Seabird bycatch reduction in New Zealand's inshore surface longline fishery.
Significant seabird bycatch issues were first identified in longline fisheries (e.g., Brothers 1991), and international management responses were initially focused on addressing this fishing method, ahead of others (FAO 1999). However, despite prolonged management and considerable scientific efforts, surface longlines still catch and kill significant numbers of seabirds annually, and worldwide (Anderson 2011). In New Zealand, surface longline fisheries are a source of bycatch risk for seabird species including Antipodean and Gibson’s albatross (Diomedea antipodensis antipodensis, D. a. gibsoni), Campbell albatross (Thalassarche impavida), Salvin’s albatross (Thalassarche salvini), southern Buller’s albatross (Thalassarche bulleri bulleri), white-capped albatross (Thalassarche steadi), black petrel (Procellaria parkinsoni), Westland petrel (Procellaria westlandica), and white-chinned petrel (Procellaria aequinoctialis) (Abraham and Thompson 2011). It is highly likely that some of these species are caught in commercial fisheries in New Zealand waters at levels exceeding their sustainability limits (Richard and Abraham 2013), as well as being caught internationally (e.g., Baker et al. 2007).
Characteristics of surface longline gear that exacerbate the risk of seabird bycatch include relatively slow-sinking hooks, which remain within reach of seabirds for significant periods, the use of baits attractive to birds, long snoods, and the very long lengths of lines that are deployed with hooks attached (Bull 2007). Mitigation measures for this fishing method aim to reduce the availability of hooks to seabirds. Measures recognised as current global best practice for achieving this are line-weighting (which increases hook sink rates), deploying tori lines (which restricts bird access to hooks and lines during setting) and setting at night (when some species of seabirds, especially albatrosses, are less active) (ACAP 2011). The implementation of these measures is required in specified forms and combinations in New Zealand surface longline fisheries (New Zealand Government 2008).
Despite the existence of a number of measures to reduce bycatch in surface longline fisheries, continued captures in these fisheries demonstrate that the available measures do not preclude the existence of significant bycatch risk (Richard et al. 2013). This may be due to a variety of reasons e.g., inconsistent (or lack of) implementation, incompatibility with gear configurations, implementation of insufficient measures (e.g., night-setting without line-weighting). In particular, safety concerns with line weighting appear to dissuade fishers from utilising this bycatch reduction method (e.g., Maritime New Zealand 1996, 2003). Globally, research is ongoing into new measures aiming to reduce seabird bycatch in surface longline fisheries, including safe leads (Sullivan et al. 2012), hook pods1 (Sullivan 2011), an underwater line-setter (Robertson and Domingo 2011), and double-weighted branchlines (WWF 2011). Improved safety is a key component in the development of some of these methods. Following promising results from trials of such innovative devices, the Overall Objective of this project is to test one or more mitigation methods which reduce the availability of surface longline hooks to seabirds at line setting. This objective encompasses two specific objectives:
Specific Objective 1. To test the safe use and mitigation effectiveness of one or more mitigation methods, not currently in common use in New Zealand surface longline fisheries that reduce the availability of surface longline hooks to seabirds at line setting.
Specific Objective 2. To assess and quantify any impacts on catch rates between target and bycatch species between snoods with and without the target mitigation method.
Here, we report progress towards achieving these objectives in the first year of this project.