Red Drum Research Articles

Evaluation of Carbon and Nitrogen Stable Isotopes of Red Drum in the Northern Gulf of Mexico

Evaluation of Carbon and Nitrogen Stable Isotopes of Red Drum in the Northern Gulf of Mexico

Hypoxia acclimation improves mitochondrial efficiency in the aerobic swimming muscle of red drum (Sciaenops ocellatus)

Environmental hypoxia (low dissolved oxygen) is a significant threat facing fishes. As fishes require oxygen to efficiently produce ATP, hypoxia can significantly limit aerobic capacity. However, some fishes show respiratory flexibility that rescues aerobic performance, including plasticity in mitochondrial performance. This plasticity may result in increased mitochondrial efficiency (e.g., less proton leak), increased oxygen storage capacity (increased myoglobin), and oxidative capacity (e.g., higher citrate synthase activity) under hypoxia. We acclimated a hypoxia-tolerant fish, red drum (Sciaenops ocellatus), to 8-days of constant hypoxia to induce a hypoxic phenotype. Fish were terminally sampled for cardiac and red muscle tissue to quantify oxidative phosphorylation, proton leak, and maximum respiration in tissue from both hypoxia-acclimated and control fish. Tissue was also collected to assess the plasticity of citrate synthase enzyme activity and mRNA expression for select oxygen storage and antioxidant pathway transcripts. We found that mitochondrial respiration rates were not affected by hypoxia exposure in cardiac tissue, though citrate synthase activity and myoglobin expression were higher following hypoxia acclimation. Interestingly, measures of mitochondrial efficiency in red muscle significantly improved in hypoxia-acclimated individuals. Hypoxia-acclimated fish had significantly higher OXPHOS Control Efficiency, OXPHOS Capacity and Coupling Control Ratios (i.e., LEAK/OXPHOS). There was no significant change to citrate synthase activity or myoglobin expression in red muscle. Overall, these results suggest that red muscle mitochondria of hypoxia-acclimated fish more efficiently utilize oxygen, which may explain previous reports in red drum of improved aerobic swimming performance in the absence of improved maximum metabolic rate following hypoxia acclimation.

Assessing Energetic Pathways and Time Lags in Estuarine Food Webs

Detecting strong species interactions in food webs is often challenging due to difficulties related to adequate experimentation and the prevalence of generalist diets throughout nature. A promising new mathematical technique, empirical dynamic modeling (EDM), has demonstrated the potential to identify trophic interactions between populations by assessing time lags between associated time series. We attempted to analyze trophic linkages both within a subtropical estuary, as well as a simulated, theoretical ecosystem, to determine how energy moves through these systems. Additionally, we intended to evaluate the technique’s ability to detect biological relationships in ecosystems of different complexity. In both datasets, we were able to clearly identify strong consumer—resource interactions, which were generally related to bottom-up drivers. Overall, trophic connections at lower trophic levels were more easily detected than linkages higher in the food web. The ability of EDM to detect food web interactions appeared to be strongly influenced by the degree of observation error exhibited in the data. In the empirical dataset, several examples of bottom-up processes were clearly evident including effects of discharge, nutrients, and/or chlorophyll-a concentrations on anchovies (Anchoa spp.), Gulf flounder (Paralichthys albiguttata), and red drum (Sciaenops ocellatus). We also observed instances where lengths of time lags decreased as trophic level distances between consumers and resources decreased (for example, Anchovies, Gulf flounder, young-of-the-year seatrout). This analysis demonstrates the promising application of EDM to detect energetic pathways in systems of varying complexity.

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 20g/L with juvenile HSB for 9 and 8weeks 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.

Novel estimation of gear selectivity using a concurrent mass mortality event: A case study using red drum (Sciaenops ocellatus) in the northern Gulf of Mexico

Fishery-independent surveys are commonly used in modern stock assessment models to inform trends in abundance and these surveys may become more important when there are gaps in other data sources, such as harvest data. As a result of the federal harvest moratorium in the late 1980’s, Gulf of Mexico red drum (Sciaenops ocellatus) remains a data-limited species with little known about its post-escapement (6 – 46-year-old fish) abundance in offshore waters, which encompasses the spawning biomass of the stock. Historically, age and growth estimates were derived from purse seine collections, which was the industry’s preferred harvest technique. Recently, the addition of fishery-independent surveys, i.e. bottom longline surveys, sought to provide a potential alternative to purse seines; however, their efficacy in sampling the breadth of the offshore red drum population has not been widely evaluated. Here, we compared the age composition and selectivity of red drum collected with purse seine and bottom long line in offshore coastal waters of Mississippi and Alabama. Red drum collected in the purse seines ranged from 561 to 1018 mm total length (2–26 years old) and 770 − 1090 mm (2–36 years old) in bottom longlines. Additionally, an opportunistic sampling of red drum from a large fish kill in 2015 was used to estimate selectivity of red drum sampled by purse seine and bottom long line. Red drum selectivity generally decreased with age for the purse seine, while there was an increase in selectivity for the bottom long line survey. This novel approach using a mass mortality event to derive gear selectivity may allow fisheries scientists to refine selectivity measurements in stock assessments. Characterization of selectivity for different survey gears will allow for a more informed comparison of historic and current surveys when gear type effects change.

Assessing the Effects of Physical Barriers and Hypoxia on Red Drum Movement Patterns to Develop More Effective Management Strategies

Human modification of coastal ecosystems often creates barriers to fish movement. Passive acoustic telemetry was used to quantify movement patterns and habitat use of red drums (Sciaenops ocellatus) within and around a complex of coastal impoundments, and explored how the presence of artificial structures (i.e., bollards and culverts) and a hypoxia-related mortality event impacted fish movement. Results indicated bollards impede the movement of individuals with head widths greater than the mean distance between bollards (~16.0 cm). Red drum home range area and daily distance traveled were related to water dissolved oxygen concentrations; as oxygen levels decreased, fish habitat use area decreased initially. However, continued exposure to hypoxic conditions increased fish cumulative daily distance traveled. When exposed to anoxic waters, fish daily distance traveled and rate of movement were greatly reduced. These findings suggest prolonged exposure to low dissolved oxygen in combination with artificial structures can reduce movement of red drum, increase risk of mortality, and decrease habitat connectivity. Constructing and maintaining (sediment and biofouling removal) larger culvert openings and/or using wider bollard spacing would improve water circulation in impoundments, increase habitat connectivity, and facilitate movement of large sportfish inhabiting Florida’s coastal waters.

Poly-β-hydroxybutyrate has limited effects on growth and immune responses of juvenile hybrid striped bass Morone chrysops × M. saxatilis, and red drum Sciaenops ocellatus based on in vivo and in vitro approaches

Disease outbreaks in intensive aquaculture, particularly from bacterial pathogens, represent major constraints to efficient fish production. Therefore, development of novel disease treatment and prevention strategies have been receiving considerable attention in recent years. This study analyzed the efficacy of the organic acid poly-β-hydroxybutyrate (PHB) as an immunomodulator in hybrid striped bass (Morone chrysops × M. saxatilis) (HSB) and red drum (Sciaenops ocellatus) based on both in vitro and in vivo approaches. In vitro immunological assays, namely intra- and extra-cellular superoxide anion production and bactericidal capacity of HSB head kidney-derived leukocytes were determined to be significantly (P < 0.05) reduced when graded doses of sodium 3-hydroxybutyrate (3HB; 0.0, 0.5, 1.0, 2.0, 4.0 and 8.0 mM), a precursor to PHB, was supplemented in the cell culture media. For the HSB in vivo feeding trial, PHB-synthesizing bacteria, Zobellella denitrificans (ZD1), were supplemented to basal diets to produce five isonitrogenous and isolipidic experimental diets (40% crude protein and 10% crude lipid) containing PHB in stepwise increments (0.0, 0.125, 0.25, 0.5, 1.0, and 2.0% of dry-diet weight). In addition, a control diet was supplemented with 0.5% of a commercial purified PHB product. In a separate feeding trial, a commercial PHB product was supplemented to a practical basal diet in stepwise increments (0.0,0.125, 0.25, 0.5, and 1.0%) to isonitrogenous and isolipidic experimental diets (40% crude protein and 10% crude lipid). Juvenile HSB, and red drum (∼5.5, and 4.4 g/fish initial weight, respectively) in separate feeding trials were stocked in 38-L aquaria operated as a recirculating aquaculture systemHSB experimental diets were randomly assigned to quadruplicate aquaria of fish while the red drum experimental tdiets were randomly assigned to quintuplicate aquaria and fed for an 8-week period. HSB and red drum exhibited limited responses to graded levels of PHB, including percentage weight gain, feed efficiency, protein conversion efficiency and hepatosomatic index. Only juvenile red drum showed significantly (P < 0.05) increased muscle yield values with increasing dietary PHB while whole-body proximate composition analyses revealed no significant (P > 0.05) differences, except for HSB whole-body crude lipid. Thus, PHB (ZD1-derived and commercial) had limited effects on growth parameters, body condition factors, and immunological responses of both HSB and red drum juveniles.

Cross-sensory interference assessment after exposure to noise shows different effects in the blue crab olfactory and sound sensing capabilities

Underwater noise pollution is an increasing threat to marine ecosystems. Marine animals use sound in communication and orientation processes. The introduction of anthropogenic noise in their habitat can interfere with sound production and reception as well as with the acquisition of vital information through other sensory systems. In the blue crab (Callinectes sapidus), the statocyst is responsible for acoustic perception, and it is housed at the base of its first pair of antennae (antennule). The sensilla of the distal part of these antennule hosts the olfactory system, which is key for foraging. Given the anatomical proximity of the two sensory regions, we evaluated the possible interference of sound exposure with the crab ability to find food, by using an aquatic maze, and looked at the potential impairment of the righting reflex as well as at ultrastructural damages in statocysts. Although a significant effect was observed when looking at the time used by the animal to recover its habitual position (“righting reflex”), which was associated to lesions in the statocyst sensory epithelia, the time required to find food did not increase after the exposure to sound. When the crabs were exposed to natural sounds (marine background noise and sounds of their predators: Micropogonias undulates and Sciaenops ocellatus) they did not show significant differences in foraging behaviour. Although we found no unequivocal evidence of a negative impact of sound on olfactory capabilities, the study showed a clear righting reflex impairment correlated with ultrastructural damages of the statocysts. We argue that crab populations that cannot easily avoid noise sources due to their specific coastal distributions may incur in significant direct fitness costs (e.g. impairment of complex reflexes). This integrated approach to sound effect assessment could be used as a model for other invertebrate species to effectively monitor noise impact in marine environments.

Identifying trade-offs and reference points in support of ecosystem approaches to managing Gulf of Mexico menhaden

Gulf menhaden (Brevoortia patronus) support the largest fishery by yield in the Gulf of Mexico (GoM) and are a key forage species for many marine predators. While menhaden stock assessments indicated that overfishing was not likely to have occurred in the past, concerns have been raised regarding the possible effects of menhaden fishing on their predators. In this study, we used a US Gulfwide Ecopath with Ecosim (EwE) model to explore the predicted effects of increased menhaden harvest on the GoM ecosystem and focused our analyses on Gulf menhaden predators. Key menhaden predators identified included king mackerel (Scomberomorus cavalla), Spanish mackerel (Scomberomorus maculatus), sea trout (Cynoscion spp.), red drum (Sciaenops ocellatus), and pelagic coastal piscivores [e.g., bluefish (Pomatomus saltatrix)]. As expected, these predators exhibited reduced biomass in response to increased Gulf menhaden harvest, with a predicted 11% decrease in predator biomass at simulated fishing levels near historical highs. Our results indicate strong relationships between the effects of menhaden fishing and the predator fishing mortality for king mackerel and intermediate relationships for Spanish mackerel, blacktip shark (Carcharhinus limbatus), red drum, large coastal sharks, and pelagic coastal piscivores. Biomass of predator groups such as demersal coastal invertebrate feeders [e.g., drums and croakers (Sciaenidae)] are more affected by menhaden harvest (through trophodynamics interactions and bycatch removal) compared to the isolated effect of their fishing mortality. For almost all the groups examined in the trade-off analysis, with the exception of sea trout, current biomass (2016) was higher than their target biomass representing 75% of their biomass at maximum sustainable yield. In comparison to the time series of fishing mortality rates estimated by the most recent Gulf menhaden stock assessment, the mean ecological reference point (ERP) of 0.862 was exceeded in all but 1 year from 1977 to 2007; however, neither the target nor threshold upper ERP value has been exceeded since 2008. The observed Gulf menhaden landings from 2003 to the present were generally within the range of the projected equilibrium landings (i.e., within confidence intervals) at both the ERP target and threshold values except for three recent years.

Molecular characterization and functional analysis of tartrate-resistant acid phosphatase (ACP5) gene in red drum (Sciaenops ocellatus)

Tartrate-resistant acid phosphatase (ACP5) plays an important biological function in immune defense and is highly expressed in activated macrophages, osteoclasts and dendritic cells. In teleost, the functionality of ACP5 remains to be revealed. In this study, we cloned and identified SoACP5 from red drum (Sciaenops ocellatus) and analyzed its function in vivo and in vitro. The open reading frame of SoACP5 is 1002 bp in length, encoding 333 amino acids. SoACP5 shares high sequence identities (96.70%–49.25%) with ACP5 of other species. The SoACP5 mRNA was widely distributed in collected tissues of healthy red drum, and with the maximum in gills. The expression of SoACP5 increased significantly in vivo following challenge with Edwardsiella tarda. Moreover, the recombinant SoACP5 protein (rSoACP5) was purified with his-tag band resin columns, and confirmed to have phosphatase activity which was optimal at pH 5 and 55 °C. Various metal ions (K+, Zn2+, Mn2+, Mg2+, Ca2+, Cu2+, Fe2+ and Fe3+) have different effects on phosphatase activity. rSoACP5 induced the cellular proliferation of peripheral blood leukocytes. The over-expression and knockdown of SoACP5 in vivo had a significant effect on bacterial proliferation. Furthermore, both of the antibacterial activity and phosphatase activity were decreased when the reducedSoACP5 was oxidized by H2O2. In summary, the present study indicated that SoACP5 is likely involved in host defense against bacterial infection in S. ocellatus.

Experimental laboratory tests of short-term habitat selection by hatchery-reared juvenile red drum (Sciaenops ocellatus)

Structured estuarine habitats enhance the survival and growth of wild juvenile fishes by mediating density-dependent processes. However, the habitat selection behavior of hatchery-reared fishes upon release to the wild is not well understood. The red drum (Sciaenops ocellatus) is a highly sought-after, estuarine-dependent sportfish and the subject of stock enhancement efforts along the southeastern US Atlantic and Gulf coasts. We investigated the habitat associations of hatchery-reared red drum using experimental mesocosms intended to mimic the habitat types available at or nearby typical release sites in South Carolina, USA. Specifically, we presented juvenile red drum (overall mean ∼ 60 mm standard length) with a choice between salt marsh vegetation (Spartina alterniflora) and oyster shell in the presence and absence of a common estuarine predator (blue crab, Callinectes sapidus). Red drum more commonly associated with oyster shell over Spartina in both the presence and absence of a blue crab predator. Oyster shell habitat tended to be favored even when the location of the free-ranging blue crab predator was taken into account. Our results provide evidence that oyster shells, representative of a healthy restored or natural oyster reef, may be preferentially utilized by hatchery-reared red drum during the period immediately following release. Further investigation of post-release behaviors, including field-based experimental studies focusing on hatchery-reared red drum, is necessary to determine if the patterns of habitat selection behavior documented here have implications for post-release survival or mortality.

Quantitative evaluation on the suitable flow region inside the shielding device of submersible aquaculture facility

The primary purpose of the aquaculture facility is to provide a comfortable living environment and achieve welfare aquaculture for cultured fish in the open sea. Nevertheless, it has been a challenge to accurately assess the suitable flow region of the cultured fish inside the aquaculture facility for the severe ocean environment, which is a pressing concern for aquaculture farmers. First, the maximum domed swimming speed (MDSS) is used as an indicator to assess the swimming ability of Sciaenops ocellatus in this study, which can be measured through a vertical circulation water channel. Subsequently, the porous media theory is adopted and applied to predict the flow field inside the shielding device of the submersible aquaculture facility based on the shear stress transport k-omega turbulence model using the computational fluid dynamics (CFD) approach. In addition, combining the swimming ability of Sciaenops ocellatus and current speed distribution inside the shielding device of a submersible aquaculture facility, the suitable flow region is quantitatively assessed. The results indicate that when middle height, the inclined angle and net solidity are 0.4 m, 3π/12 and 0.65, respectively, the current speed inside the shielding device attenuates below the maximum domed swimming speed of Sciaenops ocellatus - 0.76 m/s and meets the survival of Sciaenops ocellatus for the actual sea condition with an incident current speed of 1.5 m/s. In addition, a suitable flow region for Sciaenops ocellatus, which is 204.512 m3 and accounts for 17.76% of the total aquaculture volume, is formed and located inside the shielding device, close to the downstream sides, and gradually extends towards the middle of the shielding device. Based on the swimming ability of Sciaenops ocellatus, using numerical means to describe the suitable flow region in detail is to provide clear and macroscopic guidance for aquaculture farmers.

The Phylogenetic Relationships of the Family Sciaenidae Based on Genome-Wide Data Analysis.

Uncertainty and controversy exist in the phylogenetic status of the Sciaenidae family because of the limited genetic data availability. In this study, a data set of 69,098 bp, covering 309 shared orthologous genes, was extracted from 18 genomes and 5 transcriptomes of 12 species belonging to the Sciaenidae family and used for phylogenetic analysis. The maximum likelihood (ML) and Bayesian approach (BA) methods were used to reconstruct the phylogenetic trees. The resolved ML and BA trees showed similar topology, thus revealing two major evolutionary lineages within the Sciaenidae family, namely, Western Atlantic (WA) and Eastern Atlantic−Indo−West Pacific (EIP). The WA group included four species belonging to four genera: Cynoscion nebulosus, Equetus punctatus, Sciaenops ocellatus, and Micropogonias undulatus. Meanwhile, the EIP group formed one monophyletic clade, harboring eight species (Argyrosomus regius, A. japonicus, Pennahia anea, Nibea albiflora, Miichthys miiuy, Collichthys lucidus, Larimichthys polyactis, and L. crocea) from six genera. Our results indicated that the Western Atlantic (WA) group was more ancient in the studied species, while the Eastern Atlantic−Indo−West Pacific (EIP) group was a younger group. Within the studied species, the genera Collichthys and Larmichthys were the youngest lineages, and we do not suggest that Collichthys and Larmichthys should be considered as one genus. However, the origin of the Sciaenidae family and problems concerning the basal genus were not resolved because of the lack of genomes. Therefore, further sampling and sequencing efforts are needed.

Short-term Salinity Stress During Early Development Impacts the Growth and Survival of Red Drum (Sciaenops ocellatus)

Short-term Salinity Stress During Early Development Impacts the Growth and Survival of Red Drum (Sciaenops ocellatus)

The role of carbonic anhydrase-mediated tissue oxygen extraction in a marine teleost acclimated to hypoxia.

With the growing prevalence of hypoxia (O2 levels ≤2 mg l-1) in aquatic and marine ecosystems, there is increasing interest in the adaptive mechanisms fish may employ to better their performance in stressful environments. Here, we investigated the contribution of a proposed strategy for enhancing tissue O2 extraction - plasma-accessible carbonic anhydrase (CA-IV) - under hypoxia in a species of estuarine fish (red drum, Sciaenops ocellatus) that thrives in fluctuating habitats. We predicted that hypoxia-acclimated fish would increase the prevalence of CA-IV in aerobically demanding tissues to confer more efficient tissue O2 extraction. Furthermore, we predicted the phenotypic changes to tissue O2 extraction that occur with hypoxia acclimation may improve respiratory and swim performance under 100% O2 conditions (i.e. normoxia) when compared with performance in fish that have not been acclimated to hypoxia. Interestingly, there were no significant differences in relative CA-IV mRNA expression, protein abundance or enzyme activity between the two treatments, suggesting CA-IV function is maintained under hypoxia. Likewise, respiratory performance of hypoxia-acclimated fish was similar to that of control fish when tested in normoxia. Critical swim speed (Ucrit) was significantly higher in hypoxia-acclimated fish but translated to marginal ecological benefits with an increase of ∼0.3 body lengths per second. Instead, hypoxia-acclimated fish may have relied more heavily on anaerobic metabolism during their swim trials, utilizing burst swimming 1.5 times longer than control fish. While the maintenance of CA-IV may still be an important contributor for hypoxia tolerance, our evidence suggests hypoxia-acclimated red drum are using other mechanisms to cope in an O2-depleted environment.

Effects of Photoenhanced Thin Oil Sheens on Survival and Growth of Newly Hatched Fishes: Sheepshead Minnow (Cyprinodon variegatus), spotted seatrout (Cynoscion nebulosus), and Red Drum (Sciaenops ocellatus)

Effects of Photoenhanced Thin Oil Sheens on Survival and Growth of Newly Hatched Fishes: Sheepshead Minnow (Cyprinodon variegatus), spotted seatrout (Cynoscion nebulosus), and Red Drum (Sciaenops ocellatus)

Characterization of supply of marine finfish species with potential for commercial growth in the United States

AbstractGlobal production of marine finfish has grown in total volume of production and the number of species farmed commercially, but there has been little production in the United States of marine finfish other than salmon and red drum. For most species considered to be ready for commercialization, there are few or no farms from which to evaluate the size of the market or to estimate revenues and costs necessary to assess economic feasibility. This present study takes a first step to fill this gap with an analysis of the existing supply of 20 marine finfish species identified as candidates for commercialization in the United States, as a proxy for effective demand (the volume of a product sold at the market equilibrium price). Secondary data from 1950 (where available) through 2019 were compiled on each species, including (1) global aquaculture production, (2) US aquaculture production, (3) US commercial landings, (4) US recreational landings, and (5) imports. Current effective market demand (measured as the sum of commercial landings, farmed production, and imports) was low, totaling 36.6 million kg across the 20 species, which is equivalent to less than 23% of the annual volume sold of US farmed catfish. Commercial landings for 17 of the 20 species exhibited declines, potentially offering opportunities for farmed product to capture market share by filling the increasing gaps in supply. The variability in commercial landings provides opportunities for farms to capitalize on their advantage in supplying product with a high degree of consistency of volume, size, delivery frequency, and quality. Several unknown factors suggest the need for follow‐up studies on consumer preferences, degree of substitutability among finfish species, and effects of recreational landings on demand. An important limitation to prospective producers is the lack of species‐specific import data for the generic categories of “flounder,” “bass,” and “snapper.” This supply analysis provides a foundational analysis for prospective producers, investors, and researchers interested in commercialization of these marine species.

Effects of constant flow velocity on endurance swimming and fatigue metabolism in red drum and blackhead seabream

Aquaculture has greater potential for seafood production than wild capture fisheries. To meet the growing demand for seafood, China's marine aquaculture industry has begun building deep-water cages in the open sea. However, under these conditions, fish encounter strong currents and waves, and ensuring their healthy growth is key to the farming process. To address these issues, it is necessary to study the sustained swimming abilities of cultured fish species. Blackhead seabream (Acanthopagrus schlegelii) and red drum (Sciaenops ocellatus) are traditional economic fish species in China; however, their sustained swimming ability under a constant current has been underexplored. Therefore, we examined the endurance swimming ability of three size classes of blackhead seabream and red drum at 20 °C. The fish were then subjected to swimming tests of 0, 30, 60, 90, 120, and 150 min at a constant swimming speed of 0.55 m/s (0.80 m/s), 0.65 m/s (0.90 m/s), and 0.70 m/s (0.98 m/s). The fish were then dissected to obtain muscle, blood, and liver samples; sample metabolite concentrations were measured at six time points, each of which guaranteed five sets of valid data. The results indicated that red drum has a significantly stronger swimming ability, and can be cultured in waters with a short-term flow rate not exceeding 0.75 m/s or 3.5 BL/s. Further, blackhead seabream can be cultured in waters with a flow velocity lower than 0.55 m/s or 2.5 BL/s. The species-related metabolic differences were mainly reflected in the hepatic glycogen and blood glucose concentrations, and those in swimming ability caused by body length were mainly reflected by the hepatic glycogen concentration. The hepatic glycogen concentration had the most significant effect on fish with body lengths >28 cm (P < 0.05). Overall, the experimental results indicated that the liver plays a major role in the physiological level of fish swimming fatigue, providing a direction for further research.

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 ± 2.4g), 38 juvenile red drum (Wt0 74.9 ± 4.4g), and 20 juvenile HSB (Wt0 78.0 ± 3.2g). 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 2weeks through 7weeks. 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.

Dietary Supplementation of a Commercial Prebiotic, Probiotic and Their Combination Affected Growth Performance and Transient Intestinal Microbiota of Red Drum (Sciaenops ocellatus L.).

In the present study, the potential synergism between beneficial lactic acid bacteria (Pediococcus acidilactici) contained in a probiotic and a mixture of fermentable complex carbohydrates and autolyzed brewer's yeast (or prebiotic) were explored in red drum. Four experimental diets were formulated from practical ingredients, and the basal diet was supplemented with either probiotic, prebiotic, or both supplements. Red drum juveniles (~5.5 g) were offered the four experimental diets for 56 days, and at the end of the feeding trial fish fed diets supplemented with probiotic had significantly better weight gain than those fed the non-supplemented diets, and higher protein content in their whole-body composition. Transient intestinal microbiome alpha and beta diversity were significantly affected by the dietary treatments. Interestingly, a higher relative abundance of the lactic acid genus Pediococcus was observed for fish fed diets supplemented with the prebiotic. A higher relative abundance was also observed for the predicted functions of the microbial metagenome, and many of these pathways involved the biosynthesis of essential amino acids, vitamins, and nucleotides. Even though no potential synergistic effect was observed, the individual inclusion of these prebiotic and probiotic supplements positively affected the intestinal health and growth performance of red drum, respectively.