Influence of food type,amount, and frequencies on the larviculture of pacamã catfish Lophiosilurus alexandri

This study assessed the performance of L. alexandri postlarvae (2 days after hatching) with different diets (Artemia and Panagrellus redivivus), food amounts (C₃₀₀-C₅₀₀-C₇₀₀), and feeding frequencies (F₁-F₃-F₆) in two experiments lasting 10 days. The best performing food type, Artemia and Artemia with P. redivivus, presented the highest survival rates as well as fish with the greatest weight, length, and specific growth rate (SGR). In the second experiment with Artemia, the weight, length, and SGR presented significant differences, increasing with higher amounts of prey. The best performance was obtained from a daily diet (F₁) with the greatest amount of prey (C₇₀₀).     

Aquaculture of the sand star,Astropecten indicus Döderlein, 1888, as a step toward the sustainable aquaculture of harlequin shrimp,Hymenocera picta Dana, 1852

Ornamental harlequin shrimp, Hymenocera picta, are commonly maintained on live comet sea stars, Linckia multifora. In Thailand, both species are commonly collected from the wild, raising concerns regarding the sustainability of such practices. As a step toward the sustainable aquaculture of both, methods of their culture and nutrition were investigated. Under captive conditions, harlequin shrimp readily predate, and can be maintained upon the astropectinid sand star Astropecten indicus as an alternative live feed during periods when comet sea stars are unavailable. Wild A. indicus subsequently spawned multiple times shortly after their collection; the eggs (300 μm diameter) were transferred to static aquaria. Following the appearance of planktonic bipinnaria, larval sea stars were fed a 50:50 Chaetoceros calcitrans and Isochrysis galbana diet. Eleven days post-transfer, brachiolaria stages began to settle; stages were then fed concentrated I. galbana. When specimens measured 1–2 mm in diameter, they were transferred onto an in-house formulated Amphiprion diet (>50% protein, >16% lipid). Sea stars were graded regularly; they matured and spawned after 6 months. Populations were maintained for more than three successive generations, demonstrating their ready culture under captive conditions, representing the first harvestable aquaculture of a sea star as a step toward supporting the sustainable culture of a primary, marine species.     

Hypothermal effects on expression of regucalcin,a calcium-binding protein,in the livers of seawater- and fresh water–acclimated milkfish,Chanos chanos

Fish Physiology and Biochemistry - Regucalcin (RGN) is a calcium-binding protein mainly expressed in the liver. It functions in regulating activities of several calcium-dependent enzymes related to...     

The presence of 17α,20β-dihydroxy-4-pregnen-3-one receptor activity in the ovary of the brook trout,Salvelinus fontinalis,during terminal stages of oocyte maturation

The presence of 17,20-dihydroxy-4-pregnen-3-one (17,20-DHP) oocyte receptor activity has been demonstrated in brook troutSalvelinus fontinalis. Scatchard analyses of the cytosol fraction during various terminal stages of oocyte maturation gave a high equilibrium association constant (K_a) value of 1.394±0.669 10⁸M^–1 (n=7) and low maximum binding capacities (N_max). The association kinetics of the receptor was second order k₊₁=2.292×10⁶M^–1 sec^–1. The dissociation rate constant k_a was 1.502×10^–2 sec^–1 for the first order dissociation reaction. The K_a=1.526×10⁸M^–1, when it was determined from k₊₁/k_–1 a value close to that found from the Scatchard analysis. Competition studies showed the following binding affinities testosterone > 17-HP > 17,20-DHP > Promegestone > progesterone > estradiol > pregnenolone; cortisol showed no competitive inhibition. Cytosolic extracts when pre-equilibrated with various labelled steroids and eluted from a Sephacryl S-300 column gave multiple specific binding peaks. On sucrose density gradient centrifugation specific binding was observed at 3.05 S in cytosol containing 0.15M sodium chloride buffer. The receptor lost binding activity when incubated with various proteases, but DNase and RNase had no effect. Blood plasma without heparin at (110) dilution also bound [³H]17,20-DHP, Ka was 8.04×10⁷ M^–1.The nuclear pellet extract (750×g) gave very little specific binding activity even at high radiolabelled steroid concentrations and a linear Scatchard plot was not obtained. Nevertheless the nuclear extract, after dextran-charcoal treatment, pre-equilibrated with [³H]17,20-DHP, bound specifically to DNA cellulose, and cytosol from the same oocytes also bound to DNA cellulose under similar conditions. Although specific binding to DNA cellulose was obtained the salt concentrations at which the steroid-receptor complex elution took place was not reproducible in both nuclear extracts and cytosol samples. Also binding activity was extremely small compared to the total cytosolic binding. The nuclear extract when pre-equilibrated with high concentrations (20 nM) of the labelled steroid and then chromatographed on Sephacryl S-300 column gave a specific binding peak which was similar to that of the cytosolic preparation.The receptor levels in cytosol decreased progressively during final maturation (Stages 1–7). There is preliminary evidence for the presence of 17,20-DHP receptor activity in cytosol of landlocked Atlantic salmonSalmo salar ouananiche, and rainbow troutSalmo gairdneri. The zona radiata fraction from late stages oocyes 5, 6, and 7 in brook and rainbow trout oocytes were isolated by ultracentrifugation; from this fraction a protein was characterized which covalently bound [³H]R5020 after photoaffinity labelling. The same protein also bound [³H]17,20-DHP after solubilization in Brig 35 buffer. The SDS gel electrophoresis subunit composition of the above protein was similar to the cytosol counterpart binding [³H]17,20-DHP, although the molecular weights were different. The blood sample [³H]R5020 binding component subunit composition was different from that of the membrane extracted protein. These results demonstrate the presence of 17,20-DHP receptor activity in the cytosol and zona radiata membranes of the oocytes during final maturation.A. Maneckjee is presently NSERC postgraduate scholar at MSRL and Ph.D. candidate at Department of Biochemistry, Memorial University of Newfoundland.     

Effect of long-term administration of dietary β-1,3-glucan on growth, physiological, and immune responses in Litopenaeus vannamei (Boone, 1931)

β-1,3-Glucan at different dietary doses was administered to enhance the growth, immunity, and survival against nitrite stress in Pacific white shrimp, Litopenaeus vannamei. Four different diets supplemented with 0, 250, 500, or 1,000 mg of β-1,3-glucan kg⁻¹ diets were fed to L. vannamei. Growth performance (weight gain and survival rate), physiological conditions (blood total protein, glucose, lactate, triacylglycerols, cholesterol levels) and immunological responses (superoxide dismutase, catalase, lysozyme, acid phosphatase, and alkaline phosphatase activities) of shrimp were recorded after 84-day feeding and 120 h after exposed to nitrite-N. After 84-day feeding, 250 mg kg⁻¹ β-1,3-glucan diet resulted in better weight gain (P < 0.05). Before the nitrite stress, blood lactate, triacylglycerols, and cholesterol level in shrimp fed with 250 mg kg⁻¹ β-1,3-glucan diet were significantly higher than those observed in shrimp fed with other diets (P < 0.05). Higher activities of catalase, lysozyme, and alkaline phosphatase were observed in shrimp fed with 500 or 1,000 mg kg⁻¹ β-1,3-glucan diet as compared to those obtained in shrimp fed with other diets (P < 0.05). After 120-h nitrite stress, blood protein, lactate, superoxide dismutase, catalase, and alkaline phosphatase activities in shrimp fed with 500 or 1,000 mg kg⁻¹ β-1,3-glucan were significantly higher than those observed in shrimp fed with other diets (P < 0.05). Glucose and triacylglycerol levels of shrimp fed with 500 or 1,000 mg kg⁻¹ β-1,3-glucan were significantly lower than those observed in other diets (P < 0.05). In shrimp fed with 500 and 1,000 mg kg⁻¹ β-1,3-glucan and 120-h after nitrite stress, the mortality was significantly lower than that observed in shrimp of control. Together, in this 84-day feeding trial, 250 mg kg⁻¹ β-1,3-glucan improved growth, whereas 500 mg kg⁻¹ β-1,3-glucan preferentially improved nitrite resistance, probably through accelerating energy metabolism and activating immune system.     

Factors affecting the catch and harvest rates of paddlefish downstream of Gavins Point Dam,South Dakota, 2000–2020

Paddlefish, Polyodon spathula (Walbaum), provide an important snagging and bowfishing fishery below Gavins Point Dam in South Dakota. During 2009–2020, snagging catch rates of paddlefish decreased below Gavins Point Dam to presumed “normal” lower pre-2004 levels, while bowfishing catch (harvest) rates significantly increased during 2000–2020. Because Paddlefish are highly migratory, both local (i.e., monthly gauge height, precipitation, and air temperature near Gavins Point Dam) and remote (difference in Mississippi and Missouri River discharge near their confluence) environmental conditions were used to explain variation in snagging catch rates and bowfishing harvest rates. Snagging catch rates were related to October gauge height, whereby deeper water in October led to decreased catch rates below Gavins Point Dam. Bowfishing harvest rates increased significantly after a 2016 regulation change moved the season from July 1 to July 31, and from June 1 to June 30, likely because water clarity was greater in June than in July. Mean annual air temperature and precipitation explained variation in bowfishing harvest rates prior to the 2016 regulation change. Our findings, the first to examine both snagging and bowfishing fisheries below Gavins Point Dam, suggest that local abiotic factors are likely more important than remote discharge for explaining variation in snagging catch rates and bowfishing harvest rates in the channelised Missouri River.     

Molecular and phenotypic characterization of Vibrio aestuarianus, a pathogen of the cultured tongue sole, Cynoglossus semilaevis Günther

Studies were conducted to determine the cause of high mortalities of cultured half-smooth tongue sole Cynoglossus semilaevis. Gross signs of disease included loss of appetite, erratic swimming, and haemorrhages on the head, opercula and base of fins, dorsal fin rot, swollen abdomen filled with ascitic fluid and herniation of the intestine. Histological examination of the liver showed focal areas of necrosis and extensive haemorrhages. Virtually pure, dense bacterial cultures were obtained from liver, kidney and spleen tissues, and high pathogenicity of the isolates to tongue sole was confirmed. The phenotypic characteristics of the isolates including morphological, physiological and biochemical characteristics were determined. The 16S rRNA and gyrB genes of the isolates were sequenced, and the phylogenetic trees representing genetic relatedness between the isolate and publicly available 16S rRNA and gyrB gene sequences from GenBank were constructed. The results confirmed that the diseased tongue soles were infected with Vibrio aestuarianus. The sequenced 16S rRNA gene of strain TS1 (GenBank Accession No. GQ372983) was 1446bp, the gyrB gene of strain TS1 (GenBank Accession No. GQ372984) was 1200bp and the two genes exhibited high similarity (98~99%) to those of V. aestuarianus from GenBank. In addition, the activities of extracellular enzymes and haemolysin were also studied; the results showed that the isolates produced beta haemolysis on rabbit blood agar, lecithinase, proteinase, DNase and lipase, but gelatinase was not produced.     

Presence of maturation-promoting factor in 17α,20β-dihydroxy-4-pregnen-3-one-induced oocytes of catfish,Clarias batrachus

Full-grown immature Clarias batrachus oocytes respond in vitro to exogenous 17,20-dihydroxy-4-preg-nen-3-one ( 17,20-DP) by undergoing germinal vesicle breakdown (GVBD). Cytosolic extract (CE) prepared from 17,20-DP-induced oocytes has been shown to produce similar effect when microinjected into unstimulated immature oocytes of the same fish. A dose of 50 nl is enough to cause 100% GVBD after 4 h. Maturation-promoting factor was investigated from 17,20-DP-induced, immature and cycloheximide treated oocytes incubated in presence of [³⁵S] methionine. When the proteins were extracted and analyzed on SDS-PAGE, two prominent bands corresponding to molecular weight 34- and 46-kDa were detected in the CE of mature oocytes. However, labelling of [³⁵S] methionine was observed mainly in the region of 46 kDa protein band indicating de novo synthesis of this particular protein during l7,20-DP-induction. Further, immunoblotting study by using rabbit anti-cyclin B₁ antibody has clearly demonstrated that the protein which is newly synthesized is highly homologous to Xenopus cyclin B₁ and goldfish cyclin B.     

Effects of 17β-estradiol injection on the reproductive efficiency of freshwater crayfish,Astacus leptodactylus (Eschscholtz, 1823)

The effects of 17β-estradiol injection (10^?7mol/crayfish) in adult female Astacus leptodactylus on the reproductive efficiency (i.e., pleopodal egg and stage 1 juvenile numbers) were investigated. In addition, hepatosomatic index, gonodosomatic index, and 17β-estradiol (E2) levels of crayfish ovary, hepatopancreas, and heamolymph before and after injections were also determined. Results showed that E2 injection to females enhances the reproductive efficiency of A.leptodctylus. E2 injection significantly increased pleopodal egg and stage 1 juvenile numbers, GSI, HSI, and concentrations of E2 in heamolymph, ovary, and hepatopancreas. However, E2 injection did not accelerate time of mating and proportion of pleopodal egg-berried females at the first week of reproduction season in this species. This study highlights that to improve the reproductive efficiency of A.leptodctylus by using hormones to regulate the ovarian cycle, E2 should be used at least 1.5 months before the commencement of the breeding season.     

Studies on activity, distribution, and zymogram of protease, α-amylase, and lipase in the paddlefish Polyodon spathula

A series of biochemical determination and electrophoretic observations have been conducted to analyze the activities and characteristics of protease, α-amylase, and lipase of paddlefish Polyodon spathula. The results obtained have been compared with those of bighead carp (Aristichthys nobilis) and hybrid sturgeon (Huso dauricus ♀?×?Acipenser schrenki Brandt ♂), in order to increase available knowledge of the physiological characteristics of this sturgeon species and to gain information with regard to its nutrition. Further, a comparative study of enzymatic activity, distribution, and characterization between commercial feed-reared paddlefish (CG) and natural live food-reared (NG) paddlefish was conducted. Results showed that higher proteolytic activity was observed in the pH range 2.5-3.0 and at a pH of 7.0 for paddlefish. Levels of acid protease activity of paddlefish were similar to that of hybrid sturgeon, and significantly higher than that of bighead carp. The inhibition assay of paddlefish showed that the rate of inhibition of tosyl-phenylalanine chloromethyl ketone was approximately 2.6-fold that of tosyl-lysine chloromethyl ketone. There was no significant difference observed for acid protease activity between PG and CG groups, whereas the activity of alkaline protease, α-amylase, and lipase in the PG group were significantly lower than those in the CG group. The substrate sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis further showed that there were certain types of enzymes, especially α-amylase, with similar molecular mass in the paddlefish and hybrid sturgeon. It can be inferred that acid digestion was main mechanism for protein hydrolysis in paddlefish, as reported for other fishes with a stomach. This indicates that the paddlefish requires higher alkaline protease, α-amylase, and lipase activity to digest natural live food.     

Influence of 11-ketotestosterone, 17β-estradiol, and 3,5,3′-triiodo-L-thyronine on distribution and metabolism of carotenoids in Arctic charr, Salvelinus alpinus L.*

This investigation examines the influence of implants containing 11-ketotestosterone (11KT), 17-estradiol (E₂), and 3,5,3-triiodo-l-thyronine (T₃) on astaxanthin metabolism in sexually immature individually tagged Arctic charr. The fish (initial average weight 427 g) were maintained in freshwater for 40 days, and weekly implanted intraperitoneally with oil-based injections containing either 11 KT, E₂ or T₃ at levels of 0.1, 1.0 and 0.1 mg (100 g body weight (BW))^–1, respectively. The control fish were given the oil medium alone (0.2 ml 100 g BW^–1). The diet contained ca. 50 mg astaxanthin kg^–1. Carotenoid composition was monitored in plasma, fillet, liver and skin, and 11 KT, E₂ and testosterone (T) levels in plasma. All hormone treatments reduced plasma T compared to the control. E₂-treated fish had a higher (p<0.05) hepatosomatic index (HSI) than the other treatments. Hormone treatment did not influence gonadosomatic index (GSI). T₃ administration induced a silvery skin appearance. The fillet and plasma carotenoid content decreased during the experiment. 11 KT implantation reduced astaxanthin and idoxanthin concentrations of plasma and fillets, and increased the amount in liver and skin, compared to the other treatments. The relative proportion of astaxanthin to idoxanthin was higher in the control fish and T₃ implanted fish, than in fish implanted with 11 KT or E₂ (p<0.05). Fish treated with E₂ had the highest skin carotenoid concentration. Male fish had significantly higher carotenoid content in plasma, fillet and skin than female fish. This study reveals that sex hormones affect carotenoid metabolism and partitioning among body compartments of Arctic charr, effects differently displayed by the sexes.     

Relativein vitro effectiveness of estradiol-17β, androgens,corticosteroids, progesterone and other pregnene derivatives on germinal vesicle breakdown in oocytes of Indian major carps,Labeo rohita,Cirrhinus mrigala andCatla catla

The relative effectiveness of estradiol-17, androgens, corticosteroids, progesterone and other pregnene derivatives on germinal vesicle breakdown (GVBD) was investigatedin vitro using folliculated oocytes of three carps,Labeo rohita, Cirrhinus mrigala, andCatla catla. In all three species progesterone and 17-hydroxyprogesterone could induce GVBD but relatively 17,20-dihydroxyprogesterone was consistently found to be the most potent maturation-inducing steroid. Both estradiol-17 and testosterone were ineffective in inducing GVBD. Androsterone and dehydroepiandrosterone were found to be effective inC. catla at all the concentrations used. Deoxycorticosterone (DOC), hydrocortisone (HC) and cortisone were effective inducer of GVBD inC. catla whereas inL. rohita andC. mrigala only cortisone was found to be effective. All 5-reduced pregnenes were effective in inducing GVBD inL. rohita but inC. catla, only 5-pregnane-17-01-3,20-dione and 5-pregnane-3,17,20-triol and inC. mrigala, 5-pregnane-3-ol-20- one could induce oocyte maturation.     

Effects of Dietary β-Hydroxy-β-Methylbutyrate on Growth and Survival of Nile Tilapia,Oreochromis niloticus,Vaccinated Against Streptococcus iniae

Abstract

β-hydroxy-b-methylbutyrate (HMB), a leucine catabolite, has been shown to cause increased disease resistance and growth in animal production. A vaccine produced from formalin killed bacteria and concentrated extracellular products of the ARS-98-60 Streptococcus iniae isolate has been used for the prevention of streptococcal disease in Nile tilapia, Oreochromis niloticus. In the present study, the effects of feeding HMB were determined in tilapia vaccinated by intraperitoneal (IP) injection of the S. iniaevaccine or unvaccinated (controls). Nile tilapia were fed diets containing either 0, 12.5, 25, or 50 mg HMB/kg diet for 14 days. The mean daily growth rate and feed efficiency showed no significant (P> 0.05) differences between the treatment groups. Dietary HMB supplementation did not enhance antibody production in unvacci-nated Nile tilapia following challenge. Dietary HMB supplementation did not enhance the survival of vaccinated Nile tilapia following challenge injection with 1 X10⁸ CFU of S. iniae.     

Effects of Different Feeding Frequencies on Growth,Body Composition,and Fillet Composition of Juvenile Sunshine Bass,Morone chrysops × M. saxatilis Grown Indoors

Abstract

In an effort to feed sunshine bass (Morone chrysops X M. saxatilis) efficiently, promote optimal growth, and reduce labor costs associated with feeding, sunshine bass were fed one of four feeding schedules: once per day, twice per day, once every other day, and twice every other day for 10 weeks. Ten fish were stocked into each of sixteen 110-L aquaria with four replications per treatment. At the conclusion of the feeding trial, percentage weight gain of sunshine bass fed twice/day were significantly (P < 0.05) higher (342%) compared to fish fed all other feeding frequencies. Specific growth rate (SGR) of fish fed twice/day was significantly higher (1.85%/day) compared to fish fed once every other day (0.69%/day) and twice every other day (1.18%/day) but not different (P > 0.05) from fish fed once/day (1.51%/day). The amount of diet consumed by fish fed twice/day was significantly higher (119 g diet/fish) compared to fish fed all other feeding frequencies. Feed conversion ratio (FCR) of fish fed twice/day were significantly higher (1.50) compared to fish fed once/day (1.28) and once every other day (1.15) but not different (P > 0.05) from fish fed twice every other day (1.35). Percentage fillet weight of fish fed once/day and twice/day were significantly higher (20.3% and 21.2%, respectively) compared to fish fed once every other day (15.7%) but not different from fish fed twice every other day (18.8%). Percentage lipid in fillet was not significantly different among all other treatments and averaged 9.7%. Percentage protein in fillet of fish fed once every other day and twice every other day was significantly (P > 0.05) higher (90% and 82.1%, respectively) compared to fish fed once/day and twice/day (81.1% and 81.5%, respectively). Based upon data from the present study, it appears that producers growing small juvenile sunshine bass indoors should feed fish twice daily. This feeding regimen allows for higher growth rates, without adverse effects on body or fillet compositions.     

Toxicity of wild juvenile “komonfugu” Takifugu flavipterus in the Bay of Sanriku Coast,Tohoku Area,Northern Japan

To clarify the mechanism of tetrodotoxin (TTX) accumulation in pufferfish, we compared the toxicity of two sets of wild juvenile “komonfugu” Takifugu flavipterus. The first set was sampled from Onisawa Fishing Port (FP) located in Okirai Bay, the Pacific Coast of Sanriku, Tohoku Area, Northern Japan. The second set was collected from the Onisawa FP and reared in an outdoor laboratory tank supplied with different seawater (Yoshihama Bay). The fish were sampled regularly and on the same days. The amount of TTX (mouse unit (MU)/fish) in the fish at Onisawa FP increased until 20 days and thereafter it did not change, while the amount of TTX in the fish in the laboratory tank remained low, and the TTX concentration (MU/g fish) decreased. Next, we compared the toxicity of wild juvenile T. flavipterus collected from Okirai Bay (Onisawa FP and Okirai FP) and Yoshihama Bay (Yoshihama FP). Large differences in TTX levels were observed among the fish from the three FPs. The amounts and concentrations of TTX in the fish at Onisawa FP were higher than those in the fish from the other two FPs. These results indicate that a large variation in toxic activity exists in the juvenile T. flavipterus in the bay of the Sanriku Coast.

     

Oxygen consumption in trilobite larvae of the mangrove horseshoe crab (Carcinoscorpius rotundicauda; Latreille, 1802): effect of temperature,salinity, pH,and light–dark cycle

A set of feeding trials was carried out for different microalgal species and processed diets for the culture of the New Zealand pipi, Paphies australis. Five microalgal species (Isochrysis galbana clone T-ISO, Pavlova lutheri, Tetraselmis suecica, Chaetoceros muelleri, and Thalassiora pseudonana clone 3H) and three formulated diets (baker's yeast, wheat flour, and corn flour) were fed to spat, juvenile, and adult pipi for 21 days. Unfed pipi were used in the control group. The spat and juvenile pipi showed a major shell increase with I. galbana while the greatest wet weight increase was obtained with P. lutheri. The shells of adult pipi grew better with corn flour, and the P. lutheri-fed group obtained the greatest wet weight. Results of proximate analysis in adult pipi revealed that proteins and lipids were accumulated in the tissue for all fed groups, while carbohydrate levels were depleted in all treatments including the control group. It is suggested that the gonads have developed during the experiment.     

Influence of oral administration of estradiol-17β and testosterone on growth,digestion, food conversion and metabolism in the underyearling red sea bream,Chrysophrys major

Estradiol-17 (E2) administered in the diet to the red sea bream Chrysophrys major did not affect appetite, food conversion efficiency, protein efficiency ratio and specific growth rate. Serum concentrations of total protein, albumin, globulin, vitellogenin, -amino acids, total lipid, free fatty acids, cholesterol and calcium were elevated. The hepatosomatic index was also increased. Activities of hepatic enzymes including lactate dehydrogenase, isocitrate dehydrogenase and glutamate-pyruvate transaminase were higher than found in untreated control fish. Intestinal activity of leucine aminopeptidase was augmented. However, there were no changes in muscle water, protein, lipid and glycogen content. In contrast, testosterone (T) given by the same route increased appetite, food conversion efficiency, protein efficiency ratio and specific growth rate. There were no alterations in serum protein and calcium concentrations but serum glucose, ammonia and triglyceride levels were elevated. Hepatic glycogen content was increased. The activities of hepatic fructose- 1,6-diphosphatase, glucose-6-phosphatase and glycogen synthetase and intestinal activities of alkaline phosphatase and -glutamyltransferase were higher than noted on control fish. The results reveal that estradiol-17 and testosterone exerted different metabolic effects in the red sea bream and they suggest that testosterone exerts its anabolic actions by increasing appetite, food conversion efficiency and activities of digestive enzymes.     

Effect of Diets Supplemented with Soybean,Flaxseed, or Menhaden Fish Oil on the Growth,Feed Utilization,Immune Status,and Sensory Properties of Channel Catfish in a Recirculating System at 22°C

Channel catfish feed intake and growth decline with temperature, but different dietary lipids might sustain performance during cool weather. Catfish at a suboptimal temperature (22°C) were fed 32% protein commercial floating pellets supplemented with 2% soybean oil (SBO), menhaden oil (MFO), or flaxseed oil (FLX). After 12 weeks, fish were counted and weighed, then health assays and proximate and fatty acid analysis of fillets were conducted. Weight gain, feed conversion ratio, and survival were similar among treatments, indicating limited potential of different lipids to improve growth at low temperatures. However, the favorable feed conversion ratios (FCRs; ≤1.6) indicated that feeding at 22°C was worthwhile to maintain good condition of catfish. Across diets, the unsaturated fatty acids in muscle lipids increased. The FLX and MFO both increased the n-3 HUFA in the fillet, but FLX was less effective. Unfortunately, both FLX and MFO reduced sensory properties of the fillet relative to the SBO control.