On an island about four miles off of Kodiak, marine scientists working with the University of Alaska are trying to figure out why Pacific cod stocks are crashing in the Gulf of Alaska. And, how climate change may be affecting the fish when they’re young.
Mike Litzow and, his wife, Alisa Abookire are stuck.
“We have to get some kelp out Liz,” Litzow said.
They’re trying to pull in a beach seine on a soggy gray day on Long Island. But, they’re catching more seaweed than fish as they slowly sink deeper into the shore’s mud.
“Oh no, it’s the freaking mother load,” Litzow said. “This will be our day right here if we aren’t careful.”
This isn’t a normal fishing trip. Litzow and Abookire are both marine scientists and they’re collaborating on a study for the University of Alaska Fairbanks to figure out why Pacific Cod stocks are declining in the Gulf of Alaska and how warming waters may be affecting the species when they’re young.
But to do that, they need cod to study, which is why they’re currently struggling to pull in a net. When the seine’s finally on shore, Litzow begins counting up the catch.
There aren’t any cod among the small flopping fish, but every specimen is still inspected and recorded before they’re tossed back into the water. Litzow says he isn’t surprised they’re not catching any cod today because it’s probably too early for them to come into shore. As it becomes warmer though, more and more fish will begin to appear, including the small cod they’re looking for.
“So, over the winter and we’d set five sets and get like at the low point, 15 fish,” Litzow said. “And then in the summer, if you hit a big school fish you can get like 15,000 in one set.”
Once juvenile cod begin to show up in their net, Litzow says he and Abookire will measure them. Examine the fish to figure out what they’re eating. And, he says, collect the small ear bones, or the otoliths, of the cod, which will be used to determine the temperature of the water the fish grew up in.
“There’s all kinds of information you can get over time once you catch the fish,” Litzow said.
The reason it’s important to collect this data is the Gulf of Alaska has been unusually warm for the past few years. In that time, cod populations have crashed. Cod is an important commercial fishery in the gulf and the quota was recently cut by about 80 percent for 2018.
Litzow says the unusually warm water in the gulf is connected to climate change. And, he believes, the reason the cod population declined so quickly is that juvenile cod couldn’t find enough food to sustain themselves in these warmer temperatures.
But, that’s only a hypothesis right now, which is why Litzow and Abookire are trying to collect as much information that will help explain the collapse.
“As you get a number of years together you can start to understand something about how environmental changes are affecting the population,” Litzow said. “That’s the ultimate goal, but it does take a few years to get enough data to be able to answer questions like that.”
Which means Litzow and Abookire will hopefully be taking a lot more trips to cast their net to see what more they can learn about how cod are being affected by the changing climate in the Gulf of Alaska.