Lotic Environment Affects Morphological Characteristics and Energy Metabolism of Juvenile Grass Carp Ctenopharyngodon idella

Abstract

This study investigated the effect of a lotic environment on morphological characteristics and energy metabolism in juvenile grass carp Ctenopharyngodon idella. The fish were stocked in the lotic environment and forced to swim for 12 h per day for 4 weeks at three water current velocities of 0.5, 2, and 4 body length s−1 (Bl s−1). The control fish were stocked in the lentic environment with water current velocities of 0 Bl s−1. The results showed that lotic environment significantly increased body weight, body length, and condition factor of grass carp. The first principal component (PC1) characterized by measured overall body size suggested that fish in a lotic environment had body stoutness and wider tail stalk. Standard metabolic rate (SMR), maximum metabolic rate (MMR), and aerobic swimming performance (Ucrit) were elevated with the increased water flow and positively correlated with PC1. The 4 Bl s−1 group showed significantly decreased contents of serum glucose and muscular glycogen, and a significantly increased level of serum lactic acid. The mRNA expression levels of AMP-activated protein kinase-phosphorylate PPAR γ coactivator 1 α-nuclear respiratory factor 1 (AMPK-PGC1α-NRF1) pathway-related genes were significantly upregulated in red muscle of grass carp in the lotic environment. Water flow environment at 4 Bl s−1 significantly increased ratios of metabolic enzymes (lactate dehydrogenase/citrate synthase) and cytochrome c oxidase/citrate synthase) in the muscle. The relationship between morphological characteristics and metabolic capacity suggested that the body size of grass carp in a lotic environment was shaped to promote energy metabolism. The study identified the evidence of the mechanism and relationship of the trade-off between energy and morphology in grass carp.

The growth‐promoting effects of exercise in finfish: A systematic review and meta‐analysis

“…The benefits of exercise therefore do not exclusively apply to fast‐swimming, athletic fish, like salmonids, suggesting that the underlying mechanisms may not be linked to lifestyle. Indeed, exercise has been shown to increase growth rates in a wide diversity of species, such as leopard sharks ( Triakis semifasciata ), 57 yellowtail kingfish ( Seriola lalandi ), 39 pacu ( Piaractus mesopotamicus ), 58 Danube bleak ( Chalcaiburnus chaicoides mento ), 59 and grass carp ( Ctenopharyngodon Idella ) 60 . Few studies have investigated the effects of exercise on growth in highly sedentary fish, like flounder, and those that have, report modest, nonsignificant increases in growth at speeds of ≤1 BL s −1 61,62 .…”

“…Indeed, exercise has been shown to increase growth rates in a wide diversity of species, such as leopard sharks (Triakis semifasciata), 57 yellowtail kingfish (Seriola lalandi), 39 pacu (Piaractus mesopotamicus), 58 Danube bleak (Chalcaiburnus chaicoides mento), 59 and grass carp (Ctenopharyngodon Idella). 60 Few studies have investigated the effects of exercise on growth in highly sedentary fish, like flounder, and those that have, report modest, nonsignificant increases in growth at speeds of ≤1 BL s À1 . 61,62 Variation in species responses to exercise training, previously ), along with their 95% confidence intervals (thick bars), prediction intervals (thinner bars), and individual data points are scaled by precision (inverse of standard error).…”