Fish bladders, known in brewing as isinglass. Is a refined form of the fish product that is used for its collagen content. Collagen naturally attracts yeast and other positive charged haze formers. It's a clarification agent. As in by its very nature it's added and is self removing. It's tantamount to complaining your steak has hoofs in it because at one point it was connected to the same cow.
After fermentation is done isinglass is added, it's given a few days to settle out and blown out the bottom.
It's stupid expensive and there are now more modern ways of clarification that are faster, cheaper, and more consistent. The few that use it do it for tradition.
MSG? I mean sure I guess, I've been in the industry for 7 years and have never heard of it. Savory flavors Arn't usually a hit in most beer.
Besides, every credible msg study finds it has no harm and is naturally found in many foods. Every restaurant I've worked in that had a request to remove it made a big act about it yet we never cooked it different. My friend worked at a Chinese delivery place that used to write in big letters "no msg" on the ticket, yet you think the fob Chinese cooks did anything different? Fuck no they didn't. My dad used to swear msg gave him bad headaches till I told him the BBQ place I worked at had lots in the season salt and the sauce. Never got em after eating there.