Aquaculture has a history spanning centuries, but the methods used have been relatively basic for most of that time. In the last few decades, the scientific method been rigorously applied to fish keeping on a commercial scale so that new and more delicate species can be cultured. Each year brings new advancements in aquaculture, yet many commercial fish breeders are still using equipment and systems designed 30 or more years ago. Growing healthy fish, with a profitable survival rate, can seem impossible. It is especially difficult when you’re dealing with old earthen ponds that leak, have long-term disease issues, or can’t support the correct volume of water. Here are the basics of designing a fish hatchery that can support practically any species you want to culture.
Fry, Nursery, and Production Ponds
Whether you decide to use earthen ponds, raceways, or raised round tanks, you’ll need to split the entire hatchery process into at least two to three distinct stages. Most hatcheries begin with eggs, so egg circulation chambers and fry brooding chambers make up the first stage. Even the slowest growing fry tend to outgrow those small fry chambers within a few days to a week, so the nursery tanks or ponds they move into must be ready to receive them from the beginning of a cycle. Some hatcheries end the process here, to ship off relatively small fingerlings to other production facilities. If mature fish are required for harvesting or release into the wild, production ponds are needed. In this third stage, the production ponds are used for sizing up the fish without crowding them.
Steady Supply of Water
No amount of water filtration and re-circulation systems can completely eliminate the need for a steady in-flow of fresh water. Yet, many fresh water supplies used for inland fish farms need extensive conditioning before they’re safe to use with more sensitive fish that require strict quality parameters. Raceways, in particular, tend to use a steady flow design where water enters the system and flows steadily through until it exits again with no re-circulation. Wells and public water supplies can rarely handle the demand of these kinds of hatchery facilities, so raceways are typically located only where rivers and oceans can be tapped for the volume necessary. Make sure to plan around water supply limitations, due to the hatchery location, before assuming any particular design is possible.
Raceway vs Tank and Pond Cultivation
Even if the location for the hatchery supports the use of raceways, they still may not be right for the hatchery. Raceways are long, narrow, artificial ponds, that are generally built outdoors due to their size. A steady flow of water allows for the cultivation of more difficult species like rainbow trout, which don’t grow well when kept in standard tanks or ponds. However, raceways are more expensive to build and maintain than tanks or in-ground ponds. They’re also harder to sanitize and clean than tanks or properly lined ponds. Using flexible liners in raceways, instead of porous concrete, can go a long way in reducing the maintenance costs and repairs required by these hatchery structures.
Indoor and Outdoor Nursery Areas
Almost all hatcheries have some amount of indoor cultivation space, since fish eggs and fry are sensitive enough to need a highly controlled environment. Yet, trying to raise the fish indoors to the fingerling stage or beyond, can immediately explode building costs unless you’re raising small tropical fish. While indoor nursery areas give you more control over the fish and fry with higher survival rates in return, it’s not feasible for larger facilities and hatcheries that plan to grow to a full harvest size. Outdoor ponds are almost always needed for larger facilities, especially if raceways are desired for cold water culture. Most modern hatcheries will combine both indoor and outdoor nursery areas to make good use of both types of spaces. Adding greenhouses and covers may also be an option to protect outdoor ponds and tanks during challenging seasons. No matter where the ponds and raceways will be located, make sure they’re properly lined. Indoor construction requires lining just as much as, or even more than, outdoor structures due to the potential for structural damage.
Target Numbers vs Total Capacity
Sizing the entire hatchery design is a matter of comparing the desired target number of fish per cycle versus the property’s ability to support a certain capacity. This requires detailed information on the specific fish that you plan to culture. A facility for raising tilapia fingerlings may require only a fraction of the space a trout farm needs due to differences in culture requirements. There’s no way to design a generic hatchery, that will provide the same production rates for all fish, due to their inherent differences in needs. Before selecting any particular site, set up general numbers on target production to estimate how many square feet of ponds or tanks you’ll need to accomplish your goal.
Survival Rates
Don’t forget to factor in survival rates when planning for the size and layout of a hatchery. Many common fish species like bream, trout, and sunfish only achieve 50% survival to harvest stage even with the best care. More sensitive species can easily drop to 20% or 30%, leaving you with only a fraction of the fry you introduced to the tank or pond. This allows you to undersize the finishing stages slightly as you’ll lose enough fry before the nursery or production ponds to leave some extra space. Yet, this also means you’re responsible for culling out excess fish if you succeed too well and have a high survival rate. Don’t forget to count and sort fish when moving them from nursery to production ponds to ensure you’re not accidentally overstocking and threatening a die-off of an entire cycle.
Seasonal or Year-Round Production
Most fish hatcheries focus on warm water production, since they can release the fingerlings or small fish before winter comes into another habitat. Year-round production of tropical species is possible in some parts of the world, but cold-water hatcheries are just as feasible with planning. Seasonal fish hatcheries tend to begin just before outdoor temperatures reach the right point. This is because most of the earliest work begins indoors; where temperatures are controlled. By the time the fry are moved to outdoor raceways or ponds, the temperatures should be correct to keep them growing rapidly. Paying to heat large volumes of water to keep fish happy is only profitable for the rarest ornamental fish. Unless you’re planning a conservation facility where the species requirements are not an obstacle, make sure your location matches up with the seasonal needs of the fish you want to produce.
Access for Maintenance
When finalizing your plans for both indoor and outdoor hatchery facilities, make sure you’re leaving plenty of space for maintenance access. It’s all too common to see outdoor ponds and tanks going without repairs and inspections simply because they’re too close together. Leave extra space for all the pumps, piping, bank reinforcements, and other details that come with hatchery structures. Every extra foot of space around a feature will benefit the workers in better ergonomics and safety, especially when walking around on slippery surfaces.
A modern fish hatchery begins with flexible liners. A fish-safe liner, like reinforced polyethylene (RPE), is the best way to control disease, make clean-up a breeze, and keep the ponds stable for years to come. Find a liner you can trust, for even your most sensitive fry and fingerlings, here at BTL Liners.
