What is a Fish Health Audit?
In BC, fish health management on salmon farms is overseen by an aquaculture veterinarian and involves continuous monitoring and assessment of mortalities and underperforming fish by trained site and fish health personnel. This information is entered into a database owned by the BC Salmon Farmers Association (BCSFA) and a summary is provided to the BC Ministry of Agriculture and Lands on a quarterly basis and posted on the Ministry website. The Fish Health Audit Program provides an assessment of the farm’s health status on the day of audit and checks the validity of fish health monitoring results that have been entered into the BCSFA database.
BC CAHS’s role was as a third-party auditor, representing neither salmon farming nor regulator (government) interests. BC CAHS was responsible for fish health audits during the transition period between the provincial government's Ministry of Agriculture and Lands and the federal government's Fisheries and Ocean's transfer of jurisdiction. BC CAHS collected data during Q2 - Q4 in 2010.
Who conducts the Fish Health Audit?
BC CAHS audit staff have extensive fish health and production/fish culture knowledge. All audit work, with the exception of laboratory analysis, is done on the farm site. The BC CAHS auditor oversees the collection, enumeration and classification of mortalities. Samples for histological, bacteriological and viral analysis are collected by the auditor from any fresh mortalities. Additionally, for each fresh mortality, the auditor notes any external or internal signs that may indicate cause of death or disease. All diagnostic material collected is submitted to Provincial Government Animal Health Laboratory for assessment.
What is the difference between infection and disease?
Many organisms that can potentially cause disease (known as pathogens) in fish are common throughout the marine/aquatic environment. Disease occurs when a pathogen (bacteria, virus or parasite) infects and multiplies within a host resulting in negative health consequences for and sometimes death to the host.
For a pathogen to cause disease 1) the pathogen must be present in the environment and must infect the host 2) the host must be susceptible to infection and disease (as with all animals, healthy individuals are less susceptible to disease) and 3) the environment must be conducive to the presence and growth of the pathogen in the host organism. Thus, even if a pathogen is present, individual fish may become infected, but not develop disease.
As well, a pathogen may be the primary cause of disease or may be secondary to (the result of) an underlying condition. For example, gill damage as a result of plankton blooms may leave a fish susceptible to secondary bacterial infection.
For farmed salmon, health is managed at a population level rather than on an individual basis as disease in one individual does not necessarily result in disease in the population. As such, one or a few fish may test positive for a disease, but mortalities in the population will remain low if the disease is not prevalent throughout the population.
In addition to disease, farmed fish mortalities can result from environmental causes (for example, toxicity or gill damage from plankton blooms), from mechanical damage (for example, rubbing against net pen structures and equipment during storms) and can occur when individual fish adapt poorly to the marine environment (called 'poor performers').
How is the Fish Health Audit conducted?
The audit process divides farming areas into fish health zones and sub-zones (as determined by the BC Ministry of Agriculture and Lands: full document here) and separates the calendar year into quarters (January-March, April-June, July-September, and October-December). In each quarter, salmon farm companies provide the names of active Atlantic salmon farm sites in each fish health zone and software is used to randomly select 25% of farms from each zone for audit.
On the audit day, data is collected on environmental parameters, fish population numbers and the auditor oversees the collection, enumeration and classification of mortalities in each net pen. The auditor collects samples from all fresh mortalities and these samples are analyzed by histology, bacteriology and PCR (tests for the presence of specific genetic materials) to determine the cause of death and/or to confirm the presence of any pathogen.
What does the audit tell us?
The audit provides data about those factors that may affect fish health (temperature, dissolved oxygen levels, recent plankton blooms), determines the probable cause of mortality in individual fish and assesses the health status of the farmed population on the day of the audit.
Ultimately, the Fish Health Audit Program is a check that fish health data reported by salmon farming companies is consistent with the auditor’s results; that farm staff are conducting their mortality assessment appropriately; and that the fish health statistics entered into the BCSFA database are credible.
Annual Fish Health Reports (from 2003 to 2009) can be found on the Ministry of Agriculture and Lands website.
Quarter 3 – 2010 Fish Health Audit Results
Table 1 and Table 2 - Q3 Diagnosis Summary and % Daily Mortality on Audit Day
Table 3 - Summary of % Daily Mortality and Cumulative % Mortality by Category during Quarter 3
Quarter 4 - 2010 Fish Health Audit Results
Table 1 and Table 2 - Q4 Diagnosis Summary and % Daily Mortality on Audit Day
Table 3 - Summary of % Daily Mortality and Cumulative % Mortality by Category during Quarter 4
Quarter 1 - 2011 Fish Health Audit Results
Table 1 and Table 2 - Q1 Diagnosis Summary and % Daily Mortality on Audit Day
Table 3 - Summary of % Daily Mortality and Cumulative % Mortality by Category during Quarter 1