Quantifying effects of reporting changes for pāua (Haliotis iris) catch-per-unit-effort

Pāua (Haliotis iris) fisheries in New Zealand are largely managed based on the outcome of regular stock assessments that determine the stock status of a particular quota management area (QMA). These stock assessments are largely dependent on catch-per-unit-effort (CPUE) from commercial fisheries as indices of relative abundance. The CPUE is also used to determine harvest control rules that support management procedures for pāua in an increasing number of QMAs. Although these management procedures are largely used internally by the fishing industry to manage catch levels between stock assessments, they are important tools to control removals.

Given the importance of CPUE for the assessment and management of pāua fisheries, the recent change from Pāua Catch Effort Landing Return (PCELR) forms to an electronic reporting system (ERS) via applications on handheld devices led to concerns about the continuity of CPUE data. The concerns were largely centred on two aspects of electronic reporting: spatial information and the duration of fishing effort (time). To address these concerns, the present study compared reporting patterns between PCELR forms and data reported via ERS over a comparable time period of three years of pre-and post-reporting change. To understand and omit records with poor effort reporting, a model was used to examine changes in reported effort time. This examination aimed to identify changes in client-effort reporting in relation to expected changes from inter-annual variation in PCELR data. To estimate spatial reporting fidelity, inferred statistical areas from catch records were compared with reported locations of catch bags recorded during dive fishing events. These analyses suggested that i) a limited number of clients changed their reporting, and ii) spatial reporting was accurate overall, although some clients tended to submit catch reports for areas other than areas where fishing had occurred.

Subsequent CPUE analyses, omitting different subsets of reported CPUE data, suggested that both spatial- and effort-derived subsets did not change CPUE trends for most areas that are currently monitored based on CPUE. Although changes in reported CPUE may have introduced changes in reporting for some clients, this finding highlights that inclusion or omission of these data has limited effects on estimated CPUE trends. For this reason, any effect on stock assessments and management procedures would be minimal. In contrast, other changes, such as selectivity changes from changes in targeting in most fisheries, will likely have a more substantial effect on CPUE.