Febuary 2013 Expedition - To shoal or not to shoal
My dive buddy and I notice a peculiar association between a juvenile Goldsaddle Goatfish and a Maori Wrasse. The goatfish and the normally solitary wrasse seemed to form a shoal of two.
Shoaling is a common behavior among fishes that typically involves numerous individuals swimming together. This type of group association is thought to confer protection from predation and among adults to aid in finding mates. Shoals of different species are often observed. However, because it doesn’t pay to stick out in a crowd, these shoals are most often formed by similarly colored and/or shaped fishes. Shoaling is often more prevalent among juveniles, which due to their smaller size are more vulnerable to predation.
Photo: Yellowfin goatfish shoaling in Chagos (c) Charles Sheppard
However, the observed relationship between the goatfish and wrasse, which we spent 25 minutes watching as the two moved about the patch reef, was unusual.
After a few minutes of observation it became clear that the goatfish was actually shadowing the wrasse, which seemed largely unphased by the presence of its companion. The goatfish was seen to regularly break from the association for short bursts of feeding on the substrate and then quickly rejoin the wrasse. Once after veering too far to feed the goatfish lost its partner and was forced to quickly choose a different Maori Wrasse to shadow.
At one point the pair came into the vicinity of another juvenile Goldsaddle Goatfish. I assumed the two would join up and shoal, but instead a seemingly antagonistic interaction ensured. The slightly larger goatfish chased the smaller around an approximately 10 meter square area. After about 2 minutes the chase ended and our subject was found alone perched upon a small dead coral head.
After a short rest our goatfish was seen swimming about from coral head to coral head in search of another associate. It attempted to shoal with a Cleaner Wrasse but didn’t seem to be able to keep up with the fast moving wrasse, and finally swam back to the protection of a coral head. The goatfish continued its search for a minute or so until it found another Maori Wrasse to shadow.
Interestingly, juvenile Goldsaddle Goatfishes don’t seem to be particular about with whom they swim. In fact on another day, I saw a juvenile of this same species swimming with a Bird Wrasse. It seems that these goatfish seek the protection of swimming with others but contrary to expectations, at least as juveniles, they seem to actively avoid members of their own species.
Michelle Gaither
Creole translation:
5eme jour lor chagos , moi ek mo partenaire plonger ine remarker ene connectec estrange entre ene poisson ki apel goldsaddle goat fish ek maori wrasse . d’habitide sa 2 poisson la vivre tout sel mais nou ine remarker ki aster zot nage ensame . mo penser ki zot zot nage ensame acoz pou protege zot contre bane pli gro poisson ou zist pou fer camouade . nou ine suive zot pendant 25 minutes et nou fine remarke bane activiter estrange entre sa 2 poisson la ki d’habitide jamais ensame . apres ki nou suivre zot nou ine remarker ki pli poisson la p casiette pli tipti la . ene la dans a sak fois li pou kit lot la la pou ale manger vite vite après li retourner et si jamais li fine perdi so camouade li pou alle rode ene lot vite vite .