Project number: 2014-242
Project Status:
Completed
Budget expenditure: $308,990.00
Principal Investigator: Peter Lee
Organisation: Department of Agriculture and Fisheries EcoScience Precinct
Project start/end date: 30 Sep 2014 - 29 Jun 2016
Contact:
FRDC
SPECIES

Need

There is a need to build on the work conducted under the auspices of the Seafood CRC and address the issues that have arisen in commercialising cobia. A number of unforeseen circumstances, in both seed supply and grow-out of cobia, arose during the Seafood CRC project,that limited the commercial development of this species.

Cobia is typically regarded as a gonochoristic species. However, a relatively high incidence of intersex individuals in captive-reared broodstock populations has occurred in recent years. This appears to have reduced reproductive output and therefore the regularity and quantity of seed supply. The mechanism behind the intersex individuals, early identification of the anomaly and the potential impact on reproductive output
and commercial hatchery production warrant further investigation. There is a need to capture and maintain wild cobia to provide contingency for the occurrence of reproductive abnormalities in captive-reared fish and to facilitate comparative developmental trials. There may also be a need to provide wild fish for the
development of a broodstock facility at PRF’s hatchery.

PRF has faced a number of challenges in commercialising cobia production. Predation and fish health have had major impacts on productivity over earlier production seasons. Whilst a number of innovative techniques have been implemented to reduce these impacts, there remains a need to improve and refine these further

There are currently no commercial hatcheries producing cobia; as such there remains a need for support from DAFF to supply juvenile fish for on-growing. Small-scale hatchery production at PRF was successful in producing juvenile cobia; however, there is a need to increase this to a commercial scale over the course of this project. DAFF will also supply larvae to continue the development of hatchery capability at PRF and to support PRF’s anticipated development of broodstock holding and maturation facilities.

Objectives

1. Transitioning to independent commercial productiona. Provide juvenile cobia for commercial grow out to further develop commercialisation of the speciesb. Further develop commercial larval rearing capacity through seed supply, technology transfer and staff exchange c. Technology transfer and staff exchange to develop capacity to maintain and spawn broodstock cobia
2. Expand cobia production to the wider industry
3. Improve production efficienciesa. Refine stocking rates and production densitiesb. Improved health management through routine sampling and early diagnosis, disease investigation and health trainingc. Implement methods to reduce predation
4. Analysis and identification of reproductive disorders in broodstock

Final report

ISBN: 978-0-7345-0458-6
Authors: Peter Lee Luke Dutney John Moloney Maria Mitris Trevor Borchert David Nixon Hazra Thaggard Brad Calcott Alyce Taylor-Brown Adam Polkinghorne
Final Report • 2018-09-12 • 2.61 MB
2014-242-DLD.pdf

Summary

This project is a collaboration between the Department of Agriculture and Fisheries (DAF) and the Cobia aquaculture sector, predominantly Pacific Reef Fisheries (PRF). It was undertaken to consolidate the aquaculture in Australia of Cobia, a species offering considerable potential as a diversification option for pond-based culture activities in Queensland. The project addressed key elements of the production cycle in order to move industry towards a more commercial footing and advance both the scientific knowledge and human capabilities of the sector. The project involved DAF staff at the Department’s Bribie Island Research Centre (BIRC) and staff from the PRF farm in Ayr, North Queensland. From 2014-2017, research examined: health issues affecting Cobia in culture both in the hatchery and on-farm; the emerging issue of intersex in Cobia and potential for this to further impact production; capability development of PRF staff in preparation of the establishment of a commercial Cobia hatchery; and, the involvement of some new entrants to Cobia aquaculture utilising tank-based production systems.

The supply of a total of 59,700 fingerlings (26,300 in 2014/15; 18,100 in 2105/16 and 15,300 in 2016/17) enabled industry collaborators to maintain production at 100 T per annum, sufficient to continue to supply the market which has been developed over several years.   Losses incurred during one contracted fish transportation event, highlighted the risks associated with this activity. This was successfully addressed in two later transportation activities by adapting PRF’s own prawn transport system.

Health management continues to be a key activity on-farm, with parasites identified as a significant and ongoing difficulty. In the hatchery, catastrophic losses of larvae were diagnosed due to epitheliocystis, caused by chlamydia-like intracellular bacteria. Molecular testing however confirmed that the bacteria was not in the order Chlamydiales, unlike several other species causing epitheliocystis in fish. Management of the infection by oxytetracycline was demonstrated and this remains an effective means of control.

Intersex frequency was negligible in the cohort examined and these individuals demonstrated significantly different growth and reproductive development to intersex animals. Females grew larger than males and animals underwent normal maturation and were successfully spawned. Intersex was found to occur at negligible levels in this cohort (<1%), and sexually dimorphic growth was shown. Incidence of 0.5% was confirmed by destructive and non-destructive gonadal examinations. Growth rates were also followed and compared to cohorts known to have significant levels of intersex individuals. Animals were followed to maturity and gonadal development assessed using examination of gonadal biopsy samples. Individuals were also raised to maturity and induced to spawn with fecundity and fertilisation rates assessed.

The study has continued to demonstrate the viability of Cobia as a diversification options for prawn farms, particularly in North Queensland. While the commercial success of tank-based Cobia aquaculture is yet to be demonstrated, continued interest in this species is encouraging, particularly in relation to a potential role for Cobia as a diversification option for prawn farms in the Logan region, following the outbreak of white spot disease in 2016. The development of this sector of the industry may well occur in conjunction with new products being brought to market, potentially broadening options for industry and consumers. In providing prawn farms with diversification and therefore greater economic stability the project is contributing towards rural and remote business resilience and economic opportunities.

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