Significance of Chlorinated Hydrocarbon Residues to Breeding Pelicans and Cormorants

necessarily mean that residues will not be detected.The industrial pollutants include the polychlorinated biphenyls (PCB's) which, like the insecticides, are now widely distributed in wildlife (Jensen 1966, Widmark 1967, Holmes et al. 1967, Risebrough et al. 1968b, Koeman et al. 1969). Sampling and PoolingFish were sampled by angling, gill-netting, and by picking up regurgitated meals, To minimize the effects of digestion, only whole regurgitated fish were taken.We pooled 329 of these fish for chemical analysis by segregating fish of approximately the same age and weights from each area.Fish up to 5 Ib were occasionally seen as pelican meals, although both pelicans and cormorants left materials at their colonies that were composed of minnows and fish up to 1 or 2 lb.We observed no other cold-blooded vertebrates or invertebrates in the regurgitated boluses at the colonies at the time of sampling.Where differences in fish size were encountered, we used equal volumes of ground material to give each fish equal representation in the pool.The fish were Anderson, Daniel W. et al. 1969."Significance of Chlorinated Hydrocarbon Residues to Breeding Pelicans and Cormorants."The Canadian field-naturalist