Multi-Species Fisheries Management

Aim:

The aim of this project was to develop species-specific standardized Catch Per Unit Effort (CPUE) values for the top 12 non-target species by volume landed in the South African hake inshore trawl sector, using a per-trip analysis. The focus was on identifying annual, seasonal, geographical, and vessel-based variations in catch composition to better understand the factors affecting bycatch. Additionally, the project tested various bycatch management schemes through modelling, using the data and insights derived from these analyses to improve bycatch management strategies within the fishery.

Results:

The project developed standardized Catch Per Unit Effort (CPUE) time series for eight non-target species, providing new abundance data for South African inshore trawl grounds, which can be used in stock assessments. Factors influencing catch composition, including year, area, vessel, and season, explained 95% of the variation, with year and area being the most influential. Vessel variation suggests that skipper behaviour could be targeted to regulate catch composition, though the issue of dumping unwanted catches requires further investigation. Geographical differences in catch composition indicate that area-based management could be an effective strategy. Testing of three effort-regulation strategies showed that while some yielded good catches, they posed risks to less productive species, highlighting the need for alternative management approaches, particularly area management.

Project Implementer

Collin Attwood - UCT