Flow-related patterns in abundance and composition of the fish fauna of a degraded Australian lowland river

1. A 7‐year study was conducted in three hydrologically distinct sections within the highly regulated, lowland Campaspe River to investigate the influence of hydrology on temporal and spatial patterns in fish composition, abundance and recruitment. One section had 6 months, one section 2 months and one section no months of increased flow due to storage releases. The fish fauna of the less regulated, nearby Broken River served as a reference to which that of the Campaspe River was compared for the last 3 years of the study to allow insight into the relative effects of hydrology, barriers to movement and other environmental characteristics. The study included one high‐flow year, a moderate‐flow year and five low‐flow years. 2. A total of 16 fish species – 10 native and six alien – were caught in the Campaspe River, although of the native species, only three are considered to have self‐sustaining populations. The remaining species are either itinerants or a result of stocking. Alien species comprised approximately 64% of the total biomass of all fish caught. 3. Overall composition of the fish fauna did not differ significantly by year, but did by section of river. Species richness and the abundance of most of the dominant species also differed significantly by river section, but there was little inter‐annual variation in the abundance of any species, except for European perch and for common carp; the latter showing an increase in abundance following a high‐flow event during the spring of 2000 as a result of recruitment. 4. Overall faunal composition was not influenced by hydrology. However, multiple regression indicated that species richness, abundance of the dominant species and abundance of young‐of‐year (YOY) of golden perch, European perch and common carp all were influenced significantly by hydrological variables. The nature of the relationships was dependent on river section and hydrological season (‘winter’ or ‘spring/summer’). Of note was the result that the total abundance of fish and that of YOY common carp were significantly positively related to the number of spells above the threshold for movement upstream through the lower two weirs in the Campaspe River. Only one significant relationship between hydrological and fish‐related variables was found for the upper river section, whereas seven and five were found for the lower and middle sections respectively. 5. Comparisons with fish collected in the Broken River over 3 years suggest that the fauna of the Broken River is in a more natural state than that of the Campaspe River. Since the two rivers do not differ substantially in water quality, and since both contain significant weirs, which act as barriers to movement of fish, flow regulation is most likely to be the major reason for the poor state of the fauna in the Campaspe River.     

The effect of a foliar disease (rust) on the development of Gastrophysa viridula (Coleoptera: Chrysomelidae)

Abstract.

• 1 Gastrophysa viridula Degeer (Coleoptera: Chrysomelidae) and the pathogenic rust fungus Uromyces rumicis (Schum.) Wint. both occur on leaves of Rumex crispus L. and R.obtusifolius L. Individual stages of beetle development, and egg laying, were compared on healthy and infected leaves of each plant species in the laboratory. Oviposition choice was investigated in the field and laboratory.
• 2 Beetles reared on infected leaves of each species had greater larval mortality and slower development than those reared on healthy leaves. Although larvae feeding on infected leaves consumed up to 2.5 times more dry weight than those reared on healthy leaves, they had a lower relative growth rate and pupated at a lower weight. These changes were consistent with the reduced nutritive quality of rust-infected Rumex leaves.
• 3 Fecundity of beetles reared on infected leaves of both species was considerably reduced. Eggs laid by beetles feeding on infected R.crispus leaves also had a reduced viability.
• 4 The beetle developed consistently poorer on healthy R.crispus than on healthy R.obtusifolius throughout its life-cycle. Differences in larval performance were greater between host species than between infected and healthy leaves.
• 5 Oviposition was similar on infected and healthy R.crispus in both the laboratory and field. However, adults consumed less, and laid fewer eggs on infected than on healthy R.obtusifolius. The pattern of egg laying on different aged leaves was affected by rust infection: a greater proportion of eggs was laid on the older, infected leaves, than on the equivalent aged leaves on the healthy plants. Few larvae survived from eggs laid on rusted leaves in the field.

     

Isolation of Naegleria australiensis from an Oklahoma Lake1

Eight isolates of Naegleria australiensis were obtained from a small lake in Tulsa, Oklahoma. The eight strains were isolated during the hot summer months of July through September, when water temperatures ranged from 27 to 33°C. All eight isolates were pathogenic for mice. The mean time to death for mice was 10 days (range 6–13 days). This pathogenic free-living ameba has not before been reported from the United States or the Western Hemisphere.     

Fine Structure and Biomineralization of the Mucilage in Envelopes of Trachelomonas lefevrei (Euglenophyceae)1

Envelope development in Trachelomonas lefevrei (Deflandre) begins with the production of short, coarse mucilaginous strands, morphologically similar to the mucilage produced by non-enveloped euglenoids. These initial mucilaginous secretions subsequently become impregnated with manganese (Mn) and/or iron (Fe). Continued mucilage secretion and mineralization results in a mature envelope that is characteristic for the species. When these mature envelopes are treated with oxalic acid to remove the Mn and Fe, the envelopes collapse and are composed only of short, coarse mucilaginous strands similar to those present during early stages of development, prior to their mineralization. Brief treatment with 10 mM EDTA renders dark envelopes colorless, and our EM-EDS analyses show that this corresponds to a loss of Mn from the envelope; however, if Fe is present in the envelope, it is unaffected by the brief treatment. The mucilage present during early stages of envelope development and that remaining after complete demineralization is also morphologically similar to the mucilage in the plug at the anterior end of the envelope.     

Assessing Ecoregional-Scale Habitat Suitability Index Models for Priority Landbirds

ABSTRACT Emerging methods in habitat and wildlife population modeling promise new horizons in conservation but only if these methods provide robust population-habitat linkages. We used Breeding Bird Survey (BBS) data to verify and validate newly developed habitat suitability index (HSI) models for 40 priority landbird species in the Central Hardwoods and West Gulf Coastal Plain/Ouachitas Bird Conservation Regions. We considered a species’ HSI model verified if there was a significant rank correlation between mean predicted HSI score and mean observed BBS abundance across the 88 ecological subsections within these Bird Conservation Regions. When we included all subsections, correlations verified 37 models. Models for 3 species were unverified. Rank correlations for an additional 5 species were not significant when analyses included only subsections with BBS abundance >0. To validate models, we developed generalized linear models with mean observed BBS abundance as the response variable and mean HSI score and Bird Conservation Region as predictor variables. We considered verified models validated if the overall model was an improvement over an intercept-only null model and the coefficient on the HSI variable in the model was >0. Validation provided a more rigorous assessment of model performance than verification, and models for 12 species that we verified failed validation. Species whose models failed validation were either poorly sampled by BBS protocols or associated with woodland and shrubland habitats embedded within predominantly open landscapes. We validated models for 25 species. Habitat specialists and species reaching their highest densities in predominantly forested landscapes were more likely to have validated models. In their current form, validated models are useful for conservation planning of priority landbirds and offer both insight into limiting factors at ecoregional scales and a framework for monitoring priority landbird populations from readily available national data sets.     

Wintering site fidelity and movement patterns of Western Sandpipers Calidris mauri in the San Francisco Bay estuary

Western Sandpipers Calidris mauri are the most numerous shorebird species in the San Francisco Bay estuary during winter. A sample of 106 Western Sandpipers was captured in mist nets and radio-marked with 1-g transmitters to examine their wintering site fidelity and movements. Differences in distances moved, home range extent and core area size were examined by age, sex, season, site, time of day and tide. All birds remained in the south San Francisco Bay region during winter and exhibited strong site fidelity, with a mean home range of 22.0 km² or only 8% of the study area. First-year birds had larger home ranges (26.6 ± 3.6 km²) than adults (17.2 ± 2.5 km²) in winter, but home range sizes of males and females were not significantly different in any period. Home range sizes were similar between seasons, but core areas were smaller in spring (6.3 ± 1.2 km²) than in early (9.6 ± 4.0 km²) or late (11.6 ± 1.6 km²) winter. Movements and home range size were similar for radio-marked birds located during day and night. The high degree of regional and local site fidelity demonstrated that the mixture of natural mud fiats and artificial salt ponds in southern San Francisco Bay provided sufficient resources for large wintering populations of Western Sandpipers.