Dye dispersion study to characterize how sea lice bath treatments disperse from salmon farm cage sites in southwest New Brunswick

Description

This dye dispersion study builds on a similar study from the early 1990s. The project’s main objectives were to estimate therapeutant/dye transport and dispersal patterns from:

• the release site using current meters and drifters,
• a flume tank study to examine the effect of net cages on water flow under control conditions, and
• a field study looking for differences between zooplankton species composition, abundance and mortality within and outside the dye/therapeutant plume.

Dye concentration, drifter and current turbulence data were used to estimate near surface in situ length scales and rates of vertical and horizontal mixing within and downstream of the salmon cage sites. The results of these studies provide additional science-based data to inform environmental risk assessments.

Findings

Sea lice on farmed salmon are often treated with a therapeutant bath. Treatments result in the release of the bath water containing the therapeutant into the ocean. The consequence of releasing the therapeutant into the receiving waters depends upon several factors including the following:

• the distribution, presence and sensitivity of non-target organisms, the toxicity of the therapeutant,
• the dilution and distribution of the therapeutant after its discharge into the environment, and
• the overlap in space and time between the distribution and concentration of therapeutant and the sensitive organisms

The analyses summarized in the Canadian Science Advisory Secretariat report (CSAS 2014/102) explored the transport and dispersal of the substances in the marine environment. The report presented a review of literature and new empirical information concerning the transport and dispersal of therapeutants from commercial tarpaulin, skirt and well-boat sea lice of treatments conducted in the southwest New Brunswick portion of the Bay of Fundy. The empirical information focused on the measurement and initial modelling of the temporal and spatial evolution of the combined dye and therapeutant discharges; the dye was mixed with the therapeutant prior to the combined dye-therapeutant solution being introduced into tarp, skirt and well-boat treatment bath containment volumes.

Publications

Ernst, W., K. Doe, A. Cook, L. Burridge, B. Lalonde, P. Jackman, J.G. Aube and F. Page. 2014. Dispersion and toxicity to non-target crustaceans of azamethiphos and deltamethrin after sea lice treatments on farmed salmon, Salmo salar. Aquaculture 424-425:104-112.

Wu, Y., J. Chaffey, B. Law, D.A. Greenberg, A. Drozdowski, F. Page and S. Haigh. 2014. A three-dimensional hydrodynamic model for aquaculture: a case study in the Bay of Fundy. Aquaculture Environment Interactions 5(3): 235-248.

Bakker, J.A., F. Page, M. Beattie, R. Losier, P. McCurdy, B. Thorpe, J. Fife and K. Brewer-Dalton. 2012.  Mixing within salmon aquaculture netpen tarps and skirts: preliminary results from commercial therapeutant bath treatments conducted in South-west New Brunswick. Aquacul. Assoc. Canada Spec. Publ. No. 20, p.76-79

Page, F., Chang, B.D., Beattie, M., Losier, R., McCurdy, P., Bakker, J., Haughn, K., Thorpe, B., Fife, J., Scouten, S., Bartlett, G. and Ernst, B. 2014. Transport and dispersal of sea lice bath therapeutants from salmon farm net-pens and well-boats operated in Southwest New Brunswick: a mid-project perspective and perspective for discussion. DFO Can. Sci. Advis. Sec. Res. Doc. 2014/102. v + 63 p.

Program Name

Program for Aquaculture Regulatory Research (PARR)

Year(s)

2011 to 2014

Principal Investigator(s)

Fred Page, Research, Scientist, Fisheries and Oceans Canada, St. Andrews Biological Station, Maritimes Region
Email: Fred.Page@dfo-mpo.gc.ca