The use by farm site staff of oxygen probes with data logging technology means that real-time, around the clock data provides them with the information needed to make informed decisions about fish management.
Fish require constant oxygen levels of greater than 70% for optimum growth, said James Rogers, Campbell River South Production Manager. This basic truth of salmon physiology means that a vital element of raising healthy fish needs to be maintaining this key environmental condition.
In previous years, hand-held oxygen meters were used to measure oxygen levels in fish pens. The disadvantage was their limited capacity to provide only a snapshot of what was going on within the pens, as well as providing no information about what was happening at night.
Data loggers, however, are units that are permanently fixed to the side of a net pen and relay water temperature and data related to oxygen levels as well as the percentage of oxygen saturation in the water. The information is transferred via a series of probes to a computer in the on-site office. Basic information is available pen-side, directly from the unit, while more detailed information is logged and accessible through the site’s computer system.
The data is logged into an Excel spreadsheet and can be easily retrieved for any time frame, whether it’s annually, monthly, daily, or hourly. This flexible and thorough method of data collection, along with separate colors for each water probe’s data, means that each pen’s information is captured and available for detailed study at the first sign of potentially worrisome numbers.
This constant flow of information means site staff can be proactive as well as giving them the information required to respond when oxygen levels dip lower than is safe for the fish, said James. An important part of the system is the alarm, which is activated when the oxygen levels in a pen fall below a predetermined level, which can be individually set for each site. This warning has prevented and continues to help prevent fish kills due to low oxygen.
When the information provided by the data loggers shows a drop in oxygen levels, aeration is used, to move water through the pens helping the oxygen levels remain constant, an essential consideration for optimum well-being of the fish.
Activating the diffusers for three to six hours after feeding has also become a common approach to help the fish not only maximize their feed conversion efficiency and to maximize growth, he added.
Every site in the Campbell River area has had the data loggers since last year. The plan is for them to continue to be added company-wide. Craig Sherman installed the first data logger in the CR South area four years ago at Brougham Point.