Haemorrhagic septicaemia in the hybrid surubim (Pseudoplatystoma corruscans×Pseudoplatystoma fasciatum) caused by Aeromonas hydrophila

Intensive culture of the hybrid surubim (Pseudoplatystoma corruscans × Pseudoplatystoma fasciatum) in Brazil is responsible for the occurrence of diseases and consequent economic losses. However, the causative agents are not well known. The objective of this study was to isolate and to characterize the pathogenic agent responsible for mortalities in cultured surubim and to demonstrate its virulence. Ten fish from a fish farm located in the Mato Grosso do Sul State (Brazil) were collected and 14 haemolytic bacteria characterized as Aeromonas hydrophila were isolated from the kidneys (eight) and brain (six). As an experimental challenge, fish weighing 98.1±23.6 g were injected with 1 mL of saline solution and 2 × 10², 2 × 10⁴, 2 × 10⁶ and 2 × 10⁸ CFU A. hydrophila mL^?1. Fish infected with 2 × 10⁸ CFU showed increased external and internal symptoms and mortality of 50±12.5% after 96 h. Increased A. hydrophila concentration was responsible for a decrease in haematocrit percentage and erythrocyte number, lymphocytes and eosinophils, as well as an increase in monocytes, neutrophils, serum agglutination titre and serum antimicrobial activity. It was concluded that A. hydrophila was responsible for characteristic symptoms of bacterial haemorrhagic septicaemia as well as important haematological and immunological alterations, which led to surubim mortality.     

Liver histology and histomorphometry in hybrid sorubim (Pseudoplatystoma reticulatum × Pseudoplatystoma corruscans) reared on intensive fish farming

This study aimed to characterize the liver histology and histomorphometry in sorubim hybrid of different categories (nursery, growth and grow‐out) reared on fish farming. The categories were defined considering body weight (BW): nursery category (n = 5): BW = 37.06 ± 6.00 g (31.6–45.3 g); growth category (n = 5): BW = 310.40 ± 53.80 g (242.1–376.4 g) and grow‐out category (n = 5): BW = 874.28 ± 27.59 g (846.2–913.1 g). Liver fragments were processed to paraffin inclusion, and sections were stained by haematoxylin and eosin (H&E), PAS (Periodic Acid Schiff) and Perl's staining to histology, histomorphometry and density volumetric of liver structures; glycogen analysis and to detect ferric irons (Fe³⁺) respectively. The hepatosomatic index decreased between the categories (P < 0.01). The percentage of PAS‐positive hepatocytes in the nursery category was higher (P < 0.05) in relation to the growth and grow‐out categories. The hepatocytes from all fish were positive to Perl's staining. The density volumetric of liver structures did not differ among categories except to blood vessels were higher (P < 0.01) in the nursery and growth. The area (μm²) and perimeter (μm) of hepatocytes, and the area (μm²), perimeter (μm) and volume (μm³) of the nuclei from grow‐out fish were lower (P < 0.01) than those from the nursery and growth categories. Changes in morphometric characteristics of hepatocytes may result from metabolic changes associated with body growth surubins; therefore, these morphometric characteristics of liver tissue can be used as functional biomarkers for the assessment of fish health and nutrition status.     

Digestibility of feed ingredients for the striped surubim Pseudoplatystoma reticulatum

Knowledge on apparent digestibility coefficients (ADC) is necessary to maximize the feed efficiency, thus lessening dietary nutrient and energy losses. This study tasks the determination of apparent digestibility of selected feedstuff to striped surubim Pseudoplatystoma reticulatum, a carnivorous, South American catfish of economic importance for fisheries and fish culture alike. Juvenile striped surubim (82.4 ± 17.7 g and 23.0 ± 1.6 cm) was distributed in 21 cylindrical, plastic cages (80 L), housed in seven 1000 L feeding tanks under constant water flow and aeration and conditioned to a two daily meals (20h00m and 22h00m) feeding regimen on a practical, reference diet (RD) (460.0 g kg^?1 crude protein (CP); 19.23 kJ g^?1 gross energy (GE)]. Test diets were obtained by adding of 1 g kg^?1 chromium III oxide and 300 g kg^?1 of one the following feedstuffs: fish meal (FM), meat and bone meal (MBM), poultry by‐product meal, feather meal, blood meal, soybean meal, wheat bran, corn and corn gluten meal to the RD. After the last daily meal, fish were transferred to cylindrical, conical‐bottomed aquaria (200 L) under aeration and continuous water exchange, coupled to refrigerated plastic bottles for faeces collection by sedimentation. Best ADC of protein (99.36%) and energy (86.25%) were recorded for poultry by‐product meal and MBM, respectively, which are thus deemed ideal surrogate feedstuffs to FM in the formulation and processing of diets for striped surubim.     

Dietary Levamisole as Immunostimulant for Striped Surubim,Pseudoplatystoma reticulatum

Immunostimulants are better suited for disease control than using drugs and chemicals as remedies in animal production. This study evaluates effects of dietary levamisole on growth and immunological parameters response of Pseudoplatystoma reticulatum. A trial was set up in a completely randomized design with six treatments – 0.0, 50, 100, 200, 300, and 500 mg levamisole per kg of feed (n = 3) – fed until apparent satiation, twice a day, for 60 d to striped surubim (77.68 ± 2.5 g) randomly stocked in 18 plastic tanks (300 L; 10 fish per tank). Dietary levamisole affected lysozyme activity and concentration, the best effects were recorded for fish fed 247 mg levamisole per kg of feed, that is, levamisole positively influenced innate immune system of striped surubim. However, dietary levamisole did not affect serum protein, albumin and globulins, as well as leukocyte respiratory burst activity and leukocyte proliferation. No differences in growth parameters were recorded. Dietary levamisole improved immunological responses of striped surubim.     

Dietary Protein Requirement of Juvenile Cachara Catfish,Pseudoplatystoma reticulatum

Cachara, Pseudoplatystoma reticulatum, is a high commercial value carnivorous catfish in Brazil, but whose dietary protein requirement is still unknown. Aiming to determine this requirement, groups of 15 juveniles (16.08 ± 1.13 g) were fed isoenergetic diets (4600 kcal/kg gross energy) with increasing levels of crude protein (30, 35, 40, 45, 50, and 55%). After 60 d, regression analysis revealed a quadratic effect (P < 0.05) of increasing dietary crude protein concentration on growth variables. The highest weight gain and specific growth rate as well as the best feed conversion were shown by fish fed the 50% crude‐protein diet. Similarly, protease activities were significantly higher (P < 0.05) in fish fed 50% crude protein. However, the highest protein retention was observed in fish fed the 45% crude‐protein diet. Protein and dry matter digestibilities did not differ (P > 0.05) for diets containing 40, 45, or 50% crude protein. Therefore, based on weight gain and at a dietary energy concentration of 4600 kcal/kg, the estimated protein requirement for juvenile cachara between 16 and 85 g is 49.25% crude protein. This is equivalent to 44.79% digestible protein and a gross energy to digestible protein ratio of 10.27 kcal/g.     

Effects of graded levels of dietary vitamin E on striped surubim Pseudoplatystoma reticulatum

Vitamin E is important to animal health, growth, productive performance, fillet quality and immune systems. This study evaluated the effects of dietary vitamin E on flesh composition, growth, biochemical and immunological parameters of striped surubim, Pseudoplatystoma reticulatum. Prior to beginning of the feeding trial, fish were fed a vitamin E‐free control diet for 45 days to reduce body deposits. The trial was set up in a completely randomized design; diets containing 3.4; 28.4; 53.4; 103.4; 153.4 and 303.4 mg DL‐α‐tocopherol acetate per kg of ration (n = 3) were fed twice a day to apparent satiation, for 90 days. Juvenile striped surubim (38.1 ± 4.9 g and 17.5 ± 1.5 cm) randomly stocked in 18 plastic tanks (300 L; 10 fish per tank). Based on serum globulin content and liver and fillet deposition of vitamin E, inclusion of 166.6 mg/kg of DL‐alpha tocopherol acetate in the diet is recommended to improve the immunological status and, probably, flesh quality of striped surubim.     

Genetic structure of the migratory catfish Pseudoplatystoma corruscans (Siluriformes: Pimelodidae) suggests homing behaviour

Abstract –  Pseudoplatystoma corruscans is distributed widely in the La Plata Basin in Brazil, where it is a very important species because of its high commercial value and ecological role as a voracious predator. This species undertakes long migrations during the dry and rainy seasons to feed and reproduce, respectively. In this study, we analysed seven microsatellite loci to test the hypotheses of the existence of a single panmictic population of P. corruscans in the La Plata Basin. All microsatellites analysed were highly polymorphic with the number of alleles per locus ranging from seven (Pcor28) to 30 (Pcor10). Across all samples, 107 alleles were detected. Thirty alleles were private, i.e., found in only one sample. Highly significant genetic differentiation was observed among samples in three of the four analyses performed: F _ST (from 0.03435 to 0.16349, P  < 0.05), Analysis of molecular variance (amova) F _ST = 8.25% ( P  < 0.0001) and amova R _ST = 9.72% ( P  < 0.0001). A microsatellite multilocus Bayesian assignment test with the programme structure confirmed the division of the fishes into six groups largely concurrent with main branches on a population neighbour-joining tree. The obtained results rejected the panmixia hypothesis. On the other hand, the documented long-distance movements of P. corruscans and the geographical scale of genetic differentiation found in this study indicate a strong tendency for fish of this species to utilise their natal nursery regions for reproduction, which represents the first demonstrated example of homing in a freshwater catfish in South America.     

Hatching rate and larval growth variations in Pseudoplatystoma punctifer : maternal and paternal effects

In Pseudoplatystoma punctifer (e.g. Pseudoplatystoma fasciatum) larvae, parental effects on hatching, growth of initial stages and dry feed adaptation were evaluated as they could influence fry heterogeneity, which is responsible for the enhancement of cannibalism, and which remains one of the main factors of mortality during larval stages. A full factorial experiment was carried out with 3 females × 3 males producing nine families of full siblings, raised separately in triplicates into 30 L tanks at 28±0.5 °C in a water recirculating system. Paternal and maternal effects were observed on hatching success, yolk utilization efficiency and growth until 26 days post fertilization. Hatching success was generally over 80% except for one male × female combination (25%). Total length (TL) at hatching and during the first 4 weeks of exogenous feeding on live Artemia nauplii and dry feeds was determined in each family using digital photographs of larvae and nih image j analysis freeware. Mean TL was calculated for each family at each sampling time and analysed using multifactorial analysis of variance tests. These results indicate not only dam but also sire effects at very early developmental stages as well as in subsequent stages of P. punctifer.     

Artemia sp. Proportions and Effects on Survival and Growth of Pintado,Pseudoplatystoma corruscans Larvae

ABSTRACT

The aim of the present study was to evaluate the survival and growth of larvae (L) of pintado, Pseudoplatystoma corruscans, fed different Artemia sp. proportions: 50, 200, 350, 500, 650, 800, and 950 Artemia nauplii per larva per day, in a complete randomized design. Water salinity was 1.7%, and larviculture lasted for a period of 15 days, which was divided into three individual 5-day trials. Larvae were stocked at a density of 15 per liter and kept in the dark. The concentrations of un-ionized ammonia-N and nitrite-N were directly proportional to the increase in prey density (P < 0.05). Regression analysis showed increased survival and growth rates up to 200, 350, and 500 nauplii/L/day, for the first, second, and third trials, respectively. These results indicate that larval food intake is related to ontogenetic development stage.     

Use of White Fat as a Replacement for Squid Liver Oil in Practical Diets for Surubim Pseudoplatystoma coruscans

The effect of dietary lipid on culture performance, fatty acid composition of carcass, and the liver polar lipid of surubim fingerlings Pseudoplatystoma coruscans was investigated. Five isonitrogenous (46.5% crude protein) and isolipidic (19% crude lipid) diets were formulated with squid liver oil (SLO) and white fat (pig lard-PL) as lipid sources. Diet 1 was supplemented with 12% SLO, diet 2 with 8% SLO and 4% PL, diet 3 with 6% SLO and 6% PL, diet 4 with 4% SLO and 8% PL, and diet 5 with 12% PL. Fish were fed to apparent satiation over a 64-d feeding trial. No statistically significant difference ( P >0.05) was observed in growth performance of fish. In contrast, fatty acid profile of fish carcass and liver polar lipid fraction was affected ( P 0.05) by dietary fatty acid composition. Palmitic (16:O) and the oleic (18:1n-9) acids were the major saturated and monoene fatty acids respectively found in fish carcass, independent of the lipid source in the diets. The total amount of saturated and monoene fatty acids was significantly higher ( P 0.05) in the carcass of the fish fed diets 4 and 5, than in the other fish. The concentration ( P 0.05) of eicosapentaenoic and docosahexaenoic acids and the n-3/n-6 ratio in fish carcass and in polar lipid fraction of liver increased in direct proportion to the level of squid liver oil in diet. Results of this experiment clearly demonstrated that both squid liver oil and pig lard have a positive nutritive value for surubim and that it is possible to increase the n-3 to n-6 ratio in favor of n-3, without loss in the growth performance, feeding fish with a diet containing a lipid source rich in this fatty acid.     

Effects of Temperature on Performance Characteristics and the Cortisol Stress Response of Surubim Pseudoplatystoma sp.

Three experiments were conducted in flow‐through tanks at 24, 27 and 30 C to evaluate growth, food conversion, morbidity, survival, and the cortisol stress response of surubim Pseudoplatystoma sp. at different temperatures. In Experiment 1, fish (mean initial weight, 33.3 ± 7.2 g) reared at 27 and 30 C for 60 d grew significantly faster than fish reared at 24 C (P < 0.05). Fish at the lowest temperature showed the poorest feed conversion ratio (FCR, 5:1), while fish at 27 and 30 C had FCRs of 2.5:1 and 3.5:1, respectively. Mortality and morbidity rates were inversely proportional to the temperatures tested. In Experiment 2, serum cortisol levels following an acute handling stressor peaked at 30 min after stress, returned to near‐resting levels at 1 h after stress, and completely returned to resting levels at 3 h after stress in fish at all temperatures tested. Peak serum cortisol levels were higher in fish at 30 C (321.1 ± 38.8 ng/mL) than those in fish at 27 and 24 C (143.3 ± 37.4 ng/mL and 104.2 ± 37.2 ng/mL, respectively). In Experiment 3, fish (mean initial weight, 67 ± 8.58 g) reared at 27 C for 137 d grew significantly faster than fish at 30 and 24 C. Virtually, all fish reared in 30 C had some sign of morbidity (skin lesions and fin abrasion) compared to only a small percentage of fish in the other two temperatures. Again, the highest cortisol peak level was measured in fish reared at 30 C (117.6 ± 16.7 ng/mL), as compared to fish at 24 and 27 C (99.2 ± 15.5 ng/mL and 80.2 ± 12.8 ng/mL, respectively). Our findings indicate that the optimum temperature for rearing surubim in tanks is 27 C. At 30 C, these fish may suffer from stress, as suggested by the elevated peak of cortisol and morbidity and mortality rates. The relatively rapid cortisol stress response of surubim suggests that they may be more tolerant to handling stressors than other fish species.     

Intestinal morphology and histology of the striped catfish Pseudoplatystoma fasciatum (Linnaeus, 1766) fed dry diets

This study unveils histological features of the intestinal tract of juvenile striped catfish Pseudoplatystoma fasciatum (Linnaeus, 1776) in three size classes (weight, standard length): I – 36.84 ± 10.19 g, 14.52 ± 1.54 cm; II – 59.03 ± 11.47 g, 17.17 ± 1.06 cm; III – 89.72 ± 18.70 g, 20.79 ± 1.55 cm, respectively. Histological organization of the juvenile speckled catfish intestine bears features common to the carnivorous fish, but the organ presents some convolutions that indicate a certain degree of dietary flexibility, a surprising trend, common only to omnivorous Siluriforms. The architecture of the mucosa of the speckled catfish intestine indicates that the species concentrates digestion and absorption of nutrients in the medium intestine, a common feature among carnivorous Teleosts.     

Induced breeding and larval rearing of Surubí, Pseudoplatystoma fasciatum (Linnaeus, 1766), from the Bolivian Amazon

Brooders of Surubí (Pseudoplatystoma fasciatum) were caught in the Ichillo River (Bolivian Amazon) and adapted to captivity conditions for 1 year in the facilities of the experimental aquaculture station of ‘El Prado’ (Santa Cruz de la Sierra) under natural temperature and photoperiod conditions. Induced reproduction was obtained by means of Ovaprim^® (Syndel, Canada) injections and artificial fertilization. Sperm and ova were obtained by gentle stripping of male and female brooders. Fertilized eggs were incubated in 60 L Zug jars. A mean hatching rate of 73.7±19.0% was obtained after 24 h at 26.5 °C. For larval rearing, several protocols were tested with different settings of photoperiod, light intensity, food type and period of distribution, and stocking density. The best survival rates were obtained with Artemia nauplii feeding in total darkness. A high level of aggressiveness between larvae and precocious appearance of jumpers was observed, but these can be controlled with appropriate rearing conditions.     

Dietary lipid level and source affect metabolic responses in hybrid catfish (Pseudoplatystoma reticulatum × Leiarius marmoratus)

This study was undertaken to evaluate the effect of dietary lipid source [linseed oil (LO, rich in 18:3 n?3); corn oil (CO, rich in 18:2 n?6); olive oil (OO, rich in 18:1n?9); and fish oil (FO, rich in LC‐PUFA)] and level (9% L and 18% L) on growth, body composition and selected plasma biochemistry parameters in hybrid catfish (Pseudoplatystoma reticulatum × Leiarius marmoratus) juveniles. Moreover, liver histology (lipids, glycogen, cell vacuolization) and key metabolic enzyme activities were also evaluated. After 8 weeks of feeding, there were no differences in growth performance and whole‐body composition between groups. Plasma lipoprotein, muscle and liver composition, and G6PD and ME activity were affected by lipid level and source. No differences were observed between groups in hepatic ALT activity; however, AST activity was lower in fish fed the 9% L diets. Overall, liver and muscle fatty acid composition reflected that of diet FA composition, with increased n3/n6 ratio, high HUFA and low MUFA in fish fed FO compared with the VO diets. Higher liver glycogen content was observed in fish fed the 18% L than the 9% L diets, except for fish fed FO diet. Considering the experimental diets used, these results indicate that hybrid catfish can efficiently utilize VO supplementation as an energy source, without affecting growth performance and fillet composition.     

Lactococcus garvieae outbreaks in Brazilian farms Lactococcosis in Pseudoplatystoma sp. – development of an autogenous vaccine as a control strategy

This study evaluated the control of streptococcosis outbreaks in Brazil, isolated from diseased sorubim and identified as Lactococcus garvieae by genetic sequencing. This report determined the potential for lactococcosis control in sorubim Pseudoplatystoma sp. with two vaccines: an aqueous‐based, whole‐cell inactivated vaccine (bacterin) and an oil‐adjuvanted bacterin. Their efficacy was evaluated at 30 days post‐vaccination (d.p.v.) by challenge with L. garvieae, and the antibody production response at 15, 30 and 60 d.p.v. and the non‐specific immune response were compared amongst treatments. High protection levels (P < 0.05) were achieved with the oil‐adjuvanted vaccine with a relative percentage survival value of 81.7% at 30 d.p.v. Additionally, the oil‐adjuvanted vaccine increased the immunogenicity of the bacterin as indicated by greater agglutination antibody titres from 15 until 60 d.p.v. This is the first report of a positive effect of vaccine administration on the specific immunity of sorubim, and the study showed that a specific antibody plays an important role in sorubim defence against lactococcosis because the innate immune responses were similar in all of the studied animals. These results demonstrated that oil‐adjuvanted vaccine can be an effective alternative for the protection of sorubim from L. garvieae disease.     

Growth, Maturation, Induced Spawning, and Production of the First Generation of South American Catfish, Pseudoplatystoma sp., in North America

Growth, plasma steroids, and the appearance of gonads (histology and gonadosomatic index) were followed in South American catfish (surubim, Pseudoplatystoma sp.) raised in captivity in the aquaculture facility at The Ohio State University, Columbus, Ohio, USA, from 2003 until 2006. Broodstock growth showed a great individual variation and it did not seem sex dependent. The levels of 11‐ketotestosterone were high in males during the reproductive season. Three out of six females spawned after receiving two doses of carp pituitary extract (0.5 and 5 mg/kg) at 11‐h intervals. Fertilization was performed in only one female in February 2006. Egg size was 0.73 ± 0.06 mm in diameter at stripping. Two males released sperm, and it was used for fertilization. Sperm concentrations were 24 × 10⁹ and 15.5 × 10⁹ spermatozoa/mL in Male 1 and Male 2, respectively, and viability was confirmed after activation in 0.3% NaCl. Embryo survival at 9 h after fertilization was 44 and 23% for Male 1 and Male 2, respectively. Embryos hatched 15 h after fertilization. Larvae were 3.53 ± 0.09 mm in length at hatching and were successfully raised (72% survival after 2 wks) using live brine shrimp nauplii.     

Performance, carcass composition and nutrient utilization of surubim Pseudoplatystoma coruscans (Agassiz) fed diets with varying carbohydrate and lipid levels

Five isonitrogenous diets formulated to contain 470 g kg^?1 of crude protein, five different levels of crude lipids (190, 210, 230, 250 and 270 g kg^?1), five different levels of carbohydrates (178, 155, 158, 125 and 110 g kg^?1) and gross energy (21.2, 21.6, 22.4, 22.8 and 23.2 MJ kg^?1) were used to investigate the effect of dietary lipid levels on performance and carcass composition of the surubim, Pseudoplatystoma coruscans (Agassiz). Triplicate groups of 11 fish with an average individual body weight of 5.1 ± 0.2 g were randomly assigned to 15 net cages and fed each test diet twice a day to apparent satiation for 64 days. At the end of the trial there were no significant differences in feed consumption or fish performance. No differences (P > 0.05) were observed in the lipid content of fish carcass and liver. On the contrary, visceral lipid increased (P < 0.05) with the increase in dietary lipid level. Protein and energy retention efficiencies were not significantly affected (P > 0.05) by the dietary lipid and carbohydrate levels. The results of this trial suggest that increasing dietary lipid levels from 190 to 270 g kg^?1 did not improve growth performance or protein sparing and caused an undesirable increase in the visceral lipid content of surubim fingerlings.     

Effect of dietary supplementation of inulin and W. cibaria on haemato‐immunological parameters of hybrid surubim (Pseudoplatystoma sp)

The dietary supplementation of prebiotics, probiotics and symbiotic in hybrid surubins (a Pseudoplatystoma corruscans and P. fasciatum cross) was evaluated for the effects on their autochthonous intestinal microbiota and on haematological and immunological parameters. A total of 160 fish were divided into four treatment groups with four replicates each. The treatment groups were fed with the following diets for 15 days: control diet without supplementation; 0.5% inulin (prebiotic) supplementation; Weissella cibaria (CPQBA 001‐10 DRM 02) (7.87 ± 0.2 log CFU g^?1) supplementation; or 0.5% inulin and W. cibaria supplementation (symbiotic group). The midgut intestines of the fish with the symbiotic diet supplementation had higher concentrations of lactic acid bacteria (7.07 ± 1.11 log CFU g^?1) and low levels of Vibrio spp (1.90 ± 0.60 log CFU g^?1) and Pseudomonas spp (2.23 ± 1.48 log CFU g^?1). In addition, increased erythrocytes and reduced circulating neutrophils were observed in this group. No differences in blood glucose, serum protein or lysozyme levels were detected between treatment groups. However, a higher concentration of total immunoglobulin was observed in fish fed with the probiotic and symbiotic diets. The addition of 0.5% inulin (prebiotic) thus W. cibaria (probiotic) to the diet of Pseudoplatystoma hybrid surubins reduce the number of pathogenic bacteria and stimulate the beneficial intestinal microbiota and may possibly alter their immune defence system.     

Growth,body chemical composition and trypsin activity of South American catfish,surubim (Pseudoplatystoma sp.) juveniles fed different dietary protein and lipid levels

To evaluate protein and lipid requirement of South American catfish surubim (Pseudoplatystoma sp.) juveniles, nine semi‐purified diets containing three levels of protein (40%, 45% and 50%) and three levels of lipid (12%, 16% and 20%) were tested. After 8‐week feeding trial, body weight increase averaged 2124.3 ± 295.7%. Growth performance was significantly affected by dietary level of protein (P < 0.05). At the 40% protein level, increasing level of dietary lipid had a positive effect on final individual mean weight (protein sparing effect). Whole body protein and moisture contents were affected by the dietary level of lipid (P < 0.05). Whole body lipid content positively correlated with the level of dietary lipid (P < 0.05). Cannibalism related mortality was observed despite rearing fish in 24 h dark. Fatty acid composition of fish was affected by the dietary lipid level (P < 0.05). Polyunsaturated fatty acids increased with the increasing level of dietary lipid while saturated fatty acids and monounsaturated fatty acids decreased. Trypsin activity in the digestive tract of surubim was influenced by dietary levels of protein and lipid (P < 0.05). Our preliminary results suggest that the optimum protein/lipid ratio might be close to 45/16% for surubim juveniles.