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h i g h l i g h t s• In India, this is the first-ever assessment, which offer an insight on the accumulation of bacteria in farmed oysters.• We investigated the dynamic process of microbial bio-accumulation and how it is influenced by rainfall.• Bio-accumulation was high during the pre-monsoon season when the Lake is brackish.• Salinity and temperature play a major role in the survival of coliform bacteria in the shellfish growing water.• We can reduce input costs in the laboratory by analysing faecal coliform as a quality indicator instead of using E. coli as an indicator. a r t i c l e i n f o

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Trace metal concentrations were monitored in the yellow clam (Paphia malabarica), green mussel (Perna viridis) and edible oyster (Crassostrea madrasensis) from growing areas in the Ashtamudi and Vembanad estuaries, Kerala. Ranges of mean annual concentrations (mg/kg) were Ni (0.46-0.65); Co (2.87-3.49); Fe (80.0-119.4); Mn (3.88-9.38); Zn (40.8-76.2); Pb (1.28-2.00); . In Ashtamudi, clams had higher mean concentrations of Ni, Co, Fe, Mn and Pb than oysters. Mean concentrations of Ni, Pb (in all species), Zn (in clams and mussels) and Cu (in mussels) did not exceed maximum permissible limits mandated by the Food Safety and Standards Authority of India. Mean Mn concentrations exceeded the World Health Organization guideline in the three species while mean Fe concentrations in clams and oysters did not exceed the guideline. Target hazard quotients were generally ≤ 1, except for a few Pb results in clams and mussels. Although results suggest no health risk to consumers for the reference doses, daily intakes and elements considered, regular monitoring of trace metals is recommended to maintain consumer protection given increasing anthropogenic and climatic pressures on the shell sh growing areas.

The survival of the tropical edible oyster (Crassostrea madrasensis) was examined under the condition of ice-storage in a rectangular thermocol-transport box for a period of 48 h. A total of 100 two-year old farmed oysters were used for the experimental transportation. Inside the box, all oysters were arranged in four layers covered with wet-gunny bags and lined on the top and bottom with ice. Surface and bottom temperature of the transport box varied from 9.7 to 25.2˚ C and 9.7 to 28.4˚ C respectively during the 48 h exposure. The patterns of changing temperature at both surface and bottom were found to be different. Recoveries of the oysters at every two hours till 48h were monitored by taking random samples from the box. All the oysters recovered within 1 h of being placed back into seawater and there was close to 100% recovery within 2 hours. Survival was more than 90% after 8 days of the experiment.

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Length–weight relationships (LWRs) were estimated for five deep sea fishes viz. Astronesthes martensii, Glyptophidium macropus, Neobythites multistriatus, Physiculus roseus, Synagrops japonicus from Kerala, south west coast of India. Fishes were collected from commercial trawlers monthly from February 2018 to March 2019 operating at depth ranged from 270 m (Lat. 9°29.35′ N, Long. 75°44.74′ E) to 350 m (Lat. 9°26. 49′ N, Long. 75°42.36′ E) in the south east Arabian Sea. Correlation coefficients (r2) were found high for all species, with b value ranged from 2.923 to 3.404.