Skates make up a huge biomass throughout the North Pacific. In fisheries, they are taken mostly as by-catch and discarded. A new study aims to find out how many of them die.
Currently, management assumes that 100 percent of the mortality, whether retained or discarded. We have anecdotal evidence that’s an exaggeration and it’s likely less.
Daniel Michrowski-
is a researcher assistant at the School of Fisheries and Ocean Sciences at the University of Alaska at Fairbanks. His project aims to get better numbers on how many skates die when caught on long-lines, which account for about 70 percent of skate by-catch. About 60 million pounds of skate are allowed to be taken incidentally in the Bering Sea.
We’ve seen skates coming up with their mouths mangled but they obviously have healed and you see scar tissue and regrowth in certain areas. So just as halibut can survive with possibly losing part of their jaws, we imagine skates can as well.
Michrowski learned in Bering Sea long line studies that handling by the crew is one of the biggest factors. Now he plans to compare rough and careful handling outcomes, and monitor injury recoveries, with skates taken in the Gulf.
So the hooking injuries around the mouth seem to be less severe than when, for example they are being gaffed and ripped off the line or hitting crucifiers and such so those were the initial efforts.And now that we have a very good category of those injuries and how they are generally handled, we are now looking to get some of those skates that are handled either carefully, as you would with halibut or handled in a more standard commercial practice – we want to get both of those groups of skates into the lab to monitor their injury recovery, as well as we’re going to take video recordings of their eating attempts to see if there is any impairment –if it takes them longer to feed, if they’re eating less, or if there’s a time delay between after they are injured till when they start feeding again.
A commercial long-liner is needed to capture live skates in Southeast Alaska waters throughout the summer. They’ll be held for three months at NOAAs Auke Bay lab in Juneau. Michrowski say fishery managers will incorporate the results of the skate mortality study into stock assessments.
By reducing the mortality rate that quota that remains can be used for those who are generally retaining them as well as to cover whatever resulting mortality from discards there are.
The skate study is funded by the Pollock Conservation Cooperative. For more details on Michrowski’s live skate study at our website – www.alaskafishradio.com —
dbmichrowski@alaska.edu (907)-796-5461
