Browsing by Subject "Red drum"
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Item Defining the metabolic compensation pathways employed during low-level hypercapnia in red drum (Sciaenops ocellatus)(2015-08) Brown, Elizabeth Ann; Esbaugh, Andrew; Thomas, Peter; Walther, BenjaminSince the pre-industrial era, anthropogenic CO₂ emissions have raised oceanic CO₂ by 40% and reduced ocean pH by 0.1 unit. This results in acid-base disturbances in marine organisms that are compensated through regulatory pathways. Many estuarine fishes, including red drum (Sciaenops ocellatus), regularly encounter periods of elevated CO₂, which may impart a level of species resilience to ocean acidification. Initial studies examined the time course of whole animal acid-base compensation in response to varying CO₂ concentrations. Under control conditions red drum showed net base excretion; however, the onset of CO₂ exposures resulted in a dose-dependent increase in acid excretion during the initial 2h time period. Notably, net acid excretion returned to baseline levels by 4h of exposure of up to 5,000 μatm, but remained elevated throughout 15,000 and 30,000 μatm exposures. Subsequent studies assessed the plasticity of branchial acid-base pathways after exposure to various CO₂ levels using qPCR. 1,000 μatm exposed fish were sampled at 1h, 4h, 24h, 72h, and 14d, while 6,000 and 30,000 μatm exposed fish were sampled after 1h, 4h, and 24h of exposure. Of a suite of acid-base relevant genes, only the Na⁺ HCO₃⁻ co-transporter (NBC) was upregulated in 1,000 and 6,000 μatm treatments. In contrast, the majority of relevant genes were up-regulated by 4h of exposure to 30,000 μatm, with the exception of the electrogenic anion exchanger slc26a3a, which was only upregulated by 24h of exposure to 30,000 μatm. Cytoplasmic carbonic anhydrase and Na⁺ H⁺ exchanger 1 exhibited no change in expression to 30,000 μatm. Localization studies examined the position of the V-type H⁺ ATPase (VHA) within gill ionocytes. Under control conditions, VHA is diffusely distributed throughout the cytoplasm of the cell, although oriented toward the apical pole; there was no evidence of basolateral localization. Exposure to 6,000 μatm CO₂ did not result in translocation of cytoplasmic VHA to the apical membrane. Overall, these results indicate that red drum can quickly compensate to a wide range of environmentally relevant acid-base disturbances using baseline cellular machinery, yet are capable of acid-base plasticity in response to extreme challenges.Item Evaluation of the Nutritional Value of Seafood By-Product Blends with Red Drum Sciaenops Ocellatus and Hybrid Striped Bass Morone Saxatilis X M.Chysops(2014-05-06) Burns, Alton FDiets of many cultured fishes require high inclusion of fishmeal and fish oil. With the growth of aquaculture worldwide, demand for fishmeal and fish oil has increased resulting in higher prices of these ingredients due to increased demand but relatively static supplies. A promising source of alternative protein and lipid is the waste from seafood processing. This project evaluated four different types of seafood processing wastes as potential feed ingredients for the red drum (Sciaenops ocellatus) and hybrid striped bass (Morone saxatilis x M. chysops). Viscera and skeletal remains from filleted channel catfish (Ictalurus punctatus), black drum (Pogonias cromis), yellowfin tuna (Thunnus albacares) and krill (Euphausia superba) were evaluated with red drum and hybrid striped bass by determining nutrient and energy digestibility. Catfish, black drum, and tuna waste products were blended with soybean meal in a 40:60 ratio. All diets were subjected to dry extrusion, and then dried to produce stable ingredients. Diets used for the digestibility trial were formulated to contain 40% crude protein, 10% lipid and 1% chromic oxide as a marker, with each ingredient substituted in a reference diet at a 30:70 ratio. The yellowfin tuna fillet waste also was evaluated in a comparative feeding trial with juvenile red drum. In that trial, experimental diets with the tuna by-product meal replaced menhaden fishmeal on an equal protein basis at levels of 5, 10, 20, 40 or 60%. Diets were formulated to contain 40% crude protein and 12% lipid. Juvenile red drum were fed the various diets for 7 weeks in 38-L aquaria linked as a brackish (6 + 1 ppt) water recirculating system. Apparent digestibility coefficient (ADC) values for crude protein, crude lipid, and energy from krill and catfish meal were similar for red drum while the black drum meal had decisively lower values. Krill meal had higher ADC values for organic matter and energy than catfish meal and black drum meal in hybrid striped bass. ADC values of crude protein, and crude lipid were similar for krill, catfish, and black drum ingredients. Based on weight gain and feed efficiency responses in the feeding trial, red drum fed the control diet with only fishmeal significantly outperformed fish fed the tuna-substituted diets. However, no significant differences were observed among fish fed the diets with 5, 10, 20, or 40% tuna substitution. These results suggest that inclusion of seafood processing by-products can be substituted for fishmeal and possibly reduce the price of fish feeds.Item Intraspecific competition among early life stages and the optimal spawning strategy of red drum (Sciaenops ocellatus)(2009-12) Nakayama, Shinnosuke, 1978-; Fuiman, Lee A.; Thomas, Peter; Holt, Gloria J.; McClelland, James W.; Cummings, Molly E.This collection of studies was designed to understand the mechanisms and consequences of competition among early life stages of red drum (Sciaenops ocellatus), with a special attention to asymmetric competition and multiple-breeding strategy of parents. The overall hypotheses were that (1) red drum larvae show behavioral interactions, and the magnitude of these interactions is explained by the sizes of the competing individuals, (2) red drum larvae compete for food and habitat use, and the competition is asymmetric as determined by size and behavioral interactions, and (3) the parents can reduce negative effects of competition among larvae and increase larval survival by altering their multiple-spawning traits. The laboratory experiments showed the existence of sociality in red drum larvae. The magnitudes of aggressive behavior, vigilant behavior and shoaling behavior were explained by a combination of absolute and relative phenotypes of competing individuals, such as body lengths and body condition. A new method of combining the laboratory experiments and the foraging theory disentangled interference competition for food from exploitative competition, revealing that both absolute and relative body lengths of competing individuals influence feeding efficiencies. In addition, vigilant behavior decreased feeding efficiency regardless of body sizes. The competitor size and behavioral interactions between individuals had different effects on competition for habitat use: the existence of larger individuals prevented the newly settled larvae from entering preferred habitats, whereas the aggressive behavior from the occupants of preferred habitats moved newly settled larvae to the unpreferred habitats. Finally, computer simulations using an individual-based model revealed that as interference competition among larvae increased, the number of spawning events and the spawning interval of the parents increased to lessen competition and maximize total survival of offspring.Item Replacement of Fishmeal with Plant Feedstuffs in the Diet of Red Drum Sciaenops ocellatus: An Assessment of Nutritional Value(2012-07-16) Moxley, JosephThe 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.