Integrating Fisheries Dependent and Independent Approaches to assess Fisheries, Abundance ...

170 Pages·2014·2.1 MB·English

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

Dissertation by
Julia L.Y. Spät

In Partial Fulfillment of the Requirements
For the Degree of
Doctor of Philosophy

King Abdullah University of Science and Technology
Thuwal, Kingdom of Saudi Arabia

May 2014
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EXAMINATION COMMITTEE APPROVALS FORM

The dissertation/thesis of Julia Spät is approved by the examination committee.

Committee Chairperson: Dr. Michael Berumen

Committee Members: Dr. Xabier Irigoyen
Dr. Timothy Ravasi
Dr. Friedhelm Krupp
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© May 2014
Julia Spät
All Rights Reserved
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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
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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.
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TABLE OF CONTENTS
Page
EXAMINATION COMMITTEE APPROVALS FORM .......................................... 2
COPYRIGHT PAGE ................................................................................................. 3
ABSTRACT ............................................................................................................... 4
TABLE OF CONTENTS ........................................................................................... 6
LIST OF ABBREVIATIONS .................................................................................... 7
LIST OF FIGURES ................................................................................................... 8
LIST OF TABLES ..................................................................................................... 10
CHAPTER 1: INTRODUCTION & LITERATURE REVIEW ................................ 11
CHAPTER 2: FISH MARKET SURVEYS .............................................................. 48
CHAPTER 3: BRUVS AND LONGLINE SURVEYS ............................................. 93
CHAPTER 4: POPULATION CONNECTIVITY .................................................... 124
SUPPLEMENTARY MATERIAL………………………………………………… 160
GENERAL CONCLUSIONS……………………………………………………… 163
APPENDIX 1: LIST OF PUBLICATIONS ................................................................ 169
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LIST OF ABBREVIATIONS
AIMS Australian Institute of Marine Science
BRUVS Baited Remote Underwater Video Surveys
CPUE Catch Per Unit Effort
FAO Food and Agricultural Organization
H Expected Heterozygosity
E
H Observed Heterozygosity
O
HWE Hardy-Weinberg Equilibrium
IUCN International Union for the Conservation of Nature
IPOA International Plan of Action
L Total Length
T
mtDNA CR Mitochondrial DNA Control Region
MPA Marine Protected Area
TN Tamura-Nei
UAE United Arab Emirates
UVS Underwater Visual Surveys
WIO Western Indian Ocean
W Disc Width
D
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LIST OF ILLUSTRATIONS

Chapter 1
Figure 1: Map of elasmobranch research in the Red Sea.................................................. 20
Chapter 2
Figure 1: Sampling locations ........................................................................................... 51
Figure 2: Species composition ……................................................................................. 59
Figure 3: Cumulative species curve ………..................................................................... 60
Figure 4: Seasonal landing trends..................................................................................... 61
Figure 5: Size classes ....................................................................................................... 65
Figure 6: Mean vs. maximum sizes..……….................................................................... 67
Figure 7: Length frequency distribution........................................................................... 68
Chapter 3
Figure 1: Sampling locations ......................................................................................... 100
Figure 2: Images of BRUV units ................................................................................... 103
Figure 3: Images taken by BRUV units ......................................................................... 106
Figure 4: BRUVS CPUE …........................................................................................... 107
Figure 5: Global BRUVS CPUE comparisons .............................................................. 108
Figure 6: Global longline CPUE comparisons ............................................................... 109
Chapter 4
Figure 1: Collection locations ........................................................................................ 130
Figure 2: Parsimony network - C.limbatus .................................................................... 141
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Figure 3: Parsimony network - C.sorrah ...................................................................... 143
Figure 4: Parsimony network - R.acutus …................................................................... 144
Figure 5: Parsimony network - S.lewini ........................................................................ 147
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LIST OF TABLES
Chapter 1
Table 1: Literature overview - Red Sea elasmobranch diversity................................ 22-23
Table 2: Literature overview - research on Iago omanensis............................................ 26
Chapter 2
Table 1: Sample interview questions................................................................................ 55
Table 2: Species list .................................................................................................... 62-63
Table 3: Maximum sizes at maturity................................................................................ 66
Table 4: Information on pregnant individuals.................................................................. 69
Table 5: Results of fishermen interviews .........................................................................70
Chapter 3
Table 1: BRUV sampling regime................................................................................... 102
Chapter 4
Table 1: mtDNA marker information............................................................................. 133
Table 2: Microsatellites………....................................................................................... 137
Table 3: F values……………...................................................................................... 138
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Table 4: mtDNA diversity……...................................................................................... 140