Project number: 2008-711
Project Status:
Completed
Budget expenditure: $290,167.63
Principal Investigator: Steven Clarke
Organisation: SARDI Food Safety and Innovation
Project start/end date: 29 Feb 2008 - 27 Feb 2011
Contact:
FRDC

Need

Controlling flukes of YTK is a major cost for producers, and the industry has identified improving the treatment of flukes as one of the top research priorities. Currently, the industry bathes fluke-infested YTK in hydrogen peroxide. Although this approach is currently efficacious, it is also costly, labour-intensive, and stressful for fish. An option to reduce the need to bathe frequently is to use in-feed therapeutic agents to kill or remove flukes. This project aims to develop palatable feeds containing medications that will significantly reduce burdens of flukes.

Changing bio-fouled nets is another costly practice for the industry. Antifoulants have the potential to not only reduce the frequency and cost of net-changing due to the need to maintain good water flow bringing dissolved oxygen to the caged fish, but also to potentially reduce the numbers of fluke eggs entangling on the nets, and therefore further reduce the numbers of infective fluke larvae settling on YTK within cages. The optimum compound to use from an assessment of three will be identified.

Commercial YTK may have experienced slower growth at Fitzgerald Bay than at Arno Bay; the cause is suspected to be due the higher salinity (39-42 ppt at Fitzgerald Bay, compared with 37 ppt at Arno Bay). It needs to be confirmed experimentally whether increased salinity slows growth, first in summer and, if not, then in winter.

Health issues affecting hatchery-reared, larval SBT are presently unknown. Before production begins, the development of health protocols and a surveillance program is required, as well as the collection of archival samples of larvae for future investigations. These investigations not only ensure the biosecurity of the hatchery but also the sea-based growout stage, whether associated with hatchery-produced or wild-caught stock. This project will also allocate a small amount of funds for early disease testing, if required.

Objectives

1. Review literature to establish best candidate in-feed medications and their dosages for the treatment of flukes, and then test the efficacy of selected in-feed medications in reducing burdens of gill and skin flukes on YTK in tank trials and in pilot-scale field trials. Determine the rate that residues of the most promising medication are cleared from fish, in accordance with APVMA requirements (Parts A-D).
2. Determine whether netting treated with antifoulants reduces the numbers of larval flukes settling on YTK and determine whether YTK absorb and retain residues of the most promising antifouling compounds (Parts F and G).
3. Establish program for 12-month routine monitoring of gill and gut pathology of YTK, and determine impact of special diet formulations on winter gut syndrome (Parts H, I).
4. Over the range of salinities experienced in Spencer Gulf, experimentally quantify the effects on performance (growth rates and apparent food conversion efficiency) and blood osmolality of YTK (Parts K, L).
5. Develop a health protocol for hatchery-reared larval SBT and preserve samples for future archival diagnostic analyses (Parts M, N).

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