Last year husband and wife Ned and Anna DeLoach of BlennyWatcher.com were diving in Indonesia when they and one of their dive buddies happened upon a interesting sight: a ball of juvenile striped catfish (Plotosus lineatus). Juveniles of this species regularly form ball aggregations of 100 fish or more for protection from predators. However, the ball itself wasn’t what was interesting. What was interesting was what was inside the ball along with the striped catfish.
A number of juvenile bluespotted trevally jacks (Caranx bucculentus) inside the writhing ball had taken on the black and white striped pattern of the striped catfish. When they showed their photos and video to jack expert Dr. William Smith-Vaniz, he stated that this striped pattern matching the striped catfish coloration had not been observed before and that this was most likely a case of opportunistic mimickry. Most likely the jacks were gaining some protection out of being associated with the large catfish ball and possibly gaining access to food items that were disturbed as the undulating ball moved across the reef.
We thank Anna DeLoach of BlennyWatcher.com for sharing this incredible discovery with us!