Louis Evans

Synopsis of freshwater crayfish diseases and commensal organisms

Disease agents and pests associated with freshwater crayfish fall into six main categories—viruses, bacteria, rickettsia-like organisms (RLOs), fungi, protists and metazoans. Data and information on specific disease agents and pests from each of these categories are presented in this synopsis. Each agent or group of agents is considered under the following headings—condition, causative agent(s), life cycle/life history, epizootiology, pathology, pathogen viability. Information for the synopsis was obtained from the published literature and from personal contact with internationally recognised experts in freshwater crayfish aquaculture, biology and disease. Data of relevance for import risk analysis are summarised. Import risk analysis is the process by which the risks associated with importation of animals and plants, and products derived from animals and plants, are assessed and managed. Hazard identification is essential and is the first component of an import risk analysis. In 1996, the Australian Quarantine and Inspection Service (AQIS) commenced a review of policy relating to the importation of non-viable freshwater crayfish products, along with a suite of other aquatic animal products. AQIS commissioned a synopsis of freshwater crayfish pests and pathogens for use as a resource document for hazard identification in the formal IRA process.

Investigation of alternative protein sources in practical diets for juvenile shrimp, Penaeus monodon

Abstract A 42-day feeding trial was conducted using juvenile Penaeus monodon (4.86 ± 0.52 s.d. g mean initial weight) to evaluate the efficacy of five isoproteic (40%), isolipidic (4–5%) practical diets containing various (fish and crustacean) protein sources in different combinations. The diets contained laboratory preparations of scallop waste and shrimp head meals (D1), sardine and shrimp head meals (D2), sardine and lobster waste meals (D3), sardine and shrimp head meals with lupinseed meal replacing soybean meal and wheat flour (D4) and commercial preparations of fish and shrimp meals (D5). Diet D1 produced significantly greater weight gain than all other diets ( P P P P P P P. monodon were not significantly different among the test diets with a range of 96 to 100% (% survival) and 72.1–74.1%, 8.0–8.8%, and 13.8–15.8% for crude protein, lipid and ash content, respectively ( P > 0.05). The best pellet stability was displayed by diets D1 and D3 and the poorest stability by diet D4 ( P P. monodon . The diet combining scallop waste and shrimp head meals as major protein sources (D1) was found to be relatively superior to other diets for juvenile P. monodon , followed by the diets containing sardine and shrimp head meals (diet D2) and sardine and lobster waste meals (diet D3). The commercial fish and shrimp meal based diet (D5) and the sardine and shrimp head meal based diet containing lupinseed meal (D4) gave the poorest performance.

Hemolymph clotting time as an indicator of stress in western rock lobster (Panulirus cygnus George)

Abstract A simple method to measure clotting time was introduced in an experiment studying the effects of exercise stress on western rock lobster ( Panulirus cygnus ). The treatment group lobsters ( N =8) were made to exercise (tail flipping) in a 200 l tank for 2 min. Lobsters were then sampled immediately after exercise and once again 1 h later. Controls were sampled both before the experiment started and after all the other samples were taken (pre- and post-exercise controls). Total hemocyte counts (THCs), differential hemocyte counts (DHCs), hemolymph clotting time, hemolymph protein content and lobster vigor were analyzed. THCs, DHCs, hemolymph clotting and vigor index showed response to treatment. THCs were increased significantly 1 h after exercise (6.36±0.58×10 6 cells/ml) compared to pre- and post-exercise controls (4.42±0.38 and 4.41±0.38×10 6 cells/ml, respectively). Hemolymph clotting time in the same experimental lobsters (43.7±2.0 s) were decreased compared to pre- and post-exercise control groups (56.0±4.1 and 52.7±2.2 s, respectively). Hemolymph clotting times were correlating with DHCs and hemolymph protein levels. Hemolymph clotting time is easily measured and could be a useful indicator of stress.

Effect of air exposure on the immune system of the rock lobster Panulirus cygnus

This study aimed to determine the effect of post harvest operations such as air exposure on the health status of lobsters. These effects can be assessed through measurement of selected immune parameters such as total haemocyte counts, haemolymph clotting time, bacteraemia and the differential proportion of granular cells in lobster haemolymph. Lobsters were taken from factory holding tanks and exposed to air for 2, 6, 12, and 18 h through placement in foam boxes. Controls were sampled at each time point by collecting lobsters from the same tank as the experimental animals (10 animals /treatment group) with a different group of lobsters being sampled at each time point. Air exposure caused a significant increase in clotting time at 12h and 18h. Total haemocyte counts showed a decreasing trend. The proportion of granular cells tended to be lower in air-exposed animals, the difference was significant at 2h exposure. The bacteraemia levels tended to be higher in air exposed lobsters than in controls and the difference was significant at 12h exposure. Low total haemocyte counts, high clotting times, low granular cell numbers and high bacteraemia levels implied increased susceptibility to infection and lowered immunity. The results show that air exposure has a significant adverse effect on the immune system and hence on the health status of the lobsters.

Digestibility studies on fisheries by-product based diets for Penaeus monodon

Abstract Apparent dry matter digestibility (ADMD) and apparent protein digestibility (APD) of four isonitrogenous practical diets (40% crude protein) containing different combinations of marine animal protein sources prepared from fisheries by-products were determined for juvenile Penaeus monodon (average weight 4.65 ± 0.99 g). An indirect method using chromic oxide (Cr 2 O 3 ) as an indicator was employed for the determination of digestibility. The diet formulations tested contained mollusc and crustacean waste meals (scallop and shrimp head, diet D1) and fish and crustacean waste meals (sardine and lobster, diet D2; sardine and shrimp head, diet D3). Diet D4 contained commercially available fish and crustacean meals (anchovy and shrimp). In addition, all diets contained soya-bean meal, wheat flour and rice pollard as plant protein sources except for diet D3 in which the diverse plant protein sources were replaced by lupinseed meal. The ADMD and APD values of the three diets D1, D2 and D4 were similar with a range of 75.8–78.1% and 92.0–92.8%, respectively. The diet combining sardine and shrimp head meals with lupinseed meal (D3) had significantly lower ADMD and APD values of 53.2% and 85.4%, respectively, than the other three diets. When the essential amino acid index (EAAI) was used to evaluate the protein quality of these diets with whole juvenile P. monodon as the reference protein, all diets gave a similar result with a range of 0.94–0.96. The results indicate that fish meals prepared from fisheries by-products were digested as efficiently as those prepared from commercial fish meals and have potential as alternative animal protein sources in shrimp diets. However, replacement of the plant protein sources with lupinseed meal lead to a decrease in the digestibility with P. monodon .

Lupin ingredients in shrimp (Penaeus monodon) diets: influence of lupin species and types of meals

The nutritive value of five isonitrogenous practical diets containing different legume meals, whole or dehulled lupin (Lupinus albus) seed meal (WAD and DAD, respectively), dehulled lupin (L. angustifolius) seed meal (DND), lupin (L. angustifolius) protein concentrate (LPCD), and defatted soybean meal (SBD), was evaluated in two laboratory experiments (growout and digestibility studies) using juvenile (4.07±0.05 g, mean±SD) shrimp, Penaeus monodon. In the 42-day growout study, shrimp fed SBD or DND had significantly higher (P<0.05) growth rates than those fed LPCD, DAD or WAD. Protein conversion efficiency (PCE) and apparent protein utilization (APU) values of DND were significantly higher than those of LPCD, DAD or WAD. SBD and DND had significantly higher feed intake values and better feed conversion ratios (FCRs) than WAD and DAD. LPCD had a similar FCR to other diets but lower feed intake than SBD. Shrimp fed WAD had significantly poorer performance in all the above parameters than shrimp fed other diets except for DAD and LPCD. The diets SBD, DND, LPCD, and DAD had significantly higher (P<0.05) apparent dry matter digestibilities (ADMD) (68.3–71.4%) than WAD (64.4%). All diets had a similar apparent protein digestibility (APD) (87.1–89.1%) with a small, but significant difference being observed for the diets with the highest (DND) and the lowest (WAD) protein digestibility. Pellet water stability was significantly different (P<0.05) among the diets. The most stable pellet was displayed by LPCD, while WAD had the poorest water stability. Dehulling or concentrating lupin seed protein did not improve the nutritive value of lupin diets for juvenile P. monodon. The lupin seed meal of L. angustifolius was better utilized by P. monodon than that of L. albus and the nutritive value of L. angustifolius diet was equal to that of soybean (control) diet. Results of a feeding preference test also indicated that L. angustifolius diet was more attractive for juvenile P. monodon than L. albus diet.

Improved approaches to ecotoxicity testing of petroleum products.

Crude oils produced in the North West shelf of Western Australia are highly volatile, a characteristic not shared by most of the Northern Hemisphere crude oils on which internationally accepted toxicity test protocols were developed. Because of this volatility and some other factors, the LC50 and EC50 values obtained from acute toxicity tests will be significantly affected by the changes of toxicant concentration in test solutions during the period of exposure. To address these issues all steps of a standard protocol for crude oil toxicity testing have been revised. A systematic study has been performed on factors which affect petroleum hydrocarbon solubilisation in aqueous systems during test solution preparations. The influence of mixing time, agitation energy and volume/ interface ratio on a hydrocarbon concentration in a water-soluble fraction (WSF) was studied for heavy, medium and light crude oils. A study of the sensitivity of marine unicellular algae to WSF of crude oils was conducted with Isochrysis sp., Nannochloropsis-like sp. and Nitzchia closterium. Total concentrations of hydrocarbons dissolved in test solutions were estimated by UV-spectrometry and GC/FID chemical analyses. When the toxicant concentration decreased during the exposure period, the EC50 values derived from initial or final concentrations either underestimate or overestimate toxicity, respectively. Therefore, weighted average concentrations (WAC) calculated for the whole test period were recommended for expressing hydrocarbon concentrations in test solutions of crude oils. Toxicity indices calculated from WAC of total hydrocarbons for different crude oils can be compared regardless of the rates of hydrocarbon loss.

Toxicity of acid mine pit lake water remediated with limestone and phosphorus.

Pit lakes are increasingly common worldwide and have potential to provide many benefits. However, lake water toxicity may require remediation before beneficial end uses can be realised. Three treatments to remediate AMD (pH approximately 4.8) pit lake water containing elevated concentrations of Al and Zn from Collie, Western Australia were tested in mesocosms. Treatments were: (a) limestone neutralisation (L), (b) phosphorus amendment (P), and (c) combined limestone neutralisation and phosphorus amendment (L+P). Laboratory bioassays with Ceriodaphnia cf. dubia, Chlorella protothecoides and Tetrahymena thermophila assessed remediation. Limestone neutralisation increased pH and reduced heavy metal concentrations by 98% (Al) to 14% (Mg), removing toxicity to the three test species within 2 months. Phosphorus amendment removed toxicity after 6 months of treatment. However, phosphorus amendment to prior limestone neutralisation failed to reduce toxicity more than limestone neutralisation alone. Low concentrations of both phosphorus and nitrogen appear to limit phytoplankton population growth in all treatments.

Antibacterial activity in the haemolymph of western rock lobster,Panulirus cygnus

Nonspecific antibacterial activity (ABA) of lobster haemolymph was investigated as an indicator of lobster immune-system status and health condition. To determine whether ABA was localised in the plasma or in the haemocytes, we destroyed the haemocyte membrane by sonication and analysed samples containing plasma and haemocyte lysates for ABA along with sera from the same lobsters. Haemocytes were the main site of ABA in lobster haemolymph. In an experiment designed to assess typical handling conditions, lobsters were placed for 6 h under treatment conditions simulating five transport/storage approaches: submerged in flow-through water, sprayed with flow-through water, submerged in recirculating water, sprayed with recirculating water, and exposed to humid air. The lowest ABA was observed in the two submerged treatments and the highest in the two spray treatments. Lobsters that subsequently survived a simulated live-shipment procedure exhibited significantly lower ABA than did those found dead or weak during a subsequent 7 days of holding in the tank. We concluded that handling stress is associated with high ABA level in lobster haemolymph.

Urban runoff impacts on receiving aquatic ecosystems assessed using periphyton community

Urban runoff is a major cause of stream degradation. For appropriate management action, there is a need to establish whether or not the runoff is degrading or potentially will degrade the receiving water. This work explored the use of local periphyton communities for assessing the ecological impacts of runoff of two urban catchments. Periphyton communities were colonized on glass substrate for 2 weeks in riverine waters receiving the urban runoff and in non-receiving waters at an upstream reference site. The receiving communities were evaluated against the reference community for photosynthetic efficiency and tolerance to copper, identified to be a significant runoff stressor. Photosynthesis efficiency was measured as a PSII quantum yield, and community tolerance was assessed using a laboratory ecotoxicological test. The hypothesis tested is that the runoff degrades by causing communities in receiving waters to become more sensitive to runoff stressors. The bioassessment indicated a much higher copper threshold than provided for in the generic water quality guidelines. The significance in the use of local community is that it allows for ecological risk analysis of exposure to runoff stressors, providing site-specific information relevant to management.