Integrating Fisheries Dependent and Independent Approaches to assess Fisheries, Abundance, Diversity, Distribution and Genetic Connectivity of Red Sea Elasmobranch Populations

Handle URI:
http://hdl.handle.net/10754/320296
Title:
Integrating Fisheries Dependent and Independent Approaches to assess Fisheries, Abundance, Diversity, Distribution and Genetic Connectivity of Red Sea Elasmobranch Populations
Authors:
Spaet, Julia L.
Abstract:
The Red Sea has long been recognized as a global hotspot of marine biodiversity. Ongoing overfishing, however, is threatening this unique ecosystem, recently leading to the identification of the Red Sea as one of three major hotspots of extinction risk for sharks and rays worldwide. Elasmobranch catches in Saudi Arabian Red Sea waters are unregulated, often misidentified and unrecorded, resulting in a lack of species-specific landings information, which would be vital for the formulation of effective management strategies. Here we employed an integrated approach of fisheries dependent and independent survey methods combined with molecular tools to provide biological, ecological and fisheries data to aid in the assessment of the status of elasmobranch populations in the Red Sea. Over the course of two years, we conducted market surveys at the biggest Saudi Arabian fish market in Jeddah. Market landings were dominated by, mostly immature individuals - implying both recruitment and growth overfishing. Additionally, we employed baited remote underwater video (BRUVS) and longline surveys along almost the entire length of the Red Sea coast of Saudi Arabia as well as at selected reef systems in Sudan. The comparison of catch per unit effort (CPUE) data for Saudi Arabian Red Sea BRUVS and longline surveys to published data originating from non-Red Sea ocean systems revealed CPUE values several orders of magnitude lower for both survey methods in the Red Sea compared to other locations around the world. Finally, we infered the regional population structure of four commercially important shark species between the Red Sea and the Western Indian Ocean.We genotyped nearly 2000 individuals at the mitochondrial control region as well as a total of 20 microsatellite loci. Genetic homogeneity could not be rejected for any of the four species across the spatial comparison. Based on high levels of region-wide exploitation, we suggest that, for management purposes, the population structure of all four species should be considered as single stock in the three marginal seas surrounding Arabia. Overall, our combined results indicate a severe depletion of sharks in Saudi Arabian Red Sea waters, likely caused by drastic overfishing of elasmobranch populations.
Advisors:
Berumen, Michael L. ( 0000-0003-2463-2742 )
Committee Member:
Irigoien, Xabier ( 0000-0002-5411-6741 ) ; Krupp, Friedhelm; Ravasi, Timothy ( 0000-0002-9950-465X )
KAUST Department:
Biological and Environmental Sciences and Engineering (BESE) Division
Program:
Marine Science
Issue Date:
May-2014
Type:
Dissertation
Appears in Collections:
Marine Science Program; Dissertations; Biological and Environmental Sciences and Engineering (BESE) Division

Full metadata record

DC FieldValue Language
dc.contributor.advisorBerumen, Michael L.en
dc.contributor.authorSpaet, Julia L.en
dc.date.accessioned2014-06-10T12:44:58Zen
dc.date.available2014-06-10T12:44:58Zen
dc.date.issued2014-05en
dc.identifier.urihttp://hdl.handle.net/10754/320296en
dc.description.abstractThe Red Sea has long been recognized as a global hotspot of marine biodiversity. Ongoing overfishing, however, is threatening this unique ecosystem, recently leading to the identification of the Red Sea as one of three major hotspots of extinction risk for sharks and rays worldwide. Elasmobranch catches in Saudi Arabian Red Sea waters are unregulated, often misidentified and unrecorded, resulting in a lack of species-specific landings information, which would be vital for the formulation of effective management strategies. Here we employed an integrated approach of fisheries dependent and independent survey methods combined with molecular tools to provide biological, ecological and fisheries data to aid in the assessment of the status of elasmobranch populations in the Red Sea. Over the course of two years, we conducted market surveys at the biggest Saudi Arabian fish market in Jeddah. Market landings were dominated by, mostly immature individuals - implying both recruitment and growth overfishing. Additionally, we employed baited remote underwater video (BRUVS) and longline surveys along almost the entire length of the Red Sea coast of Saudi Arabia as well as at selected reef systems in Sudan. The comparison of catch per unit effort (CPUE) data for Saudi Arabian Red Sea BRUVS and longline surveys to published data originating from non-Red Sea ocean systems revealed CPUE values several orders of magnitude lower for both survey methods in the Red Sea compared to other locations around the world. Finally, we infered the regional population structure of four commercially important shark species between the Red Sea and the Western Indian Ocean.We genotyped nearly 2000 individuals at the mitochondrial control region as well as a total of 20 microsatellite loci. Genetic homogeneity could not be rejected for any of the four species across the spatial comparison. Based on high levels of region-wide exploitation, we suggest that, for management purposes, the population structure of all four species should be considered as single stock in the three marginal seas surrounding Arabia. Overall, our combined results indicate a severe depletion of sharks in Saudi Arabian Red Sea waters, likely caused by drastic overfishing of elasmobranch populations.en
dc.language.isoenen
dc.subjectSharksen
dc.subjectRaysen
dc.subjectFisheriesen
dc.subjectRed Seaen
dc.subjectConservationen
dc.subjectGeneticsen
dc.titleIntegrating Fisheries Dependent and Independent Approaches to assess Fisheries, Abundance, Diversity, Distribution and Genetic Connectivity of Red Sea Elasmobranch Populationsen
dc.typeDissertationen
dc.contributor.departmentBiological and Environmental Sciences and Engineering (BESE) Divisionen
thesis.degree.grantorKing Abdullah University of Science and Technologyen_GB
dc.contributor.committeememberIrigoien, Xabieren
dc.contributor.committeememberKrupp, Friedhelmen
dc.contributor.committeememberRavasi, Timothyen
thesis.degree.disciplineMarine Scienceen
thesis.degree.nameDoctor of Philosophyen
dc.person.id113060en
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