4.2 | Implications for fisheries management
Re-emergence of AVG remains a significant threat to the economic
viability of H. rubra fisheries in south-eastern Australia
(Lafferty et al. 2015; Corbeil 2020). Therefore characterising
the spatial distribution and prevalence of disease resistant genotypes
will help managers identify stocks expected to be either resilient or
vulnerable to AVG re-emergence. Previous population genomic research has
indicated a lack of biological stock structure in these fisheries
(Miller et al. 2016), suggesting that gene flow could contribute
to the spread of adaptive genotypes and resilience of naïve fishing
stocks. However, gene flow from unaffected parts of the fishery could
eventually reduce the frequency of adaptive genotypes over time in the
absence of ongoing selection. Whether selection for resistance will be a
recurring process is still unclear. However, for the first time in a
decade AVG was recorded in 2021, leading to abalone mortalities at a few
proximal fishing locations heavily impacted by AVG in the early 2000s
(Agriculture Victoria 2021). Unlike the first outbreak, animal mortality
and disease spread has been minimal. While environmental and
epidemiological factors may be contributing to the suppression of the
disease (Bai et al. 2019a; Corbeil 2020), it is possible that the
presence of adaptive phenotypes has already reduced the number of
susceptible animals and overall viral load within affected fishing
stocks.
Evidence of panmixia in H. rubra (Miller et al. 2016)
suggests that standing genetic variation is likely to persist within
disease naïve populations allowing for in situ adaptation to
HaHV-1. However, strategic stock augmentation activities, involving the
translocations of animals with AVG resistant genotypes, could
potentially assist the spread of genotypes to reduce risks of
vulnerability across wild fisheries. Also, there may be future
opportunities to biosecure farm fisheries through the establishment of
AVG resistant breeding programs, similar to disease related breeding
programs in other farmed mollusc, crustacean and finfish fisheries
around the world (Ragone Calvo et al. 2003; Kjøglum et al.2008; Moss et al. 2012; Potts et al. 2021). Overall, these
results add to those of Miller et al. (2019) demonstrating
patterns of genetic adaptation across environmental gradients and the
adaptability of H. rubra populations to new environmental
conditions. This is pertinent in south-eastern Australia where rapid
changes in the physical marine climate are threatening commercial
fisheries through shifts in species distributions (Ling 2008; Johnsonet al. 2011), changes in habitat and trophic interactions
(Holland et al. 2021), and risks of infectious diseases (Oliveret al. 2017).