Discrimination among live and even dead esocids can sometimes be very difficult. In areas where muskellunge and northern pike cohabit, there is inadvertent (sometimes illegal) harvest of the rare and more valuable muskellunge because many anglers can’t readily distinguish between them. Muskellunge x northern pike hybrids are recognized only by the most avid muskellunge angler and fisheries specialist. This study reviews criteria for identifying and distinguishing among esocids and researches new techniques that can be applied specifically for muskellunge, northern pike and their hybrid, the tiger muskellunge.
Body color pattern and external appearance of young, juveniles and adults provide discriminating characteristics as do the submandibular pores and cheek and gill cover scalation. External morphology such as body proportions can be used to distinguish between northern pike and muskellunge however their hybrids generally show intermediate meristic and morphometric characteristics that somewhat overlap muskellunge. Differences in the shape of dentary teeth and shape and dentition of the vomer and palatine tooth patches provide distinct diagnostic features. Scale pattern and shape and zonation of both scales and cleithra can nbe used to distinguish among these species and their hybrids. Scales and cleithra in large hybrids are larger relative to body size than in the parent species The internal anatomy also has distinguishing characteristics (e.g., location of the dorsal aorta, vertebral column and centra).
The fish were compared electrophoretically for 18 enzyme systems encoded by 35 lo ci. Muskellunge and northern pike are electrophoretically distinct for 54% (19) of their loci. The hybrid has intermediate isozyme patterns for all but two of these loci.
The results describe not only better and more easily recognizable characteristics for the angler but also more sophisticated, analytical laboratory techniques which can be used as forensic tools for discrimination among muskellunge, northern pike and their hybrids.