Association between a fish and box jellyfish during an encounter with a carcharhinid shark.

Fish-cubomedusa associations are less frequently reported than those involving scyphozoans and are typically limited to larval or juvenile fishes without an explicit predator context. Here, we report an adult fish associating with the cubozoan Morbakka sp. during an encounter with a carcharhinid shark at Magnetic Island, Australia. [Correction added on 03 September 2026, after first online publication: In the previous sentence, "Monodactylus argenteus associated", has been corrected to "fish associating"]. Throughout the observation, the fish maintained close association with the cubomedusa and reduced its distance to the bell and upper tentacle field during the shark encounter. Although behavioural motivations could not be determined from aerial observations alone, the observed change in spatial positioning by the fish was consistent with refuge use, although opportunistic foraging or medusivory remain plausible alternative explanations. [Correction added on 03 September 2026, after first online publication: The preceding sentence has been corrected.] This observation extends previous reports of fish-cubomedusa associations by documenting such an interaction in an adult fish during an encounter with a carcharhinid shark.