Weight of evidence approach to stock classifications
Assessing the status of biological fish stocks can be a difficult task. The methods used to monitor and assess stock status vary, ranging from simple catch levels to complex stock assessments.
Smaller and lower value stocks and fisheries often have less data available or limited resources to undertake quantitative stock assessments. If targeted catch from a stock is very low, or a species is only taken in small numbers as byproduct, it may be inappropriate to invest in the development of resource-intensive quantitative stock assessment models.
It is important to note, however, that robust stock status assessments can be made without having quantitative stock assessments and/or scientific surveys.
A weight-of-evidence approach can be used to support a stock status classification. This is achieved by systematically considering a range of biological and fisheries information.
For many biological fish stocks, particularly for smaller fisheries, limited evidence is available. Expert judgement plays an important role in stock status classification, with an emphasis on documenting the key evidence and rationale for the decision.
Evidence used in a weight-of-evidence approach may include:
- fisheries-dependent data (i.e. empirical indicators derived from fisheries reporting such as catch, effort, catch rate, spatial and temporal distribution of the fishery)
- risk assessments
- fishery-independent data (i.e. systematic population surveys)
- quantitative stock assessment models
- harvest strategies.