Early Sturgeon Data Show Unexpected Results

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7-Foot-Long “Minerva” Breaking the Rules

It began as an ambitious project in the mid-Hudson River two years ago: to tag Atlantic sturgeon with specialized satellite and sonic devices to track migration and spawning patterns, testing whether conventional wisdom on this ancient fish still applied.

Though it is still too early to make conclusions, researchers at the New York State Department of Environmental Conservation (DEC) have seen surprising preliminary results, thanks in part to a 7.5-foot-long fish called Minerva.

In the spring of 2006 and 2007, DEC marked 20 sturgeon with sonic tags that send a signal to remote receivers when the fish return to the Hudson to spawn. Over the same period, DEC attached satellite tags to 23 sturgeon to gather data about their travel once they leave the river. The first few fish spotted have produced unexpected data about their journey.

SONIC TAGS
It has been thought that sturgeon return to the Hudson every three to five years, based on studies of sturgeon eggs, though no one has actually verified the spawning frequency. So it was a curiosity when “Minerva McGonagall” was found in the river near Stony Point in April – just two years after she was equipped with a sonic tag. Then in May, along came “Arthur Weasley” and “R2D2,”also much earlier than expected. (All the fish tagged in 2006 were given names from the “Harry Potter” series; 2007 fish were named after “Star Wars” characters.)

Arthur Weasley is a male fish found near Hastings-on-Hudson, just two years after he was tagged near Catskill. R2D2 returned even sooner. He was found near Danskammer Point, one year after being tagged in Haverstraw Bay. It’s premature to say whether these quick returns are anomalous.

Minerva has displayed other unanticipated behavior, said Amanda Higgs, estuary biologist with DEC’s Hudson River Fisheries Unit. First, the female beat the males to the Hudson – an unusual occurrence. Second, she didn’t swim straight to the traditional spawning grounds, near Hyde Park. Rather, she dallied near Haverstraw Bay and just recently moved up to the Hudson Highlands, still farther south than she’s supposed to be.

“She’s breaking all the rules,” Higgs said. “Females are supposed to rush to the spawning grounds and then leave. She’s been here for a month and a half.”

The sonic signals from Minerva and other tagged fish are picked up by a receiver anchored near Hastings-on-Hudson. Once the signal is recorded, DEC researchers proceed by boat to track and obtain more data about the fish. This year, DEC’s mobile crew began tracking in early April so as to not miss some of the earlier sturgeon arrivals that may have been missed in 2007 when tracking began later in the season.

The sonic tags will provide invaluable insight on the sturgeon’s use of the Hudson and help DEC’s Hudson River Estuary Program meet its goals for long-term management of the Atlantic sturgeon. These include: identifying spawning areas, determining bottom-type preferences and estimating how long the fish stay in the river during their spawning run. The project is funded by DEC’s Hudson River Estuary Program and Bureau of Marine Resources, along with the Atlantic States Marine Fisheries Commission, in partnership with the U.S. Fish and Wildlife Service. Sonic tagging has continued through the 2008 spawning season.

SATELLITE TAGS
It’s typical for fish to leave the Hudson and go north. Think shad and striped bass. Here again, the sturgeon, so far, have gone against the grain.

“We didn’t expect them to go south,” Higgs said. “They’re doing the opposite of the other fish.”

In general, the satellite-tagged sturgeon have left the river in summer, lingered in New York and New Jersey waters for a while, then moved south to either the mouth of the Delaware River or Chesapeake Bay. However, two have gone farther.

One male tagged in 2007 made it as far as the Outer Banks of North Carolina. One female tagged in 2006 made it to Georgia.

The tags send a signal every 15 minutes, conveying information about latitude, water temperature and depth. Externally attached to the fish, the tags are programmed to “pop” off after so many months. Supported by a float, the tags drift to a beach where they can be found by their satellite signals. Researchers analyze the data stored on the tags. However, sometimes the journey (weather, other factors) corrupts the data.

A major goal of the study is to learn more about the seasonal migration along the Atlantic Coast. DEC is interested in the particulars of the sturgeon’s voyage (i.e., where on the map, how close to shore, at what depths, etc.). The project is funded by DEC’s Hudson River Estuary Program and Bureau of Marine Resources, along with the U.S. Fish and Wildlife Service, the Atlantic States Marine Fisheries Commission, the Pew Institute for Oceanic Studies and the University of Miami (Fla.). Satellite tagging has continued through 2008.

One of the goals of DEC’s Hudson River Estuary Action Plan (available at www.dec.ny.gov/lands/5104.html ) is for Atlantic sturgeon to show signs of recovery by 2009.

“New York imposed a moratorium on sturgeon fishing in 1996 and convinced other Atlantic Coast states to do the same in 1998,” said Fran Dunwell, coordinator of DEC’s Estuary Program. “Since then, we have aggressively pursued a program of study designed to promote recovery of the species in the Hudson and further protect its habitat.”

Sturgeon belong to one of the most primitive groups of bony fish, having survived since the Mesozoic Era. While some characteristics have changed over time, sturgeon remain basically the same as they have been since their beginning. More information about sturgeon and fish conservation plans is available at www.dec.ny.gov/animals/37121.html. For student lesson plans designed for grades 3-5 using river research to teach basic skills, go to www.dec.ny.gov/education/25386.html.