TítuloMetapopulation dynamics in the spider crab "Maja squinado" : implications for fisheries management
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(2) The spider crab Maja squinado AGE SEASON PHASE 0. May - Nov. LARVAE. Aug - Sep. Shallow waters. Settlement JUVENILE. 2+. EVENT HABITAT. Growth. Pubertal moult. PRIMIPAROUS FEMALE Sep Oct - Nov. Gonad maturation Migration Deep waters. Gonad maturation Jan - Feb Feb - Apr. Mating Spawning. Migration. Jan - Feb. 3+. Mar - Jun. Hatching Spawning. MULTIPAROUS FEMALE. Shallow Waters. Jun - Nov (2 addittional broods). Incubation Gonad maturation. Female life history.
(3) Galicia, NW Spain Golfo Artabro. Costa da Morte Ría de Arousa.
(4) Shallow-water coastal habitats n. 0-15 m. n. Rocky and sandy bottoms.
(5) Objetives a.. Existence and characteristics of the spider crab metapopulations. b.. Modeling population dynamics and fisheries to incorporate metapopulation characteristics. c.. Development of alternative management policies for sustainable fisheries.
(6) Methods and information sources n. Sampling with suction pumps: Postlarval recruitment.
(7) Methods and information sources n. Sampling with experimental traps and beam trawl: Spatial distribution and temporal dynamics in shallow habitats, local dynamics: – recruitment – growth – mortality.
(8) Methods and information sources n. Ultrasonic telemetry and data storage tags: Habitat use, movements and migratory behaviour.
(9) Methods and information sources n. Mark-recapture experiments: Population structure and connectivity.
(10) Methods and information sources n. n. Observations of fishing operations with gill-nets: Spatial distribution and temporal dynamics in deep habitats Fishers’ ecological knowledge (FEK): Habitat use, spatial distribution and temporal dynamics.
(11) Spatial scales involved n. Within local populations: 1s - 100s m. n. Among juvenile local populations: 100s - 1000s m. n. Metapopulation (juvenile and adult local populations): 10s – 100s km.
(12) Individual behaviour Ontogenetic habitat shifts of juveniles. n. 9 Sep 99. 0. 10. 20. >30 0. 1. 2. 3. Distance from coastline (km). Number of crabs. Depth (m). 6. 3. 0 40. 60. 80. 100. 120. CL (mm) - 105. Age (months) 0 - 18. Juv. 1+. 67 - 120. 17 - 26 (38). 160. 24 Oct 99 18 Sand Rock. 12. Phase Juv. 0+. 140. 6 0 40. 60. 80. 100. 120. 140. Carapace length (mm). 160.
(13) Spatial distribution in local populations n. Aggregative behaviour in shallow habitats Juveniles. Adults. 1 km. MALES. FEMALES. MALES FEMALES. Jan-May. Jul. Sep. MALES. FEMALES FEMALES. Jun-Aug. Aug. Oct.
(14) Spatial distribution in local populations n. Mark-recapture: transfer among local populations % RECAPTURES Nm Nr Bast. 6752 417 Canide 1743 63 1 km Channel. Canide. Bastiagueiro. Shallow Deep Bast. Canide Channel 99.0% 0.5% 0.5% 3.2% 87.3% 9.5% Nm = no. of juveniles marked Nr = no. recaptured as juveniles.
(15) Individual behaviour n. Reproductive migrations of adults to deep habitats 21. -10. 20 0. Adult female migrating up to 95 m deep and returning to shallow waters. 19 10. 18 17. 20. 16 30. Celsius (°C). Depth (m) Temp (ºC). 14. 40. 13 50 12 60. 11 10. 70. 9 80 8 90. 7 6. 100 2000-10-11 2000-11-10 2000-12-10 2001-01-09 2001-02-08 2001-03-10 2001-04-09 2001-05-09. Nov. Dec. Apr. 2001-06-08. Meters (m). 15.
(16) Spatial distribution in local populations Depth (m). Connectivity juveniles-adults. n. 0. 10. >30. 160 0. 1. 2. Distance from coastline (km) Phase Juv. 1+. CL (mm) 67 – 120. Adults. >120. >3.
(17) Spatial distribution in local populations n. Recaptures from the fishery of adults in deep waters (scale of adult populations in mating habitats). 5 km. 6 km. Golfo Artabro. Release Recapture. Ría de Arousa Telemetry experiments.
(18) Dynamics of local populations Time series of abundance in local shallow-water populations: recruitment, mortality, onset of maturity and migration Bastiagueiro 17.6 20.7. 9. Juveniles Adults Recruitment Terminal moult. 6 3. Oct. Aug. Jun. Apr. Feb. Dec. Oct. Aug. Jun. Apr. Feb. 0 Dec. CPUE (males / trap). 12. “Source”: net adult production. Canide 25 20. “Sink”: no adult production. 15 10 5 Oct. Aug. Jun. Apr. Feb. Dec. Oct. Aug. Jun. Apr. Feb. 0 Dec. CPUE (males / trap). n.
(19) Dynamics of local populations Size structure of local populations: recruitment and growth dynamics RECRUITMENT. 28. 30. June 98. 12 6. 12. 60. 80. 100. 120 140. July 98. 8 4 0 40. May 98. 20. 18. 0 40. GROWTH AT MOULT. 24. CPUE (juvenile males / trap). 24. CPUE (juvenile females / trap). n. 16 12 8 4 0 40. 60. 80. 100 120 140 160. 24 20. June 98. 16 12 8 4. 60. 80. 100. 120 140. Carapace length (mm). 0 40. 60. 80. 100 120 140 160. Carapace length (mm).
(20) Stage-dependent population dynamics 3rd recruitment <60 <60. 2nd recruitment. 67 78 78 90. 67. <60 1st recruitment. 67 78. Rocky subtidal (0-5 m). 90 105. Sandy subtidal (5-15 m). 67 78 90 105 120 Adults. 0. 6. 12. 18. 120 140 155. 24. 120 Juveniles. Sandy subtidal (5-15 m). 120 140 Adults 155. Deep. 120 140 155. 28. 30. 36. 42. Time (months) Fishing season. 48. 52.
(21) CONCLUSSIONS: Metapopulation structure n. Characteristics of the juvenile segment of metapopulation Postlarval recruitment. Juv. 1+. Growth Mortality. Juv. 0+ 100 m 1 - 10 km. Connectivity among local populations Ontogenetic habitat shifts.
(22) CONCLUSSIONS: Metapopulation structure n. Characteristics of the adult segment of metapopulation 10 - 100 km Female migration (to shallow waters). Adults. Juv. 1+ + Postpubertal adults. Mating Fishing mortality Migration Terminal moult.
(23) MODELLING POPULATION DYNAMICS: Spatially-explicit yield- and egg-per-recruit models n. Stage structure: size, age, maturity and habitat. n. Spatial structure. Depth (m). FISHERY • Divers / Intertidal harvesters • Gillnets / divers • Gillnets 3 1 2 0. PROTECTED AREAS Rocky 0-5 m. Larvae. 10. Sandy 5-15 m. 20. Migration corridors / Deep. >30 0. 1. 2. 3. 4. Distance from coastline (km). 5. OPEN AREAS Phase Juv. 0+ Juv. 1+ Adults Adults.
(24) Yield- and egg-per-recruit analyses: Results without MPAs 0.5. 1. Fa = 1. 52. F a = 0.5. Control of fishing mortality to maximize yield and egg production: HOW?. 54. 0.3 38 40 42. 44. 46. 56. 48. 60. 58. 0.2. 62. 0.1 36. 64. 50. 0.0. 66. 0 0.0. 0.1. 0.2. 0.3. 0.4. 0.5. 0. 1. 2. 2 58. Fa = 2. 60. 60 63. Fa = 3. Fj0. 62. •Artisanal small-scale fisheries •Multi-fleet and multi-gear •No effort data •No catchability information. 64. 66. 1. 1 66. 69. 68 72. 70 72. 78. 74. 0. 1. 2. 75. 81. 0. 0. 0. 1. 2. F j1. 2. 60 62. Biomass yield (g / recruit). Fa = 4. 64 66. Fj0. n. Fj0. 0.4. 1. 68 70. 84. 0 0. 82. 80. 78. 76. 72 74. 1. Fj1. 2. FISHING MORTALITIES: Fj0: juv. 0+ Fj1: juv. 1+ Fa: adults.
(25) Yield- and egg-per-recruit analyses: Results with MPAs Lets allow fishing mortality to be an uncontrolled variable (in open areas). Reproductive effort (eggs · 1000 / recruit). Biomass yield (g / recruit). n. 80. 80. 60. 60. 40. 40. 10. 10. 1. 1 10 25 50 75 90 100. Juv. 0+. 10 25 50 75 90 100. Juv. 1+. 10 25 50 75 90 100. Juv. 0+ / 1+. 10 25 50 75 90 100. Adult. Percentage of habitat protected. No reserves.
(26) CONCLUSSIONS: Modelling population dynamics CONSIDERATIONS n Regulations based in direct control of fishing effort are difficult to implement n n. MPAs are easier and cheaper to implement in coastal areas MPAs and minimum sizes are understood and well accepted by fishers. RESULTS OF ANALYSES n MPA performance is robust to uncertainties in Fs in open areas n n. Performance of regulations based on MPAs is similar or higher than others based in direct control of effort The best MPA designs should implement closures in most of the juvenile habitat in shallow waters. REGULATION IMPLICATIONS n Direct efforts to implement MPAs and minimum landing sizes n Do no invest too much effort trying to control fishing effort in areas open to the fishery.
(27) A new management policy is needed: Community-based co-management systems are working for other resources CHARACTERISTICS. CENTRALIZED MODEL (bureaucreatic / government). Property rights. State No access limitation. COMMUNITY COMANAGEMENT MODELS Community (TURFs) Access limitation. Top-down Autonomous goverment. Bottom-up Fishers’ organizations. Scientific. Traditional Scientific. Decission-making · Flows · Institutions involved Knowledge sources Regulations. Compliance systems · Surveillance · Punishments. • Inputs: gears, seasonal closures, minimum sizes • Outputs: daily quotas per vessel or fisher. State Legal. • Inputs: minimum sizes, seasonal closures • Outputs: daily quotas per vessel or fisher • MPAs and rotations Fishers organizations Social (+ legal).
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