When do fish spawn and when do they eat?

When I was a 14 years old, my football coach took me fishing. When we got to the river, he pulled out a thermometer and held it in the water. "Today is going to be a great day," he said. "We are going to catch 'em up."

I thought he was nuts. Why wouldn't he at least make a few casts to see if we were going to catch a fish? The fact that Coach was also my science teacher made me think of two things: I didn't want to run post-practice wind sprints for asking a dumb question, and I didn't want to fail his class. I kept my mouth shut, but he fortunately continued.

"When the water temperature is at a specific temperature, fish burn off a lot of food and they need to eat. So when the water is between 55 and 65 degrees, the trout we're trying to catch will burn up one stomach full of food per day. When it's colder or warmer, those same trout will burn up one stomach-full of food every four days, and that means they don't need to eat. Today, they need to eat.

"But we also need to know when they spawn, because if they are focused on spawning they won't want to eat. It's just like you and your teammates get distracted when the cheerleaders run on the field."

Since then, a thermometer has been as important a tool as a rod, reel, and line itself. There are some regional variations for both spawning and feeding temperatures, but here is a chart to help you put the ball in the endzone.

Source: USFWA