Characterising deck strikes

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Summary

Incidents of bird strikes on fishing vessels in the Southern Ocean have long been known and attributed to the presence of artificial lights disorientating birds at night (Black, 2005). It has been reported that on some vessels bird strikes are a nightly occurrence on vessels in the Southern Ocean (Black, 2005). Mortality of seabirds caused by collisions with cruise ships has also been witnessed, for example Bocetti (2011) extrapolated the seabird mortality she had observed on a cruise ship to an estimation of 240 bird deaths caused by colliding with the vessel on a given night. Seabirds colliding with a vessel is referred to as a deck strike in this report. Deck strikes are another way in which seabirds can be effected by anthropogenic activities. This report solely considers deck strikes occurring on commercial fishing vessels within New Zealand’s EEZ.

A deck strike is defined as “being when an animal collides/impacts with the vessel or it’s superstructure and is unable to leave the vessel of its own accord (either through injury or disorientation). Seabirds which land on vessels and then fly away are not included in this category” (Department of Conservation, 2010). Due to the nature of deck strikes there are likely to be inconsistencies between the reporting of occurrences between observers. An example of this is when an observer has recorded the capture method as other, rather than deck strike and commented on the interaction ‘deck strike’.