Many of the most important commercial and recreational species of the megadiverse Brazilian freshwater fishes migrate in rivers among essential habitats during all life stages. These movements, however, have been severely blocked by hundreds of hydroelectric dams and reservoirs and they will be even more obstructed due to hundreds of new developments. Fishways have been used in many countries to allow fish to pass around dams. Fishway construction is booming in Brazil, but poor understanding of migrations by Brazilian fishes has led legislators, scientists, and the public to several misconceptions about the rules of fishways in fisheries conservation. First, is a belief that fishways are only needed to facilitate upstream spawning migrations. Also, it has been suggested that upstream passage for Neotropical migrant fishes is not useful if there is no large free-flowing stretch upstream of a dam that contains spawning habitat and has a large natural floodplain (nursery habitat). In this paper, we discuss that, in addition to providing passage for pre-spawning migrants, upstream fishways also provide passage for other fish migrations (e.g. foraging), and that all up-and downstream migrations during life history need to be addressed at dams to conserve fish resources. We also argue that an upstream fishway is important even if the upstream reach does not have spawning or nursery habitats. In addition, we discuss the need for protection of downstream migrant fish, and the importance of fish behaviourists and engineers working together on fishway design and operation to solve fish passage issues.

Abstract.-It is difficult for agencies to evaluate the impacts of the many planned dams on São Francisco River, Brazil, migratory fishes because fish migrations are poorly known. We conducted a study on zulega Prochilodus argenteus, an important commercial and recreational fish in the São Francisco River, to identify migrations and spawning areas and to determine linear home range. During two spawning seasons (2001)(2002)(2003), we radio-tagged fish in three main-stem reaches downstream of Três Marias Dam (TMD), located at river kilometer (rkm) 2,109. We tagged 10 fish at Três Marias (TM), which is 5 km downstream of TMD; 12 fish at Pontal, which is 28 km downstream of TMD and which includes the mouth of the Abaeté River; and 10 fish at Cilga, which is 45 km downstream of TMD. Late-stage (ripe) adults tagged in each area during the spawning season remained at or near the tagging site, except for four Cilga fish that went to Pontal and probably spawned. The Pontal area at the Abaeté River mouth was the most important spawning site we found. Prespawning fish moved back and forth between main-stem staging areas upstream of the Abaeté River mouth and Pontal for short visits. These multiple visits were probably needed as ripe fish waited for spawning cues from a flooding Abaeté River. Some fish homed to prespawning staging areas, spawning areas, and nonspawning areas. The migratory style of zulega was dualistic, with resident and migratory fish. Total linear home range was also dualistic, with small (,26-km) and large (53-127-km) ranges. The locations of spawning areas and home ranges suggest that the Pontal group (which includes Cilga fish) is one population that occupies about 110 km. The Pontal population overlaps a short distance with a population located downstream of Cilga. Movements of late-stage TM adults suggest that the TM group is a separate population, possibly with connections to populations upstream of TMD.

Surubim, Pseudoplatystoma corruscans, is the most valuable commercial and recreational fish in the Sã o Francisco River, but little is known about adult migration and spawning. Movements of 24 females (9.5-29.0 kg), which were radio-tagged just downstream of Trê s Marias Dam (TMD) at river kilometer 2,109 and at Pirapora Rapids (PR) 129 km downstream of TMD, suggest the following conceptual model of adult female migration and spawning. The tagged surubims used only 274 km of the main stem downstream of TMD and two tributaries, the Velhas and Abaeté rivers. Migration style was dualistic with non-migratory (resident) and migratory fish. Pre-spawning females swam at ground speeds of up to 31 km day -1 in late September-December to pre-spawning staging sites located 0-11 km from the spawning ground. In the spawning season (November-March), prespawning females migrated back and forth from nearby pre-spawning staging sites to PR for short visits to spawn, mostly during floods. Multiple visits to the spawning site suggest surubim is a multiple spawner. Most post-spawning surubims left the spawning ground to forage elsewhere, but some stayed at the spawning site until the next spawning season. Post-spawning migrants swam up or downstream at ground speeds up to 29 km day -1 during January-March. Construction of proposed dams in the main stem and tributaries downstream of TMD will greatly reduce surubim abundance by blocking migrations and changing the river into reservoirs that eliminate riverine spawning and non-spawning habitats, and possibly, cause extirpation of populations.

We used metadata on nine reproductive traits of 67 species of Brazilian iteroparous, oviparous, teleost freshwater fishes to test phenotypes associations to discriminate species that only spawn in large rivers (lotic fishes) from those capable to spawn in lentic habitats (lentic fishes). We tested the hypothesis that lotic fishes present spawning migration, shorter spawning season, single spawning, no parental care, free eggs, higher relative fecundity, faster embryogenesis, and larger size, while lentic fishes present no spawning migration, longer spawning season, multiple spawning, parental care, adhesive eggs, lower relative fecundity, slower embryogenesis, and smaller size. Our analyses supported the hypothesis but not all phenotypic associations satisfied it, specifically with regard to lentic fishes or to pairs of phenotypes typical of lentic fishes. We also concluded that spawning in large rivers is a better predictor of bionomic characters than spawning in lentic habitats, and lotic fishes are specialists compared to lentic fishes.

In the Rio Doce basin of southeastern Brazil, the freshwater fish Hoplias malabaricus (trahira) is a widespread predatory characin and one of the few resilient native fishes in a highly impacted lake system. In order to test for genetic differentiation in populations within this basin and for biogeographic relationships among populations of this species in other basins, a study was conducted using RAPD-PCR analysis of Rio Doce samples (N = 63) and phylogeographic analyses with mitochondrial DNA (mtDNA) haplotypes, including the Rio Grande and Macacu river basins. In the Rio Doce basin, the patterns of genetic similarity of RAPD-PCR markers (individual fingerprinting and Nei's genetic distance) suggest the existence of two genetically different groups, one composed of the lacustrine populations Carioca and Dom Helvécio, and the other of riverine and the remaining lacustrine populations. The differences in the RAPD-PCR patterns may be explained by the existence of sub-basins within this lacustrine system. A maximum parsimony tree of cytochrome b fragment (383 base pairs) supports the view that trahiras of the Rio Doce share a complex biogeographic history with those of neighboring basins. The phylogeographic patterns may be explained by a common history of the watersheds of the Rio Doce, Paraíba do Sul, and Rio Grande basins, corroborating the hypothesis of a Plio-Pleistocene separation of these drainage systems, forming the Mantiqueira "divortium aquarium".

SynopsisReproduction in female Serrasalmus spilopleura (Characiformes, Characidae) from the Itumbiara reservoir (18°28' S, 48°36' W), Paranaiba River, Brazil, was examined with emphasis on the relationship between condition factors and coelomic fat, the annual reproductive cycle and the unusual dynamics of its sexual maturity .The condition factor and coelomic fat index follow a similar pattern along the stages of reproductive cycle .Variations in the condition factor along the reproductive cycle were assigned to variations in the fat contents of the carcass . Serrasalmus spilopleura exhibits characteristics of partial spawning fish and reproduces throughout the year . Sexual maturity occurs at 17 .8 cm standard length . Resting and totally spent females were not captured . Females cycle from partially spent to intermediate/advanced maturation without going into the totally spent or resting stages. The initial maturation stage is restricted to fish of intermediate size .Once the initial maturation stage has started the fish remains there for a considerable period of its lifetime before entering in the intermediate maturation stage, an uncommon sexual maturity pattern . The long duration of the initial maturation stage was responsible for the females not returning to the resting stage after spawning .

Upstream fish passage was evaluated during 12 months in the vertical-slot Igarapava Fish Ladder constructed around Igarapava Dam, in the heavily dammed Grande River, Southeast Brazil. A video monitoring system was used to observe 61,621 fish that passed the ladder, of which 93.5% were identified to 15 taxa. Among the migratory species, the most abundant were Pimelodus maculatus (33.6% of all fish), Leporinus octofasciatus (31.4%), Leporinus friderici (4.5%), and Prochilodus lineatus (3.1%). Seven taxa were classified as nonmigratory, and of these taxa, the small Bryconamericus stramineus was the most abundant (12.7%) of all fishes. Passage of the 'nonmigratory' taxa upstream in the ladder shows they are migratory in this system and have a strong behavioural drive to move to upstream habitat. Passage of most taxa had a strong seasonal pattern. While some species passed primarily during the day, others showed a distinct nocturnal pattern. Lunar phase and water temperature also strongly affected passage of some taxa. Rainfall and dam discharge had a small or null influence on most taxa; perhaps due to the fairly small catchment area of the reservoir and the highly regulated discharge at Igarapava Dam.

DIET OF FOUR SPECIES OF LEPORINUS (CHARACIFORMES, ANOSTOMIDAE) DURING FORMATION OF A RESERVOIR IN SOUTHEAST BRAZIL.The study reports the changes ocurred in feeding ecology of fish species during a tropical river reservoir formation. It was analysed the stomachal contents of 399 individuals belonging to four species of genus Leporinus (L. elongatus Valenciennes, 1849, n=157; L. friderici (Bloch, 1794), n=87; L. octofasciatus Steindachner, 1917, n=107; L. amblyrhynchus Garavello & Britski, 1987, n=48) during formation of Nova Ponte reservoir, State of Minas Gerais, Brazil, in 1993 and 1994. Specimens were separated by sampling period, according with the rate of filling of the reservoir, and standard lenght classes. The species had included in diet vegetal and animal items of autochtone and alochtone origin in several proportions. L. amblyrhynchus fed on basically dipterans in all the sampling periods and length classes. L. elongatus had presented a diverse diet, with predominance of dipterans and vegetal items, and changed the consumed items proportions along the sampling periods and between lenght classes. L. friderici diet was composed mainly by terrestrial insects during the rapid filling period, that were later substituted by fishes and vegetal items. Ontogenetic trophic changes were observed in this species. L. octofasciatus presented a well characterized herbivorous diet, without trophic ontogeny, but with a opportunistic character. Just three pair-species, L. amblyrhynchus-L. elongatus, L. friderici-L. octofasciatus and L. elongatus-L. octofasciatus, have presented some high value of trophic overlap in at least one sampling period. In spite of the fishes of the genus Leporinus being classified like omnivorous in a general way, the differences found between diets of these four species suggest that there is structuration of trophic niches in the reservoir.