Use of meristic and morphometric characteristics for the differentation of Atlantic herring (Clupea harengus harengus Linnaeus) stocks in Newfoundland and adjacent waters

Numbers of vertebrae, gill rakers, pectoral, anal and dorsal fin rays and the relative size of various body parts (orbit diameter, head, snout, postorbital and predorsal length) of herring from Newfoundland and adjacent areas were examined to ascertain the value of these characters for the differentiation of herring stocks in the Newfoundland area. -- Spring and autumn spawners from the same area differ significantly in several morphological characteristics. Mean numbers of gill rakers and of pectoral and anal fin rays are generally higher (P<0.01) for autumn-spawning than for spring-spawning herring. These meristic differences are related to water temperatures during larval development and to differences in developmental rates of spring- and autumn- hatched larvae. In most areas autumn spawners also have relatively larger heads, snouts, orbit diameters, postorbital and predorsal lengths than spring spawners, A linear discriminant function based on three meristic characters was used to correctly classify from 79 to 91% of individual southwest Newfoundland spring and autumn spawners to their respective spawning groups, which indicates that the amount of interchange between the two spawning groups is probably slight. -- Sexual dimorphism in meristic and morphometric characteristics is negligible. Gill-raker number apparently increases with fish size in juvenile herring but not in adults. Correlation of the other meristic characters with fish length is negligible. Mean numbers of vertebrae and anal fin rays differ significantly between year-classes from the same locality in some instances. Dorsal fin-ray averages are unsatisfactory for stock separation, but mean numbers of pectoral and anal fin rays, gill rakers and vertebrae appear useful to varying degrees for this purpose. -- Covariance comparisons of the log-log regressions of body parts on standard length revealed considerable heterogeneity in morphometric characteristics, Between-area differences are evident for all characters and all pairs of areas compared. Significant differences are found even between closely related stocks. -- Both meristic and morphometric characters appear to be useful indicators of stock heterogeneity, but morphometric characters are less valuable than meristic characters and other methods for stock differentiation. Stock relationships indicated by the combined results of the meristic and morphometric comparisons agree in most instances with those suggested by other methods.