Relationship between reproductive biology and age composition and growth in Urolophus lobatus (Batoidea: Urolophidae)

The aim of the present study was to use samples, collected by trawling throughout the year along the lower west coast of Australia, to determine the reproductive biology, size and age compositions, and growth rate of Urolophus lobatus, a member of a speciose elasmobranch family (Urolophidae) for which there was previously only a small amount of such data. U. lobatus copulates about 3 months prior to the time when females ovulate, which implies that sperm is stored in the oviducal gland of the female in the intervening period. Gestation lasts for 10 months, which is relatively long for a species that does not grow to a large size. This feature is reflected in the fact that the mean disc width at parturition (105 mm) is equivalent to as much as 44% and 52% of the asymptotic disc widths of the females and males of this species, respectively. The trends exhibited by the marginal increments on vertebral centra demonstrated that each of the translucent zones in these centra is laid down annually and that their numbers can thus be used to age this species. Maturity was attained by about 70% of females and 50% of males at the end of the 4th and 3rd years after conception, respectively, or at just over 3 and 2 years after birth, respectively. Females and males typically first reach maturity at ˜200 and ∼160 mm, respectively, and attained maximal disc widths of 277 and 237 mm, respectively. Females reached maximum ages of 15 years from conception and 14 years from birth, with the corresponding values for males being 13 and 12 years, respectively. Since such a large amount of growth occurs during gestation, von Bertalanffy growth curves were constructed using the date of conception, that is, the fertilisation date, as age 0, as is usually the case with teleosts, as well as employing the birth date as age 0, as is typically the case with elasmobranchs. The growth curves drawn through the points for the disc width-at-age of the older female and male fish gave a slightly better fit when using, as age 0, the parturition date rather than the conception date. However, the asymptotic disc widths derived for females and males using the conception date, that is, 241.3 and 202.9 mm, were each still only 7.6 mm less than those derived using the birth date. Moreover, the fit of the line drawn through the points for the disc width-at-age of fish during gestation was better using the conception date as age 0 than would be achieved by a backwards extrapolation of the growth curve using the birth date as age 0. Received: 6 January 2000 / Accepted: 17 June 2000     

Hydrologic and Water Quality Functions of a Disturbed Wetland in an Agricultural Setting1

Abstract: In 2006, we collected flow, sediment, and phosphorus (P) data at stream locations upstream and downstream of a small degraded wetland in south‐central Wisconsin traversed by a stream draining a predominantly agricultural watershed. The amount of sediment that left the wetland in the two largest storms, which accounted for 96% of the exported sediment during the observation period, was twice the amount that entered the wetland, even though only 50% of the wetland had been inundated. This apparently anomalous result is due to erosion of sediment that had accumulated in the low‐gradient channel and to the role of drainage ditches, which trapped sediment during the wetland‐filling phase. In the case of total P, the inflow to the wetland approximately equaled the outflow, although the wetland sequestered 30% of the incoming dissolved reactive P. The discrepancy is almost certainly due to net export of sediment. Many wetlands in the glaciated midwestern United States are ditched and traversed by low‐gradient channels draining predominantly agricultural areas, so the processes observed in this wetland are likely to be common in that region. Knowledge of this behavior presents opportunities to improve water quality in this and similar regions.     

Intra-laboratory evaluation of Microbial Assay for Risk Assessment (MARA) for potential application in the implementation of the Water Framework Directive (WFD)

The Microbial Assay for Risk Assessment (MARA) is an innovative system based on an array of 11 different microbial species freeze-dried in a 96-well micro-titre plate format. Developed for testing the toxicity of chemicals, mixtures and environmental samples, the assay employs species of a taxonomically diverse range. In addition to ten prokaryotic species, a eukaryote (yeast) is included in the range. The MARA's innate scope of a multi-dimensional test allows determination of toxicity based on a unique assay fingerprint or index, numerically expressed as the mean Microbial Toxic Concentration (MTC). The most significant potential of the test is in the additional inference that can be conveyed to the toxicity evaluation because of the presence of each of the constituent species. In view of the fact that conventional aquatic bioassays, like fish or cladoceran tests, are expensive and impractical, the MARA could provide a cost-effective solution for routine ecotoxicological testing. The performance of the MARA was evaluated to ascertain its capability and potential scope. Sensitivity to toxicants and different environmental samples was assessed. Evaluation included comparison with other tests: namely Microtox, invertebrate (Daphnia magna and Thamnocephalus platyurus) microbiotests, and respiration-inhibition and nitrification-inhibition tests. The most sensitive invertebrate test was found to be the T. platyurus microbiotest for three of the four metals tested. The LC(50) values for this test for Cd(ii), Cr(vi) and As(iii) were 0.2, 0.018 and 0.3 mg l(-1), respectively; and the corresponding most sensitive MARA species MTC values were 4.4, 2.8 and 17 mg l(-1), respectively.     

The European Water Framework Directive beyond 2010: let actions speak louder than words

The first generation of WFD River Basin Management Plans is now available. This is a formidable achievement and a great step towards addressing Europe's deteriorated river systems. However, plans are only words: only the actual implementation of the selected measures will result in achievement of good ecological and chemical status. The WFD Lille 2010 Conference pointed out that a lot of new, but so far unused scientific knowledge is available to improve the effectiveness of selected measures or to inspire the introduction of complementary measures. Furthermore, the complexity in terms of the functioning of the water system, its interaction with the socio-economic system and the uncertain consequences of climate change, urges a 'learning-by-doing' approach. This approach should be applied in well-designed, -coordinated and -monitored learning catchments.     

Sustainable innovation journeys: exploring the dynamics of firm practices as part of transitions to more sustainable food and farming

Deep structural and sustained change is necessary to tackle contemporary environmental challenges. How such change emerges and can be governed has been explored through the notion of sustainable innovation journeys. To date research had conceptualised such journeys as transitions to more sustainable socio-technical systems, e.g. mobility, shelter, food and farming. However, there is a paucity of how innovation proceeds in firms as part of sustainable innovation journeys. This paper begins to address this gap in knowledge. A longitudinal case study was completed of a medium-sized food-processing firm in the UK. Qualitative data were collected using ethnographic methods such as participant observation. Drawing on practice theory, a conceptual framework was developed which enabled us to explore and make sense of the firm's sustainable innovation journey conceptualised as practices. Findings show that we can usefully treat a firm as a flow of practices that either resist or otherwise accommodate new practices deemed more sustainable.