North Atlantic Salmon Conservation Organization | est 1984


Sea lice model for the sustainable development of Atlantic salmon fisheries and aquaculture: LiceTrack

This project proposes to develop a sea lice integrative model developing and refining hydrodynamic modelling, environmental variables, sea lice production on salmon farms and other data requirements to support sustainable development of aquaculture and wild salmon stocks. Existing modelling tools have been developed in Norway and Scotland. These models simulate dispersal of larval sea lice based on farm production, hydrodynamics, water temperature and salinity, and have been used to identify the role of specific salmon farming sites as recipients or sources of sea lice. In order to make directly comparable estimations of lice dispersal, and hence larval concentrations and infection pressure, the models need to be standardised.

The work carried out in each country can also benefit from the exchange of ideas to ensure optimal solutions are arrived at. For this reason, we will seek to form a network that will meet with the objective of developing a standard model that can be plugged into any hydrodynamic model of local currents to generate sea lice dispersal patterns. This project will contribute to developing best management practice for sea lice control and define a range of production strategies aiming at reducing the presence of sea lice and their negative impacts, both on farmed and wild Atlantic salmon.

Progress to Date

A second project workshop took place in Ireland in February 2018. An update was given on progress with model development in Killary Harbour. The proposed model builds on a previous hydrodynamic model produced for the Killary area. The proposed model uses a horizontal spacing with 64 m (DTM: 320 x 100 grid cells) and 15 layers in the vertical direction (500,000 grid points). Grid spacing in the upper part of the water column was discussed and further consultation with the relevant project partners on this and other model-related sensitivities will be required. The best approach to integrate the lice data with the hydrodynamic data (e.g. 3D flow field, salinity, turbulence coefficients, wind forcing, particle time-steps, light attenuation) as well as overall model transferability was discussed and IMR agreed to facilitate and advise Irish partners. The resolution and availability of meteorological data for the model was also discussed and it was noted that lice dispersal under a range of meteorological scenarios in Killary is important to elucidate. Stimulus thresholds of lice to light, temperature and salinity and their inclusion in the model were further discussed. It was noted that consideration should be given to localised variations in salinity in Killary which may influence lice survival and dispersal in different areas of the fjord and the potential exposure levels as a result to out-migrating fish.

Progress on sea lice model standardisation and application was discussed under the following areas; the definition of a particle in the model, behaviour of particles at boundaries, lice survival, effects of rate sensitivities, probability of infection, swimming behaviour, and application of standardisation. Vertical currents are not considered in the Norwegian model and the use of surface currents should be sufficient. Furthermore, infection rates are temperature and time dependant and that < 50% of lice are considered ineffective (e.g. <5oC there is virtually no infection potential). National University of Ireland, Galway, will require the actual source data from the Killary area (e.g. stock abundance in the fish farm). Project partners will continue discussions on model standardisation.

A brief overview on sea lice research and model development in home countries related to the implementation of the model in Killary Harbour was presented. A presentation was given on Sea lice and model development at the Institute of Marine Research, Norway, including an overview of the “Traffic Light system”. A presentation was given on Sea lice work in Marine Scotland Science. The use of eDNA to calculate the abundance of copepodid lice was discussed. It was recommended by the Norwegian Institute for Nature Research to collect samples using a filter pump, this is preferable to using plankton tows. Pumps can be attached to the sentinel cages in four or five locations at 4-5 metres depth. There is an 80-90% detection rate using eDNA. The standardisation in the collection and counting of lice data on fish to populate models was discussed, as was the value of non-destructive sampling of sea lice on fish (field counts vs lab counts). The Institute of Marine Research, Norway, commented that field counts are best, otherwise lice can be lost, particularly the young stages of lice and freezing of samples can miss 20% of lice present.

Considerable progress was made in 2018 on development of a standard model through the LiceTrack project. A scientific paper entitled ‘A standard sea lice particle model for application in coupled hydrodynamic-particle models’ was prepared for publication in December 2018. It is expected that the manuscript will be published as a major scientific paper in 2019, a significant output of one of the core objectives of the LiceTrack project. The publication is:

Murray, A.G. et al. Submitted. A standardised generic framework of sea lice model components for application in coupled hydrodynamic-particle models. Environmental Modelling and Software.

Total project cost (including in-kind contributions): €618,604

EU contribution to the International Atlantic Salmon Research Fund: €239,994

Partners: Inland Fisheries Ireland. In-kind contributions from the Norwegian Institute for Nature Research and the Institute of Marine Research, Norway; Marine Scotland Science; and the National University of Ireland, Galway.