Oxidative enzymes in the urinary apparatus of several marine fishes

Summary The distribution and activities of several oxidative enzymes in the urinary apparatus of seven marine fish species (hagfish, lesser spotted dogfish, electric ray, herring, marine catfish, cod, sea-horse) have been studied. Species were selected from three main taxonomic groups: Cyclostomata, Elasmobranchii and Teleostei. Distinctly positive enzyme reactions were found in the tubular elements of the kidney and the collecting duct-archinephric duct system, with the exception of the generally weak staining intensities for NADP-liked malate dehydrogenase. In the proximal tubule segment the second, more distal part (PII) reacted, in general, very strongly when compared with the first proximal part (PI). If present, the distal tubule in teleosts showed only weak reactions, while this segment in elasmobranchs exhibited moderate to strong enzyme activities. In the epithelial cells of the collecting tubule-collecting duct system stronger reactions were confined to the glomerular teleost species, the corresponding part of the elasmobranch kidney showing weak staining intensities. In the urinary duct system distinctly positive enzyme reactions were only to be found in the archinephric duct of the teleost species, except forPlotosus. The ureters of the elasmobranchs exhibited weak enzyme activities throughout.The enzyme patterns of the various types of urinary tubules and ducts are compared with observations from several morphological and physiological studies. The histochemical findings are discussed in relation to corresponding investigations of fresh water fishes and problems arising from phylogenetic divergence of marine fish groups.     

Potential impacts of climate change on the distributions of several common and rare freshwater fishes in Canada

Climate change will ultimately affect the supply and quality of freshwater lakes and rivers throughout the world. This study examines the potential impacts of climate change on freshwater fish distributions in Canada. Climate normals data (means from 1961 to 1990) from Environment Canada were used to map current climate found throughout the tertiary watersheds of Canada. Logistic regressions based on these climate data were used to develop predictive presence‐absence equations for (a) common commercially and recreationally important species and (b) an Arctic freshwater species and a freshwater fish species of conservation significance listed by the Committee on the Status of Endangered Wildlife (COSEWIC). The Canadian Centre for Climate Modelling and Analysis Global Coupled Model 2(IS92a) provided forecasts of Canada's climate in 2020 and 2050. The data from this scenario and the logistic regressions provided a ready framework for predicting the potential distributions of the fishes. Physical and ecological barriers would have to be overcome for the distribution of these species to actually change in response to climate change. Generally, coldwater species may be extirpated from much of their present range while cool and warm‐water species may expand northward. Species that are limited to the most southern regions of the country may expand northwards. A conceptual framework for assessing potential climate change impacts on fishes and the variety of management strategies required to deal with these impacts are discussed. Our forecasts demonstrate the need for climate change assessments in species at risk as well as for common species.     

Comparative antioxidant enzyme study in freshwater fishes. I. Distribution of superoxide dismutase, peroxide-decomposing enzymes and lipid peroxidation in herbivorous fishes

The activities of Cu,Zn-superoxide dismutase, Mn-superoxide dismutase, catalase and glutathione peroxidase were comparatively studied in organ homogenates from two herbivorous fishes, viz., the grass carp and the silver carp. 2. The protein contents and lipid peroxidation of organ homogenates were also compared. The comparative measurements primarily provide control values for subsequent toxicological examinations. 3. The highest total superoxide dismutase activities were found in the kidney, spleen and liver in the grass carp, and in the kidney and liver in the silver carp. 4. The antioxidant enzyme activities and other parameters of the organ homogenates appear to be independent of the feeding mode, but are rather characteristic of the fish variety.     

The role of pheromones in freshwater fishes

The study of fish pheromones is particularly relevant because of the conserved nature of chemoreception in vertebrates. However, most fish pheromone systems remain unstudied. All the major known pheromones of freshwater fish and their associated behaviours were reviewed. Importantly, those studies that have demonstrated the connection between behaviour and pheromones in freshwater fishes have resulted in a wide range of applications in management. For example, pheromones released by the sea lamprey Petromyzon marinus have a practical function in pheromone traps, showing how chemical communication can be used in the management of invasive species. Future research on fish pheromones should include olfactory systems in a wider range of species testing the possibility that a few distinct models could be applied to the all fishes. Progress in research on fish pheromones should include a closer collaboration with other research fields such as evolutionary biology to allow a better understanding of fish pheromones systems divergence and mate selection where correlation between phenotypic dominance and pheromone production is still largely ignored. Finally, the example of pheromone interaction between an invasive species topmouth gudgeon Pseudorasbora parva and a native endangered species sunbleak Leucaspius delineatus is provided to illustrate the concept of pheromone pollution that assists its establishment in a novel ecosystem.     

Parasitofauna of freshwater fishes in the Serbian open waters: a checklist of parasites of freshwater fishes in Serbian open waters

As a result of freshwater fish parasitofauna investigations, throughout the past 75 years, the number of parasitic species is presented. This paper reviews the history, current state, and tendencies of the fish parasitofauna studies in Serbian open waters. Up to now, in total 170 parasitic species have been reported. Systematic parasitofauna investigations have been carried out on 54 freshwater fish species in waters of the Danube River Basin in Serbia, also in hill-mountanious watercourses, lakes and salmonid fishpond of Sjenicko-Pesterska plateau (south-west region of Serbia), Homolje area (east Serbia), and in Vlasina lake (south-east Serbia). This data review pointed that it is necessary to continue the investigation on fish parasites in Serbia. The data on freshwater fish parasites are important for evaluation of general influence on the community structure.     

Biogeography of freshwater fishes of the Balkan Peninsula

Delineating biogeographical regions is a critical step towards the establishment and evaluation of conservation priorities. In the present study, we analysed the distribution patterns of the freshwater fish of an understudied European biodiversity hotspot, the Balkan Peninsula. Based on the most extensive available database of native freshwater fish species distributions, we performed a hierarchical clustering analysis to identify the major biogeographical regions of the Balkan Peninsula. We also highlighted the ‘hottest hotspots’ of freshwater fish diversity across the delimited biogeographical regions by describing the patterns of species richness, endemic and vulnerable species; indicator species were also determined. The bioregionalisation scheme consisted of eight groups of drainage basins that correspond to distinct regions of the Balkan Peninsula. Overall, the delineated biogeographical regions varied in terms of species richness, endemism, vulnerability (i.e. extinction threats) and indicator species composition. From a conservation perspective, this study emphasises the prioritisation of areas characterised by high levels of irreplaceability (endemism) and vulnerability (i.e. the Attikobeotia region, Ionian Sea and Prespa Lakes) and stresses the necessity of implementing a network of protected freshwater areas across the Balkan Peninsula.     

Reproductive ecology of Brazilian freshwater fishes

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.     

Geographical distribution of African freshwater fishes

Geographical distribution of African freshwater fishes is discussed with emphasis on the effects of major continental features, hydrographic history, and Pleistocene climatic fluctuations. Differences in the modes of dispersal and biological interactions among various categories of fishes, ecological as well as phyletic, have also had marked effects on distribution.
The African continent can be divided into ten ichthyofaunal provinces. The geography of these provinces and composition of their fish faunas is briefly described. The paper concludes with a consideration of the faunistic relationships of African lakes with endemic fishes.     

The scarcer freshwater fishes of the British Isles

This, the first of two papers on the scarcer freshwater fishes of the British Isles, gives an account of the introduced species. Nineteen species are included. The natural distribution of these fishes, the history of their introduction, their success in acclimatization, and their present distribution in the British Isles are given. A brief discussion on the introduction of exotic fishes to aquatic ecosystems follows.     

Fungi associated with the diseases of freshwater fishes

During the course of present investigations 43 isolates representing 5 genera of Saprolegniaceous fungi were isolated from 19 different species of freshwater fishes. The parasitic abilities of these isolates have been demonstrated by conducting artificial inoculation experiments under laboratory conditions using the species of Puntius and Colisa as test fishes.     

Pattern and process in the geographical ranges of freshwater fishes

North American freshwater fishes were studied to determine whether they displayed the same relationships between log (geographical range size) and log (body size) and the same pattern of range shape as found among North American birds and mammals. The forces that produce these patterns were also investigated. The log (geographical range size) : log (body size) relationship was analysed for 121 North American freshwater fish species. Thirty‐two imperilled species were compared with 89 non‐imperilled species to determine if the overall relationship could result from differential extinction. Range geometries were analysed, within and among habitat guilds, to determine if general patterns could be detected. The log (geographical range size) : log (body size) pattern among freshwater fish species was triangular and qualitatively similar to that found for North American birds and mammals. The results suggest that below a minimum geographical range, the likelihood of extinction increases dramatically for freshwater fishes and that this minimum range size increases with body size. The pattern of fish species’ range shapes differs from that found for other North American vertebrate taxa because, on average, fish possess much smaller ranges than terrestrial species and most fish species’ geographical ranges extend further on a north–south axis than on an east–west axis. The log (geographical range size) : log (body size) pattern reveals that fish species’ geographical ranges are more constrained than those of terrestrial species. The triangular relationship may be caused by differential extinction of species with large bodies and small geographical ranges as well as higher speciation rates of small‐bodied fish. The restricted geographical ranges of freshwater fishes gives them much in common with terrestrial species on oceanic islands. Range shape patterns within habitat guilds reflect guild‐specific historical and current ecological forces. The overall pattern of range shapes emerges from the combination of ecologically different subunits.