Hello Carlos,
It is definetely Mytilidae; it might be perna perna. The colour isn't exactly correct, in my experience, for M. edulis. Of course, it may be a juvenile M. galloprovincialis; sometimes they are yellowish in colour.
Best wishes,
Emma.
Thanks Emma, I think that is Perna perna, but as you say, also can be Mytilus galloprovincialis. I will name as aff Perna perna.
Kind regards.
in my opinion this is juv. m. galloprovincialis. by the way, to be sure, you have to check the number of the teeth of the legament. meaning two on one valve and one onto the second valve. if so, well you has a perna