Exotic Species Control: Louisiana Coastwide Nutria Control Program—Nutria Harvest Areas by Marsh Type, 2003–2004 Season

Nutria, large semiaquatic rodents native to South America, are literally eating their way through the coastal wetlands of Louisiana. Nutria weigh an average of 12 pounds and can consume 25 percent of their weight in aquatic plants daily. Current estimates report approximately 63,000 acres of Louisiana's fragile coastal wetlands are impacted by nutria's herbivorous habits at any time. The Louisiana Department of Wildlife and Fisheries (LDWF), with funding from the Coastal Wetlands Planning, Protection, and Restoration Act, is implementing the Louisiana Coastwide Nutria Control Program to reduce wetland damage by providing an incentive payment to registered trappers and hunters for each animal harvested.

GIS has an integral role in the collection, documentation, and analysis of hunting activity and nutria damage assessments. During the last few years, LDWF has documented and mapped nutria damage areas along the coast through aerial surveys of established transects. LDWF primarily needs to identify nutria harvest locations and determine if these areas are in or adjacent to documented damage areas. To address this need and many other reporting and mapping requirements, a SQL Server 2000 database was developed to maintain all participant and landowner information. An ArcSDE^® 8.3 geodatabase maintains the spatial data, and ArcInfo 8.3 is used for all mapping activities. A Microsoft Access front end was developed for easy field data entry.

In April and May 2004, a coastwide aerial survey was conducted of the nutria habitat. One hundred fifty-five transects spaced 1.8 miles apart were surveyed for damage, and 93 damage sites were visited. Twelve were new sites in 2004 and 81 were previously classified as damaged in a 2003 survey. When vegetative damage was identified, the location was recorded with differential GPS, and polygons were created. Additional information recorded included nutria abundance, extent of damage, dominant plant species, age and condition of damage, number of nutria observed, and a prediction of vegetative recovery. Types of analyses include nutria harvest by marsh type, identification of damaged areas not being harvested, number of nutria harvested from documented damaged areas, and nutria harvest per acre by lease.

Results from the 2004 aerial survey are encouraging. Compared to the 2003 survey, the total number of damaged acres decreased by 22.8 percent, and the severe damage decreased by 82.5 percent.

Currently in its third season, the program improves every year. Since migrating to ArcSDE geodatabases and SQL Server, map and report production has become more efficient. The success of the GIS application has allowed managers to track harvest activity at a greater level of detail than initially required and derive answers in a timely and efficient manner.