Scientists from Scripps Institution of Oceanography and the Monterey Bay Aquarium Research Institute have discovered that two species of fish are capable of living in ocean waters almost completely devoid of oxygen.
Marine biologist Natalya Gallo, a postdoctoral researcher at Scripps, and her colleagues reported high abundances of fish living in deep Gulf of California waters with almost no dissolved oxygen.
The catshark, Cephalurus cephalus, and the cusk eel, Cherublemma emmelas, seem to prefer this seemingly inhospitable environment, and were at times observed swimming over areas resembling bare moonscapes, but were absent from better-oxygenated areas.
The study, “Home sweet suboxic home: remarkable hypoxia tolerance in two demersal fish species in the Gulf of California,” appeared in online versions of the journal Ecology.
The researchers used the remotely operated vehicle Doc Ricketts to survey the habitat and behaviors of fish in the Gulf of California’s oxygen minimum zone, a region more than 3,280 feet deep that is nearly oxygen-free in many places. The southern Gulf of California represents one of the most extreme low-oxygen environments in the world’s oceans.
“I distinctly remember the moment when we went over a ledge with the ROV and saw hundreds of these cusk eels, along with several other species of fish, swimming around,” Gallo said. “I could hardly believe my eyes. We were in a suboxic habitat, which should exclude fish, but instead there were hundreds of fish. I immediately knew this was something special that challenged our existing understanding.”
The researched said the fish likely use a combination of strategies for reducing oxygen demand and increasing oxygen uptake capacity.
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