— This is one smart little submarine. But maybe not always that smart.
By KIRK MOORE • STAFF WRITER • APP
March 14, 2010
"REMUS is flirting with danger," remarks biologist John O'Herron as the robotic submersible pops up in the Delaware River, smack-dab in the path of a barge pushing upriver.
"It has no idea what's going on up here," says Roland Hagan, a marine technician driving one of two Rutgers University small boats. He explains the REMUS vehicle has taken a break from tracking endangered shortnose sturgeon to pop up and confirm its position: "It only knows that it's on point."
On the other boat, the crew confers by radio with the captain of the Weeks Marine towboat Robert, who throws his diesel engines into a high hum of reverse. The researchers scoot across the channel and retrieve the torpedo-shaped yellow probe, waving thanks to the Robert's crew as they speed back to the dock.
When they get a federal collecting permit, researchers will use nets to catch and release shortnose sturgeons and their cousins, bigger Atlantic sturgeons that are new candidates for the endangered species list, says Lisa Calvo, a watershed coordinator for Rutgers who also heads the Seaboard Fisheries Institute.
"We're trying to build a constituency for sturgeons," says Calvo, whose group got a $25,000 grant from the duPont Corp. for Delaware watershed research projects. "It gets us five or six missions — we'd like eight or 10."
"One of the goals is to identify and mainstream new technologies," says Thomas Grothues, a Rutgers assistant research professor and lead scientist, who's used the REMUS (Remote Environmental Monitoring Units) to track migrating fish. Experiments in the Hudson River showed "the whole idea of coupling all these sensors in a single system is key" for both tracking fish and monitoring their critical habitats, Grothues says.
O'Herron is a consultant on the project and a longtime sturgeon researcher, who in the 1980s estimated the Delaware's shortnose sturgeon population at 13,000. Once they get that collecting permit from the government, the team will net sturgeon, match them to the sonar images read by REMUS and release them back into the water, O'Herron says.
That "ground truthing" helps identify sturgeon compared to the big carp, channel catfish and striped bass that patrol here just down the river from Trenton. Despite their girth and prehistoric appearance, O'Herron says, a shortnose sturgeon, typically 26 to 30 inches long, is "very gentle" in the net. Unlike some other customers.
"About four years ago we netted a grass carp that weighed about 40 pounds and there wasn't a soft spot on it, it was all muscle," he recalls. "It jumped and hit me in the face. It drove my sunglasses into my face, and they stayed there. I saw stars. I was glad it wasn't a swordfish."
Data on a laptop computer show the team what they are looking for. "We detected three acoustically tagged sturgeon. These guys were all from November 2008," says environmental consultant Harold Brundage III, who attached the tracking devices then. "Every 60 to 180 seconds the tag pings. It's a coded pulse that the receiver interpets."
Rutgers scientist Joe DoBarro pulls up images from the REMUS side-scan radar. Sonic echoes converted to a visual format, they clearly showed more than a dozen shapes hovering in the New Jersey side of the river.
"All these remote-sensing systems only show you a large, torpedo-shaped fish in the river. They can't say for sure it's a shortnose sturgeon," Brundage says. "But this far upriver, it's most likely them."
"They seem to select these sites. We're not sure why," Brundage adds. He calls it "a pre-spawning aggregation," and thinks this weekend's rains could be the trigger to the next stage. Sturgeon start to spawn in late March, and it continues into May, he says.
REMUS sensors give researchers the total environment around the sturgeon groups, and "we're going to analyze this very carefully," Grothues says. But there is also a possibility the aggregations are, in a sense, social. "The same reason why geese cluster on just one spot in a great big marsh," Grothues suggests. "They're probably not eating, because it would be insane competition. They may be in a torpor, overwintering in a way that minimizes their energy use."
The five-foot long REMUS has long been used in the Mullica River-Great Bay estuary, and its small size makes it ideal for the Delaware work. Powered by lithium batteries, the autonomous underwater vehicle submerges and cruises about 9 feet off the bottom of the center channel at just over 3 knots, its instruments sampling water conditions as the side-scan creates what looks like an aerial photo of the riverbed.
In the ocean, it has endurance of at least 14 hours and has covered runs of nearly 40 miles. "It will really come into its own on the continential shelf," where REMUS can cruise for a whole day following fish, Grothues says.
MORE THE WEB:
Sturgeon research at www.seaboardfisheries.org