Diagnosis:
Remarks: the scales of clupeids are generally large and easily shed. There is substantial variation in size and shape, not only between the sampling series, but also within a series. Amongst the species, however, the scales are remarkably similar and can be difficult to tell apart, especially if the scale material is fragmented. Along the midventral line of the body, the scales become keeled and highly modified, forming scutes. The focus definition is variable. The scales lack radii, but fracture cracks are common and often run parallel and across circuli. The circuli/annuli are concentric with the scale margin, but are not always concentric around the focus. Often the circuli/annuli run transverse across the scale. The fields (anterior, posterior, and lateral) are less distinct. The posterior field is considerably different from the rest of the scale, and looks similar to that of salmonids. It is sometimes referred to as a "wing." It is often clear with fracture cracks and striations, and the edge is crenulated.
The only other major study to consider the morphology of clupeid scales is that of Shackleton (1986), in her study on the sardine Sardinops ocellata and the anchovy, Engraulis japonicus. She cited approximately five-six types of clupeid scales, all differing in their overall shape. We have found that even within these types, there is considerable plasticity, although there is generally less variation in Clupea as compared to Sardinops , and relatively little variation amongst the scales of Engraulis mordax. Caution should be taken when using Shackleton's study for comparisons to fish in Northeast Pacific waters as she was using different species that are present in this study. It should also be noted that in her diagrams, she also reversed the anterior and posterior fields. What we consider the posterior field is termed a "wing" and the attachment of the wing to the edge of the anterior/lateral fields, the "wing join." In these descriptions, the term posterior field will be retained for consistency.