Abstract
While triploid Atlantic salmon represent a practical and affordable solution to the issues associated with sexual maturation in the salmonid aquaculture industry, empirical evidence suggests triploids are more susceptible to disease and vaccine side-effects than diploids. With vaccination now part of routine husbandry, it is essential their response be studied to confirm their suitability for commercial production. This study tested the response of triploid and diploid Atlantic salmon to vaccination with commercially available vaccines. Triploid and diploid Atlantic salmon siblings were injected with one of three commercial vaccines (or sham-vaccinated) and monitored for performance throughout a commercial production cycle. Sampling at smolt and harvest was undertaken along with individual weight and length assessments through the cycle. Antibody response to Aeromonas salmonicida vaccination was similar in both ploidy, with a positive response in vaccine-injected fish. For both adhesions and melanin, analysis found that higher scores were more likely to occur as the anticipated severity of the vaccine increased. In addition, for adhesion scores at smolt and melanin scores at smolt and harvest, triploids were statistically more likely to exhibit high scores than diploids. Triploids maintained a significantly higher body weight during freshwater and until 11 months post-seawater transfer, with diploids weighing significantly more at harvest. Growth, represented by thermal growth coefficient (TGC), decreased in both ploidy as the severity of adhesions increased, and regression patterns did not differ significantly between ploidy. Vertebral deformity prevalence was consistently higher in triploids (smolt 12.3 ± 4.5%; harvest 34.9 ± 5.9%) than diploids (smolt 0.8 ± 0.5%; harvest 15.9 ± 1.9%), with no significant difference between vaccine groups in each ploidy. This study demonstrates that triploids respond as well to vaccination as diploids and provides further supporting evidence of triploid robustness for commercial aquaculture.
Highlights
Disease is considered one of the most significant constraints to the continued development and success of Atlantic salmon aquaculture, with substantial economic losses caused by increased mortalities, downgrading at harvest and treatment use [1,2]
This study showed that triploids respond as well as diploids to vaccination
Ploidy significantly affected both adhesion and melanin scores, suggesting that triploids may be prone to higher scores than diploids, further studies would be required to fully elucidate these differences
Summary
Disease is considered one of the most significant constraints to the continued development and success of Atlantic salmon aquaculture, with substantial economic losses caused by increased mortalities, downgrading at harvest and treatment use [1,2]. The aquaculture industry has employed numerous strategies to prevent disease outbreaks in intensive farming including improved biosecurity procedures (using reliable egg/fish stocks; water quality monitoring; disinfection of vehicles and equipment) and the implementation of diagnostic tools for early pathogen detection [2,3,4]. With prevention regarded better than a cure, vaccination has become the single most important tool for disease control in the aquaculture industry, with research since the late 1930's resulting in the production of numerous effective aquatic vaccines [13,14,15,16,17]. Vertebral deformities can be evident prior to vaccination but inflammation around the spine, as a result of vaccination and the associated handling has been suggested to aggravate vertebral deformities post-vaccination [21,25,26,27]
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