Yes and no slabbacks. An inflated or partially inflated air bladder will return a stronger sonar echo than other parts of a fish will, but it is still the fact that the fish, in general, is returning a stronger sonar return while it is in the stronger center part of the transducer beam versus the leading/trailing edges of the transducer beam.

Two fish of the same species pass through the center of a sonar beam at the same water depth. If they are of the same size, shape and orientation to the transducer; the one with the more inflated air bladder would have a more pronounced or thicker central part of the sonar return versus the fish with the less inflated air bladder would.