| Title | Trout Don't Follow the Weather Forecast | |
| Date | Sunday September 13 2020, @04:30AM | |
| Author | martyb | |
| Topic | ||
| from the this-one-is-for-TheMightyBuzzard dept. | ||
Trout don't follow the weather forecast:
UC visiting assistant professor of biology Michael Booth studied the migration patterns of steelhead, a subpopulation of rainbow trout that migrates to the Pacific Ocean, where the growing fish hunt and feed until they return to their natal freshwater streams to spawn.
While working at the United Water Conservation District, Booth used 19 years of records from a designated fish trap on southern California's Santa Clara River to identify potential environmental drivers that spur some fish to make the arduous trip to the Pacific Ocean. The trap is part of a diversion off the river where fish can be counted and, if necessary, relocated downstream past the river's low or dry spots.
He found that steelhead migration was triggered by the lengthening daylight of spring rather than factors like recent rains, which had little correlation to migration.
[...] Booth said there are big genetic benefits to making the dangerous trip to the Pacific Ocean. Steelhead grow much faster in the food-rich ocean than trout that remain in the freshwater streams. Fish that migrate to the ocean have an advantage in passing on their genes to subsequent generations when they return to spawn, he said.
"A 3-year-old resident trout might be a foot long, but a steelhead might be 3 feet long," he said. "Their fecundity is directly related to size. So the bigger the fish, the more eggs it can make. There's a really strong genetic advantage to making more babies."
[...] "There are a lot of challenges in the Santa Clara River. The water levels go up and down," he said. "This river has a massive sediment load. During a big storm, the river bed can erode 20 feet. The water looks like a smoothie coming downstream."
[...] "We thought the fish would migrate when the river was flowing and wouldn't migrate in years without storm events," Booth said. "It turned out that wasn't the case. They migrated regardless of whether the river was flowing to the ocean."
Journal Reference:
Michael T. Booth. AFS Publications, North American Journal of Fisheries Management (DOI: 10.1002/nafm.10475)
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