In the recent years, a benchmark in stock assessment is currently gaining popularity – SPR or Spawning Potential Ratio. Often just referred to as SPR, this method has been developed for data-poor fisheries, wherein few data (sometimes none) are available other than a representative sample of the size structure of the vulnerable portion of the population and an understanding of the life history of the species i.e. growth, maturity, fecundity, and natural mortality (Prince et al., 2015).
Spawning potential ratio is the average fecundity of a recruit in a fished stock divided by the average fecundity of a recruit in an unfished stock. It is based on the principle that certain populations of the fishery have to survive in order to reproduce and replenish the stock at a sustainable level (to allow growth and stability). It is a well-established biological reference point (Hordyck et al., 2014).
Whereas conventional statistical assessment models require numerous information i.e. catch demographics, spatial structures, ecosystem interactions, catch trends, etc., that are lacking in small-scale fisheries, SPR is one of the indicators that come handy in grass root assessments, thus providing immediate information on the status of the fishery to support urgent management decisions.
In blue swimming crabs (BSC), SPR can be derived by measuring the carapace width and determining the stage of maturity in females (immature, mature, berried). Life history information and size of maturity are readily available from literature. Due to minimal data requirements, LB-SPR is a simple, cost-effective tool in providing estimates for BSC stocks.