Date of this Version
Proceedings of the 15th Wildlife Damage Management Conference. (J. B. Armstrong, G. R. Gallagher, Eds). 2013.
Conflicts with wildlife are often based on the perceptions and concerns of citizens, industries, and managers. The gregarious nature of Double-crested Cormorants (Phalacrocorax auritus; DCCO) makes their colonies highly conspicuous. Their feeding habits on forage and commercially important fishes have incited a human/wildlife conflict with this species. Colonies re-use roosting and nesting sites. In these areas guano deposits accumulate and are released into the environment where they have the potential to alter the food web through changes in productivity. This alteration can ultimately change the composition, abundance, and condition of fishery resources.
We investigate the influence of bird-derived nutrients in a semi-controlled pond system. We used a combination of Seabird Guano® and Triple Super Phosphate ® to simulate nutrient excretions of P. auritus at densities of 40,000 birds water acre-1. Our experiment was conducted in 3 phases. Phase 1 simulated a low-impact treatment where nutrients were added once every three weeks. Samples of planktonic organisms were collected 12-48 hours before and after fertilization. Phase 2 was the high-impact treatment where fertilizer was added twice per week, and planktonic organisms were sampled weekly. Phase 3 was a recovery period where no additional nutrients were added to the system and samples were collected every 10 days. Six replicate collections occurred for each phase, and each set was comprised of six samples. Control ponds received no fertilizer and every effort was made to minimize cross-contamination of equipment and safety gear between fertilized and unfertilized ponds.