Growth,Reproduction and Condition of Roach (Rutilus rutilus (L.)), Perch (Perca fluviatilis,L.) and Ruffe (Gymnocephalus cernuus (L.)) in Eutrophic Lake Aydat (France)

The growth, reproduction and condition of adults of the three dominant fish species (roach, Rutilus rutilus, (L.); perch, Perca fluviatilis, L. and ruffe, Gymnocephalus cernuus, (L.)) in the eutrophic Lake Aydat were studied over one year cycle. Compared to published data, the growth of R. rutilus and G. cernuus was about average, while that of P. fluviatilis was below average. Comparing to literature, the fecundity of R. rutilus and G. cernuus was low but their oocytes were large. In contrast, P. fluviatilis had a high fecundity but small oocytes. At the end of summer, an abrupt decrease in the condition was recorded only for perch, probably due to stress as a result of environmental conditions. The sex-ratio was in favour of females for the three studied species but, in contrast to G. cernuus, the sex-ratio of R. rutilus and P. fluviatilis increased significantly also with age. It is concluded that Lake Aydat is a more favourable environment for R. rutilus and G. cernuus than for P. fluviatilis.     

Are fish early growth and condition patterns related to life-history strategies?

Life-history studies provide a global framework for comparison of fish species responses and trade-offs facing ecological and environmental constrains. A broad comparison among fishes’ early growth and condition traits is performed in order to determine ecological patterns of early development regarding latitudinal distribution, habitat use and life-history strategies. Based on Winemiller and Rose (1992) classification of life-history strategies, data on early growth and condition indices of 46 fish species worldwide was analysed. Available information on fishes’ early features, namely first year length percentage (relative to species maximum theoretical length), age at maturation and Fulton’s condition index (K), provided a good segregation of species by latitudinal distribution and habitat use, and evidenced the categories of the three-endpoint model. Higher larvae and juvenile growth rates and condition indices (K, mean RNA–DNA ratios and protein contents) were associated with tropical and temperate fish species that occur in complex or variable habitats (respectively coral reefs and estuaries). These species selected for the opportunistic and periodic strategies, investing highly in rapid growth in order to increase survival probability to counter high mortality rates during early stages or unstable habitat conditions. Later age at maturation, slower larvae and juvenile growth as well as lower mean condition indices were consistent with fish species from more stable or predictable environments, as polar regions and freshwater habitats, which selected for the equilibrium strategy. Nonetheless, differences in energy allocation strategies during early stages were not observed, evidencing the scarcity of available data regarding condition indices and/or the importance of integrating life-history intermediate strategies. Future research into condition indices and other physiological processes, for a broader set of species and for a wider latitudinal and habitat range including seasonal variability (particularly for species from tropical and polar regions), is essential to better understand or test current theories of species ecological patterns. The use of direct quantitative measures of young fishes’ metabolic investment and fitness constitutes a new approach for life-history studies, and should be fundamental for predicting species’ responses to acute environmental or human constrains, especially in a global climate change scenario that is expected to affect distribution and abundance of fish species worldwide.     

Growth Rates of Roach (Rutilus rutilus (L)) in a Cooling Water Reservoir under Different Thermal Conditions

Thermal effluent from the nuclear power plant on Lake Drūkšiai in Lituania has had a major impact on fish population and other aquatic biota of this lake. In 1984, Lake Drūkšiai was transformed into a cooling water reservoir of the Ignalina Nuclear Power Plant (INPP). The greatest impact of elevated water temperatures was on the fish species composition. Roach (Rutilus rutilus) adapted itself best to water temperatures averaging in summer month 30°C, and it grew faster, while other species became much less common. The mollusc Dreissena polymorpha Pall, became an important source of food for roach. When the long-term temperature exceeded 30°C, the rate of growth of roach slowed down.     

Impacts of bleak (Alburnus alburnus) and roach (Rutilus rutilus) on water quality,sedimentation and internal nutrient loading

Lake Vesijärvi, southern Finland, suffered sewere eutrophication by sewage effluent from the city of Lahti during the 1960's and the early 1970's. The municipal sewage loading was diverted from the lake in 1976 and the lake started to recover. However, in the 1980's blue-green algal blooms increased again and the recovery of the lake faded. Enclosure experiments demonstrated that high roach (Rutilus rutilus) biomass is one of the key factors in the fading recovery of the lake. In this study, the influence of roach and another cyprinid fish species (bleak, Alburnus alburnus) to planktonic algal productivity and biomass in Lake Vesijärvi was examined. Enclosure experiments in the field showed the impacts of planktivorous bleak on water quality; in an enclosure with a density of 1 fish m^–2 average daily algal production (1370 mg C m^–2) and chlorophyll-a concentration (50–90 µg 1^–1) were more than twice that in an enclosure without fish. Laboratory experiments showed that the availability of planktonic food affects the foraging behaviour of roach and consequently the internal nutrient loading from the sediment into the water. Roach caused the highest phosphorus loading and turbidity when there was no zooplanktonic food available in the water. The possible interactions between planktivorous and omnivorous fish species are discussed.     

Phenotypic plasticity in life-history traits of femaleThalassoma bifasciatum (Pisces: Labridae): 2. Correlation of fecundity and growth rate in comparative studies

Synopsis The cost of reproduction is a central concept in theories of life-history evolution. One way to empirically examine the tradeoff between current reproduction and future reproductive prospects is to use natural intraspecific variation in life-history traits. However, this approach is complicated by the sensitivity of life-history traits to variation in the level of resources. We report here an attempt to measure the cost of increasing reproductive activity in populations of female bluehead wrasse,Thalassoma bifasciatum, a coral-reef fish. All of the significant correlations of fecundity and growth rate were positive, in contradiction to the tradeoff predicted by the cost concept. In one of two regions studied, the populations with relatively high mean growth rate had a relatively large mean fecundity. The trait means were also positively associated over time: in months of rapid growth, female reproductive activity was high. Even after removing the effects of habitat and time period in a comparison of individual traits, no growth cost to reproduction appears. Variation in the abundance of resources over space and time is likely to interfere with the measurement of the cost of reproduction in many natural systems.     

Length–weight relationships of 40 freshwater fish species from two decades of monitoring in Flanders (Belgium)

Nearly 263 000 individual length–weight (L/W) data, collected during 2839 fish stock assessments between 1992 and 2009, were used to calculate L/W relationships (W = aL^b) of 40 freshwater fish species from Flanders (Belgium). Roach Rutilus rutilus, perch Perca fluviatilis, three‐spine stickleback Gasterosteus aculeatus, gudgeon Gobio gobio and European eel Anguilla anguilla were the most abundant species in our surveys. Mean a and b values were in accordance with those available in FishBase. Mean b across all examined species is 3.094 (95% CL = 3.041 to 3.148) indicating a tendency towards slightly positive allometric growth in most fishes (thirty‐three species with b > 3). On the basis of a form factor equation, we characterized 2 species as ‘eel‐like’, 7 as ‘elongated’, 22 as ‘fusiform’ and 9 species as ‘short and deep’. This paper adds a substantial dataset to the yet scarcely available a and b values of European populations of freshwater fish species.     

Direct Estimation of Food Consumption of Juvenile Fish in a Shallow Inlet of the Southern Baltic

The species composition and feeding behaviour of fish larvae and juveniles was investigated in a shallow inlet of the Southern Baltic. The aim of the study was to examine if there was a predatory impact of young fish on the observed annual collapse of the copepod population. Dominant fish species were herring (Clupea harengus), perch (Perca fluviatilis) and roach (Rutilus rutilus). Roach larvae preferred shallower areas, whereas young herring and perch were found in open water. Highest consumption values were always observed in the evening. By computing complete evacuation of the digestive tract in approximately 3.5 hours, daily consumption in percent of fish fresh weight was 1.3, 4.7 and 5.5% for young herring, roach and perch, respectively. The impact of young fish on the dynamics of the population of the copepod species Eurytemora affinis is negligible.     

Life-history traits of the endangered river blenny Salaria fluviatilis (Asso) and their implications for conservation

The life-history characteristics of the river blenny Salaria fluviatilis in a Mediterranean stream in north-east Spain have been studied. The maximum age observed was 4+ years in both sexes, although only age groups 0+ and 1+ years were well represented. For both sexes, growth was rapid between April and June (before the summer drought) and in October. The instantaneous rate of monthly growth (April to October) was positively correlated with water depth. All fish attained sexual maturity during their first year of life. Females spawned multiple times. Spawning occurred mainly from June to August, although older females (2+ years old) began in May. The relationship between fecundity and total length recorded for older females in the spring was not significantly different from that obtained for 1 year-old females in the summer. The mean diameter of ripe oocytes, however, was greater in older females. Larger eggs that were laid during a period of good food supply (spring) might have a higher probability of survival. The results suggest that female fecundity is affected by environmental conditions. The species is characterized by fast growth, early maturity, multiple spawning and limited longevity. This may be a good life-history strategy for small fish species in unstable environments, where adult mortality is high, variable or unpredictable. Some life-history traits of the river blenny suggest that this species might be vulnerable to more severe drought conditions than those associated with the Mediterranean climate.     

On r- and K-selection: evidence from the bean weevil (Acanthoscelides obtectus)

Populations of Acanthoscelides obtectus were maintained for 7 generations in either low- or high-larval densities in order to examine whether weevils life-history traits are modified in the direction predicted by r/K-selection theory. We found that r-selected population had a higher total fecundity, earlier age at first and last reproduction, and higher intrinsic rate of growth than K-selected population. Contrary to the theory, we have no evidence that preadult developmental time and adult longevity have been molded by density-dependent selection. The analysis of genetic variation of the weevils life-history traits in responses to different larval densities in both r- and K-selection populations indicates that different set of genes determining performance in two densities of analysed fecundity indices were accumulated during the course of the r- and K-selection.     

Correlation between Olfactory Responses, Dispersal Tendencies, and Life-history Traits of the Predatory Mite Neoseiulus Womersleyi (Acari: Phytoseiidae) of Eight Local Populations

To investigate the relationship between foraging behavior and life-history traits of the predatory mite Neoseiulus womersleyi, the olfactory responses, dispersal ratios from a prey patch, predation rates, fecundity, and developmental times in eight local populations of N. womersleyi were investigated. Significant differences among local populations were found in all these traits except fecundity. None of the life-history traits correlated with foraging behavior. A significant positive correlation was found only between the olfactory response and the dispersal ratio. These results suggested that predatory mites with low olfactory responses would stay in a prey patch longer than predatory mites with high olfactory responses.     

Life-history strategies of Acrossocheilus fasciatus (Barbinae, Cyprinidae) in the Huishui Stream of the Qingyi watershed, China

Life-history traits of Acrossocheilus fasciatus were examined using 384 specimens collected monthly during May 2009 and April 2010 in the Huishui Stream of the Qingyi watershed, China. Using scales for age determination, female and male fish comprised five and four age groups, respectively. The monthly changes in marginal increment ratio suggested that annuli on scales were formed during March through May. Total lengths back-calculated significantly increased with age for both sexes and varied significantly between the two sexes at each age. The fact that females had larger body size and grew faster than males indicated the sexual size dimorphism for this species. Both sexes got their 50% maturity at age 3, when females and males were 105.3 and 112.1?mm total length, respectively. Based on the monthly changes in the gonado-somatic index and egg-development process, fish spawned from April through August. Absolute fecundity ranged from 295 to 3,573 eggs per fish and increased significantly with age. But relative fecundity, ranging from 11.77 to 69.96?eggs/g, was not significantly different among age groups. Compared with the life-history traits of an upstream population in the Puxi Stream (a headwater stream within this study watershed), the downstream population of A. fasciatus in the Huishui Stream (a 4th-order stream) exhibits larger body size, faster somatic growth, later sexual maturity, and lower reproductive investment. These variations in life-history strategies between the two populations could perhaps be explained by the spatial heterogeneity in habitat environment along the upstream–downstream gradient in this watershed.     

Life history and parasites of the invasive mosquitofish (Gambusia holbrooki) along a latitudinal gradient

The eastern mosquitofish (Gambusia holbrooki) is among the most invasive fish worldwide and yet, while very abundant in most Mediterranean countries, it is unable to tolerate the colder winters of northern and central Europe. Understanding the effects of latitude on its life-history traits is essential to predict the potential for its invasion of central Europe in current scenarios of climate change. We studied the variation of life-history traits and parasite load in the eastern mosquitofish along a latitudinal gradient from southern France to southern Spain, sampling mosquitofish populations in eight Mediterranean river mouths ranging 5° in latitude. Southern mosquitofish populations displayed higher catch rates, allocated more energy to reproduction (gonadosomatic index and gonadal weight after accounting for fish size) and had a lower condition (total weight and eviscerated weight after accounting for fish size) than in northern populations. Despite variability among populations, size-at-maturity (L₅₀) significantly varied with latitude and northern individuals matured at smaller size (lower L₅₀). Parasite prevalence ranged from 0.0 to 26.7% but parasite richness was very low; all the parasites identified were larvae of pleurocercoid cestodes belonging to the order Pseudophyllidea. The abundance of mosquitofish parasites decreased with latitude and the presence and number of parasites infecting the mosquitofish had a significant negative effect on fish condition. The significant effects of latitude on the catch rates, life history and parasites of mosquitofish highlight the importance of latitudinal studies of invasive species to understand the interactive mechanisms of climate change and biological invasions.     

The structure of <Emphasis Type="Italic">Dreissena polymorpha</Emphasis> (Pallas) biocenosis and the role of mollusk in roach <Emphasis Type="Italic">Rutilus rutilus</Emphasis> (Linnaeus) feeding in Pleshcheevo Lake

As a result of studies on the macrozoobenthos composition of zebra mussel biocenosis in Lake Pleshcheevo carried out in 1996, a total of 44 species of bottom macroinvertebrates were found. The richest in terms of species composition were chironomids (17 species), oligochaetes (13 species), and mollusks and leeches (5 species each). After the introduction of zebra mussel Dreissena polymorpha (Pallas) into the lake, a natural biophilter was formed in the waterbody at depths of 4.5 to 9 m. This biophilter intercepts a substantial part of degrading macrophytes and allochtonous organic matter. Thus, the filter prevents the income of this organic matter in the lake’s profundal zone. Two roach Rutilus rutilus (Linnaeus) groups had inhabited Lake Pleshcheevo before dreissena introduction. Comparatively fast growing roach fed predominantly on mollusks of g. g. Valvata and Bithynia, while slowly growing roach fed mostly on zooplankton. After the introduction and mass development of D. polymorpha in the lake, roach started to consume these mollusks. This resulted in increases in the fish growth rate and maximum body size. Roach starts to feed on dreissena and other mollusks after reaching a body length of 15.0 cm. This relates to the third and the last change in the pharyngeal teeth shape, making possible for the fish to consume mollusks and to crush their shells.     

ECOLOGICAL AND HISTORICAL ASSOCIATIONS OF GENE FLOW IN DARTERS (TELEOSTEI: PERCIDAE)

Life history should relate to gene flow (Nm) through its influence on dispersal and effective population size. Comparative studies designed to elucidate this relationship must contend with historical events that can yield misleading estimates of gene flow and statistical problems associated with inclusion of life-history traits correlated with phylogeny. We studied the relationships of life-history characters and gene flow in 15 species of darters, a monophyletic group of stream fishes. Populations of coexisting species were sampled in three geographic regions with different Pleistocene glaciation histories. Gene flow was estimated indirectly from allozymes using two methods, 8 and private alleles. Isolation-by-distance was also tested using regression of pairwise estimates of gene flow (M?) on distance. Theta and private-alleles methods produced congruent estimates of Nm, except in a study region hypothesized to have been historically fragmented and then united following Pleistocene glaciation. A relatively weak association between life-history traits and Nm (based on θ) was observed when species from the historically fragmented region were included in stepwise regression analysis, because Nm was low despite life-history differences among taxa in this region. Excluding observations from this region produced stronger associations between clutch size and Nm (r² = 0.57), and between female size, egg size, and Nm (r² = 0.95). Additional analyses that corrected for female body size and phylogenetic nonindependence agreed that darters with high fecundity and small eggs exhibited high gene flow, whereas darters with small clutches and large eggs had low gene flow. The latter combination of life-history traits primarily is exhibited in species from headwater habitats where parental investment presumably confers survivorship on offspring. Reduced gene flow and genetic divergence among demes appear to be evolutionary consequences of this strategy.     

Bridge under troubled water: Turbulence and niche partitioning in fish foraging

The coexistence of competing species relies on niche partitioning. Competitive exclusion is likely inevitable at high niche overlap, but such divide between competitors may be bridged if environmental circumstances displace competitor niches to enhance partitioning. Foraging‐niche dimension can be influenced by environmental characteristics, and if competitors react differently to such conditions, coexistence can be facilitated. We here experimentally approach the partitioning effects of environmental conditions by evaluating the influence of water turbulence on foraging‐niche responses in two competing fish species, Eurasian perch Perca fluviatilis and roach Rutilus rutilus, selecting from planktonic and benthic prey. In the absence of turbulence, both fish species showed high selectivity for benthic chironomid larvae. R. rutilus fed almost exclusively on zoobenthos, whereas P. fluviatilis complemented the benthic diet with zooplankton (mainly copepods). In turbulent water, on the other hand, the foraging‐niche widths of both R. rutilus and P. fluviatilis increased, while their diet overlap simultaneously decreased, caused by 20% of the R. rutilus individuals turning to planktonic (mainly bosminids) prey, and by P. fluviatilis increasing foraging on littoral/benthic food sources. We show that moderate physical disturbance of environments, such as turbulence, can enhance niche partitioning and thereby coexistence of competing foragers. Turbulence affects prey but not fish swimming capacities, with consequences for prey‐specific distributions and encounter rates with fish of different foraging strategies (pause‐travel P. fluviatilis and cruise R. rutilus). Water turbulence and prey community structure should hereby affect competitive interaction strengths among fish species, with consequences for coexistence probability as well as community and system compositions.     

Interactions between developmental processes,growth, and food selection in the larvae and juveniles of Rutilus rutilus (L.) (Cyprinidae)

Summary The aim of this study was to assess the effects of developmental events, occurring in fish during the first weeks after hatching, on the quantity and quality of the ingested food and on growth. The investigation was carried out with the larvae and juveniles of Rutilus rutilus, the single cyprinid species occurring in an oligotrophic subalpine lake in Tirol, Austria. Comparison between availability of prey in the water and gut contents suggests that the selection of food by the young fish is strongly influenced by developmental processes. For example, the prevalence of indigestible phytoplankton in the gut of young larvae can be taken as a sign of the not yet fully developed sensory and locomotory capacities of the young fish (El-Fiky et al. 1987). Furthermore, quantitative and qualitative changes in the gut contents correlate strongly with changes in the form and relative length of the gut, but reflect only weakly the availability of prey in the water. In the Seefelder See population of R. rutilus the switch from a phytoplankton to a cladoceran dominated diet is accompanied by an increase in relative growth rate by nearly one order of magnitude (Wieser et al. 1988).     

Life-history phenotypes in populations of Brachyrhaphis episcopi (Poeciliidae) with different predator communities

Variation among populations in extrinsic mortality schedules selects for different patterns of investment in key life-history traits. We compared life-history phenotypes among 12 populations of the live-bearing fish Brachyrhaphis episcopi. Five populations co-occurred with predatory fish large enough to prey upon adults, while the other seven populations lacked these predators. At sites with large predatory fish, both sexes reached maturity at a smaller size. Females of small to average length that co-occurred with predators had higher fecundity and greater reproductive allotment than those from populations that lacked predators, but the fecundity and reproductive allotment of females one standard deviation larger than mean body length did not differ among sites. In populations with large predatory fish, offspring mass was significantly reduced. In each population, fecundity, offspring size and reproductive allotment increased with female body size. When controlling for maternal size, offspring mass and number were significantly negatively correlated, indicating a phenotypic trade-off. This trade-off was non-linear, however, because reproductive allotment still increased with brood size after controlling for maternal size. Similar differences in life-history phenotypes among populations with and without large aquatic predators have been reported for Brachyrhaphis rhabdophora in Costa Rica and Poecilia reticulata (a guppy) in Trinidad. This may represent a convergent adaptation in life-history strategies attributable to predator-mediated effects or environmental correlates of predator presence.     

Reproductive traits of the “ocellated killifish” Floridichthys polyommus Hubbs, 1936 (Pisces: Cyprinodontidae) inhabiting estuary of the Champotón River (Campeche,Mexico)

This study explores the reproductive biology and the influence of environmental factors on the reproductive traits of Floridichthys polyommus inhabiting the estuary of the Champoton River. The analysis included population structure, gonadal developmental stages, reproductive period, size at first sexual maturity, fecundity, sex ratio, and somatic indexes. A spatio‐temporal pattern in the distribution of the seven size classes was detected. The species showed a positive allometric growth. Sex ratio was 1.21:1 (females:males). Size at first maturity was 42.23 mm (females) and 47.8 mm (males). A higher absolute and relative fecundity was detected in Puente Champotón estuary (PCH) with lower salinities than those detected in the Delta (DE). The adaptive significance of this trait could be in response to the heavy osmotic constraint imposed by extreme salinities in the DE. Floridichthys polyommus prefers PCH for spawning, and as a result a higher number of ripe individuals was observed in this site, characterized by the highest nutrient levels, which can boost productivity and food availability for fish. Hepatosomatic index was negatively correlated with gonadosomatic index, suggesting energy transfer from the liver towards gamete production. Floridichthys polyommus exhibits an opportunistic strategy (early maturity, small oocytes, small clutches) suggesting that energy is allocated towards reproduction to compensate for the unpredictable hydrological conditions imposed by the estuary (particularly during the hurricane season). Floridichthys polyommus shows a reproductive strategy exhibited by fish living in unstable systems. A seasonal divergence was observed in the reproductive traits of F. polyommus, while differences between study sites were for fecundity.     

Sensitivity to thermal extremes in Australian Drosophila implies similar impacts of climate change on the distribution of widespread and tropical species

Climatic factors influence the distribution of ectotherms, raising the possibility that distributions of many species will shift rapidly under climate change and/or that species will become locally extinct. Recent studies have compared performance curves of species from different climate zones and suggested that tropical species may be more susceptible to climate change than those from temperate environments. However, in other comparisons involving responses to thermal extremes it has been suggested that mid‐latitude populations are more susceptible. Using a group of 10 closely related Drosophila species with known tropical or widespread distribution, we undertake a detailed investigation of their growth performance curves and their tolerance to thermal extremes. Thermal sensitivity of life history traits (fecundity, developmental success, and developmental time) and adult heat resistance were similar in tropical and widespread species groups, while widespread species had higher adult cold tolerance under all acclimation regimes. Laboratory measurements of either population growth capacity or acute tolerance to heat and cold extremes were compared to daily air temperature under current (2002–2007) and future (2100) conditions to investigate if these traits could explain current distributions and, therefore, also forecast future effects of climate change. Life history traits examining the thermal sensitivity of population growth proved to be a poor predictor of current species distributions. In contrast, we validate that adult tolerance to thermal extremes provides a good correlate of current distributions. Thus, in their current distribution range, most of the examined species experience heat exposure close to, but rarely above, the functional heat resistance limit. Similarly, adult functional cold resistance proved a good predictor of species distribution in cooler climates. When using the species’ functional tolerance limits under a global warming scenario, we find that both tropical and widespread Drosophila species will face a similar proportional reduction in distribution range under future warming.     

Mechanism of hybridization between bream Abramis brama and roach Rutilus rutilus in their native range

Mechanisms of hybridization between bream Abramis brama and roach Rutilus rutilus were studied within the native range of the species in a lake in southern Finland. Through the genetic analysis of A. brama, R. rutilus and putative hybrids, hybridization is shown to have occurred between female A. brama and male R. rutilus. These results match with previous findings from introduced habitats, suggesting that mating between female A. brama and male R. rutilus is the predominant mechanism through which the two species hybridize.