Drifting or walking? colonisation routes used by different instars and species of lotic, macroinvertebrate filter feeders

Many views of stream invertebrate populations centre on drift as the major route of larval dispersal, but few studies have presented unambiguous information about the role of drift. We present the results from an experiment designed to determine whether the major route of colonisation of substrata by hydropsychid larvae (commonly found in the drift) is by drifting directly onto substrata or by walking along the stream bottom. The experimental design contained four treatments: substrata open to drifters and walkers; fenced substrata open to drifters only; and two treatments open to drifters and walkers that provided forms of fence controls. Fifteen replicates of each treatment were set out at random locations within a riffle at each of three sites, with each site on a different river (the Little River, the Steavenson River and the Acheron River) in the Acheron River catchment. The experiment was run twice, once during autumn (April 1999) and once during early summer (January 2000). Both experiments were colonised by three species of hydropsychids, Asmicridea sp. AV1, and Smicrophylax sp. AV1 and AV2. We found that 2nd/3rd instars of Asmicridea sp. AV1 walked as well as drifted, whereas all others primarily drifted. No relation between numbers of recruits and water speed was found when substrata were open only to drifters, whereas substrata open also to walkers gained more recruits in faster flows. Additionally, larvae more frequently abandoned nets in slow than fast flows, indicating that drifting into unfavourable flow environments may result in mortality or redispersal of larvae. These findings demonstrate that, although drift is important, it is not necessarily the only method used by hydropsychids to colonise substrata. Larvae may have more capacity to choose substrata in fast flows when they colonise substrata by walking. Spot measures of hydropsychid distribution cannot distinguish between these explanations. The finding that walkers can sometimes comprise significant numbers of recruits raises the prospect that hydropsychids can be sourced locally and have not inevitably drifted in from upstream locations.

Effect of atypical rainfall on lotic zooplankton: comparing downstream of a reservoir and tributaries with free stretches

To contribute to the knowledge of lotic zooplankton from dammed and free stretches, we tested the hypothesis that the ecological attributes are different between these environments, which are subjected to several effects caused by different hydrological conditions. The study was carried out in the low Iguacu river, a large hydrographic basin in the south of Brasil. Two samplings were performed, one in the dry period (April/04) and the other in the atypical rainy period (July/04), in five stations downstream a large reservoir, and other 12 stations in four tributaries representing the upper, intermediate and low regions of each river. The observations suggest a clear spatial distribution of zooplankton in lotic stretches subjected or not to damming, mainly due to the effects of physical, chemical and biological variables. Furthermore, the atypical rainfall promoted alterations in community structure when compared to the dry period.

Skill development for innovative procurement environments in construction

The construction industry should be a priority to all governments because it impacts economically and socially on all citizens. Sector turnover in industrialised economies typically averages 8-12% of GDP. Further, construction is critical to economic growth. Recent Australian studies estimate that a 10% gain in efficiency in construction translates to a 2.5% increase in GDP Inefficiencies in the Australian construction industry have been identified by a number of recent studies modelling the building process. They have identified potential savings in time of between 25% and 40% by reducing non-value added steps in the process. A culture of reform is now emerging in the industry – one in which alternate forms of project delivery are being trialed. Government and industry have identified Alliance Contracting as a means to increase efficiency in the construction industry as part of a new innovative procurement environment. Alliance contracting requires parties to form relationships and work cooperatively to provide a more complete service. This is a significant cultural change for the construction industry, with its well-known adversarial record in traditional contracting. Alliance contracts offer enormous potential benefits, but the Australian construction industry needs to develop new skills to effectively participate in the new relationship environment. This paper describes a collaborative project identifying skill needs for clients and construction professionals to more effectively participate in an increasingly sophisticated international procurement environment. The aim of identifying these skill needs is to assist industry, government, and skill developers to prepare the Australian construction workforce for the future. The collaborating Australian team has been fortunate to secure the Australian National Museum in Canberra as its live case study. The Acton Peninsula Development is the first major building development in the world awarded on the basis of a joint alliance contract.

Mapping of indoor environments by robots using low-cost vision sensors

For robots to operate in human environments they must be able to make their own maps because it is unrealistic to expect a user to enter a map into the robot’s memory; existing floorplans are often incorrect; and human environments tend to change. Traditionally robots have used sonar, infra-red or laser range finders to perform the mapping task. Digital cameras have become very cheap in recent years and they have opened up new possibilities as a sensor for robot perception. Any robot that must interact with humans can reasonably be expected to have a camera for tasks such as face recognition, so it makes sense to also use the camera for navigation. Cameras have advantages over other sensors such as colour information (not available with any other sensor), better immunity to noise (compared to sonar), and not being restricted to operating in a plane (like laser range finders). However, there are disadvantages too, with the principal one being the effect of perspective. This research investigated ways to use a single colour camera as a range sensor to guide an autonomous robot and allow it to build a map of its environment, a process referred to as Simultaneous Localization and Mapping (SLAM). An experimental system was built using a robot controlled via a wireless network connection. Using the on-board camera as the only sensor, the robot successfully explored and mapped indoor office environments. The quality of the resulting maps is comparable to those that have been reported in the literature for sonar or infra-red sensors. Although the maps are not as accurate as ones created with a laser range finder, the solution using a camera is significantly cheaper and is more appropriate for toys and early domestic robots.