Aminotransferases in early development of salmonid fish

The activities of alanine and aspartate aminotransferases were assessed in the embryos and juveniles of the rainbow trout Parasalmo mykiss L. and chum salmon Oncorhynchus keta W. Changes in subcellular localization of these enzymes and their activities were found at different pH optima in each subcellular fraction of the rainbow trout during ontogenesis.__________Translated from Ontogenez, Vol. 36, No. 2, 2005, pp. 96–101.Original Russian Text Copyright © 2005 by Samsonova, Lapteva, Filippovich.     

Habitat use of the European mudminnow Umbra krameri and association with other fish species in a disconnected Danube side arm

Fish assemblages along the longitudinal course of an old, disconnected and modified side arm of the Danube floodplain downstream of Vienna, Austria, as well as habitat structure, hydro‐morphological and hydro‐chemical factors, were investigated in order to analyse the key environmental determinants of the European mudminnow Umbra krameri. Generally, U. krameri was the most abundant species in the system. It occurred in disconnected ditches, ponds and pools with dense reed belts and comparatively low nutrient content, indicating its natural association with marsh habitats. At infrequently disturbed sites it was associated with a small group of stagnophilious and highly specialized species with adaptations to strong oxygen fluctuations. At frequently flooded sites, the species was absent or occurred in low abundances, indicating its adaptation to water bodies in older successional stages and its low competitive power in permanently connected floodplain habitats.     

Relationships between life-history strategies of European freshwater fish species and their habitat preferences

1. Focusing on the current environmental characteristics, the ‘habitat template’ theory proposes that life‐history strategies summarise how evolution has shaped species to cope with the temporal and spatial variability of their present environment. The hierarchical ‘landscape filters’ concept predicts that the distribution of species reflects their specific traits that allow them to pass through multiple habitat filters. Together, these theories showed the importance of identifying the functional relationships of species to selective habitat forces in order to predict the organisation and response of communities to the environment. 2. We test the relationships between life‐history traits of European freshwater fish species’ and their habitat preferences, to detect the strategies adopted by fish to cope with their current habitat. For this purpose, we use published data on species traits and habitat preferences (microhabitat hydraulics, temperature and oxygen level). We use multivariate analyses to classify fish species’ strategies and test the relationships between strategies and habitat preferences. 3. We identified a continuum of life‐history patterns between two extremes, with opportunistic and periodic species. Our study supports the idea that microhabitat hydraulics plays a more important role as a template for these species ecological strategies than temperature and oxygen level. Indeed, riffle habitats may select opportunistic species whereas weak relationships are found between species strategies and both their temperature and oxygen level preferences. In addition, the ratio between mortality and growth rate (dimensionless trait), reflecting a trade‐off between growth and survival, varied among species according to the use of their hydraulic habitat, with species using deep habitats exhibiting the highest values. 4. These general relationships between hydraulics and traits may be of importance in community ecology to develop predictive models to understand how fish communities change with the hydraulic environment.     

The structure and components of European estuarine fish assemblages

This paper discusses the structure of fish assemblages using information from 17 European estuarine areas (in the British Isles, Portugal, Belgium, France, the Netherlands, Germany, Norway and Spain). Binary (presence/absence) and quantitative data for each assemblage have been used to assess the assemblage structure according to taxonomy (i.e. species identity). Following this, a total of 29 functional guilds were created in order to describe the use made of an estuarine area for each taxon encountered: feeding preferences, reproduction type, substratum preferences (for bottom dwelling fish) and position within the water column (vertical preference guild). The paper focuses on the designation and determination of the proportions of the guild members of the fish assemblage within each estuary. Ecological guilds within the assemblage include estuarine residents, marine juvenile migrants, catadromous and anadromous migrants, marine seasonal users, and freshwater and marine adventitious species. Feeding guilds include detritivores, planktonic feeders, infaunal croppers and sediment ingesters, piscivores, and active predators of mobile crustaceans. Reproduction guilds include planktonic and demersal spawners and those using brood-protection. The substratum preference indicates the proportions of sand, mud, rock and vegetation dwellers, and the vertical preference denotes benthic, demersal or pelagic species. The analysis has allowed both the estuaries to be grouped according to taxonomic and guild similarity and the characterisation of a typical European estuarine fish assemblage. Within the limits posed by differing sampling methods, times of sampling and survey rationale, there is a high similarity between estuaries. The data indicate common patterns of estuarine usage irrespective of the differences between the estuaries although such patterns cannot be interpreted fully given the incomplete knowledge of their physical and anthropogenic characteristics.     

Review: Assessing fish welfare in research and aquaculture,with a focus on European directives

The number of farmed fish in the world has increased considerably. Aquaculture is a growing industry that will in the future provide a large portion of fishery products. Moreover, in recent years, the number of teleost fish used as animal models for scientific research in both biomedical and ecological fields has increased. Therefore, it is increasingly important to implement measures designed to enhance the welfare of these animals. Currently, a number of European rules exist as requirements for the establishment, care and accommodation of fish maintained for human purposes. As far as (teleost) fish are concerned, the fact that the number of extant species is much greater than that of all other vertebrates must be considered. Of further importance is that each species has its own specific physical and chemical requirements. These factors make it difficult to provide generalized recommendations or requirements for all fish species. An adequate knowledge is required of the physiology and ecology of each species bred. This paper integrates and discusses, in a single synthesis, the current issues related to fish welfare, considering that teleosts are target species for both aquaculture and experimental models in biological and biomedical research. We first focus on the practical aspects, which must be considered when assessing fish welfare in both research and aquaculture contexts. Next, we address husbandry and the care of fish housed in research laboratories and aquaculture facilities in relation to their physiological and behavioural requirements, as well as in reference to the suggestions provided by European regulations. Finally, to evaluate precisely which parameters described by Directive 2010/63/EU are reported in scientific papers, we analysed 82 articles published by European researchers in 2014 and 2015. This review found that there is a general lack of information related to the optimal environmental conditions that should be provided for the range of species covered by this directive.     

Environmental DNA metabarcoding provides enhanced detection of the European eel Anguilla anguilla and fish community structure in pumped river catchments

The European eel Anguilla anguilla (eel hereafter) is critically endangered and has a catadromous life cycle, which means adult eels that live in pumped catchments must pass through pumps during their downstream spawning migration. Policy makers are currently lacking detailed site-by-site eel distribution information to estimate the overall impact of individual pumping stations on eel escapement, and as such lack the data to enable informed prioritisation of pumping station management and targeted mitigation. This study investigated whether environmental DNA (eDNA) metabarcoding can provide increased detection sensitivity for eel and fish community structure in highly regulated pumped catchments, when compared directly to current standard practice fish survey protocols (seine netting/electric fishing). Eels were detected in 14 of 17 sites (82.4%) using eDNA metabarcoding in contrast to 3 of 17 sites (17.6%) using traditional catch methods. In addition, when using eDNA monitoring, species richness was higher in 16 of 17 sites (94.1%), and site occupancy was greater than or equal to traditional methods for 23 of 26 of the fish species detected (88.5%). Although eDNA methods presented significantly higher average species richness and species site occupancy overall, eDNA and catch methods were positively correlated in terms of species richness and site occupancy. It was therefore found that eDNA metabarcoding was a high-sensitivity method for detecting eels in pumped catchments while also increasing the detection of overall fish community structure compared to traditional catch methods. In addition, this study highlights how eDNA monitoring is especially suited to increase the detection of particular species, with traditional methods sufficient for others. This high sensitivity, coupled with the ability to sample multiple sites in a short time frame, suggests that eDNA metabarcoding workflows could be invaluable tools when prioritising pumping station management.     

Measurements of salmonid population performance in relation to habitat in eastern Newfoundland streams

The density, biomass and estimated production of brook trout Salvelinus fontinalis and Atlantic salmon Salmo salar were related to habitat factors in streams of Terra Nova National Park, Newfoundland, Canada. Fish communities at 29 sites (18 brooks; 15 watersheds) were sampled in the summer of 2002, 2003 and 2005. Salmonid density, biomass per unit area and production (derived from biomass and fish size using allometric P:B relationships) were compared with site habitat characteristics (wetted width, lactustrine habitat, per cent riffle habitat, canopy coverage and stream gradient), using an interactive stepwise multiple linear regression. Salmonid biomass (mean: 2·87 g m^?2; range: 0·33–10·88 g m^?2) and estimated production (mean: 3·05 g m^?2 year^?1; range: 0·32–10·98 g m^?2 year^?1) within the study area varied by an order of magnitude, however, habitat variables accounted for much of this variation. Specifically, wetted width and lacustrine area of the tributary played important roles in explaining density, biomass and production. Wetted width was important for all measurements of brook trout and total salmonids while lacustrine area was important for all measurements of Atlantic salmon and played a lesser role in total salmonid biomass. Other factors such as the percentage of riffle habitat, site gradient and canopy coverage provided modest improvements to the fit of some relationships. When models using the same environmental factors were compared, those using production estimates derived from allometric P:B equations in the literature provided improved predictive capability than did those from direct density and biomass estimates. It is proposed that allometric P:B relationships have utility in improving comparisons of stream fish communities, particularly in studies with insufficient resources to measure production directly.     

Effects of riparian canopy cover on salmonid diet and prey selectivity in low nutrient streams

This study focuses on stream sections within a relatively low nutrient catchment in south‐east Ireland in an attempt to characterize the probable effects of riparian canopy on salmonid diet and prey selectivity within two size classes of nursery stream. Sampling found that brown trout Salmo trutta diet changed significantly in response to riparian canopy regardless of stream size. The observation that S. trutta within unshaded stream sites did not feed on drifting terrestrial prey items to the same extent as those within shaded streams was not due to a lack of availability of this food source. There was no evidence to suggest that S. trutta selectively choose particular prey items.     

Environmental DNA phylogeography: Successful reconstruction of phylogeographic patterns of multiple fish species from cups of water

Phylogeography is an integrative field of science linking micro- and macro-evolutionary processes, contributing to the inference of vicariance, dispersal, speciation, and other population-level processes. Phylogeographic surveys usually require considerable effort and time to obtain numerous samples from many geographical sites covering the distribution range of target species; this associated high cost limits their application. Recently, environmental DNA (eDNA) analysis has been useful not only for detecting species but also for assessing genetic diversity; hence, there has been growing interest in its application to phylogeography. As the first step of eDNA-based phylogeography, we examined (1) data screening procedures suitable for phylogeography and (2) whether the results obtained from eDNA analysis accurately reflect known phylogeographic patterns. For these purposes, we performed quantitative eDNA metabarcoding using group-specific primer sets in five freshwater fish species belonging to two taxonomic groups from a total of 94 water samples collected from western Japan. As a result, three-step data screening based on the DNA copy number of each haplotype detected successfully eliminated suspected false positive haplotypes. Furthermore, eDNA analysis could almost perfectly reconstruct the phylogenetic and phylogeographic patterns obtained for all target species with the conventional method. Despite existing limitations and future challenges, eDNA-based phylogeography can significantly reduce survey time and effort and is applicable for simultaneous analysis of multiple species in single water samples. eDNA-based phylogeography has the potential to revolutionize phylogeography.     

Large-scale intraspecific variation in life-history traits of European freshwater fish

Aims To test the magnitude and direction of the effects of large‐scale environmental factors (latitude and habitat type: lotic or lentic) on the intraspecific variations in multiple life‐history traits, across multiple European freshwater fish species. To test the relevance of defining species traits by quantifying the magnitude of interspecific vs. intraspecific variability in traits. Location Europe. Methods We obtained estimates of 11 fish traits from published sources for 1089 populations of 25 European freshwater fish species. Traits were: longevity, maximal length, growth rate, asymptotic length, mortality rate, age and length at maturation, fecundity, egg size, gonadosomatic index, and length of breeding season. We described population habitats by latitude and habitat type (lotic or lentic), when available. For each species we tested the combined effect of latitude and habitat type on the intraspecific variation of each trait using analysis of covariance (ancova ). We compared the intraspecific variation in traits with the variation between species using an analysis of variance (anova ) for each trait, all species pooled. Results We found a consistent effect in direction of latitude on six traits, but we showed that this effect is not always significant across species. Higher‐latitude populations often grew more slowly, matured later, had a longer life span and a higher maximal and asymptotic length, and allocated more energy to reproduction than populations at lower latitudes. By contrast, we noted only a slight effect of habitat type on the intraspecific variation in traits, except for Salmo trutta. All traits varied significantly between species. However, traits such as growth rate, mortality rate and length of breeding season varied more between populations than between species, whereas fecundity and traits associated with body length varied more between species. Main conclusions Latitude, in contrast to habitat type, is an important factor influencing several traits of geographically widely dispersed populations of multiple European freshwater fish species. Species traits that vary more between species than between populations are attractive variables for understanding and predicting the responses of stream fish communities to their environment.     

Partitioning the diversity of riverine fish: the roles of habitat types and non-native species

1. Quantifying how biological diversity is distributed in the landscape is one of the central themes of conservation ecology. For this purpose, landscape classifications are being intensively used in conservation planning and biodiversity management, although there is still little information about their efficacy. 2. I used data from 158 running water sites in Hungary to examine the contribution of six a priori established habitat types to regional level diversity of fish assemblages. Three community measures [species richness, diversity (Shannon, Simpson indices), assemblage composition] were examined at two assemblage levels (entire assemblage, the native assemblage). The relative role of non‐native species was quantified to examine their contribution to patterns in diversity in this strongly human influenced landscape. 3. Additive diversity partitioning revealed the primary importance of beta diversity (i.e. among‐site factors) to patterns in species richness. Landscape‐scale patterns in species richness were best explained by between‐habitat type (beta₂: 41.2%), followed by within‐habitat type (beta₁: 37.7%) and finally within‐site (alpha: 21.1%) diversity. Diversity indices showed patterns different from species richness, indicating the importance of relative abundance distributions on the results. Exclusion of non‐natives from the analysis gave similar results to the entire‐assemblage level analysis. 4. Canonical analysis of principal coordinates, complemented with indicator species analysis justified the separation of fish assemblages among the habitat types, although classification error was high. Multivariate dispersion, a measure of compositional beta diversity, showed significant differences among the habitat types. Contrary to species diversity (i.e. richness, diversity indices), patterns in compositional diversity were strongly influenced by the exclusion of non‐natives from the analyses. 5. This study is the first to quantify how running water habitat types contribute to fish diversity at the landscape scale and how non‐native species influence this pattern. These results on riverine fish assemblages support the hypothesis that environmental variability (i.e. the diversity of habitat types) is an indication of biodiversity and can be used in large‐scale conservation designs. The study emphasises the joint application of additive diversity partitioning and multivariate statistics when exploring the contribution of landscape components to the overall biodiversity of the landscape mosaic.     

A realignment of marine biogeographic provinces with particular reference to fish distributions

Marine provinces, founded on contrasting floras or faunas, have been recognized for more than 150 years but were not consistently defined by endemism until 1974. At that time, provinces were based on at least a 10% endemism and nested within biogeographic regions that covered large geographic areas with contrasting biotic characteristics. Over time, some minor adjustments were made but the overall arrangement remained essentially unaltered. In many provinces, data on endemism were still not available, or were available only for the most widely studied vertebrates (fishes), a problem that is ongoing. In this report we propose a realignment for three reasons. First, recent works have provided new information to modify or redefine the various divisions and to describe new ones, including the Mid‐Atlantic Ridge, Southern Ocean, Tropical East Pacific and Northeast Pacific. Second, phylogeographic studies have demonstrated genetic subdivisions within and between species that generally corroborated provinces based on taxonomic partitions, with a notable exception at the Indian–Pacific oceanic boundary. Third, the original separation of the warm‐temperate provinces from the adjoining tropical ones has distracted from their close phylogenetic relationships. Here we propose uniting warm‐temperate and tropical regions into a single warm region within each ocean basin, while still recognizing provinces within the warm‐temperate and tropical zones. These biogeographic subdivisions are based primarily on fish distribution but utilize other marine groups for comparison. They are intended to demonstrate the evolutionary relationships of the living marine biota, and to serve as a framework for the establishment of smaller ecological units in a conservation context.     

Heavy metals in Lake George, Uganda, with relation to metal concentrations in tissues of common fish species

The northern end of Lake George, Uganda, and its associated wetlands receive localized metal pollution from a former copper mine and tailings left after metal extraction. The aim of this study was to determine (i) whether the heavy metals are a threat to the biology of the major commercial fish species and (ii) whether consumption of the fish threatens human health. Concentrations of copper, zinc, cobalt and nickel in detrital sediments, plankton, and five fish species from sites in Lake George, the Kazinga Channel and Lake Edward (which are inter-connected) were determined using atomic absorption spectroscopy. The detrital sediments of Hamukungu Bay, Lake George, had average concentrations (g/g dry weight) of 96.3 zinc, 270.4 copper, 57.4 cobalt and 42.8 nickel. There were no significant differences between the Hamukungu Bay and the North Lake George site of Bushatu: both receive inflows from the mining activities. Concentrations of copper and zinc were significantly higher than background values from unpolluted freshwater ecosystems. Plankton samples showed a metal concentration gradient consistent with a gradient from the source of pollution in northern Lake George, along the Kazinga Channel to Lake Edward. The liver tissues of fish had markedly higher concentrations of copper and zinc than flesh. Concentrations of cobalt and nickel were relatively low. The highest mean concentrations of metals in liver tissue occurred in Oreochromis leucostictus (189.0 g/g Cu) and Bagrus docmac (187.5 g/g Zn) whilst the lowest occurred in Oreochromis niloticus (15.3 g/g and 78.2 g/g dry weight copper and zinc, respectively). However, O. niloticus contained the highest concentrations of cobalt (11.2 g/g) and nickel (3.8 g/g). Liver Somatic Indices (LSI) of the fish species from the different sites indicated a reduction of LSI in those fish from the most contaminated zones of northern Lake George compared with all other sites. This suggests there could be anatomical and physiological abnormalities linked to the heavy metal pollution. The flesh had only low concentrations of metals; well within international guidelines for consumption. A person would have to consume 9 kg of fresh flesh of Clarias sp. and 65 kg of O. leucostictus daily to exceed the WHO recommended intake for copper, and even more for other metals. This implies that currently metal pollution in Lake George presents an ecological rather than a human health concern.     

Comparison of the physical properties of real and artificial salmonid eggs and of their performance when drifting in an experimental stream channel

The paper compares three batches of brown trout (Salmo trutta Linnaeus) eggs, two batches of Atlantic salmon (Salmo salar Linnaeus) eggs and the artificial trout eggs described by Ottaway (1981), in terms of their measurable physical characteristics. Attention was given to the effects of temperature and of the stage of development of the real eggs. Comparisons were also made between brown trout eggs and artificial eggs of the rate of fall in a water column, of the value and speed of attainment of terminal velocity when falling through water and of the pattern of settlement within an experimental stream channel.The main measurable characteristics of brown trout eggs (after water hardening) and of artificial eggs (values in parentheses) were: diameter 0.52–0.54 mm (0.54), fresh weight 0.078–0.086 g (0.09), density 1.071–1.075 g ml^–1 (1.066), and volume 0.073–0.081 ml (0.085). There was no evidence of any major change in these values as egg development proceeded. Salmon eggs had a similar density to trout and artificial eggs but had 30 to 70% greater weight and volume. The water-hardening of eggs caused their dry matter content to fall from 37–39% to 31–34% and there were corresponding increases in volume and fresh weight.The rate of fall of trout eggs and artificial eggs through water when timed from rest at the water surface to a depth of 125 cm was similar for both types of egg at 10 °C. This rate rose with increasing temperature at the same low rate of c. 0.02 cm s^–1 °C^–1 for both types of egg. Both types of egg had a terminal velocity of c. 8.8 cm s^–1 and both achieved terminal velocity in less than 1.5 s after release.The patterns of settlement of the two types of eggs in an experimental channel were similar.     

Patterns in species richness and endemism of European freshwater fish

Aim  To analyse the patterns in species richness and endemism of the native European riverine fish fauna, in the light of the Messinian salinity crisis and the Last Glacial Maximum (LGM).
Location  European continent.
Methods  After gathering native fish faunistic lists of 406 hydrographical networks, we defined large biogeographical regions with homogenous fish fauna, based on a hierarchical cluster analysis. Then we analysed and compared the patterns in species richness and endemism among these regions, as well as species–area relationships.
Results  Among the 233 native species present in the data set, the Cyprinidae family was strongly dominant (> 50% of the total number of species). Seven biogeographical regions were defined: Western Peri-Mediterranea, Central Peri-Mediterranea, Eastern Peri-Mediterranea, Ponto-Caspian Europe, Northern Europe, Central Europe and Western Europe. The highest regional species richness was observed for Central Peri-Mediterranea and Ponto-Caspian Europe. The highest endemic richness was found in Central Peri-Mediterranea. Species–area relationships were characterized by high slope values for Peri-Mediterranean Europe and low values for Central and Western Europe.
Main conclusions  The results were in agreement with the 'Lago Mare' hypothesis explaining the specificity of Peri-Mediterranean fish fauna, as well as with the history of recolonization of Central and Western Europe from Ponto-Caspian Europe following the LGM. The results also agreed with the mechanisms of speciation and extinction influencing fish diversity in hydrographical networks. We advise the use of the seven biogeographical regions for further studies, and suggest considering Peri-Mediterranean Europe and Ponto-Caspian Europe as 'biodiversity hotspots' for European riverine fish.