Come by and learn about coho salmon transitioning into fry.
In our lobby at the Gulf of Georgia Cannery, we are raising coho salmon in a tank for all visitors to see. Since January, we have been participating in the Department of Fisheries and Oceans’ Salmonid Program. Over this time period, the coho have grown from eggs to alevin and now into fry. To reach this latter stage in their lives, there are a few fascinating biological transitions the alevin go through.
Up until the fry stage of their lives, salmon sink. To swim up to the surface, they must flutter their tails very quickly. At the surface, they swallow large gulps of air to fill their swim bladders for the first time. Swim bladders are like small balloons that hold in air so the fry can easily swim up and down. The alevin and fry live at the bottom of the tank until they have enough strength to reach the surface for air.
Alevin transform into fry when they absorb their orange yolk sacs. Without a yolk, fry must find their own source of nutrients. Once able to swim, they are capable of chasing food. In the wild, fry prey on small insects, krill, plankton and other micro-organisms.
In nature, herons, dragonflies, and water beetles prey on fry. In streams and rivers, fry swim at night and hide during the day to avoid these predators. At this stage, their skin adapts and changes. Parr lines, dark lines that develop on their sides, help them blend in with their gravel surroundings.