Résumé
Silky shark in the Indian Ocean can be targeted by some semi-industrial, artisanal and recreational fisheries, and is a bycatch of industrial fisheries such as pelagic longlines and purse seines. Currently there are not stock status estimations, but the WPEB has in its workplan a first assessment of this species in 2019. The objective of this paper is to provide preliminary support for that scheduled assessment, namely by providing: 1) a reconstruction of the time series of catches, 2) explore the possibility to standardize CPUEs for the EU pelagic longline fleets, 3) estimate prior for intrinsic population growth rate (r) and 4) test the feasibility to implement a data-limited assessment model (CMSY) and 5) provide a tentative stock status. From the final CMSY model configuration tested, the catches of silky shark in the Indian Ocean exceeded MSY from 1994 onwards. The exploitation rate for 2015 (last year in the model) was predicted to be well above MSY-level (F2015/Fmsy = 2.07). The estimation of current biomass (B2015) was 1.03 of Bmsy, with a considerable margin of uncertainty in the prediction (0.44-1.39), meaning that at present the silky shark stock in the Indian Ocean is subject to overfishing but not yet overfished. A fishing reduction to the levels observed in the late 1990s and early 2000s (around 9,000 t) would likely be sustainable. However, given the current level of uncertainty, the estimated lower 95% confidence limit of MSY (6,400 t) could serve as a more conservative guidance for total allowable catches. Due to the preliminary nature of this work and considerable uncertainty associated with the estimations, management advice is not clear. However, this work it could serve as a starting point to the scheduled 2019 IOTC silky shark assessment