Saturday, June 29, 2013

Jellies - by Aquarist Patrycja Lawryniuk

Jelly hunting is an work activity that I enjoy the most! Every year the aquarium staff collects jellies from the local waters near to the VLM, such as the York River. Certain jelly species are seasonal and tend to show up in the area at different times of the year. The large colorful lion's mane jellies Cyanea capillata are actually arctic and prefer colder water, and therefore appear in late January to early March. The white jellies that haunt the summertime waters are sea nettles Chrysaora quinquecirrha, which are famous for their stinging tentacles. We can usually rely on sea nettles popping up in early June when the waters start to warm up. However, an unusual amount of heavy rains have kept water temperatures low and pushed their arrival back a few weeks. Since sea nettles are so common in the Chesapeake Bay, the National Oceanic and Atmospheric Administration (NOAA) tracks the ideal conditions for these jellies in the bay, and we are able to view their abundance online!  Finally, in the last two weeks, we hit the jelly jackpot at Grandview Beach in Hampton.

Sea nettles are generally much smaller than lion's mane jellies, but are faster and more aggressive. Their sting can be deadly to their prey, but is no more than a painful irritation to humans and can be neutralized with a small amount of vinegar. Nettles are carnivorous, usually feeding on zooplankton, other jellies, and even small fishes! On exhibit we try to emulate their natural diet as closely as possible. They are fed minced  capelin, shrimp, or squid, with an enriched commercial food called Cyclop- Eeze The prepared food is then mixed with salt water and distributed to each jelly using a turkey baster. Lion's mane are larger and slower, and their sting is not quite strong enough to irritate human skin, therefore they are fed with larger pieces of food which is distributed individually into their tentacles using tweezers.Moon jellies are planktivorous and are fed Artemia nauplii or newly hatched brine shrimp.

Saturday, June 22, 2013

Saltwater collecting season: juvenile lookdowns, sea robins, flounder, etc.

 A summer flounder (~ 2 inches long)

As the weather warms up, the aquarium department takes full advantage of our brief opportunities to catch all the saltwater fishes we will need until next year. Early summer is an excellent time to collect, not only because of the weather; a wide variety of juvenile fishes frequent the shallows as they begin to prey on invertebrates, micro-crustaceans and larval fishes close to shore. These miniature predators are voracious and eat constantly to fuel their rapid growth. Come fall they must be large and healthy enough to survive among the big boys when they will either migrate southward or move into deeper water. During the summer we are able to collect a wide variety of species: summer flounder, lookdowns, puffers, sea robins, black sea bass, jacks with a beach seine, sometimes in the same haul! Many of these species would be much more difficult to acquire as adults, so we seize the opportunity to catch them while we can. There are several benefits to collecting fishes as juveniles - other than convenience - but most importantly juveniles acclimate to captivity much more readily than adults. Below are just a few of the juvenile fishes we collected this season with (hopefully) many more to come.

Juvenile bluefish

 Juvenile lookdown (approximately the size of a quarter)

Juvenile sea robin
Juvenile northern puffer
Juvenile black sea bass