Short-range homing in a site-specific fish: search and directed movements

Abstract

SUMMARYSedentary and territorial rockfish of the genus Sebastes exhibit distinctive homing ability and can travel back to an original location after displacements of metres or even kilometres. However, little is known about the behavioural and sensory mechanisms involved in homing. Although our previous study demonstrated that nocturnal black rockfish Sebastes cheni predominantly use their olfactory sense for homing from an unfamiliar area, the possibility of using landmarks in a familiar area cannot be discounted; i.e. site-specific fish are likely to use three-dimensional spatial memory for navigation and orientation. Using high-resolution acoustic telemetry, we investigated whether S. cheni exhibit distinctive homing paths. Results show that all of the eight rockfish increased their effort within a small area of an unfamiliar region around the release site just after displacement, suggesting that the rockfish probably searched for the homeward direction. The rockfish showed the search movement in the upstream and/or downstream direction, which did not lead home. Finally, after returning to their familiar area, the rockfish exhibited more directed movements with faster speeds at a shallower depth, which was similar to the depth utilised in daily life as well as that of the fish capture.

Simultaneous observation of intermittent locomotion of multiple fish by fine-scale spatiotemporal three-dimensional positioning

“…It is possible the tagged fish used an olfactory cue from their habitat, similar to salmonids [ 36 – 37 ]. For instance, black rockfish Sebastes cheni perform back-and-forth movement in the direction of the current (intermittent locomotion with 180° turns) to detect their homeward direction using olfactory cues [ 11 ]. The tagged fish may have sensed an olfactory cue related to the current direction, for instance, an odour of conspecific females from their original location due to the spawning season.…”

“…Within the array, the probability of location of the tagged fish was 69.1±15.3%, which was relatively low compared to that of the stationary test (83.6±14.0%). The positioning interval, however, was 7.4±1.7 s, giving an estimate of tagged fish locations at least once every ~10 s. Conventional biotelemetry systems typically set their signal transmitting interval between 30–120 s to minimize collisions (see [ 40 ]); for example, during the simultaneous observation of moving routes using a conventional biotelemetry system, Mitamura et al obtained positional data sets of the homing behaviour of four black rockfish ( Sebastes cheni ) at time intervals of 60 s or greater [ 11 ]. CDMA MAP technology, which has simultaneous positioning capabilities, was able to localise ~75% of transmissions at 15 s intervals, such that there was an estimate every 20 s on average [ 17 ].…”

“…Turn angles in ‘stop’ phases were categorised into two types, first-half turns and second-half turns, according to our hypothesis that the tagged fish would display movement with angled turns during the first half of their return based on the documented searching behaviour of homing fish (e.g. [ 11 ] and [ 28 ]). If the tagged fish stayed overnight in their travels, movement until 30 min after sunset and from 30 min before sunrise were categorised into the first half and the second half, respectively.…”

“…These positioning methods have revealed the details of behaviour and movement of tagged individuals using positional information (e.g. homing behaviour [ 10 – 11 ] and movement patterns [ 12 – 13 ]). Behavioural intermittence (e.g.…”

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“…Acoustic telemetry has been used to assess a wide range of research questions, such as movements of hatchery-reared fish after release (Mitamura et al, 2008), schooling behaviour around fish aggregating devices (FADs) (Mitsanuga et al, 2013), homing ability after displacements (Mitamura et al, 2012), evaluation efficiency of marine protected areas (Knip et al, 2012), harvest selection of behavioural traits (Olsen et al, 2012), effects of water pollution (Thorstad et al, 2013b) and movements of escapees from aquaculture fish farms (Chittenden et al, 2010;Solem et al, 2013). The method has also been used in a range of basic descriptive studies of fish behaviour in sea, estuaries and fresh water (Bendall et al, 2005;Naesje et al, 2007;Wang et al, 2012).…”