Fish fry are a primary food source for a wide range of amphibians, insects, animals, and even the fish themselves. Without proper protection, you may lose all of your fry to various predators and self-feeding behaviors. Preventing both predation and cannibalization requires the use of time-tested techniques designed to address the risks to your pond.
Competition for Food
Some insects and animals that move into the pond won’t eat fry directly but still consume the algae and phytoplankton they need to move on from the smallest stage of development. Increased competition for food from overstocking also increases the risk of cannibalization. Fish fry grow unevenly when there’s too much competition between them for food, resulting in a few large fish that eat the smaller fish when necessary. Sticking to generous feeding rates leads to the expected growth rates for profitable production.
Carnivorous Fish and Animal Predators
If you’re using raceways and other flow-through nursery ponds connected to open water sources, you may end up with carnivorous or omnivorous fish entering the space. Even fingerlings and juvenile fish of other species can decimate your fry stock within hours if they can make it into the pond. From flexible nets to complex stepped lock systems, there are multiple ways to keep unexpected predatory fish out of the pond.
Animal predators like mink, muskrat, water birds, and even neighbor cats may come by to sample your fish as they grow. Fry are generally too small for these predators to want to catch, but they attract more attention as they reach the fingerling stage.
Hanging and Floating Nets
Fine mesh nets that hang just over the surface of the water or even float on it are a good option for keeping predators of all kinds away from your fry. These meshes and nets won’t help against insects that can lay their eggs near or on the water, but it does keep away birds and animal predators. Make sure the net won’t catch fish rising to the surface for air or to eat.
Controlling Cannibalization Among Fry
There are three general methods to prevent fry and fingerlings from eating each other as they grow. First, provide plenty of food and clean the pond more often than usual if you notice build-up of uneaten material. Underfed fish are much more likely to turn to eating each other. Second, remove fish growing faster than the rest and move them to separate nursery ponds or tanks as much as possible. Fish reaching the fingerling size a week or more before their siblings are the most likely to eat smaller fish. Finally, don’t overstock your pond. Understocking the rates recommended for your chosen species by 20-30% will leave enough space for smaller fish to escape the larger and hungrier ones.
