Mark recapture sampling in the Delaware River in resulted in juvenile sturgeon being marked and four of those were recaptured. The resulting estimate of juvenile abundance that year was 3, individuals. The York River is one of the more recent Atlantic sturgeon spawning populations discovered. Since that time, annual abundance estimates have been calculated, ranging from 52 per year to about per year with a total adult population of approximately individuals.
In the Pee Dee River, side scan sonar imaging was used to estimate a summer feeding aggregation, which may have included fish non-natal to the river, of approximately 1, to 1, adult or sub-adult Atlantic sturgeon in the river during the three day sampling period. Because shortnose sturgeon can grow slightly larger than one meter in length, it is possible that some of these individuals were large shortnose sturgeon rather than sub-adult Atlantic sturgeon.
The Altamaha River supports one of the most robust Atlantic sturgeon populations in the Southeast, The number of juvenile sturgeon produced by these spawning runs ranges from 1, to 2, individuals occupying the river each year, 87 percent of which are 1 to 2 years of age. The population appears to be stable or possibly increasing. Table of Contents St. Recent abundance estimates include: St.
This species, along with the Amur sturgeon Acipenser schrenckii , is now classified as Critically Endangered. Sturgeon can live for up to years and do not reproduce annually, which means they take many years to recover from any population declines. This leads to over-harvesting, both legal and illegal, of many species, which is a major threat to their survival. Also, as they are a migratory group of species, the damming of rivers across Europe, Asia and North America over the past century has led to many sturgeon species losing access to vast areas of their spawning grounds.
One ray of hope for these species is their ability to produce millions of eggs. If proper protection can be put in place this reproductive capability may gradually replenish their populations. Event On 18 March , Dr. It is based on an objective system for assessing the risk of extinction of a species should no conservation action be taken.
Species are assigned to one of eight categories of threat based on whether they meet criteria linked to population trend, population size and structure and geographic range.
Pollution sucked oxygen from rivers. Among the species showing improvement is Atlantic sturgeon, whose range stretches from Florida to eastern Canada.
The population around the Chesapeake Bay was feared to be extinct in the mids. Now, thousands of are believed to be there, according to Virginia Commonwealth University scientists.
Last fall, Matthew Balazik, a sturgeon research ecologist with the university and the U. Army Corps of Engineers, netted more than baby Atlantic sturgeon in the James River — the first seen there in years.
Balazik said. Not every river is seeing improvement. Dewayne Fox, a fisheries professor at Delaware State University, said the Delaware River's population remains low, possibly because of collisions with cargo vessels or dredging on spawning grounds. But overall, Atlantic sturgeon appear to be slowly recovering after a species-wide fishing moratorium went into effect in , according to a assessment by the Atlantic States Marine Fisheries Commission.
The shortnose sturgeon also shows signs of bouncing back. In Maine, scientists have captured about 75 this decade on the Saco River, where they were previously never seen.
In Maine's Kennebec River, the shortnose population nearly doubled from about 5, in the late s to more than 9, around , and it has likely grown since, said Gail Wippelhauser, a fisheries biologist with Maine's Department of Marine Resources. Wippelhauser credits cleaner water: "They used to just dump sewage into the river.
There were paper mills that used to dump chemicals in. Lake sturgeon are waging a slow but steady comeback. The species is benefiting from fishing limits and stocking programs, some by Native American tribes. But dam construction over more than a century has slowed the recovery. One solution has been a fish elevator and tanks that haul them around two hydroelectric dams on the Menominee River, which flows between Wisconsin and Michigan's Upper Peninsula.
The number of Gulf sturgeon is also growing, particularly in Florida's Suwannee River. That population has at least doubled since the mids to about 10, fish. The species still faces various threats including the Gulf Coast's ever-warmer waters, said Adam Kaeser, an aquatic ecologist with the U. Fish and Wildlife Service.
Decimated by dams, only one Alabama sturgeon has been caught since , but DNA tests of river water confirm some are still there. This story was reported by The Associated Press. Already a subscriber? Monitor journalism changes lives because we open that too-small box that most people think they live in. We believe news can and should expand a sense of identity and possibility beyond narrow conventional expectations.
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