'Dinosaurs of the Deep' making Great Lakes comeback - The Buffalo News

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'Dinosaurs of the Deep' making Great Lakes comeback

The lake sturgeon is a living dinosaur of sorts. The origin of this interesting species can be traced back 200 million years, maintaining the same physical characteristics as its ancestors. Despite this longevity, our knowledge of these fish is amazingly limited.

To people associated with fish and fishing early on, these fish appeared to be a limitless resource – especially here in New York and the Province of Ontario. Tales of long stringers of sturgeons were backed up with photos and filled area bragging boards in the 19th and 20th centuries. Overfishing for meat and caviar combined with habitat degradation and pollution to whittle away population levels for this fish. In less than 200 years, lake sturgeon numbers were declining rapidly. It was feared that they would soon be going the way of the blue pike (now extinct) and sturgeon became a protected species.

 

Today, lake sturgeon in the Great Lakes are slowly making a comeback to the excitement of fisheries biologists like Dr. Dimitry Gorsky of the Lower Great Lakes Fish and Wildlife Conservation Office located in Basom. Dr. Gorsky has been involved with a lake sturgeon study in the lower Niagara River and Lake Ontario for the last seven years and the early results are certainly impressive to say the least. At the same time, he is compiling a long list of pertinent sturgeon information that will give him and his colleagues data on fish movement, prime spawning areas, diet and general health of these swimming marvels.

After the fish are caught, they are held in tanks until they are ready to be sampled, measured and tagged. They are then released unharmed.

“We are trying to collect as much information as possible,” says Gorsky, a U.S. Fish and Wildlife Service employee. “So far in seven years of utilizing overnight setlines in the Niagara River, we have managed to catch, tag and release in excess of 800 lake sturgeons. The amazing thing is that we have had very few recaptures in our work which gives us a population estimate of around 6,000 to 10,000 fish in the lower Niagara River area alone. We’ve recaptured approximately 54 of those fish, giving us a recapture rate of about seven percent.” Each fish was outfitted with a Passive Integrated Transponder (PIT) tag so that they could keep track of individual fish.

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In addition to every fish being tagged, a total of 70 fish were surgically implanted with acoustic telemetry tags to help follow the fish. Nearly 40 receivers have been placed into the lower section of river – from Devil’s Hole to the Niagara Bar off the mouth of the Niagara River – with most of them being in the Niagara River. The receiver is anchored to the bottom of the river with a concrete block and picks up signals from the tag. When it comes time to collect the data, the researchers simply scuba dive into the river or lake and pick up the information absorbed through the receiver. The researchers will be able to determine things like locations, depth and water temperature, all cross-referenced with the calendar and the fish from each receiver. When compiled, they will be able to get a cross-section of a particular fish for a specified amount of time – an important piece of their lifetime and a better understanding of these gray giants.

Weighing a fish is important and requires taking extra care.

A big part of the study, which will be ongoing for many more years, will be to collect information on reproductive behavior. Biologists are continuing to catch sexually mature fish throughout the study and that natural reproduction has been occurring from 1992 to 2005. In an earlier study of the same lower river area, a total of 91 sturgeons were caught by using a total of 250 setlines. In 2013 alone, a total of 208 sturgeons were caught by using 157 setlines. “We are excited to see these fish getting older,” says Gorsky. “We are in the process of analyzing the data. We can see these fish use the Niagara Gorge for spawning, and generally hang around the mouth of the river on the Niagara Bar. In the next 5 to 10 years, we should be seeing a lot more natural reproduction.”

Fisheries agencies are working together now to collect additional data by using the same style of equipment for research – and sharing information that may come through with any crossovers.

“This is exciting to see everyone working together to collect information on a variety of fish species,” says Gorsky. “New York’s Department of Environmental Conservation (DEC) and other state agencies; U.S. Geological Survey, Fish and Wildlife, as well as  the Ontario Ministry of Natural Resources (OMNR) are utilizing the same receivers and when one of our tagged fish travels within the boundary of a receiver, we are sent the information for our data base.”

Everyone works together with funding and in-kind services through boats and personnel to allow for better management of the lake as a whole. All of the data for all of the Great Lakes receivers go through a central clearinghouse – the Great Lakes Acoustic Telemetry Observation System (GLATOS).

A lower Niagara River sturgeon caught on a trotline.

Another important component of the study is to determine what these fish eat. Its torpedo-shaped body has a mouth that perfect for this bottom feeder, resembling a vacuum cleaner. It makes sense that the study so far has revealed that amphipods (bottom crustaceans) account for 91 percent of all prey items. Round gobies make up 87 percent of the wet mass. That said, they will also feed on crayfish, shiners, worms and will hit just about anything an angler will toss into the water. Sturgeons have been caught on treated egg skein, spoons, spinners, tube jigs and a long list of other terminal tackle. Remember it is illegal to target sturgeon for fish catching, but if you do catch one incidentally, it should be released as quickly as possible, unharmed. Mature adults average between 3-5 feet in length and 10-80 pounds but can occasionally grow as large at 7-plus feet and 300-plus pounds.

The fish is long-lived – up to 60 years for males; up to 150 years for females. Males will become sexually mature at 8 to 12 years of age; females 14 to 33 years of age. The problem for the speedy recovery of these fish in the Great Lakes is the frequency with which they spawn.

Dr. Dimitry Gorsky tags a sturgeon.

“Only about 10 to 20 percent of mature adults spawn in any given year,” says Gorsky. “While we have detectable levels of recruitment observed for year classes between 1995 and 2000, there is a definite lack of young and old age classes as far as our studies are concerned. Our next step will be to look for stronger evidence of recruitment.”

A similar sturgeon acoustic telemetry study is taking place in the upper Niagara River and Buffalo Harbor with DEC and FWS working together. We’ll have a column on that this spring.

The Fishing Beat (Feb. 1)

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