Cost benefit of fishery-independent surveys: are they worth the money?

Fishery-independent monitoring is invariably more costly than fishery-dependent monitoring but is justified on the basis of the value of the data for effective management, or is viewed as the only valid approach for setting Total Allowable Catches (TAC). However, the cost-benefit of fishery-independent monitoring is rarely explicitly assessed. Development of an integrated fishery model for the Torres Strait tropical rock lobster (TRL) Panulirus ornatus fishery provided the opportunity to assess the relative value of different combinations of fishery survey methods. Annual fishery-independent pre-season and mid-season surveys were compared with fishery-dependent data collection. All three methods are currently carried out or have been in place in the recent past. Typically, short-lived highly variable species such as TRL require both recruit and spawner biomass surveys. Using CPUE data only, and not carrying out either the pre-or mid season fishery independent surveys, resulted in lower and considerably less precise TAC estimates. When conducting both fishery-independent surveys a positive cost benefit ratio was realised if additional catch to the CPUE-based TAC estimate was greater than 14.8 t (around 2% of TAC). TAC estimates based on independent fishery surveys were up to 20% greater than the model-predicted estimates using CPUE data alone. Including both independent fishery surveys returned a positive net present value over a 20 year timeframe even when randomly varying biomass, accounting for increasing survey costs, lower gross margins, and lower lobster prices.