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The curious tale of the piranhas that merely eat a few scales off their fish prey

Not all piranhas eat in the feeding frenzies that Hollywood is so fond of depicting. Instead, some species remove and eat just a few scales from their prey. As described in UW News, some of these scale-eaters ram into their unsuspecting prey, while others open their mouths to extraordinary dimensions and use specialized teeth to pry off scales. The wide variety of approaches is captured in a new paper that placed these fish in CT scanners, as part of the Scan All Fish program led by SAFS professor Adam Summers. 

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Forgotten fish naturalist and illustrator remembered in new book

Naturalist Charles Plumier’s work has been resurrected by SAFS Professor Ted Pietsch in a new book Charles Plumier and His Drawings of French Caribbean Fishes. Plumier lived in the era just before Linneaus created his Latin naming system for species names, and as a result, none of Plumier’s detailed painting and descriptions of species were given priority. Prof Pietsch talks in detail about the inspiration for his book with Michelle Ma in an interview posted on UW Today. 

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Applications for Ken Chew visiting professorship in aquaculture ($29,000) to SAFS are now open

The recipient will be awarded with a 2-6 month collaborative visit to SAFS beginning in summer 2018, which covers travel, housing, research supplies and a modest stipend each month, for a total value of up to $29,000. The award honors the many lasting and excellent contributions of Prof Kenneth K. Chew to aquaculture. More details are available here: https://catalyst.uw.edu/workspace/sr320/29938/198514. 

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Costs of processing salmon limit the reward for managing predators and prey together

In Chignik, Alaska, sockeye salmon are preyed on when young by coho salmon; the sockeye support a valuable fishery, but coho do not. A simulation exercise examined whether fishers and processors might make more money if coho were reduced by fishing, under different levels of predation of coho on sockeye. Models suggested that fishers would end up with higher harvests, and make more money, but processors would probably not benefit because of the extra costs of processing low-value coho salmon.  

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Dam removal frees fish to feed in the ocean

Bull trout in the Elwha River have been separated from the ocean for a century, but dam removal in 2012-14 has now freed them to head out to the ocean again. Analysis of stable isotope ratios reveals that bull trout now spend substantial time at sea eating marine prey before heading back to the Elwha River to spawn. This re-emergence of a long-lost life history variation after being landlocked for so many decades, shows that fish species can swiftly adapt and change their strategies when new opportunities arise. 

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Socially aware seabirds are more likely to find food successfully

Animals that are based on a central place, and head out from their to find food, face an especially daunting problem of finding prey when prey are ephemeral and found in unpredictable places. A new model now shows that colonial seabirds foraging for fish like anchoveta can use social information to help them find their prey. Notably, if outgoing birds track the direction of homeward-bound birds, and follow their path back to their last foraging location, they are more likely to end up in prey-rich places. 

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Which fish are you really eating, and how does that affect conservation?

Up to 30% of the time, the true species being sold or served in restaurants is labeled as something else entirely. A new study gathers data on 43 separate papers that DNA tested fish samples to find the actual species being sold, and compared the truth to the species on the labels. The true species identified by DNA was on average 3% less expensive, but slightly more sustainable than the species listed on the labels. 

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Revealed: the ups and downs of sablefish

Sablefish are a highly valuable commercial species that inhabit waters as deep as 750 m in the North-East Pacific. New pop-up satellite tag data now show that they do not stick to the bottom all the time: the majority of tagged fish migrate hundreds of meters up and down in the water column every day. The upward migration occurs at night and is likely because the sablefish are chasing their prey of fish, krill and squid, which are migrate vertically. 

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Designer river flows can benefit native fish over introduced fish species

A new study shows that dams can be designed to benefit native fish, instead of only harming them. Eighteen years of data were collected about river flow, native fish species, and nonnative fish species in a large dryland river basin in the southwestern US, and then analysed to find the best patterns of water release for native fish species. Remarkably, releasing water from the dams in a designer pattern could produce benefits for native fish species that are even greater than the benefits of mimicking natural river flow patterns. 

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Salmon face the opposing forces of fishing selection and natural selection

A 100-year simulation of individuals reveals the opposing forces that fisheries and natural selection play in sockeye salmon in Bristol Bay, Alaska. Natural selection favored the production of longer salmon, but also produced differences between the body type of salmon spawning in shallow streams (where body depth declined) and those spawning in the beaches of large lakes (where body depth increased). 

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