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The global production of aquatic organisms has grown steadily in recent decades. This increase in production results in high volumes of by-products and waste, generally considered to be of low commercial value and part of them are consequently discarded in landfills or in the sea, causing serious environmental problems when not used. Currently, a large part of the reused aquaculture waste is destined for the feed industry. This generally undervalued waste presents an important source of bioactive compounds in its composition, such as: amino acids, carotenoids, chitin and its derivatives, fatty acids and minerals. These compounds are capable of offering numerous benefits due to their bioactive properties. However, the applicability of these compounds may be opportune in several other sectors. This review describes studies that seek to obtain and apply bioactive compounds from different sources of aquaculture waste, thus adding commercial value to these underutilized biomasses.HIGHLIGHTSVolume of aquaculture industrial waste from crustaceans and mollusks.Quantity and quality of bioactive components in aquaculture waste.Applications of recovered proteins, lipids, chitin, carotenoids and minerals.Future prospects for the destination of aquaculture waste.

Phosphorus is an essential mineral present in the vegetable matter in the form of phytate, which is considered an antinutritional factor. Phytate can be degraded by phytases, which have been used in commercial feeds. However, these enzymes undergo costly isolation and purification processes. In the present study, a genetically modified (GM) Bacillus subtilis strain that expresses a fungal phytase was used as a feed additive. The GM probiotic was added to the commercial feed of shrimp Litopenaeus vannamei and its effects on zootechnical performance, proximate composition of muscle, lipid concentration in hepatopancreas and expression of genes related to digestion, amino acid metabolism and antioxidant defenses were analyzed. Although the genetically modified probiotic had no impact on growth parameters, there was a 39% increase in phosphorus content in muscle. In addition, genes related to digestion were downregulated in shrimp hepatopancreas, as well as an increase in lipids in this tissue. These results demonstrates that the GM probiotic increased the efficiency of the use of plant-derived phosphorus, which may imply a decrease in the addition of this element in the diets, as well as minimizing the impact of shrimp farms on the eutrophication of adjacent ecosystems.

The chemoprotection of "buriti” Mauritia flexuosa (inclusion in diet: 0-control group; 1.25; 2.50; 5.00; and 10.00% W/W) to Litopenaeus vannamei postlarvae (PL) exposed to ammonia or nitrite was investigated. Analyzed variables include antioxidant (ACAP) and oxidative damage (TBARS) responses and levels of total carotenoids. The results indicated that there was no significant difference (p >0.05) in zootechnical variables between diets. The PL carotenoid content (R2 = 0.86), ACAP (R2 = 0.78), and TBARS (R2 = 0.91) showed a dose-dependent relationship with the inclusion levels of "buriti” (p

The objective of the present study was to evaluate the use of fermented and non-fermented whole rice bran for rotifer feeding, based on the effects on growth parameters, antioxidant and oxidative damage responses, and water quality. The study was based on three experiments, which compared the effect of different concentrations of non-fermented whole rice bran, the effect of different concentrations of fermented whole rice bran and the effect of the best concentrations of fermented and non-fermented whole rice bran, as well as the replacement of part of the baking yeast by rice bran. The results showed the best growth performances in treatments with 0.7 g yeast with 1.5 g fermented rice bran, 0.35 g yeast with 0.75 g whole rice bran, and 0.35 g yeast with 0.75 g fermented rice bran. Fermentation of rice bran for 6 hours did not induce oxidative stress in rotifers. This work revealed that the use of 1.5 g of fermented bran and replacement of 50% of yeast with fermented or non-fermented rice bran may be used for rotifer feeding, with the additional benefit of improving the environmental quality due to the lower amount of ammonia released in the water.

In this study Aflatoxin B1 (AFB1), ochratoxin A (OTA) and zearalenone (ZEN) occurrence in fish feed, regarding its chemical composition, were investigated. Besides, AFB1 bioaccessibility to fish wa...

Functional foods have molecules that promote health benefits beyond their nutritional qualities. In this context, the zootechnical performance, color, and biochemical responses of Pacific white shrimp (Litopenaeus vannamei) fed with different levels of acai (Euterpe oleracea), a fruit with unique antioxidant characteristics, were observed. Four diets with different levels of inclusion of lyophilized acai (0.0%, 2.5%, 5.0%, and 10.0% W/W) were administered to shrimps reared in biofloc technology (BFT) systems. After 43 days, the zootechnical parameters (weight gain, feed conversion ratio, and specific growth rate) and coloration in fresh and cooked shrimps were measured, and the L*, a*, and b* parameters were estimated with a digital colorimeter. Survival and growth performances were not affected by acai inclusion in diets. Acai inclusion modulates the flavonoid content in the gills of L. vannamei and in the bioflocs of the rearing BFT system. As in the diet of 10.0% acai, performed with a total replacement of fish oil without affecting growth, we propose the use of acai as a vegetal oil source for shrimp feeding in BFT systems. Acai also induced the reddish color in fresh and cooked L. vannamei, an influential factor in their commercial value.

This study investigated the effects of the inclusion of Mauritia flexuosa fruit pulp in the diet on the growth performance, economic benefit, muscle composition, total contents of carotenoids and flavonoids, chromaticity parameters, total antioxidant capacity, and lipid peroxidation in the hepatopancreas and muscle of the juvenile shrimp Litopenaeus vannamei (weighing 1.26 ± 0.023 g). Five diets (37% protein, 10% lipid) consisting of 0 (control), 1.25%, 2.50%, 5.00% and 10.00% (w/w) M. flexuosa fruit pulp were formulated and provided to the shrimps (n = 50 per tank, treatments in triplicate) for 31 days. Results showed that there were no significant differences between the treatments in terms of the growth capacity, chromaticity parameters, muscle composition and total flavonoid content of shrimps (p > .05). However, the carotenoid content in the muscle and hepatopancreas of the shrimps was significantly increased due to the dietary carotenoids present in M. flexuosa fruit pulp (p

This study investigated the effects of the use of the inclusion of acai on the diet of shrimp Litopenaeus vannamei on antioxidant and histopathological responses after exposure to ammonia. The shrimps were fed two experimental diets: control and with 10% of acai inclusion (W/W), for 35 days. Afterwards, the organisms were exposed at four concentrations of ammonia (0.01‐control; 0.26; 0.48 and 0.91 mg NH₃‐N L⁻¹) for 96 hr. The total antioxidant capacity (ACAP) of the gills decreased significantly in both diets when exposed to ammonia, whereas in the muscle, the acai promoted an increase in ACAP. Concomitantly, lipid peroxidation levels increased in the gills and decreased in muscle. After exposure to ammonia, glutathione‐S‐transferase activity increased in hepatopancreas in shrimps fed with acai facilitating the detoxification of lipid peroxidation by‐products, and the concentration of protein sulfhydryl groups decreased in the gills and muscle of the shrimp of the control diet, evidencing protein damage, an unobserved response in shrimps that received the acai diet. Histopathological changes decreased in acai‐fed shrimps about the control diet after exposure to ammonia. It is concluded that acai mitigated ammonia‐induced histopathological changes, improved the antioxidant defence system (gills and muscle) and attenuated the lipid damage in the muscle.

This research evaluated the effect of the simultaneous substitution of fish meal and fish oil at 0, 30, 50, 70 and 100% (termed SS0, SS30, SS50, SS70 and SS100, respectively) with both Spirulina (Arthrospira platensis) and linseed oil. The effect on growth, colour, fatty acid (FA) profile, and liver and muscle antioxidant response in mullets (Mugil liza) were evaluated. A full substitution was not possible due to a final body weight reduction (p 0.05). The colorimetric analyses showed an improvement in fillet colouration (p 0.05). Also, we found a saturation of carotenoids in muscle at 30% substitution. The content of highly unsaturated fatty acids - HUFA (DHA, EPA and ARA) in muscle diminished as the substitution level increased and, at the same time, the level of these FAs in the diet diminished. We found interesting evidence of elongation from 18:3n-3 to 20:3n-3 when substitution with linseed oil levels was above 50% but no desaturation to 20:4 or 20:5n-3 was found, which could insinuate a certain n-3 HUFA requirement under the experimental conditions. Moreover, we noted an increase in the antioxidant capacity up to the treatment SS70; the SS100 treatment showed a diminution in the antioxidant capacity. It is concluded that a partial inclusion of Spirulina and linseed oil (50%) is possible, and that this replacement can increase antioxidant responses, improve its growth performance and can modulate the mullets fillet quality without affecting negatively fillet fatty acid content.

The addition of pure carotenoids is a common practice in some aquaculture species production since its use in fish feed is known to improve carcass and antioxidant capacity. Spirulina (Arthrospira) cyanobacteria are a rich source of carotenoids that has proven health benefits for fish welfare. In the current experiment, four isonitrogenous (38%) isolipidic (9%) diets were made, including a control diet (free of β-carotene and Spirulina, SP0), β-carotene diet (50 mg kg−1, β0), and two Spirulina (Arthrospira platensis) diets with 2% (SP2) and 4% (SP4) of total feed inclusion. The experimental diets were given to juvenile mullets in a controlled recirculation system. The parameters evaluated were growth, colour, total carotene content of muscle, and antioxidant capacity of the liver and muscle. Significant differences were found (p

Background: Cyanobacterium Athrospira platensis (Spirulina) is a potential fishmeal (FM) substitute in fish diets because of its high protein content, antioxidant and immunostimulant properties. Objective: To evaluate the effects of total and partial substitution of FM with A. platensis (0, 30, 50, 70 and 100% substitution) in juvenile mullet (Mugil liza). Methods: Juvenile mullets (n=210) were maintained in a recirculation system under optimal water parameters for the species. Mullets were fed five experimental diets for 80 days. Each diet was tested in triplicate tanks. At the end of the experimental period growth parameters were measured and samples of blood, liver and spleen were taken to evaluate the immune system. Results: Full replacement (100%) of FM resulted in growth deficits and low survival. The FM replacement induced changes in the proportion of macrophages and lymphocytes. Up to 50% FM replacement increased the expression of CD3 receptors in spleen T lymphocytes (T-Cells), whereas >50% FM replacement decreased the expression of CD3 receptors. We also found that partial FM substitution diminished the apoptotic process. Conclusions: Up to 50% FM substitution with A. platensis can improve performance of non-specific immune system of mullets.Keywords: apoptosis, CD3, fish, immunostimulant, microalgae, Spirulina. ResumenAntecedentes: La cianobacteria Arthrospira platensis (Spirulina) puede usarse como substituto potencial de la harina de pescado (HP) por su alto contenido de proteína, sus antioxidantes y sus propiedades inmunoestimulantes. Objetivo: Analizar el efecto de la substitución parcial y total de HP por A. platensis (0, 30, 50, 70 y 100% de substitución) en juveniles de lisa (Mugil liza). Métodos: Juveniles de lisa (n=210) se mantuvieron en un sistema de recirculación con parámetros de calidad de agua en niveles óptimos para la especie. Las lisas se alimentaron con las dietas experimentales durante 80 días. Cada dieta fue evaluada en triplicado. Al final del periodo experimental se midieron los parámetros de crecimiento y se colectaron muestras de sangre, hígado y bazo para evaluación del sistema inmune. Resultados: La substitución total (100%) resultó en deficiente crecimiento y baja sobrevivencia. El remplazo de HP produjo cambios en las proporciones de macrófagos y linfocitos. La substitución de hasta un 50% HP aumentó la expresión de receptores CD3 en linfocitos T del bazo. Por otro lado, la substitución mayor a 50% HP disminuyó la expresión de receptores CD3. La substitución parcial de HP disminuyó el proceso de apoptosis. Conclusiones: Proponemos una substitución de HP del 50% por A. platensis, lo cual mejora el desempeño del sistema inmune no especifico de las lisas.Palabras clave: apoptosis, CD3, inmunoestimulante, microalga, pez, Spirulina. ResumoAntecedentes: A cianobactéria Athrospira platensis (Spirulina) é um potencial substituto da farinha de peixe (FP) pelo seu alto conteúdo de proteína, antioxidantes e características imune estimulantes. Objetivo: Foram avaliados os efeitos da substituição parcial e total da FP por A. platensis (0, 30, 50, 70 e 100% substituição) em juvenis de tainha (Mugil liza). Métodos: Juvenis de tainha (n=210) foram mantidos em um sistema de recirculação com os parâmetros da água sendo mantidos em níveis ótimos para a espécie. As tainhas foram alimentadas com as dietas experimentais por 80 dias, cada dieta foi testada em triplicata, ao final do período experimental foram avaliados os parâmetros de crescimento e amostras de sangue, fígado e baço foram coletadas para a avaliação do sistema imune. Resultados: A substituição total de FP resultou em redução do crescimento e baixa sobrevivência. A avaliação do sistema imune demostrou que a substituição da FP produz alterações nas proporções de macrófagos e linfócitos. Provou-se que até 50% de substituição da FP incrementa a expressão de receptores CD3. Além disso, a substituição parcial da FP diminui o processo de apoptose. Conclusão: Baseado em nossos descobrimentos, se propõe a substituição de até 50% da FP por A. platensis que melhorará o desempenho do sistema imunológico não específico das tainhas.Palvras-chave: apoptosis, CD3, estimulante, imune, microalga, peixe, Spirulina.

The objective of the present study was to evaluate the use of fermented and non-fermented whole rice bran for rotifer feeding, based on the effects on growth parameters, antioxidant and oxidative damage responses, and water quality. The study was based on three experiments, which compared the effect of different concentrations of non-fermented whole rice bran, the effect of different concentrations of fermented whole rice bran and the effect of the best concentrations of fermented and non-fermented whole rice bran, as well as the replacement of part of the baking yeast by rice bran. The results showed the best growth performances in treatments with 0.7 g yeast with 1.5 g fermented rice bran, 0.35 g yeast with 0.75 g whole rice bran, and 0.35 g yeast with 0.75 g fermented rice bran. Fermentation of rice bran for 6 hours did not induce oxidative stress in rotifers. This work revealed that the use of 1.5 g of fermented bran and replacement of 50% of yeast with fermented or non-fermented rice bran may be used for rotifer feeding, with the additional benefit of improving the environmental quality due to the lower amount of ammonia released in the water.

With the productive intensification of fish farming, the partial or total replacement of fishmeal by ingredients of plant origin became a reality within the feed industry, with the aim of reducing costs. However, this practice increased the impact of mycotoxin contamination. Studies have shown that mycotoxins can induce various disorders in fish, such as cellular and organic alterations, as well as impair functional and morphological development, and, in more severe cases, mortality. Thus, studies have been conducted to evaluate and develop strategies to prevent the formation of mycotoxins, as well as to induce their elimination, inactivation or reduction of their availability in feed.

Five isonitrogenous and isolipidic diets were prepared with different inclusion levels of Gracilaria domingensis (GD; 0%, 5%, 10%, 15%, and 20%) with the objective to test its effects on gr...

This study evaluated the effects of dietary supplementation with different concentrations of chitosan from shrimp tailings on the antioxidant and immune systems of juvenile Litopenaeus vannamei cultivated in a biofloc system (BFT) and subjected to abrupt salinity reduction. The experiment was performed with juvenile shrimp fed diets supplemented with four levels of chitosan: C0 (0 g kg−1 diet – control), C1 (1 g kg−1 diet), C3 (3 g kg−1 diet), and C5 (5 g kg−1 diet). After 35 days, the shrimp were exposed to an acute reduction in salinity from 30 to 5 for 24 h, and the hemolymph, gills, and hepatopancreas were collected. No significant differences were found in the growth performance and survival among treatments. In the gills, acute salinity reduction increased the activity of catalase (CAT), although this effect was reversed by the 5 g kg−1 diet (C5). Furthermore, glutathione-S-transferase (GST) activity was maintained at the basal level in shrimp fed a 1 g kg−1 diet (C1) but reduced in those fed C3 and C5. We also identified a reduction in lipid peroxidation in shrimp fed the C3 and C5 diets. In the hepatopancreas, the GST activities and glutathione (GSH) levels were higher in shrimp supplemented with chitosan, which showed a protective effect. Saline stress and chitosan supplementation did not affect differential hemocyte counts. In conclusion, the results of this study suggest that dietary intake of chitosan could enhance some antioxidant defenses of L. vannamei farmed in a BFT system. Thus, the inclusion of at least 1 g kg−1 chitosan could represent a good alternative to improve defense mechanisms and stress resistance, and it could also contribute to the development of sustainable aquaculture.

A anestesia tem sido utilizada em aquicultura como técnica para facilitar a manipulação dos animais e amenizar o estresse causado pelos procedimentos de manejo. O presente estudo teve como objetivo determinar a eficiência de quatro fármacos como anestésico em juvenis de tainha Mugil liza. Os peixes (6,9 ± 1,4 g) foram submetidos individualmente (N=10 por concentração) í­Â anestesia utilizando-se quatro concentrações de benzocaí­­na (30, 40, 50 e 60 mg L-1), MS-222 (100, 125, 150 e 175 mg L-1), eugenol (50, 70, 90 e 110 mg L-1) e mentol (175, 200, 225 e 250 mg L-1). O critério utilizado para avaliação das melhores concentrações foi a faixa de tempo máximo de três e cinco minutos para anestesia e recuperação dos peixes respectivamente. As concentrações mais eficientes foram: benzocaí­­na, 50 mg L-1; MS-222, 150 mg L-1; eugenol, 70 mg L-1; e mentol, 225 mg L-1.

The aim of this study was to determine the isotopic-turnover rate (RIT ) and trophic-discrimination factor (FTD ) in muscle tissues of Lebranche mullet Mugil liza fed an experimental diet (δ13 C = -27·1‰; δ15 N = 1·0‰). Juvenile M. liza exhibited a relatively fast RIT , with a half-life (t50 ) of only 16 and 14 days for δ13 C and δ15 N respectively and a nearly complete isotopic turnover (t95 ) of 68 and 60 days for δ13 C and δ15 N.

This experiment evaluated the efficacy of benzocaine to reduce stress response during transport of juvenile cobia. Fish (30 g) were packed in bags and transported for 8 h (stocking density = 10 g L-1). Three concentrations of benzocaine were evaluated: 0, 2, and 6 mg L-1. Blood samples were taken for glucose and hematocrit before transportation, and then at 0, 2, 24, and 48 h after. Water quality parameters were verified. No mortality was observed. Total ammonia nitrogen was higher (2.46 mg L-1) and pH was lower (6.92) at 2 mg benzocaine L-1. There was an increase in blood glucose for all treatments on arrival, and it was higher for those exposed to benzocaine at 6 mg L-1, although at 48 h they were all similar. The hematocrit did not differ among treatments. The results suggest: 1) the density 10 g L-1 is considered safe for juvenile cobia transport; 2) benzocaine did not mitigate stress response on cobia during transport, therefore its use is not recommended for this purpose.

Although aquaculture is among the fastest growing food production sectors in the world, one of the bottlenecks for the continuity of its expansion is the dependence of animal protein on commercial feed formulations. Vegetable proteins are an alternative due to the low cost and high availability. However, this protein source is accompanied by a series of antinutritional and pro-inflammatory compounds, including phytate. Phytases can be added in feed for phytate degradation and increase nutrient availability. However, the use of purified phytases significantly increases the production costs. An interesting alternative is to use probiotics genetically modified as bioreactors for phytase production. In the present study, a strain of Bacillus subtilis secreting a fungal phytase was used to evaluate the effect of a feed with high content of soybean meal on zebrafish (Danio rerio). We analysed the condition factor (K) of fish, and the expression of genes related to the immune system, inflammatory response and oxidative. stress. The results obtained demonstrate that the transgenic probiotic was efficient in improving the fish condition factor, stimulating the immune system, reducing the inflammatory response and oxidative stress. Thus, probiotics acting as phytase bioreactors can be considered an interesting tool for the adaptation of commercial species to feed of lower cost.

RESUMO Este trabalho teve como objetivo avaliar o efeito da substituição da farinha e do óleo de peixe pelo concentrado proteico de soja e óleo de soja, na sobrevivência, no crescimento e na composição corporal dos camarões (Litopenaeus vannamei) produzidos em sistema de bioflocos (BFT). Foram formuladas cinco dietas, isoproteicas e isoenergéticas, com diferentes níveis de substituição da farinha e do óleo de peixe por concentrado proteico de soja e óleo de soja, sendo os tratamentos designados como: 0% (sem substituição), 25%, 50%, 75% e 100%. As rações foram elaboradas para conter aproximadamente 35% de proteína e 8% de lipídios. O experimento foi conduzido durante 49 dias, com juvenis com peso inicial de 2,93±0,83g, em sistema de bioflocos (BFT). Não foram encontradas diferenças significativas entre os tratamentos até 75% de substituição para as variáveis de ganho de peso, conversão alimentar e sobrevivência. O tratamento de 100% de substituição apresentou menor taxa de crescimento específico. O presente resultado sugere que, nas dietas para camarões criados em sistema bioflocos, a farinha e o óleo de peixe possam ser substituídos em até 75% por concentrado proteico de soja e óleo de soja, sem prejudicar o desenvolvimento dos animais. ABSTRACT The objective of this work was to evaluate the effect of the substitution of fishmeal and fish oil with soy protein concentrate and soybean oil on survival, growth and body composition of shrimp (Litopenaeus vannamei) produced in biofloc system (BFT). Five diets were formulated to be isoproteic and isoenergetic with different levels of substitution of fishmeal and fish oil with soy protein concentrate and soybean oil. The treatments were named as: 0% (without substitution), 25%, 50%, 75% and 100%. The diets were formulated to contain approximately 35% protein and 8% lipids. The experiment was conducted for 49 days, with juveniles with initial weight of (2.93±0.83g) in a biofloc system (BFT). No significant differences were found between treatments up to 75% of substitution for the variables of weight gain, feed conversion ratio, and survival. The 100% substitution treatment showed a lower specific growth rate. The present study suggests fish meal and fish oil can be substituted in up to 75% for soy protein concentrate and soybean oil, without harming the development of the shrimps when reared in biofloc system.

Este estudo investigou o uso de enzimas exógenas em dietas para juvenis de pampo prateado Trachinotus marginatus. Foram preparadas seis dietas (43% de proteí­­na, 8% de lipí­­dio), contendo 0 (TC), 25 (T25), 50 (T50), 100 (T100), 250 (T250) e 500 (T500) mg kg-1 do complexo enzimático Rovabio ® Max AP. Avaliou-se os efeitos sobre o crescimento, composição de carcaça, ní­­veis de glicogênio e triglicerí­­deo no fí­­gado e possí­­veis alterações na morfologia do intestino e fí­­gado. Os resultados mostraram diferença significativa (p < 0,05) no desempenho de crescimento dos peixes dos tratamentos T100, T250 e T500, com grande concentração de triglicerí­­deos e alteração na morfologia do fí­­gado nos peixes dos tratamentos T250 e T500. A concentração de cálcio nos ossos também teve um aumento significativo (p < 0,05) nos peixes dos tratamentos T50, T100 e T250 em relação ao controle. Entretanto, não houve diferença significativa (p > 0,05) na composição de carcaça, morfologia do intestino e concentração de glicogênio no fí­­gado.Esses resultados indicam que o uso de 100 mg kg-1 de enzimas na dieta mostrou ser o melhor ní­­vel de inclusão para juvenis de pampo prateado, favorecendo o crescimento e a concentração de cálcio nos ossos. Sem efeitos significativos sobre os ní­­veis de triglicerí­­deos no fí­­gado

Stable isotopes are useful tools for studying species residency and movement in aquatic environments. Yet, many questions about their use still remain, mostly related to assumptions that should be experimentally validated, such as turnover rates and discrimination factors. Salinity is a key environmental variable that may influence turnover and discrimination factors, but its effects have not been tested. A controlled diet-shift experiment was conducted with whitemouth croakers (Micropogonias furnieri), a euryhaline species, to determine the turnover rates and diet-tissue discrimination of carbon (δ13C) and nitrogen (δ15N) stable isotopes in muscle tissue. Fish captured in Patos Lagoon, Brazil were distributed into three independent recirculating aquaculture systems with salinities adjusted to represent freshwater, estuarine and marine environments, and fed for 90 days on an isotopically distinct diet. Half-life estimates were longer for both isotopes in the freshwater group (δ13C = 25.6 days, and δ15N = 34.6 days) compared to the estuarine (δ13C = 18.7 days, and δ15N = 23.9 days) and marine treatments (δ13C = 17.7 days, and δ15N = 22.3 days). Overall, carbon isotopic turnover was mainly driven by catabolism, whereas growth was the main factor responsible for nitrogen turnover. Trophic discrimination factors (TDFs) for carbon isotope were similar between fresh and estuarine treatments (TDFfinal = 0.82 ± 0.54‰ and 0.88 ± 0.58‰, respectively), but higher in marine (TDFfinal = 1.44 ± 0.66‰). Hence, in addition to providing species-specific isotopic parameters of a widespread sciaenid in the western Atlantic Ocean crucial to elucidate residence time along salinity gradients, these findings provide lab-based evidence of salinity effects on diet-tissue discrimination of a euryhaline species.

The effects of salinity on growth and parameters related to osmoregulation and energy turnover were evaluated in juvenile pompano Trachinotus marginatus . In a first experiment, fish were reared at different salinities (4, 8, 12, 16 and 20 ppt) for 15 days. No fish mortality was observed. Also, no significant difference in fish size (length and weight), hematocrit and plasma glucose concentration was observed among treatments. Although a significant increase in plasma Na + , Cl − and K + concentrations was noted with increasing water salinities, while no significant changes in plasma osmolality were observed. The isosmotic point was calculated as 357.5 mOsm/kg H 2 O, corresponding to the osmolality of the ambient water at salinity 13.1 ppt. These findings indicate that juvenile pompanos T. marginatus acclimated to 20 ppt are fully acclimated to a wide range of salinities (4–20 ppt) after 15 days of transfer to the new salinity condition. Also, they show that the plasma isosmotic point of juvenile T. marginatus (13 ppt) is within the range of values reported for some euryhaline teleost fish from different habitats (10–14 ppt). In a second experiment, fish were reared at different salinities (3, 6, 12 and 32 ppt) for 28 days. No significant difference in survival, feed conversion, Fulton's condition factor, body weight coefficient of variation, feed intake and intestinal trypsin activity was observed among salinity treatments. However, fish reared at 32 ppt showed lower body weight, specific growth rate, oxygen consumption, and gill Na + ,K + -ATPase activity than those reared at 3 and 6 ppt. Also, their gills showed higher chloride cell area, epithelium thickness, chloride cell density and mucous cell density than those of fish reared at 3, 6 and 12 ppt. These findings indicate that juvenile pompano T. marginatus is euryhaline in the range of salinities tested (3–32 ppt) and grows better when reared at low salinities (3–6 ppt) for 28 days. This performance is associated with a good osmoregulatory ability resulting from structural and biochemical adaptive responses of the gill epithelium to salinity changes paralleled by increased aerobic metabolism and elevated use of liver carbohydrate store. Although it would be cost effective to maintain higher salinities in coastal aquaculture systems given the proximity to the marine environment, our findings support the idea of rearing juvenile pompano T. marginatus in low salinities (3–6 ppt) to improve growth. Statement of relevance Pompano rearing performance is improved in low salinities.

The present study was conducted to evaluate the effects of two commercial yeast products (Y1 and Y2) that were administered via Artemia sp. enrichment on the survival, growth, histomorphometry, immunohistochemical and stress tolerance of pejerrey larvae. The larvae received enriched Artemia for 20 days. After 20 days post-hatch (dph), a saline stress test was conducted with 10 larvae tank− 1. The remaining larvae were kept for ten days (until 30 dph) being fed with dry feed without yeast supplementation. The samples were taken at 0, 10, 20 and 30 dph for weight, length, histological and immunohistochemical analysis. The results showed that the larvae fed with hydrolyzed yeast presented a higher weight and specific growth rate than did those fed Artemia without yeast. However, there was no effect on survival or condition factor. Regarding the histological analyses, no difference was observed on intestinal morphology. Hydrolyzed yeast appears to have a positive influence on the area and diameter of the kidney and thymus. The specific label of CD3 for kidney, spleen and thymus revealed that Y1 and Y2 have a significantly higher percentage of labeled cells. The kidney and thymus of larvae that received yeast displayed significantly more CD4-labeled cells. The control and Y2 groups were significantly more sensitive when subjected to salinity of 60‰. Our findings indicate that Artemia enriched with yeast may promote growth and immunity and the persistence of these parameters for ten days after the last hydrolyzed yeast supplementation. Furthermore, enhanced stress tolerance of pejerrey larvae was observed. Statement of relevance The larviculture is a very sensitive moment, since the immune system is not fully developed, resulting in a greater vulnerability to diseases. In this study we found that, besides presenting performance improvement, hydrolyzed yeast supplementation also improves the marine pejerrey larvae immune response and resistance to salinity stress.