the invention relates to a method of preserving shellfish using a modified atmosphere which is rich in oxygen and which contains a second main nitrogen component , such as to preserve the live bivalve shellfish and safeguard the quality of said food for as long as possible throughout the marketing and sales process . the shellfish sales packaging must be full and well compacted , for which purpose , the units must be perfectly inserted during the filling operation using a vibrator , such that the bivalve shellfish cannot open their valves and lose intervalvular liquid throughout the sales process . the invention relates to the most popular bivalve on the market in terms of sales and price and , as a result , is of particular interest to the mussel industry .