Hugo Luis López

Freshwater Ecoregions of the World: A New Map of Biogeographic Units for Freshwater Biodiversity Conservation

ABSTRACT We present a new map depicting the first global biogeographic regionalization of Earths freshwater systems. This map of freshwater ecoregions is based on the distributions and compositions of freshwater fish species and incorporates major ecological and evolutionary patterns. Covering virtually all freshwater habitats on Earth, this ecoregion map, together with associated species data, is a useful tool for underpinning global and regional conservation planning efforts (particularly to identify outstanding and imperiled freshwater systems); for serving as a logical framework for large-scale conservation strategies; and for providing a global-scale knowledge base for increasing freshwater biogeographic literacy. Preliminary data for fish species compiled by ecoregion reveal some previously unrecognized areas of high biodiversity, highlighting the benefit of looking at the worlds freshwaters through a new framework.

Distribution of introduced and native fish in Patagonia (Argentina): patterns and changes in fish assemblages

The interaction between native fishes and salmonids introduced in Patagonia at the beginning of the 20th Century, developed at the same time as the environmental change. The phenomenon of global warming has led to the formulation of predictions in relation to changes in the distribution of species, in the latitudinal dimension, both at intralacustrine, or small streams levels. The aim of the present work includes three main objectives: a) to compose a general and updated picture of the latitudinal distribution range of native and alien fishes, b) to analyze the historical changes in the relative abundance of Percichthys trucha, Odontesthes sp., and salmonids in lakes and reservoirs, and c) to relate the diversity and relative abundance of native and salmonid fishes to the environmental variables of lakes and reservoirs. We analysed previous records and an ensemble of data about new locations along the northern border of the Patagonian Province. We compared current data about the relative abundance of native fishes and salmonids in lakes and reservoirs, with previous databases (1984–1987). All samplings considered were performed during spring-summer surveys and include relative abundance, as proportions of salmonids, P. trucha, and Odontesthes sp. For the first time, we found changes in fish assemblages from twenty years back up to the present: a significant decline in the relative abundances of salmonids and an increase of P. trucha. We studied the association between the diversity and relative abundance of native and salmonid fishes and the environmental variables of lakes and reservoirs using Canonical Correspondence Analysis. Relative abundance showed mainly geographical cues and the diversity relied largely on morphometric characteristics. Relative abundance and diversity seem to have a common point in the lake area, included into the PAR concept. Native abundance and alien diversity were negatively related with latitude. Greater native diversity was observed in lakes with high PAR compared with salmonids. Historical changes such as southward dispersion, relative abundance changes, and geographical patterns for relative abundance and diversity are basic concepts needed not only in future research but also in management design for Patagonian fish populations.

Fishes of southern South America: a story driven by temperature.

The latitudinal extension of southern South America imposes a thermal gradient that affects the structure of marine and freshwater fish assemblages and the biology of the species through direct exposure to the temperature gradients or by means of a web of historical and ecological relationships. We have reviewed biological and ecological data of marine and freshwater fishes from the southern Neotropics, including Patagonia, and report several examples of dependence on temperature, from glacial times to today’s climate change. We were able to identify historic and present effects on the diversity of fish assemblages, isolation, southern limits for the distribution of species, and morphological variation among populations. There is a wide range of characteristics that exemplify an adaptation to low temperatures, including biochemical peculiarities, physiological adjustments, and alternative life history patterns, and these appear in both freshwater and marine, and native and exotic fishes. The consequences of stable temperature regimes in both the ocean and thermal streams deserve special mention as these shape specialists under conditions of low selective pressure. At present, habitat use and interactions among species are being subject to changes as consequences of water temperature, and some of these are already evident in the northern and southern hemispheres.

Fish fauna and environments of the Pilcomayo-Paraguay basins in Formosa, Argentina

The ichthyofauna from subtropical (East) and tropical (West) areas in the Formosa province (Northern Argentina) is analyzed. An up-to-date list of fishes is provided, including 18 new reports for environments associated with the Pilcomayo and Paraguay rivers, considering the detailed distribution of the fishes. Dominant families in terms of number of species are Characidae, Pimelodidae, Loricariidae and Curimatidae. Percentage of individuals (about 5000 examined) were 66% for characoids and 25% for siluriforms, with less than 10% for other groups. Comparisons were made with other South American environments. Most frequent species were Psellogrammus kennedyi, Astyanax bimaculatus, Gymnocorymbus ternetzi, Hoplosternum thoracatum and Cichlasoma portalegrense. The predominant type of environment sampled, of small size and shallow depth, with extensive plant cover, and temporal level variations, explains the dominance of the above groups. This interpretation is supported by independent studies. Diversity values ranged between 0.71 and 3.92. A marked reduction in number of species from East to West was observed (79 and 41 species respectively, 31 shared). No species of Gymnotidae, Hemiodidae, Characidiidae, Trichomycteridae, Lebiasinidae nor Aspredinidae were captured in the West. The higher number of species in eastern environments is considered to be due to the influence of the Paraguay river and the complex hydrology of the area. Other factors, both historical and ecological are considered. A correlation between total phosphorous content in the water and fish richness is also suggested. Water chemistry is compared with near by environments. Sites studied showed pH values from 6.14 to 7.5. The dissolved solid contents ranged from 51.8 to 474.3 mg 1−1, within the hypohaline level. Ionic composition differed somewhat between East and West, water in the East being mainly hypocalcic, as in the Paraguay river. Conductivity was rather variable and Secchi disk values similar to those in the Parana river.

Nuevas localidades para peces de agua dulce de la argentina: IV. Adiciones a la ictiofauna del río uruguay y algunos afluentes(1)

From 58 species collected in the Uruguay river and some of its affluents, new localities are reported for six Characoidei species (Schizodon platae, Glandulocauda terofali, Holoshestes pequira, Hyphessobrycon luetkeni, H. meridionalis and Aphyocharax rubropinnis) and for three Siluriformes (Megalodoras laevigatulus, Auchenipterus nuchalis and Bunocephalus ihe‐ringi). For these nine species morphological data and complete Argentine references are given. Chemical data on the affluents are checked with those from neighbouring areas.

Hyphessobrycon nicolasi (Teleostei: Characidae) a new species from the Uruguay River basin in the Mesopotamian Region, Argentina

Hyphessobrycon nicolasi is described from the Uruguay River basin in the Mesopotamian Region, Entre Rios, Argentina. The new species can be distinguished from all congeners by the presence of a well-defined oblique and marginal black stripe on each lobe of the caudal fin. Other characters defining H. nicolasi are the possession of 1-3 teeth with 3-10 cusps on maxilla; outer premaxillary row with 2-3 small teeth, with 5 or 7 cusps; iv-vi, 27-36 anal-fin rays; 33-36 scales on the longitudinal series; two vertical dark spots on the humeral region; dorsal and anal fins dappled in black and base of caudal fin bearing conspicuous black spot; and the presence of bony hooks on the rays of dorsal, anal and caudal fins of the mature males.

Biological data and Otolith (Sagitta) morphology of Polyprion americanus and schedophilus griseolineatus (Osteichthyes, Serranidae and Centrolophidae) 1

Summary Morphometrical data, feeding habits, sexual maturity stage, weight and otolith morphology of Polyprion americanus (Serranidae) and Schedophilus griseolineatus (Centrolophidae) are given based on a relatively large number of specimens captured in the Argentine sea during a research trip aboard the R/V “Orient Maru I”;. Temperature and depth for each station are recorded and the relationships of the studied species with others in the area commented. A detailed synonymy and a full bibliography are added. Current knowledge of the biology of both species is scarce.

Hypostomus derbyi (haseman) e hypostomus myersi (gosline), description complementaria y primeros registros Para Argentina (Pisces, loricariidae)∗

Hypostomus derbyi (Haseman) and Hypostomus myersi (Gosline), complementary description and first records for Argentina (Pisces, Loricariidae). ‐These species are recorded in Argentina upstream of Iguazu Falls and Urugua‐i Falls. H. myersi record is the first after the original description. Morphometrical, meristics and biological data of both species are given. These are briefly compared with related forms from the Parana Basin.

New records of Astyanax pelegrini Eigenmann, 1907 and Triportheus pantanensis Malabarba, 2004 (Actinopterygii: Characiformes: Characidae) for the Río Pilcomayo National Park and Ramsar Site in the province of Formosa, Argentina

This note presents the first records of Astyanax pelegrini Eigenmann, 1907 and Triportheus pantanensis Malabarba, 2004 for the province of Formosa, Argentina from fish surveys conducted in the Rio Pilcomayo National Park and Ramsar Site. In the case of T. pantanensis , this occurrence represents the first record of this species for Argentina.

Fish fauna from Río Pilcomayo National Park and Ramsar Site and its surroundings, Formosa, Argentina

The first list of fish species from the Rio Pilcomayo National Park and Ramsar Site (RPNP), located in the Wet Chaco plains of northern Argentina is presented here. Samplings were carried out bimonthly from December 2006 to January 2008 in sites representative of the different landscapes, in both dry and wet seasons. A total of 77 species were collected, belonging to 23 families and eight orders and covering 54% of the province ichthyofauna. New records to the Province of Formosa are Brachyhypopomus gauderio Giora & Malabarba, 2009; Cyanocharax sp. and Hypophthalmus edentatus Spix & Agassiz, 1829.