MULTI-SCALE ABUNDANCE AND DISTRIBUTION TRENDS OF DOUBLE-CRESTED CORMORANTS Phalacrocorax auritus ON CATFISH AQUACULTURE IN MISSISSIPPI

Paul C. Burr*, Jimmy Avery, Garrett M. Street, Bronson K. Strickland, and Brian S. Dorr.
 
*Mississippi State University
Wildlife, Fisheries, and Aquaculture
Box 9690, Mississippi State, MS 39762
Pcb124@msstate.edu
 

Commercial production of catfish (Ictalurus spp.) is the largest aquaculture industry in the nation, with the majority of production occurring in Mississippi (MS). Since its inception in the 1960's, the state's catfish industry has unfortunately experienced continuous human-wildlife conflict between producers and fish-eating bird species through the consumption of cultured catfish. Most notable of these species is the Double-crested Cormorant (Phalacrocorax auritus; hereafter, cormorant), which can cost producers millions of dollars annually, through the depredation of catfish.

Historically, cormorants were infrequently found on fresh waters of MS, but populations of cormorants wintering inland steadily increased during the latter part of the 20th century. This resulted in a growing concern from catfish producers over the economic loss associated with bird depredation at their facilities. Consequently, a large scale monitoring program was implemented by U.S. Department of Agriculture, National Wildlife Research Center (USDA-NWRC) in 1996 to estimate both the abundance and distribution of cormorants in the state. This extensive data set permits exploration of the mechanism driving cormorant use of MS in relation to aquaculture.

Our data suggest the change in cormorant population wintering in MS coincided with the changes in catfish aquaculture in the state (Figure 1). Other aspects are also being examined, including effectiveness of roost harassment strategies on displacing cormorants away from aquaculture, seasonal trends of cormorant distribution, and fine scale roost characteristics that explain cormorant use. Seasonal trends involve examining where cormorants occur, with respect to aquaculture, between their arrival and departure from the state within a winter season. Their use of catfish ponds throughout this time may vary in relation to migration as their dietary needs change. Investigating fine scale roost characteristics will determine what cues cormorants use to choose roosting locations, aiding in effective future roost harassment. Although much research has been done in the past to address some of the above issues, drastic changes in catfish aquaculture in MS including total hectares in production, production practices, and the use of hybrid catfish make contemporary information on cormorant depredations particularly relevant.