Sharks and Rays

Last Thursday prior to our weekly SCUBA program, we added our two male lemon sharks to the 30,000 gallon Chesapeake Bay tank.

Before moving the sharks, we had to first remove the southern stingray from the exhibit, as skates and rays are natural prey for many shark species. Our presence inside the exhibit helps to disrupt any potential territorial behaviors by the fishes already in the tank and allows us to closely monitor the situation and even to remove the sharks if things go poorly. In holding, these two sharks were very active and rather aggressive; in fact they ate several smaller tankmates, so caution was needed. But so far so good. Inside CBA each shark has established one half the tank as their own "territory", circling near the surface of the tank, always alert for food. They are still fed off tongs three times a week, but get several peices of food each when the fishes in the main tank are fed during the 2pm program. They showed no fear of us during the dive and swam directly in front of me whenever I was near the surface totally unafraid. Juveniles of top predators and animals that get to be very large often are fearless, perhaps instinctively knowing that one day they will be quite formidable.

Are You Feeding?

Probably the most common question we get from the visitors as we work in or around the exhibits is, "Are you feeding?" People love to watch the animals eat so I think the question may be born from wishful thinking. We do have feedings for the public at 11am and 2pm on selected days, but mostly we try to feed the exhibits before we open because feeding usually clouds the water a bit afterwards. Also, some fishes are skittish and will not feed well surrounded by activity; others are being trained for a particular feeding time.

(A typical weekly food order often includes: (clockwise from top) squid, smelt, live clams, and fresh spanish mackerel.)

 The VLM houses over 100 species of both fresh and saltwater fishes of all life-stages so their diets range from flake food to whole herring.

 

(Atlantic herring are a staple for the saltwater fishes, fed out in chunks, fillets, or even whole)



We attempt to mimic as closely as possible what they would eat in the wild, while providing maximum variety coupled with suppliments to ensure proper nutrition. We prepare diets every day and constantly adjust the amounts as the fishes grow. Fishes that prey on other fishes in the wild, often have the ability (and the desire) to eat their exhibit-mates, so we move them often as they become too large or aggressive for a particular exhibit. We also try to keep them well-fed but not fat; it is no simple task to ensure the most passive fishes get enough food while the most aggressive do not get too much. Successful feeding and nutrition - and their ability to be housed together - relies on the fishes' natural ecology.


(Shad roe, salvaged from fresh whole shad we ordered as a food fish, are occasionally fed out for extra nutrition.)



Trip to Duke Marine Lab

Every spring, students from local Christopher Newport University make a trip to the Duke University Marine Lab in Beaufort, NC.  A couple of aquarium employees from the VLM accompany them on the trip to help with identification and to lend an extra hand to the chaperoning professor. This year aquarists Jessi Shupe and Heidi Pankratz were selected to go. The trip, started almost 30 years ago, is a favorite tradition for biology students at CNU.  Students get a chance to experience a boat trip on the RV Susan Hudson that includes trawling and dredging, walking through mud flats in the Beaufort Inlet Channel, and a visit to the North Carolina Aquarium at Pine Knoll Shores.  The aquarium department at the VLM also gets a chance to collect specimens for use in exhibits.

We brought coolers on board to hold collected animals

The trawl allows us to catch species living just above sediment (hake, flounder, crabs) and the dredge pulls up species living in the sediment. The catch from the boat this year was good, but less diverse than usual because of the long winter and cold waters (~55 F).  

Students sort through catch from the dredge

The mud flats we visit are home to a variety of mollusks that thrive in an environment of changing tides, including oysters, whelks, conchs, and clams. We visit at low tide, which allows us to cover more area and find animals to collect.

Jessi fights through the deep mud

CNU student Emily Wolford shows off the lightning whelk she found (eating a clam)

After the boating and trekking through mud flats, students have a lab session that gives them a chance to go through and identify the collected specimens.

Dr. Gwynne Brown, professor of biology at CNU, talks about the water vascular system of sea urchins

The wet labs allowed us to hold our collected animals overnight until the drive back to the VLM

Jessi and I enjoyed a behind-the-scenes tour of the NC Aquarium

Species that we collected for the museum this year included white and purple urchins, lightning and channeled whelk, spider, stone, mud, and portunid crabs, spotted hake, and windowpane flounder. These species will soon be used in exhibits including the "crusty" crustacean tank and the touch tank.

Lemon Shark update

One issue with introducing the lemon sharks is that the loggerhead is still somewhat passive competing for food, while the lemons are aggressive towards everything edible. The sharks are trained with tongs just as the turtle was (see pics below) , but the turtle has not yet established its position (with regards to feeding) in the big tank.

Before they go in, the turtle needs to be able to fend off attempts to take food from it. Sea turtles can inflict serious damage when they want to, but they also need a little attitude and training. The Chesapeake Bay exhibit is over 30 times the size of any previous enclosure it has been in and is filled with many large fishes so as usual it takes a little time before getting comfortable. But it "gets it" a little more each day.