Eso creo.

In this context, it sounds like a panel, but it could also be a "round table"--just depends on how the "mesas" are organized. Hope this helps.

*Nevertheless, I'd query the client to make sure that he/she is not referring to a working group and whether "panel" or "round table" best fits the situation. The choice depends on the length and structure of the seminar. If it's a presentation, it's most likely a round table or a panel (discussion).

A seminar is a group discussion. Someone gives a small lecture just to start the group discussion that would last one or two hours.

In spanish "mesa" is a reference to "mesas de discusión". Some people here have suggested to use the term "round table", and it would be appropriate as well because it is actually a way of seeing seminars, but the whole point of a seminar is to have discussions about predetermined topics, and round table doesnt sound as formal as discussion or session.

Seminars can have panels of experts invited to give their views on the topic, but it would still be a group discussion, unless it specifies that it would be a panel discussion and the attendants are only to watch quietly and maybe pose questions at te end, but that wouldn´t be called a seminar.

Another way of seeing it is to call them workshops. it is a valid terms as well, but is less formal.

Down below I post two sources. One is the seminar schedule of the american association of port authorities. Just to see how they refer to seminar topics and their organization.
And the second one is from the UW on how to create a seminar and direct it.