Using multivariate adaptive regression splines to predict the distributions of New Zealand's freshwater diadromous fish

1. Relationships between probabilities of occurrence for fifteen diadromous fish species and environmental variables characterising their habitat in fluvial waters were explored using an extensive collection of distributional data from New Zealand rivers and streams. Environmental predictors were chosen for their likely functional relevance, and included variables describing conditions in the stream segment where sampling occurred, downstream factors affecting the ability of fish to move upriver from the sea, and upstream, catchment‐scale factors mostly affecting variation in river flows. 2. Analyses were performed using multivariate adaptive regression splines (MARS), a technique that uses piece‐wise linear segments to describe non‐linear relationships between species and environmental variables. All species were analysed using an option that allows simultaneous analysis of community data to identify the combination of environmental variables best able to predict the occurrence of the component species. Model discrimination was assessed for each species using the area under the receiver operating characteristic curve (ROC) statistic, calculated using a bootstrap procedure that estimates performance when predictions are made to independent data. 3. Environmental predictors having the strongest overall relationships with probabilities of occurrence included distance from the sea, stream size, summer temperature, and catchment‐scale drivers of variation in stream flow. Many species were also sensitive to variation in either the average and/or maximum downstream slope, and riparian shade was an important predictor for some species. 4. Analysis results were imported into a Geographic Information System where they were combined with extensive environmental data, allowing spatially explicit predictions of probabilities of occurrence by species to be made for New Zealand's entire river network. This information will provide a valuable context for future conservation management in New Zealand's rivers and streams.     

Efficacy of a nature-like bypass channel in a Portuguese lowland river

Throughout Europe in the last decade there has been a steady shift away from more technical fish pass designs to more nature‐like passes, such as nature‐like bypass channels. Upstream fish passage in a nature‐like bypass channel was investigated in a lowland river, the Lima River, for 117 days from March 2000 to May 2002. Fish passage was recorded using an automatic video recording system. Electrofishing samples within the bypass and below the weir were compared with species abundance found on the tape recordings. More than 7500 individuals of eight species passed through the bypass channel. Species composition was dominated by striped mullet (65.3%) and potamodromous species (34.3%), which used the bypass mainly at night. Of the environmental variables considered, bypass discharge explained most of the variation in the number of cyprinids, whereas water temperature was more important for diadromous species. Comparing species composition below the weir using passage recordings provided a useful tool to assess species efficacy of the bypass, although biological requirements should also be taken into account. This study proved the efficacy of the bypass for passage of almost all occurring species and life stages and also for providing suitable habitat for fish fauna, highlighting the use of these facilities for river restoration schemes.     

Historical Ecology on Sandoy, Faroe Islands: Palaeoenvironmental and Archaeological Perspectives

We present palaeoenvironmental, geomorphological, archaeological, and place-name data which allow a holistic assessment of the history of landscape change on Sandoy, Faroe Islands, especially in terms of the changes that occurred in response to the colonization of the island by humans. In contrast to other situations in the North Atlantic region, there is considerable continuity in the patterns and processes of landscape evolution across the initial settlement horizon. Many of the characteristic features of post-settlement North Atlantic landscapes—absence of trees, widespread blanket mires, high rates of soil erosion—were already in place when the first people arrived. Although human impact on Sandoy appears to have been light, conversely, the unusual environment forced major alterations of the subsistence economy imported by the colonists. Settlement-era archaeological records suggest that, from the start, patterns of resource use differed substantially from the regional norm, and these differences became amplified over time as the Faroese economy created a locally sustainable cultural landscape.     

Histological Observations of Rotylenchulus reniformis on Gossypium longicalyx and Interspecific Cotton Hybrids

Observations on the development of reniform nematode (Rotylenchulus reniformis) on roots of Gossypium longicalyx, G. hirsutum, and two interspecific hybrids derived from them were made by light microscopy. Gossypium longicalyx is reported to be immune to reniform nematode, but the mechanism(s) for resistance are unknown. Penetration of G. longicalyx roots by female nematodes was confirmed, and incipient swelling of the females, indicating initiation of maturation of the reproductive system, was observed. Female maturation occurred up to the formation of a single embryo inside the female body but not beyond this point. In both hybrids, development was inhibited but progressed further than in the immune parent. Reactions ranged from highly compatible, with the formation of active syncytia and full development of females, to incompatible with little or no development of the female. Compatible plants showed characteristic hypertrophied cells, enlarged nuclei, dense cytoplasm, and partial dissolution of cell walls, whereas incompatible plant reactions included lignification of the cells adjacent to the nematode head, or the complete collapse and necrosis of the cells involved. The need to characterize reactions and to carefully select among the plants descended from the hybrids during the introgression process, as well as the importance of combining the results of reproduction tests with histological observation of the plant-nematode interactions, is discussed.     

Juvenile Sparus aurata L. on the south coast of Ireland

Records of gilthead sea bream Sparus aurata L. in Irish and British waters since 1967 are provided together with the first observations on the ecology of 0 year group gilthead sea bream in these islands.