AN ABSTRACT OF THE THESIS OF Hi lal Saud Ambusaidi for the degree of Master of Science in Fisheries Science presented on November 29. 1994, Title: Distribution and Assemblages of Demersal Fish in Oman. Redacted for Privacy Abstract approved: David B Sampson The Sultanate of Oman has 1700 km of coastline extending from the Arabian Gulf south to the Arabian Sea. The demersal fish distributions and assemblages have not previously been well defined. In winter, variations in the oceanography of the area are minimal. In summer, however, the Arabian Sea is strongly influenced by the southwest monsoon. For this study the continental shelf off Oman was divided into eight regional areas and research trawl data on the distribution of demersal fish assemblages was studied using two forms of multivariate statistical analysis: two-way indicator species analysis and detrended correspondence analysis. The study was carried out to examine the influence on the species assemblages of geographical zonation, seasonal variation, and factors such as depth, time of day, and distance from untrawlable ground. There was seasonal variation in the fish assemblages and this variation was greatly influenced by the summer monsoon. Within each regional area depth appeared to be the major factor determining species distribution. In addition to the multivariate analyses, univariate techniques were applied to the catch rate data for forty commercial species to study in detail the influence of time of day and distance from untrawlable ground, factors which could potentially influence stock assessment estimates of fish biomass. Because the data were highly unbalanced, they were analyzed using General Linear Model with five factors, two continuous variables, and ten interaction terms to examine variation in the log-transformed catch rates. The factors time of day and distance from untrawlable ground, in combination with other factors, had significant effects on the catch rates for half of the species. C Copyright by Hilal Saud Ambusaidi November 29, 1994 All Rights Reserved Distribution and Assemblages of Demersal Fish in Oman by Hilal Saud Ambusaidi A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science Completed November 29, 1994 Commencement June 1995 Master of Science thesis of Hilal Saud Ambusaidi on November 29. 1994 APPROVED: Redacted for Privacy Major Professor, representing Fisheries and Wildlife Redacted for Privacy Hea of Department of Fisheries an ildlife Redacted for Privacy Dean of Gra te School I understand that my thesis will become part of the permanent collection of Oregon State University libraries. My signature below authorizes release my thesis to any reader upon request. Redacted for Privacy Hilal Saud Ambusaidi, Author Dedication In memory of my parents May Allah forgive them and enter them into paradise. To my wife, my daughters Zuhrah and Noor, to my brothers especially, Ahmad Al-Amry and Bador Ambusaidi, and to my brother in law Khalaf Ambusaidi. Your support meant a lot to me. Thanks. Acknowledgment I thank His Highness-the minister of the Ministry of Agriculture and Fisheries Resources Sheikh Muhammad bin Abdullah Al-Henaei, His Excellency Sheikh Abdullah Ba- Katheir-the director general of the Directorate General of Fisheries Resources, Thabit Zahran- the director of the Marine Science and Fisheries Center, and the staff of the Marine Science and Fisheries Center who helped in collecting the data during the survey, for sponsoring me, providing with the data, and for their support. Also, I thank the Omani American Joint Commission for in part sponsoring my scholarship. I am grateful to my advisor Dr. David Sampson for his assistance with the data analysis, and his constant availability when I was in need for his help academically and otherwise. Dr. Richard Tubb graciously helped me to get into the university and made me always feel at home. I am grateful to Dr. David McIntire who kindly spent most of his summer vacation helping me analyzing data using TWINSPAN and DECORANA. I thank the staff of the Hatfield Marine Science and Fisheries Center library Janet Webster, Susan Gilmont, and Liz Fox, for helping get the information required. Table of Contents Page Chapter 1. INTRODUCTION 1 Chapter 2. Distribution and Assemblages of the Demersal Fish Species 6 INTRODUCTION 6 General oceanography and seasonal patterns of Omani waters. 6 MATERIALS AND METHODS 10 Description of the data: 10 Analytical methods: 14 Classification of stations and species using TWINSPAN 15 Ordination using DCA and correlation with environmental factors 16 RESULTS IS Species Unique to Single Areas 18 Analysis of species assemblages 18 TWINSPAN Results by Season 19 TWINSPAN Results by Area 26 Community Structure Analysis Results: 35 Community Structure Analysis by Season: 35 Community Structure Analysis by Areas 43 DISCUSSIONS 53 CONCLUSIONS 55 Table of contents, continued Page Chapter 3. The Influence of Diurnal Variations and Distance from Untrawlable Ground on the Distribution of Commercial Fish Species in Omani Waters 56 INTRODUCTION 56 MATERIALS AND METHODS 57 RESULTS 59 DISCUSSIONS 76 CONCLUSIONS 81 BIBLIOGRAPHY 82 APPENDICES 86 List of Tables Page Table 1 The number of trawl stations by area and season 12 Table 2 Correlation coefficients of the environmental factors with the first and second ordination axes 37 Table 3 Correlation coefficients of the environmental factors with the first and second ordination axes 44 Table 4 Number of dominant species shared between areas 44 Table 5 The variables treated as factors with fixed number of levels in the analysis by GLM 58 Table 6 The number of stations conducted at depth, distance, season, and time of day in relation to areas 60 Table 7.a Significant factors in the generalized linear model for log-transformed catch rates 61 Table 7.b Significant factors in the generalized linear model for log-transformed catch rates 62 List of Appendices Appendix 1 List of species which were used in the analysis including their codes, and scientific and English names 87 Appendix 2 Stations which were deleted from the multivariate analyses 101 Appendix 3 TWINSPAN two-way tables for areas and seasons 104 List of Figures Figure Fig. 1 Map of the Sultanate of Oman 2 Fig. 2 Echogram distinguishing the untrawlable ground (rough), left side, with dense concentration of fish and the trawlable ground (smooth), right side, having less density of fish 4 Fig. 3 Sea surface temperature (2C) for the Omani coast covering the entire year based on data obtained prior to 1952 8 Fig. 4 Vertical profile of dissolved oxygen in the Gulf of Oman and sea surface salinity ( %o) 9 Fig. 5 Map of the Sultanate of Oman showing the regional areas by which the data were grouped 13 Fig. 6.1 Map showing groups derived from TWINSPAN results for the winter 1 season and a summary table showing for each group the dominant species, number of stations, and the average depth and distance from untrawlable ground in nautical mile (nm) 21 Fig. 6.2 Map showing groups derived from TWINSPAN results for the pre-monsoon season and a summary table showing for each group the dominant species, number of stations, and the average depth and distance from untrawlable ground 22 Fig. 6.3 Map showing groups derived from TWINSPAN results for the monsoon season and a summary table showing for each group the dominant species, number of stations, and the average depth and distance from untrawlable ground 23 Fig. 6.4 Map showing groups derived from TWINSPAN results for the post-monsoon season and a summary table showing for each group the dominant species, number of stations, and the average depth and distance from untrawlable ground 24 Fig. 6.5 Map showing groups derived from TWINSPAN results for the winter 2 season and a summary table showing for each group the dominant species, number of stations, and the average depth and distance from untrawlable ground 25 List of Figures, Continued Figure Page Fig. 7.1 Map showing groups derived from TWINSPAN results for area 1 (Musandam) and a summary table showing for each group the dominant species, number of stations, and the average depth and distance from untrawlable ground, and diversity index value 27 Fig. 7.2 Map showing groups derived from TWINSPAN results for area 2 (Batinah) and a summary table showing for each group the dominant species, number of stations, and the average depth and distance from untrawlable ground, and diversity index value 28 Fig. 7.3 Map showing groups derived from TWINSPAN results for area 3 (Sharquiah) and a summary table showing for each group the dominant species, number of stations, and the average depth and distance from untrawlable ground, and diversity index value 29 Fig. 7.4 Map showing groups derived from TWINSPAN results for area 4 (Jazer) and a summary table showing for each group the dominant species, number of stations, and the average depth and distance from untrawlable ground, and diversity index value 30 Fig. 7.5 Map showing groups derived from TWINSPAN results for area 1 (Masirah Bay) and a summary table showing for each group the dominant species, number of stations, and the average depth and distance from untrawlable ground, and diversity index value 31 Fig. 7.6 Map showing groups derived from TWINSPAN results for area 6 (Sawquirah Bay) and a summary table showing for each group the dominant species, number of stations, and the average depth and distance from untrawlable ground, and diversity index value 32 Fig. 7.7 Map showing groups derived from TWINSPAN results for area 7 (Halanyiat) and a summary table showing for each group the dominant species, number of stations, and the average depth and distance from untrawlable ground, and diversity index value 33 Fig. 7.8 Map showing groups derived from TWINSPAN results for area 8 (Salalah) and a summary table showing for each group the dominant species, number of stations, and the average depth and distance from untrawlable ground, and diversity index value 34 List of Figures, Continued Figure Tag Fig.