Marine Environment

Potential impacts to the marine environment were extensively considered as part of the approval process for the project. All marine impacts by the LHI REP were deemed minimal with appropriate controls in place. A key control was that no bait were to be intentionally applied to the marine environment.

For successful eradication, all terrestrial habitats which may harbour rodents must receive bait, including smaller islands, ocean cliffs and islets. When brodifacoum pellets are applied aerially to these areas in attempts to eradicate rodents it is often the case that a small quantity of bait may enter the marine environment near the shore. Studies on other island eradications have shown that the small amounts of bait that enter the water disintegrate quickly, particularly in areas with high wave action.  The low-moderate application rate of brodifacoum (0.4 g/ ha) for the LHI REP, low solubility, high dilution factor in the marine environment and one off eradication mean that any sea water contamination would be of a sufficiently low magnitude as to not present a significant risk to marine life or humans through any activity (including swimming or snorkelling).

Bait entry into the lagoon was minimised by hand baiting along the lagoon foreshore, only baiting above the high water mark and the use of a deflector arm on the spreader bucket to minimise bait entry into the water. Bait entry into waters adjacent to small islands, ocean cliffs and islets was minimised by the use of a highly accurate trickle-baiting bucket. Results from the environmental monitoring sampling showed no detectable levels of brodifacoum in the marine waters of Lord Howe Island following aerial baiting.

Prior to implementation of the program, a study was undertaken by the University of Technology Sydney on LHI that showed that even where baits enter the water, it was unlikely that would fish consume the pellets. The study tested fish attraction to bait at many locations around the island and found that at all sites (except for the hand feeding site at Ned’s beach) no fish consumed pellets. Even at Ned’s a very small number of individual fish consumed a pellet.

Read the full study – Reef Fish behaviour towards placebo bait pellets on Lord Howe Island