A fish blog.com

The freshwater pearl mussels (Margaritifera margaritifera) live to be over 100 years old. Some scientists claim that its maximum age is about 200 years. This gives the mussel a lot of opportunities to reproduce, but in the Northern Europe most populations of freshwater pearl mussel is classed as either “extinct”, “endangered” or“vulnerable”. The mussel is dependent on the presence of fish (mainly trout and salmon) as hosts for its larvae. Polluted rivers may not damage the mussel population, but it may have an negative influence on the fish they are so depended on.

A couple of years ago a friend of mine told me he had found a strange mussel in a stream. It appeared to be a freshwater pearl mussel. He saw a couple of other mussels in the same stream, but they were all big and old. This sad fact supports the situation in United Kingdom were it is believed that many populations have not produced young for over 30 years.

We reported the found of freshwater pearl mussels to the local authorities. They were not aware of this population, and they would examine the location the next summer. On my island (in the southwestern part of Norway) there are now two known populations of freshwater pearl mussels.

In most rivers in Norway it is now hard to find these mussels. 100 years ago thousands of pearl mussels were harvested each year. The search for the pearls was almost an industry in some rivers. Now there are no commercial interest for the pearl mussel in Norway, and the mussel is protected by law (from 1993). Still reports indicate decline in every known population.

The common cockle is (as its name says) a common shell in Europe. This species is of commercial interest in several countries (like in Great Brittan and Holland).

A couple of years ago mechanical harvesting was banned in Holland due to damages the vessels and the gear caused to the bottom fauna. The cockles are therefore now harvested manually.

We have cockles in Norway as well, but we do not have those large harvesting areas like the shallow banks off the coast of Holland.

The cockles above were found on sand bottom (30 cm. depth). I used my fingers to filter the sand, and it was then easy to find (and feel) the cockles. The growth lines indicate that these cockles are 5-8 years old.

The Norwegian name for common cockle is “heart shell” (translated). When you look at the photo of a live cockle below you will understand how it got its Norwegian name.