Forsøksdyr: Caligus elongatus lab cohort for larvae production

Godkjenningsdato 05.09.2018

Salmon lice (Lepeophtheirus salmonis and Caligus elongatus) represent a substantial obstacle for the sustainability of salmon farming. Understanding the fluctuations in abundance and behaviour of lice larvae in plankton can facilitate the development of predictive tools to assist farmers in management of preventative measures, as well as helping to validate models of larval dispersion which in turn can be used for area management and long-term choice of site locations. However, larval distribution (both spatially and temporally) is heavily influenced by factors such as environmental conditions (e.g. temperature, salinity, and light), hydrodynamics, connectivity between farms, and natural mortality. To address these parameters in the field entails the enumeration of lice larvae in complex plankton samples. Current methods to process plankton samples is traditional microscopy, which is time-consuming and limits how many samples can be collected.

Fluorescence microscopy is being developed as a potential solution, and our collaborators in Scotland are going to conduct a full investigation, for L. salmonis, into a wide range of excitation wavelengths and preservation methods, and use of additional wavelength emission filters to reduce noise. IMR is responsible for conducting parallel investigations on planktonic stages of C. elongatus, with a total of 30 tests.

We aim to create a lab strain of C. elongatus, and require 60 Atlantic salmon on which to hold the lice. C. elongatus is not as virulent as L. salmonis, and so mild to moderate distress is expected for the salmon, at a lower level than would be expected for L. salmonis infections. We aim to hold a maximum of 1 adult female per fish and 2 pre-adults or adult males, which is not expected to physiologically impact 300-500g salmon. We require the eggstrings from females at multiple time points, and are not confident in the number of eggs produced per female. Therefore, a maximum of 60 females is required to ensure we acquire enough larvae for fluorescence testing. Effort for reduction and refinement of animal numbers is considered with mediating the potential physiological impact of infections.

An enumeration method for lice in plankton samples is highly sought after, and the development of a method will open a vast potential for answering questions about the planktonic stage of both species of lice, for both aquaculture and ecological purposes.