Protected species bycatch in New Zealand fisheries

Seabirds, marine mammals, and turtles are caught during commercial fishing operations within the New Zealand Exclusive Economic Zone. In order to monitor the impacts of fishing on these species, New Zealand government observers on fishing vessels record any protected species bycatch incidents that occur. Observer data on protected species captures are maintained by the Ministry for Primary Industries, with identification of captured animals carried out by the Department of Conservation. The data have been summarised in a series of reports, with the most recent report covering the period from 2002–03 to the end of the 2008–09 fishing year (Abraham and Thompson 2011b). This dataset provides a summary of protected species bycatch in trawl and longline fisheries, from the 2002–03 to 2012–13 fishing year (fishing years run from October 1 to September 30). Observers are only present on some fishing vessels. To estimate total captures in a fishery, it is necessary to use statistical methods to extrapolate from the observed fishing to the unobserved fishing. The total observable captures are an estimate of the captures that would have been reported, had observers been present on all fishing vessels. There may be additional mortalities (such as birds that are struck by fishing gear but not brought on board the vessel) that are not recorded by observers. These are referred to as ‘cryptic mortalities’ and are not included in the estimates of total captures, nor is there any evaluation of potential survival of seabirds recorded as captured but subsequently released alive. The methods used for the estimation follow those described in technical reports on bycatch estimation for seabirds (Abraham and Thompson 2011a, Abraham et al. 2013), and marine mammals (Thompson et al. 2013). ####Notes about some Fields: - **fishing_year** the fishing year of the capture. Fishing years run from 1 October to 30 September; - **datetime** the date and time of the capture. All times are in New Zealand Standard Time (GMT+12); - **status** whether the animal was alive or dead; - **identification** how the identification was made (necropsy: by necropsy of the dead animal; photograph: from an expert inspection of a photograph of the capture; imputation: imputed by correcting the observer code using necropsy and photographic identifications of other captures with the same observer identification; as reported by the observer); - **method** the fishing method (surface longline; bottom longline; trawl; set net; or purse seine); - **target** the target species reported by the fisher; - **vessel_size** the length class of the vessel (a range in m).在新西兰专属经济区（New Zealand Exclusive Economic Zone）内的商业捕捞作业中，常有海鸟、海洋哺乳动物与海龟被兼捕（bycatch）。为监测捕捞活动对这些物种的影响，新西兰政府会在渔船上配备观察员，记录发生的受保护物种兼捕事件。新西兰初级产业部（Ministry for Primary Industries）负责保管受保护物种捕获量的观察员数据，而捕获动物的物种鉴定工作则由新西兰保护部（Department of Conservation）完成。相关数据已被整理为一系列报告，最新的报告覆盖了2002–03捕捞季至2008–09捕捞季结束时段（Abraham与Thompson 2011b）。本数据集汇总了2002–03至2012–13捕捞季（捕捞季为每年10月1日至次年9月30日）拖网与延绳钓渔业中的受保护物种兼捕情况。 仅部分渔船配备了观察员。为估算某一渔业的总捕获量，需采用统计方法将观测到的捕捞数据外推至未被观测的捕捞活动。总可观测捕获量指的是：若所有渔船均配备观察员时，本应被记录的捕获量估算值。此外还可能存在额外死亡情况（例如被渔具撞击但未被带上船的海鸟），此类情况未被观察员记录，被称为‘隐蔽死亡（cryptic mortalities）’，未被纳入总捕获量估算范围；同时，本数据集也未评估那些被记录捕获后被活体放归的海鸟的潜在存活情况。 本次估算所采用的方法，参考了海鸟兼捕估算技术报告（Abraham and Thompson 2011a, Abraham et al. 2013）以及海洋哺乳动物兼捕估算技术报告（Thompson et al. 2013）中的相关方法。 #### 部分字段说明： - **捕捞季（fishing_year）**：捕获事件发生的捕捞季。捕捞季为每年10月1日至9月30日； - **日期时间（datetime）**：捕获事件发生的日期与时间。所有时间均采用新西兰标准时间（GMT+12）； - **存活状态（status）**：捕获动物的存活状态（活体或死亡）； - **鉴定方式（identification）**：物种鉴定的实施方式（尸检：通过对死亡动物进行尸检；照片鉴定：由专家对捕获现场照片进行检视；推定修正：通过对其他具备相同观察员标识的捕获事件的尸检与照片鉴定结果，修正观察员标识后推定得到；观察员现场报告）； - **捕捞方式（method）**：捕捞作业方式（表层延绳钓、底层延绳钓、拖网、定置网、围网）； - **目标物种（target）**：渔民上报的捕捞目标物种； - **船体尺寸等级（vessel_size）**：渔船的长度分级（以米为单位的范围区间）。