Date of Defense
8-4-2025 11:00 AM
Location
F3-022
Document Type
Dissertation Defense
Degree Name
Doctor of Philosophy in Cellular and Molecular Biology
College
COS
Department
Biology
First Advisor
Prof. Sabir Bin Muzaffar
Keywords
Narrow-barred Spanish mackerels, Pelagic fish, Arabian Gulf, Persian Gulf, Foraging habits, Forage fish, diet, DNA barcoding, Phylogenetics, Heavy metals, Bioaccumulation, Biomagnification, Population genomics, ddRAD sequencing, Population structure
Abstract
Marine organisms are integral part of marine ecosystems, forming complex feeding interactions. Large predatory fish are especially important because they often govern food web structures through top-down influences. The narrow-barred Spanish mackerel (Scomberomorus commerson) is an ecologically and economically important fish species that feeds on small forage fish. The current study focuses on three aspects of the narrow-barred Spanish mackerel (diet, bioaccumulation of heavy metals and population genomics). This species is considered near-threatened, as its population has been declining due to anthropogenic stressors. The Arabian Gulf experiences continuous natural stressors, which are further exacerbated by human activities, impacting the marine ecosystem. The narrow-barred Spanish mackerel is an ecologically and economically valuable fish that remains less investigated. To assess the diet of S. commerson collected from two distant locations inside the Arabian Gulf (UAE and Iran), two different approaches were used: 1.) The gastrointestinal tract was physically inspected to identify various semi-intact prey species. 2.) DNA barcoding and phylogenetics, based on 16s rRNA, were employed to identify fish prey taxa. Based on both morphological and DNA barcoding analysis, the semi-intact prey species in the gastrointestinal tract consistently identified the primary prey as sardines (Sardinella spp.) and scads (Decapterus spp.). All the narrow-barred Spanish mackerel specimens sampled from both sites in the Gulf showed poor body condition based on the Fulton’s body index. Further research is required to understand the diet of the narrow-barred Spanish mackerel. Anthropogenic activities have increased the discharge of marine contaminants, threatening marine life. Small gulfs, such as the Arabian Gulf, are vulnerable to accumulating potentially toxic elements in marine species due to slow water exchange. The concentration of 21 elements was determined in the tissues of Scomberomorus commerson from Umm Al Quwain (United Arab Emirates) and Bandar Abbas (Iran). Chromium, copper, and iron exceeded internationally established maximum permissible limits. Sites could not be distinguished based on Principal Component Analyses of elements. Elevated Cu and Cr in muscle are of concern to marine species as well as humans. The Metal Pollution Index showed a significant difference between sites, with 20.34% and 100% of individuals suffering from high metal toxicity and poor body conditions, respectively. The Arabian Gulf is experiencing an increase in the discharge of industrial wastes. Implementation of strict policies to reduce the discharge of toxic substances is required to protect marine organisms and humans. Conservation of wildlife populations requires a thorough understanding of population structure and gene flow. Usually, when sampling is conducted for ecological studies, it is assumed that specimens are collected from one population. However, the obtained samples might be collected from more than one population, making it difficult to guide wildlife management with uncertainty regarding individuals from distinct populations. The Arabian Gulf is considered a living laboratory as it supports several coastal and marine ecosystems and is home to a wide range of fish species. However, the lack of genetic data, especially for fish populations, raises taxonomic uncertainty. Therefore, this study used advanced genomic tools to resolve these uncertainties by assessing the population structure, gene flow, and dispersal of the narrow-barred Spanish mackerel from the Arabian Gulf. The ddRAD sequencing, quality check-filtering of sequences, and analysis through genetic software reported that the narrow-barred Spanish mackerel collected from the eastern Arabian Gulf is a panmictic population with significantly low FST values. This study emphasizes the need for conservation, sustainable fisheries management, and stricter pollution control to ensure the long-term stability of the narrow-barred Spanish mackerel population in the Arabian Gulf ecosystem.
Included in
DIET, BIOACCUMULATION OF HEAVY METALS, AND POPULATION GENOMICS OF NARROW-BARRED SPANISH MACKEREL (SCOMBEROMORUS COMMERSON) FROM THE ARABIAN GULF
F3-022
Marine organisms are integral part of marine ecosystems, forming complex feeding interactions. Large predatory fish are especially important because they often govern food web structures through top-down influences. The narrow-barred Spanish mackerel (Scomberomorus commerson) is an ecologically and economically important fish species that feeds on small forage fish. The current study focuses on three aspects of the narrow-barred Spanish mackerel (diet, bioaccumulation of heavy metals and population genomics). This species is considered near-threatened, as its population has been declining due to anthropogenic stressors. The Arabian Gulf experiences continuous natural stressors, which are further exacerbated by human activities, impacting the marine ecosystem. The narrow-barred Spanish mackerel is an ecologically and economically valuable fish that remains less investigated. To assess the diet of S. commerson collected from two distant locations inside the Arabian Gulf (UAE and Iran), two different approaches were used: 1.) The gastrointestinal tract was physically inspected to identify various semi-intact prey species. 2.) DNA barcoding and phylogenetics, based on 16s rRNA, were employed to identify fish prey taxa. Based on both morphological and DNA barcoding analysis, the semi-intact prey species in the gastrointestinal tract consistently identified the primary prey as sardines (Sardinella spp.) and scads (Decapterus spp.). All the narrow-barred Spanish mackerel specimens sampled from both sites in the Gulf showed poor body condition based on the Fulton’s body index. Further research is required to understand the diet of the narrow-barred Spanish mackerel. Anthropogenic activities have increased the discharge of marine contaminants, threatening marine life. Small gulfs, such as the Arabian Gulf, are vulnerable to accumulating potentially toxic elements in marine species due to slow water exchange. The concentration of 21 elements was determined in the tissues of Scomberomorus commerson from Umm Al Quwain (United Arab Emirates) and Bandar Abbas (Iran). Chromium, copper, and iron exceeded internationally established maximum permissible limits. Sites could not be distinguished based on Principal Component Analyses of elements. Elevated Cu and Cr in muscle are of concern to marine species as well as humans. The Metal Pollution Index showed a significant difference between sites, with 20.34% and 100% of individuals suffering from high metal toxicity and poor body conditions, respectively. The Arabian Gulf is experiencing an increase in the discharge of industrial wastes. Implementation of strict policies to reduce the discharge of toxic substances is required to protect marine organisms and humans. Conservation of wildlife populations requires a thorough understanding of population structure and gene flow. Usually, when sampling is conducted for ecological studies, it is assumed that specimens are collected from one population. However, the obtained samples might be collected from more than one population, making it difficult to guide wildlife management with uncertainty regarding individuals from distinct populations. The Arabian Gulf is considered a living laboratory as it supports several coastal and marine ecosystems and is home to a wide range of fish species. However, the lack of genetic data, especially for fish populations, raises taxonomic uncertainty. Therefore, this study used advanced genomic tools to resolve these uncertainties by assessing the population structure, gene flow, and dispersal of the narrow-barred Spanish mackerel from the Arabian Gulf. The ddRAD sequencing, quality check-filtering of sequences, and analysis through genetic software reported that the narrow-barred Spanish mackerel collected from the eastern Arabian Gulf is a panmictic population with significantly low FST values. This study emphasizes the need for conservation, sustainable fisheries management, and stricter pollution control to ensure the long-term stability of the narrow-barred Spanish mackerel population in the Arabian Gulf ecosystem.