Screening of probiotics from indigenous Omani natural products for potential use in the aquaculture industry

Probiotics can enhance the growth performance and disease resistance of aquatic animals. Probiotics can influence digestive physiology through the secretion of exogenous digestive enzymes, facilitating the utilization of nutrients, and resulting in improvements in growth performance. The objectives of the present study were to reduce fish diseases, minimize the usage of antibiotics, and promote national policy on aquatic health management in Oman through enhancing immune stimulation mechanisms with probiotics from indigenous Omani products and finally to promote Oman’s aquaculture industry. Thirty-five kinds of edible products were screened. After the primary screening process, only 3 products contained appropriate amounts of probiotics, therefore the present study focused on 3 probiotics from Omani products, i.e., dried date, date vinegar, and camel milk. Gram staining, VITIK2, and DNA tests were used for the identification and characterization of bacterial strains. DNA sequence revealed that the bacteria isolated from dried dates were identified as Bacillus licheniformis. Those from date vinegar were identified as Bacillus vallismortis. A viability test with pepsin, pH 3 showed that the bacteria isolated from camel's milk (Bacillus stratospheric) had a greater tolerance at low pH followed by bacteria isolated from dried date (B. licheniformis). Thus, these can be used as a probiotic for aquatic organisms

Ectoparasite Fauna of Imported Ornamental Fishes in Oman

The movement of live aquatic animals crossing international borders is a regular activity for economic, social, and public resource development. A survey was carried out to investigate the prevalence of parasites translocated with imported ornamental fishes. Exotic diseases from imported fish have a potential hazard of biosecurity. A sample of 138 imported ornamental fish originating from Thailand and Sri Lanka were collected from pet shops around Muscat governorate and examined for ectoparasites. Parasitological examination was based on a visual macro and microscopic examination of fish’s exterior. The findings of the current survey of imported ornamental fish revealed that 50.72% of the imported ornamental fish were infected by the one or more of ectoparasites species including Ichthyophthirius multifiliis, Dactylogyrus sp., Gyrodactylus sp., digenean metacercaria and Trichodina sp. Parasitic infection of the gills (55.795) was higher than the skin (42.75%). The most prevalent parasite in skin infection was Gyrodactylus sp. (14.49%) but this was absent from the gills which was dominated by digenean metacercaria (26.08%). The existence of such parasitic organisms could pose a threat to native fish populations and the aquaculture sector. It is recommended that a risk analysis method based on the detection and assessment of fish diseases found in live ornamental fish be established and used. Also, exotic pathogenic parasites, as well as their hosts, must be closely monitored to reduce the likelihood of infections being introduced into new areas

Histological Examination of Various Organs of Asian Seabass, Lates calcarifer after an Oral Inactivated Vaccine against Vibrio harveyi

Disease outbreaks and consequential losses are a challenge to the aquaculture industry. Diseases in aquaculture are caused by pathogenic agencies, such as bacteria, viruses, and parasites. The use of vaccines is one approach for the control of infections in fish and in building immunity against them. The goal of the present study was to create an effective oral vaccination against V. harveyi in order to ensure the long-term viability of aquaculture operations in the Sultanate of Oman. At a commercial farm, the target bacterium was isolated from infected fish and identified from a pure strain. Bacteria were killed with formalin and cleaned with saline several times. The vaccine was mixed with commercial feed to provide an oral vaccination for fish. This vaccinated feed was given for four weeks, and the efficiency of vaccine was determined by a challenge test, which involved injecting live same species of bacteria into healthy fish. Histology samples were taken when the experiment was completed. Multivitamins and vaccination therapy helped the fish to develop faster and to survive for extended periods of time without any organ damages. The control fish, on the other hand, demonstrated an incapacity to resist bacteria and died as a result, with external and internal organ damage. Despite the positive findings of this study, more research is required

Gill monogenean communities on three commercially important sparid fish in Omani waters

The prevalence and intensity of polyopisthocotylean monogeneans on the gills of three commercially important species of sparid caught in Omani coastal waters close to the city port of Muscat were determined and compared. Throughout May 2012 to April 2013, infections on bi-weekly samples of the soldier seabream, Argyrops filamentosus (Valenciennes, 1830), the king soldier seabream, Argyrops spinifer (Forsskål, 1775), and, the silver seabream, Rhabdosargus sabra were evaluated. From a total of 200 specimens (standard length of 26–52 cm), caught by line angling or by traps, at least three species of gill monogenean, namely Omanicotyle [Bivagina] heterospina, Heteromicrocotyla sp. and Microcotyle sp., were commonly encountered. Silver bream, which was infected by all three monogeneans, bore the highest infections (100% prevalence; mean intensity of 20.14 ± 0.92 parasites fish-1), whilst the soldier bream, which was infected only by O. heterospina had the lowest levels of infection (of the three sparids with 63.8% prevalence; mean intensity 5.8 ± 0.17 parasites fish-1). Comments on the distribution of monogeneans on each host are provided but to what extent this is influenced by water current speeds passing through the buccal and opercular cavities, gill morphology, parasite size, and / or the morphology and efficiency of the parasite’s attachment apparatus requires establishing and forms the basis of ongoing investigations

Gill monogenean communities on three commercially important sparid fish in Omani waters

The prevalence and intensity of polyopisthocotylean monogeneans on the gills of three commercially important species of sparid caught in Omani coastal waters close to the city port of Muscat were determined and compared. Throughout May 2012 to April 2013, infections on bi-weekly samples of the soldier seabream, Argyrops filamentosus (Valenciennes, 1830), the king soldier seabream, Argyrops spinifer (Forsskål, 1775), and, the silver seabream, Rhabdosargus sabra were evaluated. From a total of 200 specimens (standard length of 26–52 cm), caught by line angling or by traps, at least three species of gill monogenean, namely Omanicotyle [Bivagina] heterospina, Heteromicrocotyla sp. and Microcotyle sp., were commonly encountered. Silver bream, which was infected by all three monogeneans, bore the highest infections (100% prevalence; mean intensity of 20.14 ± 0.92 parasites fish-1), whilst the soldier bream, which was infected only by O. heterospina had the lowest levels of infection (of the three sparids with 63.8% prevalence; mean intensity 5.8 ± 0.17 parasites fish-1). Comments on the distribution of monogeneans on each host are provided but to what extent this is influenced by water current speeds passing through the buccal and opercular cavities, gill morphology, parasite size, and / or the morphology and efficiency of the parasite’s attachment apparatus requires establishing and forms the basis of ongoing investigations.

Gill histology of Nile tilapia Oreochromis niloticus following chronic and acute exposure to ammonia

Ammonia is a common aquatic pollutant and is toxic to fish. The main nitrogenous compound excreted by fish is also ammonia, which may reach toxic concentrations in high-density fish culture, reducing growth and productivity. In this study, changes in gill structure and mucus cell distribution were examined when juvenile Nile tilapia, Oreochromis niloticus, were exposed to chronic and acute concentrations of ammonia. For chronic exposure, the tilapia were exposed to daily increments in ammonia concentration rising from 0 mg L-1 ammonia on Day 0 to 5 mg L-1 by Day 8; the experiment was terminated on Day 9. There were obvious histopathological changes to the gills over this period including hypertrophy and fusion and of the secondary lamellae. The mucus cell number in gill histology sections were observed to increase until Day 6 then decrease thereafter until the termination of the trial. For the acute exposure, juvenile tilapia were exposed to 5 mg L-1 ammonia for 5 hours. Hourly changes to the gills were monitored, with notable changes to gill filaments and an observed increase in the mucus cell number over the duration of the experiment.

Gill histology of Nile tilapia Oreochromis niloticus following chronic and acute exposure to ammonia

Ammonia is a common aquatic pollutant and is toxic to fish. The main nitrogenous compound excreted by fish is also ammonia, which may reach toxic concentrations in high-density fish culture, reducing growth and productivity. In this study, changes in gill structure and mucus cell distribution were examined when juvenile Nile tilapia, Oreochromis niloticus, were exposed to chronic and acute concentrations of ammonia. For chronic exposure, the tilapia were exposed to daily increments in ammonia concentration rising from 0 mg L-1 ammonia on Day 0 to 5 mg L-1 by Day 8; the experiment was terminated on Day 9. There were obvious histopathological changes to the gills over this period including hypertrophy and fusion and of the secondary lamellae. The mucus cell number in gill histology sections were observed to increase until Day 6 then decrease thereafter until the termination of the trial. For the acute exposure, juvenile tilapia were exposed to 5 mg L-1 ammonia for 5 hours. Hourly changes to the gills were monitored, with notable changes to gill filaments and an observed increase in the mucus cell number over the duration of the experiment

Gill histology of Nile tilapia Oreochromis niloticus following chronic and acute exposure to ammonia

Ammonia is a common aquatic pollutant and is toxic to fish. The main nitrogenous compound excreted by fish is also ammonia, which may reach toxic concentrations in high-density fish culture, reducing growth and productivity. In this study, changes in gill structure and mucus cell distribution were examined when juvenile Nile tilapia, Oreochromis niloticus, were exposed to chronic and acute concentrations of ammonia. For chronic exposure, the tilapia were exposed to daily increments in ammonia concentration rising from 0 mg L-1 ammonia on Day 0 to 5 mg L-1 by Day 8; the experiment was terminated on Day 9. There were obvious histopathological changes to the gills over this period including hypertrophy and fusion and of the secondary lamellae. The mucus cell number in gill histology sections were observed to increase until Day 6 then decrease thereafter until the termination of the trial. For the acute exposure, juvenile tilapia were exposed to 5 mg L-1 ammonia for 5 hours. Hourly changes to the gills were monitored, with notable changes to gill filaments and an observed increase in the mucus cell number over the duration of the experiment

Gill monogenean communities on three commercially important sparid fish in Omani waters

The prevalence and intensity of polyopisthocotylean monogeneans on the gills of three commercially important species of sparid caught in Omani coastal waters close to the city port of Muscat were determined and compared. Throughout May 2012 to April 2013, infections on bi-weekly samples of the soldier seabream, Argyrops filamentosus (Valenciennes, 1830), the king soldier seabream, Argyrops spinifer (Forsskål, 1775), and, the silver seabream, Rhabdosargus sabra were evaluated. From a total of 200 specimens (standard length of 26–52 cm), caught by line angling or by traps, at least three species of gill monogenean, namely Omanicotyle [Bivagina] heterospina, Heteromicrocotyla sp. and Microcotyle sp., were commonly encountered. Silver bream, which was infected by all three monogeneans, bore the highest infections (100% prevalence; mean intensity of 20.14 ± 0.92 parasites fish-1), whilst the soldier bream, which was infected only by O. heterospina had the lowest levels of infection (of the three sparids with 63.8% prevalence; mean intensity 5.8 ± 0.17 parasites fish-1). Comments on the distribution of monogeneans on each host are provided but to what extent this is influenced by water current speeds passing through the buccal and opercular cavities, gill morphology, parasite size, and / or the morphology and efficiency of the parasite’s attachment apparatus requires establishing and forms the basis of ongoing investigations

Gill monogenean communities on three commercially important sparid fish in Omani waters

The prevalence and intensity of polyopisthocotylean monogeneans on the gills of three commercially important species of sparid caught in Omani coastal waters close to the city port of Muscat were determined and compared. Throughout May 2012 to April 2013, infections on bi-weekly samples of the soldier seabream, Argyrops filamentosus (Valenciennes, 1830), the king soldier seabream, Argyrops spinifer (Forsskål, 1775), and, the silver seabream, Rhabdosargus sabra were evaluated. From a total of 200 specimens (standard length of 26–52 cm), caught by line angling or by traps, at least three species of gill monogenean, namely Omanicotyle [Bivagina] heterospina, Heteromicrocotyla sp. and Microcotyle sp., were commonly encountered. Silver bream, which was infected by all three monogeneans, bore the highest infections (100% prevalence; mean intensity of 20.14 ± 0.92 parasites fish-1), whilst the soldier bream, which was infected only by O. heterospina had the lowest levels of infection (of the three sparids with 63.8% prevalence; mean intensity 5.8 ± 0.17 parasites fish-1). Comments on the distribution of monogeneans on each host are provided but to what extent this is influenced by water current speeds passing through the buccal and opercular cavities, gill morphology, parasite size, and / or the morphology and efficiency of the parasite’s attachment apparatus requires establishing and forms the basis of ongoing investigations.