As I write this, the crappie are spawning. When you read this, the spawn will be over and the adults moving to their summer homes. For many anglers, crappie season is over. But the number of year-round dedicated crappie anglers appears to be increasing, as is their knowledge of how to catch summer crappie. The results of a crappie movement study by University of Missouri fishery scientists may offer some thoughts to add to your treasure chest of crappie-catching knowledge.
Temperature selection and stratification
Crappie prefer temperatures near 80°F. Mississippi lakes get a lot warmer than that in the summer, and crappie occupy cooler water if they can find it.
Mississippi lakes stratify in the summer. Warm upper waters are separated from cooler lower waters by the thermocline, a layer of water often only a few feet thick with a sharp temperature gradient. The water below the thermocline offer crappie the cool temperatures they prefer but has little oxygen shortly after the lake stratifies. The thermocline, which offers fish cooler waters than the surface water, contains oxygen, so it is here that crappie can find cooler water and have sufficient oxygen to survive. The University of Missouri study adds a few more details to crappie summer location.
Attaching temperature-sensing transmitters to adult crappie, the researchers were able to monitor the crappies’ horizontal movement as well as figure out where the fish were vertically in the water column and what temperature they were occupying.
In Little Dixie Lake, the crappie stayed in the warmest water available until the lake reached 75 degrees. When the average upper-water temperature climbed above 82° F, the crappie selected the coolest water available.
In Rocky Ford Lake, the other lake in the study, the crappie occupied the warmest water until the average upper water temperature reached 82 degrees. Crappie selected the coolest water available when the upper water temperature climbed to 88 degrees.
An obvious application of the results: expect the fish to go to deeper and cooler water some time during the summer. The results also suggest that the depth at which you catch crappie may suddenly change as summer advances and the water warms.
The crappie exhibited movement to cooler water in both lakes, but the temperatures that triggered the movement differed. Why?
The result wasn’t expected, and the study wasn’t designed to test this question, but the difference may be related to habitat.
Crappie orient to vertical cover. Little Dixie Lake has abundant standing timber in open water. Association with the timber allowed them to stay close to their preferred cover while moving up and down to find their thermal comfort zone.
Rocky Fork Lake is deeper and the banks slope steeply into deeper water. The lake lacks standing timber, and the crappie orient to the narrow band of shallow-water vegetation. Without cover in deeper, cooler water, possibly the crappie tolerated warmer water conditions longer before finally moving off cover to cooler water.
Survival is a powerful instinct, and habitat is a powerful factor, whether it is providing cover for a prey fish or a predator, or whether it is concentrating prey for a predator. All fish start their lives small and as forage for just about every meat eater that swims in the lake. Do they ever grow up? When I think about habitat use of a variety of adult sport fish, like crappie and bass, I always wonder if they are still “living small” and seeking refuge from predation.