サケ、陸路で海へ　干ばつでトラック輸送作戦が本格化　米

【オロビルＡＦＰ＝時事】米カリフォルニア州では今年、慢性的な干ばつにより例年よりも早く川が干上がっている。名物のマスノスケ（キングサーモン）が川から太平洋へ到達できるよう、大胆な作戦が本格化している──何台もの大型タンクローリーで稚魚を海へ輸送するのだ。（写真は米カリフォルニア州オロビルのふ化場で、職員の手から跳ねるマスノスケ）
　回遊魚のマスノスケは川で生まれ、海で成長する。海で数年過ごした後は生まれた川に戻って産卵し、一生を終える。
　しかし、干ばつにより川の流れが弱かったり、水温が異常に高かったりすると、サケのライフサイクルが乱れかねない。そこで、カリフォルニア州当局は、ふ化場で育てられた数百万匹の稚魚をトラックで海へ運ぶ「先を見越した対策」を講じている。
　サケの陸路輸送は１９８０年代から行われている。しかし、今夏は早くから干ばつに見舞われていることから、当局は輸送の規模を２０％拡大し、４～６月に稚魚１７００万匹近くを輸送する計画だ。
　稚魚を送るふ化場「フェザー・リバー・ハチャリー」は、サクラメント北部のダムの近くに位置し、故郷の川に戻ってきたサケから年間約８００万匹の稚魚を生産する。このふ化場は１９６７年、オロビルダムの上流にあった自然の産卵場所が破壊されたことに伴い建設された。
　カリフォルニア州では今年、すでに５８郡中４０郡以上に干ばつの非常事態宣言が出されている。【翻訳編集ＡＦＰＢＢＮｅｗｓ】
〔ＡＦＰ＝時事〕（2021/06/07-11:33）

With chronic drought drying up rivers earlier than usual this year, California is scaling up a drastic operation to help its famous Chinook salmon reach the Pacific -- transporting the fry by road in dozens of large tanker trucks.
The tasty migratory fish are typically born in rivers, swim to the ocean where they reach maturity and can remain for several years, before returning to their native rivers to spawn and die.
But drought-hit rivers with too little flow or unusually warm water can fatally disrupt that cycle, causing California's fish and wildlife department to take the proactive measure of trucking millions of hatchery-raised juvenile salmon to the sea.
Trucking young salmon to downstream release sites has proven to be one of the best ways to increase survival to the ocean during dry conditions, said northern California hatchery chief Jason Julienne in a recent statement.
While road transportation of salmon dates back to the 1980s, early drought conditions this summer mean authorities plan to boost the size of the operation by 20 percent.
Trucks bearing nearly 17 million young salmon will travel more than 30,000 miles (48,000 kilometers) between April and June, helping the fry avoid streams where many have perished in the past.
One beneficiary will be the Feather River Hatchery, just below a dam north of Sacramento, which produces around eight million salmon fry annually from fish that naturally return to the rivers in which they were born.
The hatchery was built in 1967 to compensate for the destruction of natural spawning sites above the Oroville Dam, with a fish ladder -- a narrow channel around a mile long with man-made steps -- simulating the rapids of a mountain stream.
- 'Don't have any rain' -
The fish will migrate up, because the instinct of the fish is to go upstream when they're ready to spawn, said Anna Kastner, head of the hatchery, on a recent visit by AFP.
On a day in late May, several dozen salmon were crowded at the top of the ladder, ready to be diverted into the hatchery basin where the powerful fish -- who can exceed 50 pounds (22.5 kilograms) in weight -- will be tranquilized for tagging and receive vitamin injections.
Later, salmon ready to spawn will be harvested, and some 20 million eggs placed in incubation trays at the hatchery. They'll make next year's journey back to the Pacific as fry.
According to Kastner, the entire artificial process means survivability in the hatchery is much higher than the river, with around 85 percent of eggs able to produce fish that can be returned to downstream rivers or the sea near San Francisco and Monterey.
Already this summer California authorities have declared a drought emergency in more than 40 of California's 58 counties.
Conditions in Butte County, where the Oroville Dam is located, are classified as exceptional -- the highest category.
Exacerbated by climate change, conditions are likely to deteriorate until rainfall returns in five to six months.
We want to make sure that we have the best available chance for this fish, because we don't know what's going to happen, said Kastner.
We don't have any rain.