Above is one of our treatment tanks. We are holding fish at 0, 2, 4 and 6 degrees C, and measuring indices of growth and reproduction.
The big fish on the right side of this holding pen are egg-bearing females. These fish are gravid in early spring and will spawn in a month or so. We let the gravid females back into the Sound.
We sample seven different tissues for a variety of measurements. We can determine what percentage of the cells were actively dividing and how many were in the process of dying. These indices are metrics of growth (actively dividing cells) and a stressed condition (arrested cell division and cell death).
Things are warming up considerably down here. The sea ice is softening and the ice edge, where the open ocean starts is only maybe 20 miles or so north of station. The picture above shows a melt pool of the type that are popping up everywhere. The wall of ice is part of the Erebus glacier tongue. The picture below shows one of the ice caves that opens in the glacier and that we can enter and poke around in.
We have been holding fish at a range of temperatures (from -1.86C to 6C) for a range of durations. We are measuring indices of growth. Amanda has taken a keen interest in the reproductive state of the animals and we will set up tanks that are kept in the dark to mimic winter conditions. We will compare the reproductive output (gamete production) in these fish to those we keep in the light. We are doing a similar experiment also where we are feeding some individuals and starving others to observe the effect of food availability on growth and reproduction. These will hopefully provide preliminary data on the impact of light and food availability on the metabolism and nutritional value of the fish, and we are hoping to relate this to the status of the seals.
Here's a series of clips showing our drilling operation. Amanda and Isaac are using a "jiffy" drill. Watch when they pull the drill out and you can get a sense of the thickness of the ice. The feature behind them is Inaccessible Island. We've caught the bulk of our fish at this site, including five different species.
This video shows the characteristic swimming style of the fishes of McMurdo Sound. Called "labriform" swimming, the lobed-shaped fins "scull" the water. This swimming style is common among fish species that live on the bottom and just make short forays into the water column to eat. In the tanks, the fish are incredibly curious and swim right up to say hi.
The sun has been shining and we've been out fishing 4-5 days a week.
This is one of our exposure tanks. We heat this tank to our experimental temperatures and hold the fish at those temperatures for varying durations. The idea is to get a handle on what the effects of sub-lethal heat stress are on a physiological level.