The red drum (Sciaenops ocellatus) is important for recreational fishing and aquacultural production in Texas' coastal waters and elsewhere in the nearshore Gulf of Mexico and in subtemperate to subtropical areas of the western North Atlantic Ocean. I performed indoor-tank and outdoor-pond experiments, in conjunction with automa ted respirometry and ecophysiological modeling, to assess interacting effects of temperature, dissolved-oxygen concentration (DO) and feed energy density on survival, growth, metabolism, and other measures of juvenile red drum performance. The main objective was to test an energy/metabolism tradeoff hypothesis, which states that growth of fish exposed to high temperatures can be limited by available feed energy; whereas, growth of fish exposed to lower temperatures can be limited by their metabolic capacity to exploit available feed energy. Also, I examined the influence of DO on this relationship and evaluated the effects of cyclical regimes of temperature and DO on fish performance. Insights from laboratory-based feeding trials were incorporated in experiments conducted in hatchery ponds to assess effects of oxygen supplementation and dietary additives - nucleotides and prebiotics - on performance in a more natural setting. In examining these issues, various technologies were developed. These included a computer-based apparatus for autonomously inducing cyclical regimes of temperature and DO in experimental tanks over an extended period of time. Additionally, I developed a soft feed with low energy-density to simulate natural forage. Experimental results supported the principal research hypothesis: At high temperature and DO, ecophysiological performance of juvenile red drum was enhanced by feeding to satiation with a high-energy feed (15.9 kJ/g) versus with a foragesimulating feed having lower energy density (4.1 kJ/g). Cyclical regimes of temperature and DO - as imposed in my particular laboratory experiments -did not impart growth benefits; however, the potential for enhanced growth via an appropriate cyclical environmental regime remains intact. Results from outdoor-pond experiments were consistent with laboratory results; however, the strong positive effect of feed energy density overwhelmed potential effects of dietary additives or oxygen supplementation on growth.

By-catch and wastes from processed fish and shrimp constitute a sizeable portion of commercial fishery landings. This discarded material is potentially valuable, for its content of fish meals and other substances. Fish meals, in particular, are increasingly in short supply for the manufacture of animal feeds, including feeds for farmed fish. Therefore, in this study, various by-catch and by-product meals of marine origin were evaluated with red drum (Sciaenops ocellatus), a carnivorous fish species native to the Gulf of Mexico that has been cultured over the past two decades for stock enhancement as well as for food. Four different kinds of by-catch or by-product meals [shrimp by-catch meal, shrimp processing waste meal, red salmon (Oncorhynchus nerka) head meal, and Pacific whiting (Merluccius productus) meal] were substituted for Special Select™ menhaden fish meal at two different levels (33% or 67% of crude protein) in prepared diets for red drum. Another treatment consisted of shrimp processing waste meal formulated on a digestible-protein basis to replace 33% of the protein from menhaden fish meal. Levels of calcium carbonate were reduced in two additional diets containing Pacific whiting, to evaluate the effects of ash content. Diets were formulated to contain 40% crude protein, 12% lipid, and 3.5 kcal digestible energy/g. Each diet was fed to triplicate groups of juvenile red drum in 38-l aquaria containing brackish water (7 ± 1 ppt) in two separate 6-week feeding trials. Survival, weight gain, feed efficiency, protein efficiency ratio and body composition responses were measured in each trial. Fish fed the by-catch meal at either level of substitution performed as well as fish fed the control diet containing protein solely from menhaden fish meal; whereas, fish fed the shrimp processing waste meal diets did significantly (P ≤ 0.05) worse than the controls, even when fed a diet formulated to be equivalent on a digestible-protein basis. Fish fed the red salmon head meal diet fared poorly, probably owing to an excessive amount of lipid in the diet that tended to become rancid. Overall, by-catch meal associated with shrimp trawling appears to be a very suitable protein feedstuff for red drum.

The expansion of aquaculture has increased demand for fishmeal supplies around the world; this, in turn, has resulted in dramatic increases in the cost of fishmeal, which has sparked interest in alternative feedstuffs. The development of new processing technologies, as well as the expanding generation of by-products from ethanol production has resulted in the development of novel protein sources that have the potential for replacing fishmeal in aquafeeds. The present study assessed the nutritional value of soy protein concentrate (SoyPC), barley protein concentrate (BarPC) and corn protein concentrate (CornPC) in the diet of red drum. Three sequential feeding trials were conducted; in these 50%, 75%, or 90% of the protein provided by Special SelectTM menhaden fishmeal in the reference diet was replaced with either SoyPC, BarPC, or CornPC in isonitrogenous (40% CP), isoenergetic (3.1kcal g-1) diets. Red drum with an average weight of 2.5 g, 1.6 g, and 1.5 g for trials 1, 2, and 3, respectively, were stocked in a recirculating system and fed twice daily at a rate approaching apparent satiation for 6 to 8 weeks. Along with the substitution of the selected plant feedstuffs, supplementation of DL-methionine and L-lysine was provided to exceed the established requirements of red drum for lysine and methionine, and glycine was added for palatability. Performance parameters of weight gain, feed efficiency, survival, hepatosomatic index, intraperitoneal fat ratio, and apparent digestibility coefficients for protein along with proximate composition of whole-body tissues were determined in the various trials. Results showed that 50% replacement of fishmeal protein by each of the protein concentrates produced fish performance, condition indices, and whole-body composition similar to those produced by the reference diet. However, replacing 75% and 90% of fishmeal protein with each of the plant protein concentrates reduced fish performance but not as severely as replacing all of the fishmeal protein with equal (33%) contributions from SoyPC, BarPC, and CornPC. Contrarily, these dietary substitutions did not reduce the apparent protein digestibility of the experimental diets. Based on the various results of this study, SoyPC, BarPC, and CornPC can readily replace 50% of the protein provided by menhaden fishmeal without adversely affecting the performance of cultured red drum.

By-catch and wastes from processed fish and shrimp constitute a sizeable portion of commercial fishery landings. This discarded material is potentially valuable, for its content of fish meals and other substances. Fish meals, in particular, are increasingly in short supply for the manufacture of animal feeds, including feeds for farmed fish. Therefore, in this study, various by-catch and by-product meals of marine origin were evaluated with red drum (Sciaenops ocellatus), a carnivorous fish species native to the Gulf of Mexico that has been cultured over the past two decades for stock enhancement as well as for food. Four different kinds of by-catch or by-product meals [shrimp by-catch meal, shrimp processing waste meal, red salmon (Oncorhynchus nerka) head meal, and Pacific whiting (Merluccius productus) meal] were substituted for Special Select™ menhaden fish meal at two different levels (33% or 67% of crude protein) in prepared diets for red drum. Another treatment consisted of shrimp processing waste meal formulated on a digestible-protein basis to replace 33% of the protein from menhaden fish meal. Levels of calcium carbonate were reduced in two additional diets containing Pacific whiting, to evaluate the effects of ash content. Diets were formulated to contain 40% crude protein, 12% lipid, and 3.5 kcal digestible energy/g. Each diet was fed to triplicate groups of juvenile red drum in 38-l aquaria containing brackish water (7 ± 1 ppt) in two separate 6-week feeding trials. Survival, weight gain, feed efficiency, protein efficiency ratio and body composition responses were measured in each trial. Fish fed the by-catch meal at either level of substitution performed as well as fish fed the control diet containing protein solely from menhaden fish meal; whereas, fish fed the shrimp processing waste meal diets did significantly (P ≤ 0.05) worse than the controls, even when fed a diet formulated to be equivalent on a digestible-protein basis. Fish fed the red salmon head meal diet fared poorly, probably owing to an excessive amount of lipid in the diet that tended to become rancid. Overall, by-catch meal associated with shrimp trawling appears to be a very suitable protein feedstuff for red drum.

While substantial progress has been made in replacing live prey with artificial diets in the feeding of marine fish larvae, it still remains impossible to successfully rear larvae on artificial diets without some period of co-feeding live prey or algae. This study investigated the presence and role of the gastrointestinal hormone cholecystokinin (CCK) in the red drum (Sciaenops ocellatus) to gain a better understanding of the factors limiting the utilization of artificial diets by red drum larvae. Work with other fish species has shown that CCK is the principal hormone which regulates the release of pancreatic enzymes into the gut lumen and emphasizes the potential importance of CCK in early red drum larvae. This work investigated the hypothesis that some signal present in the live prey or algae stimulates CCK and thereby initiates the digestive process in the larvae. First, the nucleotide and amino acid sequence of the putative red drum cholecystokinin precursor was determined and the development of CCK immunoreactive cells was examined. This work showed that red drum CCK is highly similar to CCK in other vertebrates and can be detected in the digestive tract of larval red drum within three days after the initiation of exogenous feeding. Next; postprandial trypsin, CCK, and CCK mRNA responses were quantified in red drum juveniles and larvae over a three hour period. Both CCK and trypsin were increased within thirty minutes following feeding while CCK mRNA levels were increased within the next two to three hours. Finally, the trypsin, CCK, and CCK mRNA responses of red drum larvae to homogenates of live prey and algae were examined. Homogenized rotifers appeared to be sufficient to induce both the CCK and trypsin responses in larval red drum. These results suggest that in addition to other factors, some component of live prey may initiate the release of CCK and prime the digestive process. Understanding these factors and their effects in early larvae may allow us to formulate and produce a prepared diet which will support growth and survival to metamorphosis equal to that provided by live feeds. / text

Bayou St. John is a degraded water-body located within the City of New Orleans and is the focus of restoration efforts. I tested the ability of reintroduced red drum (Sciaenops ocellatus) to survive in this system and assessed their habitat use and behavior. I tracked 29 red drum fitted with external acoustic radio transmitters to determine if they could survive the degraded habitats and determine their general dispersion within the Bayou. All 29 tagged red drum exhibited post-stocking movement (i.e., survival) and occurred primarily in the northern section of the Bayou (nearest Lake Pontchartrain). To assess habitat use and behavior on a finer scale, a second group of 19 red drum were internally tagged with VEMCO transmitters and movements monitored by four remote receivers. These fish exhibited behavior similar to red drum in natural habitats. Monthly movements changed as temperatures changed but were not influenced by diurnal differences, salinity, or conductivity.

Post-release survival of hatchery fishes is imperative to the success of any supplemental stocking program. The purpose of this research was to identify differences between hatchery and wild red drum (Sciaenops ocellatus) and determine if pre-release exposure techniques improve survival of hatchery individuals. Objectives were to contrast survival skills of hatchery and wild red drum from different locations, and examine if exposure to natural stimuli (e.g., habitat, predators, live prey) enhances survival skills in naïve hatchery red drum. Laboratory trials using high-speed videography (250 frames per second, fps) and field mesocosm experiments were used to investigate differences in prey-capture (e.g., attack distance, mean attack velocity, capture time, maximum gape, time to maximum gape, gape cycle duration, and foraging behaviors) and anti-predator performance (e.g., reaction distance, response distance, maximum velocity, time to maximum velocity, mean acceleration, and maximum acceleration) of hatchery and wild red drum. Results indicated that anti-predator performance measures differed significantly between hatchery and wild red drum. Variability in prey-capture and anti-predator performance for hatchery and wild red drum was high (CV range: 5.6 – 76.5%), and was greatest for hatchery fish for the majority of performance variables tested. Exposure to habitat (Spartina alterniflora marsh) did not appear to afford any obvious survival benefits to hatchery red drum, although survival skills did vary according to ontogenetic stage. Hatchery red drum exposed to natural predators (pinfish, Lagodon rhomboides) exhibited significantly greater attack distances during feeding events, and anti-predator performance variables were 20 – 300% in these individuals versus naïve red drum. In predation experiments with free-ranging pinfish predators, mortality rates (Z) ranged from 0.047 – 0.060 h-1 · predator-1; however no significant differences in mortality were found between fish reared with and without predators. Hatchery red drum reared on live prey (Artemia franciscana, mysid shrimp) demonstrated enhanced prey-capture and foraging behaviors as well as anti-predator performance relative to fish reared on artificial (pellet) diets. Findings of this research indicate that several behavioral patterns differed between hatchery and wild red drum; however, these differences can be mediated through the use of various pre-release exposure techniques.

Post-release survival of hatchery fishes is imperative to the success of any supplemental stocking program. The purpose of this research was to identify differences between hatchery and wild red drum (Sciaenops ocellatus) and determine if pre-release exposure techniques improve survival of hatchery individuals. Objectives were to contrast survival skills of hatchery and wild red drum from different locations, and examine if exposure to natural stimuli (e.g., habitat, predators, live prey) enhances survival skills in naïve hatchery red drum. Laboratory trials using high-speed videography (250 frames per second, fps) and field mesocosm experiments were used to investigate differences in prey-capture (e.g., attack distance, mean attack velocity, capture time, maximum gape, time to maximum gape, gape cycle duration, and foraging behaviors) and anti-predator performance (e.g., reaction distance, response distance, maximum velocity, time to maximum velocity, mean acceleration, and maximum acceleration) of hatchery and wild red drum. Results indicated that anti-predator performance measures differed significantly between hatchery and wild red drum. Variability in prey-capture and anti-predator performance for hatchery and wild red drum was high (CV range: 5.6 – 76.5%), and was greatest for hatchery fish for the majority of performance variables tested. Exposure to habitat (Spartina alterniflora marsh) did not appear to afford any obvious survival benefits to hatchery red drum, although survival skills did vary according to ontogenetic stage. Hatchery red drum exposed to natural predators (pinfish, Lagodon rhomboides) exhibited significantly greater attack distances during feeding events, and anti-predator performance variables were 20 – 300% in these individuals versus naïve red drum. In predation experiments with free-ranging pinfish predators, mortality rates (Z) ranged from 0.047 – 0.060 h-1 · predator-1; however no significant differences in mortality were found between fish reared with and without predators. Hatchery red drum reared on live prey (Artemia franciscana, mysid shrimp) demonstrated enhanced prey-capture and foraging behaviors as well as anti-predator performance relative to fish reared on artificial (pellet) diets. Findings of this research indicate that several behavioral patterns differed between hatchery and wild red drum; however, these differences can be mediated through the use of various pre-release exposure techniques.

High feed costs and increasing demand for fishmeal have intensified the search for alternative protein sources which are needed to allow world aquaculture to continue expanding. A severely underused marine resource is processing wastes of various types of seafood, which are often disposed of at great cost. Therefore, this study was conducted to evaluate three different types of seafood processing wastes as potential feed ingredients for the red drum (Sciaenops ocellatus). The three processing wastes evaluated were heads and shells from Penaeid shrimp, and viscera and skeletal remains from filleted black drum (Pogonias cromis) and channel catfish (Ictaluras punctatus). These wastes were blended with soybean meal in a 40:60 ratio, dry extruded and dried to produce stable ingredients. All three byproduct meals produced had crude protein levels ranging from 45 to 50 percent. Two feeding trials were conducted to evaluate the different processing waste byproduct meals in comparison to menhaden fishmeal. A digestibility trial was conducted with sub-adult red drum which led to the computation of apparent digestibility coefficients (ADCs) for organic matter, protein, lipid and energy for each of the byproduct meals. Each byproduct meal had relatively high ADC values that were generally similar to those of menhaden fishmeal. A comparative growth trial with red drum was then conducted in which experimental diets were formulated with the three byproduct meals replacing menhaden fishmeal on an equal-digestible-protein basis at levels of 65 percent, 80 percent, or 95 percent. Juvenile red drum were fed the various diets for 8 weeks in a brackish (6 plus/minus 1 ppt) water recirculating system after which weight gain, survival, feed efficiency, as well as whole-body proximate composition and condition indices were measured. All three of the byproduct meals could replace up to 65 percent of the protein provided by fishmeal without adversely affecting performance of red drum. However, the shrimp byproduct consistently provided the highest performance values at 80 percent replacement. The catfish byproduct yielded the lowest fish performance at all levels. This study indicates that dry extrusion of seafood processing wastes can be used to replace a considerable amount of fishmeal in feeds for red drum.

Thyrotropin (TSH) is a glycoprotein hormone released from the pituitary gland to promote the synthesis and secretion of thyroid hormone. The existence of well-established peripheral mechanisms for regulation of thyroid hormone delivery to targets has called into question the significance of TSH as a primary regulator of circulating thyroid hormone concentrations in fish. However, relatively little is known about the regulation or action of endogenously secreted teleost TSH, largely due to lack of purified TSH suitable for biological testing and immunoassay development. I developed a red drum in vivo bioassay to aid in the production and purification of recombinant TSH from the red drum, a perciform fish demonstrating dynamic daily thyroxine (T4) cycles hypothesized to be driven by TSH. Exogenous bovine TSH injection resulted in a time and dose-dependent increase in circulating TSH and T4 in red drum. However, the sensitivity of the red drum thyroid gland to stimulation by bovine TSH was lost during growth under controlled laboratory conditions, even when circulating levels of exogenously-administered mammalian TSH remained elevated. The insensitivity of the thyroid was not due to prior TSH injection or feed source. Because insensitivity of the Thyrotropin (TSH) is a glycoprotein hormone released from the pituitary gland to promote the synthesis and secretion of thyroid hormone. The existence of well-established peripheral mechanisms for regulation of thyroid hormone delivery to targets has called into question the significance of TSH as a primary regulator of circulating thyroid hormone concentrations in fish. However, relatively little is known about the regulation or action of endogenously secreted teleost TSH, largely due to lack of purified TSH suitable for biological testing and immunoassay development. I developed a red drum in vivo bioassay to aid in the production and purification of recombinant TSH from the red drum, a perciform fish demonstrating dynamic daily thyroxine (T4) cycles hypothesized to be driven by TSH. Exogenous bovine TSH injection resulted in a time and dose-dependent increase in circulating TSH and T4 in red drum. However, the sensitivity of the red drum thyroid gland to stimulation by bovine TSH was lost during growth under controlled laboratory conditions, even when circulating levels of exogenously-administered mammalian TSH remained elevated. The insensitivity of the thyroid was not due to prior TSH injection or feed source. Because insensitivity of the red drum thyroid precluded their use as a bioassay species, the plasma TSH and T4 response to exogenous TSH was next characterized in goldfish. The T4 response in goldfish was stable and repeatable, with T4 levels peaking at 5 hours and remaining elevated for more than 11 hours after bovine TSH injection. Plasma TSH peaked from 2-5 hours following TSH injection with more than 90 percent cleared by 11 hours. The goldfish bioassay was further utilized to evaluate the effects of structural modifications on TSH biological activity. Substitution of four positively charged amino acids at the n-recombinant human TSH, had the same effect in goldfish. The heterothyrotropic potency of mammalian follicle stimulating hormone in goldfish was also enhanced by the same amino acid substitutions. Finally, the importance of oligosaccharides to TSH bioactivity was also examined in goldfish. Deglycosylation abolished TSH bioactivity, even when immunoreactivity persisted in circulation. Furthermore, recombinant canine TSH was less potent when produced in cell lines generating insect-type glycosylation than when produced in a cell line capable of mammalian-type glycosylation. These studies utilizing recombinant mammalian demonstrated conservation of mammalian TSH hormone-receptor interactions in goldfish, suggesting TSH function might likewise be conserved. Thus, I have established goldfish as a sensitive and stable bioassay which can now be utilized to monitor the biological activity of teleost TSH expressed in vitro as well as to evaluate how structural modifications of the TSH molecule influence its vivo biological activity.