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- Diversity, distribution, and density of marine mammals along the Saudi waters of the Arabian Gulf: update from a multi-method approachPublication . Rabaoui, Lotfi; Roa-Ureta, Ruben; Yacoubi, Lamia; Lin, Yu-Jia; Maneja, Rommel; Joydas, Thadickal V.; Panickan, Premlal; Gopalan, Jinoy; Loughland, Ronald; Prihartato, Perdana K.; Qassem, Ali; Hikmawan, Tyas I.; Diaz Lopez, Bruno; Qurban, Mohammed A.Despite the important role of marine mammals in marine ecosystems and the imperative for their conservation, there is still a great lack of information on the diversity, distribution, and density of these animals in the Saudi waters of the Arabian Gulf. To fill this gap, an integrative data-collection approach including fishermen’s questionnaires, opportunistic sighting reports, and directed boat-based surveys, was undertaken between 2016 and 2020, leading to the first scientific report of marine mammal diversity, distribution, and density in the region. The results of the different approaches carried out during the study confirmed a high diversity of cetaceans on the west coast of the study area, with bottlenose dolphins (Tursiops aduncus), humpback dolphins (Sousa plumbea) and dugongs (Dugong dugon) as the most common species. While the two dolphin species were found to be widely distributed in both coastal and offshore waters, D. dugon appears to occur exclusively in coastal waters in the southern part of the study area, mainly in the Gulf of Salwah. The presence of both species of dolphins increased during the summer months and in the vicinity of the numerous oil and gas facilities in this region. The distribution of the observed dolphins was found mostly within a 10–20 km radius around each facility. Other cetacean species observed less frequently in the area include Bryde’s whale (Balaenoptera edeni), killer whale (Orcinus orca), common dolphin (Delphinus delphis) and finless porpoise (Neophocaena phocaenoides). Regarding the density of marine mammals in the region, boat-based surveys confirmed the results of fishermen’s questionnaires and reports of opportunistic sightings, with bottlenose and humpback dolphins being the most abundant species. These results provide a baseline for policies oriented to the conservation of mammals in the Saudi waters of the Arabian Gulf.
- Ecology, life history, and fisheries potential of the flathead lobster (Thenus orientalis) in the Arabian GulfPublication . Rabaoui, Lotfi; Yacoubi, Lamia; Lin, Yu-Jia; Joydas, Thadickal V.; Qurban, Mohammad A.; Premlal, Panickan; Gopalan, Jinoy; Nazeer, Zahid; Vijayakumaran, Manambrakat; Khan, Syed Ajmal; Roa-Ureta, RubenThis study, which included examination of the distribution and life history and a stock assessment of the flathead lobster (Thenus orientalis), is the first of its kind in the waters of Saudi Arabia in the Arabian Gulf, also known as the Persian Gulf. The flathead lobster is widely distributed in this region, although it is more abundant in the central and northern Arabian Gulf. Carapace lengths at 50% and 95% maturity are 59 and 65 mm for females and 58 and 71 mm for males. The fecundity of 4 berried females ranged from 26,000 to 76,000 eggs per spawning, and the fertilization rate exceeded 97%. Length-frequency data were consistent with just 2 cohorts, indicating that this species has a short life span and high growth coefficient (K=0.846 year(-1)). Large fishing boats (called dhows) accounted for more than 98% of the total landings. Estimates of natural mortality rates from use of generalized depletion models have high statistical precision and a magnitude compatible with short life history. In addition, abundance levels estimated with the depletion model are sufficient to support a sustainable small-scale fishery either as bycatch of shrimp trawlers or as a resource targeted with specialized gear. A targeted fishery for flathead lobster could be set during the off months of the shrimp trawl fishery (February-July), reducing interference with the reproduction cycle.
- Habitat-forming organisms in the offshore seabed of the western Arabian GulfPublication . Lin, Yu-Jia; Roa-Ureta, Ruben; Premlal, Panickan; Nazeer, Zahid; Pulikkoden, Abdu Rahiman Kambrath; Qurban, Mohammad A.; Prihartato, Perdana K.; Alghamdi, Hamed A.; Qasem, Ali M.; Rabaoui, LotfiSome macro-benthic organisms, such as macroalgae, bryozoans, sponges, and gorgonian corals, can create heterogeneous frameworks of habitats in the surrounding seabed. Such frameworks are important benthic ecosystems, but knowledge of them is fairly limited in the Arabian Gulf, the hottest sea in the world. In this study, the presence of macroalgae, bryozoans, sponges, and gorgonian corals was discovered in the seabed of the western Arabian Gulf. These organisms had positive co-occurrences with a preference for depths of 20 to 50 m. A hotspot of spatial distribution of macroalgae and bryozoans was also identified, located in the northwestern part of the Arabian Gulf. These habitat forming organisms were distributed in a patchy pattern with low to moderate levels of density. They were positively associated with several commercial fishes, suggesting their importance to fishery. Our discovery extends the distribution of marine habitat-forming organisms into the offshore waters of the subtropical Arabian Gulf.
- Strengths and weaknesses in the long-term sustainability of two sympatric seabreams (Argyrops spinifer and Rhabdosargus haffara, Sparidae)Publication . Lin, Yu-Jia; Rabaoui, Lotfi; Maneja, Rommel H.; Pulikkoden, Abdu Rahiman Kambrath; Premlal, Panickan; Nazeer, Zahid; Qurban, Mohammad A.; Abdulkader, Khaled; Prihartato, Perdana K.; Qasem, Ali M.; Fita, Nabil; Roa-Ureta, RubenArgyrops spinifer and Rhabdosargus haffara are two sympatric seabream species making important contributions to fisheries landings in the western Arabian/Persian Gulf. We identified the strengths and weaknesses in the long-term sustainability of A. spinifer and R. haffara stocks by integrating multiple sources of data, including fisheries catch and effort statistics, life history traits, scientific trawl surveys and historical length frequency distribution. Four strengths were identified in A. spinifer: wide distribution of juveniles, positive association to the network of de facto fishing exclusion areas created by hundreds of oil-gas facilities, early maturation and the existence of large and old individuals. A. spinifer suffers from two potential weaknesses: slow growth rate and higher exploitation pressure on the small-sized individuals. R. haffara, on the other hand, has a strength of having a short life span and a fast growth rate, characteristics that make it robust to unfavourable conditions. R. haffara suffers from two weaknesses: the lack of association to the oil and gas facilities, and the preference for nearshore shallow waters with stronger negative anthropogenic impacts. Identified strengths and weaknesses of these two sparids provided a preliminary assessment about their long-term sustainability, as well as a roadmap about how to develop different management strategies to meet specific objectives.
- Essential fish habitats of demersal fish in the western Arabian GulfPublication . Lin, Yu-Jia; Roa-Ureta, Ruben; Pulikkoden, Abdu Rahiman Kambrath; Premlal, Panickan; Nazeer, Zahid; Qurban, Mohammad A.; Rabaoui, LotfiInformation about habitats occupied by aquatic organisms while completing critical stages of their lives, called essential fish habitats, is crucial for their sustainability. In this work, we determine essential fish habitats (nursery and spawning grounds) of several fish species inhabiting Saudi territorial waters in the western Arabian Gulf using data from multiple surveys (2013-2016), geostatistics, and indicator species analysis. We built geostatistical maps of spatial distributions of juvenile and mature fish and examined the strength of association of each species to its observed nursery and spawning areas. Fish nursery areas were generally located in nearshore locations while spawning areas were located in offshore waters. The patterns of nursery and spawning grounds were highly varied among species, supporting a hypothesis of habitat-species heterogeneity: different species use different locations as nursery and spawning grounds. This information can be used as a roadmap for future evidence-based spatial planning and ecosystem-based management.
- Coarser taxonomic resolutions are informative in revealing fish community abundance trends for the world’s warmest coral reefsPublication . Lin, Yu-Jia; Roa-Ureta, Ruben; Basali, Abdullajid Usama; Alcaria, Joselito Francis Albaran; Lindo, Reynaldo; Qurban, Mohammad A.; Prihartato, Perdana K.; Qasem, Ali; Rabaoui, LotfiThe Arabian Gulf is a natural laboratory to examine how subtropical coral reef ecosystems might change in responding to recurring heating events because of uniquely high water temperature and relatively low fish diversity. Several statistical methods were applied to long-term (30 yrs) monitoring data in the western Arabian Gulf to extract clean signals of the fish abundances, to reveal common trends in the multivariate time series, and to test for nonlinear and lagged effects of coral coverage and sea surface temperature as predictors. Data were analyzed at three taxonomic resolutions: species (29 species out of a total of 148 species, contributing to 69% of total observations), genus (24 genera, 81%), and family (19 families, 96%), to test the taxonomic sufficiency hypothesis, which asserts that there is no significant loss of information at higher taxonomic levels for detecting changes in the fish assemblages. Multivariate abundance time series can be summarized by dynamic factor models of four common trends, which were supported by time series clustering and good model fitting performances. The taxonomic sufficiency hypothesis is supported for the first two common trends, which showed similarity among the three taxonomic resolutions. The effects of changes in coral coverage on the fish community are nonlinear and significantly lagged with lags mostly of 8 yrs, while the effects of mean sea surface temperature were significant but inconclusive. The fish communities in the coral reefs of the western Arabian Gulf are degrading in general with decreasing abundance at the three taxonomic resolutions. Analyzing data at coarser taxonomic resolutions can be informative in revealing the general trends of the abundance of coral reef fish communities, at the cost of ignoring variations at finer resolutions. This study further highlights the importance of long-term and continuous monitoring of the coral reef ecosystem at the finest possible taxonomic level to fully reveal slow but crucial changes in fish communities, as well as to detect signs of communities' degradation to take timely restoration actions.
- Distribution, abundance, and life history traits of the blue swimming crab Portunus segnis (Forskål, 1775) in the Saudi waters of the Arabian GulfPublication . Rabaoui, Lotfi; Yacoubi, Lamia; Lin, Yu-Jia; Joydas, Thadickal V.; Maneja, Rommel H.; Dagoy, Joshua; Qurban, Mohammad A.; Roa-Ureta, RubenThe blue swimming crab, Portunus segnis (Forskal, 1775), formerly known as P. pelagicus (Linnaeus, 1758) has become a major fishery resource in the Gulf. Yet, there are no regional studies on the stock population dynamics and life history processes of this species. Considering the extreme oceanographic features of the Gulf (high salinity and high temperature variations), which is hypothesized to cause fast growth of P. segnis, a study was conducted to determine the abundance/biomass distribution of its stocks, growth rates, and sexual maturation in the territorial Saudi waters in the Arabian Gulf. The study was based on trawling surveys, landing sites monitoring, and records of fisheries catch and efforts and juvenile habitat surveys. The spatial distribution patterns supported by generalized linear model indicated the occurrence of P. segnis in the nearshore shallow waters, and its absence from the offshore deeper waters, attributed to the variability of environmental conditions including salinity, temperature, and trophic resources. Manifa, one of the productive areas in the northern Saudi waters of the Gulf, had high abundance of the crab. In agreement with the hypothesis, the growth rate of the Saudi P. segnis was found to be the higher (2.12 K year(-1)) compared to other parts of the Gulf (1.1-1.7 K year(-1)) or other sea areas of tropical regions (0.95-1.68 K year(-1)). The study shows that P. segnis can spawn throughout the year, with at least three peaks: winter, late spring-early summer, and autumn. The L-50% record obtained in this study with females (127 mm) and males (125 mm) are larger than those reported with the same species from other parts of the Gulf (113 mm) or with other congeneric blue species crabs reported from other tropical regions (61-113 mm). The present study provided basic data to develop a management strategy for the fishery of P. segnis in the region. (c) 2021 Elsevier B.V. All rights reserved.
- A comparison of three data-poor stock assessment methods for the pink spiny lobster fishery in MauritaniaPublication . Meissa, Beyah; Dia, Mamadou; Baye, Braham C.; Bouzouma, Moustapha; Beibou, Ely; Roa-Ureta, RubenSeveral data-poor stock assessment methods have recently been proposed and applied to data-poor fisheries around the world. The Mauritanian pink spiny lobster fishery has a long history of boom and bust dynamics, with large landings, stock collapse, and years-long fishery closures, all happening several times. In this study, we have used catch, fishing efforts, and length-frequency data (LFD) obtained from the fishery in its most recent period of activity, 2015–2019, and historical annual catch records starting in 2006 to fit three data-poor stock assessment methods. These were the length-based Bayesian (LBB) method, which uses LFD exclusively, the Catch-only MSY (CMSY) method, using annual catch data and assumptions about stock resilience, and generalised depletion models in the R package CatDyn combined with Pella-Tomlinson biomass dynamics in a hierarchical inference framework. All threemethods presented the stock as overfished. The LBB method produced results that were very pessimistic about stock status but whose reliability was affected by non-constant recruitment. The CMSY method and the hierarchical combination of depletion and Pella-Tomlinson biomass dynamics produced more comparable results, such as similar sustainable harvest rates, but both were affected by large statistical uncertainty. Pella-Tomlinson dynamics in particular demonstrated stock experiencing wide fluctuations in abundance. In spite of uncertain estimates, a clear understanding of the status of the stock as overfished and in need of a biomass rebuilding program emerged as management-useful guidance to steer exploitation of this economically significant resource into sustainability.