Multiple factors determine the effect of anthropogenic barriers to connectivity on riverine fish

Habitat fragmentation is a key anthropogenic factor in biodiversity decline, particularly in aquatic ecosystems. We predicted that differences in fish assemblage composition due to the impact of fragmentation would most strongly affect migratory species, and these effects would be dependent on the interaction between the characteristics of each barrier and the antecedent flow conditions that determine temporal variation in connectivity. These hypotheses were applied to a coastal river network in eastern Australia that is fragmented by multiple weirs and dams, including some with passage facilities. How these facilities interact with flow to mediate hydrological connectivity and hence patterns of community structure is unknown. Five distinct assemblages were identified that were associated with different combinations of environmental factors and barrier characteristics (spatial arrangement, passability), and key differences were due to variation in migration traits. Two spatially distinct assemblages were associated with fragmentation by two impassable barriers. However, the migration traits that accompanied these community changes were inconsistent between these groups, and likely reflected effects of barriers near the estuary and in the middle of the stream network on diadromous and freshwater-migratory species, respectively. Two assemblage groups in the vicinity of passable weirs varied temporally as a function of hydrology and the seasonal upstream movement of juvenile diadromous species. The effect of habitat loss in conjunction with fragmentation was evident, with a further assemblage group occurring in reaches where riparian vegetation and instream habitat have been altered by poor management of agriculture. This study indicates that the impact of habitat fragmentation in rivers depends on the interaction of the migration characteristics of biota, temporal variation in hydrology which mediates connectivity, and the location of anthropogenic barriers. Conservation policies aimed at minimizing human impacts on aquatic biodiversity need to jointly account for the separate impacts of habitat fragmentation and habitat loss.     

Molecular identification methods of fish species: reassessment and possible applications

Fish species identification is traditionally based on external morphological features. Yet, in many cases fishes and especially their diverse developmental stages are difficult to identify by morphological characters. DNA-based identification methods offer an analytically powerful addition or even an alternative. This work intends to provide an updated and extensive overview on the PCR-methods for fish species identification. Among the ten main methods developed, three PCR-RFLP, PCR-FINS and PCR-specific primers have been the most used. Two other emerging methods, namely real-time PCR and microarray technology, offer new potential for quantification of DNA and simultaneous detection of numerous species, respectively. Almost 500 species have been targeted in the past decade, among which the most studied belong to gadoids, scombroids, and salmonids. The mitochondrial cytochrome b gene was by far the most targeted DNA markers. The most common applications belonged to the forensic, taxonomic, and ecological fields. At last, some key problems, such as the degradation of DNA, the reliability of sequences, and the use of scientific names, likely to be encountered during the development of molecular identification methods are described. In conclusion, the tremendous advances in molecular biology in the past 10 years has rendered possible the study of DNA from virtually any substrates, offering new perspectives for the development of various applications, which will likely continue to increase in the future.     

Use of hair tubes to survey for shrews: new methods for identification and quantification of abundance

• 1 Accurate and sensitive survey and monitoring methods are needed for shrews. We present a new design of hair tube and a new, simple method of species identification from multivariate analysis of four parameters measured from shrew guard hairs using a binocular microscope with incident light.
• 2 Multivariate analysis of these parameters measured from hairs of known identity showed that they can be used to identify hair to the species level with 85% accuracy.
• 3 We compared our indices of abundance from hair tubes (the hair tube index) with those from live trapping in 40 field margins. Capture‐mark‐recapture methods showed that capture rate did not vary systematically across sites, so that number of individuals captured was used as an index of abundance.
• 4 The hair tube index showed a significant association with the number of individuals captured for Sorex araneus and Neomys fodiens. The lack of a significant association for Sorex minutus may be because hair tubes are more sensitive in detecting this species than live trapping.
• 5 Hair tubes have additional advantages over live trapping, since they do not require frequent checking, are much lighter and cheaper than live traps, and no licence is required for their use in the UK. We therefore recommend consideration of their use in future surveys and monitoring studies of shrews. We provide an equation so that other researchers can use our multivariate method.

     

Predator complex of the horse chestnut leafminer Cameraria ohridella: identification and impact assessment

Abstract:  The control of Cameraria ohridella Deschka and Dimic (Lepidoptera, Gracillariidae) by natural enemies in Europe is poor. Thus, in the past 15 years epidemic population densities of the moth regularly caused a continuous pre-mature defoliation of horse chestnut trees, Aesculus hippocastanum L.. Whereas several studies investigated the parasitoid complex of the leafminer and revealed its inefficiency, only little is known about the predators of C. ohridella . The aim of this study was to identify the predator complex in European horse chestnut stands by visual observations and exposure experiments and to assess the impact of different predator guilds on C. ohridella populations by an exclusion experiment. Of all potential predators observed, only blue tits, Parus caeruleus L., great tits, Parus major L., marsh tits, Parus palustris L. and the southern oak bushcricket Meconema meridionale (Costa) were found to prey on the pre-imaginal leafminer stages. Bushcrickets have to our knowledge never before been recorded preying on leafminers; moreover M. meridionale showed a measurable negative impact on the C. ohridella population. However, birds seem to be of greater importance as predators of C. ohridella than arthropods. Predation rates of birds ranged from 2 to 4% of leafminer populations, which is of the same order of magnitude as published parasitism rates. We conclude that the augmentation of tit densities, for example via nesting boxes in chestnut trees, should be considered as a component of an integrated control strategy against the horse chestnut leafminer.     

Predicted impact of barriers to migration on the Serengeti wildebeest population

The Serengeti wildebeest migration is a rare and spectacular example of a once-common biological phenomenon. A proposed road project threatens to bisect the Serengeti ecosystem and its integrity. The precautionary principle dictates that we consider the possible consequences of a road completely disrupting the migration. We used an existing spatially-explicit simulation model of wildebeest movement and population dynamics to explore how placing a barrier to migration across the proposed route (thus creating two disjoint but mobile subpopulations) might affect the long-term size of the wildebeest population. Our simulation results suggest that a barrier to migration--even without causing habitat loss--could cause the wildebeest population to decline by about a third. The driver of this decline is the effect of habitat fragmentation (even without habitat loss) on the ability of wildebeest to effectively track temporal shifts in high-quality forage resources across the landscape. Given the important role of the wildebeest migration for a number of key ecological processes, these findings have potentially important ramifications for ecosystem biodiversity, structure, and function in the Serengeti.     

Research progress on gut health of farmers teleost fish: a viewpoint concerning the intestinal mucosal barrier and the impact of its damage

Reviews in Fish Biology and Fisheries - The intestinal mucosal barrier plays a critical role in the maintenance of host health. In farmed teleost fish, the intestinal epithelium is challenged by a...     

Estimation of growth hormone secretion rate: impact of kinetic assumptions intrinsic to the analytical approach

We compared four common mathematical techniques to determine daily endogenous growth hormone (GH) secretion rates from diurnal plasma GH concentration profiles in 24 women (16 upper- or lower-body obese and 8 normal-weight individuals). Two forms of deconvolution analysis and two techniques based on a priori determined GH clearance estimates were employed. Deconvolution analyses revealed significant differences in the 24-h GH secretion rate between normal-weight and upper-body obese women, whereas the other two techniques did not. Moreover, deconvolution analyses predicted that the reduction in mean plasma GH concentrations in upper-body obese women was accounted for by impaired GH secretion, whereas the other methods suggested that obesity increases GH metabolic clearance. Thus we infer that disparate conclusions concerning GH secretion can be drawn from the same primary data set. The different inferences likely reflect dissimilar kinetic assumptions and the particular limitations intrinsic to each analytical approach. Accordingly, we urge caution in the facile comparison of calculated GH secretion data in humans, especially when kinetic and secretion measurements are performed under different conditions. The most appropriate way to determine the GH secretion rate in humans must be balanced by the exact intent of the experiment and the acceptability of different assumptions in that context.     

Depauperate freshwater fish communities in Sabah: the role of barriers to movement and habitat quality

Up to 30 species of fish were generally found in medium-sized rainforest streams in Sabah, Malaysia. However, depauperate fish communities were found in two streams above large (>8 m) waterfalls (five and nine species) and in two very small streams located in deep forest (five and six species). A fifth stream with small cascades and waterfalls had a faunal list of 12 species. Species resident above waterfalls were predominantly herbivores while fishes in the two forest streams were from a variety of trophic groups. Abundance and biomass of fishes above waterfalls were significantly lower than all other sites. A translocation experiment was performed in one stream to distinguish between the hypotheses that fish communities above waterfalls were determined solely by colonization ability and were unsaturated with species or that they were limited by habitat quality or food. Seven species (775 individuals) were trans located into one isolated section and four species (570 individuals) into another. Species that were trans located included trophic groups that were not represented by resident species. Twelve months after translocation, only four and one trans located species were collected in the two sections, all at greatly reduced densities. After 20 months, the number of species were three and two, respectively. One trans located species, Rasbora sumatrana , had increased in abundance from 12 months and juveniles were present in the population. Individuals of other trans located species appeared to be remnants of stocked populations. Abundance and biomass of resident species fluctuated widely between years. Interpretation of results was complicated by a large flood which substantially changed habitat conditions about a month after translocations were performed. It is suggested that two different factors were responsible for depauperate communities: movement barriers for waterfall sites and physicochemical conditions and/or habitat availability at other sites.     

Protocol for the assessment of mortality and injuries in fish larvae associated with their downstream passage through hydropower dams

Reviews in Fish Biology and Fisheries - Migratory fishes are one of the groups most threatened by the interruption of river connectivity caused by reservoirs and dams. The downstream displacement...     

Constraints on recovery: using molecular methods to study connectivity of aquatic biota in rivers and streams

1. The ‘Field of Dreams Hypothesis’ states ‘if we build it, they will come’, referring to the assumption that if habitats are restored, species will recolonise them. However, the ability of a species to recolonise a restored site will depend not only on the appropriate habitat being present, but also on the ability to get there. This is likely to depend on both the species’ dispersal behaviour and the position of a site in the landscape. 2. Animals with good potential for dispersal are more likely to be able to disperse to newly restored sites. Similarly, sites in lowland streams with limited altitudinal differences between sites may be easier to reach than upstream sites. This is because upstream sites are connected to one another via lowland streams that have different characteristics and therefore may be difficult for animals to traverse. 3. In this paper, genetic data from a range of freshwater species that have been analysed in my laboratory are used to assess the importance of life cycle and position in the landscape (i.e. upland versus lowland streams) on connectivity patterns (and thus recolonisation potential) among populations. 4. In general, contemporary dispersal across catchment boundaries is negligible, except for aquatic insects with an adult flight stage. Dispersal among streams within catchments appears to be more limited than was predicted from knowledge on life histories, except for fish in lowland rivers and streams. 5. As predicted, dispersal of fish, crustaceans and molluscs among streams within catchments is significantly greater in lowland rivers than in upland streams. 6. Overall, these analyses suggest that, with the exception of most insects, and fishes in lowland rivers, natural recolonisation of restored sites is only likely from sites within the same stream. If a species has disappeared from the whole stream, then restoration of habitat alone may not be sufficient for its re‐establishment.     

Influence of turbidity and passage rate on the efficiency of an infrared counter to enumerate and measure riverine fish

This study aimed to ascertain the influence of turbidity and migration rate on the count accuracy and size determination of an automatic infrared fish counter. The effect of turbidity on enumerating silver perch (Bidyanus bidyanus) migration rates was insignificant when compared to the inability of the infrared counter to deal with large numbers of migrating fish. The infrared counter underestimated counts by 56–84% at moderate migration rates (12 fish h^?1) and by 62–82% at the highest migration rate (120 fish h^?1). When multiple fish were simultaneously passed through the counter, the software detected them as a single fish and overestimated fish length. Fish passed through the unit ranged from 340 to 520 mm but the infrared counter estimated the range to be 140–780 mm, with the lengths of a high proportion of individuals being underestimated. Most issues of inaccuracy appeared to be software‐related and could be overcome with further software development. Further assessment of the applicability of the unit to enumerate fish migration, at high migration rates, should then be considered.     

The ECVAM workshops: a critical assessment of their impact on the development,validation and acceptance of alternative methods

ECVAM initiated its workshop programme in 1994, to enable it to become well informed about the state of the art of non-animal test development and validation, and about the possible incorporation of alternatives into regulatory requirements for safety testing. Fifty-one such workshops have been held on specific topics, up to 2002. In these workshops, the current status of in vitro tests and their potential uses were reviewed and recommendations were made as to the best ways forward to progress and enhance the utilisation of in vitro methods. Reports for 46 of these workshops have been published in ATLA. Most of the workshops focused on in vitro replacement methods, although an increasing number have dealt with reduction and refinement. The recommendations in the ECVAM workshops have been progressed further by: a) the formation of ECVAM task forces; b) the organisation of further workshops; c) the activities of scientific committees; d) the provision of earmarked research funding; and e) the conduct of validation studies. Examples of each of these activities are discussed. Some individual workshops are covered in more detail and several recommendations that have so far not been acted on are also considered. The workshops and their reports have had a substantial effect on the development and implementation of alternative methods, and have been a major factor in contributing to the success of the first nine years of ECVAM's existence. It is strongly recommended that ECVAM continues to organise workshops and to publish their findings, and several suggestions are made for topics of future workshops.     

Step-by-step social life cycle assessment framework: a participatory approach for the identification and prioritization of impact subcategories applied to mobility scenarios

The International Journal of Life Cycle Assessment - Investigating potential social and socio-economic impacts should play a key role for the development of sustainable mobility alternatives....     

Relationship of fish and macroinvertebrate communities in the mid-Atlantic uplands: Implications for integrated assessments

Indices developed for stream bioassessment are typically based on either fish or macroinvertebrate assemblages. These indices consist of metrics which subsume attributes of various species into aggregate measures reflecting community-level ecological responses to disturbance. However, little is known about the relationship between fish and macroinvertebrate metrics, or about how ecological health assessments are affected by assemblage-specific responses to disturbance. We used principal component analysis (PCA) and regression analysis of existing fish (n = 371) and macroinvertebrate (n = 442) stream bioassessment data from a multi-source dataset to determine broad scale, within-assemblage metric patterns, and to examine the intercorrelation of fish and macroinvertebrate metrics (n = 246) and their response to watershed area and land use/land cover gradients. Fish and macroinvertebrate metrics expressed as principal components (PCs) accounted for 72.4 and 85.4% of dataset variance, respectively, with PC-metric patterns reflecting aspects of stream impairment including water and habitat quality. Model components predicting fish metric response differed among fish PCs, with watershed area and macroinvertebrate metric response strongly correlated with the first fish PC, and remaining fish PC models consisting of watershed area, land use, and macroinvertebrate PCs. Correlation between fish and macroinvertebrate PCs, and models relating fish and macroinvertebrate PCs generally explained less variation (13–27%) than metric response models of fish (25–34%) and macroinvertebrates (8–38%) to watershed area and land use/land cover variables. Best-response models integrating fish and macroinvertebrate PCs, watershed area, and land use/land cover variables accounted for the greatest variation in fish PCs (32–50%) across sites. Because fish and macroinvertebrate metrics provide different information on ecological condition, integrated use of information from multiple groups may be appropriate when developing monitoring programs.     

Improved high-performance liquid chromatographic method for the separation and quantification of lipid classes: application to fish lipids

An improved straight-phase HPLC method for the separation and quantification of lipid classes is described. Two binary gradient solvent systems were used, one for polar and one for neutral lipids, and detection was performed with a light-scattering detector. The developed HPLC methods were highly reproducible and allowed base-line separation of all investigated polar lipid classes (phosphatidic acid, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, sphingomyelin, phosphatidylserine, phosphatidylinositol and lysophosphatidylcholine) and neutral lipid classes (triacylglycerol, free fatty acid, diacylglycerol, cholesterol and monoacylglycerol) except of cholesterol ester and wax ester. Application of the chromatographic systems demonstrated that the methods are suitable for quantitative analysis of the major lipid classes present in lipid extracts from livers and eggs of Atlantic salmon (Salmo salar).