Shape up or ship out: migratory behaviour predicts morphology across spatial scale in a freshwater fish

Abstract

Summary 1.Migration is a widespread phenomenon, with powerful ecological and evolutionary consequences. Morphological adaptations to reduce the energetic costs associated with migratory transport are commonly documented for migratory species. However, few studies have investigated whether variation in body morphology can be explained by variation in migratory strategy within a species. 2. We address this question in roach Rutilus rutilus, a partially migratory freshwater fish that migrates from lakes into streams during winter. We both compare body shape between populations that differ in migratory opportunity (open vs. closed lakes), and between individuals from a single population that vary in migratory propensity (migrants and residents from a partially migratory population). Following hydrodynamic theory, we posit that migrants should have a more shallow body depth, to reduce the costs associated with migrating into streams with higher flow conditions than the lakes the residents occupy all year round. 3. We find evidence both across and within populations to support our prediction, with individuals from open lakes and migrants from the partially migratory population having a more slender, shallow-bodied morphology than fish from closed lakes and all-year residents. 4. Our data suggest that a shallow body morphology is beneficial to migratory individuals and our study is one of the first to link migratory strategy and intraspecific variation in body shape.

Habitat effects on intra‐species variation in functional morphology: Evidence from freshwater fish

“…Morphology-habitat associations are common among natural populations, and numerous field studies have shown that stream gradient habitats have an impact on fish morphology have been discussed extensively (Michel, Chien, Beachum, Bennett, & Knouft, 2017). In addition, numerous field studies have shown that stream gradient habitats influence fish morphology across a range of species and many freshwater fish displayed morphologically plastic responses to various habitats (Chapman et al, 2015;Senay, Boisclair, & Peres-Neto, 2014;Webb, 1984). For example, Crucian carp can alter their body shape in response to different hydraulic conditions and have been reported to develop a shallower body shape when living in water currents (Johansson & Andersson, 2009).…”

“…Several other studies have described a strong correlation between morphology and locomotion among fish species. For example, fish that occupied high flow habitats were found to have a significantly more streamlined body shape than fish occupying low flow habitats (Chapman et al., ; Collin & Fumagalli, ). Strong correlations were also shown to exist between stream hydraulics and body shape of fishes (Lamouroux, Poff, & Angermeier, ).…”

“…Strong correlations were also shown to exist between stream hydraulics and body shape of fishes (Lamouroux, Poff, & Angermeier, ). For example, fish can reduce the cost of drag and energy losses in turbulent currents by evolving a narrow and more streamlined body shape, which enables them to swim in a steadier manner (Chapman et al., ; Langerhans & Reznick, ; Webb, ).…”

“…For example, fish can reduce the cost of drag and energy losses in turbulent currents by evolving a narrow and more streamlined body shape, which enables them to swim in a steadier manner (Chapman et al, 2015;Langerhans & Reznick, 2010;Webb, 1984).…”

Behavioral and physiological adaptations to high-flow velocities in Southwestern native chubs (Gilaspp.)

“…A previous study (Moran et al, 2016) reported that G. elegans has morphological features similar to those of high-performance swimmers from the marine environment. A shallow caudal peduncle, high body fineness ratio (approaching the optimal value of 4.5; Von Mises, 1945), low theoretical drag and a high aspect ratio caudal fin are features also exhibited by tunas, many shark species, cetaceans and even extinct swimming reptilesall of these organisms are thought to be specialized for highperformance, sustained swimming (Webb, 1984a,b;Webb et al, 1984;Pettersson and Hedenström, 2000;Chapman et al, 2015;Baktoft et al, 2016). Additionally, the higher aerobic scope observed in G. elegans may allow this species to maintain higher aerobic swimming speeds than the other species tested here.…”