Comparison of traditional and geometric morphometrics using Lake Huron ciscoes of the Coregonus artedi complex

Abstract

Objective: Here we determine how traditional morphometrics (TM) compares with geometric morphometrics (GM) in discriminating among morphologies of four forms of ciscoes of the Coregonus artedi complex collected from Lake Huron.Methods: One of the forms comprised two groups of the same deepwater cisco separated by capture depth, whereas the other three forms were shallow-water ciscoes.Result: Our three groups of shallow-water ciscoes were better separated (3% vs. 19% overlap) in principle component analysis (PCA) with TM data than with GM data incorporating semilandmarks (evenly spaced nonhomologous landmarks used to bridge between widely separated homologous landmarks). Our two deepwater cisco groups, comprising a putatively single form collected from different depths, separated more in PCAs with GM data (33% overlap) than in PCAs with TM data (66% overlap), an anomaly caused by greater decompression of the swim bladder and deformation of the body wall in the group captured at greater depths. Separation of the two deepwater cisco groups captured at different depths was not affected by the removal of semilandmarks. Assignment of forms using canonical variate analysis accurately assigned 86% of individuals using TM data, 98% of individuals using GM data incorporating semilandmarks, and 100% of individuals using GM data without semilandmarks. However, we considered assignments from the same form of deepwater cisco into separate groups as misassignments resulting from different capture depths, which reduced the accuracy of assignments with GM data incorporating semilandmarks to 66%. Conclusion:Our study implies that TM will continue to have an important role in morphological discrimination within Coregonus and other fishes similarly shaped.

Morphological differences between wild and hatchery‐reared Bloater (Coregonus hoyi) from Lake Michigan, USA

“…Lack of exposure to predators in hatchery environments could contribute to shallower body depth because predator presence can modify fish body depth, even over short time frames (i.e., plastic change; Holopainen et al, 1997). Alternatively, deeper body depth in wild fish could be due to “bloating” of wild individuals when the swim bladder expands during rapid retrieval from deep waters (see, e.g., Martin et al, 2023), although all fish used in our analyses were deflated by nets when collected. Finally, dorsal fins of hatchery‐reared fish were shorter than those of 2016 and 2017 wild fish, which could impact the swimming ability or maneuverability of hatchery‐reared fish (e.g., Laporte et al, 2016; Robinson & Parsons, 2002).…”

“…Nine metrics that have proven useful for characterizing morphological differences among coregonines (Eshenroder, Kao, et al, 2021; Eshenroder, Olds, et al, 2021; Koelz, 1929; Martin et al, 2023) were used. These metrics included measurements of eight linear morphometric characters (body depth, dorsal fin height, head length, maxillary length, orbital length, pectoral fin length, pelvic fin length, and preorbital length) and one meristic character (total number of gill rakers; Figure 1).…”

“…Gametes for these individuals were collected during 2012-2015 from the same location in Lake Michigan during the same time of year as the wild fish collections. These individuals were reared in 4000 L, light green, circular tanks (1.52 m in diameter and depth) and fed every 15-30 min with one of three feeds (either Gemma Nine metrics that have proven useful for characterizing morphological differences among coregonines Koelz, 1929;Martin et al, 2023) were used. These metrics included measurements of eight linear morphometric characters (body depth, dorsal fin height, head length, maxillary length, orbital length, pectoral fin length, pelvic fin length, and preorbital length) and one meristic character (total number of gill rakers; Figure 1).…”