Metal concentrations, selenium-mercury balance, and potential health risk assessment for consumer of whiting (Merlangius merlangus euxinus L., 1758) from different regions of the southern Black Sea

The significant increase in the human population and the associated industrial wastes have a widespread impact on coastal areas. It is important to monitor trace elements that affect food safety and pose a potential consumer health threat. All over the Black Sea coast, people enjoy consuming whiting as both meat and roe. In February 2021, whitings were caught by bottom trawling from four different locations on the coasts of Kastamonu, Sinop (Sarıkum, Adabaşı), and Samsun in the southern Black Sea region. The meat and roe extracts obtained from whiting samples were analyzed through an optical emission spectrophotometer (ICP-MS). Trace element concentrations of whiting meat and roe in this study were Zn > Fe > Sr > As > Al > Se > B > Mn > Cu > Hg > Li > Ni > Ba > Pb > Cr > Cd and Zn > Fe > Al > As > Cu > Sr > Mn > Se > B > Ba > Li > Ni > Hg > Cr > Pb > Cd, respectively. These amounts were lower than the acceptable values accepted by the EU Commission. In case of whiting and roe consumption of a maximum of three portions (860.33 g) for Adabaşı, six portions for Kastamonu (1432.37 g), three portions for Samsun (828.55 g), and five portions (1253.04 g) for Sarıkum per month do not pose a health risk.

Diclidophora merlangi (Kuhn, 1829) Krøyer, 1838 (Monogenea: Diclidophoridae) as an indicator of hydrocarbon pollution in the North Sea

This study presents the results of analyses of data on infections of 2646 whiting Merlangius merlangus with the monogenean Diclidophora merlangi. All fish were caught in the North Sea and off the north coast of Scotland in 1990, 1993 and 1995. The aims were to analyse these data in relation to the locations of whiting sampling stations and oil installations active at that time, and to evaluate the results in terms of D. merlangi as an indicator of hydrocarbon pollution. Mean abundance of D. merlangi increased significantly with increasing proximity to the nearest oil field, with an accelerated rate of increase within approximately 2 km of the oil field. Age of oil field and whiting length showed no significant effect on parasite abundance, but there was a small difference between years. The results support those of previous studies in demonstrating the value of monogeneans as indicators of hydrocarbon pollution.

Morphological and molecular identification of Cryptocotyle lingua metacercariae isolated from Atlantic cod (Gadus morhua) from Danish seas and whiting (Merlangius merlangus) from the English Channel

Trematode larvae (metacercariae) causing black spot disease occur frequently in gills, fins, skin and the superficial muscle layers of marine fish. Species within the genus Cryptocotyle Lühe, 1899 are frequently associated with this disease. Descriptions of the metacercarial stage are relatively limited and none has hitherto been reported from fish from the English Channel. The present study reports the morphological and molecular identifications of encysted black spot-inducing parasites from whiting (Merlangius merlangus) and Atlantic cod (Gadus morhua) caught respectively from the north coast of France (English Channel) and from Danish sea waters. Metacercariae were characterised morphologically based on microscopic observations and molecularly using Sanger sequencing of fragments of the mitochondrial cox1 gene and rDNA ITS region. Morphological data were compared with available data in the literature. Phylogenetic trees including reference sequences were built to confirm morphological and molecular identifications. This survey constitutes the first description of C. lingua metacercariae in the English Channel ecosystems.

Relationship Between Heavy Metal Accumulation in Fish Muscle and Heavy Metal Resistance Genes in Bacteria Isolated from Fish

Cadmium, cobalt, copper, nickel, and zinc are the most common pollutant heavy metals that can be discharged into the marine environment with different sources. Whiting (Merlangius merlangus) and mullet (Mullus barbatus) were sampled in four seasons in a year to determine Cd, Co, Cu, Ni, and Zn levels in the muscle and to determine heavy metal resistance genes (MRGs) such as copA, czc, and ncc genes in coliform bacteria isolated from the fish. In both species, zinc was the most abundant metal, while Cd and the Co levels were scarce. Co level was significantly higher in summer in mullet than that of whiting (p < 0.001). The most prevalent MRGs was determined as copA (46.2%) followed by czc (35.8%) and ncc (17.9%). Increased Co and Ni level in the muscle significantly affected the presence of ncc gene in bacteria, while the presence of ncc and copA genes was affected by Ni and Cu levels found in the fish muscle. There was a significant positive correlation between Cd level in the muscle and presence of czc and ncc gene in the bacteria (p < 0.029). When the levels of Cu, Zn, and Cd increased in the muscle of the fish, occurrence of MRGs genes was increased significantly (p < 0.0001). A strong positive correlation was found between heavy metal resistance levels in fish and the prevalence of E. coli and coliforms that harbor heavy metal resistance genes which will be a problem in aquaculture, aquatic ecosystem, and public health.

Quantitative Determination of Heavy Metal Contamination in Horse Mackerel and Whiting Caught in the Sea of Marmara

In this study, the concentrations of lead, cadmium and manganese were determined in horse mackerel (Trachurus mediterraneus) and whiting (Merlangius merlangus euxinus) that were caught in the Sea of Marmara. These are commonly consumed fish species in this region. Fish were provided by a fishermen quarterly between March 2013 and December 2013 and, separated according to size (small, medium and large). Pb(II), Cd(II) and Mn(II) levels were determined using the wet digestion method by Graphite furnace atomic atomic absorption spectrophotometer. According to this study, for horse mackerel, the highest concentration of lead, cadmium, and manganese was 6.69 µg kg^-1 (September), 5.24 µg kg^-1 (March) and 9.24 µg kg^-1 (June), respectively. For whiting, the highest concentration of lead, cadmium, and manganese was 2.25 µg kg^-1 (June), 0.263 µg kg^-1 (September) and 10.4 µg kg^-1 (June), respectively. These heavy metal levels in fish were found to be acceptable for human consumption according to World Health Organization border values.