Tuesday, June 21, 2011

Sharks In Minnesota !!!??

Shark Tales No More. Live Sharks Caught in Minnehaha Creek
Shortly after Jaws opened in Minneapolis theatres back in the summer of 1975, the number of swimmers using our area lakes and pools plunged significantly. So, when a 10 year-old Minneapolis student approached Minnesota DNR biologist Dan Marais about three fossilized shark’s teeth she had found in Minnehaha Creek, he could only smile to himself. More shark tales, he thought. That is, until he actually saw the teeth.
They did, in fact, come from sharks. However, two of the specimens were clearly not fossils, but teeth shed from a contemporary shark. Curious about the origins, Marais called a colleague at the Department of Fisheries and Wildlife to help identify the teeth and perhaps avoid falling victim to a hoax. What he learned made the small hairs on the back of his neck stand up.
After Hurricanes Katrina and Rita last year, a report by Gulf marine scientists had warned that the enormous amount of pollution back-flushed into the Gulf of Mexico would cause many species of marine animals to either relocate or perish. That expected decimation of the food chain led to warnings of a possible migration of coastal sharks into rivers where a higher oxygen content would support more aquatic life. Specifically, they were watching for the common Bull Shark (Carcharhinus leucas). The stuff of legends, this aggressive shark was already known for its ability to live, feed, and even breed in extremely shallow fresh waters. Bull Sharks had previously been documented as far north as the Ohio River. They have also been attributed to most of the attacks on humans worldwide.
Lab technicians positively identified these two teeth as having come from a two-to-three year-old Bull Shark. However, it was a semi-classified document dated February 12, 2006 from the Wisconsin DNR that really set the wheels in motion. On that date, ice-diving biologists captured a nearly comatose five-foot Bull Shark in Lake Pepin, a widening of the Mississippi River. They were responding to reports from several startled salvage divers of a sleeping, “shark-like fish” in the open cab of a pickup truck that had gone through the ice a few weeks earlier. The Wisconsin divers located the truck in approximately 18' of water with the shark still inside, apparently hiding from the swift current. But the cold water had slowed its respiration and metabolism so much that it was barely alive. After an examination, the fish was tagged with a radio location device and released back into the river (Wisconsin regulations do not allow the keeping or transport of live, non-game fish). Sadly, marine biologists doubt the fish will survive until summer without the needed quantity of minerals and trace elements found in saltwater.
Worried about the negative effect on local recreation a man-eating shark might possibly cause, Minnesota officials ordered an immediate sweep of Minnehaha Creek. On Saturday, March 26, conservation officers began their search below the falls using ultrasonic stun devices to drive any fish downstream and into gill nets strung across the mouth of the creek. Despite catcalls and hoots from park patrons, the team worked downstream throughout the day and into the night. It was difficult work with shallow water and an unusual number of recently downed trees blocking the creek.

A little after midnight, two juvenile sharks were captured along with dozens of rough fish and several spawning Northern Pike. Both sharks were malnourished and docile, but in overall better health than the larger Lake Pepin specimen. The two fish are now in a special hospital tank at the Minnesota Zoo in Apple Valley, undergoing observation and a slow acclimatization back to salt water. The staff there have named them Lenny and Frankie, after two of the characters from the 2004 animated feature, Shark Tale.

This summer, scientists plan to install experimental freshwater sonar devices to watch for sharks in the two-mile stretch of the Mississippi between the Ford Dam and its confluence with the Minnesota River at Fort Snelling State Park.

For the safety of its visitors, the Minneapolis Park and Recreation Board ordered signs prohibiting cliff diving or swimming in or below Minnehaha Falls until further notice.

So what about those two teeth? Technicians dated them by comparing tannin stain penetration to known levels in the Creek. They judge that the teeth had been in the creek for 7-10 years. Long before Hurricane Katrina.

Laura Zimmerley, feeling vindicated nowadays, can be heard humming the theme song from Jaws... Dah duh, dah duh