Mitigating seabird net captures in trawl fisheries: CSP reports

Introduction

This is the final report for MIT2006/02: summarising the knowledge of seabird interactions with trawl nets, discussions to identify mitigation measures and reports on field trials undertaken to assess the effectiveness of agreed mitigation options. Published 2009.

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Summary

Interactions between seabirds and trawl nets in the New Zealand deepwater trawl fleet have been responsible for a significant proportion of recorded seabird captures. Interactions with trawl warps (cables) are responsible for the majority of the remainder.

In recent years, as a result of research on interactions between seabirds and trawl warps, mitigation measures have been implemented to reduce warp strikes both in New Zealand waters, and internationally. As a result the proportion of seabird captures through interactions with nets has risen. Generally it is the smaller seabird species that are captured (and retained) by nets, particularly shearwaters and petrels which are capable of diving well below the sea surface. Larger seabirds will tend to feed on discarded offal and fish waste in proximity to warps, but at times they are also at risk of injury or death due to feeding in proximity of nets at the surface.

DOC has recognised the above and contracted research to assess and analyse the interactions between seabirds and trawl nets and to identify and trial options to mitigate these.

This paper summarises the knowledge of seabird interactions with trawl nets in New Zealand waters, summarises subsequent discussions to identify mitigation measures and reports on specific field trials undertaken to assess the effectiveness of agreed mitigation options.