Astaxanthin profiles and corresponding colour properties in Australian farmed black tiger prawn (Penaeus monodon) during frozen storage

The colour of commercial cooked black tiger prawns (Penaeus monodon) is a key quality requirement to ensure product is not rejected in wholesale markets. The colour, due to the carotenoid astaxanthin, can be impacted by frozen storage, but changes in colour or astaxanthin profile, during frozen storage, have not been studied in detail. Subsequently in this study, the aims were to define the astaxanthin (as cis, trans, mono-ester and di-ester forms) content, together with the colour properties, in both pleopods (legs) and abdominal segments. Changes in astaxanthin content and colour properties were further determined during frozen storage (−20°C). Total astaxanthin content was seen to decrease in all samples over time, with the rate of degradation being significantly greater (P < 0.05) in pleopods than abdomen. In both pleopods and abdomen, rate of degradation of esterified forms was significantly greater (P < 0.05) than non-esterified forms. Hue angle (increase), a* value (decrease) and L value (increase) were all seen to significantly change (P < 0.05) during storage, with changes being more prevalent in the pleopods. The pleopods are the key indicator of astaxanthin and colour loss in cooked black tiger prawns and preservation strategies are required to preserve astaxanthin and colour during frozen storage.

Rising temperatures increased recruitment of brown tiger prawn (Penaeus esculentus) in Moreton Bay (Australia)

Abiotic factors are fundamental drivers of the dynamics of wild marine fish populations. Identifying and quantifying their influence on species targeted by the fishing industry is difficult and very important for managing fisheries in a changing climate. Using multiple regression, we investigated the influence of both temperature and rainfall on the variability of recruitment of a tropical species, the brown tiger prawn (Penaeus esculentus), in Moreton Bay which is located near the southern limit of its distribution on the east coast of Australia. A step-wise selection between environmental variables identified that variations in recruitment from 1990 to 2014 were best explained by a combination of temperature and spawning stock biomass. Temperature explains 35% of recruitment variability and spawning stock biomass 33%. This analysis suggests that increasing temperatures have increased recruitment of brown tiger prawn in Moreton Bay.

The Cost of Co-viability in the Australian Northern Prawn Fishery

Fisheries management must address multiple, often conflicting objectives in a highly uncertain context. In particular, while the bio-economic performance of trawl fisheries is subject to high levels of biological and economic uncertainty, the impact of trawling on broader biodiversity is also a major concern for their management. The purpose of this study is to propose an analytical framework to formally assess the trade-offs associated with balancing biological, economic and non-target species conservation objectives. We use the Australian Northern Prawn Fishery (NPF), which is one of the most valuable federally managed commercial fisheries in Australia, as a case study. We develop a stochastic co-viability assessment of the fishery under multiple management objectives. Results show that, due to the variability in the interactions between the fishery and the ecosystem, current management strategies are characterized by biological and economic risks. Results highlight the trade-offs between respecting biological, economic and non-target species conservation constraints at each point in time with a high probability and maximizing the net present value of the fishery.

Impact of reducing investment disincentives on the sustainability of the Moreton Bay prawn trawl fishery

The Moreton Bay prawn trawl fishery is one of Queensland’s oldest commercial fisheries, but is currently economically unsustainable. The fishery is characterized by a mix of large and small vessels, with the small vessels facing different licensing and boat replacement restrictions to the large. Industry have proposed the removal of the current two-for-one boat replacement policy that affects the smaller vessels to encourage investment and replacement by larger vessels, although there is concern by managers about the impact of this on total fishing effort and sustainability of the stocks, despite the existence of a total cap in vessel capacity units. We estimate the impact of removing the boat replacement policy for the smaller vessels on fleet performance and total fishing effort, and find that removing the boat replacement policy is unlikely to result in a substantial increase in fishing effort due to the existence of a vessel unitization scheme.

The Predation of Artemia Nauplii by the Larvae of the Amazon River Prawn, Macrobrachium amazonicum (Heller, 1862), is Affected by Prey Density, Time of Day, and Ontogenetic Development

The present study analyzed the effects of prey density, the time of day, and ontogenetic development on the predation of Artemia nauplii by the larvae of the Amazon river prawn, Macrobrachium amazonicum, as well as possible synergy among these factors. Larvae were raised in 120-L tanks with biological filter systems, and fed on recently hatched Artemia nauplii, using two feeding management protocols: (a) fed once per day at 2000 h (high density HD) and (b) half of the ration provided at 2000 h, complemented at 0800 h the following day by a replacement of the nauplii consumed up to a maximum of the full ration (low density with replacement LDWR). Each treatment consisted of six replicates. The consumption of nauplii was estimated prior to the feeding times. Consumption varied according to time of day, ontogenetic development, and feeding protocol. The larvae ingested more nauplii during the daytime at most developmental stages. Ingestion rates were similar during the day under both treatments, but at night the higher density of prey in the HD treatment caused a higher encounter rate and increased ingestion of nauplii by the larvae. Among the performance indicators only survival was greater in HD in comparison with LDWR; productivity and dry weight were similar. The results indicate a circadian trophic rhythm in M. amazonicum, with the encounter rate being an important mechanism for the capture of prey during the night. A second mechanism probably the visual system aids the perception of prey during the daytime. Based on these results, we suggest that feeding captive Amazon river prawn larvae only once a day would be appropriate and economically beneficial. Further work is necessary to determine the most effective time that this single feed should be applied.

ECONOMIC ANALYSIS of AMAZON RIVER PRAWN FARMING TO THE MARKETS FOR LIVE BAIT and JUVENILES IN PANTANAL, BRAZIL

The implementation of a hypothetical aquaculture facility with hatchery, nursery and grow-out earthen ponds for raising the Amazon River Prawn Macrobrachium amazonicum in the Pantanal was considered. Eight larviculture cycles per year were projected: four to produce post-larvae for stocking in grow-out bait ponds, and four to stock nursery tanks to sell juveniles as seed to grow-out farms, which produce prawns for human consumption. Annual production would be 146,880 dozen bait prawns and 2,938 thousand juveniles. The assumed sale prices were US$ 1.38 per dozen baits and US$ 15.39 per thousand juveniles. The net present value was US$ 555,890.79, internal rate of return was 48% per year, payback period was 2.4 years and benefit-cost ratio was 3.90. The breakeven price to cover total costs per dozen baits was US$ 0.70 and per thousand juveniles was US$ 17.00, indicating that the selling price assumed for juveniles in base scenario is not realistic. Net return was US$ 84,773.80. The results indicate that this activity would be a lucrative and attractive investment in the Pantanal.

The history of the introduction of the giant river prawn, Macrobrachium cf. rosenbergii (Decapoda, Palaemonidae), in Brazil: new insights from molecular data

The giant river prawn, Macrobrachium cf. rosenbergii, is one of the most cultivated freshwater prawns in the world and has been introduced into more than 40 countries. In some countries, this prawn is considered an invasive species that requires close monitoring. Recent changes in the taxonomy of this species (separation of M. rosenbergii and M. dacqueti) require a re-evaluation of introduced taxa. In this work, molecular analyses were used to determine which of these two species was introduced into Brazil and to establish the geographic origin of the introduced populations that have invaded Amazonian coastal waters. The species introduced into Brazil was M. dacqueti through two introduction events involving prawns originating from Vietnam and either Bangladesh or Thailand. These origins differ from historical reports of the introductions and underline the need to confirm the origin of other exotic populations around the world. The invading populations in Amazonia require monitoring not only because the biodiversity of this region may be affected by the introduction, but also because admixture of different native haplotypes can increase the genetic variability and the likelihood of persistence of the invading species in new habitats.

Automatic grading and packing of prawns

Prawns are a substantial Australian resource but presently are processed in a very labour-intensive manner. A prototype system has been developed for automatically grading and packing prawns into single-layer 'consumer packs' in which each prawn is approximately straight and has the same orientation. The novel technology includes a machine vision system that has been specially programmed to calculate relevant parameters at high speed and a gripper mechanism that can acquire, straighten and place prawns of various sizes. The system can be implemented on board a trawler or in an onshore processing facility. © 1993.

Nitrogen and phosphorus transformations in fixed-film biofilters subjected to aeration/no-aeration cycles

Despite recent developments in fixed-film combined biological nutrients removal (BNR) technology; fixed-film systems (i.e., biofilters), are still at the early stages of development and their application has been limited to a few laboratory-scale experiments. Achieving enhanced biological phosphorus removal in fixed-film systems requires exposing the micro-organisms and the waste stream to alternating anaerobic/aerobic or anaerobic/anoxic conditions in cycles. The concept of cycle duration (CD) as a process control parameter is unique to fixed-film BNR systems, has not been previously investigated, and can be used to optimise the performance of such systems. The CD refers to the elapsed time before the biomass is re-exposed to the same environmental conditions in cycles. Fixed-film systems offer many advantages over suspended growth systems such as reduced operating costs, simplicity of operation, absence of sludge recycling problems, and compactness. The control of nutrient discharges to water bodies, improves water quality, fish production, and allow water reuse. The main objective of this study was to develop a fundamental understanding of the effect of CD on the transformations of nutrients in fixed-film biofilter systems subjected to alternating aeration I no-aeration cycles A fixed-film biofilter system consisting of three up-flow biofilters connected in series was developed and tested. The first and third biofilters were operated in a cyclic mode in which the biomass was subjected to aeration/no-aeration cycles. The influent wastewater was simulated aquaculture whose composition was based on actual water quality parameters of aquacuture wastewater from a prawn grow-out facility. The influent contained 8.5 - 9:3 mg!L a111monia-N, 8.5- 8.7 mg/L phosphate-P, and 45- 50 mg!L acetate. Two independent studies were conducted at two biofiltration rates to evaluate and confirm the effect of CD on nutrient transformations in the biofilter system for application in aquaculture: A third study was conducted to enhance denitrification in the system using an external carbon- source at a rate varying from 0-24 ml/min. The CD was varied in the range of0.25- 120 hours for the first two studies and fixed at 12 hours for the third study. This study identified the CD as an important process control parameter that can be used to optimise the performance of full-scale fixed-film systems for BNR which represents a novel contribution in this field of research. The CD resulted in environmental conditions that inhibited or enhanced nutrient transformations. The effect of CD on BNR in fixed-film systems in terms of phosphorus biomass saturation and depletion has been established. Short CDs did not permit the establishment of anaerobic activity in the un-aerated biofilter and, thus, inhibited phosphorus release. Long CDs resulted in extended anaerobic activity and, thus, resulted in active phosphorus release. Long CDs, however, resulted in depleting the biomass phosphorus reservoir in the releasing biofilter and saturating the biomass phosphorus reservoir in the up-taking biofilter in the cycle. This phosphorus biomass saturation/depletion phenomenon imposes a practical limit on how short or long the CD can be. The length of the CD should be somewhere just before saturation or depletion occur and for the system tested, the optimal CD was 12 hours for the biofiltration rates tested. The system achieved limited net phosphorus removal due to the limited sludge wasting and lack of external carbon supply during phosphorus uptake. The phosphorus saturation and depletion reflected the need to extract phosphorus from the phosphorus-rich micro-organisms, for example, through back-washing. The major challenges of achieving phosphorus removal in the system included: (I) overcoming the deterioration in the performance of the system during the transition period following the start of each new cycle; and (2) wasting excess phosphorus-saturated biomass following the aeration cycle. Denitrification occurred in poorly aerated sections of the third biofilter and generally declined as the CD increased and as the time progressed in the individual cycle. Denitrification and phosphorus uptake were supplied by an internal organic carbon source, and the addition of an external carbon source (acetate) to the third biofilter resulted in improved denitrification efficiency in the system from 18.4 without supplemental carbon to 88.7% when the carbon dose reached 24 mL/min The removal of TOC and nitrification improved as the CD increased, as a result of the reduction in the frequency of transition periods between the cycles. A conceptual design of an effective fixed-film BNR biofilter system for the treatment of the influent simulated aquaculture wastewater was proposed based on the findings of the study.

The cultures of Restaurant Australia: epicurean food experiences for tourists in south east Queensland

Tourism Australia’s launch of the ‘Restaurant Australia’ marketing campaign in 2014 is aimed at changing perceptions of the ‘prawn on the barbeque’ image of Australian culinary culture. The campaign is the government's response to global research that reveals that tourists want ‘good’ food and wine experiences (in Australia?). In effect, ‘Restaurant Australia’, and the AUS$10 million supporting it, is promoting? the notion that Australian tourism should provide epicurean food experiences associated with high quality and ‘authentic cultural’ tourism, rather than contrived versions of national identity articulated via stereotypical notions of national cuisine. This paper adopts a cultural tourism approach, especially in relation to theories of authenticity and the relationship of post-tourists, cultural tourists, and tactical tourists to examine two very different areas of wine and food production in Australia in the context of the Restaurant Australia campaign. In particular, it considers issues associated with defining Australian cuisine and the development of a narrative about Australia as a epicurean destination.

Deriving optimal fishing effort for managing Australia's Moreton Bay multispecies trawl fishery with aggregated effort data

Deriving an estimate of optimal fishing effort or even an approximate estimate is very valuable for managing fisheries with multiple target species. The most challenging task associated with this is allocating effort to individual species when only the total effort is recorded. Spatial information on the distribution of each species within a fishery can be used to justify the allocations, but often such information is not available. To determine the long-term overall effort required to achieve maximum sustainable yield (MSY) and maximum economic yield (MEY), we consider three methods for allocating effort: (i) optimal allocation, which optimally allocates effort among target species; (ii) fixed proportions, which chooses proportions based on past catch data; and (iii) economic allocation, which splits effort based on the expected catch value of each species. Determining the overall fishing effort required to achieve these management objectives is a maximizing problem subject to constraints due to economic and social considerations. We illustrated the approaches using a case study of the Moreton Bay Prawn Trawl Fishery in Queensland (Australia). The results were consistent across the three methods. Importantly, our analysis demonstrated the optimal total effort was very sensitive to daily fishing costs-the effort ranged from 9500-11 500 to 6000-7000, 4000 and 2500 boat-days, using daily cost estimates of $0, $500, $750, and $950, respectively. The zero daily cost corresponds to the MSY, while a daily cost of $750 most closely represents the actual present fishing cost. Given the recent debate on which costs should be factored into the analyses for deriving MEY, our findings highlight the importance of including an appropriate cost function for practical management advice. The approaches developed here could be applied to other multispecies fisheries where only aggregated fishing effort data are recorded, as the literature on this type of modelling is sparse.