Dietary creatine and guanidinoacetic acid supplementation have limited effects on hybrid striped bass.

The effects of dietary supplementation of creatine and guanidinoacetic acid (GDA) have been studied to a limited extent in various fish species including red drum (Sciaenops ocellatus) and hybrid striped bass (HBS) (Morone saxatilis x M. chrysops). However, in HSB, there is a need to better understand the impact of creatine and GDA supplementation at elevated salinity which may be encountered by this euryhaline fish. Therefore, two separate feeding trials were conducted at a salinity ranging from 15 to 20 g/L with juvenile HSB for 9 and 8 weeks to evaluate the effects of dietary creatine and GDA. In each trial, four diets were formulated with either singular additions of creatine at 2% of dry weight, GDA at 1% of dry weight, or a combination of both. Fish grew adequately in both feeding trials but no significant (P > 0.05) effects of supplemental creatine or GDA were observed on weight gain, feed efficiency, survival, hepatosomatic index (HSI), intraperitoneal fat (IPF ratio), or protein conversion efficiency (PCE). However, fish fed diets supplemented with creatine had significantly (P < 0.05) increased ash and reduced lipid deposition in whole-body tissues in the first feeding trial. Supplemental creatine also resulted in significantly higher muscle yield in the second trial, but no other effects on growth performance or body composition were observed. The addition of GDA to the diet had little effect except for significantly increasing the creatine content in the liver of fish in both feeding trials due to its role as a precursor and a catalyst for synthesis of creatine within the body. Based on the results of these two trials, supplemental creatine and GDA had rather limited effects on HSB cultured in moderately saline water.

Effects of sustained swimming exercise on growth and body composition responses of Nile tilapia (Oreochromis niloticus), red drum (Sciaenops ocellatus), and hybrid striped bass (Morone chrysops × M. saxatilis).

Exercise has been shown to increase growth of many salmonid species. However, limited research has evaluated exercise on warmwater species. The present study was conducted to evaluate with tilapia, red drum (RD), and hybrid striped bass (HSB), the effects of swimming (exercising) in a constant slow current of approximately one body length/s (1bl/s) compared to not being forced to swim in a static culture system. Concurrent trials were conducted with 22 advanced juvenile male Nile tilapia (Wt0 97.9 ± 2.4 g), 38 juvenile red drum (Wt0 74.9 ± 4.4 g), and 20 juvenile HSB (Wt0 78.0 ± 3.2 g). Equal numbers of fish of each species were pit tagged and randomly assigned to two tanks, one operated static (control) and the other with current (exercised), which were all part of the same recirculating aquaculture system. Fish were fed to satiation twice daily a commercial diet and individually weighed every 2 weeks through 7 weeks. Significant (P ≤ 0.05) enhancements of weight gain were observed for exercised tilapia and RD vs static (control) treatments. Reduced growth was observed in exercised HSB, possibly due to consistently skittish feeding behavior. Hepatosomatic index was lower in all exercised fish, though not significantly so for RD and tilapia. Significant reductions also were detected in liver glycogen of exercised tilapia and RD. Results from this study indicate that continuous exercise beneficially affected aspects of tilapia and red drum growth and altered their body composition.

Efficacy of purified nucleotide supplements on the growth performance and immunity of hybrid striped bass Morone chrysops x Morone saxatilis.

Fishmeal is being increasingly replaced in aquatic animal diets with alternative plant protein feedstuffs such as soybean meal which have lower concentrations of nucleotides; therefore, supplemental sources of exogenous nucleotides in diets could become increasingly important. A 9-week feeding trial was conducted with triplicate groups of juvenile hybrid striped bass (average initial body weight ± standard deviation, 5.6 ± 0.1 g) to determine the effects of supplementing single purified nucleotides on the growth performance and immune parameters. The basal diet, which utilized menhaden fishmeal (25%) and soybean meal (75%) as protein sources, contained 44% protein, 10% lipid and an estimated digestible energy level of 3.5 kcal g-1. Single additions of 5'- adenosine monophosphate (AMP), 5'- uridine monophosphate (UMP), 5'- cytidine monophosphate (CMP), 5'- guanosine monophosphate (GMP), and 5'- inosine monophosphate (IMP) disodium salts (Chem-Impex International, Wood Dale, Illinois, USA) were evaluated with each nucleotide added to the basal diet at 0.5% of dry weight at the expense of cellulose. A positive control diet in this trial was a diet containing 5'- AMP from Sigma-Aldrich also supplemented at 0.5% by weight. Results showed significantly (P < 0.05) improved weight gain between fish fed AMP-supplemented diets and the basal diet. No statistical significance (P > 0.05) was detected in whole-body proximate composition and protein retention of fish fed any of the dietary treatments. The respiratory burst of whole blood phagocytes also was significantly (P < 0.05) higher in fish fed the AMP Sigma diet compared to the other dietary treatments. Dietary IMP and AMP both significantly (P < 0.05) enhanced the capacity of isolated phagocytes to generate extracellular superoxide anion compared to all other dietary treatments. No significant differences were seen in other innate immune parameters such as plasma lysozyme, total plasma protein, and total immunoglobulin. The ability of isolated B lymphocytes to proliferate prompted by the presence of lipopolysaccharides was significantly (P < 0.05) different among dietary treatments with the highest simulation index observed in fish fed the diets containing AMP Sigma and UMP; however, it was not significantly different from that of fish fed the basal diet. Based on all the measured responses, it is concluded that AMP at 0.5% of diet had the most positive influence on growth performance and innate immunostimulation of hybrid striped bass.

Effects of a Bioprocessed Soybean Meal Ingredient on the Intestinal Microbiota of Hybrid Striped Bass, Morone chrysops x M. saxatilis.

The hybrid striped bass (Morone chrysops x M. saxatilis) is a carnivorous species and a major product of US aquaculture. To reduce costs and improve resource sustainability, traditional ingredients used in fish diets are becoming more broadly replaced by plant-based products; however, plant meals can be problematic for carnivorous fish. Bioprocessing has improved nutritional quality and allowed higher inclusions in fish diets, but these could potentially affect other systems such as the gut microbiome. In this context, the effects of bioprocessed soybean meal on the intestinal bacterial composition in hybrid striped bass were investigated. Using high-throughput sequencing of amplicons targeting the V1-V3 region of the 16S rRNA gene, no significant difference in bacterial composition was observed between fish fed a control diet, and fish fed a diet with the base bioprocessed soybean meal. The prominent Operational Taxonomic Unit (OTU) in these samples was predicted to be a novel species affiliated to Peptostreptococcaceae. In contrast, the intestinal bacterial communities of fish fed bioprocessed soybean meal that had been further modified after fermentation exhibited lower alpha diversity (p < 0.05), as well as distinct and more varied composition patterns, with OTUs predicted to be strains of Lactococcus lactis, Plesiomonas shigelloides, or Ralstonia pickettii being the most dominant. Together, these results suggest that compounds in bioprocessed soybean meal can affect intestinal bacterial communities in hybrid striped bass.

Effects of the antidepressant venlafaxine on fish brain serotonin and predation behavior.

Antidepressants that enter receiving waters through final treated wastewater effluent have exhibited relatively low acute toxicity in traditional fish tests at currently measured concentrations. However, the psychotropic mode of action of these compounds warrants examination of the behavioral effects these chemicals may have on aquatic organisms. Previous research has demonstrated that exposure to the antidepressant fluoxetine causes decreased brain serotonin levels in fish and results in a decreased ability to capture prey. Another antidepressant, venlafaxine, has been found at low µg/L concentrations in final treated wastewater effluent. The objective of this study was to quantify the effects of venlafaxine on fish predation behavior and determine if this effect was correlated with changes in brain neurotransmitter concentrations. The predator prey bioassay used hybrid striped bass (Morone saxatilis x Morone chrysops) as the predator and fathead minnows (Pimephales promelas) as prey. Bass were exposed to venlafaxine (0-500 µg/L) for a period of 6 days and then allowed to recover for 6 days. During both exposure and recovery, bass were fed four minnows every third day. The time to capture the minnows was quantified and compared among treatments to determine if there was an effect on predation behavior. Brain tissue was analyzed for serotonin, norepinephrine, and dopamine, to determine the relationship between exposure concentration, brain monoamine levels, and predation behavior. Results indicated that venlafaxine exposures increased time to capture prey 1 and 2 by day 6 for the 250 and 500 µg/L treatments. Time to capture prey 3 was increased for all venlafaxine treatments by day 6. Venlafaxine caused a statistically significant decrease in brain serotonin concentrations that initially decreased in a dose dependent manner before reaching a steady state by the end of exposures for all treatments. No significant, dose-dependent changes in dopamine or norepinephrine were seen. Brain serotonin alone did not adequately explain behavioral results. Serotonin response in other tissues as well as peripheral effects may have accounted for additional behavioral responses after brain serotonin reached a depressed steady state.

Reprint of: Effects of the antidepressant venlafaxine on fish brain serotonin and predation behavior.

Antidepressants that enter receiving waters through final treated wastewater effluent have exhibited relatively low acute toxicity in traditional fish tests at currently measured concentrations. However, the psychotropic mode of action of these compounds warrants examination of the behavioral effects these chemicals may have on aquatic organisms. Previous research has demonstrated that exposure to the antidepressant fluoxetine causes decreased brain serotonin levels in fish and results in a decreased ability to capture prey. Another antidepressant, venlafaxine, has been found at low µg/L concentrations in final treated wastewater effluent. The objective of this study was to quantify the effects of venlafaxine on fish predation behavior and determine if this effect was correlated with changes in brain neurotransmitter concentrations. The predator prey bioassay used hybrid striped bass (Morone saxatilis x Morone chrysops) as the predator and fathead minnows (Pimephales promelas) as prey. Bass were exposed to venlafaxine (0-500 µg/L) for a period of 6 days and then allowed to recover for 6 days. During both exposure and recovery, bass were fed four minnows every third day. The time to capture the minnows was quantified and compared among treatments to determine if there was an effect on predation behavior. Brain tissue was analyzed for serotonin, norepinephrine, and dopamine, to determine the relationship between exposure concentration, brain monoamine levels, and predation behavior. Results indicated that venlafaxine exposures increased time to capture prey 1 and 2 by day 6 for the 250 and 500 µg/L treatments. Time to capture prey 3 was increased for all venlafaxine treatments by day 6. Venlafaxine caused a statistically significant decrease in brain serotonin concentrations that initially decreased in a dose dependent manner before reaching a steady state by the end of exposures for all treatments. No significant, dose-dependent changes in dopamine or norepinephrine were seen. Brain serotonin alone did not adequately explain behavioral results. Serotonin response in other tissues as well as peripheral effects may have accounted for additional behavioral responses after brain serotonin reached a depressed steady state.