Quantifying seabird bycatch: where do we go from here?

摘要: Bycatch of seabirds in offshore commercial fisheries has long been recognized as a serious conservation issue (e.g. Brothers, 1991; Cooper & Lokkeborg, 1999), but until recently the problem was principally associated with industrial longline gear. In fact, pelagic seabird bycatch is very much multi-gear problem. Watkins, Petersen Ryan (2008) have presented latest string recent case studies documenting geographically widespread and sometimes severe levels trawl throughout Southern Hemisphere (Weimerskirch, Capdeville Duhamel, 2000; Sullivan, Reid Bugoni, 2006a; Baker et al., 2007; Gonzales-Zevallos, Yorio Caille, 2007). Substantial occurs fleets Northern well Alaskan for groundfishes; NMFS, 2006). The one global importance that requires urgent international attention. National management bodies face several challenges they move forward to address within context. One fundamental question what relative cumulative threat populations from gear? Answering this depends on having reasonable estimates mortality these two gear types across multitude fishing which particular interact This will require new observer programs be established national their waters, currently working quantify high-seas (see Gilman Moth-Poulsen, 2007) expand threats posed by well. Trawl poses particularly difficult challenge estimation because large often unquantified proportion birds killed interactions cables (the dominant cause gears) not hauled onto vessel therefore goes unobserved traditional observer-data collection protocols Gonzales-Zevallos Yorio, 2006; Sullivan 2006a). Watkins al. observed only out 30 known fatalities cable interaction were eventually aboard, corresponding at best an overall 0.067 ( 0.046 binomial SE) detection rate type if haul data had used estimated bycatch. indicates need update monitoring fisheries, ensure proper accounting bird mortalities resulting collisions. Alternative methods should also explored, appropriate seabird–trawl are labor intensive expensive. able observe 0.5% annual effort reason, even some most well-funded fishery world United States) too overstretched financially meet coverage goals (Rossman, promising approach video (McElderry 2004; Ames, Williams Fitzgerald, 2005), apparent success during first part study. Another strategy may augment protocols, based sampling hauled-in bycatch, over term shorter aimed estimating species composition non-detection rates retrieved hauling These might then applied correction factors statistically estimate actual trawls collected using conventional protocols. To our knowledge, provide empirical inference about we encourage future report similar estimates. As research respond increase data, it would helpful adopt common metrics reporting reported per hour,