Light mitigation: reducing vessel interactions with seabirds

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Summary

Artificial light produced by vessels operating at night has been shown to influence behaviour and cause negative impacts to seabirds. Of particular concern, birds may be attracted to fishing vessels by light and become disorientated and confused, leading to collisions with the vessel (vessel strikes) and subsequently injury or death.

This work describes two sets of trials examining bird responses to a series of different light treatments of varying colour and amount. Land-based trials at a fairy prion breeding colony used short duration treatment periods in three blocks per night over a two-hour period. At-sea trials in the Hauraki Gulf used the same lights and treatments, but with longer durations and two blocks per night.

Snapshot abundance and behaviour counts were made from video footage recorded using a thermal camera. For the colony-based data, generalised linear mixed-effects models were applied to the counts from treatment periods, taking into account the experimental design and the variation in bird numbers throughout the night. Behaviour counts showed greater differences between treatments than snapshot abundance counts. More light and whiter lights attracted significantly higher counts of birds than amber and red lights. Environmental variables incorporated in the model, including relative humidity, wind speed, wind direction, and moon phase and illumination described variation in both the snapshot or behaviour counts. Counts of birds were much lower at sea and appeared to be dominated by variation in the number of birds attending the vessel.
Results are consistent with those in the literature and support the recently introduced Mitigation Standards to reduce light-induced vessel strikes of seabirds with New Zealand commercial fishing vessels. Based on the findings in this study we make two recommendations for future work:

• The use of amber lights should be tested under fishing conditions to see if they are suitable for use on fishing vessels.
• Support vessels to implement the mitigation standards and minimise unnecessary use of light

Publication information

Goad, D., Middlemiss, K., Cieraad, E., Duke, K., Bell, H., Le Lec, Marc., Le Lec, Marissa., Fischer, J., Taylor, G. 2023. Light mitigation: reducing vessel interactions with seabirds. MIT2022-06 final report prepared for Conservation Services Programme, Department of Conservation. 16 p.