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

Two main types of spawning aggregations have been defined: transient and resident (Domeier andColin 1997; Domeier 2012). Transient spawning aggregations persist for several days or weeks,usually form around specific lunar phases within certain months of the year, and may involve relativelylong migrations for participating fish. Resident spawning aggregations form more regularly,often over a lengthy spawning season, last for shorter periods (minutes to hours), and occur closeto or within the areas of residence for participating fish (Domeier and Colin 1997; Domeier 2012).It has been suggested that transient spawners are more vulnerable to aggregation fishing thanresident spawners (Domeier et al. 2002), not least because a significant proportion of the annualreproductive output of participating fish may be invested in a single aggregation (Shapiroet al. 1993). However, within these broad types of transient and resident spawners, vulnerabilityis expected to vary depending on the relative importance of any single aggregation to the annualreproductive output of the population, as well as on predictability and concentration of aggregations.For example, some transient spawners form relatively small aggregations at numerous sitesand also spawn outside aggregations (e.g. Plectropomus leopardus; Samoilys 2000, 2012), whileothers form numerous, large aggregations across a protracted spawning season (e.g. Robinson etal. 2011). In both cases, the contribution of each aggregation to annual reproductive output isreduced compared to transient spawners that spawn in large aggregations at a few sites and withina narrow time period. Transient spawners forming aggregations that are patchily distributed orvary slightly in their location on inter-annual scales may be less vulnerable than transient spawnerswhich form predictable, spatially discrete, highly concentrated aggregations such as Nassaugrouper, Epinephelus striatus (Sadovy et al. 1994; Sadovy and Eklund 1999).Table 2. Spawning aggregations verified in the western Indian Ocean prior to 2009. Verification of spawning and aggregationformation based on Colin et al. (2003). (After Robinson et al. 2008b).Country Site SpeciesSpawning*Direct IndirectAbundance**S1 Epinephelus polyphekadion Yes Yes YesS1 E. fuscoguttatus Yes Yes YesS1 Plectropomus punctatus Yes No NoS2 E. polyphekadion Yes Yes NoS2 E. fuscoguttatus No Yes NoS2 P. punctatus Yes No NoS3 E. polyphekadion No Yes YesS3 E. fuscoguttatus No Yes YesS4 P. punctatus Yes Yes NoS5 E. polyphekadion No Yes YesS6 Siganus sutor Yes Yes NoS7 S. sutor Yes No NoK1 E. fuscoguttatus No Yes NoK2 E. fuscoguttatus No Yes NoK3 Mulloidichthys vanicolensis No Yes NoK4 M. vanicolensis No Yes NoK5 M. vanicolensis No Yes NoSeychellesKenya*: Direct signs of spawning include observations of gamete release or hydrated ovaries. Indirect signs include patternsin gonado-somatic index, colour changes and territorial/courtship behaviour associated with spawning, andobservations of gravid females. **: Increases in abundances determined quantitatively. ases in abundances or densitiesdetermined quantitatively; No = determined qualitatively.Based on a growing literature documenting the vulnerability of reef fish that spawn in aggregations,Sadovy and Domeier (2005) proposed that aggregation fishing may only be sustainable at3