Yellowtail Kingfish is a high priority species for recreational fishers and the basis of an important commercial fishery in NSW. The biological stock structure is reasonably well understood, with genetic analyses showing that the population in Western Australia is genetically distinct from the population along the eastern and southern Australian coasts (Commonwealth, Queensland, New South Wales, Victorian, Tasmanian and South Australian waters) and New Zealand. Tagging studies have confirmed movements between Australia and New Zealand and South Australia to NSW. Therefore Yellowtail Kingfish are assessed through the Status of Australian Fish Stocks (SAFS) initiative at the biological stock level, being two stocks - Eastern Australia and Western Australia.

The most recent (2018) SAFS assessment for the Eastern Australian biological stock of Yellowtail Kingfish was ‘Undefined’, due mainly to knowledge gaps around the degree of mixing throughout this stock which spans more than 3,000 km of coastline. Reasonable data for assessment exists only within NSW, and uncertainty around whether an assessment of that component of the stock reflected the entire stock resulted in an ‘Undefined’ status, with a recommendation that this uncertainty be resolved.

Yellowtail Kingfish within NSW has been assessed as ‘Growth Overfished’ (2003/04 to 2013/14), and current evidence indicates a Depleted stock. There are ongoing discussions within NSW about appropriate management changes that may assist recovery; however these are hampered by the ‘Undefined’ status in SAFS.

The FRDC National Priority 1 aims to reduce the percentage of ‘Undefined’ stocks within SAFS, which also has an objective of providing a roadmap to recovery for ‘Depleted’ stocks. To address both of these and to promote better and more collaborative monitoring, assessment and management across all relevant jurisdictions, there is a clear need to review existing knowledge across the entire stock and to identify areas of uncertainty that require addressing.

Optimised vaccines deliver improved animal health and avoid use of antimicrobials in the production of fish (Sommerset et al., Expert Review Vaccines 2005, 4, 89-101.). Australian YTK Photobacteriosis outbreaks have been reported in association with Photobacterium damselae subsp damselae (Pdd), Photobacterium damselae subspecies piscicida(Pdp) and various Vibrio harveyi(Vh) isolates (Matt Landos, Nicky Buller, unpublished). To support stable production of high quality finfish highly efficacious controls of microbial diseases are critical. Successful examples are currently employed in salmon (Yersinia ruckeri, Vibrio anguillarum) and barramundi (Streptococcus iniae) whereby disease outbreaks drove the need for vaccine development. These conditions are now both well controlled in vaccinated populations and have dramatically reduced reliance on administration of antibiotics.
Currently, crude autogenous vaccines are in use with YTK for control of only Pdd in South Australia and Western Australia with some reported success. Recently Pdp has emerged as a significant pathogen in South Australian outbreaks. Reliable vaccination against Pdp has proven difficult in international experience using traditional autogenous and generic killed vaccine methods, hence increasingly research is exploring DNA vaccination methods to improve protection against this pathogen (Kato et al., Vaccine 2015, 33 (8), 1040-1045). It is also probable that antigenic diversity had been underestimated, given high diversity that recent sequencing technology has revealed in our preliminary research . Preparedness for the emergence of highly pathogenic Pdp strains is prudent to allow rapid controls to be developed, without incurring business-ending losses within the growing aquaculture sector, or having high levels of reliance on oral antibiotics. Genetic sequence data on isolates generated through this project can be used for epidemiological modelling, new rapid diagnostic typing tools and immediate response if disease emergence occurs in other finfish industries. Pdp is acknowledged as a serious pathogen internationally in species including yellowtail, cobia, flounder, seabream, pompano and sea bass. (Andreoni et al.J Immunol Res. 2014).