Peter J. Allen

Using Trace Elements in Pectoral Fin Rays to Assess Life History Movements in Sturgeon: Estimating Age at Initial Seawater Entry in Klamath River Green Sturgeon

Abstract To investigate the timing of the initial entry of green sturgeon Acipenser medirostris into seawater, we examined the ratios of strontium and barium to calcium in pectoral fin rays via laser ablation-inductively coupled plasma-mass spectrometry. In a reference group of six hatchery fish that was reared 1-2 years in freshwater and 1-3 years in seawater, we found a significant increase in the Sr:Ca ratio, a decrease in the Ba:Ca ratio, and an increase in the Sr:Ba ratio in calcified growth zones during the transition from freshwater to seawater. In 10 wild adults captured in the Klamath River, California, combined evaluation of the Sr:Ca and Ba:Ca ratios provided a clearer understanding of fish movements than the Sr:Ba ratio, probably because wild fish have a more complex life history. The Ba:Ca ratio dropped significantly between growth zones 1 and 2 (ages 0.5-1.5), indicating a transition into saline waters, such as the Klamath River estuary. The Sr:Ca ratio increased slightly in the same locatio...

Growth of larval to juvenile green sturgeon in elevated temperature regimes

Abstract To determine the effect of high river temperatures on post-yolk-sac larval to early juvenile green sturgeon Acipenser medirostris, growth rates at elevated and cycling temperature regimes were measured. Water temperatures were chosen based on temperature regimes in their highly altered natal rivers. Post-yolk-sac fish (15 d after hatching) were placed into twenty-four 60-L tanks. Fish were kept on a natural photoperiod, receiving continuous well water and aeration and ad libitum commercial rations. Significant differences were found between final wet weights, total lengths, and specific growth rates (at 24°C and at cycling 19–24°C > 19°C) because of increases in food consumption, despite increases in activity (both significantly greater at 24°C than at 19–24°C or 19°C). Elevated and cycling temperatures in the 19–24°C range do not adversely affect juveniles (body size range, ∼0.1–10 g), when abundant food and oxygen are available.

The effects of oil exposure on peripheral blood leukocytes and splenic melano-macrophage centers of Gulf of Mexico fishes

In August and November 2010 we collected and examined peripheral blood and tissues from three species of Gulf of Mexico fish. Findings were compared to non-exposed control fish. The leukocyte counts of exposed alligator gar were not significantly different from controls, while exposed Gulf killifish and sea trout had significantly decreased lymphocyte counts. Liver ethoxyresorufin-O-deethylase (EROD) values from sea trout were significantly greater than control sea trout EROD values, suggesting poly aromatic hydrocarbon exposure. Splenic melano-macrophage centers (MMCs) from exposed sea trout and Gulf killifish showed a significant increase in number compared to non-exposed fish. Sea trout splenic MMCs were also significantly greater in size. These findings suggest that Gulf fish sampled were exposed to crude oil from the Macondo well and were in a lymphopenic or immuno-compromised state.

Metabolic and locomotor responses of juvenile paddlefish Polyodon spathula to hypoxia and temperature.

Hypoxia is an increasing problem in the natural habitats that the paddlefish (Polyodon spathula) has historically inhabited, and a potential problem in managed culture conditions. However, the effects of hypoxia on paddlefish are not well understood. In order to understand the effects of hypoxia on juvenile paddlefish, acute hypoxia tolerance, aerobic metabolic rates and swimming capabilities were measured under normoxic (PO2 = 140-155 mm Hg) and hypoxic (PO2 = 62-70 mm Hg) conditions at 18 °C and 26 °C. The results showed that paddlefish acclimated to 18 °C and 26 °C had routine metabolic rates of 211 mg/kg/h and 294 mg/kg/h, respectively, with a corresponding Q10 of 1.5. At 18 °C and 26 °C, paddlefish had a critical partial pressure of oxygen (PO2crit) of 74 mm Hg and 89 mm Hg, respectively. Paddlefish had a lethal oxygen threshold of 31.0mm Hg and 37.0mm Hg at 18 °C and 26 °C, respectively. Further, paddlefish exhibited a reduction in swimming capability when exposed to hypoxia with a 24% and 41% decrease in Ucrit at 18 °C and 26 °C, respectively. Therefore, paddlefish are relatively sensitive to hypoxia, and at temperatures from 18 to 26 °C require a dissolved oxygen concentration ≥ 4.7 mg/L to maintain basal aerobic metabolism and >2.0mg/L to survive under acute hypoxia.

Influences of Cyclic, High Temperatures on Juvenile Channel Catfish Growth and Feeding

Abstract Effects of high summer temperatures on Channel Catfish Ictalurus punctatus are poorly understood, particularly for thermal regimes that mimic pond aquaculture conditions. Therefore, this study examined the effects of three cycling upper-range temperature regimes (23–27°C, 27–31°C, and 31–35°C) characteristic of aquaculture environments in the Mississippi Delta. Feed conversion ratio, feed consumption, specific growth rate, activity levels, survival, and overall growth in terms of wet weight and TL were measured in fingerling channel catfish over an 8-week period in a flow-through, multiple-tank system. Specific growth rate, feed consumption, TL, and wet weight of fish increased significantly in the 27–31°C treatment in contrast to the 23–27°C and 31–35°C treatments. Feed conversion ratio was lowest in the 27–31°C treatment, whereas activity levels were highest in the 31–35°C treatment. Survival significantly decreased for catfish in the warmest treatment compared with catfish in the coolest treat...

Using 1-D 1H and 2-D 1H J-resolved NMR metabolomics to understand the effects of anemia in channel catfish (Ictalurus punctatus)

Anemia is a widespread hematological disorder in vertebrates. In channel catfish (Ictalurus punctatus), anemia is a persistent problem in culture environments, however, its causes and physiological impacts are not well understood. To better understand the symptoms and characterize associated biomarkers of anemia, 1-D 1H and 2-D 1H J-resolved NMR were used to analyze metabolite changes in healthy and anemic channel catfish kidney and liver tissue. Additionally, standard physiological analytical techniques were used to analyze blood plasma. NMR analyses revealed energy sources such as glucose were depleted and many metabolites associated with anaerobic metabolism or alternative energy pathways such as lactate, creatine, alanine, acetate and myo-inositol had changed. Energy demanding processes were reduced, such as muscle function, as indicated by reductions in taurine and inosine, and protein synthesis. Stress and oxidative stress related metabolites changed, with increases in valine, leucine and isoleucine and decreases in glutathione. Inhibitory neurotransmitters such as 4-aminobutyric acid (GABA) increased, and excitatory neurotransmitters such as glutamine and glutamate generally decreased, although there were tissue-specific differences. Immune function also decreased in anemic fish. Blood analyses revealed decreased respiratory gas transport capabilities through reductions in erythrocytes and hemoglobin-markers. Taken together, these tissues and analytical techniques produced complementary results, and metabolite expression in anemic channel catfish was similar to that observed in other vertebrates exposed to anoxia, severe hypoxia or experiencing oxidative stress from deficiencies in iron homeostasis.

Critical Thermal Maxima of Two Geographic Strains of Channel and Hybrid Catfish

AbstractCritical thermal maxima have been used extensively to provide physiologically and ecologically valuable reference points that identify early signs of thermal stress. In catfish pond culture, daily temperature maxima up to 36°C and daily fluctuations of as much as 6°C are observed. These extreme conditions will probably be exacerbated by the effects of global climate change. Channel Catfish Ictalurus punctatus have a broad natural distribution from southern Canada to northern Mexico. If regional genetic differences could cause strains with a southern distribution to have greater thermal tolerance than strains with a northern distribution, and consequently a greater critical thermal maximum, then hybrid catfish (Channel Catfish × Blue Catfish I. furcatus) strains might be expected to have greater critical thermal maxima than their respective Channel Catfish strains because Blue Catfish have a more southern range of distribution. To examine this, we quantified differences of acute thermal tolerance i...

The influence of environmental calcium concentrations on calcium flux, compensatory drinking and epithelial calcium channel expression in a freshwater cartilaginous fish.

Calcium metabolism and mRNA levels of the epithelial calcium channel (ECaC) were examined in a freshwater cartilaginous fish, the lake sturgeon Acipenser fulvescens. Lake sturgeon were acclimated for ≥2 weeks to 0.1 (low), 0.4 (normal) or 3.3 (high) mmol l–1 environmental calcium. Whole-body calcium flux was examined using 45Ca as a radioactive marker. Net calcium flux was inward in all treatment groups; however, calcium influx was greatest in the low calcium environment and lowest in the high calcium environment, whereas efflux had the opposite relationship. A significant difference in the concentration of 45Ca in the gastrointestinal tract (GIT) of fish in the low calcium environment led to the examination of drinking rate and calcium flux across the anterior-middle (mid) intestine. Drinking rate was not different between treatments; however, calcium influx across the mid-intestine in the low calcium treatment was significantly greater than that in both the normal and high calcium treatments. The lake sturgeon ECaC was 2831 bp in length, with a predicted protein sequence of 683 amino acids that shared a 66% identity with the closest sequenced ECaCs from the vertebrate phyla. ECaC mRNA levels were examined in the gills, kidney, pyloric caeca, mid-intestine and spiral intestine. Expression levels were highest in the gills, then the kidneys, and were orders of magnitude lower in the GIT. Contrary to existing models for calcium uptake in the teleost gill, ECaC expression was greatest in high calcium conditions and kidney ECaC expression was lowest in low calcium conditions, suggesting that cellular transport mechanisms for calcium may be distinctly different in these freshwater cartilaginous fishes.

Effects of salinity on growth and ion regulation of juvenile alligator gar Atractosteus spatula

The alligator gar (Atractosteus spatula) is a primitive euryhaline fish, found primarily in estuaries and freshwater drainages associated with the northern Gulf of Mexico. The extent of its hypo-osmotic regulatory abilities is not well understood. In order to determine how salinity affects growth rates and ionic and osmoregulation, juvenile alligator gar (330 days after hatch; 185 g) were exposed to 4 different salinities (0, 8, 16, and 24 ppt) for a 30-day period. Specific growth rate, plasma osmolality and ion concentrations, gill and gastrointestinal tract Na(+), K(+)-ATPase activities, and drinking rate were compared. Juvenile alligator gar were able to tolerate hyperosmotic salinities up to 24 ppt for a 30 day period, albeit with decreased growth resulting largely from decreased food consumption. Plasma osmolality and ionic concentrations were elevated in hyperosmotic salinities, and drinking rates and gastrointestinal tract Na(+), K(+)-ATPase activities increased, particularly in the pyloric caeca, presumably the primary location of water absorption. Therefore, juvenile alligator gar<1 year of age are capable of prolonged exposure to hyperosmotic salinities, but, based on the inference of these data, require access to lower salinities for long-term survival.

Tissue PAH, blood cell and tissue changes following exposure to water accommodated fractions of crude oil in alligator gar, Atractosteus spatula.

Alligator gar Atractosteus spatula acclimated to brackish water (9 ppt) were exposed to water accommodated fraction oil loadings (surrogate to Macondo Deepwater Horizon, northern Gulf of Mexico) of 0.5 and 4.0 gm oil/L tank water for 48 h. The surrogate oil was approximately 98% alkanes and alkynes and 2% petroleum aromatic hydrocarbons. The 2% petroleum aromatic hydrocarbons were predominately naphthalene. After 48 h, naphthalene levels in fish liver exposed to 0.5 or 4 gm oil/L were 547.79 and 910.68 ppb, while muscle levels were 214.11 and 253.84 ppb. There was a significant decrease in peripheral blood lymphocyte numbers and a significant reduction of granulocytes in the kidney marrow of the same fish. Tissue changes included hepatocellular vacuolization and necrosis, necrotizing pancreatitis, renal eosinophilia, and splenic congestion. After 7 days recovery, liver naphthalene levels decreased to 43.59 and 43.20 ppb, while muscle levels decreased to 9.74, and 16.78 ppb for oil exposures of 0, 0.5 or 4 g/L. In peripheral blood and kidney marrow, blood cell counts returned to normal. The severity of liver and kidney lesions lessened after 7 days recovery in non-oiled water, but splenic congestion remained in all gar.