Sergio Makrakis

Diversity in migratory patterns among Neotropical fishes in a highly regulated river basin

Migratory behaviour of selected fish species is described in the Paraná River, Brazil-Argentina-Paraguay, to search for patterns relevant to tropical regulated river systems. In a 10 year mark-recapture study, spanning a 1425 km section of the river, 32 867 fishes composed of 18 species were released and 1083 fishes were recaptured. The fishes recaptured were at liberty an average 166 days (maximum 1548 days) and travelled an average 35 km (range 0-625 km). Cluster analysis applied to variables descriptive of movement behaviour identified four general movement patterns. Cluster 1 included species that moved long distances (mean 164 km) upstream (54%) and downstream (40%) the mainstem river and showed high incidence (27%) of passage through dams; cluster 2 also exhibited high rate of movement along the mainstem (49% upstream, 13% downstream), but moved small distances (mean 10 km); cluster 3 included the most fishes moving laterally into tributaries (45%) or not moving at all (25%), but little downstream movement (8%); fishes in cluster 4 exhibited little upstream movement (13%) and farthest downstream movements (mean 41 km). Whereas species could be numerically clustered with statistical models, a species ordination showed ample spread, suggesting that species exhibit diverse movement patterns that cannot be easily classified into just a few classes. The cluster and ordination procedures also showed that adults and juveniles of the same species exhibit similar movement patterns. Conventional concepts about Neotropical migratory fishes portray them as travelling long distances upstream. The present results broaden these concepts suggesting that migratory movements are more diverse, could be long, short or at times absent, upriver, downriver or lateral, and the diversity of movements can vary within and among species. The intense lateral migrations exhibited by a diversity of species, especially to and from large tributaries (above reservoirs) and reservoir tributaries, illustrate the importance of these habitats for the fish species life cycle. Considering that the Paraná River is highly impounded, special attention should be given to the few remaining low-impact habitats as they continue to be targets of hydropower development that will probably intensify the effects on migratory fish stocks.

Passage performance of long-distance upstream migrants at a large dam on the Paraná River and the compounding effects of entry and ascent

This paper presents results of a fishway evaluation performed at the Engenheiro Sergio Motta Hydroelectric Power Plant (known as Porto Primavera) - CESP, Parana River, Brazil. The evaluation was designed to quantify entry and passage proportions of 4 long-distance migratory fish species: Brycon orbignyanus (piracanjuba), Piaractus mesopotamicus (pacu), Prochilodus lineatus (curimba), and Rhinelepis aspera (cascudo-preto). Proportions finding and entering the fishway differed between species, ranged from 7.4 % (Prochilodus lineatus) to 55.4% (Piaractus mesopotamicus). Also, proportion passing was different between species, ranged from 31% (R. aspera) to 100% (Prochilodus lineatus). Fish that were marked and released within the fishway had greater failure rates than those that entered volitionally. Total time to pass ranged from 1.48 hours (Prochilodus lineatus) to 178.9 hours (R. aspera). Failure rates were greatest in the lower end of the fishway. Although some individuals of all species passed successfully, significant challenges remain to restoring connectivity of the upper Parana River.

Genetic structure and diversity of migratory freshwater fish in a fragmented Neotropical river system

Over the past few decades, South American Rivers, including the Paraná River system, have been intensely impacted by dam constructions. To mitigate adverse impacts, fish passages were incorporated into two large dams on the Paraná River (Itaipu and Porto Primavera) to reestablish longitudinal connectivity, which is very important for conserving populations of migratory fish species. The aim of this study was to estimate genetic diversity, population differentiation and gene flow, using microsatellites markers and mitochondrial haplotypes (d-loop), in populations of Prochilodus lineatus, a long distance migratory species commonly found in Paraná River basin drainages. Samples were obtained from six locations in the Upper and Middle Paraná River: Porto Primavera Reservoir, downstream of the Porto Primavera Reservoir, four tributaries of this reservoir (Pardo, Peixe, Verde and Aguapeí Rivers) and in the Iguaçu River, downstream of the Itaipu dam. High genetic diversity was observed in all samples, as expected for species with large population sizes and high migration rates. However, the influence of other factors, such as secondary contacts, fish passages and restocking were also suggested. In general, evidence of spatial population structuring was not found, even though there were two large dams in the study area. This could also be attributed to the brief period that has elapsed since the dams were built, the influence of migratory and reproductive patterns and the possible contributory effects of the fish passages. Furthermore, the absence of population structuring also corroborates existing information that emphasizes the importance of unimpeded tributaries for conserving migratory fish populations in fragmented watersheds.

A barrier to upstream migration in the fish passage of Itaipu Dam (Canal da Piracema), Paraná River basin

The majority of the fish passages built in the Neotropical region are characterised by low efficiency and high selectivity; in many cases, the benefits to fish populations are uncertain. Studies conducted in the Canal da Piracema at Itaipu dam on the Parana River indicate that the system component designated as the Discharge channel in the Bela Vista River (herein named Canal de desague no rio Bela Vista or CABV), a 200 m long technical section, was the main barrier to the upstream migration. The aim of this study was to evaluate the degree of restriction imposed by the CABV on upstream movements of Prochilodus lineatus and Leporinus elongatus, Characiformes. Fish were tagged with passive integrated transponders (PIT tags) and released both downstream and upstream of this critical section. Individuals of both species released downstream of the CABV took much more time to reach the upper end of the system (43.6 days vs. 15.9 days), and passed in much lower proportions (18% vs. 60.8%) than those tagged upstream of this component. Although more work is needed to differentiate between fishway effects and natural variation in migratory motivation, the results clearly demonstrate passage problems at the CABV.

Culverts in paved roads as suitable passages for Neotropical fish species

Improperly installed or poorly maintained culverts can pose a serious threat to fish by disrupting their habitat and endangering spawning success. Road culverts that are not designed for fish passage frequently can become obstacles. This can be especially problematic for migratory species, but can lead to fragmentation of resident populations as well. This study evaluated 40 culverts of 29 sites within a 25-km radius from Toledo city, Parana State, southern Brazil, with respect to their likely effects on movement of the local ichthyofauna. We collected data on the shape and length of culverts, culvert material, waterfall height, water column depth, slope, and estimated flow velocity. Culverts were categorized by level of barrier risk for upstream migration: high, medium, low, and impassable, as well as the type of barrier posed (fall height, depth, length and velocity). Most of culverts analyzed were considered potential barriers to fish movement, with 45% classified as impassible, 45% as high risk, 10% as medium risk, and no culverts as low risk. Brazilian culverts as fishways will require additional monitoring and studies to corroborate the premises proposed in the present study. Road culvert projects that are properly built and maintained will be able to simultaneously improve function of roadways and protect fish populations. Bueiros incorretamente instalados ou mal conservados podem representar uma seria ameaca para os peixes por fragmentar o seu habitat e comprometer o sucesso da desova. Bueiros em estradas que nao sao projetados para passagem de peixes frequentemente tornam-se obstaculos. Isso pode ser especialmente problematico para as especies migratorias, mas tambem pode levar a fragmentacao das populacoes de peixes residentes. Este estudo avaliou 29 locais com 40 bueiros dentro de um raio de 25 km de Toledo, Estado do Parana, sul do Brasil, com relacao aos seus provaveis efeitos sobre a movimentacao da ictiofauna local. Dados foram coletados sobre a forma e o comprimento dos bueiros, material utilizado, altura da queda de agua, profundidade, declividade e velocidade estimada do fluxo. Os bueiros foram categorizados pelo nivel de risco como barreira a migracao ascendente: alto, medio, baixo e impassavel, bem como o tipo de barreira imposta (altura da queda, profundidade, comprimento e velocidade). A maioria dos bueiros analisados foi considerada barreira para o movimento dos peixes, com 45% classificados como intransitaveis, 45% como alto risco, 10 % como medio risco, nao havendo bueiros com baixo risco. Bueiros brasileiros como passagens para peixes necessitarao de monitoramento e estudos adicionais para corroborar as premissas propostas no presente estudo. Projetos de bueiros em estradas que estao devidamente construidos e mantidos serao capazes de simultaneamente melhorar a funcao das rodovias e proteger as populacoes de peixes.

The use of morphometric analysis to predict the swimming efficiency of two Neotropical long-distance migratory species in fish passage

This study investigated the external body morphology (based on morphometric data) and the swimming efficiency in fish passages (based on the ascent time in a fish ladder) of two Neotropical long-distance migratory species. The fish were collected in the fish ladder of the Porto Primavera Hydroelectric Power Plant (known as Engenheiro Sergio Motta), upper Parana River, Brazil. The species differ in several morphometric ratios related to swimming performance. Prochilodus lineatus exhibited a higher muscle ratio and caudal fin length ratio. However, Leporinus elongatus showed higher values for the fineness ratio, a higher length from snout to pectoral fin base ratio, and a higher caudal peduncle depth factor. Although both species show good swimming performance, the characteristics listed above may enable L. elongatus to apply greater power and propulsion, allowing it to reach a high swimming speed and to exhibit greater efficiency than P. lineatus. Leporinus elongatus moves faster than P. lineatus and has a lower mean ascent time (1.39 hours) than P. lineatus (3.76 hours). Prochilodus lineatus would require a somewhat longer time to pass through the fish ladder.

Genetic Diversity of the Endangered Neotropical Cichlid Fish (Gymnogeophagus setequedas) in Brazil

Gymnogeophagus setequedas is a rare and rheophilic species of tribe Geophagini, considered endangered in Brazilian red lists. Its previously known geographical distribution range was the Paraná River basin, in Paraguay, and a tributary of the Itaipu Reservoir in Brazil. Since its description no specimens have been collected in the original known distribution area. However, recent records of G. setequedas in the lower Iguaçu River, in a region considered highly endemic for the ichthyofauna, extended the known geographical distribution and may represent one of the last remnants of the species. The aim of this study was to estimate the genetic diversity and population structure of G. setequedas, using microsatellite markers and mitochondrial haplotypes, in order to test the hypothesis of low genetic diversity in this restricted population. Muscular tissue samples of 86 specimens were obtained from nine locations in the Lower Iguaçu River basin, between upstream of the Iguaçu Falls and downstream of the Salto Caxias Reservoir. Seven microsatellites loci were examined and a total of 120 different alleles were obtained. The number of alleles per locus (NA) was 17.429, effective alleles (NE) 6.644, expected heterozygosity (HE) 0.675, observed (HO) heterozygosity 0.592, and inbreeding coefficient (FIS) 0.128. Twelve haplotypes in the D-Loop region were revealed, with values of h (0.7642) and π (0.00729), suggesting a large and stable population with a long evolutionary history. Thus, both molecular markers revealed high levels of genetic diversity and indicated the occurrence of a single G. setequedas population distributed along a stretch of approximately 200 km. The pattern of mismatch distribution was multimodal, which is usually ascribed to populations in demographic equilibrium. Nevertheless, the construction of a new hydroelectric power plant, already underway between the Salto Caxias Reservoir and Iguaçu Falls, could fragment this population, causing loss of genetic diversity and population decline, and for this reason it is necessary to maintain the Iguaçu River tributaries and downstream area from the Lower Iguaçu Reservoir free of additional dams, to guarantee the survival of this species.

Desenvolvimento embrionário, larval e juvenil de Hemisorubim platyrhynchos (Siluriformes, Pimelodidae) da bacia do rio Paraná

O objetivo deste estudo foi descrever o desenvolvimento embrionario, larval e juvenil da jurupoca, Hemisorubim platyrhynchos (Valenciennes, 1840), bem como as mudancas nos padroes de crescimento alometrico durante a ontogenia inicial da especie. Um total de 90 ovos, 210 larvas e 24 juvenis provenientes de reproducao induzida foram analisados quanto a variaveis morfometricas e meristicas, alem do coeficiente de crescimento alometrico em relacao a cabeca, tronco e cauda durante o periodo larval e juvenil inicial. Os ovos apresentaram diâmetro medio de 1,74 mm, espaco perivitelino amplo (21,29%), com media de 0,37 mm, e diâmetro medio do vitelo de 1,08 mm. O comprimento padrao (CP) das larvas variou de 3,47 a 11,85 mm, com a maioria das medidas apresentando aumento proporcional ao longo do desenvolvimento. O numero total de miomeros variou de 40 a 46 (pre-anal=15-17 e pos-anal=24-30). As larvas iniciais de H. platyrhynchos apresentam pigmentacao na cabeca e na regiao ântero-ventral do corpo (anterior e posterior do saco vitelino). No estagio de pos-flexao, a pigmentacao se intensifica, distribuindo-se na regiao dorsal da cabeca, formando uma faixa longitudinal que se estende do focinho ao operculo, assim como uma faixa transversal, de um flanco a outro, passando pela regiao anterior da nadadeira dorsal, com maculas distribuidas ao longo do corpo nos juvenis (CP=19,5-49,09 mm). Nos primeiros estagios de desenvolvimento larval, a cabeca e a cauda crescem muito mais rapidamente do que o tronco, o que indica prioridades relacionadas a alimentacao e natacao, as quais posteriormente tendem a isometria, com um crescimento rapido do tronco nos juvenis iniciais.

Mudanças morfológicas no trato digestório e composição da dieta de larvas e juvenis do linguado catathyridium jenynsii no reservatório de Itaipu, rio Paraná, Brasil

The objective of this study was to characterize the diet and digestive tract morphology of flounder, catathyridium jenynsii (gunther, 1862) (achiridae), in its early stages of life. for analysis of the digestive tract, we used a specimen of each larval stage, pre-flexion to post-flexion, and juvenile. a total of 256 larvae and 16 juveniles, belonging to five classes of standard length was analyzed for diet. data were collected in the itaipu reservoir, parana river, brazil, from september, 2001 to march, 2002, and from september, 2002 to february, 2003. the occurrence and numerical methods were applied for determining the occurrence frequency and numerical frequency of each food item in different standard length (sl) classes. the anterior digestive tract of c. jenynsii began to differentiate into the stomach at 4.70 mm sl (not presented pyloric caeca). since the stage of pre-flexion, there are three intestinal folds and a lot of grooves in the digestive tract. the dietary analysis showed that the smaller larvae (class 1) had a distinct diet, with dominance of cladocerans (mainly bosmina hagmanni and bosminopsis deitersi). for class 2, the copepod notodiaptomus sp. was important both in number and occurrence, however b. hagmanni also had significant importance in the diet. already the largest larvae (classes 3 and 4) and juveniles (class 5) showed a similar diet, consuming mainly copepods (notodiaptomus sp.). therefore, in this study, larvae of c. jenynsii can be considered zooplanktivore, since in all stages of development, copedods and cladocerans dominated the diet. changes in diet followed the morphological changes of the early stages of c. jenynsii.

Longitudinal habitat disruption in Neotropical streams: fish assemblages under the influence of culverts

This study assessed differences in fish assemblages existing upstream and downstream two types of culverts, one on each of two different Neotropical streams. We analyzed the composition and structure of the ichthyofauna and tested for spatial patterns. Fish sampling was carried out monthly between November 2009 and October 2010 using different fishing gears. We collected 2,220 fish of 33 species; 901 in stretches of the Lopei stream - circular culvert and 1,310 in stretches of the Pindorama stream - box culvert. Fish abundance was similar in upstream and downstream stretches of the circular culvert, whereas it was slightly higher in the upstream than downstream stretch for the box culvert. Characiformes predominated in the upstream stretch of both culverts. On the other hand, Siluriformes was abundant in the downstream stretch of the circular culvert, with similar abundance in the stretches of the box culvert. Species richness and diversity (Shannon-Weiner Index) were higher in the downstream stretch of the circular culvert, but they were similar in both stretches of the box culvert. The most abundant species were Astyanax altiparanae, A. paranae, A. fasciatus, Ancistrus sp., and Hypostomus sp. The last two species were more abundant in the downstream stretch of the circular culvert, and similar in stretches of the box culvert. Our study indicated variations in the species abundance, richness, and diversity between upstream and downstream stretches in particular of the circular culvert in the Lopei stream, suggesting that fish movements are restrained more intensively in this culvert, especially for Siluriformes. The drop in the circular culvert outlet probably created passage barriers especially for those fish that has no ability to jump, where downstream erosion could lead to culvert perching. Studies on appropriate road crossing design or installation are fundamental whereas improvements in these structures can restore the connectivity of fish populations and communities in streams.