Quantifying contamination of streams by 1080 baits, and their fate in water

Forty-eight streams were surveyed during four aerial 1080 operations in New Zealand's South Island to quantify the number of 1080 baits falling into streams. Bait size used in each operation varied considerably: small (2g) baits in Marlborough, medium-sized (6-7 g) baits in Canterbury and the West Coast, and large (11 g) baits in Lewis Pass. The number of baits found in streams varied widely, and was related only to bait size, with more of the small baits found in streams than the large baits. There was no relationship between stream width or canopy cover and the number of baits found within a stream. These findings suggest that the potential number of baits falling into a stream cannot be calculated from the bait application rate and the stream size. The fate of submerged 1080 baits was also examined in a laboratory flow tank. Submerged baits fragmented within 3-4 days. 1080 was rapidly leached from submerged baits: almost 50% of original 1080 had leached after 5h, and >90% after 24h. Such rapid leaching reflects 1080's high solubility. This finding has implications for water quality monitoring programmes used during 1080 drops, as samples should be collected within 4-8h of potential contamination to detect presence of 1080.