Gavin J. Partridge

The effect of salinity on growth and survival of juvenile black bream (Acanthopagrus butcheri)

Growth and survival of juvenile black bream (Acanthopagrus butcheri) were determined at salinities from 0 to 60 ppt (in 12-ppt increments) and from 0 to 12 ppt (in 4-ppt increments) in two separate trials of 6 and 4 months duration, respectively. Juvenile black bream were able to survive and grow at salinities ranging from freshwater (0 ppt) to 48 ppt. Osmotic stress was evident at 60 ppt, however, survival was not significantly affected. Fish reared at 24 ppt in trial 1 had a specific growth rate of 2.34 ± 0.03%/day, a rate significantly higher only to those fish reared at 60 ppt (2.16 ± 0.04%/day). Growth was greater at 24 ppt in association with the highest food intake and most efficient FCR. Although both food intake and FCR were not significantly higher than those obtained with fish reared at 12, 36 and 48 ppt, the combination of the two factors being optimised at 24 ppt lead to the greatest growth. Analysis of data from the second trial found no significant difference in the growth rate of black bream reared at salinities ranging from freshwater to 12 ppt, with SGR ranging from 1.92 ± 0.05%/day to 2.05 ± 0.02%/day. Variable results in freshwater between the two trials suggested that total hardness of freshwater may influence survival and/or an ontogenetic change in salinity tolerance may occur.

Development of Artificial Diets for Marine Finfish Larvae: Problems and Prospects

Publisher Summary This chapter discusses the development of artificial diets for larvae of marine finfish. The typical feeding protocol for marine finfish larvae begins with rotifers, Brachionus plicatilis followed by brine shrimp ( Artemia ), and then larger Artemia . Marine microalgae are also added to the larval rearing tank and weaning is the phase when live food organisms are replaced with artificial or formulated food particles. The high cost of live food production in finfish hatcheries could be minimized by cheaper production of live food organisms and earlier weaning onto formulated feeds. The potential advantages of using artificial diets to replace live food organisms include reduced feed costs, convenience and short- to medium- term food storage. The most significant advantage is the size of the food particle and diet composition which can be adjusted to suit the exact nutritional requirements of the larvae. The majority of artificial diets for finfish larvae have been presented as either microencapsulated diets or microbound diets.

The potential of a salt-tolerant plant (Distichlis spicata cv. NyPa Forage) to treat effluent from inland saline aquaculture and provide livestock feed on salt-affected farmland

Dryland salinity is a major problem affecting food production from agricultural land in Australia and throughout the world. Although there is much interest in using saline groundwater to grow marine fish on salt-affected farmland, the disposal of nutrient enriched, saline aquaculture effluent is a major environmental problem. We investigated the potential of the salt-tolerant NyPa Forage plant (Distichlis spicata L. Greene var. yensen-4a) to trap nutrients from saline aquaculture effluent and subsequently to provide a fodder crop for livestock. Sub-surface flow wetlands containing NyPa Forage were constructed and their efficacy in removing total nitrogen, ammonia, nitrite/nitrate, total phosphorus and orthophosphate was monitored under different levels of nutrients and salinity. The wetlands removed 60-90% of total nitrogen loads and at least 85% of ammonia, nitrite/nitrate, total phosphorus and orthophosphate loads, with greater efficiency at high nutrient and low salinity levels. The above-ground yield, sodium, crude protein (CP) and in vitro dry matter digestibility (DMD) of NyPa Forage plants were measured after fertilisation with different nutrient levels and cropping at different frequencies. Yield of plants increased with increased nutrient, while nutritive value was greater when nutrients were applied but did not differ among nutrient levels. Yield was not affected by cropping frequency, but nutritive value was greatest when plants were cropped at intervals of 21 or 42 days. At optimum nutrient addition and cropping levels, the plants had a mean CP content of 16.7% and an in vitro DMD of 67.6%, equivalent to an energy value of 9.5 MJ kg(-1). Assuming an equivalent fibre content and voluntary food intake as grass hay, and no accumulation of other toxic minerals, these nutritive values would be sufficient for maintenance or moderate liveweight gains in dry adult sheep or cattle.

Direct and indirect effects of simulated calcareous dredge material on eggs and larvae of pink snapper Pagrus auratus.

The direct and indirect effects of a simulated, calcarenite-based dredge material on eggs and larvae of pink snapper Pagrus auratus were assessed. Direct effects were assessed by measuring hatch rate or survival of eggs and pre-feeding larvae, respectively, over a range of concentrations and exposure durations. Exposure of eggs to suspended solid concentrations up to 10 000 mg l(-1) for 24 h did not affect egg buoyancy or hatch rate, despite sediment adherence occurring at the two highest concentrations tested. Newly hatched larvae, whose mouths were still closed, were relatively tolerant of suspended solids, with a 12 h lethal concentration resulting in 50% mortality, LC(50), of 2020 mg l(-1) and a first observable effect concentration of 150 mg l(-1). Once the larvaes mouths opened, tolerance was significantly reduced, with a 12 h LC(50) of 157 mg l(-1) and a first observable effect concentration of 4 mg l(-1). Tolerance of larvae to suspended solids was negatively correlated with suspended solids concentration and exposure time, with exposure durations of <or=6 h being significantly less detrimental than those of 9 h or more. Indirect effects to larvae were assessed by measuring ingestion of copepod nauplii by 10 and 15 days post-hatch (dph) larvae at sediment concentrations from 0 to 200 mg l(-1) in 50 mg l(-1) increments over 4 h. Ingestion was not significantly affected by sediment for 10 dph larvae, but by 15 dph, sediment had a far greater impact on ingestion, with larvae in all sediment treatments eating significantly fewer copepods than those in the control.

Praziquantel form, dietary application method and dietary inclusion level affect palatability and efficacy against monogenean parasites in yellowtail kingfish

The bitterness of racemic praziquantel (PZQ) currently constrains its use as an in-feed treatment against monogenean flukes in finfish aquaculture. In an effort to increase the palatability of diets containing racemic PZQ for yellowtail kingfish, the palatability and efficacy of 2 forms of racemic PZQ (powder or powder within microcapsules) against natural infestations of skin and gill flukes were compared using 2 different dietary application methods (incorporated within the pellet mash prior to extrusion or surface-coated after extrusion) at active dietary inclusion levels of 8, 16 and 25 g kg-1 in large (3.5-4 kg) yellowtail kingfish. There was no clear benefit of incorporating PZQ into diets prior to extrusion. PZQ microcapsules improved the palatability of PZQ-containing diets but did not completely mask the bitter flavour. At the lowest active dietary inclusion level of 8 g kg-1, ingestion of the diet containing PZQ microcapsules was equal to the control and significantly better than that containing PZQ powder. At an inclusion level of 16 g kg-1, ingestion of the PZQ microcapsule diet was significantly better than that containing the same inclusion of PZQ powder but significantly lower than the control. Consumption of the diet containing 25 g kg-1 of PZQ microcapsules was poor. All fish consuming medicated feeds had a significant reduction in flukes relative to control fish; however, efficacy data and blood serum analysis suggested that diets containing PZQ microcapsules had lower bioavailability than those containing PZQ powder.

Larval development of the western school prawn Metapenaeus dalli Racek, 1957 (Crustacea: Decapoda: Penaeidae) reared in the laboratory

ABSTRACT The six Naupliar, three Protozoea, three Mysis and first post-larval forms of the western school prawn Metapenaeus dalli Racek, 1957 were cultured in the laboratory. These stages were described in detail and compared to those of other metapenaeids. The ontogenetic development occurred in 12 days at 26°C, with both the growth rate and morphological patterns of development in M. dalli broadly following those recorded for other metapenaeids. Differences were found between M. dalli and other metapenaeids at corresponding stages of larval development, with these being the number, location and composition of individual setae and other minor spinal development.

Closed-cycle hatchery production of tuna

The reliance on wild-caught juvenile tuna is seen as the Achilles heel of tuna ranching industries worldwide and it is widely recognised that closed-cycle hatchery production is essential to sustain the demand for tuna and reduce pressure on wild stocks. The many features that make tuna such a unique group of fish also give rise to the many challenges associated with their culture and despite some forty years of effort, commercial scale hatchery production has yet to be fully realised. This chapter summarises the history of closed-cycle tuna production and discusses the recent and significant achievements that have been made towards the achievement of this elusive goal.

Factors affecting mark quality of alizarin complexone-stained otoliths in juvenile black bream Acanthopagrus butcheri and a prescription for dosage

The relationships between otolith score, a function of increasing stain visibility, and the ratio of alizarin complexone (mg) to fish biomass (g) for 0.1, 0.6 and 7 g black bream Acanthopagrus butcheri show that acceptable marks are produced in all size classes using a stain-to-biomass ratio of 3.3 mg g(-1) following an immersion period of 24 h.

Overview on Status and Technological Advances in Tuna Aquaculture Around the World

The current status of tuna fiseries, fattening and farming practices, as well as advances in closed-cycle tuna aquaculture, are summarized. The emergence and expansion of tuna fattening and farming activities during the last four decades have led to a shift from traditional fisheries toward aquaculture. This change is entirely reshaping the tuna fishery industry and the management of their stocks worldwide. Tuna fattening and farming operations still rely primarily on wild-caught juveniles that are fattened using small pelagic fish, blurring the line between fisheries and aquaculture and merging these activities to the point that it is no longer possible to analyze them separately. Progress in fattening operations has been limited to improved management and decreased mortalities during the capture, towing, transferring, and feeding stages of the tuna in cages. However, tuna aquaculture is now rapidly changing due to remarkable progress in closed-cycle tuna aquaculture production through advancements in broodstock maturation, spawning, larval rearing, and juvenile production technologies. Indeed, following the pioneering achievement of closing the life cycle of the Pacific bluefin tuna (PBFT) in Japan, researchers the world over are now making significant progress in hatchery technology. Closing their life cycle and the development of ecologically and economically efficient feeds that meet the specific nutritional requirements of tuna are required to ensure the future of tuna production and the conservation of tuna species. Collective efforts by researchers, academics, and the global industry are making it possible to achieve these goals.

Dietary tuna hydrolysate modulates growth performance, immune response, intestinal morphology and resistance to Streptococcus iniae in juvenile barramundi, Lates calcarifer

This study investigated the effects of tuna hydrolysate (TH) inclusion in fishmeal (FM) based diets on the growth performance, innate immune response, intestinal health and resistance to Streptococcus iniae infection in juvenile barramundi, Lates calcarifer. Five isonitrogenous and isoenergetic experimental diets were prepared with TH, replacing FM at levels of 0% (control) 5%, 10%, 15% and 20%, and fed fish to apparent satiation three times daily for 8 weeks. The results showed that fish fed diets containing 5% and 10% TH had significantly higher final body weight and specific growth rate than the control. A significant reduction in blood glucose was found in fish fed 10%, 15% and 20% TH compared to those in the control whereas none of the other measured blood and serum indices were influenced by TH inclusion. Histological observation revealed a significant enhancement in goblet cell numbers in distal intestine of fish fed 5 to 10% TH in the diet. Moreover, fish fed 10% TH exhibited the highest resistance against Streptococcus iniae infection during a bacterial challenge trial. These findings therefore demonstrate that the replacement of 5 to 10% FM with TH improves growth, immune response, intestinal health and disease resistance in juvenile barramundi.