Scientists discover freaky fish thriving in waters we thought were deadly to life
Science Alert: In the water, it’s getting harder to breathe. Suffocating dead zones with little or no oxygen are pervading the world’s oceans, rivers, and streams.
This phenomenon – which has exploded in recent decades – poses an extinction-level nightmare for marine populations already beset by a complex interaction of human-made menace.
When it comes to these oxygen shortages, however, some fish might not be too bothered.
In a new paper, researchers report the discovery of deep-sea fish who were found thriving in virtually oxygen-less conditions that scientists previously assumed to be deadly. “I could hardly believe my eyes,” biological oceanographer Natalya Gallo from the Scripps Institution of Oceanography explains in a blog detailing the research.
“We observed cusk-eels, grenadiers, and lollipop sharks actively swimming around in areas where the oxygen concentration was less than one percent of typical surface oxygen concentrations.”
In 2015, Gallo and fellow researchers conducted eight dives with a remotely operated vehicle (ROV) on an expedition in the Gulf of California led by the Monterey Bay Aquarium Research Institute (MBARI).
Readings from sensors on the ROV indicated the oxygen concentrations in this environment were between one-tenth to one-fortieth as low as those tolerated by other low-oxygen-tolerant fish.
“We were in a suboxic habitat, which should exclude fish, but instead there were hundreds of fish,” Gallo explains.
“I immediately knew this was something special that challenged our existing understanding of the limits of hypoxia [low-oxygen] tolerance.”
According to the researchers, fish are generally considered hypoxia intolerant due to their metabolic requirements, but clearly some extremophiles swim within their scaly ranks.
Even amongst such exceptional fish, though, the cusk-eel (Cherublemma emmelas) and the lollipop catshark (Cephalurus cephalus) look to be outliers, peaking in number at depths of between 600–900 metres (1,969–2,953 ft).
Alongside these, the researchers also observed the occasional grenadier (Nezumia liolepis) and ogcocephalid anglerfish (Dibranchus spinosus), but in fewer numbers, and seemingly preferring to occupy more oxygenated waters.