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Sea lice infestation levels decrease with deeper ‘snorkel’ barriers in Atlantic salmon sea-cages

journal contribution
posted on 2023-11-22, 04:29 authored by F Oppedal, F Samsing, T Dempster, DW Wright, S Bui, LH Stien
BACKGROUND: Salmon lice (Lepeophtheirus salmonis) are the most important parasites of farmed salmon. Infective larvae position themselves in the upper part of the water column to increase encounter probabilities with potential hosts. Previous studies have shown that a ‘snorkel’ sea-cage technology protects salmon from infection in surface waters. We tested whether deep snorkels would more effectively reduce lice infestation than shallow snorkels and still uphold adequate conditions for the fish. Five sea-cages (12 m × 12 m) each holding approximately 3000 Atlantic salmon (Salmo salar) (53 ± 10 g) were fitted with snorkels that gave protection from infection for 0, 4, 8, 12 or 16 m. We tested whether reductions in the settlement of new salmon lice copepodids were consistent among four separate infection periods. RESULTS: Lice infestation decreased exponentially with depth in all time periods. Infection levels in shallow snorkels (0 and 4 m) were consistently 4–10 times higher than those in deep snorkels (12 and 16 m). Key welfare and production performance indices were similar across all snorkel depths. CONCLUSION: Deeper snorkels dramatically and consistently reduced infection levels of salmon lice compared with shallow snorkels, without consequences for fish welfare and production performance. Therefore, reducing salmon sea lice encounters using a depth-based barrier is a powerful management tool for salmon farming. © 2017 Society of Chemical Industry.

History

Journal

Pest Management Science

Volume

73

Pagination

1935-1943

Location

England

ISSN

1526-498X

eISSN

1526-4998

Language

English

Publication classification

C1.1 Refereed article in a scholarly journal

Issue

9

Publisher

JOHN WILEY & SONS LTD