Dr. Cristina Cox Fernandes

My work focuses on the ecology and evolutionary diversity of neotropical freshwater fishes, particularly within the Amazon River basin. Neotropical fishes make up a significant percentage of the worlds freshwater icthyofauna, with new species being described at an impressive rate. Much of my research aims to provide basic information about these fishes, from behavior and ecology, to taxonomy and sexual dimorphism within the electric fishes.

A hallmark feature of Amazonian fish is that they adapt to extreme seasonal changes in habitat properties such as water level, oxygen availability, and space. I am particularly interested in one such adaptation -- lateral migrations -- in which fishes swim away from floodplains when conditions are poor and return when conditions improve. This appears to be a basic and widespread adaptation, occuring in at least 20 Amazonian species. In my studies of lateral migration I have used various approaches, including direct observations and capture of migrating fishes, interviews with subsistence and commercial fisherman, assessment of habitat quality, and evaluation of fish physiological and reproductive condition. One of the significant results from my work concerns intrapopulation variation in behavior; some individuals a population engage in a reproductive migration, returning immediately to the same floodplain area, while other individuals migrate in what appears to be a dispersal event. This work raises additional questions that I would like to pursue, such as: What factors trigger lateral and longitudinal (upstream and downstream) migrations in Amazonian fishes? Do lateral migrations initate longitudinal migrations? How do fishes choose a floodplain habitat at the end of their longitudinal migrations? What are the effects of dispersion migrations on gene flow within these species?

My work also examines the large-scale ecology and distribution of benthic fishes across the Amazon basin. Since 1992 I have been involved in a project entitled 'Fish Diversity of the Principal Channels of the Amazon River', funded by the National Science Foundation and Brazil's Conselho Nacional de Pesquisas. In this research my collaborators and I have been trawling the Amazon river channel in Brazil (about 3,500 km) and the lower reaches of its major tributaries. We have documented a remarkable abundance and diversity of fishes, over 360 species, most of which are catfishes and electric fishes, and several of which are new to science. This project has provided an immense data set for the quantitative study of the community ecology of these fishes. One of my preliminary findings is that the distribution and community structure of the 40 or so electric fish species in this region is strongly influenced by the location of tributaries, and by the physiochemical features of the water. For instance, diversity appears to increase immediately downstream of tributaries, and some familes, such as the Apteronotidae, are significantly more abundant in 'white' waters while others, such as the Sternopygidae, are more abundant in 'clear' and 'black' waters. I plan to assess the community structure of other benthic fish groups as well, when taxonomy of the more complex groups is resolved. Another planned project, currently under grant review, is to study the behavior of fishes in the deep water of the Negro River, using underwater filming equipment. This project will be conducted in collaboration with John Lundberg and Bret Hobson, a specialist in underwater imaging. One of the goals of this work is to learn how these benthic fishes are distributed in their habitat -- for example, are they clustered, or evenly spaced, or territorial?

Another part of my present work deals with Gymnotiformes (electric fish) taxonomy, which comprises over 100 species. My interest in the taxonomy of this group was initially geared towards species identification, for my work on community ecology. As part of my training I have visited all of the electric fish collections in the United States and Brazil, and have regularly been collecting new specimens in central Amazonia. With colleagues I have recently described a new genus of electric fish with two species. I have also discovered a pronounced morpholgical sexual dimorphism in several species in the family Apteronotidae, the most diverse family of Gymnotiformes. Males of these species exhibit unusually long snouts, which had led them to be classified intially in genera separate from the females. I discovered this dimorphism while examining the gonads of museum specimens, when I realized that all of the hypermorphic individuals were male. Another case of a taxonomic error resulting from sexual dimorphism occured in the genus Oedegmognathus, in which fishes with teeth outside of their mouths were initially classified in one genus while individuals without this character were classified in another genus. Fishes with teeth outside of their mouths turn out to all be males. My long term goal with the sexual dimorphism work is to map the different traits onto a phylogenetic tree, to understand the relationships among the species, and the steps by which the traits evolved.

Study the biology of the South American lungfish, Lepidosiren paradoxa (Dipnoi: Lepidosirenidae) with W. E. Bemis.