Splitting Salmon

It is common to hear hatchery folk saying things like, “it’s time to split the steelhead again” or “the fish are getting crowded, let’s split ‘em”. But what on earth does that mean? Rest assured we aren’t cutting the fish in half; rather we are moving fish from one pond into several. 

These steelhead are very crowded and need to be split.

There are a few reason we split our fish here at Dworshak. The main reason is that at some point the fish get too large for their current pond, or there are too many fish in the pond, and become crowded. If fish are crowded they become stressed and are more likely to get sick. Steelhead are more likely to become aggressive and nip at fins when they are crowded so this is another reason to split the fish. Fin loss and fin erosion can also lead to disease. Since our goal is to raise healthy, high quality fish we defiantly don’t want to keep the fish stressed or over crowded.

Crowding fish, the pipe on the left is the inlet to the fish pump.

The process of splitting fish is simple. One person uses an aluminum mesh screen to crowd the fish close together so they can be pumped from their current pond into a vacant pond. The fish make a pass through a computerized fish counter so we know exactly how many fish end up in the new pond. (The video below show how fish move through the fish counter.) Another person controls the speed of the pump and watches the fish counter to be sure there is always just the right amount of fish traveling through the fish counter. If too many fish are being pumped at once the counter can’t keep up and the final ponding number will be off. This can affect feed rates and growth estimates.