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

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A spawning aggregation is said to occur when two criteria are satisfied: that an ‘aggregation’has formed and that ‘spawning’ is occurring (Colin et al 2003; SCFRA database: (http://www.scrfa.org/database). An aggregation is defined as finding densities of at least 4 times that of nonreproductiveperiods (Domeier 2012), whereas confirmation of reproductive activity is by eitherdirect or indirect indicators. Direct indicators are observations of spawning or the presence ofhydrated eggs and/or post-ovulatory follicles (direct signs). Indirect indicators are spawning-relatedbehaviours, such as courtship, colour changes, high catches of gravid fishes and seasonal increasesin GSI. This study was unable to confirm that an aggregation had formed because of limitedinformation on reproductive and non-reproductive fish densities, incomplete fisheries landingsstatistics and the lack of access to gonads. However, the seasonally limited and site-specific fisheryfor E. lanceolatus is most parsimoniously explained by the occurrence of a transient spawningaggregation and this is supported by the video footage obtained by the local diving companyExtreme Bluewater Spearfishing. To further verify this, we would need to monitor handline catchesat Kizimkazi and other Unguja Island landing sites year-round for at least two years. Remotelyoperated video (ROV) cameras could also be set on the site to monitor in situ fish behaviour andobserve spawning.Lunar periodicity in spawning of groupers is common, and is often synchronised with the fullmoon or new moon (Sadovy 1996; Sadovy de Mitcheson et al. 2008; Colin 2012). The factthat numbers of fish, albeit low, were caught throughout the lunar month would suggest that E.lanceolatus migrate to the site, potentially from all around Unguja Island, and remain on or nearthere for the duration of the season, where they are accessible to fishers. This is also seen in itscon-specific the Goliath grouper in the Caribbean (Ferreira et al. 2012). However, egg maturation,spawning behaviour and gamete release may be restricted to a few days within the lunar month.This periodicity is typical of many groupers that migrate long distances to spawning aggregations(Nemeth 2012). Catch landings, fishers knowledge, the FGD and GSI gave conflicting resultsregarding full or new moon timing of aggregations. Catch landings suggest FM and first quarterspawning, however, GSI gave no indications of spawning periodicity relative to moon phase. Forthe current study, GSI proved an unreliable indicator of spawning seasonality, in part becausegonads were not reliably sexed. Since ovaries are better indicators of spawning timing, knowing thesex of sampled fish would have enhanced our ability to determine seasonal and lunar reproductivepatterns (Samoilys and Roelofs 2000). In contrast, the FGD stated new moon and last quarterspawning. The video footage of the aggregation was taken on the new moon (LD 29). Finally,higher catches during full moon may reflect changes in feeding behaviour rather than spawning.Although inconclusive, together these results suggest this species may aggregate on site throughoutthe spawning season, spawns around the new moon and is more readily caught by hook and lineduring the first quarter and full moon.The fishery for Giant grouper in Zanzibar is unique in being highly targeted, with the use ofspecialised gear and highly constrained fishing, seasonally and spatially. We propose that the datapresented here combined with known spawning behaviour of large groupers (e.g. E. itajara; Ferreiraet al. 2012) strongly suggests that the Zanzibar fishery is targeting a single spawning aggregationof E. lanceolatus. If this aggregation represents the only spawning aggregation site for the Giantgrouper population that resides on Unguja Island, then an indication of the possible catchmentarea of this site is 3,331km 2 , based on the total area of coastal waters to 50m depth around theisland. Since this species is Vulnerable under IUCN Redlist criteria, is naturally rare, and mayhave a single transient spawning aggregation on Unguja Island, which may represent the totalreproductive effort for participating individuals (Sadovy and Eklund 1999), we propose that thisfishery is not sustainable. Comparison with the closely related Eastern Pacific/Atlantic Goliathgrouper, Epinephelus itajara, which once formed aggregations of 100-150 individuals (Colin 1994)but recent estimates range from 0-12 (Ferreira et al. 2012), are useful. Assuming aggregationssizes and reproductive periodicity are similar, a seasonal catch of 64 E. lanceolatus in Zanzibar in100
2009-2010 would suggest that previous aggregations were sizable if this fishery has persisted forgenerations, but the low productivity of this species and improvements in fishing technology aredepleting the aggregation. Recently, subsequent to the surveys and interviews, Kizimkazi fishershave reported to one of us (NJ) that the total catch in the 2011-2012 season has declined to ca. 45individuals. We have also received anecdotal reports of increased incidental catch, which may reflectgreater numbers of shark fishers operating with the same heavy hook and line gear used to catchE. lanceolatus. Using the vulnerability framework described later in Chapter 11, we assessed thisspecies and its fishery as highly vulnerable because: a) fishers’ knowledge of the seasonal occurrenceof the Giant grouper aggregation is good; b) fishers’ access to the site is high; c) aggregationfishing may be the main driver of potential population collapse, since fishers catch E. lanceolatuspredominantly when aggregating, although year-round data are scant; d) there is no regulatoryco-management framework for this species in Zanzibar; and e) the market demand is relativelyhigh, since the fish are valuable in the Zanzibar town market. In conclusion we recommend thatZanzibar fisheries management agencies and institutes initiate discussions with fishers as a matterof urgency regarding this aggregation-based fishery before it disappears.101
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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
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pooled sizes of the three spawning
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found S. sutor contributed up to 44
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2011b). However, observations of fi
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MethodsTo identify seasonal and lun
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n=199Females GSI (mean ± SE)2.521.
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The estimate of size at maturity in
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This study was designed to verify S
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were selected. Fish selected for ta
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The number of traps increased on th
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Of the 9 tagged fish detected by re
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Fig. 7. Diel patterns ofdetection f
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Spawning aggregation site fidelity
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Chapter 6: Shoemaker spinefoot rabb
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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 80 and 81: eported aggregations forming betwee
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 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
Page 130 and 131: The approaches identified above are
Page 132 and 133: during full moon periods. Siganus s
Page 134 and 135: model, many parameter estimates are
Page 136 and 137: ReferencesAbunge C (2011) Managing
Page 138 and 139: Cox DR (1972) Regression models and
Page 140 and 141: Grüss A, Kaplan DM, Hart DR (2011b
Page 142 and 143: Kaunda-Arara B, Rose GA (2004a) Eff
Page 144: Newcomer RT, Taylor DH, Guttman SI
Page 147 and 148: Sancho G, Petersen CW, Lobel PS (20
Page 149 and 150: Appendix 1. QuestionnaireMASMA SPAW
Page 151 and 152: 8. Spawning aggregation knowledgeUs
Page 153 and 154: Example items KSh Furthest site Clo
Page 155 and 156: Appendix II. Experimental testing o
Page 157 and 158: Clove oil concentrationAt a concent
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Appendix III. Application of acoust
Page 161 and 162:
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