Fish Community Structure on a Deep Ocean Outfall,Barber's Point,Oahu, Hawaii

The Barber's Point, Oahu, Hawaii sewer outfall structure attracts large numbers of fish (500 — 1000 per 336 m² bottom area) and fish species (23—29) not normally seen over flat, soft bottoms characteristic of the diffuser (66 m) isobath. Except for fish species strictly associated with corals, the adult fish community parameters (species richness, abundance, and composition) were similar to shallower natural Hawaiian reef environments. The adult fish species composition at the diffuser changed significantly during the discharge of heavy flocculated pre-treated sewage (15 mgd). High rates (15 mgd) of pre-treated sewage may cause decreases in total fish abundance and species richness when compared with the discharge of primary effluent with little or no flocculation between 0 and 19 mgd. Two fish species, which were generally abundant in Hawaiian waters during the years of observation, were absent at the outfall during discharge of heavy flocculated pre-treated effluent.     

Fish impingement at power stations situated along the rivers Rhine and Meuse in The Netherlands

Summary Substantial numbers of predominantly O⁺ fish were impinged on the cooling water screens of Harculo, Gelderland, Merwedehaven and Amer power stations. Low numbers were impinged at the two stations located on the river Meuse (Maas and Claus). Two possible reasons for this difference are suggested,viz. a low fish density in the river Meuse and the deep position of the cooling water intakes. In comparison with Bergum power station situated on a lake the impingement rate at the river stations was more than ten times as low.Most fish were impinged during the summer months when large numbers of juvenile fish are present in the rivers. Dominating species impinged were roach, pikeperch, bream and perch. The abundance of pikeperch in the screensamples, points to a recent increase in the population of pikeperch in the rivers. The growth pattern of O⁺ pikeperch and O⁺ roach during summer seemed very similar for power stations located at different rivers. Thirty fish species and four crustacean species were collected, among whichOrconectus limosus was quite abundant at Maas and Claus power stations.     

Annual and non-annual fish assemblages respond differently to environmental and spatiotemporal variations of temporary wetlands from southern Brazil

• The fish community of temporary wetlands is highly dynamic due to the marked seasonal changes in hydrological and limnological conditions. In this study, we evaluated spatiotemporal variation in the fish community and the influence of environmental factors on this variation in temporary wetlands in southern Brazil.
• Two different life cycles—annual and non-annual fishes—were recorded among species. Variation in the fish community appeared to be associated with differences in the life history strategy of species. While species of annual fish were present throughout the hydroperiod, gradually decreasing in density over time, non-annual fish species had an opposite pattern, with higher densities in the final phase of the hydrological cycle.
• Variations in the composition and abundance of fish community in temporary wetlands were related to habitat and landscape attributes (area, number of microhabitats and isolation between temporary wetlands) and climate indicators of water availability (air temperature, average rainfall, and water level of the São Gonçalo channel), but not to water conditions (dissolved oxygen, pH, conductivity and water temperature).
• We concluded that the ichthyofauna of temporary wetlands are composed both of rare species, highly specialised for life within these ephemeral environments, and widespread generalist species that reach the wetlands opportunistically for short periods. Habitat and landscape attributes and changes in climate and hydrological variables over the hydroperiod are the factors that had the greatest influence on spatiotemporal variation of the fish community.
• Maintaining physical characteristics and the hydrological cycle of temporary wetlands is critical for the conservation of fish species inhabiting these vulnerable environments in southern Brazil. Habitat and landscape attributes and climate and hydrology fluctuations affect the annual and non-annual fishes inhabiting temporary wetlands differently.

     

Circadian-rhythmic variations of biochemical parameters in the yearlings of indigenous perch (Perca fluviatilis L.) and nonindigenous tyulka (Clupeonella cultriventris Nordmann) from the Rybinsk Reservoir (Russia)

Diurnal variations of some parameters of protein, lipid, and water metabolisms in the underyearlings of indigenous (perch, Perca fluviatilis L.) and nonindigenous (tyulka, Clupeonella cultriventris Nordmann) fish species have been analyzed. These species form the basis of feeding aggregations of young fish in the Rybinsk Reservoir pelagial. No significant daily fluctuations in the values of protein content, water, and lipids in the studied fish species were revealed. Stable interspecific differences in mean daily and hourly values of the above-mentioned components, as well as in the contents of three lipid fractions—phospholipids (PLs), free cholesterol (FC), and triacylglycerols (TAGs)—have been determined at the level of whole organism. It is shown that the level of adipose reserves and the content of TAG in the tyulka are higher than in perch, while the contents of proteins, PL, and FC are lower. Diurnal variations of the level of each of the three fractions in both fish species are similar, but the ranges of variations are wider in tyulka than in perch. Possible mechanisms for the regulation of lipid metabolism and their similarity in young fish of different species upon adaptation to short-term changes in the environment are discussed. It is suggested that the modern state of the zooplankton community in the Rybinsk Reservoir pelagial negatively affects the feeding of perch underyearlings and parameters of lipid metabolism in their organisms.     

Presence of cyclic betaines in fish

The distribution of cyclic betaines were examined comparatively in several organs of 10 species of fish. The distribution of homarine depended on the organs and fish: high levels in gonads, and medium levels in digestive contents and digestive organs were found in Clupeidae and Engraulidae. Homarine was also present in undetected or small amounts in the remaining five species belonging to Plecoglossidae, Scomberesocidae, Carangidae, Sciaenidae and Monacanthidae. Trigonelline and N-methyl isonicotinic acid—isomers of homarine—were scarcely found. Homarine content in fish was not closely related to their food.     

The fish fauna of the Jordan reservoir, one of the oldest man-made lakes in central Europe

The Jordan reservoir, Czechoslovakia, was constructed in 1492 and the last full drainage and fish removal was in 1830. In this 'mature' fish community of 20 species (plus three hybrids), the roach, Rutilus rutilus (L.) (1446 fish ha^–1) and beam, Abramis brama (L.) (1074 fish ha^–1) dominated the fish stock (total of all species = 3628 fish ha^–1). Predatory species made a small contribution to the total (maximum 7.7%, obligatory predators 2%). The contribution (12%) by perch, Perca fluviatilis L., was also low, and its numbers in successive age-groups showed a steady decrease. The high variability and time-synchronization in the year-class strengths of the principal cyprinid species may indicate unstable environmental conditions or intra-community cycles. The growth rates of non-predatory species were low. There was a high fishing rate on predatory species but there was little impact by fishery management on the whole 'mature' community. Intensive eutrophication from both communal waters and agriculture probably caused the high biomass level (all species) and the low abundance of zander, Stizostedion lucioperca (L.).     

Fish populations of lentic environments of the Paraná River

Data on the fish populations of lentic water bodies in the Paraná River are given for different areas sampled over more than twenty years. Three kinds of environment are considered: small, medium and large lagoons. Each kind has a particular fish population, the characteristics of which are described. Fish populations are also considered in relation to the macrophytes along the Paraná River. In general Prochilodus lineatus is the most important species, both in numbers and in biomass, in the majority of the lagoons. Considerations related to size and age of fish species are also discussed.     

Modification of the response to high density conditions in the guppy, Poecilia reticulata (Peters)

An examination was made of some of the factors which influence the response to density in the guppy. Water from high density fish was given to fish populations kept at high and low densities. This induced high density behaviour in low density fish by increasing aggression and decreasing courtship. But giving 'fresh' water to high density fish failed to alleviate the response to density. 'High density water' slightly reduced the numbers of young found in low density groups. High density fish kept in the dark had more young than high density groups in the light; and the number of young found was decreased when 'high density water' was given to low density fish. The number of ovarian stages was decreased in the dark in high density and was not overridden by the type of water. Giving 'high density water' to low density fish decreased the number of oocytes stage III, but the interaction between water and 'light' was confounded by the total numbers of ovarian stages. Increasing the 'visual space' of high density fish with mirrors partially decreased aggression and increased courtship and number of young found; but had little affect upon the number of ovarian stages. Decreasing the number of physical contacts by keeping the fish chronically tranquillized reduced the activity of the fish. This reduced the aggression of the high density fish and also reduced the differences between the high and low density fish on the basis of their courtship scores, number of young found and number of stages in the ovary. Fish from differing population sizes were given a choice between varying fish densities. The fish from a 'normal' sized population and with an extended visual field, tended to make a choice conforming to the overall selections compared with fish from populations of extreme size and with a reduced visual field.     

The state of the reproductive system of several fish species from water bodies polluted with radionuclides during the Chernobyl catastrophe

The state of the reproductive system in several fish species—offspring of individuals exposed to radiation as a result of the catastrophe at the Chernobyl Nuclear Power Plant (CNPP) was studied. Material was collected in water bodies of Ukraine polluted with radionuclides: water cooler of the CNPP (1992, 2002–2004), Lake Glubokoe (2003–2004), Kiev Reservoir, and Teterev River (1997, 1999–2005). It was shown that the total number and the degree of disturbances in gonads of the studied fish species were positively correlated with the levels of pollution of water bodies: in the cleanest water body, Teterev River, the proportion of fish with gonads without considerable deviations was about 78%; in the Kiev Reservoir, 67%; in the water cooler, 51%; and in Lake Glubokoe, 45%. By the number and pattern of gonad anomalies, species specificity in their response to the radiation background was revealed. A smaller degree of damage of sexual cells and gonads in unisexual (triploid) populations of goldfish Carassius auratus reproducing gynogenetically, as compared to bisexual (diploid) populations, was detected. Among postemergency generations of the studied fish species, in all water bodies the number and degree of gonad disturbances were in F_2–4, in Kiev Reservoir and Teterev River, this was most likely accounted for by the phenomenon of prolonged mutagenesis.     

Results of the introduction of Coregonids to Lake Vashozero

The results of the introduction of coregonids—the whitefish Coregonus lavaretus and the European cisco C. albula—to Lake Vashozero are considered. It is shown that a positive result was obtained from the introduction of the European cisco; it has naturalized in the lake and successfully reproduces. The biology of the European cisco in a water body new for it was studied, and it was compared to its initial form from Onega Lake. The structure of trophic relations in the water body has changed with the introduction of the European cisco. Previously there was one flow of matter and energy in the lake: benthos—benthophagous fish—carnivorous fish. Now, however, another flow has been added: plankton—European cisco—carnivorous fish.     

The icthyofauna of the Mhlathuze coastal lakes: some preliminary results

The fish faunas of the four Mhlathuze coastal lakes and the lower river comprise a diverse assortment of over fifty marine, estuarine and freshwater species. Three freshwater species are endemic to KwaZulu-Natal and nine estuarine species are endemic to southern Africa. Five species are of conservation significance. Species numbers in Lakes Mzingazi and Cubhu are similar historically and both lakes served as secondary nursery habitats for estuarine associated fishes. This role has been impacted by the construction of weirs at their outlets which prevent successful recruitment of estuarine species, especially during drought years when lake water levels are low. The fish faunas of Lakes Nsezi and Mangeza are depauperate and lack marine or estuarine components. In order that these systems fulfil their potential function as secondary nursery habitats to many estuarine fish species, minimum lake water levels must be set to ensure sufficient outflows at proposed fish ladders during critical spawning and migration times.     

A mass mortality of fishes caused by receding water levels in the vegetated littoral zone of the West Kleinemonde Estuary,South Africa

On 15 November 2017 the mouth of the West Kleinemonde Estuary breached following heavy catchment rains and increased river flow. The water level in the estuary following mouth opening decreased by 1.65 m within 24 h, resulting in an almost complete draining of the littoral zone where large beds of the aquatic macrophyte Ruppia cirrhosa and mats of the associated filamentous algae were present. As the water depth within the plant beds decreased, the macrophytes, together with the algal filaments, created an increasingly dense mat, trapping fish that were resident, foraging or passing through the littoral zone. By 16 November 2017 large numbers of fishes belonging to at least 20 species were trapped in pools and depressions within the littoral, as well as within the R. cirrhosa beds and filamentous algal mats in the lower reaches of this system. Other affected taxa included crustaceans, especially isopods, and large numbers of small bivalves attached to macrophyte vegetation. Beneficiaries of the fish kill, in terms of unexpected food availability, included a variety of piscivorous bird species and the Cape clawless otter Aonyx capensis. This is the first documented account of a diverse species fish kill associated with estuary mouth breaching.     

Ocean acidification alters temperature and salinity preferences in larval fish

Ocean acidification alters the way in which animals perceive and respond to their world by affecting a variety of senses such as audition, olfaction, vision and pH sensing. Marine species rely on other senses as well, but we know little of how these might be affected by ocean acidification. We tested whether ocean acidification can alter the preference for physicochemical cues used for dispersal between ocean and estuarine environments. We experimentally assessed the behavioural response of a larval fish (Lates calcarifer) to elevated temperature and reduced salinity, including estuarine water of multiple cues for detecting settlement habitat. Larval fish raised under elevated CO₂ concentrations were attracted by warmer water, but temperature had no effect on fish raised in contemporary CO₂ concentrations. In contrast, contemporary larvae were deterred by lower salinity water, where CO₂-treated fish showed no such response. Natural estuarine water—of higher temperature, lower salinity, and containing estuarine olfactory cues—was only preferred by fish treated under forecasted high CO₂ conditions. We show for the first time that attraction by larval fish towards physicochemical cues can be altered by ocean acidification. Such alterations to perception and evaluation of environmental cues during the critical process of dispersal can potentially have implications for ensuing recruitment and population replenishment. Our study not only shows that freshwater species that spend part of their life cycle in the ocean might also be affected by ocean acidification, but that behavioural responses towards key physicochemical cues can also be negated through elevated CO₂ from human emissions.     

Feeding of fish young from littoral of the gulf Arguin (Mauritania)

The results of ichthyologic investigations on littoral of the gulf Arguin in 2000–2004 are represented in this article. All main trophic fish groups—phytophagans, planktonphagans, benthophagans and predators—were discovered in the zone of littoral. The transfer to another trophic group is marked for the young of the most species while growth. Detritus and detritus-algal units have a special place in fish young diet. Sea grasses with covering area in the gulf of 390–490 km² are the origin of detritus. Favourable environmental conditions and high food provision make the gulf Arguin vitally important place for existense of neritic ichthyocene of northern Africa, the place for young fish reproduction and pasture.     

The impact of fishery on the state of populations of the European whitefish Coregonus lavaretus in Lake Imandra

The impact of fishery on the state of populations of the European whitefish Coregonus lavaretus in Lake Imandra, the largest water body of the Kola Peninsula, is considered. The retrospective analysis of catches in the period of 1930 to 1998 indicated that the consequences of an uncontrolled fishery are comparable with the effects of intensive technogenic pollution. As a result of the intensive commercial load on the water body over many decades, the number of age groups decreases, the size-weight indices in fish change, an early maturation at sizes small for the species is observed, and the population structure becomes more simple. Against the background of the improving environmental quality, the numbers of fish under the effects of the uncontrolled amateur and poaching fisheries continue to decrease, which leads to the change of the nucleus of the fish proportion of the community and the change of dominant species.     

Seasonal changes in the use of feeding resources by fish in stands of aquatic macrophytes in an Amazonian floodplain,Brazil

This study aimed to characterize the food intake by the fish assemblage inhabiting aquatic macrophytes stands, evaluating the changes in food availability among the periods of the hydrologic cycle and the trophic responses of the fish assemblage along with food availability. Fish sampling was conducted in stands of aquatic macrophytes (predominantly Paspalum repens, Poaceae) along banks of the Trombetas River during the four hydrologic periods (rising, high, receding, and low water level) that represent different phenological conditions of the habitat. The food consumption by the fish assemblage was analyzed for 41 species with stomach contents. The assemblage fed mainly on aquatic insects, periphytic algae and detritus. Food availability analysis showed that food resources changed among periods. Fifteen species were present in more than one period and most of those species showed dietary changes along with the hydrologic cycle, feeding mainly on invertebrates in the rising water period and periphytic algae and detritus in receding and low water periods. Only four species showed sufficient numbers to be analyzed in relation to diet and food availability along the at least three hydrologic periods, two of which showed a positive correlation between diet and food availability for three of the four periods; the other two species did not show this correlation, and presented omnivorous habits. In all cases, the selectivity values for the most important food items were near zero, indicating that intake was not motivated by feeding preference. Our results suggest that both trophic plasticity and omnivorous diets are important adaptations for species that inhabit temporally variable habitats such as aquatic macrophytes stands.     

Comparative haematology of ten species of marine fish from Visakhapatnam Coast

A comparative study has been made of haematological parameters (erythrocyte numbers, leucocyte numbers, haematocrit and haemoglobin), erythrocyte indices (MCV, MCH and MCHC) and cytometric measurements (cell and nucleus) of 10 species of marine fish from the Visakhapatnam Coast, of which six are from harbour waters, three from rock pools and one from inshore waters. It is found that active fish have high values of erythrocyte numbers, haematocrit, haemoglobin and nucleo/cytoplasmic ratio and low values of leucocyte numbers and erythrocyte cytosome measurements. The most active of all is the inshore species Rastrelliger kanagurta depicting the haematological requirements of an active fish with high oxygen demand to meet the requirements of high metabolic rate. The other active fish such as Megalops cyprinoides and Mugil cephalus are intermediate, with the rock pool fish and Caranx carangus with low values of nucleo/cytoplasmic ratio at the other extreme.     

Formation and development of the Black Sea-Caspian kilka Clupeonella cultriventris (Clupeidae) in the Rybinsk reservoir

We studied the state and development of the population of the Black Sea-Caspian kilka Clupeonella cultriventris in the Rybinsk reservoir from 1994 to 2010. The population dynamics, the rate of growth of the kilka, as well as its food relationships with other fish species of the pelagial community, were analyzed. It was found that the period of exponential increase in the numbers was replaced by the period of interannual fluctuations. With the development of the population, tendencies for a decrease in the rate of growth of the kilka and aggravation of its food relationships with other species are revealed, which is determined by changes in the structure of pelagic aggregations of fish. One of the most significant environmental factors determining dynamics of the numbers and state of the kilka population in the northernmost part of its modern range is water temperature.     

Fish behavioural responses to river discharge trends and the importance of habitat connectivity

Population behaviours associated with the migrations of coarse (non‐salmonid) fishes within river basins are amongst the most poorly understood dispersion mechanisms of temperate freshwater organisms, which in rivers are expected to be influenced by river discharge. We examined the timing and intensity of fish movements (via trapping) between the River Avon (Hampshire, England) and a small floodplain tributary, Ibsley Brook, and tested for correlations with trends in river discharge (i.e. mean cm of change in stage during trapping), water temperature and brook water velocity over twelve months in 1999–2000. 0‐group fishes dominated the catches. Intensities of movement between the brook and the river were similar in most months, but seasonal patterns were observed overall and for individual species. Few significant differences in overall numbers of fish were observed between the discharge trends, but many individual species demonstrated differences, mostly as more intense movement under fast rising discharge. Fish numbers in five species were correlated with river discharge trend, and movements in some species were correlated with the rate of temperature change (Δ° C 10 h sampling), and with changes in brook water velocity. Our results suggest daily movements between the river and small tributary brooks are triggered by changes in light intensity and water velocity, whereas seasonal movements of species between the river and brook are driven by changes in river discharge and water temperature, in particular associated with flood events. This study emphasizes the importance of connectivity in river systems, as fish movement between the Avon and its annexes occur under all flow regimes, but especially with rapidly rising discharge.     

Species composition and pattern of fish distribution in Siberia

At the end of the first half of the 20th century, 61 species and subspecies of fish, including one invader (bleak Alburnus alburnus) and 17 species—endemics of Baikal—were reported for Siberia (Berg, 1933, 1949). At the present time, in rivers, lakes, and reservoirs of Siberia, 96 fish species and subspecies are described, of which 80 are aboriginal and 16 are invaders; 33 species are endemics of Baikal. Each landscapegeographic zone of Siberia has its specific ichthyofauna: in rivers and lakes of the south of Siberia, species of boreal piedmont complex dominate; in water bodies of the steppe, forest-steppe, taiga, and southern parts of the forest-steppe zone boreal plain dominates; in the zone of tundra, arctic freshwater dominates; and in Baikal, the most part (35) of species belongs to the Baikal autochtonous complex. Most researchers, as before, distinguish in Siberia two ichthyogeographic sites—West Siberian and East Siberian—that enter the Arctic Province of the Circumpolar subregion of the Holarctic region. Baikal is considered in the rank of the suboblast of the Holarctic.