Introduce catch shares
Overall effectiveness category Awaiting assessment
Number of studies: 2
Background information and definitions
Catch share is a fishery management system that allocates harvest rights to individuals or communities. The system has developed over the years, and it may now be described as falling into two main types: quota- and area-based catch shares. Quota-based systems set a species or fishery-wide catch limit (or in some cases fishing effort limit), a portion of which is assigned to individuals or groups for harvest. Participants are directly accountable for staying within the limits. Area-based systems allocate participants an exclusive privilege to harvest a specific area. Combinations of catch share systems may also be employed. This intervention covers any evidence of fisheries managed by catch shares where the type is not specified, and/or the measures are mixed. Introducing catch shares may limit fishing effort and mortality and help ensure sustainability by reducing effects of overfishing.
Evidence for related interventions is summarized under ‘Introduce an overall catch limit (quota cap or total allowable catch) by fishery or fleet’, ‘Set catch shares by area’ and Set catch shares by species‘.
Supporting evidence from individual studies
A systematic review in 2000–2004 of 11 marine regions worldwide (Melnychuk et al. 2012, same data sources as Melnychuk et al. 2016) found that fisheries that introduced catch shares (divisions of annual fleet-wide quotas among individuals or groups) did not have improved management performance based on biomass targets compared to fisheries managed only by fleet-wide quota caps or fishing effort controls (non-catch share fisheries) but did result in lower rates of over-exploitation than non-catch share fisheries. Across stocks (mainly fish but including some invertebrate fisheries), there were no differences in ratios of current stock biomass to target management biomass between catch share, fleet-wide quota caps and non-catch share fisheries (data reported as statistical results). In addition, there was no difference in the proportion of stocks subject to over-exploitation (measured as current exploitation rate - fishing mortality - relative to target exploitation rate) between stocks under catch shares, both full and partial (9–17%), and fleet-wide quota limits (13%). However, over‐exploitation was higher (41%) in stocks under effort controls (like days-at sea limits or size-based limits). Data for 2000–2004 were extracted from a fisheries stock assessment database (‘RAM Legacy’ - see original paper for details) and from other sources including stock assessment documents and fishery management plans. A global meta-analysis examining trends in biomass and exploitation rates was performed for 345 stocks of 158 species from 11 regions. See original paper for full details of assessment methods and metrics used.Study and other actions tested
A systematic review in 2000–2004 of seven marine regions worldwide (Melnychuk et al. 2016, same data sources as Melnychuk et al. 2012) found that fisheries managed under catch shares (individual catch quotas) typically met biomass sustainability targets and had rates of exploitation below or the same as target levels. Overall, 63% of stocks with catch shares had biomass levels above or within 10% of management sustainability targets. Fisheries that transferred excess catch or under-catch into the following year’s catch limit had higher ratios of stock biomass to target levels, while fisheries that did not had lower biomass ratios. In addition, 68% of stocks had exploitation rates below or within 10% of targets. Catch share systems in place >15 y had exploitation rates lower than target levels (data reported as statistical model results). Data for 2000–2004 were extracted from a fisheries stock assessment database (‘RAM Legacy’ - see original paper for details) and from other sources including stock assessment documents and fishery management plans. The study used meta-analysis to investigate the effects of catch shares (individual quota systems) on sustainability targets for biomass and rates of exploitation of 167 fish stocks in Canada, New Zealand, Australia, Iceland, Argentina, South Africa and USA.Study and other actions tested