Methylmercury bioaccumulation in sport fish and the relation to human exposure

A long-lasting contaminant, methylmercury (MeHg), builds up in human bodies over a lifetime. Regularly eating contaminated fish may accumulate mercury to an amount that raises health concerns, especially for children and babies. Methylmercury is found throughout the parts of the fish that are eaten; cleaning or cooking methods cannot effectively reduce mercury exposure. The main focus of this thesis concerns the fish contamination in Lake Ontario and to conserve health from eating contaminated sport fish. Although mercury (Hg) is tightly regulated, mercury levels in fish still gradually increase throughout their life spans. Through the field data provided by the Ontario Ministry of Environment (MOE), greater amounts of methylmercury are found in older fish and predatory fish that eat other fish as part of their diet. A bioenergetics computer program, called Generic Bioaccumulation Model (BGM) (Luk, 1996), simulating the bioaccumulation of Hg in fish was applied to provide a good estimation of mercury levels for different species. It is an excellent tool in predicting the trends and magnitude of mercury levels among six sport fish in Lake Ontario. In addition, an estimation of human mercury consumption from fish was also developed. In most of the fish species, there is minimal risk to humans when eating fish less than two times a week. The species Walleye (Stizostedion vitreum) and its quality and quantity are of greatest concern, since it exhibits the highest mercury level among the six sport fish species.

Methylmercury bioaccumulation in sport fish and the relation to human exposure

A long-lasting contaminant, methylmercury (MeHg), builds up in human bodies over a lifetime. Regularly eating contaminated fish may accumulate mercury to an amount that raises health concerns, especially for children and babies. Methylmercury is found throughout the parts of the fish that are eaten; cleaning or cooking methods cannot effectively reduce mercury exposure. The main focus of this thesis concerns the fish contamination in Lake Ontario and to conserve health from eating contaminated sport fish. Although mercury (Hg) is tightly regulated, mercury levels in fish still gradually increase throughout their life spans. Through the field data provided by the Ontario Ministry of Environment (MOE), greater amounts of methylmercury are found in older fish and predatory fish that eat other fish as part of their diet. A bioenergetics computer program, called Generic Bioaccumulation Model (BGM) (Luk, 1996), simulating the bioaccumulation of Hg in fish was applied to provide a good estimation of mercury levels for different species. It is an excellent tool in predicting the trends and magnitude of mercury levels among six sport fish in Lake Ontario. In addition, an estimation of human mercury consumption from fish was also developed. In most of the fish species, there is minimal risk to humans when eating fish less than two times a week. The species Walleye (Stizostedion vitreum) and its quality and quantity are of greatest concern, since it exhibits the highest mercury level among the six sport fish species.

Sources of Fungal Contamination of Fresh and Dried Fish in Kisii County, Kenya

Aflatoxins are toxic secondary metabolites produced by Aspergillus flavus and Aspergillus parasiticus that frequently invade foods and feedstuffs. In humid climatic conditions like those found in Kisii County, growth of fungi on dried fish and fish feeds is accelerated due to absorption of moisture from the environment as a result of poor storage and sometimes improper drying. This can lead to creation of favourable conditions for the growth of the toxigenic fungi and consequently production of aflatoxins. This study was conducted to determine the main sources of fungal contamination of selected fresh and dried fish sold in Kisii county, Kenya. Samples of fish were randomly obtained from four main markets in the county. A structured questionnaire was used to determine the sources of fish, mode and hygiene of transportation, handling of fish, duration of storage, hygiene of packaging materials and display environment of fish. Levels of fish contamination were expressed in form of colony forming units per gram (CFU/g) of fish. One-way analysis of variance was used to determine mean differences in parameters analysed. The results revealed that CFU/g of fish from control samples were significantly less than those from fresh and dried fish samples from the various sources (p<0.05). There was generally no significant difference between CFU/g from both fresh and dried fish from the various sources. The study found out that fresh and dried fish sold in Kisii county are contaminated with fungi. There is therefore need for frequent surveillance on the sources of fish contamination and public sensitization of all those involved in fish supply chain. This will help reduce possible aflatoxin contamination thus promoting consumers’ healthy living.

Seasonal dynamics of carp infection with Bothriocephalus sp. in cage farming under the new conditions

The purpose of the research: is studying the seasonal dynamics of carp infection with Bothriocephalus sp. in cage farming under the new conditions (no discharge into the reservoir-cooler of warm water, wintering in cages under the ice). Materials and methods. To study the dynamics of contamination of carp yearlings with Bothriocephalus sp. In JSC Cherepetskaya fish farm is chosen 4 cage with fingerlings of carp. Monthly, from April to November 2017, the helminthological autopsy carried out on 10 yearlings carp from each tank to establish the extensiveness and intensity of infection of fish with Bothriocephalus sp. The content of soluble oxygen in water and measured the water temperature in the zone of location of the garden lines determined daily. After carrying out preventive treatments with microsal fish from all experimental cages were opened and the effectiveness of treatment was determined. Results and discussion. Carp are infected with Bothriocephalus sp. in April at 30-50%, in May there was a slight increase of the infection (40- 50%). After the first treatment with feed drug mixtures with microsal, a significant decrease in the infection of the fish with Bothriocephalus sp. occurred. In three cages 100% efficiency was obtained. In the cage No 21, the effectiveness of treatment was 75,0%. In June 2017, in the No. 21 cage, fish contamination increased till 20%. In the remaining three experimental cages, the fish did not infected. At the end of July, there was a sharp increase in the extensiveness and intensity of infection of fish by Bothriocephalus sp. - from 10 to 40% at an invasive rate from 1 to 2,25 cestodes per fish. In August, the extent of infection continued to grow and amounted to 30-60% for different experimental cages, the intensity of infection remained at the same level. On September 18, 2017, after the second treatment of fish with the therapeutic granulated mixed fodder with microsal, efficiency in cages No 5, No. 25 and No 36 was 100%. In the cage No 21, efficiency was 83,3%. In October and November 2017 there was an insignificant increase in fish infection by cestodes. The incidence of infection in October was 10% in the cage No 21, 20% and 10% in the cages 21 and 36 respectively. In the remaining experimental cages, the infection of fish with Bothriocephalus sp. is not established.

Examine the contamination of Epinephelus coioides with Listeria and Salmonella bacteria in Khuzestan coastal zone

Listeria and Salmonella species are high risk for human through contaminated foods; these bacteria are psychrophilic and could grow at low temperature even at refrigerator. Fish and shrimp and other aquatic organisms are very good resources for these kinds of bacteria. These bacteria are known as food-borne bacteria because infected of human by foods. These bacteria have been isolated from fresh and processing aquatic foods in the most countries. In this research, two different organs including intestines and gills from each fish were prepared at sterile condition for isolation of salmonella and Listeria. Listeria was indentified according to FDA and also salmonella was characterized according to impedance method. From total examined 60 fish, 18 fish was contaminated to salmonella and 3 fish was contaminated to Listeria respectively. The frequency of Salmonella and Listeria in Mahshahr fish was 0.30 and 0.05 and in Hendijan fish contamination with salmonella was 0.05 and contamination with Listeria was not reported. S. paratyphi, S. typhimurium B and S. cholera-suis C were identified in Mahshahr fish, but in Hendijan, fish was characterized S. paratyphi and S. typhimurium B. L. murrayi was only isolated specie from Mahshahr fish. These two pathogenic bacteria have contaminated Khuzestan coastal zone through human resources, animal waste, waste water and chemical industries. Therefore people receive these kind bacteria through consumption of aquatic contaminated marine foods.

Variability in the Structure of Planktonic Microalgae Assemblages in Water Column Associated withPosidonia oceanica(L.) Bed in Tunisia

Patterns of phytoplankton in areas with seagrass (Posidonia oceanica) and areas without seagrass were quantified in the coast of Chebba (East of Tunisia). Replicate samples were collected at August 2011, from four stations (separated by 500 of metres). The diversity of phytoplankton was high aroundP. oceanicameadows compared to area without seagrass. A possible explanation to this finding is that water motion and hydrodynamics forces cause leaves agitation allowing the passage of epiphytic species in the water column. Our results also show an increase of abundance of potentially toxic dinoflagellates aroundPosidoniabed such asAlexandrium minitum,Amphidinium carterae,Karenia selliformis,Coolia monatis,Karlodinium veneficum,Ostreopsis ovata,Prorocentrum concavum,P. minimum,P. rathymum, andP. lima. Installation of fish farms onPosidoniabeds should be avoided, not only to preserve this vulnerable habitat, but also to avoid fish contamination by toxic species derived from the resuspension of epiphytic community on seagrass substrata to the water column.