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

Fig. 2 Yield-per-recruit normalized by maximum yield-per-recruit in the absence of NTRs (YPR/YPR max), as a functionof multiplier of fishing effort (mE base) for NTR scenarios #2, #4, #7 and #8 (see Table 1 for a description of the differentNTR scenarios). (a,b) is for rabbitfish, while (c,d) is for grouper. The fraction of spawning sites or normal residence areasin NTRs, C r, is 30% and 60% for (a,c) and (b,d), respectively. E baseis the default level of annual fishing effort exerted onthe population and is indicated by a dashed-dotted blue line. The level of annual effort at which yield-per-recruit reaches amaximum in the absence of NTRs is indicated by a dashed-dotted red line for rabbitfish. (See colour plates.)conventional NTRs (Grüss et al. 2011b). Moreover, from acoustic studies on grouper populations,evidence is emerging that a proportion of individuals may not attend the spawning aggregationsthat form at a particular site in all reproductive months (Starr et al. 2007; Rhodes et al. 2012).While there is no evidence to suggest that they attended other, unmonitored spawning aggregationsites in those ‘missed’ reproductive months, such behaviour also constitutes infidelity in so far asfidelity can be measured as the level of participation in all spawning aggregations that form ata particular site. Assuming adults that miss attending a spawning aggregation in any particularperiod remain in normal residence areas, infidelity of this type will not undermine spawning stockbiomass through effort reallocation to unprotected spawning sites, although conservation benefitsmay be constrained as less of the population will be protected than expected. However, such aconstraint is likely to be minor in groupers due to the much lower levels of catchability associatedwith normal residence areas. Clearly there is a degree of risk in extrapolating individual behaviourto the population-level, especially if tagging sample sizes are low and polymorphic spawningbehaviour occurs (Grüss et al. 2011a). From a conservation perspective, it may be preferable todeconstruct fidelity into ‘site’ and ‘aggregation’ components to ensure that fidelity does not onlyinvoke the use of a single site for spawning, but also the proportion of the population’s attendanceat aggregations across spawning periods. Therefore, we recommend that fidelity assumptions beexamined in models, especially for families other than groupers for which less is known regardingtheir spawning behaviour.120