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Scientists examine spawning rates in Mullica River
By JARRETT RENSHAW Staff Writer, (609) 978-2015

LITTLE EGG HARBOR - -Spring for many of the region's fishermen means traveling to the mouth of the Mullica River, better known as Graveling Point, an area believed by many to be the site of the first significant striped bass spawning run of the year.

Opportunistic anglers stand shoulder to shoulder here each March and April, catching the now-hungry, hormone-filled stripers as they make their trek up the 55-mile, pristine river presumably to spawn.

But researchers at the Rutgers Marine Field Station, located along Great Bay and at the mouth of the Mullica River, warn local fishermen that looks may be deceiving.

"We know that stripers run up the river, but we have questions about whether they are successful at spawning," said Tom Grothues, a marine scientist at the facility.

Researchers suspect that environmental conditions, such as swift changes in the river's pH level, water flow, predators and salt levels, may jeopardize the success rate of eggs and larvae within the system.

A 1980s study supports the researchers notion. It found that "despite a considerable number of eggs collected, the capture of only a single 1-year-old adult out of 524 specimens suggests a negligible survival of striped bass young in the Mullica River perhaps due to other environmental factors."

Clare Ng, as part of her pursuit for a doctorate in marine biology at Rutgers, will spend the next three years testing the hypothesis using an array of methods, from the simple collection of eggs and larvae to lip-stick sized acoustic devices placed inside a number of stripers to track their movements up and down the river.

Striped bass - like salmon, sturgeon and some herrings - are anadromous, which means they migrate from salt water to fresh water to spawn. Striped bass spawning behavior is triggered by warm water, anywhere from 60 to 80 degrees. Scientist's can induce spawning in controlled environments by simply increasing water temperature.

When it comes to successful striped bass spawning, the chips are stacked against the popular fish in any environment. Conditions must be near-perfect and any slight changes in the environment present devastating challenges to eggs and larvae.

In the most advantageous environments, the striper egg mortality rate is as much as 90 percent, studies indicate. This causes the female to lay as many as 4.5 million eggs to ensure the success of the species.

One of the most telling indicators of successful spawning, according to several studies and researchers, is a river's pH level.

The Great Bay/Mullica River watershed is a vast, heavily protected and relatively untouched system. It also serves as the primary drainage system for Pinelands, which are naturally acidic.

Striper eggs and larvae are extremely sensitive to sharp changes in pH levels. Numerous studies have found a 100 percent mortality rate when the pH level of water shifted as little as one unit in either direction - acidic or basic.

"We really don't know the exact pH level at portions of the river or the possible shifts in the level, but we will by the end of the project," Ng said.

Flowing river is also critical to the success of striped bass spawning. That helps explain why there is little no natural reproduction of the fish when they are confined to inland lakes, researchers said.

The flowing water keeps the fish eggs suspended in the water long enough to hatch. This typically requires a relatively uninterrupted stretch of flowing fresh water as long as 50 miles, researchers said.

"We are going to look at the speed of the water, any deterrents to egg flow and how long eggs could spend in fresh and salt water," Ng said.

Researchers said they are unsure how long the eggs and larvae spend in fresh water and how long they spend in salt water. If a river is too salty it inhibits larvae to see food.

Another potentially detrimental factor includes the abundance of predators, a situation that escalated last decade when striper numbers declined.

"The stripers have bounced back. Maybe now they are producing enough eggs to be successful and we have missed it. We will see," Grothues said.

Researchers want to know more about the area north of Hogs Island and south of the Forks, considered to be prime areas for striper spawning.

They now have recording devices in this area to measure the movements of the fish. They want to know how long the fish are spending in these areas - males typically spawn for as many as 30 days and females about seven - and what they are doing in these areas.

In all areas in between the two points, Ng said they would measure the pH level, salinity level, water flow and temperature of the river.

At the same time, they will collect egg and larvae samples. Researchers also will count the number of eggs and larvae and inspect for relevant damage.

Areas where there are an abundance of eggs and larvae will be considered advantageous to striper spawning. Areas where there are not as many eggs or larvae will be considered poor.

Researcher will then attempt to determine why.

"We are not saying that they don't spawn there. We are saying that there is reason to believe they are not successful," Grothues said.

Regardless of the research, fishermen continue to find success in the area.
 

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Read it this morning, very interesting. What a treat for anglers of this area to have such groundbreaking research right here in our own backyard!! Only 7 days, STRIKES.
 

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Dr.Bass backyard hell he is a barner. fishdoc is his screen name and he is the guy Capt Phil and myself are working with on our barner fish. :cool:
 

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No ,7 days is how long the cows stick around, it's in the article. I am here until August, Jack. This is your your year, and Mack's is the best for sure.

Stain, that's awesome, did not know that. Should have known, Billy D did say good things about you. It's a shame we are losing him too, although now you have afreind in the Carolinas.
 
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