System-specific salmon louse infestation thresholds for salmon farms to minimize impacts on wild sea trout populations
Open Access
- 23 September 2021
- journal article
- research article
- Published by Inter-Research Science Center in Aquaculture Environment Interactions
- Vol. 13, 377-388
- https://doi.org/10.3354/aei00413
Abstract
Salmon lice Lepeophtheirus salmonis from aquaculture can cause negative impacts on sea trout Salmo trutta and other wild salmonids. Long-term records from 5 Irish rivers were used to explore relationships between annual sea trout runs and estimated total number of lice on nearby salmon farms. It was hypothesised that local environmental conditions may result in system-specific differences in realised louse pressure on sea trout. Louse count was thus tested as an absolute number and as a relative pressure, i.e. standardised by farm. When the standardised total number of mobile lice on a given salmon farm in April was above baseline level (50th percentile of observed annual values on that farm), there was a high probability of a below-average sea trout run in the local river. Absolute louse counts did not show an important effect on runs. This finding suggests that salmon farm louse production in spring can have a strong system-specific regulating effect on wild sea trout populations. Total number of lice on a farm was most strongly driven by changes in individual infestation rate, with a lesser effect of stocking density. Thresholds for number of mobile lice per farmed salmon required to maintain total louse count below the baseline varied with stocking density and among systems: greater density required lower infestation rate. Regulations relying on a generic louse threshold to trigger treatment are not sufficient to protect sea trout populations-stocking density and site characteristics must be considered to evaluate system-specific infestation pressure and impacts on wild salmonids.Keywords
This publication has 43 references indexed in Scilit:
- Sea lice as a density-dependent constraint to salmonid farmingProceedings. Biological sciences, 2012
- Relationship of farm salmon, sea lice, and wild salmon populationsProceedings of the National Academy of Sciences of the United States of America, 2010
- Physiological consequences of “premature freshwater return” for wild sea-run brown trout (Salmo trutta) postsmolts infested with sea lice (Lepeophtheirus salmonis)Canadian Journal of Fisheries and Aquatic Sciences, 2007
- Physiological effects of simultaneous, abrupt seawater entry and sea lice (Lepeophtheirus salmonis) infestation of wild, sea-run brown trout (Salmo trutta) smoltsCanadian Journal of Fisheries and Aquatic Sciences, 2006
- A review of the Norwegian ‘National Action Plan Against Salmon Lice on Salmonids’: The effect on wild salmonidsAquaculture, 2005
- Wild salmonids and sea louse infestations on the west coast of Scotland: sources of infection and implications for the management of marine salmon farmsPest Management Science, 2002
- The development of salmon lice (Lepeophtheirus salmonis) on artificially infected post smolts of sea trout (Salmo trutta)Canadian Journal of Zoology, 1998
- The performance of sea trout, Salmo trutta L., stocks from the Burrishoole system western Ireland, 1970–1994.Fisheries Management and Ecology, 1996
- Infestation parameters for Lepeophtheirus salmonis (Kroyer) (Copepoda: Caligidae) parasitic on sea trout, Salmo trutta L., off the west coast of Ireland during 1990 and 1991Aquaculture Research, 1993
- Diseases of wild sea trout in Scotland in relation to fish population declineFisheries Research, 1993