Search warrants of CN Rail offices executed in B.C. train derailment (article url)
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Salmon play significant role
Nov 23 2006 The carcasses of spawning salmon play a significant role not only to the eagle, but to the productivity of the salmonid ecosystem. Pacific salmonids are aradromous fish, spawning in fresh water but spending their adult life in the ocean. Salmon are found as far south as California and as far east as Siberia. Depending on the species, they spend from one to seven years in the Pacific before returning to the rivers and streams of their birth to complete the cycle. Pacific salmon are semelparous, meaning they die after they spawn. Salmonids spawn in the fall, often migrating hundreds of kilometres up raging rivers and rocky streams to reach their spawning grounds. |
They stop feeding when they reach freshwater and rely on stored fat and muscle to sustain them as they migrate. Physically, their sleek bodies maintain their shape, but the female swells in the abdominal area and her snout slightly elongates.
The male develops a prominent fleshy hump by the dorsal fin, the snout becomes longer and hooked, and the upper jaw elongates. Colour changes occur but are different between species. The backs of the sockeye salmon, for example, change to a brilliant, red colour.
Reaching their destination the females dig nests, or redds, in the gravel and lay their eggs. The males release milt to fertilize the eggs. Spawned out salmon carcasses provide food for insects, fish, birds and mammals, while land and aquatic plants and invertebrates are nourished by the nutrients released.
The eggs hatch in the spring and the young alevins live off the nutrients of a yolk sac until it has been absorbed.
The young salmon, now called fry, swim into the water to find food. Pink and chum fry migrate directly to the ocean. Other types of salmon stay in the freshwater a year before migrating to the sea. For these species a healthy and high quality stream habitat is extremely important. Vegetation along the streams creates shade and supports insects that are food for the young fish. Fallen trees, roots and boulders provide hiding places and keep flood waters from sweeping the fry downstream.
Changes in the environment create major physiological changes, called smolting, in the juvenile salmon. They swim downstream, adapting to salt water in estuaries before heading into the ocean to travel thousands of kilometres before returning to begin the cycle once more.
The Fraser Valley is blessed with an abundance of productive salmon streams that must be protected from the impact of urban development, agriculture and industry if they are to continue to thrive.
