Pesticide and PCB levels in the eggs of shag Phalacrocorax aristotelis and cormorant P. carbo from Ireland

Shag and cormorant eggs were collected from three sites off the east, south-east and south coasts of Ireland and the pesticide and PCB levels determined by gas chromatography.

Of the pesticides, pp-DDT, pp-DDE, op-DDE, lindane, dieldrin, endrin, α-BHC, α-chlordane, oxychlordane, heptachlor, hept-epoxide and quintogen were detected, while op-DDT, op-DDD, aldrin, endosulphan-1, endosulphan-2, endosulphate, methoxychlor, β-BHC and γ-chlordane were not found. PCB levels were an order of magnitude greater than those of the pesticides, but levels of all substances were, in general, rather low, and it is concluded that organochlorine contamination is not at present a serious problem in the Irish marine environment.

There were few interspecific differences in concentrations of individual pesticides, and there was no significant difference in levels of total pesticides or total organochlorines.

In general, the highest levels were found at the site off the east coast, and there was a significant inter-site difference in total pesticides, while the difference in PCBs was very close to significance at P = 0·05.

The overall evidence suggested that these levels did not cause either lethal or sublethal (egg-shell thinning) effects.