Fat Snook Centropomus Parallelus Research Articles

GROWTH OF JUVENILES OF THE FAT SNOOK, Centropomus parallelus, IN RESPONSE TO DIETARY LIPID, ENERGY AND PROTEIN

This study evaluated the growth of fat snook Centropomus parallelus in response to the dietary total lipids, gross energy (GE) and crude protein (CP) content. In the 1st experiment, five isonitrogenous diets with 541.7 ± 2.4 g kg-1 CP varied their lipid content in 113, 151, 160, 189 and 200 g kg-1 and GE in 18.8, 19.4, 20.4, 21.2 and 22.2 MJ kg-1, respectively. A total of 300 fish with 6.5 ± 2.4 g were stocked in 30 tanks of 1 m3 under 10 fish m-³ and reared for 96 days. There were no differences in fish final body weight (38.2 ± 12.5 g), daily weight gain (DWG, 0.35 ± 0.04 g day-1) and specific growth rate (SGR, 1.92 ± 0.11 day-1) among dietary treatments. Feed conversion ratio (FCR) was 1.76 ± 0.17 with a protein efficiency ratio of 1.06 ± 0.10. The viscerosomatic (VSI) and visceral fat indices (VFI) raised significantly with an increase in the dietary lipid while the hepatosomatic index (HSI) was unaffected. There was a significant reduction in feed intake as the dietary lipid content reached 189 g kg-1. In a 2nd study, five isolipidic diets (114.4 ± 1.9 g kg-1 lipids) with decreasing levels of CP and GE of 578, 535, 505, 465, and 430 g kg-1 and 20.5, 19.9, 19.4, 18.9, and 18.1 MJ kg-1, respectively, were evaluated. A total of 1,450 fish of 5.8 ± 2.1 g were reared in 30 tanks of 5.8 m³ under 10 fish m-3 for 93 days. Final survival reached 93.5 ± 5.5%. Fish DWG (0.27 ± 0.05 g day-1) and SGR (1.78 ± 0.11 % day-1) did not vary in response to dietary CP. Final body weight significantly reduced while HSI increased in fish fed the 430 g kg-1CP diet compared with fish fed the 578 g kg-1 CP diet. Results of this work indicated that fish between 5.8 g and 40.8 g wet body weight can maximize growth when fed diets containing 113.2 g kg-1 lipids, 540.5 g kg-1 CP and a 34.7 MJ kg-1 energy to protein ratio.
 Keywords: Centropomus parallelus, fat snook, protein, lipid, energy.

Reproductive biology of the fat snook Centropomus parallelus Poey, 1860 (Teleostei, Centropomidae) and implications for its management in the southern Atlantic Ocean.

The reproductive biology of Centropomus parallelus was described from 589 individuals captured in estuarine and coastal waters in Southern Brazil. Length-frequency distribution showed the dominance of males in smaller length-classes (132-290 mm LT ), whereas females were dominant in larger length-classes (>290 mm LT ). Total length at maturity (L50 ) was 180 mm LT and corresponded to 29% of the maximum length recorded. Histological sections revealed one hermaphrodite (205 mm LT ) and few immature females. Life history traits provided herein can contribute to sustainable fisheries management practices.

Niche Partitioning Among Snook (Pisces: Centropomidae) in Rivers of Southeastern Florida and Implications for Species Range Limits

The presence of relatively rare species in estuarine fish communities can influence niche differentiation among species, functional redundancy, and ecosystem stability when faced with environmental disturbance. In southeastern Florida, at least four species of snook (Centropomidae) occur in coastal river systems, but only one species occurs elsewhere in the state. To better understand how these species can co-occur, we analyzed data from electrofishing and diet studies conducted during 2007–2010 to investigate niche partitioning between two species: Common Snook Centropomus undecimalis and Smallscale Fat Snook Centropomus parallelus (common and fat snook hereafter). Although the diets of the two species collected from coastal rivers were barely distinguishable, there was separation of habitat use. Adult fat snook had affinities for low salinity portions of rivers, while common snook were distributed more widely. Use of nursery habitat by fat snook occurred during early spring, confirming winter spawning, which contrasts with the protracted spawning of common snook that occurs spring through fall. While in riverine nurseries, juvenile fat snook occupied shallow to moderate depths with cover (e.g., woody debris, docks); common snook had greater affinity for shallow natural shorelines (e.g., mangroves, aquatic macrophytes). Overall, fat snook appeared to occupy niches left open by the generalist common snook. Considering that centropomids are likely to expand their range northward in Florida with climate change, understanding habitat use and niche partitioning among the species may help predict which species is likely to expand first and what habitat types will be occupied.

Reproductive biology of the protandric hermaphrodite fat snook Centropomus parallelus Poey 1860 in a tropical estuary, northeastern Brazil

ABSTRACTThe aim of the present study was to analyze the reproductive aspects of the fat snook, Centropomus parallelus, in a tropical estuary. During the study period, 187 specimens were collected, including 73 females and 114 males. The length at first sexual maturity was estimated to be 224 mm for the females and 141 mm for the males. An extensive reproductive period, January to August, was observed for the females based on the gonadosomatic index. For the males, the highest values were from July to October. Sexual segregation was observed in length classes, with predominance of males and females in the smaller and larger sizes, respectively. This pattern, observed in protandric hermaphrodites, has been confirmed with the identification of an individual in sexual transition. The average relative fecundity was 14,260 oocytes. The average absolute fecundity was 491,036 oocytes/female, and the average size of the vitellogenic oocytes was 435 µm. Management actions are suggested for better conservation of the species.

ESPACIALIZAÇÃO DAS CAPTURAS DE ROBALO (Centropomus spp) ( CENTROPOMIDAE - PERCIFORMES ) NO ESTUÁRIO DO RIO SERGIPE

Os robalos ocorrem no estuário do rio Sergipe e têm importância nas capturas da pesca artesanal, no porto do Bairro Industrial, em Aracaju, com total desembarcado de 1,62 t em 2014. O objetivo deste trabalho foi analisar as capturas de robalo, no estuário do Rio Sergipe. Os dados de produção foram obtidos através dos registros de desembarques, no Bairro Industrial, de Abril/2016 a Dezembro/2017. Um total de 562 indivíduos foi coletado para obtenção de dados biométricos (CT, PT) e identificados. Para as duas espécies mais representativas, nos desembarques, foram estabelecidas a distribuição de frequência, a relação peso-comprimento e a média mensal do fator de condição K. Os dados de captura por unidade de esforço (CPUE), calculados para cada desembarque, foram LOG transformados (LOGCPUE+1) e comparados com ANOVA. As espécies de robalos presentes nas capturas foram o robalo-corcunda Centropomus parallelus (62% dos indivíduos), robalo-furador C. undecimalis (35%) e robalo-alfaiate C. pectinatus (3%). C. parallelus apresentou amplitude de CT de 20,0 a 60,0 cm. A média do fator de condição K para os indivíduos com CT > 28,0 cm foi de 10,7±1,1. A amplitude de CT de C. undecimalis foi de 20,0 a 105,0 cm, com K médio de 3,25±0,28. Para ambas as espécies, houve uma contribuição significativa de indivíduos abaixo do tamanho de primeira maturação. O pequeno tamanho de malha do arrasto de praia (20 mm) pode estar contribuindo para presença significativa de indivíduos de pequeno porte nas capturas. As principais áreas de captura de robalo, no Rio Sergipe, estão situadas em locais com alta concentração de matéria orgânica e baixos teores de oxigênio. Para rede de arrasto de praia, o período pluviométrico influenciou na variação da CPUE. A maioria das capturas das redes de emalhe se concentrou no canal do rio Sergipe e foi menos influenciada pela redução do habitat, no período seco.

The effects of subchronic exposure to copper in fat snook (Centropomus parallelus)

Anthropogenic processes affect different communities through the release of contaminated effluents into water bodies. Copper can be found in the effluents of most industrial processes and in other effluent types. The fat snook Centropomus parallelus, found from Florida in the United States to southern Brazil, is of great economic importance and is used as a food resource near the coast. This study aimed to determine the effects of copper on C. parallelus. The fish were exposed for 30 or 60 days to treatments of 0, 13 and 26μgCuL−1. Genotoxic effects of copper were observed in the micronuclei, especially in individuals exposed to higher concentrations. Copper exposure also had a negative effect on the growth of fat snook individuals. Compared to the control group without the addition of metal, an accumulation of metal was observed in the gills of exposed fish, an effect that was not found in the muscle.

Salinity does not alter the effectiveness of menthol as an anesthetic and sedative during the handling and transport of juvenile fat snook (Centropomus parallelus).

The effectiveness of menthol as anesthetic and sedative for fat snook (Centropomus parallelus) was tested at different salinities. In the first experiment, the fish were exposed to different concentrations of menthol (25, 37 and 50 mg L-1) in water at different salinities (0, 17 and 36 ppt). In the second experiment, the fish were transported for 10 hours in water with menthol at concentrations of 0, 3.7 and 7.4 mg L-1 under different salinities. Na+ and K+ ions from fish body and water were analyzed after transport. The optimal concentrations of menthol for a short handling period and surgical induction was 37 and 50 mg L-1, respectively, and these values were independent of salinity. After transport, neither mortality nor significant changes in ammonia or dissolved oxygen were observed between treatments at the different salinities. The nitrite levels were lower in freshwater than in brackish and saltwater, but did not change with mentol. The total body levels of Na+ increased with the salinity increase. Menthol is an effective anesthetic for handling of juvenile fat snook at different salinities. Menthol did not influence the measured water parameters and body ions, and it is not necessary for the transport of fat snook.

Desempenho de alevinos de Centropomus parallelus alimentados com dietas suplementadas com citrato e acetato

This study aimed to evaluate the addition of sodium acetate and sodium citrate in the diets of fingerling fat snook (Centropomusparallelus), through growth performance and modification of the intestinal microbiota. In the experiment, 3,000 fat snook fingerlings were used, with an initial average weight of 0.57 ± 0.10 g. The fish were stocked into 12 tanks (50 L) at a density of 5 fingerlings L-1 per tank distributed in three treatments with four replicates. The treatments were as follows: control group (without supplementation), one group supplemented with sodium acetate, and another group supplemented with sodium citrate. The diets supplemented with organic salts were sprayed with cod liver oil previously homogenized with 3% sodium acetate or sodium citrate. The fish supplemented with sodium acetate showed higher final weight, length, and yield, compared with the control group fish. The intestine of fingerling fat snook showed lower counts of total heterotrophic marine bacteria in the fish supplemented with acetate and citrate in relation to fish of the control group. Lower counts of sucrose non-fermenting vibrios were also observed in fish supplemented with acetate. Through this study, it was possible to evaluate for the first time the dietary inclusion of organic salts in the diets of marine fish in Brazil, with the dietary inclusion of 3% sodium acetate showing benefits for performance of fingerling fat snook.

Desempenho de juvenis de robalo-flecha e robalo-peva submetidos a diferentes densidades de estocagem em água doce

The objective of this experiment was to compare survival and growth of fat snook(Centropomusparallelus) and common snook (Centropomusundecimalis), reared in freshwater under different stocking densities. The experiment lasted 251 days. The fish were randomly distributed in cages (1 m x 1 m x 0.8 m), treatments in triplicate, placed inside an earthen pond located in Camboriu (SC). Water quality parameters were measured and were adequate for the species, except for the low temperatures (19.8 ± 3.3 °C). Zootechnical parameters were analyzed by a two-way ANOVA (species x density). Concerning growth, total length and condition factor were significantly different between species, and specific growth rate was not significantly different between treatments (0.23% day-1). Nevertheless, there was a significant interaction of species and stocking density in relation to final weight (fat snook 42.4 ± 16.8; 34.5 ± 15.3 e 39.1 ± 18.7 g; common snook 46.2 ± 18.3; 52.8 ± 22.6 e 46.4 ± 18.8 g; for 12.5; 25.0 and 37.5 fish m-³, respectively). Regarding survival, there was also a significantly difference between species (fat snook 90.0 ± 5.9% and common snook 66.3 ± 9.4%). Stocking density significantly affected biomass only (459 ± 74.5 g; 842 ± 100 g; 1,157 ± 293 g, in densities of 12.5; 25.0 e 37.5 fish m-³, respectively). Both species had a positive growth without a clear advantage for common snook, as expected.

Desempenho de juvenis de robalo-flecha e robalo-peva submetidos a diferentes densidades de estocagem em água doce

O objetivo deste trabalho foi comparar o desenvolvimento de peixes juvenis de robalo-peva (Centropomus parallelus) e robalo-flecha (Centropomus undecimalis) criados em água doce em diferentes densidades de estocagem, com três réplicas, durante 251 dias. Foram utilizados tanques-rede (1,0 x 1,0 x 0,8 m) no interior de um viveiro escavado no municí­­pio de Camboriú (SC). Os parí­¢metros de qualidade da água foram monitorados e permaneceram adequados para as espécies, com exceção da temperatura (19,8 ± 3,3 °C). Os parí­¢metros zootécnicos foram analisados por ANOVA bi-fatorial (espécie x densidade). A taxa de crescimento especí­­fico do peso não apresentou diferença significativa entre os tratamentos (0,23% dia-1) e o fator espécie teve efeito significativo apenas no comprimento e no fator de condição. Entretanto, houve interação significativa entre espécie e densidade para o peso (peva 42,4 ±16,8; 34,5 ± 15,3 e 39,1± 18,7 g; flecha 46,2 ± 18,3; 52,8 ± 22,6 e 46,4 ± 18,8 g; para 12,5; 25,0 e 37,5 peixes m-3, respectivamente). Com relação í­Â sobrevivência, a espécie também teve efeito significativo (peva 90,0 ± 5,9% e flecha 66,3 ± 9,4%). A densidade só teve efeito significativo na biomassa. O robalo-peva apresentou maior taxa de sobrevivência em água doce do que o robalo-flecha. O aumento da densidade somente resultou em incremento significativo na biomassa (459 ± 74,5 g; 842 ±100 g; 1.157 ± 293 g, para 12,5; 25,0 e 37,5 peixes m-3, respectivamente). Ambas as espécies apresentaram crescimento, mas sem vantagem ní­­tida do robalo-flecha, como seria esperado.

Effect of stocking density and vertical substrate addition on growth performance and health status of fat snook Centropomus parallelus

Fat snook Centropomus parallelus is one of marine finfish species with farm potential in Brazil, although some adjustments in farm practices are required to optimize its production. The aim of this study was to evaluate the effect of different stocking densities and vertical substrate addition on growth, survival and health status, such as hematological and parasitological aspects, in fat snook C. parallelus culture. The experiment was carried out evaluating 200, 350 and 500fishm−3 with (S) or without vertical substrate, totalizing 6 treatments as follows: 200-S, 200, 350-S, 350, 500-S and 500. Eighteen experimental units (20L plastic bins) were settled-up in a recirculation aquaculture system. After 51days, the results showed that the highest stocking densities (350 and 500) did not affect the final weight (~29g) and survival (100%). Moreover, zootechnical performance was not influenced by the vertical substrate addition. Fish presented 100% prevalence of monogenean in all treatments, with a significant increase (p<0.05) in the mean intensity in those kept at 500fish·m−3. The fish of this density had higher (p<0.05) RBC count and thrombocyte number when compared to other treatments. On the other hand, after hematological and parasitological analysis, the use of 350fish·m−3 with (S) substrate addition is recommended aiming a better health condition of C. parallelus in a recirculation aquaculture system. Statement of relevanceThis statement is mainly due to its application (vertical substrate) in commercial farms and its benefits observed in hematological and parasitological conditions of fish.

Evaluation of catch-and-release angling practices for the fat snook Centropomus parallelus in a Brazilian estuary

Recreational fisheries are developing for many iconic marine and estuarine fish species and are generating important social and economic returns in Brazil. Fat snook is the primary target species in southeastern Brazil and it supports a vibrant fisheries sector, including recreational fishing tournaments. To evaluate the impacts of recreational angling practices, we examined external hooking injuries, secondary physiological stress responses (i.e., blood glucose and lactate concentrations; N = 24), reflex impairment (N = 39), and overnight survival (N = 39) of fat snook angled with and without air exposure. We also examined physiological stress and reflex impairment of fat snook captured in a fishing tournament (N = 43) immediately post weigh-in and 1 h post weigh-in. Values were compared to baseline reflexes (N = 10) and physiology (N = 8) collected from minimally stressed fat snook. Fish captured by anglers infrequently had hooking injury but all angling and tournament treatments resulted in significantly elevated blood glucose and lactate, indicating a considerable physiological response to angling. Angling with air exposure and tournament weigh-in (in a dry container) resulted in the highest blood lactate values. The body flex reflex was occasionally impaired after angling or tournament practices, but this was consistent with baseline reflex actions, and the body flex reflex was therefore not a valuable indicator of fisheries stress or mortality in fat snook. Although angling and tournament practices caused a marked physiological stress response, low mortality of snook indicated that the species is resilient to brief bouts of angling at moderate water temperatures. However, high lactate values associated with air exposure suggest that handling practices be refined, particularly during tournament weigh-in. We recommend that anglers reduce air exposure intervals when handling snook prior to release and that recreational tournaments adopt wet weigh-in procedures to maximize the utility of catch-and-release in this fishery.

Ontogeny of the digestive tract of Centropomus parallelus larvae.

Development of the digestive tract and accessory glands of larvae of the fat snook Centropomus parallelus was examined under light microscopy, from hatching to 60 day post-hatching (dph). At hatching, the digestive tract is straight and composed by a cubic cell layer. The exogenous feeding starts at 3 dph, concomitantly with the mouth opening and subdivision of the rudimentary stomach and esophagus. At 4 dph, the intestine has three sectins, and vacuoles are observed in the posterior section, indicating the beginning of protein digestion and absorption. The pharyngeal teeth appear at 9 dph, and goblet cells appear at 13 dph in the esophagus. Gastric glands appear at 30 dph, marking the beginning of weaning. The disappearance of supranuclear vacuoles in the posterior intestine occurs at 35 dph, suggesting efficiency of extracellular digestion. This study shows that C. parallelus larvae is able to start weaning 15 days earlier than reported in earlier studies, increasing the success of larviculture.

Fish oil replacement by soybean oil in the diet of fat snook juveniles

The objective of this work was to evaluate fish oil replacement by soybean oil in diets, as for the effects on the performance and body composition of juveniles of fat snook (Centropomus parallelus). The experiment was carried out in a randomized block design, with three treatments (lipid sources) and six replicates, in a 60-day period. Fat snook juveniles (24.17±0.28g) were distributed in 18 experimental tanks of 200 L each, equipped with aeration and heating systems, under continuous water renovation (800% per day). Three isoproteic (44% CP) and isoenergetic (4,635 kcal CE kg-1) diets were formulated to comprise three replacement rates (0, 50, and 100%) of fish oil by soybean oil. Biometric analyses were done to evaluate fish performance, and two entire specimens from each replicate were used for body composition analyses. The zootechnical indices of weight gain (38.68±5.41 g), feed conversion (1.38±0.10), and specific growth at 1.70±0.18% weight gain per day were considered satisfactory. Lipid source substitution does not affect the performance and body composition of fat snook juveniles, which suggests that soybean oil can replace fish oil in diet formulation.

Acute copper toxicity in juvenile fat snook Centropomus parallelus (Teleostei: Centropomidae) in sea water

Three experiments were designed to assess the accumulation and acute toxicity of copper (Cu) in juvenile fat snook Centropomusparallelus. The first experiment was performed to determine the 96-h lethal concentration (LC50) of Cu. The second experiment was designed to assess the effects of sublethal concentrations of Cu (0.47 and 0.94 mg/L), while the third one allowed us to test the recovery capacity of fish exposed to the sublethal concentrations Cu and kept in sea water without Cu addition. The LC50value for Cu was found to be 1.88 mg/L Cu. Fish exposed to the sublethal concentrations of Cu showed a significant accumulation of Cu in gills at 96 h respect to the control ones (0.43 µg/g Cu). No significant difference was observed in the accumulation of Cu in gills between fish exposed to 0.47 mg/L (1.09 µg/g Cu) and 0.94 mg/L (1.26 µg/g Cu). Exposure (24 and 96 h) to the sublethal concentrations of Cu tested induced DNA damage in the erythrocytes. The results show that acute exposure to sublethal concentrations induces Cu accumulation and DNA damage in fish, these effects being recovered after 240 h in sea water without Cu addition.

Feminization and growth of juvenile fat snook Centropomus parallelus fed diets with different concentrations of estradiol-17β

In this study, we evaluated the effect of diets with various concentrations of estradiol-17β (E2) on the feminization, growth and survival of juvenile fat snook. Over a 45-day period, the juveniles were fed with five diets containing 0, 25, 50, 75 and 100 mg E2/kg feed. Three replicates were run for each diet. After this hormonal treatment, the fishes were transferred to 1-m3 net cages, where they remained for 12 months. During this period, they were fed a commercial diet without added hormones. During the feminization, the control fish grew more than those in the other treatments, and the survival rates did not differ significantly among the treatments. At the end of the experiment growth did not differ among the treatments. In the control treatment, 80.85 % of the fish were male, and the females were significantly larger than the males. All of the treatments with E2 produced 100 % females. No intersex fish were found in this study. This research showed that it is possible to obtain 100 % fat snook females using feeds with 25 mg E2/kg for 45 days without impairing the growth or survival of the fish.

Anesthesia and transport of fat snook Centropomus parallelus with the essential oil of Nectandra megapotamica(Spreng.) Mez

This study analyzed the chemical composition and anesthetic potential of essential oil (EO) of Nectandra megapotamica in fat snook (Centropomus parallelus). For the extraction of EO by hydrodistillation, leaves were separated in young (EO-Y) or old (EO-O), and the chemical composition of the EOs was determined by CG-MS. The anesthetic potential was assessed by the evaluation of induction and recovery time of anesthesia and stress response from anesthesia and transport. Three experiments were carried out: i) four different concentrations of each EO were tested to evaluate anesthesia induction and recovery time; ii) two concentrations of EO-O were tested for the evaluation of its effects on stress parameters (glucose, lactate, and Na+ and K+ plasma levels) caused by anesthesia; and iii) fish were transported in plastic bags, supplied with two concentrations of EO-O for the evaluation of water quality and mortality. All experiments were performed on fish acclimated to 0 and 33 ppt salinity. The main constituents of the Y and O-EOs were bicyclogermacrene (46.5/34.6%), α-pinene (26.8/26.2%), β-pinene (7.9/12.3%), and germacrene D (9.6/9.1%). Mild sedation was achieved at 30 °L L-1(1.3-3.2 min) and deep anesthesia at 150 °L L-1(5.6-8.0 min) with both EOs. The recovery time ranged from 1-10 min. The EO-O was not able to avoid the stress of anesthesia evidenced by elevated glucose and lactate plasma levels observed in all groups. Plasma levels of Na+ and K+ were not significantly affected by treatments. During transport, the use of EO-O did not prevent deterioration in water quality and the post-transport mortality. In conclusion, the EO of N. megapotamica has anesthetic activity in fat snook, but it was not able to prevent the stress of anesthesia and transport.

Use of the copepod Acartia tonsa as the first live food for larvae of the fat snook Centropomus parallelus

High-quality live food is essential for reducing the frequent high mortality of newly hatched fat snook (Centropomus parallelus) larvae in hatcheries. Copepods, a rich nutrition source, cultivated with the microalgae Chaetoceros muelleri and Isochrysis galbana, were evaluated as food for 0–14-day-old larvae. Two experiments were performed using nine 50-L tanks stocked with 2500 embryonated fat snook eggs. Three different dietary (treatments) were tested in triplicate: Experiment 1, Treatment 1 (Control), using rotifers Brachionus rotundiformis (20mL−1); Treatment 2 (Copepod), larvae were fed with Acartia tonsa (nauplii and copepodits, 0.1mL−1); and Treatment 3 (Mixed), larvae were fed with A. tonsa (0.05mL−1) and rotifers (10mL−1). In Experiment 2 to increase the density of live food, food organisms and the phytoplankton were introduced into the experimental tanks with the embryonated eggs and were stocked: Treatment 1, 20rotifersmL−1; Treatment 2, 0.5copepodsmL−1; and Treatment 3, 10rotifersmL−1 and 0.25copepodsmL−1. In Experiment 1, the Mixed Treatment increased significantly the survival rate (16.0%±7.5%) and mean larval weight (0.84±0.05mg) in relation to the other treatments. In Experiment 2, we observed significant improvements in larval notochord flexion in the Copepod and Mixed Treatment. The essential fatty acid profile of fat snook eggs had a DHA:EPA:ARA ratio of 11.4:2.4:1.0 while larvae in the Mixed and Copepods Treatments had ratios of 2.5:1.9:1.0 and 5.5:1.9:1.0, respectively. We conclude that the survival, development and the relationship between the major fatty acids were improved in treatments with copepods.

Morphocytochemical, immunohistochemical and ultrastructural characterization of the head kidney of fat snook Centropomus parallelus

This study characterized the structure and the morphocytochemical, immunohistochemical and ultrastructural aspects of the head kidney (HK) of the fat snook Centropomus parallelus. The HK is enclosed by a thin capsule of connective tissue, from which fine trabeculae originate and branch into the interior of organ. In the parenchyma, there are aggregates of lymphoid cells containing populations of lymphocytes T immunopositive for CDRO45, in a nodular arrangement, around blood vessels and melano-macrophage centres. Among the cells that constituted these aggregates and surrounded them, were macrophages and monocytes, and their precursors, with strong immunopositivity for CD68, along with cells of the granulocytic lineage in various phases of maturation positive for lysozyme and PAS. Macrophages and chromaffin and interrenal cells are also present. Ultrastructurally, the HK comprises a reticulum-endothelial stroma consisting of endothelial cells, reticulocytes of the fibroblast type and macrophage type and a parenchyma with increased cellularity, principally blood cells of the erythrocytic, granulocytic, lymphocytic, monocytic and thrombocytic series.

Taxa alimentar no desempenho de juvenis de robalo-peva em tanque-rede

Knowing the optimal feeding rate for a given species is important not only to promote higher growth and greater feeding efficiency, but also to prevent the deterioration of water quality resulting from excess food. This study aimed to evaluate the performance of the fat-snook Centropomus parallelus cultivated in net cages under the effect of different feeding rates (1, 1.5, 2 and 2.5% live biomass daily and control rate up to apparent satiation) in natural environment conditions. For 40 days, each treatment was evaluated in triplicate, in which the biological parameters (survival, specific growth rate, final average weight and length) and nutritional parameters (feed conversion ratio) were assessed. A polynomial regression analysis of specific growth rate suggests that in average temperatures of 25°C, the feeding rate which results in best growth for juvenile fat-snook is 1.7% of live biomass per day.