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Fish are frequently considered the top predator in freshwater food web models despite evidence that predatory birds can impact fish populations. In this study, we quantified bird predation rates on experimental populations of rainbow trout ( Oncorhynchus mykiss (Walbaum, 1792)) created by stocking nine small lakes in British Columbia, Canada. Combining estimates of fish mortality with estimated bird predation rates allowed us to partition fish mortality into that due to birds versus cannibalism. Our results indicated that bird predators had significant impacts on age-1 trout populations, but little impact on age-0 trout. Common loons ( Gavia immer Brunnich, 1764) were the principle predator among eight predatory bird species present, apparently consuming nearly 50% of all stocked age-1 trout and explaining almost 50% of variation in mortality rates. Age-1 trout mortality did not differ significantly from zero in lakes without loons. Birds consumed a small proportion of age-0 trout, and estimated consumption explained none of the variation in age-0 trout mortality among lakes. We conclude that birds affect fish populations by asymmetric predation on different age (size) classes and can be important top predators that should not be ignored when characterizing freshwater food webs in lakes.

1. The importance of body size and growth rate in ecological interactions is widely recognized, and both are frequently used as surrogates for fitness. However, if there are significant costs associated with rapid growth rates then its fitness benefits may be questioned. 2. In replicated whole-lake experiments, we show that a domestic strain of rainbow trout (artificially selected for maximum intrinsic growth rate) use productive but risky habitats more than wild trout. Consequently, domestic trout grow faster in all situations, experience greater survival in the absence of predators, but have lower survival in the presence of predators. Therefore, rapid growth rates are selected against due to increased foraging effort (or conversely, lower antipredator behaviour) that increases vulnerability to predators. In other words, there is a behaviourally mediated trade-off between growth and mortality rates. 3. Whereas rapid growth is beneficial in many ecological interactions, our results show the mortality costs of achieving it are large in the presence of predators, which can help explain the absence of an average phenotype with maximized growth rates in nature.

The acute effects of a herbicide based on 2,4-D on embryos and larvae of bleak, Alburnus alburnus L. exposed to concentrations of 25–3200 mg 1−1 for 12–48 hours were investigated. The 2,4-D delayed or stopped the development of embryos in their early stages, caused behavioural changes and morphological alterations. The L.C.50 values for embryos varied between 12–9 and 15·9–4mg 1−1 and for larvae from 51·6 to 111·2mg 1−1 according to the time of exposure. The level of 2,4-D in Lake Balaton, or similar shallow lakes, without substantial injury of the littoral fish fauna should not surpass 0·5–1·0 mg 1−1.

Given limited food, prey fishes in a temperate climate must take risks to acquire sufficient reserves for winter and/or to outgrow vulnerability to predation. However, how can we distinguish which selective pressure promotes risk-taking when larger body size is always beneficial? To address this question, we examined patterns of energy allocation in populations of age-0 trout to determine if greater risk-taking corresponds with energy allocation to lipids or to somatic growth. Trout achieved maximum growth rates in all lakes and allocated nearly all of their acquired energy to somatic growth when small in early summer. However, trout in low-food lakes took greater risks to achieve this maximal growth, and therefore incurred high mortality. By late summer, age-0 trout allocated considerable energy to lipids and used previously risky habitats in all lakes. These results indicate that: (i) the size-dependent risk of predation (which is independent of behaviour) promotes risk-taking behaviour of age-0 trout to increase growth and minimize time spent in vulnerable sizes; and (ii) the physiology of energy allocation and behaviour interact to mediate growth/mortality trade-offs for young animals at risk of predation and starvation.

When we assay behaviour in the laboratory, we assume that itshould be informativeof behaviour that would also be expressed innature. However, our assays usually (forcibly) remove individualsfrom the field, or from their holding cages/tanks, and then confinethem in some novel testing apparatus where they may or may notbe briefly acclimated for some minutes before quantifying theirbehaviour. Then, animals are returned to the field or holding cages,and the assay later repeated one or more times to see whetherbehaviour is consistent within individuals, and to determine somemean value for each individual (its behavioural type, or BT). Ofcourse,thisishighlyartificial,butweassumethatassaysunder thislevel of unnatural stress and novelty tell us something aboutbehaviour under natural conditions, where the animals’ behav-ioural repertoire evolved. In other words, we assume individualrank order is maintained across these contexts, and thus is corre-lated across contexts.As a first step towards testing this assumption (Biro 2012), Irepeatedly assayed fish behaviour over time, beginning shortly af-ter introduction to their individual home tanks and then twice perday for 1 week. My intent was to test ‘whether or not observationsmade under forced novel conditions predict behavioural traitsunder familiar and (presumably) less stressful conditions, condi-tions that are likely to be most similar to what animals in natureexperience, most of the time’ (Biro 2012, page 1296). In essence, Iobserved that behaviour was highly variable within individualsduring the first 2 days in captivity, but was repeatable thereafter. Inaddition, there was no indication that initial behaviour predictedBTs that were evident from subsequent assays. On this basis, Isuggestedthatweshouldnotassumethatarapidseriesofone,twoor three assays as commonly employed in personality studies issufficienttocharacterizeindividualbehaviourtypes.Why?Becauseit seems that individuals can markedly and systematically differ inthe rate at which they habituate and/or acclimate with repeatedbehavioural assays (Biro 2012), and in intraindividual variability(see below), meaning that rank orderof individual behaviour is notmaintained over the time during which habituation/acclimation isoccurring. That individuals might differ in patterns of habituation/acclimation is not new (see below), but the great majority of per-sonality studies conduct only one, two or three assays of behaviourand thus cannot address this issue head on in the face of highlyvariable behavioural data.I then speculated that the observed patterns of relatively unpre-dictablefollowedbypredictablebehaviourmayresultfromthehighlystressfulandartificialassayswetendtouseinourresearch,somethingwithwhichanimals havenothad anyevolutionaryexperience.Itwasmy opinion that characterizing an individual ’sBTusingdatasolelyfrom the brief interval when animals seem to be really stressed and(apparently)behavingerraticallyandunpredictablymaynotbeagoodidea,becauseanimalsinnaturewouldneverexperiencesuchaforcedand unnatural novel experience. Of course, animals in nature

In this study we identify the size-dependent risk of winter starvation mortality as a strong selective pressure on age-0 rainbow trout (Oncorhynchus mykiss) that could promote the risk-taking behaviour and allocation of energy to lipids previously observed in young trout cohorts. Age-0 trout subjected to simulated winter starvation conditions gradually depleted lipid reserves to a critical minimum lipid content below which death occurred. Small fish with lower lipid content exhausted lipid reserves earlier, and experienced high mortality rates sooner, than larger fish with greater lipid content. Consequently, winter starvation endurance was dependent upon size-dependent lipid reserves and winter duration. To validate the laboratory findings in the field, we stocked several size classes of hatchery-raised trout with known lipid content at the start of winter into two experimental lakes, and estimated survival and lipid depletion at winter's end. Larger age-0 trout had greater initial lipid reserves than smaller trout. Individuals depleted most of their lipid reserves over the winter, and experienced mortality that ranged from just under 60% for the largest individuals to just over 90% of the smallest individuals. Many survivors had lipid contents near, but none were below, the minimum lipid content determined in the laboratory.

Recent research suggests that the behavior of individuals under risk of pre- dation could be a key link between individual behavior and population and community dynamics. Yet existing theory remains largely untested at large spatial and temporal scales. We manipulated food available to age-0 rainbow trout while at risk of cannibalism, in a replicated factorial whole-lake experiment, to test whether the trade-off between growth and mortality rates is mediated by foraging activity by young fish under predation risk. We found that this trade-off exists for young fish at the whole-system scale, and that food- dependent behavioral variation has large mortality consequences. In high-food lakes, age- 0 trout spent less time moving, fewer individuals swam continuously, and those swimming continuously swam at slower speeds relative to those in low-food lakes. Age-0 trout also used deep, risky habitats less when food was abundant. This lower activity, combined with avoidance of risky habitats, coincided with 68% higher survival in high-food lakes. If general, this trade-off may be a key mechanism linking individual behavior to population- level processes in size-structured populations.

In a replicated whole-lake experiment, we (a) tested for the existence of a flexible habitat shift in response to predator presence in age-0 rainbow trout (Oncorhynchus mykiss) at risk of cannibalism and (b) evaluated the population-level consequences of habitat shifts in terms of growth and survival over their first growing season. Daphnid food and adult trout predators were substantially more abundant in pelagic than in littoral habitats. Age-0 trout used all habitats in populations without adult trout predators, whereas age-0 trout were observed only in the less profitable littoral habitat in populations with adult trout. Consequently, mean fall mass of age-0 trout in the presence of predators was almost half that observed in populations without adult trout. Despite the shift in habitat use, age- 0 trout experienced 90% mortality when adult trout predators were present, in comparison to only 36% mortality when absent. We conclude that the commonly observed habitat shifts by fish at risk of predation, observed at smaller scales, do in fact occur at the whole-system scale over long time intervals. These results suggest that fish are able to perceive risk at large spatial scales and thus take advantage of profitable (but normally risky) habitats when predators are absent, or move to less profitable refuge habitats when predators are present.

Growth, population structure, abundance, production, and feeding of Volga pikeperch were studied in Lake Balaton. The population was mainly comprised of age-groups 0+ (59%) and 1+ (18%), while the total share of age-groups 6+ and older was less than 1%. Mean back-calculated standard lengths for age-groups 0+-9+ were 67, 123, 144, 196, 233, 256, 283, 316, 350, and 369 mm, respectively. The instantaneous rate of growth in weight was lower at age 2+ than it was at age 3+ and 4+, suggesting unfavourable conditions for Volga pikeperch 120-160 mm in size. In autumn, the average abundance of Volga pikeperch was 34 ind. ha -1 , the biomass 1.04 kg ha -1 , and the production 0.76 kg ha -1 in the SW basin of Lake Balaton. Based on the diet, three phases can be distinguished during the ontogeny. Zooplanktivory is characteristic for the early juvenile stage up to 50 mm in size. At the size of 50-150 mm the diet becomes heterogeneous, consisting of zooplankters, benthic invertebrates, and fish. The third phase is the piscivory which becomes a determinant at over 150 mm in size. In this phase cannibalism was also significant, as 21.9% of consumed fish were conspecifics.

Varying habitats of northern and southern inflows running into Lake Balaton provide appropriate living conditions for numerous fish species. Inflowing canals, creeks, and rivulets are presently the exclusive living places for a number of endangered and rare fish species (habitats, nursing, and feeding areas). Except for River Zala, these places functionally replaced the natural bays and marshy areas being dredged a long time ago. Particular studies on faunistics, ecology, and population dynamics during 1995–2001 proved the occurrence of 26 fish species in these water bodies at different densities. Most species are endangered due to intensified tourism, water quality deterioration, commercial and sport fisheries, and habitat modification.

Despite accumulating evidence for individual variation in behavioural plasticity, there is currently little understanding of the causes and consequences of this variation. An outstanding question is whether individual reaction norm (RN) slopes are consistent across different environmental variables—that is, whether an individual that is highly responsive to one environmental variable will be equally responsive to a second variable. Another important and related question is whether RNs are themselves consistently expressed through time or whether they are simply state dependent. Here, we quantified individual activity rates of zebrafish in response to independent manipulations of temperature and food availability that were repeated in discrete ‘bursts’ of sampling through time. Individuals that were thermally responsive were not more responsive to food deprivation, but they did exhibit greater unexplained variation. Individual RN slopes were consistent (repeatable) over time for both temperature ( R slope = 0.92) and food deprivation responses ( R slope = 0.4), as were mean activity rates in the standard environment ( R intercept = 0.83). Despite the high potential lability of behaviour, we have demonstrated consistency of behavioural RN components and identified potential energetic constraints leading to high consistency of thermal RNs and low consistency of food deprivation RNs.

The importance of studying individual variation in locomotor performance has long been recognized as it may determine the ability of an organism to escape from predators, catch prey or disperse. In ectotherms, locomotor performance is highly influenced by ambient temperature (Ta), yet several studies have showed that individual differences are usually retained across a Ta gradient. Less is known, however, about individual differences in thermal sensitivity of performance, despite the fact that it could represent adaptive sources of phenotypic variation and/or additional substrate for selection to act upon. We quantified swimming and jumping performance in 18 wild-caught tropical clawed frogs (Xenopus tropicalis) across a Ta gradient. Maximum swimming velocity and acceleration were not repeatable and individuals did not differ in how their swimming performance varied across Ta. By contrast, time and distance jumped until exhaustion were repeatable across the Ta gradient, indicating that individuals that perform best at a given Ta also perform best at another Ta. Moreover, thermal sensitivity of jumping endurance significantly differed among individuals, with individuals of high performance at low Ta displaying the highest sensitivity to Ta. Individual differences in terrestrial performance increased with decreasing Ta, which is opposite to results obtained in lizards at the inter-specific and among-individual levels. To verify the generality of these patterns, we need more studies on individual variation in thermal reaction norms for locomotor performance in lizards and frogs.

The Hospitals / Residents problem with Couples (hrc) is a generalisation of the classical Hospitals / Residents problem (hr) that is important in practical applications because it models the case where couples submit joint preference lists over pairs of (typically geographically close) hospitals. In this paper we give a new NP-completeness result for the problem of deciding whether a stable matching exists, in highly restricted instances of hrc, and also an inapproximability bound for finding a matching with the minimum number of blocking pairs in equally restricted instances of hrc. Further, we present a full description of the first Integer Programming model for finding a maximum cardinality stable matching in an instance of hrc and we describe empirical results when this model applied to randomly generated instances of hrc.

We develop Integer Programming (IP) solutions for some special college admission problems arising from the Hungarian higher education admission scheme. We focus on four special features, namely the solution concept of stable score-limits, the presence of lower and common quotas, and paired applications. We note that each of the latter three special feature makes the college admissions problem NP-hard to solve. Currently, a heuristic based on the Gale-Shapley algorithm is being used in the application. The IP methods that we propose are not only interesting theoretically, but may also serve as an alternative solution concept for this practical application, and other similar applications.

This paper reviews the issue of freshwater biodiversity, from the time of its introduction on national and international bases. The project was initiated in co-operation by the International Union of Biological Sciences, the International Society of Limnology Working Group on Biodiversity in Freshwater Ecosystems and the Hydrobiological Committee of Hungarian Academy of Sciences. The first International Union of Biological Sciences International Workshop on Freshwater Biodiversity was convened at Balatonfüred, Hungary during 25-28 August 1996. A framework was developed and a wide scale project, BIODIVERSITAS, was worked out by Prof. Hiroya Kawanabe and Dr. Christian Lévesque. This project became one of the main issues of the International Union and has been incorporated into the activities of the United Nations Educational, Scientific and Cultural Organization. Several national and international meetings have been held dealing with particular fields in relation to species richness of aquatic ecosystems so that the topic has became a broad scientific, social, popular, political and economic issue. Scientific questions already cover nearly all aspects of biodiversity, for example, how to measure indices, and how to manage and preserve species richness in the most endangered aquatic habitats. Inventorying, monitoring and conservation of biodiversity in freshwater are of vital importance. All freshwater plant and animal species (invertebrates and vertebrates) are more or less threatened by human activities. Any decrease in diversity of aquatic species may indicate harmful human impacts, and whenever these activities increase, the living world of rivers, lakes and reservoirs is degraded. The rehabilitation of degraded aquatic systems has been a major limnological issue all over the world. Freshwater biodiversity is studied in all types of habitats: lakes, reservoirs, rivers and wetlands and includes species from bacteria to aquatic vertebrates, and focuses on functional aspects and habitat differences (lake shores/ecotones, open waters and benthic habitats). Research on freshwater biodiversity can best be organized according to selected water bodies on different continents. The ‘status quo’ of freshwater stocks is of crucial importance on local, regional and global scales. A crucial point is the high-level training of specialists and improving public-relations in order to make communities understand all aspects concerning ecological crises (e.g., habitat and biodiversity erosion and their consequences on nature and human beings). However, special interest must also be afforded to soil and sediment biodiversity, microbial biodiversity, human dimensions and genetic diversity in both land and aquatic systems.

An initial value problem for the generalized Kolmogorov-Petrowsky-Piscunov (nonlinear degenerate reaction-diffusion) equation is studied numerically by the help of a slightly modified finite difference scheme of Douglas-Yanenko-Mimura type. If the initial function has compact support, the solution also will have compact support and an interface appears between the domains where the solution is positive and where it is zero. We present some examples for different parameter values where the numerical solution as well as numerical interfaces behave according to the analytical theory.

(1998). Reed-periphyton complex in the littoral of shallow lakes. SIL Proceedings, 1922-2010: Vol. 26, No. 4, pp. 1852-1856.

Thermal habitat selection and behavior by young-of-year brook trout Salvelinus fontinalis was studied in a lake in central Ontario, Canada. In May, trout foraged actively within 2 m of shore in the warmest water available (∼15°C). In early June, trout foraged near the bottom within 4 m of shore, where bottom water temperatures were near, or at, the upper thermal tolerance, for trout, of 20°C. In July, when ambient water temperatures ranged from 23°C to 27°C, trout lay on the bottom in the coldest water available (18–20°C) in discrete areas 3–8 m from shore. Flow rate of cold groundwater accounted for 87% of the variance in trout density in these areas, and the data suggest that a minimum flow rate of 125 mL·m−2·min−1 is required for trout to take up station. When trout were displaced from holding positions, sites with greater groundwater flow were more quickly reoccupied by trout than sites with lower flow. Experimentally created trough-like depressions at these sites attracted higher densities o...

The population structure, abundance (ind m−2), biomass and reproduction of Corophium curvispinum, an important element of the littoral fauna, have been studied at four sampling stations on the northern shoreline of Lake Balaton (Keszthely Bay, Szigliget Bay, Bozsai Bay and Paloznak Bay) three times a year (spring, summer and autumn) in Phragmites growing period from May 1991 to October 1993 and in summer 1994. The sampling stations represent the trophic gradient of the lake. The environmental parameters (Chlorophyll-a content of the plankton and of the reed periphyton, and suspended solid content of the water) were significantly higher (ANOVA) in the western basin (Keszthely and Szigliget bays) than in the eastern basin (Bozsai and Paloznak bays). However, the population parameters (length of the animals, percentage of juveniles, length of ovigerous females, percentage of ovigerous females and fecundity) did not differ significantly between the two basins. Both the abundance and biomass were higher in the middle than in the westernmost and easternmost bays but the difference is not significant. The ovigerous females were significantly bigger in spring than in summer and autumn. The egg number per female was also significantly greater in spring than in summer and autumn. The length of ovigerous females and the fecundity in summer did not differ significantly from those of autumn data. There is a significant positive correlation (Spearman rank correlation) between both abundance and biomass and the above environmental parameters. The length of ovigerous females and the fecundity were inversely correlated with the plankton Chlorophyll-a concentrations. The abundance of C. curvispinum in the reed belt of Lake Balaton is greater than in several parts of the Dnieper and Volga. However, it is much lower than in the Don, Oka, Danube and Rhine rivers.

Carp, common bream, white bream, wild goldfish and roach are the most common large‐sized cyprinids in the littoral zone of Lake Balaton. Their cumulative average contribution to the littoral fish fauna is between 65.0% and 86.2% by weight but the relative abundance of each species differs by habitat. The diet of four of these five cyprinids significantly differed within and between all the three habitats examined The highest food‐niche overlap was detected between carp and white bream along the stony shoreline and in the reed grass stands (Horn's Index). However, high food‐niche overlaps were common in the open water areas, where all these species compete for similar food types. According to our results, the interspecific competition among cyprinids is expected to increase with the implementation of shoreline regulations and the destruction of the reed‐grass habitat.

A common method to assess behavioral types in personality research involves the use of a single emergence test (employed by researchers working on fish, avian, mammal, amphibian, and invertebrate taxa), whereby a shorter latency to emerge from a holding container into a novel environment is inferred to represent greater ‘boldness’. Although any behavior might be context specific, studies using this single assay type must assume it reflects boldness in other similar contexts, otherwise it cannot reflect personality (defined as consistency across time and/or contexts). We attempted to validate whether a single assay of this type is correlated with other similar assays of boldness under more familiar, and less stressful, situations. We compared single emergence test scores of two species of damselfish (Pomacentrus wardi; P. amboinensis) in a novel environment, with two different behavioral assays of the same fish in subsequent repeated trials in home tanks. Although behavior was highly repeatable in home tanks, we found no correlation between emergence test scores in the novel environment and measures of latency to emerge from shelter following disturbance, or activity levels, on the first, second, or third observations in home tanks; there was also no correlation when we used average home tank scores from mixed models that accounted for individual differences (i.e., plasticity) in the rate of habituation (latency) and acclimation (activity). Our results therefore lead us to question the validity of using this single emergence test assay as a predictor of general boldness and to question the use of any single assay of behavior in personality research.

In this paper we analyze the consequences of the fairness recommendation of the Venice Commission in allocating voting districts among larger administrative regions. This recommendation requires the size of any constituency not to differ from the average constituency size by more than a fixed limit. We show that this minimum difference constraint, while attractive per definition, is not compatible with monotonicity and Hare-quota properties, two standard requirements of apportionment rules. We present an algorithm that efficiently finds an allotment such that the differences from the average district size are lexicographically minimized. This apportionment rule is a well-defined allocation mechanism compatible with and derived from the recommendation of the Venice Commission. Finally, we compare this apportionment rule with mainstream mechanisms using real data from Hungary and the United States.

To assess the costs and benefits of young fish adopting different behavioural tactics, field studies of juvenile salmonines have assumed that (but did not test whether) the rate of foraging attempts predicts ingestion rate. We tested this assumption by quantifying capture, ingestion, and rejection rates of potential prey items for individual young-of-the-year brook trout (Salvelinus fontinalis) in a lake. Overall, capture rate (a conservative estimate of the rate of foraging attempts) was only a fair predictor of overall ingestion rate (Kendallis τ= 0.54) and only 46% of captured items (number/minute) were ingested. Surface capture rate was a poor predictor of surface ingestion rate ( τ= 0.27) and only 1% of captured items were ingested. In contrast, subsurface capture rate was an excellent predictor of subsurface ingestion rate ( τ= 0.75) and 93% of captured items were ingested. No benthic prey captures were observed. Fish that ingested a low proportion of captured items spent a greater proportion of time moving, moved faster, and pursued prey further than fish that ingested a higher proportion of captured items. Rejection of captured items can represent a significant and little appreciated component of the foraging cycle for young salmonid fishes. Resume : Dans leurs tentatives diOvaluer les avantages et les inconvOnients des diffOrentes tactiques comportementales adoptOes par les jeunes chez le poisson, les Otudes sur le terrain portant sur les jeunes salmonidOs ont pris comme hypothse, sans la tester, que le taux des tentatives pour capturer des proies est un indicateur du taux diingestion. Nous avons vOrifiO cette hypothse en chiffrant les taux de capture, diingestion et de rejet de proies chez des ombles de fontaine de liannOe ( Salvelinus fontinalis) OtudiOs individuellement dans un lac. Au bilan, le taux de capture (une mesure prudente du taux de tentatives) constitue au mieux une variable prOdictive passable du taux global diingestion ( τ= 0,54, Kendall) et en outre, seulement 46% des proies (numOro/minute) sont ingOrOes. Le taux de capture ‡ la surface de lieau est un mauvais indicateur du taux diingestion des proies capturOes ‡ la surface ( τ= 0,27); seulement 1% des proies capturOes ‡ ce niveau sont ingOrOes. Par contre, le taux de capture sous lieau constitue un excellent indicateur du taux diingestion des proies capturOes ‡ ce niveau ( τ= 0,75); 93% des proies capturOes ainsi sont ingOrOes. Aucune capture de proies benthiques nia OtO observOe. Les sujets qui ingrent une faible partie des proies quiils capturent consacrent davantage de leur temps pour se dOplacer, se dOplacent plus rapidement et poursuivent leurs proies plus longtemps que ceux qui ingrent une grande partie des proies quiils capturent. Le rejet de proies peut constituer un facteur important et mOconnu du cycle dialimentation des jeunes salmonidOs. (Traduit par la ROdaction)

The effect of the insecticide, S-Deltamethrine (DM, LC50 for mosquito larvae: 0.02 ppb), in the concentration range between 0.025 and 2500 ppb was examined in both embryogenesis and embryonic evolution of the electron transport system (ETS) of the bream, roach, barbel and pike. A 0.025 ppb concentration of DM caused 10-25% death of the embryos in the first 2 days of incubation. Fifty per cent of the roach embryos died by the end of a 144 h incubation period when the concentration was 0.025 ppb. In 2.5 ppb, 50% of the embryos died after 120 h. In 25 ppb, 50% death was registered after 96 h, and in 250 and 2500 ppb, 50% death was detected after 48 h. Fifty per cent of the barbel embryos died after a 48 h long incubation time in 250 and 2500 ppb. The same mortality was detected for the embryos of pike in 2500 ppb after a longer (148 and 168 h) incubation time. Half of the bream embryos died after 24 and 48 h at a concentration of 2500 ppb. Larvae showed a more sensitive response to treatments than did embryos. After hatching, 30-84% of the larvae died in 0.025 ppb. Compared to embryos, larvae moved less in a concentration of 0.025 ppb and could not swim as easily as controls. In a concentration >0.25-2.5 ppb, larvae were passive and often malformed. S-Deltamethrine inhibited ETS activity in a concentration-dependent manner. Electron transport system activity of larvae was reduced by 50% in 250 ppb concentration.

Intra- and interspecific effects together with changing environmental conditions regulate the dynamics of the fragile bleak populations in Lake Balaton. Size- and age-structures, length-weight relationships and mortality were studied on 1493 individuals and growth history were determined using scales from 703 specimens. The population growth rate was slow and the basic population parameters showed area variations along the longitudinal axis of the lake. Gut contents were analyzed in 224 individuals. The bleak stocks are trophically strongly related to the littoral zooplankton and benthos; and they play a significant energy-mediating role in the food-webs between the periphytic communities and fish assemblages in the littoral zone of Lake Balaton.

The productivity of common carp (Cyprinus carpio L.) varies among continents according to current fish-pond management practices and variations in trophic conditions and/or fish-carrying capacity. “Biomanipulation” as a management tool for aquatic communities is aimed at exploiting “top-down forces” or the “trophic cascade” in order to influence the food-web and efficiency of energy transfer from primary producers to fish. The aim of food-web manipulation in fish-ponds has usually been in contrast to that in natural waters. This paper focusses on the basic ecosystem processes and provides an overview of the efficiency of energy transfer in various lakes, ponds and reservoirs which may be influenced by food-web manipulation using different approaches (fertilization, stocking, chemical treatment, supplementary feeding). Several sources of data have also been summarized illustrating the relationships between stocking rate and fish production in a variety of natural and artificial ecosystems.

Abstract We examined the variation in foraging movements in a population of young-of-the-year (YOY) brook charr living in the near-shore littoral zone of a lake. By repeating the methodology of an earlier stream study, we made direct comparisons between data from lake and stream populations. In general, the pattern of variation in foraging movements was similar between the two sites with greater variability and activity observed in the lake population. The dichotomous nature of the proportion of time spent moving in the stream was also observed in the lake population but in a reversal of the stream pattern. Charr that moved constantly while foraging represented the largest movement category in the lake. In general, variation in foraging movements were more strongly related to the rate of prey rejection, whereas environmental factors, such as distance from shore, submerged objects, and the amount of overhead riparian cover, were more strongly related to prey ingestion. This last finding directly contrasts with that found in the stream literature for YOY charr in still water where ingestion rate, as estimated using feeding attempt rate, increases with the mobility of YOY charr.

The stable roommates problem with payments has as input a graph G=(V,E) with an edge weighting w: E→ℝ+ and the problem is to find a stable solution. A solution is a matching M with a vector $p\in{\mathbb R}^V_+$ that satisfies pu+pv=w(uv) for all uv∈M and pu=0 for all u unmatched in M. A solution is stable if it prevents blocking pairs, i.e., pairs of adjacent vertices u and v with pu+pv

A matching game is a cooperative game (N, v) defined on a graph G = (N, E) with an edge weighting $w: E \rightarrow R_+$ The player set is N and the value of a coalition $S \subseteq NSN$ is defined as the maximum weight of a matching in the subgraph induced by S. First we present an $O(nm + n^2 \log n)$ algorithm that tests if the core of a matching game defined on a weighted graph with n vertices and m edges is nonempty and that computes a core member if the core is nonempty. This algorithm improves previous work based on the ellipsoid method and can also be used to compute stable solutions for instances of the stable roommates problem with payments. Second we show that the nucleolus of an n-player matching game with a nonempty core can be computed in $O(n^4)$ time. This generalizes the corresponding result of Solymosi and Raghavan for assignment games. Third we prove that is NP-hard to determine an imputation with minimum number of blocking pairs, even for matching games with unit edge weights, whereas the problem of determining an imputation with minimum total blocking value is shown to be polynomial-time solvable for general matching games.

In practical applications, algorithms for the classic version of the hospitals residents problem (the many-one version of the stable marriage problem) may have to be extended to accommodate the needs of couples who wish to be allocated to (geographically) compatible places. Such an extension has been in operation in the National Resident Matching Problem (NRMP) matching scheme in the United States for a number of years. In this setting, a stable matching need not exist, and it is an NP-complete problem to decide if one does. However, the only previous empirical study in this context (focused on the NRMP algorithm), together with information from NRMP, suggest that, in practice, stable matchings do exist and that an appropriate heuristic can be used to find such a matching. The study presented here was motivated by the recent decision to accommodate couples in the Scottish Foundation Allocation Scheme (SFAS), the Scottish equivalent of the NRMP. Here, the problem is a special case, since hospital preferences are derived from a “master list” of resident scores, but we show that the existence problem remains NP-complete in this case. We describe the algorithm used in SFAS and contrast it with a version of the algorithm that forms the basis of the NRMP approach. We also propose a third simpler algorithm based on satisfying blocking pairs, and an FPT algorithm when the number of couples is viewed as a parameter. We present an empirical study of the performance of a number of variants of these algorithms using a range of datasets. The results indicate that, not surprisingly, increasing the ratio of couples to single applicants typically makes it harder to find a stable matching (and, by inference, less likely that a stable matching exists). However, the likelihood of finding a stable matching is very high for realistic values of this ratio, and especially so for particular variants of the algorithms.

(1993). Biomass assessment of Chironomidae larvae in the littoral zone of Lake Balaton (Hungary) SIL Proceedings, 1922-2010: Vol. 25, No. 2, pp. 689-693.

Popular matchings have recently been a subject of study in the context of the so-called House Allocation Problem, where the objective is to match applicants to houses over which the applicants have preferences. A matching M is called popular if there is no other matching M′ with the property that more applicants prefer their allocation in M′ to their allocation in M. In this paper we study popular matchings in the context of the Roommates Problem, including its special (bipartite) case, the Marriage Problem. We investigate the relationship between popularity and stability, and describe efficient algorithms to test a matching for popularity in these settings. We also show that, when ties are permitted in the preferences, it is NP-hard to determine whether a popular matching exists in both the Roommates and Marriage cases.

Age-composition, size-distribution, length/weight relationships and growth both in length and weight of bream stocks were studied on fishes collected in NE and SW basins of Lake Balaton during 1982/83. Stocks consisting of 10 to 12 age-groups were observed at the two lake areas. The linear growth and weight-gain in the SW-basin were annually faster than in the NE-basin, however, the growth of bream in Lake Balaton was slow as compared to that observed 10 years ago. Parallel with progressive eutrophication, the density of bream stocks increased by some 5–10 % especially at hypertrophic lake areas (SW) and consequently their growth was transformed to densitydependent. In the appearance of strong year-classes some cyclicism could be observed especially in the SW-basin.

Consistent individual differences in behaviour, termed personality, are common in animal populations and can constrain their responses to ecological and environmental variation, such as temperature. Here, we show for the first time that normal within-daytime fluctuations in temperature of less than 3°C have large effects on personality for two species of juvenile coral reef fish in both observational and manipulative experiments. On average, individual scores on three personality traits (PTs), activity, boldness and aggressiveness, increased from 2.5- to sixfold as a function of temperature. However, whereas most individuals became more active, aggressive and bold across temperature contexts (were plastic), others did not; this changed the individual rank order across temperatures and thus altered personality. In addition, correlations between PTs were consistent across temperature contexts, e.g. fish that were active at a given temperature also tended to be both bold and aggressive. These results (i) highlight the importance of very carefully controlling for temperature when studying behavioural variation among and within individuals and (ii) suggest that individual differences in energy metabolism may contribute to animal personality, given that temperature has large direct effects on metabolic rates in ectotherms.

The warming of coastal oceans due to climate change is increasing the overwinter sur- vival of tropical fishes transported to temperate latitudes by ocean currents. However, the processes governing early post-arrival mortality are complex and can result in minimum threshold tempera- tures for overwinter survival, which are greater than those predicted based upon physiological tem- perature tolerances alone. This 3.5 mo laboratory study monitored the early performance of a tropi- cal damselfish Abudefduf vaigiensis that occurs commonly during austral summer along the SE Australian coast, under nominal summer and winter water temperatures, and compares results with a co-occurring year-round resident of the same family, Parma microlepis. Survivorship, feeding rate, growth and burst swimming ability (as a measure of predator escape ability) were all reduced for the tropical species at winter water temperatures compared to those in summer, whereas the temperate species experienced no mortality and only feeding rate was reduced at colder temperatures. These results suggest that observed minimum threshold survival temperatures may be greater than pre- dicted by physiology alone, due to lowered food intake combined with increased predation risk (a longer time at vulnerable sizes and reduced escape ability). Overwinter survival is a significant hurdle in pole-ward range expansions of tropical fishes, and a better understanding of its complex processes will allow for more accurate predictions of changes in biodiversity as coastal ocean temper- atures continue to increase due to climate change.

Chant and cantillation research is particularly interesting as it explores the transition from oral to written transmission of music. The goal of this work to create web-based computational tools that can assist the study of how diverse recitation traditions, having their origin in primarily non-notated melodies, later became codified. One of the authors is a musicologist and music theorist who has guided the system design and development by providing manual annotations and participating in the design process. We describe novel content-based visualization and analysis algorithms that can be used for problem-seeking exploration of audio recordings of chant and recitations.

Given an instance I of the classical Stable Marriage problem\ud with Incomplete preference lists (smi), a maximum cardinality matching\ud can be larger than a stable matching. In many large-scale applications\ud of smi, we seek to match as many agents as possible. This motivates the\ud problem of finding a maximum cardinality matching in I that admits the\ud smallest number of blocking pairs (so is "as stable as possible"). We show\ud that this problem is NP-hard and not approximable within n1−ε, for any\ud ε > 0, unless P=NP, where n is the number of men in I. Further, even\ud if all preference lists are of length at most 3, we show that the problem\ud remains NP-hard and not approximable within δ, for some δ > 1. By\ud contrast, we give a polynomial-time algorithm for the case where the\ud preference lists of one sex are of length at most 2.

Contrary to earlier observations the food composition of bream (Abramis brama L.) in Lake Balaton has changed in parallel with eutrophication. These changes were probably caused by increased population density and connected with density dependent growth as well as sharpened inter- and intraspecific competition in the cyprinid community. According to the frequency of occurrence, zooplankton followed by benthic invertebrates comprised the majority of the bream's food. By weight, however, benthic food dominated in both basins. Size-related dietary changes were pronounced, but statistically not always significant, suggesting the overall importance of the most abundant and available prey types. Bream did not strongly select any of the zooplankton groups, however, seasonal changes in food composition alternated in parallel with the trophic gradient along the longitudinal axis of the lake.

Variations is an electroacoustic sound installation commissioned by the Villa Bernau in Wabern, Switzerland. The original sound installation was created in coordination with the sculptor Wolfram Renger. Renger’s sculptures deal with the historical forming of prisons of cultural and artistic identities. The installation was divided into three spatialized parts. Penalty dealt with the problems of industrial death via the death penalty. Lizkhor dealt with questions of musical/physical closure (via exploring questions of the US prison system) and the relationship of closure to cultural memory. Borders dealt with questions of the limits of closure (exploring European border problems) and its relationship to the forming of cultural identities.

The possibility for fishery-induced evolution of life history traits is an important but unresolved issue for exploited fish populations. Because fisheries tend to select and remove the largest individuals, there is the evolutionary potential for lasting effects on fish production and productivity. Size selection represents an indirect mechanism of selection against rapid growth rate, because individual fish may be large because of rapid growth or because of slow growth but old age. The possibility for direct selection on growth rate, whereby fast-growing genotypes are more vulnerable to fishing irrespective of their size, is unexplored. In this scenario, faster-growing genotypes may be more vulnerable to fishing because of greater appetite and correspondingly greater feeding-related activity rates and boldness that could increase encounter with fishing gear and vulnerability to it. In a realistic whole-lake experiment, we show that fast-growing fish genotypes are harvested at three times the rate of the slow-growing genotypes within two replicate lake populations. Overall, 50% of fast-growing individuals were harvested compared with 30% of slow-growing individuals, independent of body size. Greater harvest of fast-growing genotypes was attributable to their greater behavioral vulnerability, being more active and bold. Given that growth is heritable in fishes, we speculate that evolution of slower growth rates attributable to behavioral vulnerability may be widespread in harvested fish populations. Our results indicate that commonly used minimum size-limits will not prevent overexploitation of fast-growing genotypes and individuals because of size-independent growth-rate selection by fishing.