The effect of low pH on physiology, stress status and growth performance of turbot (Psetta maximaL.) cultured in recirculating aquaculture systems

Vasco C Mota,Johan A J Verreth,Luís A Sampaio,Ep H Eding,Leon T N Heinsbroek,Jochem Hop,Marc C J Verdegem

doi:10.1111/are.13812

Abstract

We evaluated the effect of low pH and low and high total ammonia nitrogen (TAN) concentrations on the physiology, stress status and the growth performance of turbot in RAS. Two experiments were conducted. In Experiment 1, turbot (466 g) were grown at control (pH 7.5; TAN ~0.5 mg/L) or low pH and high TAN (pH 5.7; TAN ~50 mg/L) for 55 days. In Experiment 2, turbot (376 g) were grown at control (pH 7.5; TAN ~0.5 mg/L), low pH and low TAN (pH 5.7; TAN ~5 mg/L) or low pH and high TAN (pH 5.7; TAN ~50 mg/L) for 59 days. In Experiment 1, final body weight, feed intake and growth were significantly lower and FCR significantly higher in turbot exposed to low pH and high TAN. In Experiment 2, only growth was significantly lower in turbot exposed to treatment low pH and high TAN as compared to fish in the control treatment and low pH and low TAN. Osmoregulation and stress indicators measured were within normal levels. In conclusion, turbot grew equally well in a water pH of 7.5 or 5.7 provided a low TAN. In contrast, low pH combined with a high TAN impaired turbot performance.

Highlights

Fish production in recirculating aquaculture systems (RAS) has been gaining momentum with an increasing number of recently built facilities producing various species, ranging from cold seawater Atlantic salmon (Salmo salar) to warm freshwater Nile tilapia (Oreochromis niloticus) (Dalsgaard et al, 2013; Liu et al, 2016; Martins et al, 2010)
In Experiment 2, no differences were observed among treatments for the various performance parameters with the exception of growth that was significantly lower (p = 0.03) in turbot exposed to low pH and high total ammonia nitrogen (TAN) (LpHHTAN) as compared to turbot only exposed to low pH (LpHLTAN) or to control conditions
This study showed similar turbot survival and performance cultured in a low pH of 5.7 (LpHLTAN) or high pH of 7.5 provided a low‐TAN RAS environment

Summary

| INTRODUCTION

Fish production in recirculating aquaculture systems (RAS) has been gaining momentum with an increasing number of recently built facilities producing various species, ranging from cold seawater Atlantic salmon (Salmo salar) to warm freshwater Nile tilapia (Oreochromis niloticus) (Dalsgaard et al, 2013; Liu et al, 2016; Martins et al, 2010). Turbot production in RAS still needs further improvement; the growth performance usually observed in RAS during the on‐growing phase is lower than the potential growth recorded in flow‐ through systems (Person‐Le Ruyet, 2002) This growth reduction was observed in RAS for other fish species, such as Nile tilapia (Mota, Limbu, Martins, Eding & Verreth, 2015) and European seabass (Dicentrarchus labrax) (Deviller et al, 2005). We evaluated the effect of low pH and low and high TAN concentrations on the physiology, stress status and the growth performance of turbot cultured in RAS

| MATERIALS AND METHODS

| RESULTS

Findings

| DISCUSSION