bluuebunny/crossref_metadata_2025_split huggingface dataset:
Distribution patterns of Cladocera in subarctic Fennoscandian lakes and their potential in environmental reconstruction
Authors: Korhola Atte 
Published: July 2006

Multivariate statistical techniques were used to examine the relationships between surface‐sediment cladoceran assemblages and 28 physical and chemical variables in 53 small subarctic lakes from northern Fennoscandia. The lakes were distributed along a steep eco‐climatic gradient, spanning boreal corniferous forest to treeless tundra. In general, the sites were small, oligotrophic, and bathymetrically simple, with little or no disturbance in their catchments. From the initial 53 localities, only 36 contained a sufficient number of cladoceran remains for reasonable quantification. From these, a total of 29 cladoceran taxa representing 19 genera were identified, comprising predominantly littoral chydorid species. A constrained redundancy analysis (RDA) and associated Monte Carlo permutation tests indicated that maximum lake depth, sediment organic content, epilimnetic summer temperature, lake perimeter, and lake catchment area made statistically significant (p le; 0.05) contributions to explaining the variance in the cladoceran taxon data. These five variables together accounted for 67.7% of the explained variance, and made a unique contribution of 26.8% to the total variance: all physical determinants independently captured 33.2% of the total variance. The significance of the most powerful explanatory variables is discussed in the paper in detail, and autecological information regarding the most common cladoceran taxa is given.To assess the potential of cladoceran assemblages in environmental reconstruction, quantitative inference models for mean July water and air temperatures were developed for the cladoceran assemblage using partial least squares (PLS) regression. The final prediction model yielded a root mean squared error of prediction (RMSEP). as assessed by jackknifing, of 1.19°C for Cladocera‐water temperature data‐set, whereas the cladoceran assemblages showed only very weak relationships to mean July air temperature. The overall results emphasize the role of physical factors in regulating species abundance and distributions in these environmentally sensitive ecotonal lakes.
Study of a sand smelt (Atherina boyeri Risso 1810) population reproducing in fresh water
Authors: Rosecchi E. , Crivelli A. J. 
Published: July 2006

AbstractA population of sand smelts, Atherina boyeri, lives in the Camargue wetland, southeast France. This study deals with the part of the population that migrates towards the Fumemorte drainage canal, flowing into the brackish lagoon, the Etang du Vaccarès. Between autumn and early spring, some sand smelts migrate from the canal into seasonally flooded freshwater marshes, where they breed, and then leave between March and July, just before the marshes dry out. The sand smelts remaining in the canal use the vegetation‐choked smaller branches of the canal for breeding. In summer, most of the sand smelts leave freshwater habitats for the Vaccarès. Male and female sand smelts reach a maximum age of 4 years (5 winters), have the same weight and show a peak in condition in spring. Breeding occurs from March to July. Sand smelts are multiple spawners and batch fecundity increases with the female size. The mean egg diameter is independent of the female length but decreases towards the end of the spawning season. Sand smelts feed mainly on zooplankton and secondarily on benthic invertebrates. Temporary marshes are richer in submerged macrophytes needed for spawning and have lower densities of fish than the canal. In these marshes, sand smelts feed on the large forms of zooplankton that develop because of the low fish abundance. The life‐history traits of this population of A. boyeri living in fresh water in Camargue indicate that this environment is not unfavourable for this species. This study showed that this species can undertake local migrations to colonize various habitats. The adaptability of A. boyeri favours its survival in very unstable Mediterranean environments.
Ontogenetic diet shifts of age‐0 smallmouth bass (Micropterus dolomieu Lacepède) in the New River, West Virginia, USA
Authors: Easton R. S. , Orth D. J. 
Published: July 2006

AbstractLarval and juvenile smallmouth bass (Micropterus dolomieu Lacepède; 8.5–85.0 mm total length (TL)) were collected from 2 sites in the New River, West Virginia, in the late spring and early summer to document diet shifts during early ontogeny. The first foods of smallmouth bass (TL = 9 mm) were primarily Chironomidae and microcrustaceans (primarily Copepoda). Other aquatic insects, primarily Ephemeroptera, became more abundant in the stomachs as TL increased. A shift in the proportions and types of prey consumed began at approximately 15 mm TL and was primarily attributed to fin development and increased mouth size. Foraging success, measured by number of prey per stomach, stomach fullness, and average prey volume was lower for first‐feeding smallmouth bass than for later life stages. Mouth width appeared to restrict the size of prey consumed by larval smallmouth bass, but the maximum prey width never approached the mouth width for fish longer than 35 mm TL.
Vertical distributions of two herbivorous cichlid fishes of the genus Tropheus in LakeTanganyika, Africa
Authors: Kohda M. , Yanagisawa Y. 
Published: July 2006

AbstractThe vertical distributions of two herbivorous cichlid fishes,Tropheus mooriiandTropheus duboisi, were studied on the rocky slope at Luhanga and Bemba, 12 km apart, in Lake Tanganyika, Zaire, Africa. At Luhanga, whereT duboisiwere not present,T. mooriiranged from the shoreline to a site 30 m deep. At Bemba,T mooriioccupied areas less than 18 m andT duboisiareas between 5 and 30 m. In the overlapping zone, 5–18 m depth, each fish held an intra‐ and interspecific feeding territory, involving size‐dependent dominance relationship between neighbors irrespective of species. We indicate that the vertical distributions of these species are restricted by competitive interactions.
Application of a cluster‐bootstrapping method for identifying the dietary patterns of fish populations
Authors: Baltanás A. , Rincón P. A. 
Published: July 2006

AbstractDietary data usually exhibit considerable statistical awkwardness and the analytical techniques commonly used in the study of fish diet suffer from various problems (especially at the intraspecific and intrapopulation levels) resulting from difficulties in group definition and pooling of data. Considering that, we advocate the use of a combination of cluster analysis and bootstrapping to identify statistically significant groups of individual predators. Both basic and extended versions of the procedure (yielding slightly different results) are outlined. We also suggest the use of detrended correspondence analysis (DCA) for further interpretation of significant clusters. When applied to dietary data from a brown trout population, the method successfully finds different feeding patterns, even though possible sources (geographical and temporal) of dietary variation were very limited. Dietary patterns appear to be related to the seasonal dynamics of the prey community coupled with seasonal shifts in microhabitat use by the predator; and, in a finer time‐scale, to diel macroinvertebrate drift periodicity or interindividual, size‐related differences in preyhandling capabilities.
Migratory behaviour of brown trout,Salmo truttaL: importance of genetic and environmental influences
Authors: Näslund I. 
Published: July 2006

AbstractLake Storvindeln in northern Sweden supports a population of fast‐growing lake‐run brown trout. Spawning and early rearing take place in the River Vindelälven, while most growth occurs in the lake (piscivory). A smaller tributary to the lake, Låktabäcken Creek, holds a resident, early maturing, short‐lived brown trout population, although no migratory barriers have existed since 1947. To establish a lake‐run trout population, fry from the migratory R. Vindelälven stock were introduced into the creek during 1985–1991. Introduced trout descended to the lake prior to maturing. As a result of the introduction, large adult trout returned from L. Storvindeln to the creek to spawn in 1991 and 1992; i. e., the introduced trout were able to complete a migratory life cycle. Genetic factors appeared to have a primary influence on the predisposition to migrate in this case, and it is suggested that migratory populations rarely develop from strictly resident ones.
Comparative growth and diet of tench Tinca tinca (L.) larvae and juveniles from river floodplain biotopes in France and England
Authors: Copp G. H. , Mann R. H. K. 
Published: July 2006

AbstractThe growth and diet of larvae and 0 + juveniles of riverine tench Tinca tinca (L.) were compared in two stagnant floodplain biotopes from the upper River Rhône, France, and the River Great Ouse, England. The diet of tench was generally similar at the French and English sites, with Cladocera being the predominant prey of young larvae (English site only). Cladocera and Copepoda were the principal prey of older larvae and 0 + juveniles, though the latter took a variety of other, larger prey items. Ontogenetic changes in diet at both sites probably reflect prey availability. Protracted spawning at the French site contrasted a single spawning effort in the English backwater. Fluctuations in growth rate and condition were observed to coincide with shifts in diet, suggesting that tench developing in riverine biotopes may be vulnerable to competition at particular transitional intervals in their early ontogeny.
Abundance estimates of perch fry (Perca fluviatilis), complicated by grouped behaviour
Authors: Kubečka J. , Švátora M. 
Published: July 2006

AbstractSchnabel's mark and recapture abundance estimates of perch fry in KliČava Reservoir (Czech Republic), differentially marked in autumn and in spring, partly failed due to the existence of groups of individuals which behaved differently. There were three groupings. 1) a group of fry caught by shore seining from autumn of the first year (O+) to summer of the second year of life (1+), the only group in the littoral during late autumn and early spring and the fry with the slowest growth rate; 2) a group of perch fry that consisted of males maturing at 1 year and that dominated the trap catches in reservoir; 3) a group of fry that avoided the littoral in late autumn and during March‐May 1983, which appeared in the littoral in May and June 1983, thus diluting the previously marked littoral fry. These 3 groupings of fry were relatively stable and separable throughout 1–2 years, apart for the mixing of groups 1 and 3 that took place in the littoral during the summer. The density of perch fry of 1982 year class in spring 1983 was estimated to be about 0.094 individuals per m2.
Substrate selection by Geotria australis ammocoetes in the laboratory
Authors: Kelso J. R. M. 
Published: July 2006

AbstractLamprey ammocoetes typically emerge from the substrate at night in their search for suitable habitat. When presented with a range in substrate depths, ammocoetes were found in deeper layers (>2.5 cm, range 1.0–7.7) of substrate and were usually in the deepest substrate. When offered a choice between 0.2 mm and any other coarser substrate, ammocoetes selected the coarser substrates in apparent contradiction with current knowledge. When offered a choice between intermediate (0.6, 0.85 mm) and coarse (1.5, 3.5 mm) substrates, ammocoetes were found in intermediate substrates. Geotria australis ammocoetes grew 0.10 mm day−1 and 0.00038 g day−1 when held in the laboratory and fed adlibitum. Survival was 90% over 154 days. Ammocoetes grew better in the laboratory on a diet of yeast and mixed plankters than in New Zealand streams and apparently selected substrate on the basis of underlying, not surficial, particle size and substrate depth.
A conceptual model for examining density dependence in the growth of stream trout
Authors: Newman R. M. 
Published: July 2006

AbstractDetermination of the occurrence and importance of densitydependent responses is central to understanding stream trout population dynamics. I propose a conceptual model of growth, based on a distribution of feeding site quality, that considers the effects of density on growth. The site quality model assumes that trout select the best feeding sites available and, as the number of trout increases, they will be forced to use less energetically profitable sites, resulting in decreased growth, but also an increase in variance of size or growth. Results from a 3‐year study of a brown trout (Salmo trutta) population show that growth to age 1 was significantly reduced for the 1981 year class, which was about 4 times more dense than other year classes. The reduction in growth was not due to a decrease in the growth of all trout but rather an increase in the number of slower growing fish. These results are consistent with my site quality distribution model and suggest that individual fish growth, the distribution of growth, and the variance of growth rates should be considered in addition to mean size and growth.
Coastal movement and growth of domesticated rainbow trout (Oncorhynchus mykiss (Walbaum)) in Norway
Authors: Jonsson N. , Jonsson B. , Hansen L. P. , Aass P. 
Published: July 2006

AbstractBetween 1979 and 1991, hatchery‐reared 1+ and 2+ rainbow trout were released in May and June in the Boknafjord at the mouth of the River Imsa, and from April to June in the Oslofjord, southern Norway. The fish were recaptured in the fjords of release, in rivers emptying there and from rivers and sea further along the Norwegian coast. Of the total recaptures, 35.6% ascended rivers in the year of release. Some fish released at the River Imsa returned to the area of release after spending 1 to 3 years at sea. Among those that were recaptured in rivers, 11.9% were recaptured in other rivers than the Imsa. The growth rate of the fish varied inversely with size at release. The growth rate was higher in the Oslofjord than in the Boknafjord, and in both areas the growth rate decreased with time after release. Rainbow trout that had escaped from local fish farms entered the River Imsa between March and December. Adults ascending in spring remained a shorter time in the river (37 days) than those ascending in autumn (200 days). Fish entering in autumn decreased more in weight during their river stay than those ascending in spring, and females more than males. Spawning took place in April‐May. The monthly mean river stay of juvenile entrants ranged from 2 weeks to 6 months. In total, 27.8% of the rainbow trout escaped from fish farms and captured in the Imsa strayed to other rivers for repeat spawning. There is no evidence for continuing survival of escaped Norwegian rainbow trout in the wild.
The effect of large‐scale spatial variation of pelagic fish on hydroacoustic estimates of their population density in Windermere (northwest England)
Authors: Baroudy E. , Elliott J. M. 
Published: July 2006

AbstractFrom July 1989 to December 1992, an echo sounder provided monthly estimates, usually for both day and night, of pelagic fish densities in the north and south basins of Windermere, the largest natural lake in England. Sampling was along contiguous transects, 3 in the north basin and 5 in the south basin. It was impossible to separate records for Arctic charr (Salvelinus alpinus) from those for brown trout (Salmo trutta), but previous sampling by gill‐nets and anglers showed that charr formed about 90% of this mixed population in the north basin and 60–75% in the south basin. In each basin, estimates of population density for the combined transects did not agree with estimates obtained by treating the transects as a contiguous sample of 9 sampling units; only the latter, of course, provided a measure of the precision of each estimate. Analyses of the contiguous samples showed that the variance was significantly greater than the arithmetic mean in most samples, indicating that the fish were distributed nonrandomly in a patchy or clumped pattern. The relationship between the large‐scale spatial variance and mean for these samples was well described by a power function; the parameter estimates did not vary significantly between basins, day and night samples or years. As the power in this equation did not differ greatly from 2 (value for pooled data was 1.70 ± 0.11, n= 136), the variance was stabilized by a log transformation of the data, and the geometric mean, rather than the arithmetic mean, provided the best estimate of population density when some measure of precision was required. These conclusions may be applicable to other echo‐sounding estimates of population abundance, and similar comparisons should be made for pelagic fish in other lakes.
Habitat selection by rainbow trout Oncorhynchus mykiss in a California stream: implications for the Instream Flow Incremental Methodology
Authors: Vondracek B. , Longanecker D. R. 
Published: July 2006

AbstractWe quantified microhabitat selection of rainbow trout (Oncorhynchus mykiss) at 2 flows (low= 1.13 m3. s−1 and high =4.95 m3. s−1) in the Pit River, California. Flows were controlled by an upstream dam and habitat availability was similar during 4 sampling periods at low flow and 2 periods at high flow. A principal components analysis reduced 6 microhabitat variables to 3 new variables that explained 80% of the observed variance. The 3 components loaded heavily on velocity variables, depth variables and substrate. Microhabitat selection generally differed among macrohabitats (i. e., pools, runs, and riffles). Rainbow trout selected different microhabitats at high flow relative to low flow in response to the availability of deeper, faster water. At low flow, depth and velocity selection were positively correlated with seasonal temperature change for adults but not juveniles. Rainbow trout apparently sought shelter in interstitial spaces in the substrate of runs and riffles during the day in early winter. Generally, large rainbow trout were observed in pools, intermediate‐sized fish in runs, and small trout in riffles. The largest fish occurred in slow, deep areas of pools, where they moved slowly without orientation to flow and were not observed feeding, whereas small fish generally faced upstream and fed in all habitat types. Foraging forays were directed up in the water column at velocities similar to the mean water column velocities at holding positions. Rainbow trout were the most abundant species in 76% of the population survey stations. Other species that might have influenced microhabitat selection by rainbow trout were uncommon.
Patterns of movement of centrarchids in two warmwater streams in eastern Tennessee
Authors: Gatz A. J. , Adams S. M. 
Published: July 2006

AbstractWe studied the movements of redbreast sunfish (Lepomis auritus), bluegill (Lepomis macrochirus), rock bass (Ambloplites rupestris), largemouth brass (Micropterus salmoides), and warmouth (Lepomis gulosus) by tagging fishes with individually numbered tags. We sampled quarterly over a 3‐year period (1985–1988) at six 800‐ to 2300‐m‐long sites in 2 streams near Oak Ridge, Tennessee. Overall, distances between successive captures were < 100 m for approximately two‐thirds of all fishes. Only rarely did we document movements over long distances; distances of 17.0‐17.6 km between successive captures were obtained for 5 fishes (1 redbreast sunfish, 1 largemouth bass and 3 bluegill), and only one other fish moved > 10 km. In general, all species were highly sedentary in both streams, with rock bass and redbreast sunfish being the most sedentary and bluegill and largemouth bass being the least. In most instances, redbreast sunfish showed the same distribution of distances between captures regardless of the interval between captures (1 week, 3 months, 6 months or more). This species also tended to be more mobile in the spring and less mobile in the winter, with large fish exibiting the greatest distances between captures. Some redbreast sunfish showed a very restricted home range, being captured 3 or more times over ≥ 6 months in the same 50‐m section of stream. A few individuals moved 4‐9 km only to return to their original location, but most fish exhibited behaviors intermediate between these extremes. For all species, upstream and downstream movements were equally common, although movements in one direction predominated at some sites for limited periods of time. Knowledge of movement patterns and differences in behavior among species is important not only in understanding the basic ecology of the species but also in designing, conducting and interpreting environmental monitoring studies.
Habitat use by an endangered riverine fish and implications for species protection
Authors: Freeman B. J. , Freeman M. C. 
Published: July 2006

AbstractWe investigated habitat specificity of the amber darter (Percina antesella Williams & Etnier 1977), an imperiled fish from restricted portions of 2 rivers in the southeastern United States. Foraging amber darters occupied a narrow range of riffle habitat, consistently avoiding areas < 20 cm deep and with velocity < 10 cm. s−1 near the substrate, occupying areas with cobble or gravel substrate and average water‐column velocity of 30 to 70 cm. s−1. During low to mo'derate flows, approximately 20% or more of the study areas contained suitable habitat for the species. Amber darters appeared rare, and the numbers of individuals were uncorrelated with the concurrent availability of suitable habitat. Protecting the amber darter may require more than maintaining adequate depths and velocities over gravel‐cobble substrates. Until we understand the potential importance of migration and dispersal for maintaining small populations, suitable habitat should be maintained over the longest contiguous stream segments possible.
Effects of stocking of piscivorous brown trout, Salmo trutta L., on stunted Arctic charr, Salvelinus alpinus (L.)
Authors: Damsgård B. , Langeland A. 
Published: July 2006

AbstractTo study the effects on a stunted freshwater population of Arctic charr, Salvelinus alpinus (L.), two groups of large (26–45 cm) individually tagged brown trout, Salmo trutta L., were released and recaptured with gillnets after 1, 7, 11 and 63 weeks. One group of trout was trained on a fish diet before release, and the other, reared on commercial dry pellets, served as a control. Specific growth rates in both groups were negative 1 week after release and approached zero after 63 weeks. Condition factor and internal fat content decreased during the experiment. Although only 11% of the trout stomachs examined contained fish prey, charr represented 79% of the total stomach weight content. Gillnet samples of charr before and 63 weeks after the release of trout indicated a decreasing population size of charr. Individual growth and mean length of charr increased after release of trout, especially for charr at age 4 years. After the release of trout, 35% of the charr were longer than 20 cm as compared with 6% before the release.