Seabed discrimination data from SeaScan™

Raw data from SeaScan™ transects off Wide Bay (south Queensland) taken in August 2007 as part of a study of ecological factors influencing the distribution of spanner crabs (Ranina ranina). The dataset (comma-delimited ascii file) comprises the following fields: 1. record number 2. date-time (GMT) 3. date-time (AEST) 4. latitude (signed decimal degrees) 5. longitude (decimal degrees) 6. speed over ground (knots) 7. depth (m) 8. seabed roughness (v) 9. hardness (v) Indices of roughness and hardness (from the first and second echoes respectively) were obtained using a SeaScan™ 100 system (un-referenced) on board the Research Vessel Tom Marshall, with the ship’s Furuno FCV 1100 echo sounder and 1 kW, 50 kHz transducer. Generally vessel speed was kept below about 14 kt (typically ~12 kt), and the echo-sounder range set to 80 m. The data were filtered to remove errors due to data drop-out, straying beyond system depth limits (min. 10 m), or transducer interference.

Commercial application of polychaete sand filters for wastewater remediation and broodstock feeds

Summary Prototype sand-worm filtration beds were constructed at two prawn farms and one fish farm to assess and demonstrate their polychaete (marine worm) production and wastewater remediation capacities at semi-commercial scale. Wastewater treatment properties were monitored and worms produced were assessed and either sold for bait or used by the farms’ hatcheries as broodstock (prawn or fish breeder) feed. More than 34 megalitres of prawn- and fish-pond water was beneficially treated in the 116-319-d trial. The design of the polychaete-assisted sand filters (PASFs) constructed at each farm affected their water handling rates, which on average ranged from 315 to 1000 L m-2 d-1 at the three farms. A low profile design incorporating shallow bunded ponds made from polyethylene liner and timber stakes provided the easiest method of construction. This simple design applied at broad scale facilitated the highest quantities of treated water and the greatest worm production. Designs with higher sides increased the head pressure above the sand bed surface, thus increasing the amount of water that could be treated each day. Most water qualities were affected in a similar way to that demonstrated in the previous tank trials: dissolved oxygen, pH, total suspended solids and chlorophyll a levels were all consistently significantly lowered as pond water percolated through the sand bed, and dissolved forms of nitrogen and phosphorus were marginally increased on several occasions. However, unlike the previous smaller-scale tank trials, total nitrogen (TN) and total phosphorus (TP) levels were both significantly lowered by these larger-scale PASFs. The reasons for this are still unclear and require further research. Maximum TN and TP removals detected in the trial were 48.8% and 67.5%, respectively, and average removals (in unfed beds) at the three farms ranged from 20.0 to 27.7% for TN and from 22.8 to 40.8% for TP. Collectively, these results demonstrate the best suspended solids, chlorophyll and macronutrient removal capacities so far reported for any mariculture wastewater treatment methodology to date. Supplemental feeding of PASFs with fish meal was also investigated at one farm as a potential means of increasing their polychaete biomass production. Whilst fed beds produced higher biomass (152 ± 35 g m-2) compared with unfed beds (89 ± 17 g m-2) after 3.7 months of operation, the low number of replicates (2) prevented statistically significant differences from being demonstrated for either growth or survival. At harvest several months later, worm biomass production was estimated to be similar to, or in slight excess of, previously reported production levels (300-400 g m-2). Several qualities of filtered water appear to have been affected by supplemental feeding: it appeared to marginally lower dissolved oxygen and pH levels, and increased the TN and TP levels though not so much to eliminate significant beneficial water treatment effects. Periodic sampling during an artificial-tide demonstrated the tendency for treated-water quality changes during the first hour of filtration. Total nitrogen and ammonia peaked early in the tidal flow and then fell to more stable levels for the remainder of the filtration period. Other dissolved nutrients also showed signs of this sand-bed-flushing pattern, and dissolved oxygen tended to climb during the first hour and become more stable thereafter. These patterns suggest that the routine sampling of treated water undertaken at mid-inflow during the majority of the wider study would likely have overestimated the levels of TN and dissolved nutrients discharged from the beds, and hence underestimated the PASFs treatment efficacies in this regard. Analyses of polychaete biomass collected from each bed in the study revealed that the worms were free from contamination with the main prawn viruses that would create concerns for their feeding to commercial prawn broodstock in Australia. Their documented proximal and nutritional contents also provide a guide for hatchery operators when using live or frozen stock. Their dry matter content ranged from 18.3 to 22.3%, ash ranged from 10.2 to 14.0%, gross energy from 20.2 to 21.5 MJ kg-1, and fat from 5.0 to 9.2%. Their cholesterol levels ranged from 0.86 to 1.03% of dry matter, whilst total phospholipids range from 0.41 to 0.72%. Thirty-one different fatty acids were present at detectable (≥0.005% of dry matter) levels in the sampled worm biomass. Palmitic acid was by far the most prevalent fatty acid detected (1.21 ± 0.18%), followed by eicosapentaenoic (EPA) (0.48 ± 0.03%), stearic (0.46 ± 0.04%), vaccenic (0.38 ± 0.05%), adrenic (0.35 ± 0.02%), docosadienoic (0.28 ± 0.02%), arachidonic (AA) (0.22 ± 0.01%), palmitoleic (0.20 ± 0.04%) and 23 other fatty acids with average contents of less than 0.2% of dry matter. Supplemental feeding with fish meal at one farm appeared to increase the docosahexaenoic acid (DHA) content of the worms considerably, and modify the average AA : EPA : DHA from 1.0 : 2.7 : 0.3 to 1.0 : 2.0 : 1.1. Consistent with previous results, the three most heavily represented amino acids in the dry matter of sampled worms were glutamic acid (8.5 ± 0.2%), aspartic acid (5.5 ± 0.1%) and glycine (4.9 ± 0.5%). These biomass content results suggest that worms produced in PASF systems are well suited to feeding to prawn and fish broodstock, and provide further strong evidence of the potential to modify their contents for specific nutritional uses. The falling wild-fishery production of marine bloodworms in Queensland is typical of diminishing polychaete resources world-wide and demonstrates the need to develop sustainable production methods here and overseas. PASF systems offer the dual benefits of wastewater treatment for environmental management and increased productivity through a valuable secondary crop grown exclusively on waste nutrients.

Marking scallops for release and recapture

Objectives : To develop a method to mark hatchery reared saucer scallops to distinguish them from animals derived from wild populations. Outcomes achieved : Juvenile saucer scallop (Amusium balloti) shells have been successfully marked en masse using 3 chemicals, namely alizarin red S, calcein and oxytetracycline (OTC). Considering spat survival, mark quality and mark duration collectively, the most successful chemical was OTC. Scallop spat immersed for three days in 200 or 300 mg L-1 OTC resulted in good mark incorporation and high survival. Tris was an effective means of buffering pH change during OTC treatment, with no apparent adverse effects to the scallops. The marks from OTC treatment were still visible in live scallops for at least 10 months, even with exposure to natural filtered light during that period. A second discernible shell mark was added 27 days after the first with no evident toxicity to the scallops. A simulated seabed system was designed which provide marked improvements in scallop juvenile survival and growth. Advice on shell marking has been given to QSS by DPI&F, and the first commercial trials have now commenced, with initial results showing successful marking of juvenile scallops at QSS. This research will allow the industry to monitor the survival, growth and movement of specific cohorts of deployed scallops. This will provide valuable feedback to assess the value of the ranching venture, to optimise release strategies, and to develop improved species management plans.

Screening bacterial metabolites for inhibitory effects against Batrachochytrium dendrobatidis using a spectrophotometric assay

Certain bacteria present on frog skin can prevent infection by the pathogenic fungus Batrachochytrium dendrobatidis (Bd), conferring disease resistance. Previous studies have used agar-based in vitro challenge assays to screen bacteria for Bd-inhibitory activity and to identify candidates for bacterial supplementation trials. However, agar-based assays can be difficult to set up and to replicate reliably. To overcome these difficulties, we developed a semi-quantitative spectrophotometric challenge assay technique. Cell-free supernatants were prepared from filtered bacterial cultures and added to 96-well plates in replicated wells containing Bd zoospores suspended in tryptone-gelatin hydrolysate-lactose (TGhL) broth medium. Plates were then read daily on a spectrophotometer until positive controls reached maximum growth in order to determine growth curves for Bd. We tested the technique by screening skin bacteria from the Australian green-eyed tree frog Litoria serrata. Of bacteria tested, 31% showed some degree of Bd inhibition, while some may have promoted Bd growth, a previously unknown effect. Our cell-free supernatant challenge assay technique is an effective in vitro method for screening bacterial isolates for strong Bd-inhibitory activity. It contributes to the expanding field of bioaugmentation research, which could play a significant role in mitigating the effects of chytridiomycosis on amphibians around the world.