So I was out fishing on the weekend July 11 and 12th. We were fishing in the Columbia River and had a great weekend ,caught lots of fish.After the sun went down we filleted one rainbow for dinner.Half way threw my meal I noticed this in the meat.It is about 2to3mm in diameter and about 10mm long.It looks as though there is some sort of copper windeing inside?

Any body know what it is?