Jellyfish May Affect Climate by Stirring Oceans

Jellyfish pulsating through oceans could actually influence Earth’s climate.

A small, fist-sized jellyfish pulsating through the water seems like an unlikely candidate to alter Earth’s climate.
But its motion, combined with all the swimming creatures in the sea, could stir things up enough to do exactly that, according to a new study.
Scientists have wondered for over a century whether the agitations of fish, whales, plankton and jellyfish across the planet can affect ocean currents. But teasing their effect out from the powerful influences of the wind and tides has proven difficult.
Kakani Katija and John Dabiri of the California Institute of Technology in Pasadena have found a clue in Jellyfish Lake, a quiet salt lake in the South Pacific archipelago of Palau.
Swarms of stingless jellies migrate through the still waters there each day, providing researchers with a perfect opportunity to watch them up close as they swim.
By adding dye to the water, the researchers uncovered a surprise: jellyfish move water in two ways. Their bell-shaped heads push small swirling smoke rings out behind them, as expected, but they also drag a cone of water with them wherever they go. When moving vertically, they even manage to tow denser water toward the surface.
“We were expecting to see the vortex rings, but not the conical structure,” Katija said. “Their body shape allows them to mix water efficiently.”

For Tank Fish Two Is Not Enough Company

Watching a fish or two swim around a tank can be relaxing for you — but surprisingly stressful for the fish.
A new study found that common aquarium fish fight more and act less like themselves when they’re lonely. Just as people choose to squeeze into a crowded nightclub rather than roam around an empty bar, it seems, certain fish prefer to have lots of companions.
It was the first study to look at the well-being of fish in home aquariums, and the results suggest that we may owe more to our fish than just keeping them from going belly-up.
“I think we need to make sure they are not only alive,” said Katherine Sloman, a fish biologist at the University of Plymouth in the United Kingdom. “I think we need to get them to display behaviors they might show in the wild.”
Advocates for the welfare of animals talk about five freedoms: freedom from hunger and thirst; freedom from discomfort; freedom from pain, injury and disease; freedom to express normal behaviors; and freedom from fear and distress.
How many of those things fish can actually experience is still up for debate. Some still controversial evidence suggests that fish might feel pain.
Other studies have quantified ideal stocking densities that produce the largest number of big, healthy animals in fish farms. Whether fish can be happy or not is something we may never know, but people who spend a lot of time with fish can tell normal behavior from the abnormal.