Ian Williamson

The Influence of Environment on the Morphology of Macrobrachium australiense (Decapoda: Palaemonidae)

The common endemic Australian freshwater prawn, Macrobrachium australiense is recognised as having potential as a culture species. Across the species’ natural range high variation exists for external morphological traits of relevance to culture. Previous studies have demonstrated that morphological variation can often be correlated with environmental factors. The current study demonstrated that when exposed to a controlled environment, offspring of two morphologically divergent wild stocks retain little of their parental morphological characteristics. When crossed and grown under identical conditions, ‘hybrids’ and pure offspring were morphologically uniform. A breeding and growth trial of offspring within a single stock were exposed to a variety of environmental temperatures that resulted in high variability of morphological traits in the offspring. These results suggest that environmental parameters rather than genotype may strongly influence the phenotypic expression of the morphological traits investigated. Morphological traits of interest to culture, such as abdomen length and width show low additive genetic variance and hence may not respond well to traditional selective breeding approaches designed to improve their attributes.

Microhabitat distribution of juvenile Penaeus merguiensis de Man and other epibenthic crustaceans within a mangrove forest in subtropical Australia

The distribution of juvenile Penaeus (Fenneropenaeus) merguiensis de Man and other epibenthic crustaceans in different microhabitats within a riverine mangrove forest was examined in subtropical eastern Australia. Catches in vegetated and cleared microhabitats were compared at sites located in mangroves on the creek edge (1-2 m into the forest) and the inner forest (a further 14-22 m into the forest). Crustaceans were sampled using 3 x 3 m lift nets that were activated at the top of spring flood tides between March and May 2000. The abundance of P. merguiensis in the adjacent creek was also monitored during both high and low tides using a small beam trawl. A large size range of P. merguiensis was caught in the mangrove forest (2-13.5 mm carapace length) and the maximum density recorded was 1 prawn m-2. Catches of P. merguiensis were significantly higher at the creek edge than at the inner forest sites. Catches did not differ significantly between vegetated and cleared microhabitats, but catches were highly variable within microhabitats. This result was attributed to the very high activity levels of P. merguiensis and suggests that detecting differences between microhabitats used by prawns in the field would require a large number of samples. Substantial numbers of Acetes sibogae australis (Hansen), Macrobrachium novaehollandiae (de Man) and Metapenaeus bennettae (Racek and Dall) also entered the forest and catches of these species followed a similar pattern to those for P. merguiensis, i.e. catches were higher at the creek edge than the inner forest, did not differ between microhabitats and were highly variable within a microhabitat.

Scaling Acoustic Data Analysis through Collaboration and Automation

Monitoring and assessing environmental health is becoming increasingly important as human activity and climate change place greater pressure on global biodiversity. Acoustic sensors provide the ability to collect data passively, objectively and continuously across large areas for extended periods of time. While these factors make acoustic sensors attractive as autonomous data collectors, there are significant issues associated with large-scale data manipulation and analysis. We present our current research into techniques for analysing large volumes of acoustic data effectively and efficiently. We provide an overview of a novel online acoustic environmental workbench and discuss a number of approaches to scaling analysis of acoustic data, collaboration, manual, automatic and human-in-the loop analysis.

Structural Aspects of Microhabitat Selection by the Skink Lampropholis delicata

Abstract Lampropholis delicata is a small skink common in eastern Australia. The species is heliothermic and uses the ground litter layer. This study examined whether L. delicata showed preferences for particular structural features of the ground litter layer by observing their response to a number of pairwise choices of ground litter type. Lampropholis delicata showed a clear preference for a ground litter layer with an open structure. Difference in catch rates between pairwise comparisons was positively correlated with an index of habitat accessibility. It is suggested that this habitat preference is associated with the ability of the lizard to trade-off different activities. Selection of a habitat with some form of open structure may reduce the conflict between the need for foraging and basking, and the need to find shelter from predators.

Large Scale Participatory Acoustic Sensor Data Analysis: Tools and Reputation Models to Enhance Effectiveness

Acoustic sensors play an important role in augmenting the traditional biodiversity monitoring activities carried out by ecologists and conservation biologists. With this ability however comes the burden of analysing large volumes of complex acoustic data. Given the complexity of acoustic sensor data, fully automated analysis for a wide range of species is still a significant challenge. This research investigates the use of citizen scientists to analyse large volumes of environmental acoustic data in order to identify bird species. Specifically, it investigates ways in which the efficiency of a user can be improved through the use of species identification tools and the use of reputation models to predict the accuracy of users with unidentified skill levels. Initial experimental results are reported.

Seasonal Variation and Environmental Influences on Juvenile Banana Prawn (Penaeus Merguiensis) Abundance in a Subtropical Estuary (Logan River) of Eastern Australia

Although the life history-environment relationship for juvenile Penaeus merguiensis in tropical regions has been well documented, little is known about the species towards the subtropical limits of its range. Seasonal patterns of abundances of juvenile and postlarval P. merguiensis were studied in the Logan River, a subtropical estuary in eastern Australia from January 1998 to July 2000. Prawns were sampled using a small beam trawl at fortnightly intervals when they were abundant and monthly intervals at other times. The prawns ranged in size from 1.8 to 22 mm in carapace length (CL), with a mean size ( ± 1 SE) of 6.7 ± 0.1 mm CL and were caught at densities of up to 14.2 ± 3.3 prawns m-2. Postlarvae were caught from January to July, with peaks in April and May; and juveniles were abundant from December to June, although this varied between years. The numbers of postlarvae, temperature and rainfall explained 23% of the overall variation in juvenile catches. Temperature and rainfall also explained some of the variation in postlarval catches (9.9%). Recruitment varied considerably between years, and was the highest in years when rainfall was low (1998 and 2000). In general, both the seasonal patterns of catches of postlarval and juvenile P. merguiensis, and environmental processes affecting their abundance were similar to tropical areas. However, one notable difference was that recruitment occurred over a more restricted time period in the Logan River than in tropical regions.