Evaluation of fishery-dependent sampling strategies for monitoring a small-scale beach clam fishery

- Logbook, beach- and port-based data sources were compared.
- Catch, effort and CPUE did not differ between logbook and beach data.
- Beach-based size composition data appeared biased compared to port samples.
- Cost-effective fishery monitoring could be based on a combination of logbooks and port sampling.

This study examined industry logbooks, and beach- and port-based fishery-dependent data sources for monitoring and assessing catch, effort, catch-per-unit-of-effort (CPUE) and size compositions of beach clams in a small-scale fishery in eastern Australia. The study was conducted across the six-month fishing season and encompassed two management regions, serving as a model for elsewhere. In general, values of catch, effort and CPUE did not differ significantly between logbooks and beach sampling, and spatial and temporal trends in examined indices were similar across both data sources. Beach sampling captured additional data that included the partitioning of fishing effort into search and dig time, and also the number and location of sites fished each day, which could be useful in addressing uncertainty in CPUE-clam density relationships and potential fishing impacts, and assist in spatial management of fishing across beaches. These data could be future sourced from industry and provided on modified logbooks. Compared to port sampling, the beach-based size composition data appeared to be biased and influenced by fisher behaviour. Cost-effective future monitoring of the fishery could be conducted using a combination of logbooks for catch and effort that includes strategic periodic validations using beach-observers, and port sampling for size compositions. The success of such a strategy is reliant on strong fisher cooperation that requires open co-management arrangements. Future assessments of the beach clam resources need to account for inherent differences in populations across individual beaches, including non-fished (control) beaches.