The sarcoplasmic reticulum, or the Ryanodine receptor (RyR), is an integral part of muscle contraction, because it stores calcium, a major signal for muscle contraction and relaxation. There are three major isoforms of the RyR (RyR1, RyR2, and RyR3), but another level of gene expression control for the RyR has been recently revealed. Slow transcripts amplified by polymerase chain reaction possess a retained intron, which would presumably result in a truncated non-functional RyR. To examine this phenomenon, RNA extraction was performed on red and white muscles from albacore and yellow tail fishes using Tri-Reagent and the procedure from the Molecular Research Center Inc. Evidence for the intron retention hypothesis was not shown. In blue marlin, the intron was retained in white muscle, and spliced out of the red muscle tissue DNA. In albacore and yellow fin, two phylogenetically related species to blue marlin, showed contrary evidence. In albacore, the data show that an intron is retained, while in yellow fin tune the data show that no intron is retained.