Handling, Stress Affect Fish Farm Salmon - Cortisol Level, Lice Level, Surface Level Restricted or Not

Read the article: https://onlinelibrary.wiley.com/doi/full/10.1111/jfd.13286?fbclid=IwAR1M68aJEHbyDIWllfmpwAK1H1hUioR0rVV4vW5_aEN5gwU4GXKifBltsok.

The point was to establish lice levels and stress levels in farmed salmon under different circumstances.

They concluded:

Our experiments investigated the effect of handling and overcrowding combined with a restricted access to the surface on the attachment of L. salmonis copepodids to Atlantic salmon, suggesting a role of fish stress state in this interaction. Long-term overcrowding had no effect on L. salmonis attachment and did not influence the first stage of the infestation behaviour of the sea louse: recognition and attachment. Nevertheless, overcrowding and restricted access to the surface were shown to increase the N:L ratio of Atlantic salmon, indicative of a long-term stress state in these salmon, thus possibly raising concern about fish welfare after aquaculture procedures that could limit surface access and intensify local fish crowding. Importantly, this study shows that handling procedures influence the susceptibility of Atlantic salmon to L. salmonis copepodids, also proposing an increase in plasma cortisol as one possible aetiology. Many of the current lice management strategies may, paradoxically, increase reinfestation risk by handling or otherwise stressing the salmon. As recently stated by Overton et al. (2019), “the push for effective lice control and preventive strategies that have acceptable fish welfare outcomes are more important than ever,” emphasizing the need for a holistic approach to manage sea lice infestation in Atlantic salmon aquaculture.

In other words, lice are not good for farmed salmon, handing isn't good for farmed salmon, stressing farmed salmon is not good for farmed salmon. Need more be said?

Oh, okay, that includes on-land farmed salmon, except there are zero lice, and there is zero treatment for lice on-land, thus reducing stress, as in cortisol levels.