Blood may be thicker than water but it isn’t always red

Rising temperatures, commercial fishing bode ill for Antarctic fishes

Chaenocephalus aceratus
Chaenocephalus aceratus. Photo by Bill Baker.

A major project for the 2011 field trip was to try to understand why icefish respond so poorly to rising water temperatures. Earlier research already confirmed the critical thermal maximum for icefish — the temperature at which they start to go belly up — is 55.4 F (13 C), whereas for their red-blooded brethren it is 60.8 F (16 C). For comparison, fish species from more temperate climates can survive temperatures of between 60.8 – 86 F (20 – 30 C).

To the surprise of O’Brien and her team, the reduced oxygen-carrying capacity of their blood is not the reason icefish are more sensitive to elevations in temperature.

Researchers are still trying to figure it out.

Regardless of the mechanism, sensitivity to rising water temperatures is worrisome because western Antarctic surface waters are one of the most rapidly warming regions on earth, O’Brien says. Studies show that the upper water column temperature has increased by 1.8 degrees F (1 degree C) since 1950. This matters because the creatures that live in the ocean there are adapted to very narrow temperature ranges.

Lisa Crockett extracts icefish blood.
Lisa Crockett extracts icefish blood. Photo by Steve Untracht.

“We don’t know how they will adjust to the increase in temperature,” O’Brien says. Her team and other researchers have been able to do tests on just a few species, and of those, only adults. “We don’t know what this will mean to reproduction or to the larval stages of these animals.”

Another reason for urgency is an increase in commercial fishing activity, according to Crockett. Because of overfishing in the world’s oceans, fishermen are going after species they haven’t targeted before. Even in some areas of Antarctica, fish populations have been decimated.

“It’s important that we continue to learn about the organisms that we co-inhabit the planet with,” Crockett says. She compared the situation with the Antarctic fishes to that of the polar bear.

“[The fish aren’t] warm and fuzzy, but understanding how climate change will affect them is no less important. In this case we’re not talking about a resource in the sense of fish meat. It’s a resource for scientific knowledge and gaining better understanding of how animals work.”