Linda Benedict, Gautreaux, Craig
Louisiana has long been known as a Sportsman’s Paradise. Its many bayous, swamps and coastal marshes provide excellent fishing and wildlife viewing opportunities. Upland and bottomland forests afford hunters of all ages the chance to harvest small-game animals such as squirrels and rabbits and allow big-game hunters the prospect of taking a trophy deer or turkey.
To continue these recreational and commercial opportunities, management decisions must be made regarding the harvest of recreational and commercial species and maintaining and preserving the habitat necessary to support these animals. These important decisions involve research from the Louisiana Agricultural Experiment Station through the School of Renewable Natural Resources.
Wildlife research enjoyed an increased emphasis led by Robert Chabrek, a wetlands ecologist in the department in the 1970s through the 1990s. His research focused on the coastal plains environment and the interaction between both plants and animals. The vegetative maps developed by Chabrek and his survey methodology techniques laid the groundwork for future studies.
Bill Herke, a fisheries researcher, studied fish passage through human-made water control structures such as weirs and locks in the 1960s and 1970s. His work was the basis for federal policy in the Gulf of Mexico region and aspects of his work remain in effect today.
Recently, Frank Rohwer’s work on predator control as it relates to successful waterfowl breeding demonstrated that predator control must be conducted on large areas of land to contribute to more successful breeding. Rohwer is an avian researcher in the department.
Importance of Water
Michael Kaller, a researcher specializing in fish and stream ecology, is looking at ways to best preserve Louisiana’s water resource. “We are at the bottom of the hill. We need to make informed decisions about how much we need to support our ecosystems and our economic activities as well as what we could part with if the economic opportunity was there,” Kaller said. He cited the discussions of the sale of Toledo Bend water as a prime example of how water resource management will be a major issue in the future.
At nearly 600,000 acres, the Atchafalaya Basin is the nation’s largest bottomland swamp. Because of its abundance of natural resources including fish, wildlife and oil and gas, it is a center of commercial and recreational activity for the state. The interaction of humans within the system has led to some problems.
One problem is dealing with the flow of water through the basin. Many human-made canals and levees have disrupted the natural north-south water flow. When the spring floods come, water overtops these levees but is trapped behind them. Eventually, this water becomes devoid of oxygen, but it is reintroduced to the system when water levels drop, pulling the water into the system, thereby reducing water quality throughout the basin.
“The idea is to breach or notch levees that inhibit the natural north to south water flow. We want to notch the levees so that the water comes out,” Kaller said. The notching of the levees has been occurring for nearly 10 years, and AgCenter scientists have been studying the effects. Kaller cites the Grand Lake area as a prime example where a more natural north-south flow contributes to better water quality than areas like the Bayou Sorrel area that has many eastwest running canals.
A major benefit from improved water quality is enhanced recreational and commercial fishing. While water quality is an essential element for a healthy fishery, LSU AgCenter researchers are looking for other ways to improve recreational fishing. One area that has garnered their attention is the state’s largemouth bass population.
Bass fishing in Louisiana is a multi-million dollar industry. To help increase the number of trophy fish in the state’s waters, the Louisiana Department of Wildlife and Fisheries began to introduce a Florida-strain largemouth bass in the 1980s. These fish were introduced to improve the genetics of native bass.
“A lot of the information we have been getting is being used by Wildlife and Fisheries to modify their stocking practices and to assess the effectiveness of their stocking program,” said William Kelso, associate director of the school.
The introduction of Florida-strain fish has had an impact on the record book. According the Louisiana Outdoor Writers Association, the top 10 record bass caught in Louisiana have occurred after the introduction of Florida-strain fish. It now takes a bass more than 15.15 pounds to make the top 10. “We just got some data from taxidermists from across the state on 91 trophy fish, and 90 of them had Florida genes in them,” Kelso said.
Kelso also said that having good brood stock is an essential component of the program. AgCenter scientists play a key role in ensuring that the brood stock is comprised of the Florida-strain by performing genetic testing at the state’s Booker T. Fowler Hatchery in Woodworth
A recent phenomenon that may have a major influence on the future of hydrologic ecosystems relates to invasive species such as giant salvinia, Asian carp and feral hogs.
Salvinia, an invasive aquatic weed from South America, has the ability to overtake water bodies and other native aquatic vegetation, turning these water bodies into a liquid desert. A ripple effect would make these places unsuitable for migrating waterfowl. Kaller said the AgCenter has experts in many disciplines, and they are capable of tackling complex issues from many different approaches. For salvinia, researchers are looking at solutions from multiple approaches including chemical and biological control.
A biological control involves the use of weevils native to South America. Dearl Sanders, a weed scientist, and Seth Johnson, an entomologist, have been involved with releasing nearly 3 million weevils in more than 40 locations statewide. Establishing a colony has proved challenging.
“Along the coast, the weevils have been effective at controlling the salvinia because they make it through the winter. In north Louisiana, it is a different story. The prior two winters have been fairly severe, and the weevils have not made it through the winter. So the approach up there has been currently to make weevil releases with the strain that we have now and hope that we have a couple of mild winters,” Sanders said.
According to Sanders, a biological control is much more cost effective than a chemical control. He is running the entire state weevil program on a $100,000 budget while it would cost nearly $9 million to control the salvinia just on Lake Bisteneau, a 14,000 acre impoundment in north Louisiana.
Places where weevil populations have become established have seen declines in the area covered by the plant. “We have reduced the population of the giant salvinia better than 99 percent. So it looks like it does in southern Brazil. You have just a few salvinia plants and just a few weevils,” Sanders said.
Asian carp consist of two species, the bighead and silver. Originally imported to the United States for use in wastewater treatment lagoons in the 1970s, Asian carp escaped and are found in 23 states, primarily in the Missouri and Mississippi river watersheds.
Asian carp can reach high population density numbers and crowd out native fish populations. They are also a safety hazard because silver carp have a tendency to jump when startled leading to either injury to unsuspecting boaters or property damage.
Eradication of carp is not practical because of their widespread establishment. AgCenter researchers indicate that commercial fishing along with implementing management strategies to control their populations appears to be the most feasible approach.
Feral hogs have been in Louisiana for decades, but their environmental impact has escalated. Their increasing numbers harm crops, wildlife and livestock. Hogs have damaged rice, grain sorghum and sweet potatoes. They have destroyed shrub nesting bird nests and consumed young turkeys and deer fawns.
Feral hogs also carry several diseases that are threats to both humans and livestock. Some of the diseases include brucellosis, trichinosis and E. coli-related illnesses. Most human infections attributed to feral hogs happen during the cleaning of the animals. Wildlife and livestock infections happen when these animals venture into areas in which hogs have been feeding or watering.
AgCenter scientists have determined that feral hogs can contribute negatively to water quality. Researchers have found that hogs introduce harmful bacteria and reduce beneficial aquatic insects and mussels in upland streams. The damage to upland streams means impaired water is being carried downstream into coastal ecosystems, which are already suffering from saltwater intrusion and nutrient deficiencies.
Louisiana has a well-earned reputation as being a duck hunter’s paradise. But what happens in the northern plains of the United States and Canada has a direct correlation to the success of hunters in this state.
Nesting success plays a crucial role in the number of ducks that fly south and overwinter in Louisiana. Rohwer began to examine the role predators play in nesting success in North Dakota and three Canadian provinces.
While habitat plays an important part in nesting success, it is one piece of a larger equation. “It’s not always just about habitat, you have to manage the community,” Rohwer said. And this community includes foxes, skunks and raccoons.
“You are looking for an average between 15-20 percent nesting successes as the break-even point. Above 20 percent and you are producing ducks, and the population is going to grow,” Rohwer said. He also said that while weather such as drought plays a factor, predation plays a much larger role in nesting failures.
Rohwer said foxes are the greatest contributors to nesting failures. Foxes are adept at catching hens on the nest or raiding a nest for its eggs. He said that much like squirrels, foxes will cache the eggs for times when food is scarce.
Rohwer developed a predator control study over a large-scale area as opposed to controlling them on smaller areas. The study area was 16 square miles. In the study, 160 foxes and nearly 100 skunks and raccoons were trapped. Nesting success rate was nearly 45 percent compared to a rate of approximately 5 percent on an area that was not trapped.
While intensive predator management has shown positive results related to nesting success, another project Rohwer would like to attempt involves brood survival. Rohwer said there is little research on duckling survival with some estimates being that nearly half of the ducklings that hatch die before they reach flight stage. “It’s a different group of predators. Mink are tough on ducklings along with avian predators,” Rohwer said.
Researchers are continuing to look for ways to improve wildlife and the environment. The recent BP oil spill has scientists within the school looking for less toxic dispersants that will be available for future spills. Louisiana’s ongoing battle with coastal erosion has researchers looking at the impact of vegetative strips or terracing on the coastal environment.
Keeping Louisiana a Sportsman’s Paradise requires diligent research not only in Louisiana but in areas across the continent. Scientists within the School of Renewable Natural Resources are making sure that the opportunity to work and play in Louisiana’s outdoor environment continues to contribute to its rich heritage.
Craig Gautreaux, LSU AgCenter Communications Specialist, , Baton Rouge, La.
(A shorter version of this article appeared in the spring 2012 issue of Louisiana Agriculture.)