Signs would probably be from too much EPA interfering with arachidonic acid metabolism. See Chris Masterjohn's recent article:

"Providing sufficient DHA to allow the synthesis of the full spectrum of inflammation-resolving compounds is a nutritional approach to inflammation. Providing high doses of EPA that interfere with arachidonic acid metabolism, however, is a pharmacological approach, and it is likely to have many adverse consequences."

"Arachidonic Acid Deficiency • Dry, scaly, and itching skin • Hair loss • Dandruff • Reproductive difficulties in both males and females • Gastrointestinal disturbances • Food intolerances • Kidney disease • Inability to maintain weight • Poor immunity • Poor growth • Inflammation"

"Non-steroidal anti-inflammatory drugs (NSAIDs) work their magic by interfering with the production of PGE2 from arachidonic acid, a characteristic they share with EPA. One of the most common set of side effects associated with these drugs is gastrointestinal disturbances. Four out of ten users of NSAIDs experience symptoms such as heartburn, acid reflux, stomach burning, nausea, or bloating.56 Researchers have used NSAIDs to produce food intolerances in mice that result in a form of severe intestinal damage called villous atrophy that is usually associated with celiac disease,57 suggesting that a deficiency of arachidonic acid or the PGE2 made from it may underlie celiac disease and other food intolerances, perhaps by preventing the gut from forming cellular junctions and thus impairing its integrity. Excessive doses of EPA from fatty fish, fish oil and cod liver oil may contribute to all of these symptoms in susceptible individuals."

"The same conditions that reduce the requirement for arachidonic acid and DHA are likely to increase a person’s tolerance for EPA. A diet that excludes refined sugar and rancid vegetable oil, is low in total PUFA content, is adequate in protein and total energy, and is rich in vitamin B6, biotin, calcium, magnesium, and fresh, whole foods abundant in natural antioxidants should not carry any risk of arachidonic acid deficiency when moderate amounts of EPA are consumed. Liberal amounts of egg yolks and liver providing preformed arachidonic acid would provide extra insurance against damage by EPA."

They saw the GI and skin side effects in the EPA 1.8 g/d JELIS study (see table 4)

If you're going to use fish oil, I would use one with more DHA than EPA like this one.