We assessed the xtent of temporal variation and autocorrelation in fish habitat use based on an experimental study of individual 0+ juvenile barbel, Barbus barbus, in an artificial flume. Five treated and five control fish were individually subjected to an increase in discharege (intervention) hlfway through each experiment and kept at baseline discharge throughout, respectively. Preference surves for velocity were generated for each of 60 trials per experiment and for each combination of treated/control (fish) x before/after-intervention. There were large between- and within-individual differences in velocity preference, both in treated and in control fish. Most barbel explored the entire range of velocities, whereas some individuals used a more limited range. Temporal variation in behavioural responses was assessed by a PCA-based methodology. Autocorrelation (i.e. correlation between sequential trials) was diagnosed in most response profiles, supporting recent fidings that individuals may have a "memory" of their past velocity usage. The relevance of the results for numerical habitat models of fish habitat assessment is discussed, as well as the importance of incorporating temporal variability into fish habitat use models (e.g. PHABSIM), not only as ontogenetic intervals but also as longitudinal data of individual behaviours. A warning is also re-issued about the erroneous belief of "pseudoreplication" simly arising from repeated measurements in time.
Habitat use of introduced pumpkinseed Lepomis gibbosus in small European streams has received little study despite the species’ potential associations to native fauna of conservation and angling amenity, e.g. brook lamprey Lampetra planeri, European bullhead Cottus gobio, brown trout Salmo trutta. We examined body size, relative body condition, habitat use and species-species associations of pumpkinseed with accompanying fishes in two small streams in southern England during August 2001. Pumpkinseed body condition decreased with pumpkinseed density; the latter correlated with % clay and % riparian grasses in fish 92 mm FL. Most pumpkinseed size classes occurred more often than expected in stretches with conspecifics and with brown trout >300 mm FL; densities of the latter did not correlate with any habitat variables. Indeed, correlations between trout densities and habitat variables were observed mainly in smaller size classes. Habitat associations in other species corresponded to known levels of rheophily; substratum, channel slope, channel width and riparian trees were also important habitat variables. Pumpkinseed dispersal and establishment under conditions of climatic change, which could have ecological and management ramifications, are discussed.
Biometric relationships between bone dimensions and body size are presented for topmouth gudgeon Pseudorasbora parva and sunbleak Leucaspius delineatus, two invasive fish species in the UK. This study also provides a tool for identification of these species using key bones. Such information facilitates the assessment of the potential role of these invaders in the diet of piscivorous fauna.
e determined regression relat ionships between head bone lengths and body size (standard length and weight) in chub Leuciscus cephalus and Eurasian perch Perca fluviatilis, two species taken frequently by the otter in the River Lee catchment. All relationships yielded significant linear equations, whereas those for bone vs. body weight were logarithmic. Regression slopes for head bones do not differ greatly within species but do across species of the same family.
We examined the relative growth of threespine sticklebacks collected from 11 lowland streams in southeastern England during late autumn to test for between-catchment variations as well as development-related shifts in morphology. And, to understand better the sympatric relationship between threespine Gasterosteus aculeatus and ninespine Pungitius pungitius sticklebacks in small lowland streams, we compared growth variability in 35 mensural characters and morphological indices related to functional morphology in adults from one of these sites. Threespine demonstrated great plasticity, with some morphological differences observed between stream catchments, mainly in ventral spine and dorsal spine length, pre-anus and preanal distances, fin depth, and ventral body width (represented in the basipterygium medial plate width). Developmentally, three groups of mensural characters were found: 18 characters best explained by a linear regression (isometric growth), 9 characters best explained by a quadratic equation (gradual allometry), and 8 characters best explained by a split-linear regression (mainly isometric growth, with an abrupt shift in proportional growth – between 40 and 58 mm SL). However, these shifts did not appear associated with common ecological, physiological and/or behavioural functions. Compared with ninespine stickleback, threespine has a more robust body with stronger and more prominent spines, shorter tail, and eyes situated more backwards. Functional morphological indices suggest threespine to be a slower but more manoeuvrable swimmer than ninespine, which acquires a relatively more cruiser-form shape with reduced drag and more lift.
Fecundity and growth allocation to reproduction were investigated in stream-dwelling threespine Gasterosteus aculeatus L. (leiurus) and ninespine Pungitius pungitius (L.) sticklebacks of St. Ippollitts Brook, Hertfordshire (England), between August 1993 and October 1994. We compared oocyte size distributions as well as the relative fecundity of females containing mature oocytes, compared growth allocation to gonadal growth and overall reproductive allocation from estimates of total egg supply, the number of reserve oocytes eventually spawned, the proportion of reserve oocytes not spawned, the total number of oocytes spawned, and the number of egg clutches per season. Notable differences in reproductive strategy were observed between the two species. Ninespine sticklebacks were smaller in size than threespine, but compensated for this through a smaller size at first maturity, an almost equal seasonal fecundity (number of spawned oocytes) accompanied by a higher number of unspawned oocytes (i.e. maintenance of a low mature-to-total oocyte ratio), an extended spawning period, a higher number of clutches, and an overall lower reproductive allocation.
The pumpkinseed Lepomis gibbosus, an omnivorous, nest guarding North American sunfish, was introduced into European waters about 100 years ago. To assess growth performance following introduction, we reviewed the available data for North American and European populations of pumpkinseed and compared the back-calculated age-specific growth for juveniles (standard length, SL, at age two) and adults (age two to five increment) as well as adult body size (SL at age five), von Bertalanffy growth model parameters and the index of growth (in length) performance (φ′). For continental comparisons of growth trajectory, mean growth curves for North American and Europe were calculated with the von Bertalanffy model using pooled data sets for each continent. Juvenile growth rate did not differ between European and North American pumpkinseed, but mean adult body size and adult growth rate were both significantly greater in North American than European populations. Adult body size decreased with increasing latitude (ANOVA) in North American populations, but this was not observed with adult growth rate. In contrast, adult body size tended to increase with latitude in European populations. Adult body size correlated significantly with φ′. The von Bertalanffy model described the overall growth patterns of North American and European populations reasonably well, but on the individual population level, length asymptotes were unrealistic (estimates that were > 20 % of the mean back-calculated size for the oldest age class) for a third of European populations and 80% of the North American populations. In contrast to North American pumpkinseed populations, somatic growth in European populations appears to be compromised by limited, but adequate, food resources, probably due to strong intraspecific interactions. This appears to be especially acute in adults, having potential ramifications for life span and reproductive allocation.
Microhabitat use in the endangered cyprinid species spirlin Alburnoides bipunctatus and accompanying species was examined in three water courses of Slovakia to determine the species’ environmental requirements as a basis for informing conservation policy and management. In all three rivers, water velocity, water depth and substratum character were central features of spirlin microhabitat use, regardless of year or season of sampling, with only limited variation in microhabitat associations as a function of time of day. Clear differences in microhabitat use and intra-specific associations during development were observed in two of the rivers. In particular, a shift in velocity preference towards faster flowing waters appears characteristic of spirlin during their larval and juvenile development, and possibly also that of gudgeon Gobio gobio, European minnow Phoxinus phoxinus, and chub Leuciscus cephalus, which are all species that may be significantly associated with young spirlin. Disproportionate use of deeper waters tended to increase with age in spirlin, and in gudgeon and barbel Barbus barbus, but spirlin preference for substratum was less uniform, with affinities ranging from indifference to strong preference. This contrasts the clear preferences for sand in gudgeon and for cobbles in European bullhead Cottus gobio. Of particular importance to young-of-the-year (YOY) spirlin are lentic zones with some sort of ligneous debris – habitat also used by YOY gudgeon and minnow. Contrary to previous reports elsewhere, spirlin did not avoid in-stream vegetation where present, and in one river it was preferred by YOY and 1+ spirlin. To avoid declines in spirlin and accompanying stream-dwelling species, such as reported elsewhere in Europe, river management in water courses such as these should be limited to the rehabilitation of regulated sections to achieve a natural, heterogeneous channel character.
We studied movement and abundance of barbel, Barbus barbus , over three years (October 1995 to September 1998) in two stretches (Woolmer’s Park, Holwell Bridge) of a section of the River Lee (Hertfordshire, England) delimitated by water retention structures. Of 349 tagged individuals (168 at Woolmer’s Park; 181 at Holwell Bridge), 51.8 % and 13.3 % respectively were recaptured at least once, with a much higher rate of multiple recaptures at Woolmer’s Park, where monitoring of movements was over a longer period, than at Holwell Bridge, where too few recaptures were made for further movement analysis. At Woolmer’s Park, 77.1 % of the barbel showed limited (i.e. resident component) and the rest greater between- capture movements (i.e. mobile component). There was no preferential directional movement across size classes. Based on the available recapture data, population size (estimated through a Bayesian method) first increased moderately (1995–96) and then sharply (1996–97) at Woolmer’s Park, and even further later at Holwell Bridge (1998–99). This may reflect a recovery phase in the local population, or possibly a rising part of a cyclic recruitment pattern, such as reported for barbel elsewhere and for other cyprinids in the UK. Habitat enhancement is recommended over stocking, given the adequate abundance of barbel in areas with suitable habitat. However, it remains unclear whether fencing-off of the banks from livestock will enhance 0+ barbel numbers, which appear to be low relative to some European rivers of similar width and depth.
Research in freshwater ecology has traditionally focused on water courses or large still waters. However, ponds support proportionately high levels of biodiversity relative to other inland waters in Europe, and foraging by Eurasian otter Lutra lutra (L., 1758) could have considerable impacts on species composition in these small water bodies. The aim of the present study was to analyse otter spraints around ponds during two contrasting seasons (winter and spring) in north Norfolk (eastern England), where both otter and ponds are of particular conservation concern. Spraint density, prey diversity and the consumption of river-associated species were higher in spring than winter. In both seasons, birds were the most important prey category as ingested biomass. European eel Anguilla anguilla (L., 1758) and amphibians, specifically common frog Rana temporaria L., 1758 and common toad Bufo bufo (L., 1758), were more consumed in spring, whereas northern pike Esox lucius L., 1758 and tench Tinca tinca (L., 1758) were taken in winter. Non-native common carp Cyprinus carpio L., 1758 was important in both seasons, whereas threatened native crucian carp Carassius carassius (L., 1758) was a minor prey item. Massive kills of common toad, which involved a new handling technique for predation on this species, were observed mainly in spring. The study demonstrated otters to display great plasticity in foraging behaviour and contributes to the
understanding of otter predatory pressure on pond biodiversity, with implications for landscape management.