Tips for Aquaculture: Understanding Water Quality

Andrew Lawrence | January 19th, 2022

What is Aquaculture
Why is water quality Important
How to achieve good water quality management
Benefits of using ROVs in maintaining good water quality
Contact Industry Specialist

There are many important factors to consider when running a successful aquaculture farm. From fish feed to net integrity to pen location, there are many crucial components farm operators must consider. One such factor is water quality. Poor water quality can be extremely detrimental to overall fish health and growth. Submersible remotely operated vehicles (ROVs) provide operators with a safe, convenient and efficient way to maintain water quality in both net pens and recirculating aquaculture systems (RAS).

How can submersible ROVs (remotely operated vehicles) help aquaculture farms maintain optimal water quality? Read on to learn more.

What Is Aquaculture?

Aquaculture refers to the cultivation of aquatic organisms in controlled aquatic environments for any commercial, recreational or public purpose. The breeding, rearing and harvesting of plants and animals takes place in all types of water environments including ponds, rivers, lakes, the ocean and man-made systems on land.

Aquaculture produces almost half of the seafood consumed by humans globally, a trend that continues to increase. In fact, aquaculture is one of the fastest growing forms of food production in the world. Because harvest from many wild fisheries has peaked globally, aquaculture is widely recognized as an effective way to meet the seafood demands of a growing population. Those in the aquaculture industry are farming all types of freshwater and marine species of fish and shellfish, with the help of remotely operated vehicles for inspection purposes.

Aquaculture serves many purposes, including;

Food production for human consumption
Rebuilding of populations of threatened and endangered species
Habitat restoration
Wild stock enhancement

Why is Water Quality Important in Aquaculture?

Water quality management is crucial for a successful fish farming operation. For the health of the stock, water quality should be closely watched as it can greatly impact fish health, survival and growth. There are many water quality factors that should be monitored and controlled.

Temperature

Water temperature is incredibly important to fish health and welfare as it can directly impact their overall behaviour including feeding, growth and reproduction. The optimal water temperature depends on the type of fish being farmed. For example fish like trout or salmon do best in 48-65 degrees Fahrenheit (8-18 degrees Celsius) while fish like tilapia thrive in waters between 75-90 degrees Fahrenheit (24-32 degrees Celsius). It is imperative that fish are farmed in water temperatures suitable for their specific breed.

For net pen aquaculture, operators are at the mercy of the environment they are operating in. In some cases, the pens can lower to colder temperature zones and raise to higher temperature zones (the sun heats the water at the surface), but they cannot impact the temperature of the water directly.

Suspended Solids

Suspended solids refer to both organic (algae) and inorganic (silt or sediment) materials floating in the water.

Plankton, fish wastes, uneaten feed, or clay particles suspended in the water can all cause problems, especially in recirculating aquaculture systems. Furthermore, fish waste specifically can negatively affect water quality as they contain large amounts of nitrogen which can irritate the fish’s gills.

Clay, soil, silt, sediment or other particles that restrict light penetration can greatly limit photosynthesis. As the process of photosynthesis removes nitrogenous wastes while also supplying oxygen to the water, it is quite important to the overall health of the farm.

Some farms have introduced multi-trophic aquaculture as a method for managing fine particulate waste. Multi-trophic farming is the practice of growing multiple species that benefit from each others’ existence, such as New Brunswick farms that grow salmon, kelp, and blue mussels in the same site.

Dissolved Gasses

The levels of various dissolved gases in the water such as oxygen, carbon dioxide and nitrogen, are critical to fish health and wellbeing. Typically measured in milligrams per litre (mg/1) or parts per million (ppm), monitoring levels of dissolved gasses in the water is crucial for successful fish farming. For example, low levels of dissolved oxygen are responsible for more fish kills either directly or indirectly, than all other problems combined, making the amount of oxygen in the water crucial for fish health.

Temperature and other environmental factors play a role in the amount of dissolved gasses present. While farmers are also at the mercy of their body of water in the case of net pen aquaculture in this case, monitoring these dissolved gasses closely helps inform harvest decisions, site selection, and other important decisions. Most fish farms can utilize permanently installed water quality sensors or drop probes to gather this data.

How Can We Achieve Good Water Quality Management in Aquaculture?

There are many effective ways to achieve good water quality management. Regular sampling and monitoring is important to establish healthy baselines and recognize changes quickly.

Gather Routine Water Samples

Establishing a standardized water sampling protocol is important for overall farm health and success. Routine water samples allow teams to react quickly when normal baseline conditions vary, preventing catastrophic loss.

Deep Trekker ROVs also have tools such as the multiparameter sonde to complete water quality analysis.

Using a remotely operated vehicle provides a safe and efficient alternative for sampling, with built in temperature, depth and oxygen sensors available. It is not common to use a multiparameter sonde on a fish farm for day-to-day monitoring, since you can typically drop your probe in from the surface without a ROV being involved.

Gather Routine Sediment/Benthic Samples

A Deep Trekker ROV provides a useful alternative to divers for effective sediment sampling. In addition to keeping human divers safe and out of potentially hazardous conditions, ROV sampling minimizes the stress more traditional sampling can place on the fish. Gathering samples using a ROV is quick, safe, and easy.

While using a NAV package, you can log where you took samples from and build a report after your dive. Visualize the report on a map and log the readings from your sediment samples to make a report that any stakeholder can understand.

Watch this video to see how our data is logged in .csv and .gpx files:

Site Selection

A ROV comes in handy when wanting to create a profile of an area faster and easier than dropping a probe from a boat. An example of an application where a ROV and a multiparameter sonde is a powerful combination is for site selection and site monitoring. Understanding changes in dissolved oxygen, pH, salinity, chlorophyll, and more can help inform decisions of where to locate farms or changes that happen over the span of an area or over time.

Estimate Fish Sizes

Salmon Farmed in Aquaculture

Estimating fish sizes is important to help operators determine overall fish health, reproduction levels and growth stages while also ensuring that the stock is at a sustainable level.

Equipping a Deep Trekker ROV with a laser scaler provides farm employees with a valuable tool to quickly and accurately track fish sizes. The laser scaler sends out two laser beams 25mm apart from above the camera. Users can then make a reasonable estimate of the object’s size based on the dot spread.

Avoid Site Contamination

In this age of increased microbial risk, it’s imperative that tools enter the water clean and sanitized to prevent any contamination. Utilizing an ROV that can be sanitized prevents the introduction of contaminants into the water. Similar to boot dips and other cleaning practices, submersible ROVs should be cleaned as well. Deep Trekker vehicles can be fully sanitized with a variety of solutions, including chlorine solutions, with no negative effects on the ROV. By using an ROV that can be safely and completely sanitized, users can move from farm to farm without bringing harmful microbes with them. This is especially pertinent when sharing an ROV between sea sites and land-based facilities. Keep water clean and free of contaminants with a Deep Trekker ROV.

Use ROVs to monitor water quality, and general health and welfare of your fish farm

Practice Reliable Feed Monitoring

Feed monitoring plays a massive role in the success of a farm, in terms of fish health and financial sustainability, as well as water quality. Wasted food not only adds more suspended solids to the water but can contribute directly to the growth of algae.

Fish feed also has a direct impact on fish health and welfare. Proper feeding also ensures that fish reach harvest size in a reasonable amount of time. Further, feed regimes are strategically timed based on environmental factors like seasonality, water temperature, prevalence of particular diseases, algal blooms, and so on. Specialty feed types tend to be extremely expensive due to the many supplemental vitamins, minerals and amino acids. For these reasons, it’s imperative that farmers maximize the utility of these feeds.

Farms can make use of their ROV to monitor the feeding of their stock and ensure that they are employing the most efficient feeding practices. Upton detailed feed monitoring with the use of robotics. “Feed is by far the most expensive component at the fish farm,” highlighted Kana Upton of Aqua-Cage Fisheries. Using robotic solutions, Aqua-Cage Fisheries can monitor the feed intake of their stock.

“We’ve been working with Deep Trekker to develop a system to observe fish feeding in excessively warm temperatures,” explained Upton. “What happens when our water temperature reaches about 24 or 25 Celcius, which is surprisingly warm for our area, the larger fish who are getting the most feed don’t like to come up to that surface water, where it really piles up and heats up in that top metre or two. Instead they like to hang out at a cooler temperature down deep. This could be 20, 30 feet deep.

In more typical conditions, personnel are able to observe and monitor feeding behaviours from the feed boat. However in these warmer conditions the fish don’t come up to the surface, making observation from the feed boat impossible. “The problem is the fish are hanging out at depth and we can’t observe their feeding from the surface,” continued Upton. Using a Deep Trekker vehicle, Upton and her team can conveniently and accurately observe underwater feeding behaviours. “It allows us to better gauge the feed that we’ve rationed for the cages so that we are not underfeeding and allows us to get the fish up to size efficiently,” explained Upton.

Ensure Net Integrity

While it may not be immediately obvious, net integrity plays a significant role in water quality. Clean nets prevent the growth of organisms such as algae and minimizes suspended solids such as silt or soil. Well-maintained nets keep fish safely enclosed within the nets, while keeping other fish and animals out - allowing teams to know exactly what is in their pens. With an ROV, operators can easily make net inspections a part of their daily routine. Consistent net inspections allow pilots to monitor the regular wear and tear on lines, nets and mooring, as well as holes from potential pest incursions. By conducting regular inspections, fish farmers can reduce the risk of escapes.

Upton shared, “We typically use Deep Trekker ROVs to check out net pens for holes, so we’re checking the physical net structure. This is part of our due diligence and maintenance program but it’s also a requirement for the certification that we hold. We also monitor anchors and make sure that everything is still in check.”

In addition to the inspection of nets, Deep Trekker ROVs provide users with a reliable way to temporarily mend holes until a more permanent repair can be made. With the net patch users can quickly repair a net hole to minimize loss until the net can be more permanently fixed. Cristian Aguilera of Deep Trekker SpA elaborated on the net patch kit when he explained, “predators like sea lions cut the nets and our net patching tool allows for quick emergency repairs.”

Aquaculture net

Save Money by Reducing Diver Use

ROVs provide a safe alternative to divers, allowing farm operators to optimize their spending. The use of an ROV in lieu of divers provides farms with benefits in terms of finances, time and most importantly human safety. “It’s a safety concern having a diver in the water no matter what they’re doing,” said Upton. It is important to note that the use of ROVs “is not to get rid of the divers, but protect them,” as stated by Aguilera.

Chilean based Aguilera noted that farms in his area “changed from divers to ROVs about 6 years ago.” Aguilera went on to say that, “most of the things that are done on a fish farm today, whether that be inspections or mort retrieving, are done together with the ROVs.” Upton echoed this sentiment, “there hasn’t been a diver in the water for about 15 years now. Having a scuba diver check these nets presents an enormous amount of challenges. Bottom time is extremely limited at these depths, meaning that you can’t check as many nets in a day. Our regulations have also made it difficult to scuba dive at all without a special license or extensive training and support teams.”

The quick deployment and easy portability of Deep Trekker ROVs allow farms to use a submersible vehicle for smaller tasks that would otherwise require a dive team to complete. Sverre Føyen, site manager for Erko Seafood, noted that the easy and convenient deployment of the ROV allowed him and his team to save money. “Before we bought the ROV we had to contact divers for every little thing, from losing an item in one of the cages or just a quick check,” said Sverre. “I think that I have saved the price of buying the unit a few times since now I can do all the small things that I before needed divers to fix or check.”

Benefits of using Rovs for Maintaining Good Water Quality

By staying on top of nets, anchors and mooring line integrity, as well as quickly repairing holes, Deep Trekker ROVs allow farms to keep their nets in top condition.

In short, an ROV is one of the tools that can greatly enhance your team’s ability to monitor and maintain water quality levels for fish farming. As always our team is available to answer any questions you may have about utilizing ROVs for aquaculture. You can also reach out today for your own customized quote!