Wading bird depredations on channel catfish Ictalurus punctatus in northwest Mississippi

We interviewed farm managers about their perceptions of wading bird problem s and conducted preliminary surveys of wading bird populations at 67 random ly selected channel catfish Ictalurus punctatus pond complexes in northwest Mississippi during December 1995. At a subsample of 24 complexes and 10 ot her complexes previously surveyed in 1990, we surveyed wading bird populati ons bimonthly throughout the year in 1996 and observed great blue herons Ar dea herodias and great egrets Arden alba feeding at catfish ponds. Seventy- five percent of farm managers questioned felt that wading birds were causin g losses to their fish stocks, and 74% believed the problem was increasing. Consistent with interview results, 88% of the pond complexes surveyed had one or more wading birds present. Despite reported harassment programs by p roducers, great blue heron densities at 10 complexes previously surveyed in 1990 had increased by more than eightfold in 1996. Great blue heron densit ies varied with location, season and time of day, but the average 127-ha fa rm supported about 78 herons and 56 great egrets. Despite similar populatio ns, the potential impact of these two species was quite different. Live cat fish, averaging 10.3 cm in length (circa 10 g) comprised only 88 of the egr et diet by weight, and most of the fish were obtained from fingerling ponds during periods when these fingerlings may be weakened by the bacterial dis ease, enteric septicemia of catfish. In contrast, live catfish, averaging 1 6 cm in length (circa 34 g), comprised 44% of the great blue heron diet by weight. Herons foraged from both fingerling and food fish ponds. primarily in the early morning and evening. Based on average population densities and foraging rates, herons at the average 127-ha farm in northwest Mississippi consumed 114,000 (circa 3,900 kg) catfish, annually. However, further stud ies are recommended to document production losses.