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GIS mapping and analysis of queen conch ( Strombus gigas ) stock abundance surveys in Puerto Rico

GIS mapping and analysis of queen conch ( Strombus gigas ) stock abundance surveys in Puerto Rico. Anthony R. Marshak and Richard S. Appeldoorn Department of Marine Sciences University of Puerto Rico – Recinto de Mayag ü ez. Queen Conch ( Strombus gigas ).

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GIS mapping and analysis of queen conch ( Strombus gigas ) stock abundance surveys in Puerto Rico

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  1. GIS mapping and analysis of queen conch (Strombusgigas) stock abundance surveys in Puerto Rico Anthony R. Marshak and Richard S. Appeldoorn Department of Marine Sciences University of Puerto Rico – Recinto de Mayagüez

  2. Queen Conch (Strombusgigas) • One of the most important commercial species within the Caribbean, • especially in Puerto Rico. • Greatly overfished within most Caribbean waters, with severe population • declines throughout the region

  3. Queen conch in Puerto Rico • Most PR queen conch landings concentrated in the E and W coasts, primarily SW insular platform. • Conch depletion within shallow seagrass beds, and fishing effort has moved into deeper habitats.

  4. Queen conch stock surveys • Fisheries independent stock abundance surveys: • Estimate average densities within a variety of habitats over a large area using strip transects and underwater scooters • May collect in-situ size and stage information over time. • Many management applications for monitoring the population, or its response to any mgmt action

  5. GIS Conch Plotting • Determine exact conch locations with GPS recorded transect start and endpoints • Divers record start and end time; time of encounter of conch and habitat/depth • Habitat, depth, conch size, stage incorporated into GIS accessory data. • Spatial Analyst Density calculator gives overall distribution and aggregation patterns.

  6. Survey Results of the Puerto Rico West Insular PlatformThree Surveys over a ten-year period(1995-96, 2001-02, 2006)

  7. Habitat Density Results: Total Conch

  8. Habitat Density Results by Age Class Sum all area surveyed per habitat and number of conch encountered to get densities

  9. Spatial Patterns along the West Coast of Puerto Rico

  10. Juveniles 5000 m2 radius, 1995-1996 Survey

  11. Juveniles 5000 m2 radius, 2001-2002 Survey

  12. Juveniles 5000 m2 radius, Jul-Sep 2006 Survey

  13. Adults 5000 m2 radius, 1995-1996 Survey

  14. Adults 5000 m2 radius, 2001-2002 Survey

  15. Adults 5000 m2 radius, Jul-Sep 2006 Survey

  16. Old 5000 m2 radius, 1995-1996 Survey

  17. Old 5000 m2 radius, Jul-Sep 2006 Survey

  18. Very Old 5000 m2 radius, Jul-Sep 2006 Survey

  19. Conclusions • Highest densities of juveniles and adults in all surveys within shallow seagrass • Other juv’s and adults clustered in smaller numbers in deeper algal sand habitats • Densities of 2006 survey higher than in previous surveys • Recurring large-scale conch concentrations exist along the western shelf. • These may be classified by habitats and depths • More pronounced conc’s in the SW shelf due to expansive seagrass habitat • Current patterns, habitat type, and the attraction of conspecifics are likely playing a role in the recruitment of individuals to these areas. • Juveniles are settling/recruiting into both shallow seagrass and deeper algal sand habitats, but higher proportions and densities are found within seagrasses. • Adults and older conch are somewhat more restricted in location along the shelf and lower in number.

  20. Conclusions • GIS mapping of surveys permits high understanding of large scale habitat connectivity in queen conch. • Distinct regions and their concentrations may be identified to aid in future management, and to complement stock abundance montioring • It would appear that the seasonal closures were effective in allowing for population increase, but still a long way to go. • Alee Effect at <48 conch/ha, where reproduction ceases • Future Applications: • Essential Fish Habitat • Population Dynamics • Comparison to fishermen data • Ecosystem based management • Biological and Management applications • Seasonal survey periodicity and stratification • Future studies

  21. BREAK TIME!!!(5 Minutes)

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