Abstract
Rockfish, which are well known for their site fidelity and homing ability, live sympatrically with many conspecifics. Conspecifics may be external drivers influencing rockfish movement, and rockfish may move cohesively while travelling. We tested whether rockfish formed a group when returning to their original habitat after artificial displacement and examined the routes they travelled to return home. A fine-scale multi-individual simultaneous positioning method was used to observe the movement trajectories of tagged fish. Our results showed that tagged fish, released in groups, returned to their original habitat (5 of 8 fish) but generally did not travel with other individuals. There was one exception in which 2 individuals moved together for ~100 s immediately after release. These 2 fish had no designated leader, alternating as leader and follower. Our hypothesis was partially corroborated by these rockfish possibly travelling cohesively. The returning fish tended to travel along the sea bottom and the coastline, independent of current; thus, they likely used visual cues, rather than olfactory or social cues, to return home.
Highlights
IntroductionNavigational ability in anadromous and catadromous fish, such as salmonids (Ueda 2012) and eels (Baltazar−Soares & Eizaguirre 2017), has been well documented
Organisms live in groups on diverse spatial and temporal scales
Using a fine-scale multi-individual simultaneous positioning method, we may have observed cohesive movement by a pair of sympatric conspecific fish with high site fidelity that travelled together briefly immediately after release, the possibility exists that the fish moved synchronously by chance
Summary
Navigational ability in anadromous and catadromous fish, such as salmonids (Ueda 2012) and eels (Baltazar−Soares & Eizaguirre 2017), has been well documented. Research on navigation in schooling fish is scarce, cohesive behaviour is well documented in homing fish, such as salmonids. Orientation ability after translocation away from the reef was compared between shoaling fish larvae and isolated individuals (Irisson et al 2015). This previous study used only ~10 min of observation data following release, which did not cover the entire distance travelled towards the goal
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