Summary:

In recent years, the prevalence of multifactorial gill pathologies has increased significantly, causing substantial losses in Atlantic salmon (Salmo salar) aquaculture. Complex Gill Disease (CGD) is a multifactorial gill disorder, resulting from a culmination of exposures such as pathogenic organisms, environmental insults, and farm management practices. Hydrogen peroxide treatments help mitigate diseases such as amoebic gill disease (AGD), however, they have unintended effects on gill health. Extended exposure times can temporarily decrease oxygen consumption and directly damage gill tissue. Increasing ocean temperatures due to climate change have influenced the increased frequency of jellyfish blooms. Depending on the water current or under high pressure net washing, fragments of jellyfish can be dislodged into the water column, releasing nematocyst toxins, causing direct damage to the gill. This study examines gill damage through bath treatments of hydrogen peroxide and jellyfish toxins.

Preliminary results using one-way ANOVA (p < 0.05) and Tukey test have shown with increasing time and decreasing dose, healing is occurring within the gill 24 hours after initial exposure to jellyfish toxins. Additionally, increased gene expression has been seen in oxygen transport mechanisms is dependent on both time and dose exposed to the fish. Further gene analysis will be performed jellyfish toxins to assess cytopathic effect on Atlantic salmon kidney cells (ASK) and on hydrogen peroxide treatments that were repeated or dose dependent exposures. Additional biological responses such as damage, repair, and redox reactions will be analyzed in comparison to histopathological results. By the end of this study, common gene expression patterns associated with stages of CGD will be identified which will aid aquaculture industries in diagnosing and assessing preventative strategies in the field.

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