Looking at gill rakers is hard enough with all the info in front of you (something to compare with at a minimum is needed). That is true even with pure species. Yes pure species vary based on local conditioning. The major morphological traits don’t vary as much but yes some. If you are looking at mix species - good luck. For instance does anyone know if the GSF trait for 9-12 short and thick primary gill rakers on the 1st arch or the BG trait of 13-16 moderately long primary gill rakers on the 1st arch is genetically transferred to HBG ( GSF x BG). Answer is the hybrid of GSF X BG has an intermediate appearance of gill rakers .What if it’s a 3 way cross ( HBG X RES). Now to even make it more difficult if a hybrid like TJ’s has 9-12 short and thick primary gill rakers on the 1st arch is it from a GSF or a PS each of which have that trait. Experience and something (its relatives) to compare with can only help in the guess work.