Valid question though, and the answer to what I think you wanted to know is >3 months: > the clams are “paid back after three months of work by releasing them

Valid question though, and the answer to what I think you wanted to know is >3 months: > the clams are “paid back after three months of work by releasing them to a place from which they will never be caught again”. [---] this is done because they eventually become resistant to contamination in the water. https://www.zmescience.com/ecology/poznan-mussel-water-plants-892524/ https://www.zmescience.com/ecology/poznan-mussel-water-plant...