Paradigm of pragmatism: managing uncertainty in Australia's small pelagic fisheries
Biomass estimates of small pelagic fishes are highly uncertain; estimates of statistical precision only capture a portion of total uncertainty. Although the Daily Egg Production Method provides imprecise estimates of spawning biomass, it has been used to underpin the successful development of Australia’s largest fishery, the South Australian Sardine Fishery (SASF). The DEPM has also been adopted as the primary assessment tool in the Commonwealth Small Pelagic Fishery (SPF), and its potential application is being trialled in several other Australian fisheries. The DEPM has been adopted in these fisheries because stock assessments based on fishery-dependent data have not provided reliable estimates of biomass or recruitment (due to data limitations and/or violation of model assumptions). Ecological and logistical factors have also impeded the application of other fishery-independent methods, such as acoustic surveys. This presentation documents how the inherent imprecision of the DEPM has been addressed in the SASF. Two elements of the adaptive approach that has been used to assess and manage the fishery have been critical to its success. Firstly, we have used statistical methods that minimise imprecision and provide conservative estimates of spawning biomass. Secondly, the harvest strategies (control rules) that have been established are conservative and designed to address the imprecision of the DEPM. This presentation discusses potential opportunities for 1) further increasing the precision of estimates of spawning biomass (e.g. through improved sampling methods) and 2) using other (more reliable?) products from DEPM surveys, such as spawning area, as the key performance indicator in future Harvest Strategies.