The number of Campbell Island shags is assumed to be stable (4), and they are not believed to be currently subject to any major threats (2). However, because it breeds on only one small island it is very vulnerable to any future threats or chance events. In the past, it is thought the shag may have been impacted by farming activities on the island. Sheep farming was abandoned in 1931 and the last remaining sheep were eradicated from the island in 1992 (6), but a number of introduced plant species from the days of agriculture remain.
Surveys suggest that introduced feral cats may have died out on the island, and the brown rat and Norweigan rat have also recently been eradicated from Campbell Island. Whilst the Norwegian rat was known to have decimated wildlife on the island, none of these introduced mammals are known to have had any impact on the shag (2) (4). It is a native bird, the brown skua, which is certainly known to affect the Campbell Island shag, through predation on the eggs (2).
As shags spend the majority of their time at sea, they are very vulnerable to water pollution, particularly oil spills, and impacts from the fishing industry. Fisheries can affect the shag in two ways; over-harvesting of one species may alter marine ecology, possibly affecting the availability of food for the shag, or shags can become entangled in fishing nets. Abandoned nets pose a particular threat (5). An increase in the tourism industry in the region, if not properly managed, could pose a threat to the Campbell Island shag, through further accidental introductions (6), not all of which could be as harmless as those in the past.