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

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eported aggregations forming between January and April, while five and four fishers mentionedFebruary and March, respectively (Fig. 7). Fishers were less knowledgeable on the lunar timing ofspawning aggregations, with only two fishers reporting new moon spawning.DiscussionObservations of spawning-related behaviour at aggregations sites, increased densities of fish andfishers’ knowledge combine to provide strong evidence for the occurrence of E. fuscoguttatusspawning aggregations at two sites on the south coast of Kenya.The spawning behaviour observed for E. fuscoguttatus in Kenya is typical of many grouper thatspawn in pairs within aggregations (Samoilys and Squire 1994; Samoilys 1997b; Johannes et al.1999; Robinson et al. 2008). The distinct male colour changes and males swimming high up in thewater column have also been described in Palau and Seychelles (Johannes et al. 1999; Robinsonet al. 2008b). Strong territorial behaviour by males at aggregation sites, as seen in the smallermore mobile grouper, such as Plectropomus leopardus (Samoilys 1997b), was not apparent. Thoughaggressive encounters between males occurred, demarcation of territories was not observed,possibly as a reflection of the low densities that characterised the site. A lack of aggression betweenmales during the development of a spawning aggregation in this species has been documentedin Seychelles, where the level of aggression increased with aggregation density (Robinson et al.2008b). Clear demarcation of territories occurred in the high density aggregations at FarquharAtoll, with males regularly chasing other males out (Robinson et al. 2008b).Fig. 7. Number of fishers who positively described monthly periodicity of E. fuscoguttatus spawning aggregations(n=32, 8 fishers with knowledge of spawning aggregations)Spawning rushes and the release of gametes, direct evidence that aggregations have formed for thepurpose of spawning, were not observed. This may be explained by SCUBA observations beinglimited to between 0900 and 1700 for boat safety reasons, since the sites were seaward of thefringing reef. However, courtship behaviour was observed as late as 1650 suggesting that spawningoccurred after that, as has also been suggested for this species in Seychelles (Robinson et al. 2008b).Other grouper species are known to spawn during a narrow window before, during and after sunset(Colin et al. 1987; Samoilys 1997b; Domeier and Colin 1997; Heyman et al. 2005; Rhodes andSadovy 2002a). The proportion of males in aggregations, 45% during December, is high for thisprotogynous grouper where overall population sex ratios are normally female-biased (Pears et al.2007). This may be explained by females remaining hidden in the coral during survey periods. Theobservation of a male courting a female hidden deep within the coral supports this. Alternatively,sex ratios at aggregations may not mirror the overall population sex ratio, especially if females donot attend every aggregation (Rhodes et al. 2011).72
Our UVC surveys did not provide conclusive evidence on reproductive seasonality or spawningbecause counts were not continued throughout the year or lunar month. However, the surveyestimates of a three-month season (December-February) partially overlap with fisher reports of 4months (January-April, Samoilys et al. 2006). Monitoring of acoustically tagged E. fuscoguttatus inSeychelles identified a 2-3 month aggregation period, with lower abundance in the final month.In Seychelles the spawning period started as early as November and finished as late as March (seeChapter 8). Pears et al. (2007) found that E. fuscoguttatus spawns for 3 months (November-January)on the Great Barrier Reef, while Hamilton et al. (2012b) report 4-5 months (between Decemberand March) in Solomon Islands. Our winter count at the spawning site in July was relatively high.Possibly there is reproductive activity in winter, which is unknown to local fishers; however, thisis not supported by studies in other regions. Collectively, these studies on E. fuscoguttatus in theIndo-Pacific indicate a 3-5 month spawning season for E. fuscoguttatus during the Austral summer.In Kenya we found spawning aggregations occurred around the new moon (LD 28-2), which isalso reported from Seychelles (Robinson et al. 2008b), Palau (Johannes et al. 1999), and Indonesia(Komodo, Pet et al. 2005; Mangubhai et al. 2011). In contrast, the species appears to spawn justafter full moon in Pohnpei, Micronesia (Rhodes et al. 2012) and in Solomon Islands aggregationswere found on both new and full moon (Hamilton et al. 2012b). Our observations of a gravidfemale during full moon requires further investigation but may suggest both lunar phases are usedin Kenya. From studies elsewhere, E. fuscoguttatus aggregations gradually develop 1-3 weeks inadvance of actual spawning. During these periods, females arrive later and stay for shorter periodsthan the males (Robinson et al. 2008b, Nemeth 2012; Rhodes et al. 2012).The mean number of E. fuscoguttatus at the KM aggregation site was 21 fish, corresponding to adensity of 7.6 fish/1000 m 2 . This compared with a non-spawning number of 6 fish (2.2 fish/1000 m 2 ).Spawning aggregations were confirmed (4-fold increase, Domeier 2012) in December-February atKM. Our estimate of non-spawning density (2.2 fish/1000 m 2 ), though sample size was small, iscomparable to estimates from UVC surveys elsewhere in the eastern African region, where densitiesranged from 0.8 (Mozambique) to a maximum of 3.2 (Tanzania) fish/1000 m 2 , with a mean of 1.8(±0.73 SE) fish/1000 m 2 from three surveys sites. E. fuscoguttatus were not seen at a further 69 sites(Samoilys unpubl. data). E. fuscoguttatus aggregation sizes in Kenya appear small and most closelyresemble those from Komodo, Indonesia, where high aggregation fishing pressure is reported (Pet.et al. 2005; Mangubhai et al. 2011). Densities at the KM site are 4 to 10-fold less than those fromSolomon Islands, Palau, Micronesia and Seychelles (Johannes et al. 1999; Robinson et al. 2008b;Hamilton et al. 2012b; Rhodes et al. 2012). Possibly, fishing pressure is sufficiently intense that ithas depleted numbers at this site. However, it is not strictly valid to assess the status of an aggregationthrough comparison with different sites as aggregation size may vary substantially within the samereef system (Johannes et al. 1999; Robinson et al. 2008b; Mangubhai et al. 2011). For example, atFarquhar Atoll in Seychelles, E. fuscoguttatus forms aggregations ranging in size from 10s to 100sof individuals at different sites and size is not obviously related to fishing pressure, since the largeraggregations (68 fish/1000 m 2 ) occur at the most heavily exploited site (Robinson et al. 2008b; seeChapter 8). Recent studies of groupers have demonstrated complex dynamics within aggregationsites, with the actual spawning or core site being small and nested within a larger courtship area,which is further nested within a staging area (Nemeth 2012). This has been demonstrated in E.polyphekadion and E. fuscoguttatus in Seychelles (Robinson et al. 2008b). Our surveys in Kenya werenot sufficient to determine these zones but it is likely that the KM area of 2,744m 2 includes thecore area and most of the courtship area, since courting individuals were observed 100m beyondthe southern boundary. Densities will therefore depend on whether the core area alone is used orincludes the staging area. We also cannot discount the possibility that Kenya is characterised bysmall aggregations of this species, or that larger aggregations of E. fuscoguttatus may form elsewherein southern Kenya, particularly if located on deeper fringing or submerged reefs where fishingeffort is generally constrained (Samoilys et al 2011b).73
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The designation of geographical ent
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Chapter 1: IntroductionJan Robinson
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limited, subsistence levels of expl
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NTRs for spawning aggregations usin
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al. 2003). Verification may include
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a fraction of spawning sites are pr
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Chapter 3: Targeted fishing of the
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verifying spawning aggregations, we
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ecorded from inshore close to the c
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(a)(b)Fig. 3. Spatial patterns ofca
Page 30 and 31: pooled sizes of the three spawning
Page 32 and 33: found S. sutor contributed up to 44
Page 34 and 35: 2011b). However, observations of fi
Page 36 and 37: MethodsTo identify seasonal and lun
Page 38 and 39: n=199Females GSI (mean ± SE)2.521.
Page 40 and 41: The estimate of size at maturity in
Page 42 and 43: This study was designed to verify S
Page 44 and 45: were selected. Fish selected for ta
Page 46 and 47: The number of traps increased on th
Page 48 and 49: Of the 9 tagged fish detected by re
Page 50 and 51: Fig. 7. Diel patterns ofdetection f
Page 52 and 53: Spawning aggregation site fidelity
Page 54 and 55: Chapter 6: Shoemaker spinefoot rabb
Page 56 and 57: anterior of the anus and below the
Page 58 and 59: A high percentage (80.8%) of depart
Page 60 and 61: arrivals and departures at these tw
Page 62 and 63: are typically applied for reef fish
Page 64 and 65: (a)(b)(c)Chapter 3, Figure 3. Spati
Page 66 and 67: (1)(2)(3)(4)(5)(6)Chapter 7, Table
Page 68 and 69: Chapter 12, Fig. 1 Fraction of fema
Page 70 and 71: Plates 8. Selected photographs from
Page 72 and 73: MethodsStudy sitesThe study area wa
Page 74 and 75: which shelved gently ( ca. 25 o ) t
Page 76 and 77: Fig. 4. Lunar periodicity in number
Page 78 and 79: Behaviour and appearanceDescription
Page 82 and 83: The sizes of E. fuscoguttatus aggre
Page 84 and 85: Materials and methodsStudy area and
Page 86 and 87: TL. All fish tagged were considered
Page 88 and 89: Lunar timing of arrivals and depart
Page 90 and 91: Fig. 8. The presence and absence of
Page 92 and 93: aggregation fishing. This critical
Page 94 and 95: Chapter 9: Persistence of grouper (
Page 96 and 97: ResultsBetween 2003 and 2006, the c
Page 98 and 99: Fig. 2. Mean (± standard error, SE
Page 100 and 101: A few species (e.g. Epinephelus gut
Page 102 and 103: (a)(b)Fig. 1. Map of (a) study site
Page 104 and 105: Fig. 2. Number of E. lanceolatus ob
Page 106 and 107: was having any impact on the popula
Page 108 and 109: A spawning aggregation is said to o
Page 110 and 111: Chapter 11: Evaluation of an indica
Page 112 and 113: Table 1 Aggregation fisheries asses
Page 114 and 115: the lists of Jennings et al. (1999)
Page 116 and 117: with the more vulnerable labrids an
Page 118 and 119: The remaining serranid populations
Page 120 and 121: Spawning aggregation behaviour is c
Page 122 and 123: tiger grouper, Mycteroperca tigris:
Page 124 and 125: of protecting the normal residence
Page 126 and 127: • Since grouper males are afforde
Page 128 and 129: Fig. 2 Yield-per-recruit normalized
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The approaches identified above are
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during full moon periods. Siganus s
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model, many parameter estimates are
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ReferencesAbunge C (2011) Managing
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Cox DR (1972) Regression models and
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Grüss A, Kaplan DM, Hart DR (2011b
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Kaunda-Arara B, Rose GA (2004a) Eff
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Newcomer RT, Taylor DH, Guttman SI
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Sancho G, Petersen CW, Lobel PS (20
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Appendix 1. QuestionnaireMASMA SPAW
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8. Spawning aggregation knowledgeUs
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Example items KSh Furthest site Clo
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Appendix II. Experimental testing o
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Clove oil concentrationAt a concent
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Appendix III. Application of acoust
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