Have you ever taste this kind of sushi? If yes, definitely you’d know this made of Salmon, the common name for many species of fish of the family Salmonidae. However, did you ever ask yourself a question, what is the special characteristic of this delicious fish? It’s their migration.
Salmon, Oncorhynchus, are very different from other fish. While almost every fish can only live in fresh or salt water, Salmon can live in both. They were born in fresh water, live there for the 1st part of their life, migrate and live in ocean when they are older, and finally, when the fish reach their sexual maturity, Salmon make an unbelievable journey to where they were born to spawn.
The eggs are laid in fresh water. After 50-150 days, the eggs will hatch into alevin or sac fry. The sac fry will quickly grow into parr. Salmon will stay in this state for 1 to 3 years then develop into smolt. It is said that only 10% of the eggs can survive to this stage. When the salmon reach the size of 15-20 cm, the salmon start swimming toward the ocean. Salmon will spend some of their migration time in brackish water so that their physical and chemical characteristics have time to change, allowing them to survive in salt water.
The salmon will spend 6 months to 7 years in the ocean, grow up and become sexual maturity in salt water. The fish will change many part of their body including their colour from bright silvery blue to darker colour to attract spawning mate. Then they will make an amazing journey from the ocean to the stream where they hatched to spawn. It is believed that the salmon choose the same stream because “they “know” it is a good place to spawn and they won’t waste time looking for another stream with good habitat and other fish to spawn with” (Western Fisheries Research Center, Questions and Answers about Salmon). The salmon may get hurt, lost or eaten during the journey but mostly, they will make it. However, the methods the salmon use to find their way home is still a mystery. The possible answer is that the salmon can tell the directions in the ocean based on the earth’s magnetic field. Some believes they can “smell” the find their way home. They build their “smell memory-bank” when they start migrating to the ocean as young fish. (Western Fisheries Research Center, Questions and Answers about Salmon). Generally, the salmon will die after spawning as they used all their energy to come back without eating once they enter the fresh water.
– Western Fisheries Research Center, Questions and Answers about Salmon, URL: http://wfrc.usgs.gov/outreach/salmonq&a.htm, accessed on 5 apr, 2010.
– Wikipedia, Salmon, URL: http://en.wikipedia.org/wiki/Salmon, accessed on 5 apr, 2010.
– Picture: Salmon sushi, Jim U URL: http://www.flickr.com/photos/rain-bird/3970689364/, posted on 23 feb 2009
– Picture: Stamp falls, The Rainbird URL: http://www.flickr.com/photos/rain-bird/3970689364/, posted on 30 sep 2009
– Picture: Ikura, Blue Lotus, URL: http://www.flickr.com/photos/rain-bird/3970689364/, posted on 24 sep 2007
– Picture: Injured salmon, Rowanlea51, URL: http://www.flickr.com/photos/rowanlea51/2948075226/, posted on 16 oct 2008.