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This document is part of a CSAS process in support of the development of a post-deposit monitoring program for drug and pesticide use at Canadian marine finfish farms. This report focusses on the usage (number of farms treated and amount of active ingredient used) of drugs and pesticides at Canadian marine finfish farms during 2016-2018. Total Canadian marine finfish aquaculture production showed a slight decrease during these years: 148 900 t in 2016; 140 500 t in 2017; and 138 400 t in 2018. By province, 61-63% of the annual production was in British Columbia (BC), 17-20% in New Brunswick (NB), 11-17% in Newfoundland & Labrador (NL), and 4-8% in Nova Scotia (NS); production was >95% Atlantic salmon. The Government of Canada has required marine finfish farms to report their usage of drugs and pesticides on an annual basis since 2016. Data on drug and pesticide use in 2016-2018 were obtained from the National Aquaculture Public Reporting Data (NAPRD) and the Aquaculture Integrated Information System (AQUIIS). The reported drugs (applied in-feed) and pesticides (applied in bath treatments) included antibiotic drugs (oxytetracycline, florfenicol, erythromycin, ormetoprim, and trimethoprim), pest control drugs (emamectin benzoate, ivermectin, and selamectin for sea louse control; and praziquantel for parasitic worm control), and pesticides (azamethiphos and hydrogen peroxide; both for sea louse control). Individual farms used from zero to six drugs and pesticides in 2016, and zero to five in 2017 and 2018. Of the 136-152 active marine finfish farms in each year during 2016-2018, 108-128 (74-84%) used at least one drug or pesticide in each year. By province, 52-58% of treated farms were in BC, 26-30% in NB, 13-18% in NL, and 0-3% in NS. The percentage of active farms that used at least one drug or pesticide was: 83-86% in BC; 69-86% in NB; 74-95% in NL; and 0-38% in NS. Of the five antibiotic drugs reported, florfenicol was used at the most farms (47-50 farms per yr), followed by oxytetracycline (17-24 farms per yr); the other three were used by =5 farms per yr. BC had the largest number of farms treated with florfenicol and the highest quantity used in each year (34-35 farms per yr). The largest number of farms treated with oxytetracycline was in NB in 2016 (10 farms) and in BC in 2017 (7 farms) and 2018 (10 farms); the highest quantity used was in NL in 2016 and 2017, and in BC in 2018. Of the pest control drugs, emamectin benzoate was used at the most farms in all three years (56-70 farms per yr). BC had the largest number of farms treated with emamectin benzoate in all three years (32-38 farms per yr), while NL used the largest quantity in all three years. Ivermectin was used at 14-20 farms per yr and was only used in NB and NL, with NB having the larger number of farms treated and the larger quantity used in each year. Selamectin was used on a trial basis only (one NB farm in 2017 and one NB farm in 2018). Praziquantel was used only in NL, and only in 2016 and 2017. One other sea louse control drug, lufeneron, was used in freshwater hatcheries in BC, NB, and NL. The pesticide azamethiphos was used at 20-42 farms per yr; it was used only in NB and NL. In 2016, NB had the larger number of farms treated with azamethiphos (29 farms) and the larger quantity used; in 2017 and 2018, NB and NL had equal numbers of farms treated (20 farms each in 2016, 10 farms each in 2017), while NL used the larger quantity in both years. Hydrogen peroxide was used at 25-37 farms per yr; it was used in BC, NB, and NL. In 2016, NB had the largest number farms treated with hydrogen peroxide (14 farms) and also used the largest quantity; in 2017 and 2018, BC had the largest number of treated farms (17 in 2017; 22 in 2018) and also used the largest quantity in both years. There were differences in usage between salmon year-classes for some of the chemicals: florfenicol and ivermectin were used primarily on smolts, while emamectin benzoate and azamethiphos were used more on pre-market fish. In BC, treatments with drugs and pesticides occurred throughout the year, while in NB and NL, treatments did not occur in winter and early spring; in NS, the only treatments were in August 2016 and in June-August 2018 (all NS treatments were antibiotics). The three years of data were insufficient to discern clear interannual trends in drug and pesticide use. [ABSTRACT FROM AUTHOR]

Infectious salmon anemia (ISA) has caused severe morbidity and mortality in farmed Atlantic salmon in North America, Norway, Scotland and the Faroe Islands. The Quoddy region of Maine, United States of America (USA), and New Brunswick (NB), Canada is characterized by extensive tidal mixing and close proximity between farms. This region is also prone to recurrent appearances of ISA, though control measures limit disease spread and severity on infected farms. We conducted a retrospective longitudinal analysis of the apparent impact of hydrographics on the incidence and timing of ISA outbreaks on Atlantic salmon (Salmo salar L.) farms in the Quoddy region from May 2002 to August 2004. A time-series cross-sectional regression of 32 farms over 28 months demonstrated a limited, but statistically significant, spatio-temporal clustering of ISA outbreaks linked hydrographically. New outbreaks correlated temporally with those occurring on-site 1 and 3 months prior, and those occurring within one tidal-excursion upstream the same month. Other risk factors included holdover of previous year-class fish, wharf sharing, and possibly harvests of cages infected in previous months. Conclusions suggest that tidal dispersion does play a role in ISAV transmission in the Quoddy region. Dispersal of free virus and/or tidal distribution of lice or other hydrographically influenced vectors or fomites could all contribute to the spatio-temporal patterns described.