Distribution channels of fish and fish products in order to make it viable to end users is special as it requires proper handling, quality, temparature control and timelines. Intial distribution channel consisted of importers, distributors, wholesalers and retailers as well as food brokers and agents, with each level performing a specific task. In the recent times it is shortened from importers directly bought from wholesaler or retail chain operator. Absence of branded fresh seafood permits substitution of products and also suppliers. With the help of improved logistics and means of communication there is direct contact between wholesaler and supplier with reduced role of the agents.On the other hand, the pressure of time and increased specialisation and outsourcing of services has also created a new role for agents specialising in search of new products and markets. With supermarkets buying in bulk at lower prices allowing low prices to consumers. The successful formula of retail chains is a balanced mix of competitive pricing, large share of fresh produce and high quality standards obtained through narrow product specifications, modern logistics and stringent controls. Recent increase in consumer expectations on fish quality, environmental and animal welfare issues is leading to outbreak of diseases and parasites promoting use of antibiotics and other chemicals. Use of antibiotics and other chemicals is raising various health related concerns. Strict monitoring of this issues is important in order to overcome this problems. 

Referenced from : http://www.fao.org/fishery/topic/13287/en