Further developing a zooplankton challenge model for Atlantic salmon (RD149)

Project Summary:

Gill disease is one of the most significant health threats to salmonid culture in the marine environment. Harmful zooplankton, such as cnidarian jellyfish, are thought to play an important role in disease development, but there is a lack of understanding of the interactions between jellyfish and fish gills that can only be obtained through a lab-based challenge model using lab-reared organisms.

In a previous feasibility project, we demonstrated that it is feasible to develop such a challenge model. We were able to produce a pre-determined quantity of jellyfish at a pre-determined point in time, transport them, and challenge salmon with these live jellyfish. The level of gill disease expected did however not develop however, implying that the challenge model needs optimisation.

We plan to develop the challenge model further by 1) varying the jellyfish dose, 2) varying the challenge duration 3) varying the sampling days, and 4) comparing the juvenile life stage of the jellyfish. In addition, we investigate the possibility of rearing different jellyfish and cnidarian species in the lab, focussing on species that harm salmon as per field data from natural challenge events, such as the Muggiaea sp and Obelia sp.

If successful, we will challenge salmon with these species and compare reactions in fish. This work is needed before we can deliver a standardised, reproducible challenge model, which would allow us to investigate multifactorial gill diseases under controlled conditions, develop improved functional feeds or supportive therapies for gill disease and evaluate existing and new mitigation methods.