Lethal Control of Piscivorous Birds at Aquaculture Facilities in the Northeast United States: Effects on Populations

—Predation by piscivorous birds is considered a substantial threat to the aquaculture industry. However, lethal control of birds at aquaculture facilities has raised concerns about the effects on the distribution and abundance of populations of the species killed. We examined the relationship between numbers of piscivorous birds reported killed under U.S. Fish and Wildlife Service (USFWS) permits at aquaculture facilities in New York, New Jersey, and Pennsylvania and species population trends within the respective states. The USFWS issued 26 permits to 9 facilities from 1985 through September 1997. Eight species appeared on permits, but only six species were reported killed: blackcrowned night-herons Nycticorax nycticorax, doublecrested cormorants Phalacrocorax auritus, great blue herons Ardea herodias, herring gulls Larus argentatus, ring-billed gulls L. delawarensis, and mallards Anas platyrhynchos. Over 13 years, the authorized number of birds to be killed per species or group (e.g., gulls) ranged from 5 to 800 (mean 5 240, SD 5 300), whereas the reported number of birds killed per species or group (198521996) ranged from 0 to 289 (mean 5 83, SD 5 118). Across states and species, the number of birds authorized to be killed per permit ranged from 2 to 60 (mean 5 27, SD 5 20), whereas reported kills ranged from 0 to 45 (mean 5 12, SD 5 10). Herring gulls (N 5 272) and great blue herons (N 5 163) were the most frequently killed species. The number of birds reported killed, relative to systematic long-term population trends, is considered to have had negligible effects on the population status of the respective species.