SHARK ATTACKS ON BOTTLENOSE DOLPHINS (TURSIOPS ADUNCUS) IN SHARK BAY, WESTERN AUSTRALIA: ATTACK RATE, BITE SCAR FREQUENCIES, AND ATTACK SEASONALITY

Shark predation may have been a central factor influencing the evolution of sociality in dolphins, as well as a determinant of dolphin habitat use and behavior. To understand the role of predation in driving interpopulation differences in behavior and sociality, it is important to quantify differences in predation risk among populations. This study describes the frequency of shark-inflicted scars and estimates the shark attack rate on bottlenose dolphins ( Tursiops aduncus ) in Shark Bay, Western Australia. Shark bite scars were found on 74.2% (95 of 128) of non-calves, and most of these scars were inflicted by tiger sharks ( Galeocerdo cuvier ). Although there were no differences among age/sex classes in the frequency of scarring, significantly more adult males than adult females bore multiple scars. The rate of unsuccessful shark attack was estimated to be between 11% and 13% of dolphins attacked each year. Large sharks (>3 m) were responsible for a disproportionate number of attacks. However, bites from small carcharhinid sharks on 6.2% of dolphins suggest that some of these small sharks may be dolphin ectoparasites. Both the scar frequencies and attack rate suggest that Shark Bay dolphins face a greater risk of predation than bottlenose dolphins in other locations.     

The Rove Beetles (Coleoptera, Staphylinidae) of Exposed Riverine Sediments in Scotland and Northern England: Habitat Classification and Conservation Aspects

Exposed riverine sediments (ERS) by four rivers in Scotland and northern England were sampled for beetles in 1996 and 1997. One hundred and sixty rove beetle (Staphylinidae) species lists were analysed using ordination and classification techniques in order to identify habitat groups within and between catchments and to assess which factors were affecting species assemblage distribution. There were major differences between the species assemblages of ERS by rivers of highland and lowland catchments. Within catchments, assemblage distribution was mainly influenced by the position of sites within the catchment; vegetation cover and sediment composition had less influence. The number of rove beetle habitats was not the same as those for ground and phytophagous beetle groups, indicating that conservation considerations should take into account variations in ERS habitat diversity. A considerable number of records of nationally rare and scarce rove beetle species were recorded, most on ERS by rivers and tributaries unaffected by river management or engineering.     

Relative contributions of sexual and asexual regeneration strategies in Populus nigra and Salix alba during the first years of establishment on a braided gravel bed river

Populus nigra L. var betulifolia and Salix alba L. var alba are early successional riparian tree species threatened throughout Continental Europe by significant changes to the natural physical processes governing their natural habitat – geomorphologically active floodplains. River management activities have dramatically altered natural patterns of river flow and rates of sediment delivery along rivers, with possible consequences for the balance between sexual and asexual regeneration strategies in these species. Conservation strategies will benefit from a greater understanding of the ways in which dynamic physical processes on the floodplain influence sexual and asexual recruitment. This paper describes a field survey investigating the relative abundance and spatial distributions of P. nigra and S. alba sexual and asexual recruits during the first years of establishment along a braided gravel bed river. Sexual and asexual recruits were identified by excavation along transects in a wet and a dry field season and distributional differences were described in terms of elevation on the floodplain, local sediment type and exposure to floodwaters. Regeneration was overwhelmingly from seed in the first 2–3 years following recruitment, but poor survival rates among sexual recruits saw a shift in the relative abundance of regeneration strategies over time. In relating hydrological data to recruitment, unseasonal flood disturbances had a negative effect on recruitment from seed and a positive effect on vegetative regeneration. Seedlings were associated with fine sediment deposits and were restricted primarily to low elevations on the flood plain, while asexual recruits had a wider spatial distribution. Certain microsite types were unique to either regeneration strategy.     

Current and historical patterns of drainage connectivity in eastern Australia inferred from population genetic structuring in a widespread freshwater fish Pseudomugil signifer (Pseudomugilidae)

Dispersal can play an important role in the genetic structuring of natural populations. In this regard, freshwater fishes often exhibit extensive population genetic subdivision and are ideal subjects for investigating current and historical patterns of connection and dissociation between drainages. We set out to generate a comprehensive molecular phylogeny for a widespread freshwater fish from eastern Australia, the Pacific blue-eye Pseudomugil signifer. Although movement via flood events may be important in the southern end of the species' range, genetic structuring revealed the importance of historical drainage connections and dissociations in mediating or disrupting dispersal. A dominant feature of our phylogeny is a split between northern and southern populations, which appears to be congruent with a biogeographical barrier recently implicated as important for the connectivity of freshwater organisms in eastern Australia. The extent of the split also has taxonomic implications consistent with suggestions that the Pacific blue-eye may represent more than a single species.     

Primary structure of alpha-globin chains from river buffalo (Bubalus bubalis L.) hemoglobins

Primary structure analysis of the four river buffalo -globin chains showed that haplotypes A and B differ from each other by a substitution at codon 64 that may encode Ala or Asn. The A haplotype encodes two -globin chains, ^I1 and ^II3, which differ at positions 129 and 131: ^I1 has 64 Ala, 129 Phe, 131 Asn; ^II3 has 64 Ala, 129 Leu, 131 Ser. The B haplotype encodes two -globin chains, ^I2 and ^II4, which differ at positions 10 and 11: ^I2 has 10 Ile, 11 Gln, 64 Asn; ^II4 has 10 Val, 11 Lys, 64 Asn. Apart from the Ala/Asn polymorphism at position 64, amino acid substitutions in allelic and nonallelic -globin chains seem to have arisen by single point mutations. Detection of electrophoretically silent mutations due to neutral amino acid substitutions and their influence on the isoelectric point are discussed. Furthermore, primary structures of river buffalo -globin chains are compared to other species of the Bovidae family to suggest evolutionary events that have characterized the amino acid substitutions of river buffalo hemoglobin.     

Short Term Effects of Tucuruí Dam (Amazonia, Brazil) on the Trophic Organization of Fish Communities

A dam on a river course induces numerous changes in the aquatic environment both in the newly formed reservoir and in the river downstream. These changes modify the food resources available to fishes. As a consequence, fish communities undergo rapid transformations particularly in terms of trophic organization. Tucuruí Dam, closed on the Tocantins River, Brazil, in September 1984, formed a large reservoir of approximately 2200km². Analyses of fish stomach contents were performed before and after the completion of the dam in the downstream section of the river as well as in the reservoir. Resource availability was seen through the relative contribution of food items in supporting the biomass. Main changes caused by the dam consisted of an increase in fishes as a food resource and of a parallel decrease of sediment both in the reservoir and in the downstream part of the river. In addition, in the downstream section, the relative contribution of plankton as a food resource diminished after dam closure. We identified 8 feeding regimes before dam closure. From them the trophic structure of fish communities were established and compared. Most of the community biomass was from specialist feeders. Contribution of piscivores increased after closure; planktivores became unimportant after closure downstream. Some species were shown to change their diet in the transformed environments either downstream or in the reservoir. However, these changes in individual species diet did not seem to play a major role in the transformation of trophic structure of the fish communities.     

Use of a genetic marker to examine genetic interaction among subpopulations of pink salmon (Oncorhynchus gorbuscha)

In 1979 and 1981, a genetic marker was bred into one of the five identifiable subpopulations of pink salmon [Oncorhynchus gorbuscha (Walbaum)] in the Auke Lake drainage in Southeast Alaska. As a result of the marking effort, the frequencies of two malate dehydrogenase (MDH-B1, 2^*) alleles were changed in the marked subpopulation, but not in other subpopulations that spawn at different times or places. Between 1983 and 1989, the marker allele frequencies were monitored in many of these subpopulations and in early- and late-run pink salmon spawning in nearby Waydelich Creek, located approximately 1km away. Changes in allele frequencies at MDH-B1, 2^*, used to obtain direct estimates of average migration rates (m) from the marked to the unmarked subpopulations, revealed little or no introgression into early subpopulations or into nearby Waydelich Creek. Moreover, spatially distinct late-run Auke Creek subpopulations were not immediately overrun by the more abundant marked subpopulation. These observations suggest that genetic isolation exists between temporally distinct spawning runs and that small temporal and spatial (or ecological) differences contribute to population structure. These observations should be considered in taking actions that affect conservation and harvest management or extensive culture of salmonids.     

The role of phytoplankton in pollutant transfer processes in rivers. Example of River Marne (France)

The impact of the spring phytoplanktonic blooms on the partition of nutrients and metals between the dissolved and particulate phases was studied over two years in the river Marne, upstream of its confluence with the river Seine. Particular attention was devoted to copper and manganese, determined in the dissolved phase (< 0.22 m), subdivided into the colloidal phase and the 'truly dissolved' phase (< 10 KDaltons) obtained by tangential ultrafiltration. During the algal growth peaks, a sharp reduction of nutrients was observed in the dissolved phase: in 1994, consumption of 70% of silica, 50% of ammonium and 40% of soluble phosphorus present before the phytoplanktonic bloom.The water concentration peaks of suspended matter (SM) and of particulate metals, phosphorus and carbon coincide with those of chlorophyll. The highly significant correlations between pH and chlorophyll (r = 0.92, P < 0.001), pH and SM (r = 0.97, P < 0.001) and chlorophyll and SM (r = 0.93, P < 0.001) confirmed the phytoplanktonic nature of SM and the determining role of pH in the partition of metals, its increase being responsible for the coprecipitation of metal. As a corollary to the increase in the particulate phase, a decrease of 55% was observed for copper and manganese in the 'truly dissolved' phase compared to the concentrations outside bloom periods.The importance of the colloidal fraction was also shown. During the strong algal growth periods, the proportion of 'colloidal metal' in the dissolved phase (< 0.22 m) reached 60% and the increase in the colloidal fraction was 4 times stronger for copper than for manganese. While manganese seemed to be more associated with macroparticles, copper was more associated with fine colloidal biological particles intrinsic to the phytoplankton.     

The Importance of Ecoregion Versus Drainage Area on Fish Distributions in the St. Croix River and its Wisconsin Tributaries

Aquatic ecoregions, based on regional landscape features, have been proposed as a model for aquatic resource management. The model assumes the existence of a typical biota associated with a given ecoregion and serves as the basis for biological assessment, reference site designation, and determination of stream potential, based on this biotic assemblage. Contrasting models for predicting stream ecosystem structure focus on the importance of local site conditions, including the regular and predictable changes that occur as a function of area draining to a site. In this study, a classification of 429 stream sites over an area of approximately 20000km² in the St. Croix River basin delineated three major species groups: redhorse/spotfin shiner; brook charr/sculpin; and mixed species. Numerical analyses revealed no relationship between the species communities and ecoregions. In contrast, there was a strong association between the species communities and the area draining to the site. Our study highlights the importance of accommodating the inherent structure associated with site drainage area when imposing a regionally-based ecological classification upon stream ecosystems. This structure is expressed in the systematic changes to the physical habitat that occur with increasing drainage area and are reflected by the species community at the site. Management models that currently incorporate ecoregions in the classification or prediction of stream ecosystem structure would benefit from the inclusion of specific components that incorporate drainage area measurements.now at Environment Protection Authority     

Seston sedimentation in a lowland river (River Spree,Germany): their spatial and temporal variations and controlling factors

Sedimentation of organic particles plays a decisive role in streams in relation to pelagic loss as well as retention of nutrients and other substances. The plate sediment trap allows for the direct measurement of these net fluxes. Biweekly measurements were undertaken in the eutrophic lowland River Spree (MQ 14 m³ s^–1) 10 km upstream of Berlin in 1999 and 2000. Trapping rates between 0.5 and 25 g DW m^–2 day^–1 were found near the bank. The variance of seston sedimentation is controlled by the seston concentration, the settling velocity of the particles and the flow velocity. The sinking velocity exhibits significant seasonal fluctuations with highest values in summer. It is shown that the critical flow velocity for sedimentation is another important parameter. This controls the distribution of sedimentation over the width of the river and thus the effective average sedimentation rate for the entire river segment. This average rate ranged between 0.9 and 6.6 g DW m^–2 day^–1.