Effects of Stocking Density on Growth Performance and Stress Responses of Bester and Bester ♀ × Beluga ♂ Juveniles in Recirculating Aquaculture Systems

Abstract

The study aimed to compare the growth performance and physiological responses of bester (B) and backcrossed bester ♀ × beluga ♂ (BB) in response to crowding stress under different stocking densities, as well as to establish a threshold stocking density for rearing BB in a recirculating aquaculture system (RAS) without welfare impairment. For this purpose, in the first trial (T1), B (181.15 ± 21.21 g) and BB fingerlings (181.98 ± 28.65 g) were reared in two stocking densities of 2 kg/m2 and 4 kg/m2 in fiberglass tanks (1 m3) for 6 weeks. In a parallel trial (T2), the BB hybrids (335.24 ± 39.30 g) were kept in four initial stocking densities, ranging from 5 kg/m2 to 12 kg/m2. The results of T1 revealed better growth indices (i.e., final mean weight, weight gain, specific growth rate) at lower stocking densities for both hybrids; however, in terms of growth performance, the BB hybrid showed better results when compared with the B hybrid. BB hybrids registered significantly (p < 0.05) lower serum cortisol and MDA and higher lysozyme than B hybrids, showing higher tolerance to crowding stress. Nevertheless, at higher densities, selected serum parameters (i.e., hematological indices, cortisol, glucose, protein, malondialdehyde, lysozyme) and growth performance indices used to evaluate the hybrids indicate that high stocking density could affect the growth and welfare of BB hybrids, and that the selected serum parameters could be used as good indicators for chronic stress caused by overcrowding conditions.

Rearing performance of juvenile yellowtail snapper, Ocyurus chrysurus, in a sea water recirculation system at two different stocking densities

“…This study reports that lower stocking density performs better than higher stocking density in an experimental marine recirculation system for yellow tail snapper. Similar results were obtained for hybrid sturgeon on lower stocking densities in RAS (Dediu et al, 2021). One of the effects associated with high stocking densities is reducing or retardation of growth and has been demonstrated in different species as sturgeon (Jodun et al, 2002;Yang et al, 2011), Nile tilapia (Oreochromis niloticus) (Aketch et al, 2014;Gibtan et al, 2008), European seabass (Dicentrarchus labrax) (Saillant et al, 2003), Atlantic cod (Gadus morhua) (Lambert & Dutil, 2001), rainbow trout (Oncorhynchus mykiss) (Ellis et al, 2002), turbot (Psetta maxima) in sea cages (Aksungur et al, 2007), and red drum (Sciaenops ocellatus) (Sandifer et al, 1993;Vela et al, 2018).…”

Evaluation of DDGS as a Low-Cost Feed Ingredient for Common Carp (Cyprinus carpio Linneus) Cultivated in a Semi-Intensive System

“…The following morphometric measurements were performed weekly: body mass (g), total length (cm), standard length (cm), height (cm), maximum thickness (cm), circumference (cm), and head length (cm). Based on the measurements performed, the main growth indices were calculated [ 27 , 28 ].…”

A review of influencing factors on a recirculating aquaculture system: Environmental conditions, feeding strategies, and disinfection methods

“…Too high an aquaculture density will also increase the rate of oxygen consumption and ammonia excretion of fish, causing oxidative damage, reducing the activities of functional enzymes, disrupting hormone levels, exerting a negative influence on the antioxidant system and immune system of fish (Dediu et al, 2021;Long et al, 2019;Zhang et al, 2019). Besides, a relatively lower stocking density provides low, stable concentrations of ammonia, nitrite, and organic load.…”

“…A high stocking density can also have adverse effects on muscle development of fish, reducing protein and crude fat content of the fish body and further influencing the aquatic product quality (Aidos et al, 2019; Ni et al, 2016; Toko et al, 2007). Too high an aquaculture density will also increase the rate of oxygen consumption and ammonia excretion of fish, causing oxidative damage, reducing the activities of functional enzymes, disrupting hormone levels, exerting a negative influence on the antioxidant system and immune system of fish (Dediu et al, 2021; Long et al, 2019; Zhang et al, 2019). Besides, a relatively lower stocking density provides low, stable concentrations of ammonia, nitrite, and organic load.…”