Effects of rested-harvest using the anesthetic AQUI-S™ on channel catfish,Ictalurus punctatus,physiology and fillet quality

Trials were conducted to determine effects of AQUI-S™ sedation during harvest (rested-harvest) on physiological responses and fillet quality of channel catfish, Ictalurus punctatus. Rested-harvest is defined as application of an anesthetic immediately before harvest to reduce fish activity associated with a normal harvest. Doses of 25–35 ppm AQUI-S™ were effective for rested-harvest of catfish (loss of equilibrium in 3 to 10 min and 100% survival following recovery). Time to loss of equilibrium and time to recovery following sedation with 35 ppm AQUI-S™ increased as water temperature decreased from 30 °C to 10 °C. Catfish exposed to 25 ppm AQUI-S™, 35 ppm AQUI-S™, 100 ppm trincaine methanesulfonate, and 8 ppm metomidate had lower blood lactate, cortisol, and glucose and higher blood pH than unsedated fish exposed to a low-water stress. Rested-harvest (RH) catfish had higher muscle and blood pH, lower blood and muscle lactate, and higher muscle ATP levels than catfish exposed to a 45 min low-water stress. Rates of muscle pH decrease, ATP decrease, and lactate increase accelerated as storage temperature decreased from 15 °C to 5 °C in RH fish acclimated to summer temperatures (33 °C), conversely these rates accelerated as storage temperature increased from 5 °C to 15 °C in RH fish acclimated to winter temperatures (7 °C). Based on physiological response (higher muscle pH, lower blood lactate, delayed time to rigor), post-sedation euthanasia by CO₂ was superior to post-sedation euthanasia by AQUI-S™ overdose (150 ppm), nitrogen gas, or electrical stunning. Compared to fillets from fish exposed to simulated industry transport conditions, fillets from RH/CO₂ euthanised fish had higher pH 1 h post-slaughter, and less drip-loss and lower L^⁎ and a^⁎ color values during 7 days of iced storage. RH/CO₂ and control fillets were not different for shelf-life based on bacterial counts. Rested-harvest with AQUI-S™ followed by CO₂ euthanasia has potential to improve catfish fillet quality, but AQUI-S™ approval, development of rested-harvest strategies, and demonstration of economic benefits of rested-harvest will be required for adoption of rested-harvest to commercial catfish production.     

Optimizing Salting and Smoking of Catfish (Bagre marinus) Using Response Surface Methodology

ABSTRACT

Response surface methodology was used to assess the effects of brine concentration (0.1127–0.2473 g NaCl/g), salting time (49–271 min), smoking temperature (53.2–86.8°C), and smoking time (216–384 min) on moisture content, salt content, yield, taste preference, and texture preference of smoked catfish slices. Optimal process conditions were determined through the graphical method and desirability function approach. The desirability function showed that the optimal conditions for salting and smoking of catfish were: smoking temperature, 70°C; smoking time, 300 min; salting time, varying from 193.39 to 194.68 min; and brine concentration varying from 0.1791 to 0.1797 g NaCl/g. Under optimal conditions, moisture content, salt content, yield, taste preference, and texture preference of smoked catfish were 0.53 g water/g, 0.064 g NaCl/g, 58%, 3.7, and 3.7, respectively.     

Postmortem Biochemical and Microbiological Changes in Loricariid Catfish (Pterygoplichthys disjunctivus) Muscle During Ice Storage

ABSTRACT

Postmortem biochemical and microbiological changes in loricariid catfish (Pterygoplichthys disjunctivus) muscle were evaluated during ice storage for 20 days. Values of pH remained stable for 15 days (7.4 ± 0.2), and total volatile base-nitrogen (TVB-N) remained under acceptable limits throughout storage, with a final value of 25.2 ± 3.3 mg N/100 g muscle at Day 20. Adenosine-5´-triphosphate (ATP) and derivatives followed a postmortem degradation pattern similar to other species, with the K-value being the best freshness loss indicator. Biochemical and microbiological changes indicated that the shelf life of iced loricariid catfish muscle was 15 days under optimal (0°C) storage conditions.     

Effect of temperature on excess post-exercise oxygen consumption in juvenile southern catfish (<Emphasis Type="Italic">Silurus meridionalis</Emphasis> Chen) following exhaustive exercise

The effects of temperature on resting oxygen consumption rate (MO_2rest) and excess post-exercise oxygen consumption (EPOC) after exhaustive exercise (chasing) were measured in juvenile southern catfish (Silurus meridionalis) (8.40 ± 0.30 g, n = 40) to test whether temperature has a significant influence on MO_2rest, maximum post-exercise oxygen consumption rate (MO_2peak) and EPOC and to investigate how metabolic scope (MS: MO_2peak − MO_2rest) varies with acclimation temperature. The MO_2rest increased from 64.7 (10°C) to 160.3 mg O₂ h⁻¹ kg⁻¹ (25°C) (P < 0.05) and reached a plateau between 25 and 30°C. The post-exercise MO₂ in all temperature groups increased immediately to the peak values and then decreased slowly to a steady state that was higher than the pre-exercise MO₂. The MO_2peak did not significantly differ among the 20, 25 and 30°C groups, though these values were much higher than those of the lower temperature groups (10 and 15°C) (P < 0.05). The duration of EPOC varied from 32.9 min at 10°C to 345 min at 20°C, depending on the acclimation temperatures. The MS values of the lower temperature groups (10 and 15°C) were significantly smaller than those of the higher temperature groups (20, 25 and 30°C) (P < 0.05). The magnitude of EPOC varied ninefold among all of the temperature groups and was the largest for the 20°C temperature group (about 422.4 mg O₂ kg⁻¹). These results suggested that (1) the acclimation temperature had a significant effect on maintenance metabolism (as indicated by MO_2rest) and the post-exercise metabolic recovery process (as indicated by MO_2peak, duration and magnitude of EPOC), and (2) the change of the MS as a function of acclimation temperature in juvenile southern catfish might be related to their high degree of physiological flexibility, which allows them to adapt to changes in environmental conditions in their habitat in the Yangtze River and the Jialing River.     

Replacement of fish meal in juvenile channel catfish,Ictalurus punctatus,diets using a yeast‐derived protein source: the effects on weight gain,food conversion ratio,body composition and survival of catfish challenged with Edwardsiella ictaluri

We examined the effects of a yeast‐derived protein source (NuPro^®) as a replacement for menhaden fish meal on weight gain, specific growth rate (SGR), food conversion ratio (FCR), whole‐body composition and disease resistance in juvenile channel catfish (9.9 ± 0.2 g fish^?1). NuPro^® replaced fish meal at six levels (0, 25, 50, 75, 100 and 125 g kg^?1 diet). Catfish were sampled for whole‐body composition and then challenged with the bacterium Edwardsiella ictaluri. Growth performance was negatively affected (P < 0.01) when NuPro^® was added at 125 g kg^?1 diet. The amount of whole‐body fat decreased (P < 0.05) when NuPro^® was added at 75 g kg^?1 or more of the diet. Regardless of the amount of NuPro^® added, survival after challenge with E. ictaluri was similar among treatments. Results indicate that up to 100 g kg^?1 of NuPro^® can be added without negatively affecting growth performance. The yeast‐derived protein source used in this study is a sustainable protein alternative that could be used as a partial replacement for fish meal in juvenile channel catfish diets.     

Enzyme treatment for elimination of egg stickiness in tench (Tinca Tinca L.), European catfish (Silurus Glanis L.) and common carp (Cyprinus Carpio L.)

Enzyme treatment to eliminate egg stickiness in tench, European catfish and common carp was compared with standard methodology in an attempt to decrease time consuming under hatchery conditions. Eggs of tench and E. catfish were exposed to an alcalase enzyme MERCK EC 3.4.21.14 (0.6 AU g^?1) solution 3 min after egg fertilization for 2 min. The best enzyme concentration in tench and E. catfish was 10 and 20 ml l^?1 of enzyme, respectively. The eggs of c. carp were successfully destickiness with ALCALASE DX (2.5 AU g^?1) using two concentration of enzyme (2 ml l^?1 and 20 ml l^?1) from 8 to 20 min after fertilization.     

Evaluation of the short-term toxicity of nitrogenous compounds to channel catfish, Ictalurus punctatus

The acute toxicity of un-ionized ammonia, nitrite, and nitrate to 50–76-mm fingerling channel catfish (Ictalurus punctatus) was investigated using a static bioassay system at 22, 26 and 30°C. The 96-h LC50 values at 30°C for un-ionized ammonia, nitrite, and nitrate were 3.8, 44, and 6 200 mg/l.     

The effect of cryoprotectants on the motility and fertilizing capacity of cryopreserved African catfish Clarias gariepinus (Burchell 1822) sperm

The effect of six cryoprotectants was investigated on the cryopreservation of African catfish Clarias gariepinus (Burchell) sperm. Fructose (6%) solution buffered with NaHCO₃‐CO₂ was used as the diluent in the experiments. Glycerol (5–11%), ethylene glycol, methanol and propylene glycol (5–15%) and, finally, dimethyl sulphoxide (DMSO) and dimethylacetamide (DMA) (10%) were tested using various equilibration times (2–30 min). Sperm was frozen in 250‐μL straws in a programmable freezer (Cryocell‐15, BLS, Hungary) from 3 °C to ?4 °C at 4 °C/min and from ?4 °C to ?80°C at 11 °C/min. Thawing was carried out in a 40 °C water bath for 5 s. Fertilization and hatching trials were performed only with DMSO and DMA using 200 and 100 μL of diluted sperm (100 and 50 μL of pure sperm) and the dry and the wet fertilization methods. Ethylene glycol, glycerol, methanol and propylene glycol yielded poor results. An average post‐thaw motility rate of 44.0 ± 9.7% and 22.6 ± 18.1% was achieved after 10 min equilibration using DMSO and DMA respectively. Highest average fertilization (86.8 ± 3.1%) and hatching (67.1 ± 11.9%) rates were achieved with DMA and DMSO, respectively, 200 μL of diluted sperm and the wet fertilization technique. The use of cryoprotectants increased the percentage of malformed larvae compared with the control groups. We found that DMA at a 10% concentration was equally as suitable for the cryopreservation of African catfish sperm as DMSO.     

Virucidal effects of common disinfectants against tilapia lake virus

Tilapia lake virus (TiLV) is an emerging virus associated with high fish mortality and economic losses. This study investigates the virucidal effects of the following disinfectants (active ingredients) on TiLV: 2.5 ppm iodine, 10 ppm sodium hypochlorite (NaOCl), 300 ppm hydrogen peroxide (H₂O₂), 80 ppm formalin and 5,000 ppm (0.5%) Virkon^®. Factors that affect the disinfectants’ efficacy, including temperature, contact time and soiling (organic matter) interference, were examined under conditions mimicking natural aquaculture practices. TiLV inactivation of higher than 5 log₁₀ TCID₅₀ ml^?1 was achieved after 10 min and at 28°C for all disinfectants except formalin; similar inactivation levels were reached by NaOCl and Virkon^® at 10 min and 4°C. Extended exposure to formalin from 10 to 60 min at 28°C rendered more than 5 log₁₀ inactivation. Increasing synthetic organic matter in the water to mimic soiling interference reduced the efficacy of NaOCl, iodine and H₂O₂ when tested at 10 min and 28°C; however, Virkon^® still achieved more than 5 log₁₀ inactivation. This study demonstrates that most common disinfectants effectively reduced viral loads to minimum levels. To limit the spread of TiLV in aquaculture farms and related facilities, the appropriate use of such disinfectants should therefore be promoted and implemented.     

Water parameters affect anaesthesia induced by eugenol in silver catfish,Rhamdia quelen

The present study investigated the effects of water pH (5.0, 7.0 and 9.0), hardness (0, 20 and 120 mg CaCO₃ L^?1) and temperature (15, 23 and 30 °C) on the induction of sedation and anaesthesia, and subsequent recovery, of silver catfish exposed to eugenol. Moreover, the blood gas tensions (PvO₂ and PvCO₂) and blood pH in silver catfish acclimated to these temperatures were investigated after exposure to eugenol. Water pH, hardness, temperature and fish size affect the efficacy of eugenol in silver catfish, particularly at the lower concentrations tested (20 and 30 mg L^?1). Sedation of this species can be induced at concentrations as low as 20 mg L^?1, but for anaesthesia, a concentration of at least 40 mg L^?1 of eugenol must be used to compensate for the influence of fish size and water quality. Blood gas tension and pH were affected by eugenol anaesthesia, but only in fish acclimated to 30 °C.     

The effect of temperature on the resting and post-exercise metabolic rates and aerobic metabolic scope in shortnose sturgeon <Emphasis Type="Italic">Acipenser brevirostrum</Emphasis>

The effects of acclimation temperature (15, 20, 25 °C) on routine oxygen consumption and post-exercise maximal oxygen consumption rates (MO₂) were measured in juvenile shortnose sturgeon (Acipenser brevirostrum LeSueur, 1818). The routine MO₂ of shortnose sturgeon increased significantly from 126.75 mg O₂ h^?1 kg^?1 at 15 °C to 253.13 mg O₂ h^?1 kg^?1 at 25 °C. The temperature coefficient (Q ₁₀) values of the routine metabolic rates ranged between 1.61 and 2.46, with the largest Q ₁₀ values occurring between 15 and 20 °C. The average post-exercise MO₂ of all temperature groups increased to a peak value immediately following the exercise, with levels increasing about 2-fold among all temperature groups. The Q ₁₀ values for post-exercise MO₂ ranged from 1.21 to 2.12, with the highest difference occurring between 15 and 20 °C. Post-exercise MO₂ values of shortnose sturgeon in different temperature groups all decreased exponentially and statistically returned to pre-exercise (resting) levels by 30 min at 15 and 20 °C and by 60 min at 25 °C. The aerobic metabolic scope (post-exercise maximal MO₂-routine MO₂) increased to a maximum value ～156 mg O₂ h^?1 kg^?1 at intermediate experimental temperatures (i.e., 20 °C) and then decreased as the temperature increased to 25 °C. However, this trend was not significant. The results suggest that juvenile shortnose sturgeon show flexibility in their ability to adapt to various temperature environments and in their responses to exhaustive exercise.     

Catecholaminergic control of LH secretion: E2 modulation of tyrosine hydroxylase activity in female catfish Heteropneustes fossilis

Tyrosine hydroxylase (TH) which catalyses the rate – limiting step in catecholamine (CA) synthesis shows significant annual variations with activity and kinetics increasing with the progress of gonad recrudescence up to spawning and decreasing thereafter. Estradiol-17 β (E₂) exerts biphasic effects on in vivo and in vitro enzyme activity and kinetics: low dosages/concentrations stimulated, and high dosages/concentrations inhibited them. Preincubations of hypothalamic enzyme preparations with low (10^?9 M) or high (10^?3 M) E₂ for 15 min at 30 °C, followed by cAMP (1.0 mM) for 10 min at 30 °C produced differential effects: an additive effect in the low concentration group and an inhibitory response in the high concentration group. The stimulatory or inhibitory effects on TH activity could be related to changes in apparent K_m and V_max of the enzyme for substrate and cofactor. The results suggest that TH activity and kinetics are influenced by the circulating titer of E₂ and the steroid interacts with the cAMP signaling pathway in the acute regulation of TH.     

Improved digestibility of plant ingredient‐based diets for European seabass (Dicentrarchus labrax) with exogenous enzyme supplementation

This study evaluated the effect of supplementation of a plant ingredients‐based diet with two levels of commercially digestive enzyme products: Synergen? and Natugrain^® on the apparent digestibility coefficients (ADCs) of nutrients and on digestive enzyme activities in European seabass (Dicentrarchus labrax) juveniles. A control diet was formulated with 450 g/kg CP (200 g/kg from fish meal + 800 g/kg from plant protein) and 180 g/kg CL (fish oil), and four other diets were made similar to the control but supplemented with 0.2 g/kg or 0.4 g/kg of Synergen? and Natugrain^®. Digestive enzyme activities were not affected by dietary treatments. Nevertheless, chyme pH along the intestine of fish fed the Natugrain^®‐supplemented diets was reduced. The ADC of nutrients increased with exogenous digestive enzyme supplementation, with the highest ADC values being observed for the 0.4 g/kg Natugrain^® diet. The ADC of dry matter, protein, lipids, energy and phosphorus in this diet were 26%, 6%, 4%, 16% and 63% higher, respectively, than in the control diet. Overall, diet supplementation with exogenous enzyme complexes seems to have high potential for improving the utilization of plant feedstuff‐rich diets for seabass juveniles. This study revealed that Natugrain^® was more effective than Synergen? in improving the ADC of nutrients and energy in European seabass juveniles.     

Exposure to different glyphosate formulations on the oxidative and histological status of <Emphasis Type="Italic">Rhamdia quelen</Emphasis>

Due to the wide use of glyphosate (GLY) in soybean cultivation, their residues in the environment may affect non-target organisms such as fish, developing toxic effects. Despite GLY being widely used in Brazil, there are few studies comparing the effects of commercial formulations in native freshwater fish species. Silver catfish (Rhamdia quelen) were exposed to three different commercial formulations of GLY 48 % (Orium^®, Original^® and Biocarb^®) at 0.0, 2.5 and 5.0 mg/L for 96 h. The effects in thiobarbituric acid-reactive substances (TBARS), catalase (CAT), superoxide dismutase (SOD), glutathione-S-transferase (GST) and histological alterations were analysed in the liver, whereas alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were studied in the plasma. In the liver, TBARS levels increased and CAT decreased in all treatments and herbicides tested in comparison with the control group. The SOD increased at 2.5 mg/L of Orium^®, Original^® and 5.0 mg/L Orium^® and Biocarb^®, whereas GST increased at 2.5 mg/L Orium^® and decreased at 2.5 mg/L Biocarb^® when compared to the control group. The main histopathological alterations in hepatic tissue were vacuolisation, leucocyte infiltration, degeneration of cytoplasm and melanomacrophage in all GLY treatments. The ALT decreased after exposure to 2.5 mg/L of Biocarb^® and AST increased at 2.5 mg/L of Orium^®, Original^® and 5.0 mg/L of Biocarb^® in comparison with the control group. In summary, the oxidative damage generated by GLY may have caused the increased formation of free radicals that led to the histological alterations observed in hepatocytes.     

Induction of meiotic gynogenesis in the stinging catfish Heteropneustes fossilis (Bloch) and evidence for female homogamety

This study reports the results on induced meiotic diploid gynogenesis and female homogametic nature in the Indian catfish, Heteropneustes fossilis. The eggs of H. fossilis were inseminated with conspecific sperm. The sperm suspension was diluted to 1 × 10⁷ sperm mL⁻¹ in Hanks balanced salt solution. Sperm were irradiated under UV light, with the exposure time ranging from 15 to 360 s (7500 ergs mm⁻² for 60 s). The genetic inactivation of paternal chromosomes was confirmed by chromosome counting from the larval cells and the larvae also had a characteristic haploid syndrome. A typical ‘Hertwig effect’ in the yield of hatched larvae was observed with doses of UV exposure >75 s (9375 ergs mm²). Larvae resulting from sperm UV irradiated above 120 s (15 000 ergs mm²) were 100% haploids. Application of heat shock to the activated eggs was effective in suppressing the release of the second polar body (meiotic gynogenesis) and resulted in diploid gynogenetic larvae morphologically identical to those of the control. The best yield of diploid gynogens (49.3% with respect to the control) was found to be at 6 min after egg activation and the heat shock at 41 °C for a 1-min duration, at an ambient water temperature of 27 °C. A total of 113 diploid gynogenetic fry from seven different female fish were reared and subjected to sexing. All gynogenetic fish were female in contrast to the control, which had a mean sex ratio of 56.7% females (which was not significantly different from 50% female). From these results, the sex determination mechanism in H. fossilis was presumed to be female homogamety.     

Effect of diethylstilbestrol (DES) and 17 β-estradiol (E2) on growth, survival and histological structure of the internal organs in juvenile European catfish Silurus glanis (L.)

The effect of supplemented commercial diets with diethylstilbestrol (DES—15, 30 and 60 mg kg^?1) and 17 β-estradiol (E2—30 and 60 mg kg^?1), two chemicals commonly used in sex reversal procedure in fish, on survival and growth parameters of juvenile European catfish (Silurus glanis) was evaluated. During the two experiments, lasting 28 days each, fish were kept at temperature 25.2–26.5 °C, pH 7.4–9.3 and oxygen concentration 5.0–7.3 mg O₂ dm^?3. DES supplementation resulted in depressed growth rate of catfish. In experimental groups fed with E2, no negative effect on growth parameters was found. Both chemicals did not result in observed mortality. In all of the experimental DES groups, hepatosomatic index increased significantly, which suggests negative influence on physiological condition of catfish. DES supplementation significantly changed cytological factors of liver cells and caused hepatic alterations in parenchyma, such as vacuolization and blood congestion. Similarly, supplementation of E2 in food resulted in changes in cytological parameters of hepatocytes. However, E2 did not cause pathological changes within the liver tissue. Histological examination of the catfish gonads showed 19 and 38 % of sterile fish after treatment with 30 and 60 mg kg^?1 of DES, respectively. The results suggest that DES served in food could be ineffective in hormonal feminization process of European catfish. No disturbances of sex differentiation process after E2 treatment were observed. However, slight feminization effect in the highest level of E2 treatment group was recorded.     

Comparative growth and yield of channel catfish and channel × blue hybrid catfish fed a full or restricted ration

Growth and yield (kg ha^?1) of the channel catfish (Ictalurus punctatus, Rafinesque, 1818) and the channel × blue hybrid catfish [I. punctatus female ×I. furcatus (Lesueur, 1840) male], which shared the Jubilee strain of channel catfish as the maternal parent, were compared in sixteen 0.1 ha earthen ponds (14 852 fish ha^?1) during the April to November growing season. Each fish genetic group was fed a commercially formulated 32% protein feed daily to apparent satiation or at 80% of the mean daily satiation ration. Net yield and individual weight were higher for channel × blue hybrid catfish compared with channel catfish and for fish fed a full ration compared with a restricted ration. When fed a full ration, the channel × blue hybrid catfish grew faster from May to September than did the purebred channel catfish because the hybrid catfish consumed a greater percentage of its body weight at each feeding. Net yield within each fish genetic group was lower when feed ration was restricted. The per cent reduction in net yield in response to feed restriction was similar for each fish genetic group.     

Pharmacokinetics and tissue residues of marbofloxacin in crucian carp (Carassius auratus) after oral administration

Pharmacokinetics and residue elimination of marbofloxacin (MBF) were studied in crucian carp (Carassius auratus, 250±30 g) kept at two water temperatures of 15 and 25 °C. Marbofloxacin concentrations in plasma and tissues were analysed by means of high‐performance liquid chromatography using an ultraviolet detector. The limits of detection were 0.02 μg mL^?1, 0.02 μg g^?1, 0.025 μg g^?1, 0.02 μg g^?1 and 0.025 μg g^?1 in plasma and muscle, skin, liver and kidney respectively. Fish were administered orally at a single dosage of 10 mg kg^?1 body weight in the PK group. The data were fitted to two‐compartment open models at both temperatures. At 15 °C, the absorption half‐life () and distribution half‐life (t_1/2α) of the drug were 0.36 and 4.48 h respectively. The corresponding values at 25 °C were 0.23 and 0.87 h respectively. The elimination half‐life (t_1/2β) was 50.75 h at 15 °C and 25.05 h at 25 °C. The maximum MBF concentration (C_max) differed little between 15 (6.43 μg mL^?1) and 25 °C (8.36 μg mL^?1). The time to peak concentration was 1.74 h at 15 °C and 0.78 h at 25 °C. The apparent volume of distribution (V_d/F) of MBF was estimated to be 1.36 and 0.87 L kg^?1 at 15 and 25 °C respectively. The area under the concentration–time curve (AUC) was 301.80 μg mL^?1 h at 15 °C and 182.80 μg mL^?1 h at 25 °C. The total clearance of MBF was computed as 0.03 and 0.05 L h^?1 kg^?1 at 15 and 25 °C respectively. After repeated oral administration at a dosage of 10 mg kg^?1 body weight per day for 3 days, the results showed that the elimination half‐lives () of MBF from all tissues at 15 °C were longer than that at 25 °C. Therefore, water temperature is an important factor to be considered when deciding a reasonable withdrawal time.