Scope of Cormorant Damage to Mississippi Catfish 

 Production — The U.S. catfish industry is valued 

 at more than $650 million, with nearly 65 percent 

 of catfish production originating from Mississippi. 

 Biologists at NWRC's Mississippi field station 

 completed a study that evaluates the distribution 

 and numbers of DCCOs on catfish aquaculture 

 facilities, tying together almost a decade of research 

 on cormorant food habits, bioenergetics, and 

 abundance data. 



A significant finding is that most depredation occurs 

 on food-fish production ponds, where economic 

 losses are high. Study results demonstrate that 

 cormorants used these ponds extensively during 

 January through April, with the greatest economic 

 damage occurring in February and March. During 

 the years of this study (winter 2000-01 and 

 2003-04), an estimated 1,775 and 1,347 metric 

 tons of catfish were consumed by cormorants in 

 the delta region of Mississippi. This depredation 

 translated into a loss to the industry of $10.3 million 

 to $13.2 million annually. 



Future studies will aim to develop efficient 

 methods for monitoring cormorant abundance and 

 distribution for purposes of damage estimation and 

 cormorant management. 



Development of New Aging Techniques for 

 Birds — With collaborators at West Virginia 

 University, NWRC scientists have found pentosidine 

 concentrations in the skin of DCCOs to be a linear 

 predictor of age. This information may lead to a 

 rapid, more cost-effective technique for identifying 

 the age of cormorants and many other species 

 of birds. Pentosidine concentration analysis will 

 provide scientists a better understanding of the 

 demographics of cormorants that are impacting 

 catfish production in the Southeast. In addition, 

 NWRC scientists are developing aging techniques 

 for other bird species of concern, including monk 

 parakeets and black vultures. 



Cormorant Distribution and Abundance on Catfish 

 Ponds in the Delta Region of Mississippi — 



Biologists evaluated the efficiency of aerial and 

 ground surveys conducted twice monthly for 

 detecting changes in cormorant abundance on 

 aquaculture facilities. Results showed that the 

 sampling effort would need to be increased by 

 approximately 40 percent in order to meet the 

 desired level of detection (a 15-percent change 

 in population levels). Habitat modeling efforts 

 evaluated the factors that affect cormorant use of 

 catfish facilities. Results suggest that cormorants 

 are most likely to be present at food-fish ponds y. 

 fingerlingand broodfish ponds. Additionally, bird 

 use of catfish pond clusters was related to season of 

 the year, distance of ponds from cormorant roosts, 

 distance from roads, and the number of cormorants 

 in nearby roosts. 



Response of DCCOs to Management Activities on 

 the Breeding Grounds in the Les Cheneaux Islands 

 of Lake Huron, Michigan — Scientists from NWRC's 

 Mississippi field station collaborated with the WS 

 Operational Program in Michigan and the Michigan 

 Department of Natural Resources to use DCCO 

 management as a means of improving the local 

 yellow-perch fishery. Several studies addressed 

 different aspects of the damage attributed to 

 cormorants or the management approach for 

 dealing with the damage. 



Management efforts resulted in more than a 

 90-percent reduction in the number of young 

 cormorants produced annually and more than a 

 60-percent reduction in cormorant numbers overall. 

 Research results indicate that cormorants from 

 the colonies in question are feeding extensively in 

 the specific areas where perch populations have 

 declined, and that perch numbers following the first 

 3 years of management have improved. 



Developing Methods 7 



