WIOMSA-CORDIO spawning book Full Doc 10 oct 13.pdf

The remaining serranid populations were characterised by lower extrinsic vulnerability (Fig. 5).In the Alphonse Atoll group, the aggregation fishery for E. polyphekadion is largely a subsistencefishery, whereas the Diani fishery for E. fuscoguttatus was marked by relatively low levels of fisherknowledge and accessibility. The extrinsic vulnerability of Siganus sutor populations, a speciesof moderate intrinsic vulnerability (see Fig. 2), varied mainly due to differences in gear use andmanagement. The Praslin S. sutor aggregation-fishery employs traps as the sole fishing gear onaggregations, while the Mahé fishery also uses nets and the Msambweni fishery employs a totalof four gears. A higher diversity of gears, and particularly the use of nets, considerably increasesefficiency in aggregation-based fisheries. Moreover, the Praslin S. sutor aggregation-based fishery hashistorically been governed by community-based measures that have limited access to aggregationsites and have restricted gear use to traps, social norms that are lacking at the other sites.Fig. 5 Framework to assess the vulnerability of reef fish populations to aggregation fishing, evaluated for 11 aggregationfisheries in the western Indian Ocean that are plotted by their index values for intrinsic and extrinsic vulnerability.Aggregation fisheries are coded by location and target species: AlEP = Alphonse E. polyphekadion; CoEF = CosmoledoE. fuscoguttatus; CoEP = Cosmoledo E. polyphekadion; DiEF = Diani E. fuscoguttatus; FaEF = Farquhar E. fuscoguttatus;FaEP = Farquhar E. polyphekadion; FaPP = Farquhar P. punctatus; PrSS = Praslin S. sutor; MaSS = Mahe S. sutor; MsSS= Msambweni S. sutor; ZaEL = Zanzibar E. lanceolatus. (See colour plates.)DiscussionThis preliminary evaluation highlights the potential for indicator-based frameworks to enable rapidassessment of the vulnerability of reef fish populations to aggregation fishing in data-poor contexts.However, several limitations and potential improvements to the framework were identified and arediscussed here.The intrinsic index is relatively easy to construct and based on readily available data (i.e. FishBaseand the SCRFA Global Database, 2010) for populating the indicators. Many aggregative spawnersare data deficient and it is necessary to use life history tools to provide parameter estimates forthe indicators. While it is recognised that data derived from such tools are uncertain, the index isrelative and the absolute values decrease in importance as more species of divergent life histories110