By Amanda Biederman
Chief Science Correspondent
It was a Wednesday morning just like any other. I had dealt with a minor emergency involving a failing pump on an experimental tank late the previous night, and planned to spend the day preparing synaptosomes.
I walked towards our outdoor tank, where we were holding about twenty Notothenia coriiceps, a red-blooded fish (i.e. "normal") species known commonly as the black rock cod. Compared to its white-blooded (hemoglobin negative) relatives known as the icefishes, N. coriipceps is remarkably hearty.
When I opened up the tank that morning, I gasped. All the fishes were lying, motionless and belly-up, on the tank floor. They were dead.
We left the ship the next morning, one day earlier than planned, headed for grounds where we would hopefully encounter dozens of our target species. We began trawling in the late afternoon, dropping a large weighted net to the ocean bottom for approximately 20 minutes.
Fortunately, it would be a successful trip. We filled all six tanks with fishes, from the trawl nets as well as pots, which we set out the following morning. Most importantly, the fishes seemed to be recovering well from the stress of being captured, dragged and pulled out from the nets.
One of the interesting aspects of trawl fishing is the bycatch, or species that were pulled up in the net alongside the fishes. The net was full to the brim with a number of invertebrate species including sea spiders, sea stars and sea stars. One of the most ubiquitous creatures was a sea star with elongated, tentacle-like arms that seem to resemble (although I'm not positive) Labidiaster annulatus. We also pulled up several giant sea stars, as well as several bones that appear to have belonged to a seal.
Fish maintenance is critical in maintaining these species. The tanks have to be kept clean, and the water must remain at a fairly constant temperature (ideally below 0 degrees Celsius, the freezing point of freshwater). The tanks need to be aerated. We try to feed them, but the icefishes (who lack oxygen-binding hemoglobin in their blood and are thus much more fragile) are often too stressed to eat in their new environment.
Even with our best efforts, not all of the fishes will make it. We lose icefish on a daily basis, to the point where it becomes a race to complete our dissections and experiments while they are still alive, even under ideal conditions. And, as the previous week's events demonstrated, unexpected events can occur at any moment.
But, at least for the moment, everything is going.... swimmingly!