What a CWF project in Yukon will tell us about the state of salmon spawn­ing

Canadian Wildlife - - WILD THINGS - K. BANKS

Just out­side White­horse is the world’s long­est wooden fish lad­der: 366 me­tres long and 15 me­tres high. It trans­ports spawn­ing chi­nook salmon past the White­horse hy­dro­elec­tric plant. Here, amid the roar of the Yukon River, re­searchers with the Cana­dian Wildlife Fed­er­a­tion are tag­ging fish, gath­er­ing data they hope will help solve the puz­zle of the river’s de­clin­ing chi­nook salmon run.

The Yukon River boasts the long­est salmon run in the world. About 100 spawn­ing grounds are spread along its var­i­ous trib­u­taries in the Cana­dian por­tion of the river alone. The chi­nook that jour­ney farthest up­river af­ter ex­it­ing the ocean must swim 3,200 kilo­me­tres against the cur­rent to reach their home streams.

Be­fore 1997, an av­er­age 300,000 chi­nook en­tered the Yukon an­nu­ally. In 2013, only 37,000 fish re­turned. As a re­sult, in 2014, and again in 2015, fish­ing for chi­nook was banned en­tirely on both sides of the Alaska-yukon bor­der, an un­prece­dented move. A mod­est re­bound in 2016 and 2017 when 62,000 made it through to the spawn­ing grounds has raised hopes, but some fish­ing re­stric­tions still pre­vail.

In the past, 10,000 salmon were har­vested an­nu­ally up­stream of White­horse, but in the past few decades only about 1,200 have been pass­ing the dam. Fish con­tinue from here to the spawn­ing grounds and in some cases must still travel an­other 200 kilo­me­tres to reach their home streams. “We’re try­ing to fill in gaps in knowl­edge on ei­ther side of the lad­der,” says se­nior CWF con­ser­va­tion bi­ol­o­gist Nick La­pointe. “We are ex­pect­ing that we will learn all of the places where chi­nook salmon spawn up­stream of White­horse and what pro­por­tion of the pop­u­la­tion spawns where. We also hope to un­der­stand what pro­por­tion of the fish that ap­proach the lad­der pass it, how long this takes and whether de­lays at the lad­der have any ef­fect on mi­gra­tion suc­cess.”—

World’s long­est wooden fish lad­der by­passes the White­horse hy­droel­elec­tric plant Dams are one of the causes of the salmon cri­sis. Salmon need cool wa­ter to sur­vive. Dams heat up the river by de­creas­ing river flow and cre­at­ing huge reser­voirs that soak up the sun.

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