Reducing aggression between freshwater crayfish (Cherax destructor Clark: Decapoda, Parastacidae) by increasing habitat complexity

The culture of decapod crustaceans occurs worldwide. Aggressive behaviour is common in many of the species, including crayfish. This is problematic when it physically damages stock and reduces quality. Numerous biological factors influence crayfish fighting behaviour but the influence of environmental factors is not well known. This study investigated the effect of habitat complexity on the agonistic interactions of Australian freshwater crayfish, more commonly referred to locally as ‘yabbies’ (Cherax destructor Clark). Solid objects that provided structure but not shelter were used to manipulate the complexity of the environment. The number, duration and dynamic of aggressive interactions within groups of animals were observed and recorded in simple and complex environments. Habitat complexity reduced both the number of agonistic interactions and the total time spent interacting. It is suggested that the structure in the environment distracts crayfish from the presence of others or physically blocks contact between them. These results extend our knowledge of crayfish social behaviour and may provide opportunities for reducing detrimental aggressive interactions in the aquaculture industry.     

Environmental effects of the anti-sea lice (Copepoda: Caligidae) therapeutant emamectin benzoate under commercial use conditions in the marine environment

Sea lice infestation can pose a particular problem to intensive cage aquaculture of salmonids. It is most often treated by therapeutants added to the water or incorporated into fish feed. This study investigated the environmental effects of one such in-feed treatment, emamectin benzoate, under commercial use conditions. Atlantic salmon were fed the commercial preparation of emamectin benzoate at a production fish farm on the west coast of Scotland. Sediment dwelling fauna, large mobile fauna and sentinel organisms were monitored for potential impacts over a 1 year post-treatment period (23 September 1997 to 23 September 1998). Additionally, sediment and water samples, transplanted blue mussels and captured large fauna were analysed for accumulated emamectin benzoate and its desmethylamino metabolite to investigate the long term environmental fate of emamectin benzoate.

Results from analysis of sediments suggested that limited deposition of emamectin benzoate took place during and up to 1 week post-treatment, and may have continued up to 4 months of post-treatment. This was consistent with the release of the active ingredient from fish excretion and defecation after treatment. Quantifiable amounts of emamectin benzoate were found 10 m from the cages 12 months after treatment. However, clear reduction in overall sediment concentrations indicated that the deposited emamectin was degrading over time. Emamectin benzoate was not detected in water samples during the field trial. Quantifiable concentrations of emamectin benzoate were found in blue mussels deployed up to 100 m from the treatment cages at 1 week post treatment, but found only at 10 m from the cages at 1 month post-treatment. This suggests that while mussels were actively accumulating emamectin benzoate immediately after treatment by 1 month this had largely been depurated.

Macrobenthic faunal analysis indicated that there was no evidence that the occurrence of emamectin benzoate, or its desmethylamino metabolite, in sediments around fish farm cages after treatment had any toxic impacts on organisms in either water column or sediments.     

Modeling the Diving Behavior of Whales: A Latent-Variable Approach with Feedback and Semi-Markovian Components

Recent years have seen a fast-growing body of literature concerned with the statistical modeling of animal movement in the two horizontal dimensions. On the other hand, there is very little statistical work that deals with animal movement in the vertical dimension. We present an approach that provides an important step in analyzing such data. In particular, we introduce a hidden Markov-type modeling approach for time series comprising the depths of a diving marine mammal, thus modeling movement in the water column. We first develop a baseline Markov-switching model, which is then extended to incorporate feedback and semi-Markovian components, motivated by the observations made for a particular species, Blainville’s beaked whale (Mesoplodon densirostris). The application of the proposed model to the beaked whale data reveals both strengths and weaknesses of the suggested modeling framework. The framework is general enough that we anticipate that it can be used for many other species given minor changes in the model structure.     

Formulation,synthesis and characterization of boron phosphate (BPO4) compounds as raw materials to develop slow‐release boron fertilizers

We investigated the use of boron phosphate (BPO₄) as a slow‐release boron (B) source. Boron phosphate compounds were synthesized by mixing boric acid (H₃BO₃) and phosphoric acid (H₃PO₄) and heating at temperatures of 25 to 1000°C for 1 or 24 h. X‐ray diffraction (XRD) patterns and chemical analysis confirmed the formation of BPO₄. The crystallinity of these compounds increased with increasing temperature and heating time. The compounds synthesized at 300°C or less were hygroscopic and clumped together, while those synthesized at 500 to 1000°C were non‐hygroscopic and free‐flowing. The solubility of these compounds was assessed at different pH and P concentrations, and compared to the solubility of ulexite and colemanite. The solubility of the BPO₄ compounds decreased with increasing synthesis temperature and with decreasing pH. The solubility and the kinetics of B release from BPO₄ compounds synthesized at 500 and 800°C were slower than for most commonly used B sources. Given their slow dissolution, the BPO₄ compounds may have potential to continuously supply B to crops in environments where B leaching is a problem. The compounds synthesized at 500 and 800°C show potential for co‐granulation with macronutrient fertilizers such as mono‐ammonium phosphate to produce slow‐release B‐enriched granules.     

Extraction and characterization of original lignin and hemicelluloses from wheat straw

Original lignin and hemicelluloses were sequentially extracted with high yield/purity, using acidic dioxane/water solution and dimethyl sulfoxide, from ball-milled wheat straw. The acidic dioxane lignin fraction is distinguished by high beta-O-4' structures and by low amounts of condensed units (beta-5', 5-5', and beta-1'). Hemicelluloses contain arabinoxylans as the major polysaccharides, which are substituted by alpha-l-arabinofuranose, 4-O-methylglucuronic acid, acetyl group (DS = 0.1), and xylose at O-3 and/or O-2 of xylans. It was found that arabinoxylans form cross-links with lignins through ferulates via ether bonds, glucuronic acid via ester bonds, and arbinose/xylose via both ether and glycosidic bonds, respectively, in the cell walls of wheat straw. Diferulates are also incorporated into cross-links between lignin and hemicelluloses as well as lignification of wheat straw cell walls. The guaiacyl unit is considered to be a significant condensed structural constructor in extracted lignin and a connector between lignin and carbohydrates.     

Cecocolic intussusception in a horse

A 10-month-old 160 kg bilateral cryptorchid Quarter Horse was presented for acute colic and profuse diarrhea. The horse was a bottle-raised orphan with stunted growth, a pot belly and a rough hair coat. The colt had been on a good deworming program and had a hearty appetite until the onset of colic. Economic considerations prohibited a thorough laboratory evaluation and surgical intervention.