Balancing Sampling Precision and Fisheries Management Objectives: Minimal Methods

Density-dependent and environmental effects on population size are both too weak to be useful for short term fishery management (Smith, 1985). Year-to-year variation of recruitment rate may be of the same order of magnitude as measurement uncertainty and population changes may have to be sustained for 2 to 3 years to be detectable using the precision available from current techniques. As fishing rates accelerate, the dependence of the fishable biomass on recruitment is increased. Pre-recruit survival and growth may be more episodic than adult survival and fecundity (Smith and Moser, 1988). The episodic nature of recruitment combined with higher fishing rates may make more frequent biomass estimates necessary. When variable recruitment and high total instantaneous mortality rates (ITMR) reach a certain level, effective fisheries management will require development of recruitment prediction procedures in addition to virtual population and biomass monitoring. Annual biomass surveys may be redundant because many stocks contain several year classes. The costs of implementing recruitment prediction and systems to monitor biomass may be a significant fraction of the value of the added catch and this should be considered during management planning.