Elineide Eugênio Marques

Fish ladder of Lajeado Dam: migrations on one-way routes?

Fish ladders are generally conceived to reestablish connectivity among critical habitats for migratory species, thus mitigating the impacts of the blockage of migration routes by dams. If this management tool is to be meaningful for conserving fish species, it must provide a fully permeable connection and assure both upward and downward movements. However, because reservoirs have very different hydrodynamics than the original river, it is expected that, at least in the inner area, they may constitute an additional barrier to this movement, especially for descending fish. Thus, the present study sought to determine if migratory fish and their offspring disperse downstream from the dam after ascending a ladder and spawning in the upper reaches of a basin. To achieve this purpose, we evaluated the limitation imposed by lentic areas to the descent of eggs, larvae and adults of migratory species; we also determined the abundance and composition of larvae present in the plankton near the dam, and compared the intensity of the upward and downward movements of adult fish. Samples of ichthyoplankton were taken upriver, inside the reservoir, in the river downstream from the dam, and in the forebay of the Lajeado Dam on the Tocantins River (Luis Eduardo Magalhaes Hydroelectric Plant), from October, 1999 through September, 2004. The densities of fish ascending and descending the ladder were determined experimentally on eight occasions, from June, 2004 to March, 2005. Due to difficulties in identifying the true fish origin (up or down) in the environments connected by the fish passage system, the evaluation of the distribution of migratory fish in reservoirs was based on the landings of the commercial fishery conducted along the Itaipu Reservoir during the four years preceding (2001 through 2003) the construction of the lateral channel (fish-passage mechanism). Fish eggs and larvae drifting down the Tocantins River did not appear in samples taken in the lower half of the reservoir; those found in water flowing through the spillways, turbines or fish ladder of Lajeado Dam belonged essentially to non-migratory clupeids that spawn in the inner part of the reservoir. In addition, results showed that in a reservoir with no fish-passage mechanism, migrants select habitats that still maintain riverine characteristics, in the upper parts of the impounded area. The downward movements are negligible compared to those upward, in the experiments conducted in the fish ladder. It is concluded, therefore, that the Lajeado fish ladder, and possibly those at other dams, is essentially a one-way route that promotes upstream movements of migrants, without the necessary return of adults or their offspring. Thus, the low permeability of the connections provided by these management tools can drastically increase the level of environmental impact that they were actually intended to reduce.

Selectivity of fish ladders: a bottleneck in Neotropical fish movement

*Nucleo de Estudos Ambientais (Neamb), Universidade Federal do Tocantins, Campus de Porto Nacional, Rua 3, Quadra 17, Jardim do sIpes, 77500-000 Porto Nacional, TO, Brazil. agostinhocs@uft.edu.br**Nupelia, Universidade Estadual de Maringa, Av. Colombo, 5790, 87020-900 Maringa, PR, Brazil. agostinhoaa@nupelia.uem.br***Pos-Graduacao Ciencias do Ambiente, Universidade Federal do Tocantins. Av. NS 15, ALCNO 14, Bloco 3, Sala 15, 77010.970 Palm as,TO, Brazil.

Fish ladders: safe fish passage or hotspot for predation?

Fish ladders are a strategy for conserving biodiversity, as they can provide connectivity between fragmented habitats and reduce predation on shoals that accumulate immediately below dams. Although the impact of predation downstream of reservoirs has been investigated, especially in juvenile salmonids during their downstream movements, nothing is known about predation on Neotropical fish in the attraction and containment areas commonly found in translocation facilities. This study analysed predation in a fish passage system at the Lajeado Dam on the Tocantins River in Brazil. The abundance, distribution, and the permanence (time spent) of large predatory fish along the ladder, the injuries imposed by piranhas during passage and the presence of other vertebrate predators were investigated. From December 2002 to October 2003, sampling was conducted in four regions (downstream, along the ladder, in the forebay, and upstream of the reservoir) using gillnets, cast nets and counts or visual observations. The captured fish were tagged with thread and beads, and any mutilations were registered. Fish, birds and dolphins were the main predator groups observed, with a predominance of the first two groups. The entrance to the ladder, in the downstream region, was the area with the highest number of large predators and was the only region with relevant non-fish vertebrates. The main predatory fish species were Rhaphiodon vulpinus, Hydrolycus armatus, and Serrasalmus rhombeus. Tagged individuals were detected predating along the ladder for up to 90 days. Mutilations caused by Serrasalmus attacks were noted in 36% of species and 4% of individuals at the top of the ladder. Our results suggested that the high density of fish in the restricted ladder environment, which is associated with injuries suffered along the ladder course and the presence of multiple predator groups with different predation strategies, transformed the fish corridor into a hotspot for predation.

Orpotrin: A novel vasoconstrictor peptide from the venom of the Brazilian Stingray Potamotrygon gr. orbignyi

Characterization of the peptide content of venoms has a number of potential benefits for basic research, clinical diagnosis, development of new therapeutic agents, and production of antiserum. In order to analyze in detail the peptides and small proteins of crude samples, techniques such as chromatography and mass spectrometry have been employed. The present study describes the isolation, biochemical characterization, and sequence determination of a novel peptide, named Orpotrin from the venom of Potamotrygon gr. orbignyi. The natural peptide was shown to be effective in microcirculatory environment causing a strong vasoconstriction. The peptide was fully sequenced by de novo amino acid sequencing with mass spectrometry and identified as the novel peptide. Its amino acid sequence, HGGYKPTDK, aligns only with creatine kinase residues 97-105, but has no similarity to any bioactive peptide. Therefore, possible production of this peptide from creatine kinase by limited proteolysis is discussed. Taken together, the results indicate the usefulness of this single-step approach for low molecular mass compounds in complex samples such as venoms.

Movements through a fish ladder: temporal patterns and motivations to move upstream

Fish passages are constructed with the aim of reestablishing connectivity between critical habitats, in order to sustain thosespecies that move over a large area during their lives. The upstream movements of most of the known migratory species aremade for purposes of reproduction (adults) or dispersal (juveniles). The present study was conducted at the ladder con-structed at Lajeado Dam (Luis Eduardo Magalhaes Hydroelectric Power), on the Tocantins River. The objective was to assesswhether there is a temporal pattern in the abundance of fish below the dam and in the ladder, that correlates with their breedi ngseasons. Additionally, it was examined whether reproduction is the predominant motivation of the shoals of fish that ascendthe ladder. Samples were taken monthly from November, 2002 through October, 2003, downriver from the dam with gillnets, andin the resting pools of the fish ladder with cast nets. The analysis of seasonality in the aggregation of the shoals was based onthe temporal variations in abundance and species richness. The possibility of a reproductive motivation for ascending theladder was inferred from the frequency of the stages of gonadal development. However, during the entire study period weobserved a high frequency of individuals with gonads in the pre-vitellogenic stage for all analyzed species, both downriverfrom the dam (97%) and in the fish ladder (98%). These findings suggest that there was no reproductive motivation for theaggregation of the fish downstream and for their entry into the ladder. On the other hand, the dominance of these stagesdownriver suggests that the spawning habitats are distant, and that the upstream movements occur for other reasons such asdispersal and search for more appropriate habitats for feeding and growth. The entrance into the ladder resulted more fromrheophilic behavior, which is more pronounced in migratory species, than from an endogenous motivation linked to reproduc-tive migration.Os mecanismos de transposicao de peixes em barragens visam restabelecer a conectividade entre habitats criticos a manutencaopara as especies que tenham uma ampla area de vida. Os movimentos ascendentes da maioria das especies migradorasconhecidas sao realizados por motivacao reprodutiva (adultos) ou dispersiva (juvenis). Neste contexto, o presente estudo temcomo objetivo avaliar se existe um padrao temporal na abundância de peixes a jusante da barragem e na escada da UHE Lajeado(UHE Luis Eduardo Magalhaes, rio Tocantins) que segue a sazonalidade reprodutiva. Adicionalmente, busca avaliar sereproducao e a motivacao predominante dos cardumes que ascendem a escada. Para isto, as amostragens foram realizadasmensalmente de novembro de 2002 a outubro de 2003 a jusante da barragem, com o uso de redes de espera, e nos tanques dedescanso da escada, com tarrafas. A analise da sazonalidade na agregacao dos cardumes foi baseada nas variacoes temporaisde abundância e riqueza de especies, enquanto a motivacao reprodutiva para a ascensao foi inferida a partir da frequencia dosestadios de maturacao gonadal. Entretanto, durante todo o periodo foi constatada uma elevada frequencia de individuos comgonadas em fase pre-vitelogenica em todas as especies analisadas, tanto a jusante da barragem (97%) como na escada (98%),sugerindo a inexistencia de motivacao reprodutiva para a agregacao dos peixes a jusante e seus ingressos na escada. Por outrolado, o fato destes estadios dominarem as capturas tambem a jusante sugere que os locais de desova estao distantes, e que osdeslocamentos ascendentes ocorrem por outras razoes, como dispersao natural e busca de habitats mais apropriados paraalimentacao e crescimento. Assim, o ingresso na escada decorreu mais do comportamento reofilico, exacerbado nas especiesmigradoras, que de uma motivacao endogena ligada a migracao reprodutiva.

All that goes up must come down? Absence of downstream passage through a fish ladder in a large Amazonian river

Millions of fish ascend through fishways in South America every year, but there is no evidence that downstream passage is occurring in large dams. Based on this concern, this study monitored the fish ladder at Lajeado Dam, Tocantins River, a large Amazonian tributary. To investigate the extent of downstream movements through the fishway, ascending and descending movements were quantified between November 2007 and October 2008. Monitoring showed that the ladder is restrictive to many species in both directions, but downstream passage was much more limited: almost all fish captured in the ladder (99.5%) were ascending the facility. Consequently, the numerical ratio between ascending and descending fish (ind./m2) showed high positive values throughout the year (1508:1 on average); migratory species showed higher ratios. All results showed that downstream passage through the ladder is very limited, and that the facility allows only one-way movements (i.e., upstream). This is the first empirical evidence showing that a ladder is critically deficient for downstream passage of fishes in South America.

Studies on pharmacological properties of mucus and sting venom of Potamotrygon cf. henlei

Stingrays from the Potamotrygon cf. henlei species are widely distributed in high numbers throughout the rivers of central-west Brazil, being the source of numerous envenomations occurring in the dry season, posing a serious public health problem even if not properly reported. The accidents usually involve fishermen and bathers, and to date there is no effective treatment for the injured. Considering these facts and limitations of studies aiming at understanding the effects induced by P. cf. henlei envenoming, this study aimed to describe the principal pharmacological and certain biochemical properties of the mucus and sting venom. We found that mucus and sting venom is toxic to mice having nociceptive, edematogenic and proteolysis activities. Our results also indicate that the inflammatory cellular influx observed could be triggered by the venom and mucus. Furthermore the venom and mucus were partially purified by solid-phase extraction tested for antimicrobial activity in which only the mucus presented activity. It could be inferred from the present study that P. cf. henlei venom possesses a diverse mixture of peptides, enzymes and pharmacologically active components.

Characterization of a new bioactive peptide from Potamotrygon gr. orbignyi freshwater stingray venom

Brazilian freshwater stingrays, Potamotrygon gr. orbigyni, are relatively common in the middle-western regions of Brazil, where they are considered an important public health threat. In order to identify some of their naturally occurring toxin peptides available in very low amounts, we combine analytical protocols such as reversed-phase high-performance liquid chromatography (RP-HPLC), followed by a biological microcirculatory screening and mass spectrometry analysis. Using this approach, one bioactive peptide was identified and characterized, and two analogues were synthesized. The natural peptide named Porflan has the primary structure ESIVRPPPVEAKVEETPE (MW 2006.09 Da) and has no similarity with any bioactive peptide or protein found in public data banks. Bioassay protocols characterized peptides as presenting potent activity in a microcirculatory environment. The primary sequences and bioassay results, including interactions with the membrane phospholipids, suggest that these toxins are a new class of fish toxins, directly involved in the inflammatory processes of a stingray sting.

Trophic guilds of fishes in sandbank habitats of a Neotropical river

The objective of this study was to characterize the trophic structure of the community of fishes exploiting riverine sandbank habitats. Collections were carried out during the period of October 1999 to December 2003, on six sand banks in the upper and middle portions of the Tocantins River drainage basin in central Brazil. The availability of food resources was evaluated based on the volume of the items present in the stomachs of all species. A total of 2,127 stomachs of fish belonging to 50 species were analyzed. Nine main trophic guilds grouped the local ichthyofauna according to diet. Aquatic-origin items were the preferred source for 55.5% of the groups analyzed, whereas terrestrial-origin items composed 44.4%. Items of undetermined origin (detritus and sediment), although present in 89% of the guilds, were the predominant food in only one trophic group. Terrestrial insects and fish were the food sources with the largest biomass available in the environment. Sandbank environments are homogeneous, with little shelter and food available; as a rule, the species that occupy these environments are generalists.

Fish, Lajeado Reservoir, rio Tocantins drainage, State of Tocantins, Brazil

The Lajeado HR is the fourth hydroelectric power plant constructed in the rio Tocantins. The implementation of hydroelectric plants in the rio Tocantins basin is of high environmental concern because they may result in severe damage to the ichthyofauna. A species list of the area of influence of the Lajeado HR is provided, in the hope that it will contribute to the knowledge of this potentially threatened ichthyofauna. A few comments on the ichthyofauna of the rio Tocantins drainage are also provided.