Why are we still looking at mice studies for such a human-used substance?

This study used EPA: 0.55 mg/kg/day, and DHA: 0.55 mg/kg/day.

Among the largest I've heard in human studies are things like 4,400mg EPA and 2,200mg DHA.

Examine.com is one of the best resources to understand what evidence shows about supplements.

EPA appears to be the component that works for depression.

Also, important these days, is the quality: it should be filtered from heavy metals, and processed and stored in a way that avoids it going rancid by the time you consume it.

I strongly believe in the benefits of having a higher omega-3:omega-6 ratio than is common nowadays.