Historically, total allowable catches (TAC) of respective zones in the pearl oyster fishery have been changed in response to significant fluctuations in the previous year’s catch rate (catch per unit effort). These changes, however, have been influenced by factors other than variations in stock abundance, e.g. as changes in available technology or variations in fishing efficiency due to weather conditions or water clarity.
In order to make more reliable projections on future catch and effort there is a need to move away from reliance on retrospective catch data. In order to do this, information supplied to decision makers should include: 1) the size structure (length frequency) of past catches; 2) information on the abundance of pre-recruits (piggyback spat); 3) information on important environmental variables affecting stocks; and 4) other factors affecting catch rate such as water clarity and the use of new technology (e.g. GPS).
A recommendation from Project No. 95/41 states:
"The relationship between "piggyback" spat settlement, environmental effects and recruitment to the fishery which can be used to forecast increases/decreases in abundance should be developed. This enables changes to quota to be forecast to allow forward planning in pearl seeding and farm operations."
A framework for the collection of this data is needed, as pearl oyster fisheries have large fluctuations in recruitment over time, and management needs to base quota decisions on the presence or absence of emerging year classes. Collection of this data will give a more stable signal on the "health" of the fishery and allow more confident predictive assessments to be made.