Luke A. Roy

Biochemical effects of petroleum exposure in hornyhead turbot (Pleuronichthys verticalis) exposed to a gradient of sediments collected from a natural petroleum seep in CA, USA

Concentrations of serum/plasma estradiol, biliary fluorescent aromatic compounds (FACs), levels of hepatic CYP1A expression, and DNA damage were measured in sexually mature hornyhead turbot (Pleuronichthys verticalis) exposed in the laboratory for 7 days to a gradient of sediments collected from a natural petroleum seep in the Santa Barbara Channel. Coal oil point (COP) sediments were homogenized and divided into four treatments containing 0 (sediment from the Orange County Sanitation Districts reference location), 33, 66, and 100% (COP) sediments. Sediment concentrations of 20 PAHs ranged from below the detection limit for the 0% COP sediment treatments to 105 microg/g in the 100% treatments with lower molecular weight compounds predominating. Concentrations of biliary FACs were not linear with COP treatment but levels of hepatic DNA damage increased linearly with increasing concentrations of high molecular weight PAHs. Hepatic CYP1A expression was elevated only in the 100% treatments. A reduction of plasma estradiol in male and female fish was observed in all COP exposures. These results demonstrate that acute sediment-only exposure of flatfish to naturally-derived PAHs elicits alterations in biochemical endpoints indicative of PAH bioavailability and adverse effects with different sensitivities.

Evaluating the Benefits of Size-Sorting Tilapia Fry Before Stocking

Abstract Size-grading is routinely practiced in fish hatcheries for reasons such as increased growth among small fish, reduction of cannibalism, decrease in size variability among harvested fish, and facilitated feeding; yet there is little information with regards to growth potential of sorted groups. Two growth trials were conducted with 30-day-old, size-sorted tilapia, to evaluate growth depensation and the influence of social interactions. In the first experiment, sibling juvenile tilapia were sorted into three size classes, small (2.6 g), medium (3.7 g), and large (4.9 g), and 15 fish were stocked into 60-L aquaria with three replicate aquaria per treatment. A fourth treatment (mixed) consisted of five fish from each size category stocked together. Diet was offered at 5% body weight per day over a 7-week growth trial. Average final weights of the fish at harvest were 13.3, 18.8, 27.0, and 24.7 g for small, medium, large and mixed treatments, respectively. Fish in the large treatment grew faster than fish in the medium treatment, which in turn grew faster than fish in the small treatment. Condition index of fish in the large treatment was significantly greater than in the small treatment (P < 0.05). In the second experiment sex-reversed juvenile tilapia were sorted and divided into small (0.9 g), medium (1.2 g), and large (1.5 g). Methods were as previously described except after eight weeks of culture, the tilapia were harvested and then transferred into larger tanks (150 L) to accommodate for their increased size. Average final weights after 13 weeks were 61.3, 78.8, 95.0, and 75.8 g for small, medium, large, and mixed treatments, respectively. Fish in the large treatment grew significantly faster (P < 0.05) than fish in the medium, small, and mixed treatments. Results suggest that size grading before stocking would improve commercial returns for farmers.

Pond demonstration of production diets using high levels of distiller's dried grains with solubles with or without lysine supplementation for channel catfish.

Abstract Due to the increased availability and potential price advantage of distillers dried grains with solubles (DDGS), there is considerable interest in utilizing this product in aquaculture diets. The response of channel catfish Ictalurus punctatus to practical diets containing 20% and 30% DDGS with and without lysine supplementation was evaluated over a 150-d pond trial. Twenty earthen ponds were stocked with 650 juvenile channel catfish. The basal diet contained 35% soybean meal, 15% cottonseed meal, and 23.7% corn meal and was based on a typical practical diet formulation for channel catfish. The experimental diets, which were formulated to contain 32% protein and 6% lipid, were as follows: diet 1 (control [basal] diet) contained 0% DDGS and 0% lysine; diet 2 included 20% DDGS and 0% lysine; diet 3 contained 20% DDGS and 0.10% lysine; diet 4 contained 30% DDGS and 0% lysine; and diet 5 included 30% DDGS and 0.20% lysine. There were no significant differences in the measured variables (i.e., final ...

Effect of Feeding Rate and Pond Primary Productivity on Growth of Litopenaeus vannamei Reared in Inland Saline Waters of West Alabama

Abstract Feeding costs have skyrocketed worldwide in the past several years, negatively impacting shrimp farmers. Typically, 50–60% of the production costs of shrimp farm operations are attributed to feed inputs. The increasing cost of feed combined with declining market prices for shrimp makes it difficult to maintain adequate profit margins. In west Alabama, shrimp farmers are located long distances from feed mills and pay high shipping fees in addition to high feed prices. These low-salinity waters are quite productive, providing natural food items throughout the production cycle. To determine the possibility of reducing feed rates by relying more on pond primary productivity to contribute to shrimp growth, four growth trials were conducted with juvenile Pacific white shrimp Litopenaeus vannamei (formerly known as Penaeus vannamei). Juvenile shrimp were offered different feed rates ranging from 0% (no feed) to 110% of a normal daily ration by means of static, flow-through, or partial daily water exchan...

Chelated Potassium and Arginine Supplementation in Diets of Pacific White Shrimp Reared in Low-Salinity Waters of West Alabama

Abstract Dietary supplements have been proposed as a potential remediation strategy to counteract mineral deficiencies in low-salinity well waters (LSWW) used for shrimp culture in Alabama. Existing strategies (i.e., application of fertilizers such as K-mag and muriate of potash) are costly to farmers attempting to raise levels of potassium (K+) in their ponds. Previous laboratory studies using dietary supplements of chelated K+ increased growth but not survival of Pacific white shrimp Litopenaeus vannamei reared in low-salinity water. To determine whether this approach is applicable in the field, two growth trials were conducted in flow-through outdoor tanks that used water from farm ponds. The first trial (6 weeks) was conducted simultaneously at two separate low-salinity farms in west Alabama and evaluated two practical diets, one with a chelated K+ supplement and one without. One of these farms supplements K+ to its water and is considered a low-stress environment (LSE), while the other farm does not ...

Research Verification of Production Practices Using Intensive Aeration at a Hybrid Catfish Operation

AbstractAquaculture research verification programs are designed to demonstrate and test research-based practices recommended by extension services on commercial-scale operations. From 2010 to 2013, in western Alabama, three management protocols were followed over three crop cycles on a farm producing hybrid catfish (female Channel Catfish Ictalurus punctatus × male Blue Catfish I. furcatus) using high levels of aeration. The protocols were an owner-defined, multiple-batch treatment and single-batch and multiple-batch treatments defined by the Alabama Cooperative Extension System (ACES). Results from nine production cycles were analyzed to calculate yields, feed conversion ratios (FCRs), cost of production, and net returns. Over three production cycles the owner-defined, multiple-batch treatment outperformed the two ACES-recommended treatments in terms of yield, survival, FCR, and net returns. The owner-defined treatment could vary, and the producer chose to feed above the recommended daily maximum and obs...