The concentration of 23 metals was analyzed in the tissue of nine fish species, which represents the different habitats, i.e., primary feeder, tertiary feeder, and bottom feeder in fresh and marine waters of Visakhapatnam. Scomberomorus guttatus, Upeneus vittatus, and Penaeus indicus were selected in the coastal waters; Xiphias gladius, Stolephorus indicus, and Penaeus monodon from deep sea; and Channa striata, Puntius chola, and Macrobrachium rosenbergii from freshwater were analyzed. Metals in fish were analyzed by using the Inductive Couple Plasma Mass Spectrometer (ICP-MS). The concentrations of metals in fish were within the permissible limit set by WHO, FAO apart from Chromium, Aluminum, Manganese, and Arsenic. The concentrations were highest in coastal water fish and lowest in freshwater fish. Similarly, higher concentrations were observed in bottom feeders than in other tiers.

An assessment of heavy metal concentration in wild-captured Macrobrachium rosenbergii (giant freshwater prawns) from their natural habitat is important since it is susceptible to environmental pollution due to the rapid development and human activities along the Sarawak River. This study aimed to estimate the heavy metal contamination in muscles, exoskeletons and gills of the M. rosenbergii and to estimate the health risk assessment to human consumption. The concentration of heavy metals was analyzed by the flame atomic absorption spectrophotometer and the flow injection mercury system. The metal concentrations in prawns were detected in the following order: Hg < Cd < Co < Cu < Zn; in all body parts (P < 0.05), where a high concentration of metals was recorded in gills due to its function as the excretion site of contaminants from the body. A positive correlation of Co, Cu, and Zn in muscles and gills was observed with the increasing size of prawns. The human health risk assessment indicated a less potential adverse health effect of prawns for consumption from Sarawak River (hazard index values < 1). All samples contained metals below the Joint FAO/WHO Expert Committee on Food Additives (JECFA) permissible limit for human consumption (Cd < 2 mg/kg; Cu < 30 mg/kg; Zn < 150 mg/kg; Hg < 1 mg/kg). Therefore, M. rosenbergii from the Sarawak River were not contaminated enough to prevail high risk on human health, but regular monitoring is suggested for seasonal variability of heavy metals in M. rosenbergii for safeguarding human health.

Vibrio parahaemolyticus is a causative agent of human serious seafood-borne gastroenteritis disease and even death. Shrimps, often eaten raw or undercooked, are an important reservoir of the bacterium. In this study, we isolated and characterized a total of 400 V. parahaemolyticus strains from commonly consumed fresh shrimps (Litopenaeus vannamei, Macrobrachium rosenbergii, Penaeus monodon, and Exopalaemon carinicauda) in Shanghai fish markets, China in 2013–2014. The results revealed an extremely low occurrence of pathogenic V. parahaemolyticus carrying two major toxic genes (tdh and trh, 0.0 and 0.5 %). However, high incidences of antibiotic resistance were observed among the strains against ampicillin (99 %), streptomycin (45.25 %), rifampicin (38.25 %), and spectinomycin (25.50 %). Approximately 24 % of the strains derived from the P. monodon sample displayed multidrug resistant (MDR) phenotypes, followed by 19, 12, and 6 % from the E. carinicauda, L. vannamei, and M. rosenbergii samples, respectively. Moreover, tolerance to heavy metals of Cr³⁺ and Zn²⁺ was observed in 90 antibiotic resistant strains, the majority of which also displayed resistance to Cu²⁺ (93.3 %), Pb²⁺ (87.8 %), and Cd²⁺(73.3 %). The pulsed-field gel electrophoresis (PFGE)-based genotyping of these strains revealed a total of 71 distinct pulsotypes, demonstrating a large degree of genomic variation among the isolates. The wide distribution of MDR and heavy-metal resistance isolates in the PFGE clusters suggested the co-existence of a number of resistant determinants in V. parahaemolyticus population in the detected samples. This study provided data in support of aquatic animal health management and food safety risk assessment in aquaculture industry.

The present study was designed to evaluate the impact of gamma radiation (⁶⁰Co) on freshwater prawn Macrobrachium rosenbergii by using electron microscopic (SEM, TEM) studies. One set of prawns (experimental group) was irradiated (3, 30, 300, and 3000 mGy) by Theratron Phoenix TeleCobalt Unit [P-33], while other set of prawns (control group) was maintained (non-irradiated) separately. Scanning electron microscopic observations of gills and hepatopancreas showed fused and swollen lamella, abnormal gill tips, wrinkled lamellar epithelium, and necrotic epithelium surface in irradiated groups, while no such abnormalities were obvious in the control group. Transmission electron microscopic studies showed damaged nucleus, granulated mitochondria, vacuoles with crystalline granular inclusions, destructed membrane, vacuoles filled with granules, rough endoplasmic reticulum with residual bodies, shrunken mitochondria, dilated rough endoplasmic reticulum, and dilated cisternae of the Golgi body in irradiated groups. The structural abnormalities of vital organs could affect physiological functions such as respiration, osmo-ionic regulation and storage, secretion of the gills, and hepatopancreas, which in turn could adversely affect the growth and survivability of M. rosenbergii.

The giant freshwater prawn, Macrobrachium rosenbergii, is an important species for Bangladesh’s national economy, aquatic biodiversity, and employment opportunities; furthermore, human health risk associated to consumption of this species has become a crucial issue. Eight trace metals (Pb, Cr, Ni, Cd, Fe, Cu, Zn, and Mn) in different body parts of M. rosenbergii (U/10 as large and U/12 and U/15 as medium size), and water collected from farm and wild sources along with the human health risks were assessed in this study. Except Cd, all trace metals exceeded the maximum permissible limits proposed by different authorities. Elevated levels of Pb, Cr, Fe, Cu, Zn, and Mn were found in the wild-caught prawn, whereas Ni and Cd were higher in farmed prawn. A higher trace metal contamination was recorded from the cephalothorax part than the abdomen of both sized prawns. However, trace metal concentrations between two sizes of prawns were not statistically significant (p > 0.05). The estimated daily intakes (EDI) values were higher than the recommended and/or tolerable daily intake for Pb and Cr. Moreover, the target hazard quotient (THQ) values were > 1 for Pb, Cd, Cu, and Zn, elucidating non-carcinogenic risks to the consumers. In addition, the target cancer risk (TR) values of Pb and Ni were high and exceeded the acceptable guideline of 10⁻⁶, explicating the possibility of carcinogenic risks. Therefore, the study concludes that the consumption of the studied prawn species contaminated with elevated levels of toxic metals is associated with higher degree of potential health risks.

Although fish, crustacean, and shellfish are significant sources of protein, they are currently affected by rapid industrialization, resulting in increased concentrations of heavy metals. Accumulation of heavy metals (V, Cr, Mn, Ni, Cu, Zn, As, Se, Mo, Ag, Cd, Sb, Ba, and Pb) and associated human health risk were investigated in three fish species, namely Ailia coila, Gagata youssoufi, and Mastacembelus pancalus; one crustacean (prawn), Macrobrachium rosenbergii; and one Gastropoda, Indoplanorbis exustus, collected from the Buriganga River, Bangladesh. Samples were collected from the professional fishermen. Cu was the most accumulated metal in M. rosenbergii. Ni, As, Ag, and Sb were in relatively lower concentrations, whereas relatively higher accumulation of Cr, Mn, Zn, and Se were recorded. Mn, Zn, and Pb were present in higher concentrations than the guidelines of various authorities. There were significant differences in metal accumulation among different fish, prawn, or shellfish species. Target hazard quotient (THQ) and target cancer risk (TR) were calculated to estimate the non-carcinogenic and carcinogenic health risks, respectively. The THQ for individual heavy metals were below 1 suggesting no potential health risk. But combined impact, estimated by hazard index (HI), suggested health risk for M. pancalus consumption. Although consumption of fish at current accumulation level is safe but continuous and excess consumption for a life time of more than 70 years has probability of target cancer risk.