Homing migration of hime (land-locked sockeye) salmon in Lake Chuzenji

S. Kitamura, K. Ikuta, T. Shikama and H. Nakamura (Nikko Branch)


   A mark-recapture experiment was conducted to examine the role of the senses involved in salmonid homing using land-locked sockeye salmon in Lake Chuzenji, one of the most popular recreational fishing area for salmonids in Japan. The results suggest that sockeye salmon use visual cues from the open water to the mouth of their natal stream, then discriminate the odors of the natal stream by olfaction.


[Objective]
  Salmonids are well known for their ability to return to their natal streams for spawning. It is generally accepted that the juvenile salmon at the smolt stage learn the site-specific odors of their home stream. As adults, they use this imprinted odor memory for homing. Many behavioral experiments have supported this "Olfactory imprinting hypothesis". However, there still remains a possibility that other senses, such as vision play some role in homing since odors of rivers will not extend to open waters. In this study a mark-recapture experiment was conducted to examine the role of senses involved in salmonid homing using land-locked sockeye salmon in Lake Chuzenji.
[Results]
  Adult salmon caught by drag net at the mouth of Shobu-shimizu creek and Senju-shimizu creek flowing into Lake Chuzenji, Nikko, Japan (Wild fish) and mature fish reared in Shobu-shimizu water from eggs (hatchery-reared fish) were used in this study. Fish were anchortagged and released at the conter of the lake or  the mouths of non-home streams. One group of wild fish was visually impaired. Fish migrating into creeks were recaptured by fish traps and checked for their tags.
 Wild salmon showed a 66.7-88.3% of homing rate (number of fish returned to home stream / number of fish released x 100), whereas hatchery-reared salmon and visually impaired wild salmon were 23.3-49.5% and 50% respectively. However, home stream selectivity (retured to home / migrated into revers x 100) was almost 100% in all groups. Homing duration for returning to natal stream from the center of the lake was much shorter in intact wild salmon (5-8 days) than in hatchery-reared salmon (13-38 days) and visually impaired wild salmon (20 days). It seems that hatchery-reared fish and visually impaired wild fish swim randomly and happened to reach the mouth of their natal stream. These result suggenst that sockeye salmon use visual cues from the open water to the mouth of their natal stream, then discriminate the odors of natal stream by olfaction.
 
[Publications]
1) Kitamura, S. (2000). Telemetric observation on the homing migration of sockeye salmon in Lake Chuzenji. Nippon Suisan Gakkaishi, 66(5), 919-920 (in Japanese).
 

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