Precision and Bias of Cleithra and Sagittal Otoliths Used to Estimate Ages of Northern Pike

Abstract

Cleithra are thought to accurately record age information and produce the most reliable age estimates relative to other calcified structures (e.g., scales) for long-lived species of Esocidae such as muskellunge Esox masquinongy and northern pike E. lucius. Sagittal otoliths provide the most accurate and precise age estimates for other fish species, yet sagittal otoliths have never been evaluated for age estimation of any species of Esocidae. Our objectives were to determine if: 1) sagittal otoliths provided more precise age estimates than cleithra for northern pike from two populations, and 2) sagittal otolith age estimates differed systematically from cleithrum age estimates for two populations of northern pike. Ages were estimated by three independent individuals with different experience levels from sagittal otoliths and cleithra collected from 66 northern pike (32–101 cm total length) from Devils Lake, North Dakota and 45 northern pike (27–52 cm total length) from Cable Lake, Wisconsin. Cleithrum age estimates were more precise than those from sagittal otoliths for northern pike from Devils Lake, and were similar to sagittal otolith age estimates for northern pike from Cable Lake. Sagittal otolith age estimates were similar to cleithrum age estimates for northern pike from Devils Lake, but were dissimilar for northern pike from Cable Lake. We recommend using cleithra for estimating age of northern pike given that no specialized equipment is required for processing and age estimation. However, other studies are needed to further investigate the use of sagittal otoliths to estimate age of northern pike.

Relative Bias and Precision of Age Estimates among Calcified Structures of Spotted Gar, Shortnose Gar, and Longnose Gar

“…Although cleithra have never been used to age gars, the precision between readers using the cleithra of Spotted Gars was similar to those reported for Northern Pike from North Dakota (CV = 10%, exact agreement = 41%) and Wisconsin (CV = 11%, exact agreement = 49%; Faust et al. ). However, the precision between readers using the cleithra of Shortnose and Longnose gars was low and more comparable to that for White Suckers in Wyoming (CV = 16.2%; Quist et al.…”

“…To our knowledge, cleithra have never been used to age gars, but they are commonly used to age other long‐lived fishes, such as Northern Pike (Faust et al. ) and Muskellunge (Casselman ; cited by Casselman ). Cleithra were read whole under a dissection microscope (Faust et al.…”

“…Cleithra were read whole under a dissection microscope (Faust et al. ), but because the bone had become opaque in older specimens the annuli were less distinct, apparently leading to the inconsistencies in our reader bias plots. Reducing the boiling increments (Redmond ; Quist et al.…”

“…), and cleithra are used to age Northern Pike Esox masquinongy and Muskellunge E. lucius (Faust et al. ). Branchiostegal rays are historically the calcified structure most widely used to age gars (Netsch and Witt ; Redmond ; Klaassen and Morgan ; Johnson and Noltie ; Love ; Murie et al.…”

Living in the edge: the fate of individually marked pike (Esox lucius) stocked in a hyper-eutrophic lake with frequent winter hypoxia

“…This was very useful, because ageing from scales was hampered by several false annuli found in the scales (Neumann et al 1994). In general, pike ageing is done from cleithrum bones (Neumann et al 1994;Faust et al 2013), but these could not be used because all pike were returned to the lake after measurement. Formation of false annuli in pike scales has been connected with the challenging environment (Gerdeaux & Dufour 2012).…”