This study proposes a new method for the determination of polyethylene in Merluccius Gayi by microwave digestion, Nile Red fluorescent staining, mobile phone camera and image analysis. We have demonstrated that lyophilization of the sample is an unnecessary step in the process of determining polyethylene microplastics, obtaining recoveries close to 65% and generating sample losses. Furthermore, a method for matrix reduction is validated using direct raw sample digestion with 9/1 HNO3/H2O2 microwave-assisted digestion achieving recoveries of over 98% for microplastics. Polyethylene fluorescent color obtained was a bright yellow, which allowed it to be distinguished from micro-particles of polystyrene, polypropylene, polyvinyl chloride, and polyethylene terephthalate easily to the naked eye. Additionally, it was possible to train artificial intelligence to perform this selective identification through image analysis.