Analysis of environment‐recruitment associations for a coastal red drum population reveals consistent link between year class strength and early shifts in nearshore winds

Experiments with red drum, Sciaenops ocellatus, were conducted to assess environmental requirements and culture characteristics. Pond trials were used to evaluate the effects of salinity, chloride source, predator control, acclimation procedure, stocking density, and size at stocking on production. Survival in individual ponds ranged from 0-92%; average daily weight gain from 0.46-2.22g; and feed conversion ratio from 2.30-4.90. Survival, growth, and feed conversion ratio did not differ significantly between equivalent treatments in saltwater and freshwater ponds. The minimum chloride concentration necessary for acceptable production of red drum in freshwater ponds (250-300 mg/l) was at least 100% higher than the concentrations reported to support high survival and growth in some laboratory experiments. Mortality in ponds could be attributed to hypoxia, handling and stocking stresses, and vertebrate predators. A laboratory experiment was designed to determine the dissolved oxygen tolerance of juvenile red drum in relation to temperature and salinity. Fingerling red drum acclimated to combinations of 0.5 and 5 ppt salinity and 25 and 30 C survived to low dissolved oxygen concentration (0.34 mg/l) when concentration was reduced over several hours, as might occur in culture ponds. No difference due to temperature or salinity was detected in resistance to hypoxia. Red drum survived to significantly lower mean dissolved oxygen concentration when rate of deoxygenation was reduced. Results of these experiments indicate that red drum can be successfully cultured if water quality, predation, and handling stresses are controlled.

For many marine and estuarine fishes, there is growing evidence that processes occurring during the juvenile life stage can contribute to determining the relative success of recruitment of annual cohorts into the fishery. We studied two consecutive annual cohorts of juvenile red drum Sciaenops ocellatus from estuarine arrival through age 1 in two estuarine systems of southeastern North Carolina. For age‐0 cohorts, relative abundance generally peaked in mid to late fall, and fish were present in shallow‐water habitats through December before presumably moving to deeper waters during winter. Reappearance of red drum in shallow‐water habitats during spring occurred between late March and late April depending on spring warming rates. Considerable differences in relative abundance of age‐0 red drum were observed between estuaries; such differences may be related to variations in estuarine hydrology and flushing rates, which probably affect larval delivery and distribution. Otolith‐derived hatch date distributions indicated that red drum juveniles in North Carolina were produced between July and October; interannual differences (of up to 30 d) in peak spawning times were correlated with variable nearshore water temperatures during summer. Juvenile growth rates during fall ranged from 0.45 to 0.75 mm/d, and mortality rates were between 1.6% and 4.1% per day; ratios of weight‐specific instantaneous growth to instantaneous mortality were greater than 1.0 for all cohorts during their first fall. Both growth and mortality varied between estuaries and years, suggesting local‐scale control of these vital rates. Discrete overwinter loss rates ranged from 35% to 67%, indicating that fall cohorts of juvenile red drum could be negatively affected by variable overwinter mortality. First‐year vital rates and demographics of red drum cohorts in North Carolina displayed considerable spatial and temporal variability that could potentially affect eventual year‐class success, highlighting the need for further understanding of the linkages between juvenile ecology and fishery recruitment.

The relationship between predator gape and prey consumption in laboratory-reared larva and field-caught early juvenile red drum, Sciaenops ocellatus, was investigated in light of the hypothesis that feeding success varies throughout the early life history intervals of marine fishes. We expected the feeding ability of red drum to be more strongly constrained by mouth gape in smaller fish and expected this ability to improve with gape size. To test this hypothesis, field-caught, early juvenile red drum were examined to determine the relationship between gape size and prey size consumed. In field-caught early juveniles, gape (height and width) and prey size consumed (length and width) increased linearly with standard length (SL); however, mean width of prey consumed was only 20–47% of gape width. Furthermore, when regressed on SL, gape width yielded a higher slope than prey width. To further test this hypothesis on less developed, pre-metamorphic fish, age-specific differences in gape, number of prey and size of prey consumed prior to metamorphosis were determined from laboratory-reared red drum larvae. Similar patterns were observed for gape height– and gape width–SL relationships in laboratory-reared red drum larvae. Size of consumed prey increased from three days from hatching (dfh) to 18 dfh. The percentage of feeding larvae also increased from ∼3% at 3 dfh to 97% at 18 dfh. In both field-caught, early juvenile red drum and laboratory-reared larvae, there was little evidence that the size of prey consumed was constrained by mouth gape. It is hypothesized that besides gape size, the development of other features of the feeding mechanism (e.g., hyoid and opercular series) influences prey-capture performance prior to settlement in marine fishes.

Restriction-site variation in mitochondrial (mt) DNA was assayed among 1675 red drum (Sciaenops ocellatus Linnaeus) sampled from 20 localities along the southeastern coast of the USA (western Atlantic) and the Gulf of Mexico (Gulf). Up to four consecutive year-classes (cohorts) were sampled at most localities. Nucleotide-sequence divergence among 170 mtDNA haplotypes identified ranged (in percentage) from 0.184 to 1.913, with a mean (±SD) of 0.887 ± 0.300. Comparisons of mtDNA haplotype frequencies across year-classes within localities were non-significant, indicating temporal stability of breeding components within localities. Significant heterogeneity in mtDNA haplotype frequencies was found across all localities, between (pooled) samples from the western Atlantic and the Gulf, and among geographically spaced, regional groupings in the Gulf. Genetic divergence between subpopulations of red drum in the western Atlantic and Gulf follows a pattern exhibited in other marine fishes, and probably stems from physical (historical environmental heterogeneity, absence of suitable habitat, and current patterns) and, perhaps, behavioral factors. Genetic differences among red drum in the Gulf appear to be due largely to an isolation-by-distance effect that is attributable to behavioral factors. The latter may include female philopatry to natal bays or estuaries, limited offshore (coastwise) movement of females relative to their natal bay or estuary, or both. Genetic divergence among red drum in the Gulf occurs despite high gene flow (estimated as the number of genetic effective migrants in an island mode). Conservation and management of red drum should be based on the premise that strategies for a given bay or estuary will impact geographically proximal bays or estuaries more than distal ones. Trajectories of correlograms in spatial autocorrelation analysis suggest a geographic neighborhood size, relative to genetic migration of red drum from a bay or estuary, of roughly 500 to 600 km.

Tissue damage, antioxidant capacity, transcriptional and metabolic regulation of red drum Sciaenops ocellatus in response to nanoplastics exposure and subsequent recovery

Genetic studies of population or 'stock' structure in exploited marine fishes typically are designed to determine whether geographic boundaries useful for conservation and management planning are identifiable. Implicit in many such studies is the notion that subpopulations or stocks, if they exist, have fixed territories with little or no gene exchange between them. Herein, we review our long-term genetic studies of red drum (Sciaenops ocellatus), an estuarine-dependent sciaenid fish in the Gulf of Mexico and western Atlantic Ocean. Significant differences in frequencies of mitochondrial DNA haplotypes and of alleles at nuclear-encoded microsatellites occur among red drum sampled across the northern Gulf of Mexico. The spatial distribution of the genetic variation, however, follows a pattern of isolation-by-distance consistent with the hypothesis that gene flow occurs among subpopulations and is an inverse (and continuous) function of geographic distance. However, successful reproduction and recruitment of red drum depend on estuarine habitats that have geographically discrete boundaries. We hypothesize that population structure in red drum follows a modified one-dimensional, linear stepping-stone model where gene exchange occurs primarily (but not exclusively) between adjacent bays and estuaries distributed linearly along the coastline. Gene flow does occur among estuaries that are not adjacent but probabilities of gene exchange decrease as a function of geographic distance. Implications of our hypothesis are discussed in terms of inferences drawn from patterns of isolation-by-distance and relative to conservation and management of estuarine-dependent species like red drum. Based on estimates of the ratio of genetic effective population size and census size in red drum, observed patterns of gene flow in red drum may play a significant role in recruitment.

Advances in development of long-term embryonic stem cell-like cultures from a marine fish, Sciaenops ocellatus

The South Carolina Department of Natural Resources has been stocking red drum Sciaenops ocellatus since 1988 to evaluate parameters critical to their successful survival and recruitment in South Carolina estuaries. From 1999 to 2002, between 600,000 and 1,000,000 juvenile red drum were stocked each year in two tributaries of Charleston Harbor. The harbor and each tributary were partitioned into three independent strata and randomly sampled monthly for two decades, allowing population trends before, during, and after stocking to be evaluated. Using microsatellite-based parentage analysis, we examined the contribution of stocked age-0 juvenile red drum (15–60 mm total length) to the local population 1 year after release by using fishery-independent sampling. Analysis of these data showed that the highest contributions (88.9%) were close to the stocking site in years with low natural recruitment, whereas in years with high natural recruitment, contributions were lower and stocking was less effective in increasing catch per unit effort. The results of stocking 600,000 small juveniles/year from 1999 to 2001 in one of the study tributaries (Ashley River) indicated that stocked fish did not displace wild fish but had an additive effect on their abundance, supporting the hypothesis that trophic resources are not limiting for postlarval age-0 red drum within Charleston Harbor. The high observed variability in contribution among years of stocking similar-sized red drum suggests that (1) interpretation on a year-class-specific basis is necessary to fully understand the effects of stocking and (2) marine stock enhancement programs would benefit substantially from evaluation in the context of wild annual recruitment patterns. Received June 3, 2010; accepted August 18, 2011

Genetic variation was examined in red drum (Sciaenops ocellatus) and spotted seatrout (Cynoscion nebulosus), sciaenid marine fishes that differ in life-history components such as age and size at maturity, longevity, and migratory behavior. Survey of 22 enzymes and seven structural proteins (40 loci) revealed that measures of genic variability and F-statistics were comparable to those for other sciaenids. Differentiation into subpopulations was only weakly evident for either red drum or spotted seatrout (F,, = 0.019 and 0.032). Spotted seatrout had lower heterozygosity (<1%), spatial clumping of rare alleles, and a regional cluster of localities in the eastern Gulf of Mexico. Red drum had higher heterozygosity (3%), a mosaic geographic pattern for protein variation and for a meristic polymorphism (number of tailspots), and one slightly divergent population on Florida's Atlantic Coast. As suggested from life-history components and supported by allelic dispersion, regional differentiation, and autocorrelation analysis, the less mobile and more rapidly-maturing species, spotted seatrout, displays isolation-by-distance. Less divergence of red drum in bays is contrary to expectation based on relative inshore abundance of the two species; adult reproduction by the larger and longer-lived species, red drum, produces an offshore effective population size which may equal or exceed colonies of spotted seatrout in bays. Annual exchange of spotted seatrout between bays, derived from a one-dimensional stepping stone model and estimated to be 5% of the breeding population, is compatible with previous movement data. Red drum may show Gulf-wide panmixia, but too little is known about the migratory adults to propose an appropriate population model.

Climate change is increasing the occurrence and severity of marine hypoxia events worldwide. Hypoxia can impact marine fishes by constraining O 2 uptake and reducing the energy available for vital and non-vital functions. Here, we explored the hypothesis that the red drum ( Sciaenops ocellatus ) – an economically valuable species native to the coastal estuaries of the Gulf of Mexico – was capable of respiratory and metabolic plasticity that would mitigate the effects of hypoxia. Through a series of studies, we demonstrated that juvenile red drum exposed to hypoxia for up to 42 days exhibited significant plasticity that improved oxygen uptake affinity, tissue oxygen utilization efficiency and anaerobic capacity. Specifically, red blood cells exhibited dynamic transcriptional regulation of specific hemoglobin isoforms that correlated with reduced pH sensitivity and an overall increase in oxygen affinity. Furthermore, red muscle mitochondria exhibited improved OXPHOS control ratios and control efficiency, effectively allowing a greater amount of ATP to be generated per unit oxygen. These findings coincided with reduce hypoxia vulnerability (i.e. reduced critical oxygen thresholds) and higher maximum metabolic rates when tested in hypoxia, as well as a significant increase in anaerobic burst swimming capacity. Interestingly, there was no improvement in maximum metabolic rate when tested in normoxia. This is consistent with the notion that oxygen supply capacity reaches a plateau at higher oxygen tensions – a finding validated here for red drum by employing a hyperoxia exposure during maximum metabolic rate determination. Interestingly, embryonic red drum exposed to hypoxia during the first 72 hours post-fertilization and then reared to post-metamorphosis in normoxia also exhibited significant respiratory plasticity, but of an opposing nature. Contrary to expectations, hypoxia exposed embryonic fish showed compromised hypoxia vulnerability and elevated maximum metabolic rate when tested in normoxic environments, indicative of improved capacity for oxygen transport and utilization coincident with reduced respiratory system affinity. Overall, these data suggest that coastal marine species that commonly experience hypoxic events, such as red drum, have the capacity for respiratory plasticity that can mitigate the effects of hypoxia. However, the significance of this plasticity and how it can shape organismal outcomes can differ based on life stage. Funding for this work was provided by the National Science Foundation. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

The role of dietary polyunsaturated fatty acids (PUFAs) on the fatty acid composition of juvenile red drum Sciaenops ocellatus was investigated. Individuals (n = 435) were fed three natural diets (Gulf menhaden Brevoortia patronus, brown shrimp Farfantapenaeus aztecus and Atlantic brief squid Lolliguncula brevis) that had significantly different proximate composition, energy density and PUFA compositions for 40 days. Diets were characterized as containing: high lipid, high protein, high energy and low PUFA (fish‐based), low lipid, low protein, low energy, moderate PUFA (shrimp‐based), and low lipid, high protein, moderate energy and high PUFA levels (squid‐based), respectively. Specimens were collected at days 0, 5, 10, 20 and 40 to evaluate rate of dietary fatty acid composition in tissues. Two‐source mixing models were used to calculate dietary fatty acid accumulation in consumer tissues. Results indicated that juvenile red drum incorporated an average of 35% dietary PUFAs after 5 days. Although relative biomass and dietary proximate composition had an effect upon the dietary fatty acid contribution, red drum averaged 91% incorporation of the five most prevalent PUFAs [18 : 2 (n − 6), 20 : 4 (n − 6), 20 : 5 (n − 3), 22 : 5 (n − 3) and 22 : 6 (n − 3)] across all diets after 40 days. Growth varied as a function of diet and rates were higher for individuals fed the squid diet than those fed shrimp or fish diets primarily due to increased levels of protein and PUFAs [including 22 : 6 (n − 3); 25·8%] in the diet. Red drum fed squid exhibited the greatest increase in average dietary fatty acid contribution by day 5, a trend that continued for the duration of the experiment. Since PUFA composition in red drum was significantly influenced by diet in as few as 5 days and almost completely incorporated into body tissues after 40 days, results from this study support the premise that fatty acids (especially PUFAs) are promising dietary indicators and may be useful for future studies examining trophic relationships of estuarine and marine fishes.

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 226:143-156 (2002) - doi:10.3354/meps226143 Characterization of settlement patterns of red drum Sciaenops ocellatus larvae to estuarine nursery habitat: a stable isotope approach Sharon Z. Herzka*,**, Scott A. Holt, G. Joan Holt Marine Science Institute, University of Texas at Austin, 750 Channelview Drive, Port Aransas, Texas 78373, USA *Present address: Departmento de Ecología, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Ensenada, Baja California, México. E-mail: sherzka@cicese.mx **Mailing address: PO Box 434844, San Diego, California 92143-4844, USA ABSTRACT: A novel approach was used to study the settlement of red drum Sciaenops ocellatus larvae from the coastal Gulf of Mexico to a seagrass meadow in the Aransas Estuary, Texas, during an entire recruitment season (September through November 1999). Differences in the δ13C and δ15N of the food webs supporting red drum while in the planktonic and estuarine habitats were characterized and used to identify post-settlement individuals in the process of completing the isotopic shift between the planktonic and estuarine signatures (transitional larvae). An empirical model was used to estimate the rate of change in the isotopic composition of transitional red drum to back-calculate size at settlement (Lsett; mm standard length: SL) and time since settlement (Tsett; d). During the period of study, there were 4 to 5‰ differences in the δ13C and δ15N of planktonic larvae and ŒlargeŒ settlers that had equilibrated to estuarine food sources. Red drum captured simultaneously exhibited variability in Lsett and Tsett values, indicating that they had settled at a range of sizes and over several days. Examination of length-frequency distributions of Lsett estimates indicated that the smallest settlers were about 4 mm SL, peak size at settlement was 6 to 8 mm SL, and the largest settlers were 10 to 11 mm SL. Settlement dates derived from Tsett indicated that a brief settlement pulse occurred during the latter half of September and that new settlers appeared on a daily basis throughout October and early November. The relatively continuous settlement pattern suggests a consistent supply of potential settlers to the estuary. The approach used in this study provides a fine- scale temporal resolution for the examination of settlement patterns in marine fishes that exhibit a distinct habitat transition and consequent dietary shift during early life. KEY WORDS: Settlement · Fish larvae · Stable isotopes · Sciaenops ocellatus · Turnover Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 226. Online publication date: January 31, 2002 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2002 Inter-Research.

This study evaluated the effects of seven diets composed of natural feed components (chopped fish, shrimp, and squid) alone or in combination on the liver metabolite profile of juvenile red drum (Sciaenops ocellatus) cultured in a 24-tank recirculating aquaculture system over the course of 12 weeks using Nuclear Magnetic Resonance (NMR)-based metabolomics. Experimental diets included fish (F), shrimp (SH), squid (SQ), fish and shrimp (FSH), fish and squid (FSQ), shrimp and squid (SHSQ), fish, shrimp, and squid (FSHSQ). A commercial fishmeal-based pelleted diet was used as a control. Fish were fed isocalorically. Red drum liver samples were collected at five different time points: T0, before the start of the trial (n = 12), and subsequently every 3 weeks over the course of 12 weeks (T3, T6, T9, T12), with n = 9 fish/diet/time point. Polar liver extracts were analyzed by NMR-based metabolomics. Multivariate statistical analyses (PCA, PLS-DA) revealed that red drum fed the F diet had a distinct liver metabolite profile from fish fed the other diets, with those fed SH, SQ and the combination diets displaying greater similarities in their metabolome. Results show that 19 metabolites changed significantly among the different dietary treatments, including amino acids and amino acid derivatives, quaternary amines and methylamines, carbohydrates and phospholipids. Specifically, γ-butyrobetaine, N-formimino-L-glutamate (FIGLU), sarcosine and beta-alanine were among the most discriminating metabolites. Significant correlations were found between metabolites and six growth performance parameters (final body weight, total length, condition factor, liver weight, hepatosomatic index, and eviscerated weight). Metabolites identified in this study constitute potential candidates for supplementation in fish feeds for aquaculture and optimization of existing formulations. Additionally, we identified a quaternary amine, γ-butyrobetaine as a potential biomarker of shrimp consumption in red drum. These results warrant further investigation and biomarker validation and have the potential for broader applicability outside of the aquaculture field in future investigations in wild red drum populations and potentially other carnivorous marine fishes.

Abstract. Quang NN, Anh NDQ, Linh NTH, Venturini C, Samsing F, Phuoc NN. 2026. Virulence traits and gene profiles of Vibrio alginolyticus from farmed red drum in Vietnam. Biodiversitas 27 (1): d270145. https://doi.org/10.13057/biodiv/d270145. Vibrio alginolyticus is an emerging bacterial pathogen associated with hemorrhagic disease and mortality in red drum (Sciaenops ocellatus) and other marine fish species. This study investigated virulence phenotypes and virulence-associated gene profiles of V. alginolyticus isolates infecting red drum, which is strain-dependent and reflects the combined expression of multiple phenotypic traits rather than the presence of individual virulence genes alone. Twenty V. alginolyticus isolates obtained from diseased red drum farmed in Hue City, central Vietnam, were evaluated for swimming motility, extracellular enzyme activity, and biofilm formation, and a composite virulence score was calculated using min-max normalized phenotypic data. Based on these scores, ten high-ranking isolates were selected for PCR screening of sixteen virulence-associated genes. Marked phenotypic variability was observed among isolates, with motility and extracellular enzyme activity contributing most strongly to virulence differentiation, whereas biofilm formation was generally weak to moderate. Fifteen genes were detected, including flagellar and motility-related genes (flaA, flaC, flgE, flrA, flrB, flrC, and flaK), hemolysin-related genes (trh and tlh), an adhesion gene (tcpA), secretion system components (vopB, vopD, and vgrG), and iron-acquisition genes (pvuA and pvsA), whereas tdh was not detected. Among the isolates, VA15 and VA17 exhibited the highest motility and extracellular enzyme activities, while most isolates formed weak but detectable biofilms. Pathogenicity testing confirmed that isolate VA15, identified as the most virulent based on in vitro profiling, caused dose-dependent mortality in red drum, with an LD50 of 4.0 × 104 CFU/fish (95% CI: 3.2 × 104-5.1 × 104 CFU/fish). Overall, this study provides baseline phenotypic and molecular data on V. alginolyticus infecting farmed red drum in central Vietnam and contributes to understanding virulence variability among isolates in marine cage aquaculture systems.

Various cottonseed products containing higher levels of protein and lipid than traditional cottonseed meal have been evaluated in recent years with several carnivorous marine fish species. In previous studies in this laboratory, distinct differences in the acceptability of diets containing those cottonseed products were noted for red drum and hybrid striped bass. Therefore, the present study consisted of two concurrent feeding trials in which the effects of increasing levels of dietary cottonseed oil were evaluated with both juvenile red drum and hybrid striped bass. Three experimental diets were formulated to contain either 0, 2, or 4% of cottonseed oil in place of menhaden fish oil. All diets were formulated to contain approximately 9% lipid, with that of the basal diet (0% cottonseed lipid) primarily contributed by menhaden fishmeal and menhaden oil. In concurrent trials, each diet was fed twice a day to triplicate groups of juvenile red drum and hybrid striped bass initially averaging 1.86 g/fish and 1.41 g/fish, respectively, for 6 weeks. Results of the feeding trial showed that there were no significant differences among red drum fed the different dietary treatments based on growth parameters (weight gain and feed efficiency) or whole-body proximate composition. On the contrary, hybrid striped bass showed significant ( P ≤ 0.05 ) differences in responses to the dietary treatments with weight gain decreasing as the inclusion levels of cottonseed oil increased while their hepatosomatic index significantly increased. Thus, results of this study showed distinctly different responses of red drum and hybrid striped bass to increasing levels of dietary cottonseed oil, with hybrid striped bass being much more sensitive than red drum in terms of reduced weight gain and altered body condition which appeared to be related to reduce diet palatability from cottonseed oil.