A preliminary stock assessment of scalloped hammerhead shark (Sphyrna lewini) in the Indian Ocean

The study conducted a demographic analysis and preliminary stock assessment to status by Leslie matrix and CMSY method for the Indian Ocean scalloped hammerhead shark (Sphyrna lewini). Monte Carlo simulation was used to integrate uncertainty of biological information and key parameters. The results indicated that scalloped hammerhead shark productivity was low, with the intrinsic rate of increase r is from 0.12 to 0.23yr-1, and the most uncertainty is inconclusive fecundity where the litter size is from 13 - 41 pups per year. The results are sensitive to the final depletion level, and all scenarios reveal that the average of the last three-year catch is lower than MSY; however, the stock status is overfished. Given the high uncertainty in the catch series and high amounts of misidentified catch, future assessments need to consider more date-limited methods based on the different sources of data and improve the reconstruction of catch series.