The Great Lakes have seen successive invasions by non-native species that alter the ecosystem, including quagga mussels that filter the water and remove nutrients. At least partly as a result of the invasive mussels, Lake Michigan is becoming less hospitable to Chinook salmon, according to a new study led by scientists with the U.S. Geological Survey and Michigan State University.
The scientists concluded that stocking could help sustain a population of Chinook salmon, but that the lake’s ecosystem is now more conducive to stocking lake trout and steelhead salmon. These two species can switch from eating alewife, which are in decline, to bottom-dwelling round goby, another newly established invasive prey fish that feeds on quagga mussels. Continue reading “Invasive species shift Great Lakes ecosystems”→
FRISCO — Threatened Chinook salmon have been able to adapt to many changes over millennia, but climate change presents a big new threat, as many rivers around Puget Sound have seen bigger fluctuations in stream flows during the past 60 years.
“There’s more flooding in late fall and winter,” said Eric Ward, an ecologist at NOAA Fisheries’ Northwest Fisheries Science Center. “This is happening when the eggs are in the gravel or when the juveniles are most susceptible.”
The study, published online in May in the journal PLOS ONE, assessed how vulnerable each freshwater species in California is to climate change and estimated the likelihood that those species would become extinct in 100 years.
“If present trends continue, much of the unique California fish fauna will disappear and be replaced by alien fishes, such as carp, largemouth bass, fathead minnows and green sunfish,” said Peter Moyle, a professor of fish biology at UC Davis who has been documenting the biology and status of California fish for the past 40 years. Continue reading “Global warming will decimate California’s native fish”→
New study suggests shipping traffic a smaller factor
By Summit Voice
SUMMIT COUNTY —Recovering Chinook salmon populations in the Pacific Northwest is probably the key to killer whale conservation efforts, according to new research based on measurements of hormone levels in the marine mammals.
The southern resident killer whales, living in coastal waters of the Pacific Northwest, have been struggling and some researchers think it’s primarily because of increase ship traffic in the region.
Several valuable species have been rebuilt to sustainable levels
By Summit Voice
SUMMIT COUNTY — Federal fisheries experts say that collaborative efforts have helped rebuild stocks of several valuable commercial and recreational fisheries, including Bering Sea snow crab, Atlantic coast summer flounder, Gulf of Maine haddock, northern California coast Chinook salmon, Washington coast coho salmon, and Pacific coast widow rockfish — all fully rebuilt to healthy levels.
SUMMIT COUNTY — Hatchery raised salmon are overwhelming populations of wild-raised Salmon in some of California’s rivers, masking the fact that too few wild fish are returning to sustain a natural population in the river.
“We expected to find hatchery fish, but the sheer number of hatchery fish returning to spawn in the wild is surprising,” said Rachel Johnson, a fishery biologist affiliated with the Institute of Marine Sciences at UC Santa Cruz and with the Bay-Delta Office of the U.S. Bureau of Reclamation. “It looked like a healthy population of fish returning to spawn, but the reality is that without the hatchery fish the wild stocks are not sustaining themselves.”
The study focused on the Mokelumne River, one of the major salmon producing streams for fall-run Chinook salmon in California. Throughout the Central Valley rivers, returning fall-run Chinook salmon numbers have rebounded since a disastrous year in 2007, which led to the unprecedented closure of the commercial salmon fishing season for consecutive years in 2008 and 2009. Continue reading “Hatchery salmon overwhelming natural populations”→