Sex differences in metabolic rate and swimming performance in pink salmon (Oncorhynchus gorbuscha): the effect of male secondary sexual traits

Abstract

Do secondary sexual traits, such as large dorsal hump and hooked snout, decrease the swimming efficiency of male pink salmon during freshwater migration? This is the first study to address the effects of secondary sexual traits in pink salmon on oxygen uptake and swimming capacity. We conducted a laboratory experiment using a swimming respirometer and a field study using electromyogram (EMG) telemetry in the Shibetsu River, Hokkaido, Japan. We compared the relationship between MO2 (mg O2·kg−1·h−1) and swimming velocity U (m·s−1) in male and female fish, and also investigated the effects of morphological traits (secondary sexual characters) on the relationship between MO2 (mg O2·kg−1·h−1) and swimming velocity U (m·s−1). Additionally, we compared energy costs and swimming behaviour during upstream migration between male and female pink salmon. The laboratory experiment revealed that MO2 exponentially increased with increasing U; this increase was described by MO2 = 167.9e1.23U for males and 144.9e1.14U for females. Linear mixed models found that hump height and the upper jaw length in males significantly and positively affected the relationship between MO2 and U; no effect was found in females. The field study found that swimming velocity for both sexes estimated from EMG calibration was lower than optimal swimming velocity (Uopt) calculated from the laboratory experiment. We suggest that pink salmon in the Shibetsu River do not swim at the optimal swimming velocity because of the short migration distance involved (20 km).

Genetic coupling of life-history and aerobic performance in Atlantic salmon

“…Salmon males mature on average earlier than females (Fleming & Einum 2011) and the vgll3 locus is associated with freshwater maturation in male parr (Debes et al 2021;Verta et al 2020). Other studies in salmonids have found sex differences in the performance of 2+ yearold or mature individuals, including a higher aerobic scope, but not SMR, and a higher cost of swimming in males than in females (Clark et al 2011;Makiguchi et al 2017;Archer et al 2020). The lack of sex differences in metabolic phenotypes in our study both across and within age-at-maturity genotypes, therefore, supports the conclusion that sex-dependent lifehistory variation is not reflected in metabolic rates during the juvenile stage, as suggested by a few other studies (Regnier et al 2015;Prokkola et al 2021;Åsheim et al 2021).…”

Chum salmon migrating upriver accommodate to environmental temperatures through metabolic compensation

“…The rate of oxygen uptake was measured at least three times at 0.3 FL s -1 , and the lowest value from the trials was used as RMR. After measuring RMR, maximal exercise was achieved using a critical swim speed (U crit ) test based on a protocol described previously (Makiguchi et al, 2017). Briefly, the water flow was increased to 0.9 FL s -1 and the fish were made to swim for 15 min.…”

Bioenergetics‐adverse outcome pathway: Linking organismal and suborganismal energetic endpoints to adverse outcomes

“…The relationship between metabolic rate and locomotor performance has been particularly well studied in fish, due to the logistical simplicity of swim‐tunnels. Across fish species, increasing swim‐tunnel water velocity is associated with elevated metabolic rates (Figure B; Gamperl et al ; Fitzgibbon et al ; Li et al , ; Dickson et al ; Fu et al ; Fangue et al ; Penghan et al ; Nowell et al ; Tudorache et al ; Makiguchi et al ). Therefore, individuals with a higher standard metabolic rate (i.e., demand‐side energy elevation) or lower maximum metabolic rate (i.e., supply‐side energy reduction) typically have reduced swimming performance (Cano and Nicieza ).…”