Physiological Effects of Water Flow Induced Swimming Exercise in Seabream Sparus aurata

Abstract

A longer on-land rearing period of Gilthead seabream Sparus aurata before transfer to sea-cages would allow the farmer to benefit from exercise-enhanced growth, resilience, and robustness as induced by increasing water flow in the tanks. In this study, the physiological effects of flow-conditioning were investigated by subjecting large groups of experimental fish to minimal flow or to flow regimes inducing swimming exercise at 1 or 2 body length (BL) s−1 for a period of 8 months (February–October) in 1,500 L tanks. Fish representing the three treatment groups were then used for: (1) a stress challenge netting test and plasma cortisol measurement (baseline, peaking, and recovery levels), (2) blood plasma measurements of glucose, triglycerides, lactate, cholesterol, growth hormone (GH), and insulin-like growth factor 1 (IGF1), and (3) heart and muscle gene expression of the GH and IGF1 receptors and the muscle transcriptome by deep RNA sequencing (RNAseq). Fish size after 8 months of flow conditioning was 92 ± 27 g body weight (BW) for fish under minimal flow, 106 ± 24 g BW (+15%) at 1 BL s−1, and 125 ± 27 g BW (+36%) at 2 BL s−1. Flow conditioning at 1 BL s−1 provided optimal conditions for growth and uniformity, but also stress (lowest baseline plasma cortisol), robustness (higher condition factor and larger hearts), and energy mobilization (increased plasma glucose). Although flow enhanced growth linearly with swimming speed, also the percentage of lordotic fish increased with exercise, particularly high for swimming at 2 BL s−1. The absence of important differences in plasma GH and IGF1, and expression levels of their receptors in heart and white skeletal muscle, indicated that other factors may be involved in growth enhancement. RNAseq of the white skeletal muscle showed upregulated expression of genes involved in muscle contraction, muscle development and its molecular regulation, and immune genes that may play a role in the muscle repair mechanism. An exercise regime of swimming at 1 BL s−1 can be considered as optimal for farming robust seabream although the increase of skeletal deformities should be avoided.

Heritable variation in swimming performance in Nile tilapia (Oreochromis niloticus) and negative genetic correlations with growth and harvest weight

“…Fish with lower U crit may be heavier but not necessarily have more fillet mass. Results of a U crit test in Gilthead seabream ( Sparus aurata ), also a high bodied fish, showed that the (residual) U crit was negatively correlated with fillet mass suggesting that fast swimmers build lower fillet mass later in life 5 . A plausible explanation for our results may be the existence of a juvenile trade-off between swimming and growth performance where fish with high U crit early in life show slower growth later.…”

“…Critical swimming speed can be calculated in four different ways: as absolute U crit , with or without Wtest or SLtest as covariate in the model, as relative U crit , or as residual U crit which is the difference in U crit of an individual fish with the predicted value on basis of its length 5 . Analysing absolute U crit without a covariate for either Wtest or SLtest, has the highest additive genetic variance, but part of that genetic variance is due to genes affecting body size.…”

“…Individual fish fatigue when swimming at a specific speed interval for a certain period, from which the U crit 3 can be determined. Recently we have developed and applied such tests for gilthead seabream ( Sparus aurata ) and Atlantic salmon ( Salmo salar ) 5 . Oxygen uptake is maximal at U crit , although the anaerobic component by fast skeletal muscle increases when nearing U crit 6 .…”

Simple morphometrics for predicting lordosis‐induced deviations of body shape in reared Gilthead seabream (Sparusaurata L.)

“…Haemal lordosis, V‐shape bending of the haemal vertebrae, is a frequent abnormality of reared fish (Koumoundouros, 2010). It develops during the metamorphosis and early juvenile period, mainly due to elevated swimming activity (Palstra et al., 2020; Printzi et al., 2020; Sfakianakis et al., 2006a). During the juvenile‐to‐adult growth, lordotic individuals may present a remarkable ability to recover their abnormal phenotype, mainly by repairing the affected vertebrae (Fragkoulis et al., 2019).…”

Accelerometry of Seabream in a Sea-Cage: Is Acceleration a Good Proxy for Activity?

“…Seabream is able to swim continuously at optimal swimming speeds for long-term periods (e.g., 24 days swimming at an optimal speed of 67 cm s −1 , or 3.59 BL s −1 , for fish of ∼20 cm SL, and ∼200 g BW; Palstra and Graziano, unpublished data). However, at lower swimming speeds of 1-2 BL s −1 , fish benefit optimally from enhanced (muscle) growth (Ibarz et al, 2011;Palstra et al, 2020b) and physiological wellbeing indicated by lower baseline plasma cortisol levels, higher condition factors, larger hearts and increased plasma glucose (Palstra et al, 2020b). These results show that the more active and sustained swimming fish will resemble the features of such trained athletes including a more hydrodynamic and leaner body shape (Koumoundouros et al, 2009) with less mesenteric fat (similar to fast growing seabream; Simó-Mirabet et al, 2018), and a larger heart with higher pumping capacity and cardiac output (Farrell, 1991;Farrell et al, 2007Farrell et al, , 2009Rodnick and Planas, 2016).…”