Monday, February 17, 2014

Shortnose Sturgeon Feeding

Sturgeon are ancient creatures, first showing up in the fossil record nearly 200 million years ago. The current Family Acipenseridae, that contains the only two Virginia species of the 23 species, the Atlantic sturgeon A. oxyrhynchus and the shortnose sturgeon A. brevirostrum, has been around for 70 million years! Both species were once abundant in Virginia, but have suffered from overfishing and habitat loss to the point of near extinction; both are listed as Threatened and Endangered. Shortnose sturgeon may temporarily visit Virginia waters from other populations along the East Coast, but are essentially extinct in Virginia, with no viable spawning population left and very few records over the last several decades.
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Shortnose sturgeon eating pellets with a white sucker
We currently house four shortnose sturgeon  here in our James River exhibit and also temporarily displayed Atlantics during our Jamestown exhibit, however they get so large we could not keep them long-term. Over the years, we have also transferred some shortnose sturgeon to other facilities such as the Maritime Museum in Norwalk to give our current animals more space. Sturgeons can get large and live a long time - females may get 60 + years old and over four feet long- so we need space to keep them comfortable for several decades to come. Currently, our sturgeon are approximately 36 - 40" long and nearly 12 years old. We obtained them as juveniles from a hatchery that raised them from Hudson River stock.

Sturgeon have 4 characteristic barbels beneath their snout 

Sturgeon have physical characteristics that make many visitors mistake them for a type of shark. They are not related, but the comparison has merit. Like sharks, sturgeon have a single dorsal (back) fin, and their tails are both heterocercal or asymmetrical (or the top fork is longer than the bottom). Sturgeon also have unscaled skin similar to a sharks, but sturgeons have bony scutes or plates along their bodies that sharks do not. Both are (mostly) cartilaginous and move in a similar sinuous manner. Despite the cosmetic similarities, sturgeons live a very different lifestyle than sharks.They are adapted to life along the bottom and use their fleshy tube-like mouths to suck prey from substrate, rather than having teeth and jaws like sharks. As seen in the videos, the sturgeon actually suck up much more than the food itself; they take in a mouthful of gravel along with whatever food is available and then spit out the inedible portion. They continually search for food and sift gravel, almost constantly on the move. To help them locate food, they have sensitive barbels just in front of their mouths that "smell" food, similar to catfish "whiskers".

 

Sturgeons have survived for millions of years but are facing long odds in the future. They grow slowly and mature very late, meaning it may take ten to fifteen years before the newly born young are even able to reproduce and twenty or thirty years before they join their parents as true reproductive adults. Further complicating matters, sturgeon are anadromous and need unblocked passages to even reach their traditional spawning grounds. If they can defy the odds and make it that far, an adult female can lay from 20,000 to 200,000 eggs based upon her size. These eggs are considered a delicacy to humans - Beluga (sturgeon) caviar costs over $2000 a pound! Unfortunately, human activity has altered the riverbanks to such a degree that viable spawning grounds are exceedingly rare because their eggs need clean silt-free gravel in which to develop.But these fascinating fish have outlived humans by millions of years, so they are obviously survivors. Lets just hope we havent yet pushed them past the point of no return. Come see our shortnose sturgeon in the flesh in our James River exhibit!
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