fishers 0.3 while fishers of motorized canoes had a clear gain of 0.5 living wages.