Coupled Body-Shape Variability in Perch and Roach Using the Example of Syntopic Populations from Lakes and Reservoirs with Different Relative Abundances of These Species in Fish Communities

The spread of non-native species is nowadays recognized as a major threat to the biodiversity of freshwater ecosystems. However, for a very long time the introduction and acclimatization of new species has been perceived mainly as a source of wealth for human societies. Here, we examined the establishment of non-native fish species in the Seine River basin from a historical perspective by adopting a twofold approach. In a first step, at the whole basin scale, considering various written and archeological sources, we traced the chronology, over the last millennium, of the establishments of non-native species. In a second step, by analyzing fish monitoring from several hundred sites covering the diversity of rivers and streams, we examined the changes in numbers and abundance of non-native species in local fish communities over the last three decades. The first documented species introduction dates back to the 13th century but it is from the middle of the 19th century that the introduction attempts accelerated. Today, these introductions have reached an unprecedented level and 46% of the species recorded in the basin are non-native. During the last three decades, non-native species have continued to increase within fish communities both in terms of number of species and abundance of individuals. The most pronounced increases are noted on large rivers and sites where anthropic pressures are strong. Waterways connecting European basins, globalization of trade, and ongoing climate change provide a general background suggesting that the increase in the proportion of non-native species in the fish communities of the Seine River basin is likely to continue for several decades.

On the survey of the recent records, the fish and lamprey fauna of the River Sava catchment consists of 74 species, 15 of which being considered alien. The indigenous species diversity, explained using the relation N = 0. 546 A 0.232, fits well into the range common for large catchments in Europe. Both taxonomic and ecological diversity, as well as the character of fish communities in streams and rivers, are strongly correlated with the stream order. On the relative abundance of species in fish communities, the upper rhithron fish communities cluster distinctly from those belonging to the middle rhithron, within which several subgroups of fish communities were distinguishable. Fish communities of the middle rhithron character in streams and small rivers stand distinctly apart from those belonging to particular sections of large rivers (e.g., the Rivers Sava, Drina, Vrbas, and Bosna), with the transitional type of middle rhithron fish community in larger rivers (e.g., those in the Rivers Una and Sana) that resemble more to the fish communities common in middle rhithron streams. Fish communities in the middle section of the River Sava in Croatia and in the bordering area with Bosnia and Herzegovina mainly belong to the lower rhithron, attaining the character of potamon in the most downstream, Serbian section. River Sava’s fish communities strongly interact with the ones occurring in the most downstream sections of their largest tributaries, e.g., the Rivers Una, Vrbas, Bosna, Drina, and Kolubara, which makes them very similar in structure in the areas of river mouths. Classification of fish communities based solely on the presence and absence of species revealed similar general pattern of fish community classification, though with the more sharp delimitation between those belonging to the upper and middle rhithron on one and to the lower rhithron and potamon on the other side. That was supported by the determination of fish communities belonging to the upper rhithron with brown trout Salmo cf. trutta, European bullhead Cottus gobio, and minnow Phoxinus phoxinus as the most common fish species. Fish communities belonging to the middle rhithron were determined mainly with chub Squalius cephalus and spirlin Alburnoides bipunctatus, whereas brook barbel Barbus balcanicus and stone loach Barbatula barbatula occurred in both upper rhithron and middle rhithron. Nase Chondrostoma nasus were associated with both middle and lower rhithron fish communities. The most common fish species that determine the lower rhithron fish communities were common bream Abramis brama, ide Idus idus, and bleak Alburnus alburnus, with the northern pike Esox lucius, Balon’s ruffe Gymnocephalus baloni, and racer goby Neogobius gymnotrachelus as significant species explaining fish communities of both lower rhithron and potamon. The level of production of fish in the River Sava varies remarkably within the sections with the similar ecological features, as well as between the sections that differ for the type of fish community. The greatest biomass and annual natural production were recorded in the sections homing the potamon and lower rhithron fish communities, especially in the flooding areas of side arms and oxbows which serve as spawning areas and nurseries. A total of 15 alien fish species was recorded in the River Sava catchment, the Prussian carp Carassius gibelio and brown bullhead Ameiurus nebulosus being assessed the most invasive in the areas with the potamon fish community. A strong impact from both long-term and recent stocking with alien hatchery-reared brown trout strains and rainbow trout in the upper rhithron fish communities was recently recognized. Mudminnow Umbra krameri and huchen (or Danube salmon) Hucho hucho are considered the two most threatened fish species of the River Sava catchment, where various types of riverbed modifications, especially the damming, were seen the most prominent threatening factors for fish diversity.KeywordsFish faunaLamprey faunaDiversityCommunity structureThe River Sava Basin

The fish fauna assemblage and its association with environmental factors in the waters around Zmiinyi Island in the Black Sea were examined based on biological and hydrological data collected in the period 2003–2011. The aims of the study were to identify the fish species composition and community parameters in the area, to determine the contribution of different environmental factors to seasonal variations of the fish assemblage, and to assess the Danube outflow-induced shaping of the fish species community on a seasonal time scale. A total of 58 species belonging to 35 families were collected; most were of Mediterranean origin. The most abundant species were Atherina boyeri, Aidablennius sphynx, Engraulis encrasicolus, Merlangius merlangus, Neogobius melanostomus, Sprattus sprattus and Trachurus mediterraneus. The fish community in the area studied displayed pronounced seasonal variations. Mediterranean species were the group which predominantly determined the directions of such variations and the overall community structure. Data analysis revealed temperature and salinity to be the most important factors influencing the community assemblage. Despite the substantial amount of freshwater runoff from the adjacent Danube Delta, seasonal variations in this factor did not cause significant fluctuations in fish fauna composition.

The concept of fish community as used in this chapter must not be confused with the concept of ichthyocenosis from which it is fundamentally different. We call ‘fish species community’ the possibly biased image given by the sampling of a group of fishes able to be caught in a particular environment at a given time. This definition only names a description — in the meaning of Legendre and Legendre, 1979 — of an ecological entity, but not this entity itself. This remark will be justified by the large complexity of the whole fluvio-lacustrine Chad system in the following discussion.

Keystone predator species play an important role in regulating the number, richness and distribution of prey species. Based on the bottom trawl surveys in Haizhou Bay, keystone predator species in fish communities were identified by the revised SURF (supportive role to fishery ecosystems) index. Conger myriaster, Saurida elongata, Hexagrammos otakii, Chelidonichthys spinosus, and Larimichthys polyactis were the keystone predators in the fish community. They had high number of nodes degree, and were also the main predators of many species. Further, they had strong ability of clustering. The fluctuations of their density would have great impacts on ecosystem energy flow and food web structure. The method not only considered the feeding ratio between species, but also took the amount of catch and abundance of species as important factors in the identification of keystone predators. Compared with the traditional method, this method had great improvement and provided a new one for the identification of key predators. Our results showed that the strong inter-specific interactions played an important role in maintaining the structure and function of food webs. Protection of key predators would benefit the stability of biological communities and species diversity. Therefore, ecosystem-based fisheries management (EBFM) should give priority to the protection of key species. The important economic fish species, C. myriaster and L. polyactis, should be protected with high priority as they suffered from higher fishing pressure.

Rhinogobius pflaumi is a small-sized, warm-temperate demersal fish species. It is one of the dominant species in fish community, and plays an important role in Jiaozhou Bay ecosystem. The trophic level and feeding habits of R. pflaumi were investigated by carbon and nitrogen stable isotope analysis, based on the data collected from the bottom trawl surveys during May 2011 in Jiaozhou Bay, China in this study. The results showed that the δ15N and δ13C values of R. pflaumi ranged from 11.24‰ to 13.99‰ and -20.67‰ to -18.46‰, respectively. The mean values of δ15N and δ13C were (12.70±0.70)‰ and (-19.08±0.36)‰, respectively. The mean trophic level of R. pflaumi was (3.62±0.21) for all size classes, ranging from 3.49 to 3.76 for different size classes. There was a significant negative correlation between the δ15N values and standard length, while no significant correlation was observed between δ13C values and standard length. The main prey groups of R. pflaumi were polychaeta, decapoda and mollusca. The trophic contributions of zooplankton and particle organic matter (POM) were relatively low. The similarities of prey species composition among different size classes were more than 92%, indicating that there was no significant difference in feeding habits with different standard lengths. R. pflaumi was an intermediate consumer in Jiaozhou Bay ecosystem. The significant negative correlation between trophic level and standard length might be due to variation in the proportion of different prey groups.

Changes in landscape composition caused by conversion of natural habitats into human-altered ecosystems can directly influence the physical characteristics of stream networks. Such impacts can modify the functional structure of fish communities, although the exact consequences of anthropic land-use changes can be context-dependent. This study investigated the influence of different land-use classes on the functional structure of fish communities in 32 headwater streams from southern Brazil. Trait composition and indices of functional diversity of the fish community were related to four land-use classes: native forest vegetation, silviculture, agriculture, and urban areas. Streams surrounded by larger areas of native forest were characterized by the predominance of foraging specialist species like grazers. However, as native vegetation is replaced by agriculture and urban areas, specialist species are replaced by species with generalist diet like detritivores. In streams surrounded by larger areas of agriculture, functional richness and divergence increased, while functional evenness decreased. Most likely, these changes were induced by alterations in the water quality, indicated by increased electrical conductivity and water temperature in streams with more agriculture areas. In conclusion, the conservation of the native forest vegetation is essential to maintain habitat characteristics and ecological processes in streams and to avoid the loss of specialist species in fish communities.

In Lithuania brown trout (Salmo trutta L.) is the dominant species in fish communities of cold-water streams. We documented a variation in food consumption and prey selection by age-0 brown trout (...

Natural perturbations and human pressure increasingly affect the river ecosystems and their biological communities. Fish species are a good indicator of the river status and one of the factors for the assessment of ecological condition by the Water Framework Directive (Directive 2000/60/EC). River Mirna, one of the larger right tributaries of the river Sava, is a good example of anthropogenic pressure on the running water ecosystem. Fish community species structure was analyzed at selected eight sampling sites located over the 28 km length of the river. Abiotic conditions were determined by measuring the physical, chemical and hydro-morphological parameters and the influence of measured parameters on present fish community was analyzed. It has been determined, that the river Mirna is loaded with organic matter and physically changed by regulations, river beds canalizing and bank stabilization. Fish were sampled with standard electro-fishing method to determine species diversity, biomass of the specimens and their size. 29 fish species from seven families (26 native and 3 allochthonous species) were recorded along with one type of the Danubian brook lam- prey (Eudontomyzon vladykovi). Only two species, Telestes souffia and Cottus gobio, were present at all eight sampling sites. The largest number of specimens (890) and the largest biomass (5697 g) per 100 m2 was recorded at the sampling site located after the town as a result of the flow of purified water from the water treatment plant and a large number of invertebrates,which are an important food source. The minimum number of specimens per 100 m2 (86) and the minimum biomass of fish per 100 m2 (457 g) was measured at the relatively natural part of the channel. The most common causes for this are low temperatures, less food and a fast, turbulent flow. The study confirms that the changes in abiotic factors induced by anthropogenic activities significantly influence the structure of fish species community.

Many coral reef fish species use mangrove and seagrass beds as nursery areas. However, in certain regions, the absence or scarcity of such habitats suggests that juvenile coral reef fish may be seeking refuge elsewhere. The underlying biogenic substratum of most coral reefs is structurally complex and provides many types of refuge. However, on young or subtropical coral reefs, species may be more reliant on the living coral layer as nursery areas. Such is the case on the high-latitude coral reefs of South Africa where the coral communities consist of a thin veneer of coral overlaying late Pleistocene bedrock. Thus, the morphology of coral species may be a major determinant in the availability of refuge space. Acropora austera is a branching species that forms large patches with high structural complexity. Associated with these patches is a diverse community of fish species, particularly juveniles. Over the past decade, several large (>100 m2) A. austera patches at Sodwana Bay have been diminishing for unknown reasons and there is little evidence of their replacement or regrowth. Seven patches of A. austera (AP) and non-A. austera (NAP) were selected and monitored for 12 months using visual surveys to investigate the importance of AP as refugia and nursery areas. There were significant differences in fish communities between AP and NAP habitats. In total, 110 species were recorded within the patches compared to 101 species outside the patches. Labrids and pomacentrids were the dominant species in the AP habitats, while juvenile scarids, acanthurids, chaetodons and serranids were also abundant. The diversity and abundance of fish species increased significantly with AP size. As the most structurally complex coral species on the reefs, the loss of APs may have significant implications for the recruitment and survival of certain fish species.

Objective. Fish species community structure and benthic organisms coverage were studied in five localities in Santa Marta where the lionfish is present. Materials and methods. Abundance of fish species, including lion fish, was established using 30 m random visual censuses and video transects; trophic guilds were established according to available references. On the other hand benthic coverage was evaluated using the software Coral Point Count (CPCe) 4.0. Results. Families with higher species numbers were Serranidae, Labridae, and Pomacentridae. Lionfish abundances were low (2.6±2.1 ind/120 m2), but in any case Pterois volitans was observed as the eleventh more abundant species, surpassing species of commercial value such as Cephalopholis cruentata. Species that were found in larger numbers (>100, Thalassoma bifasciatum, Haemulon aurolineatum, Canthigaster rostrata, Abudefduf saxatilis, Chromis cyanea, and Stegastes partitus) were mainly invertebrate eaters, planctivores, and territorial herbivores. Coral coverage showed higher coral percentages in Chengue (69.9%) and Cinto (27.4%), larger sponge percentages in Morro (32.7%); Isla Aguja and Remanso showed the larger figures for abiotic substrate (41.6 and 37%, respectively); corals, sponges, and gorgonians were the components best explaining fish community, but not for the lion fish, which inhabit all studied reef formations. Conclusions. Lion fish is ranked between the 20 more abundant species, with none commercially important species larger, hence no species may qualify as a natural control. Lion fish has as well become a relatively abundant species in Santa Marta reefs, independent of benthic coverage.