PurposeThis research formulated to obtain the optimum ordered quantity and optimum inventory range of fish products under the conditions: (1) fully back ordered (lockdown) and (2) partial back ordered (normal geographical market). In both the cases, due to the deterioration nature and in quarantine situation some vendors are not able to satisfy the customers (retailers). So in this model, the cost of penalty is introduced in quarantine time to obtain the optimal total cost.Design/methodology/approachTo find the total cost, holding cost, shortage cost and deterioration cost have to be considered. There are so many disadvantages in holding the deteriorating food products. Due to the demand and deterioration, the holding cost of the fish products is determined. The supply chain of fish marketing process to find the optimum total cost and optimum back ordered quantity in the two situations, namely, (1) normal backordering and (2) Quarantine period is explained.FindingsThe conclusion of this research is exhibited for the uncertain lockdown situation and the normal geographical markets. But in both the cases, the demand function is dependent on the backorder quantity. The expected total cost of the retailers of fish products increased at the least possible range with the increase in the shortage parameter, cost of penalty and variance. But the change in mean value leads to decreasing in the back ordered quantity, inventory level and the annual total cost of the retailers. This analysis contributes to the service of supply chain from wholesaler to retailer in high level.Research limitations/implicationsFish products are very essential for nourishment and economic spread in India. This study has spotlight the efficient method for reducing the total cost of the retailers of fish marketing. The cost of deterioration of fish is high because of its perishable nature. Due to lockdown situation, the holding cost of the fish products depends upon the backordered quantity of geographical market of fish.Practical implicationsThis research formulated to obtain the optimum ordered quantity and optimum inventory range of fish products under the conditions: (1) fully back ordered (lockdown) and (2) partial back ordered (normal geographical market).Social implicationsDue to lockdown situation, the holding cost of the fish products depends upon the backordered quantity of geographical market of fish. This research formulated to obtain the optimum ordered quantity and optimum inventory range of fish products.Originality/valueThis research formulated to obtain the optimum ordered quantity and optimum inventory range of fish products under the conditions: (1) fully back ordered (lockdown) and (2) partial back ordered (normal geographical market). In both the cases, due to the deterioration nature and in quarantine situation some vendors are not able to satisfy the customers (retailers). So in this model, the cost of penalty is introduced in quarantine time to obtain the optimal total cost. A few number of sensitivity analysis are carried out for deterioration rate, shortage parameter and cost of penalty to indicate the existence of total cost in the least possible range.