Contribution of estuaries to commercial fisheries in temperate Western Australia and the concept of estuarine dependence

Fisheries catch statistics for temperate Western Australia are considered in conjunction with life cycle data to elucidate the importance of estuaries to the commercial and recreational fisheries in this region. The data are used to discuss whether the term estuarine-dependent is strictly applicable to all species of finfish found in abundance in estuaries. Between 1976 and 1984, 96 species of finfish, 7 species of crustaceans and 12 species of mollusks contributed to the large commercial fishery in estuaries, protected coastal areas and open marine waters of temperate Western Australia. The mean annual weight and monetary value (in 1984 terms) of this fishery was 21,355 t and $A151.3×10⁶. The contribution of the weight (4,340 t) and value ($A3.7×10⁶) of the estuarine-dependent species to the total fishery was 20.3 and 2.4%, respectively. Estuarine-dependent marine species frequently use protected inshore waters in temperate Western Australia, and have to do so when they occur in subtropical regions in Western Australia where there are no permanent estuaries. Even the semi-anadromous Perth herring and some species which are estuarinesensu stricto in south-western Australia complete their life cycle within the marine waters of this latter more northern region. Since virtually none of the commercially important marine species in temperate Western Australia can be considered to be entirely dependent on estuaries, and a similar conclusion is valid for many species of marine teleosts found in abundance in estuaries in temperate waters elsewhere in the world, these marine species would be best regarded as estuarine opportunists rather than estuarine dependents.     

Stokes imaging of the AM Her system ST LMi

The Stokes imaging technique of Potter, Hakala & Cropper is applied to the polarized emission from the AM Her system ST LMi. For the first time, the cyclotron emission region on the surface of the white dwarf is mapped in terms of optical depth/density in an analytical and objective manner. The region is found to consist of a less dense region leading a higher density region in orbital phase. It is demonstrated that the emission region needs to have a multi-temperature structure in order to explain the spectral slope and the general morphology of the cyclotron humps observed in the IR during the bright phase in ST LMi.
Furthermore, it is shown that a secondary emission region, fed by the same magnetic field lines that feed the main emission region, could be responsible for the positive circular polarization in the IR, the position angle variation and the excess flux during the faint phase of the white light observations which cannot be accounted for with a single emission region.     

Blue-green algae and fish population changes in a eutrophic estuary

Evidence is presented which indicates that dense blooms of the blue-green alga Nodularia spumigena have affected fish and crab populations in a large estuarine system in south-western Australia. For example, the numbers of fish were generally very low at sites in which the chlorophyll a level, an excellent indicator of Nodularia density during the late spring and summer, was above 100 μgl^?1. Moreover, commercial fishermen have recorded greatly reduced catches in Nodularia-affected areas and dead fish and crabs were found in regions where Nodularia was very dense. While the effects of this blue-green alga apparently led to death in the case of some bottom-living species in the most affected parts of the system, more active species moved into regions where Nodularia was virtually absent.     

Environmental Stewardship in UK agriculture: A comparison of the environmentally sensitive area programme and the Countryside Stewardship Scheme in South East England

Research into the adoption of Environmental Land Management Schemes (ELMS) has typically sought to identify the defining characteristics of participants and the ‘barriers to entry’ that dissuade others from joining. More recently, attention has focused on the motivation of participants and non-participants in helping to understand patterns of participation. This paper compares the pattern of participation in two distinct schemes operating in South East England. Indirect evidence suggests that scheme design and implementation is influencing the type of farmer joining and their motivation for doing so. Results from a survey of farmers also support the idea that the schemes are recruiting from different sections of the farming community. ESA farmers are largely motivated by financial gain, whereas those enrolling land in the Countryside Stewardship Scheme have more clearly defined conservation motives. Although there is also a ‘core’ of resistant non-participants, further changes to the design and delivery of policy could encourage a large number of ‘potential enrolers’ to join.     

Luquillo Experimental Forest: Catchment science in the montane tropics

Catchments in the Luquillo Experimental Forest (LEF) of Puerto Rico are warm, wet and tropical with steep elevational relief creating gradients in temperature and rainfall. Long-term objectives of research at the site are to understand how changing climate and disturbance regimes alter hydrological and biogeochemical processes in the montane tropics and to provide information critical for managing and conserving tropical forest ecosystems globally. Measurements of hydrology and meteorology span decades, and currently include temperature, humidity, precipitation, cloud base level, throughfall, groundwater table elevation and stream discharge. The chemistry of rain, throughfall, and streams is measured weekly and lysimeters and wells are sampled monthly to quarterly. Multiple data sets document the effects of major hurricanes including Hugo (1989), Georges (1998) and Maria (2017) on vegetation, biota and catchment biogeochemistry and provide some of the longest available records of biogeochemical fluxes in tropical forests. Here we present an overview of the findings and the data sets that have been generated from the LEF, highlighting their importance for understanding montane tropical watersheds in the context of disturbance and global environmental change.     

The Lamprey River Hydrological Observatory: Suburbanization and changing seasonality

The Lamprey River Hydrological Observatory (LRHO) is a lowland coastal watershed in southeastern New Hampshire (USA). The LRHO offers a platform to investigate the effects of suburbanization and changing seasonality on watershed hydrology, biogeochemistry, and nutrient export to an estuarine ecosystem. The LRHO utilizes a nested-watershed design to examine headwater stream and main-stem river dynamics distributed across a mixed land-use environment. Data sets from the LRHO now comprise over 20 years of weekly grab sample data as well as 7 years of high-frequency sensor data. Collectively these data sets include measures of discharge, dissolved organic matter, nutrients, cations and anions, greenhouse gases, and other physio-chemical properties. Here we share information on the setting and motivating questions of the LRHO and data availability.     

To what extent are the fish compositions at nearshore sites along a heterogeneous coast related to habitat type?

This study has tested the following main hypotheses. (1) The composition of fish assemblages in nearshore waters along the lower west coast of Australia will differ significantly among four habitat types (1–4), which could be distinguished quantitatively from each other by differences in the values for a statistically selected suite of enduring environmental variables. (2) The extents of the differences in ichthyofaunal composition among the four habitat types will statistically match those in the suite of environmental variables that distinguish those habitat types. A 60.5 m long seine net, with 9 mm mesh in the bunt, was used seasonally for 2 years to sample fish from sites representing each of the four nearshore habitat types, which differed broadly in their exposure to wave activity and the extent and location of seagrass beds. The compositions of the fish faunas in each habitat type were significantly different from each other in all but one case. Ichthyofaunal composition did not differ significantly between years in any habitat type and differed significantly among seasons in only one habitat type. The arrangement of the rank orders of similarity in matrices constructed from the abundances of the fish species at each site also did not differ between years but did differ among seasons. Moreover, the arrangement of the ranks in the similarity matrices produced from the ichthyofaunal data recorded at the various sites in each season were significantly correlated with that in the distance matrix constructed from the environmental data for those sites, with the correlation (ρ) ranging from 0.476 in winter to 0.696 in autumn. These results thus demonstrate that the extents of the differences in the fish compositions among the various habitat types parallel those in the environmental data for the corresponding habitat types. The subset of species that provided the best correlation with the environmental distance matrix, and which was thus most responsible for distinguishing among the fish compositions at the four habitat types, was also determined for each season.