A Case of Mimicry: Jacks with Catfish

Striped Catfish, Plotosus lineatus, Bluespotted Trevally, Caranx bucculentus ©2012 Ned DeLoachLembeh Strait, Indonesia, March 2011 – I recently posted about my love/obsession with Striped Catfish, Plotosus lineatus. The video that accompanies that post includes clips of soapfish, jacks and even a lionfish feeding alongside the rolling ball of catfish; taking advantage of the disturbance. Ned just rolls his eyes whenever he sees me following yet another swarm. That’s why I was surprised when one of our dive buddies came flying down the reef, gesturing for me to swim back toward Ned, who was giving me the get-a-move-on wave and gesturing at a ball of catfish. Hmmm…he couldn’t possibly be excited about showing me another ball of catfish… it took me a minute to comprehend.Striped Catfish, Plotosus lineatus, Bluespotted Trevally, Caranx bucculentus ©2012 Ned DeLoach

Snapping in and out of the catfish were several tiny jacks that had taken on the striped pattern of the catfish. Ned took photos of this relationship about 7 years ago in this very same bay but the jacks were so tiny that I could not get a decent video image of them.

Back home, our friend, jack expert Dr. William Smith-Vaniz took a look at our images and identified the tiny jacks as Bluespotted Trevally, Caranx bucculentus, and wrote, “The prominent stripes of the trevally juveniles have not been observed previously in the species, indicating alteration of the typical color pattern to more closely match that of the Striped Catfish.” He explains that this is likely a case of opportunistic mimicry and the jacks may benefit both from access to prey flushed out by the swarming catfish and protection from predators. He kindly supplied us with some references on mimicry to enable us to work on a full-length article.

Although we posted Ned’s photos in last year’s Lembeh Strait trip journal, I am just getting around to cataloging the video. You can view this behavioral interaction of the jacks and catfish by clicking here or on the video below.