If squeezing oil/water from a can of tuna is BORER. Can someone squeeze the oil/water with some TUNA as well? Is there also a problem with SCHITAH (SQUEEZING) in general?
The minute pieces of tuna that will come out together with the water would not be enough to consider it as if the person is taking both good ad bad, because these minute pieces would not be eaten in any case.
Schita will not be an issue here because the tuna is cooked, and foods that absorbed outside liquids, such as cooked or foods that are marinating may be squeezed in order to improve their quality.