Sardines in the Mediterranean are now smaller and lighter than 20 years ago. Mona Lisa is a European project which has been studying sardine populations in the region and has established that the average lengths of sardines had fallen from 15 centimetres to 11 and the average weight has nosedived from 30 grams to 10.
Researchers attribute the dramatic decline to a 15% drop in stocks of micro-algae in the bay of Biscay, which has lowered the nutritional value of plankton. The study carried out by the French marine institute Ifremer was able to rule out overfishing and natural predators such as dolphins or tuna. It also established that there was no virus to blame for the dramatic decline.
The changing composition of plankton was investigated using a controlled sardine population of 450 fish divided into four groups and fed differing strengths of plankton. This is the largest project of its kind anywhere in the world.
The sardine is one of the most heavily fished species in the world. The high demand from canneries creates a commercial value for sardines within a certain size range. Changing the size of sardine cans would entail substantial costs for retooling packing lines, not to mention major revisions to packing and cooking protocols for the autoclaves.