Fish Specialize Their Metabolic Performance to Maximize Bioenergetic Efficiency in Their Local Environment: Conspecific Comparison Between Two Stocks of Pacific Chub Mackerel (Scomber japonicus)

Abstract

Species-specific ecological traits in fishes are likely to vary between populations or stocks due to differences in regional oceanic conditions, such as latitudinal temperature. We examined potential intraspecific differences in the swimming performance and metabolism of Pacific chub mackerel (Scomber japonicus) from the Northwest and Northeast Pacific stocks, which are distributed on opposite sides of the North Pacific at similar latitudes, but where the temperature contrast is large. Swimming bioenergetics and metabolic data of Northwest stock mackerel were measured at 14, 18, and 24°C using variable-speed swim-tunnel respirometers, and then the resulting bioenergetic parameters were compared with previous findings from the Northeast stock. At a given size, the maximum sustainable swimming speed (Umax) of the Northwest stock showed no significant difference compared to the Northeast stock at 18 and 24°C, but was lower at 14°C. In addition, the oxygen consumption rate (MO2) of the Northwest stock showed lower mass dependence and different temperature dependence at a given swimming speed than in the Northeast stock. Combined with stock-specific data on growth and experienced temperatures in the wild, these bioenergetic differences indicate that the swimming performance and metabolism of the two stocks are specific to their local environment to maximize bioenergetic efficiency.

Development of a bioenergetics and population dynamics coupled model: A case study of chub mackerel

“…Oxygen consumption rate and respiration-related parameters were estimated for chub mackerel in the western North Pacific through laboratory-reared experiments (Guo et al, 2021), from which the value of parameter of swimming speed dependence d r was calculated as 0.0252 s cm -1 , the parameter of mass dependence b r was defined as -0.219, constant a r and temperature dependence c r were defined as 0.0290 g O 2 g fish -1 day -1 and -21.42°C, respectively (see Appendix). This study assumed chub mackerel swimming with an optimal speed U opt in which the cost of transportation is the minimum.…”

“…This study assumed chub mackerel swimming with an optimal speed U opt in which the cost of transportation is the minimum. We used the same definition for U opt with the highest limitation of 42.5 cm s -1 in the respiration function with Guo et al (2021). To avoid overestimation of respiration for smaller fish sizes by allometry fitting, we fixed b r as 0 when the mass was smaller than 1 g. The dissipation terms of excretion and egestion followed the same equations as those used in a previous study (Ito et al, 2004).…”

“…A statistically significant correlation between the otolith-based growth rate of chub mackerel in early life stages and RPS was found among April cohorts from 2002 to 2010 (Kamimura et al, 2015), which indicated that the growth rate in early life stages may be the key to successful recruitment. A model simulation of the individual growth of chub mackerel until immature showed that years with high growth individuals in their models corresponded to the year of the observed higher recruitment and RPS (Guo et al, 2021). However, their model simulation was limited to the immature stages and did not close the life cycle.…”