Lacustrine Sockeye Salmon Return Straight to their Natal Area from Open Water Using Both Visual and Olfactory Cues

Abstract

Mechanisms of the amazing ability of salmon to migrate a long distance from open water to natal streams for spawning are still unknown. Lacustrine sockeye salmon (Oncorhynchus nerka) in Lake Toya offers an excellent model system for studying the orientation mechanism in open water, because mature fish return to the natal area with a high degree of accuracy. First we examined the percentage of fish returning to the natal area after they were released 7 km south of the natal area. Forty percent of control male mature fish and 25% of the fish blinded by injection of a mixture of carbon toner and corn oil into the eyeball were captured in the natal area within 5 days. Forty-four percent of fish with brass rings (control) and 31% of fish with NdFe magnetic rings which interfere with the magnetic cue were captured in the natal area within 3 days. These experiments suggested that, although the number of blinded fish captured in the natal area was less than that of the controls, the difference was not statistically significant. In the fish captured in the natal area within 3 or 5 days, fish which found the natal area using their olfactory cue after random swimming for a long time and returned to that area may be included. Hence we tracked fish telemetrically using an ultrasonic tracking system, and found that mature males released at a long distance (3.6 or 6.8 km) from the natal area swam straight to the vicinity of the natal area. Interference of the magnetic cue by the attachment of a magnetic ring did not affect their direct return. Blockage of the visual cue caused them to move randomly. These data suggest that lacustrine sockeye salmon return straight to the vicinity of the natal area using their visual cue and finally reach the exact homing point using their olfactory cue.

Tracking animals in freshwater with electronic tags: past, present and future

“…Some of the earliest of such studies occurred on Pacific salmon in Japan and involved evaluating homing mechanisms [141] and the endocrinology of migration (reviewed in [142]). Recently, the first example of combining genomic studies with field telemetry of Pacific salmon identified the factors that are associated with migration failure in freshwater [143].…”

Magnetic sense in the Japanese eel, Anguilla japonica, as determined by conditioning and electrocardiography

“…In the rainbow trout, Oncorhynchus mykiss, electrophysiological and behavioural responses to magnetic fields have been demonstrated, and a magnetite-based magnetoreceptor cell has been identified in a discrete layer of the olfactory lamellae (Walker et al, 1997;Diebel et al, 2000). On the other hand, telemetric tracking of the chum salmon, Oncorhynchus keta, in the North Pacific and of sockeye salmon, Oncorhynchus nerka, in a lake in Japan indicated that these fishes do not cue to magnetic fields when homing (Yano et al, 1995;Ueda et al, 1998). Yano et al (1996) were unable to condition landlocked hime salmon, O. nerka, to imposed magnetic fields when an electric shock was used as an associated stimulus and thus concluded that hime salmon have no magnetic sense.…”

Olfactory Discriminating Ability of Lacustrine Sockeye and Masu Salmon in Various Freshwaters.

“…It has been discussed that sensory organs other than the olfactory organ are used by salmonids when they are migrating far from the natal river. Recently, we proposed that visual cues are important for orientation during homing migration in lacustrine sockeye salmon (Ueda et al, 1998).…”