Metabolic responses of matrinxã, Brycon amazonicus (Spix & Agassiz, 1829), exposed to environmental nitrite

Nitrite is usually found in aquatic environments where nitrification process occurs. This ion can cause several injuries to aquatic species, particularly fish. Nitrite reacts with haemoglobin yielding the non‐functional methaemoglobin, which leads to many physiological consequences such as functional anaemia and supposed hypoxia. Metabolism of the freshwater teleost matrinxã, Brycon amazonicus, exposed to environmental 0.6 mg L^?1 of nitrite N‐NO₂^? for 96 h was studied, and the fermentative/oxidative preference was gauged. Concentrations of glycogen, glucose, lactate, pyruvate and ammonia, plus the activities of lactate, glutamate and malate dehydrogenase were assayed. The exposure resulted in a metabolic profile that allowed inferring the continuity of oxidative metabolism. Catabolism of amino acids prevailed or was apparently exacerbated by inferred branchial injury and consequent impairment of nitrogen excretion. Moreover, the studied enzymes glutamate dehydrogenase, lactate dehydrogenase and malate dehydrogenase from brain and heart were little affected by nitrite. The expected fermentative metabolism due to the high methaemoglobin formation was not observed.     

Light intensity affects the survival and growth of matrinxã larvae,Brycon amazonicus (Spix & Agassiz, 1829)

We evaluated the effect of light intensity on survival rate and zootechnical performance in matrinxã larvae (Brycon amazonicus) that is an important species for fish farming in the Amazon region. For this, the larvae were submitted to three experimental stages : Stage I—10–72 hr after hatching (HAH), Stage II—72–168 HAH and Stage III—168–288 HAH. The animals were submitted to three treatments of different light intensities: low (±20 lx), intermediate (±200 lx) and high (±2,000 lx). The low light intensity increased the survival rate in 24, 48, 72, 120, 168 and 288 HAH. The size of the animals was homogeneous in 72 and 168 HAH in the low and intermediate treatments. The high light intensity increased the zootechnical parameters in 288 HAH. We suggest the use of low light intensity in the initial periods of observation (24 and 48 HAH) to reduce aggressiveness and increase the survival and homogeneity of the animals. On the other hand, it is possible to suggest an increase in the light intensity in the final period of observation (288 HAH), as the increase in intensity stimulated growth and affected the survival rate of the matrinxã larvae.     

Biochemical responses of matrinxãBrycon cephalus (Günther, 1869) after sustained swimming

Juvenile matrinxã, Brycon cephalus, were submitted to sustained swimming for 72 days at 1.0 body length s^?1. Exercised fish (EF) grew more than non‐EF and their feed conversion ratio (FCR) improved; haematological responses demonstrated a decrease in haemoglobin and mean cell haemoglobin contents and increase in the mean cell volume. In the plasma, sodium, ammonia and amino acid concentrations increased; plasma triglycerides decreased while free fatty acids increased. Liver glucose, free amino acids, ammonia, the rate protein per fish weight and total lipid content increased, while the glycogen per fish ratio declined. Glutamate dehydrogenase (GDH) activity increased while pyruvate kinase (PK) and lactate dehydrogenase (LDH) decreased. White muscle glucose, lactate, the glycogen per fish‐weight ratio and total lipid content exhibited a decrease in their values; ammonia, free amino acids and the protein per fish‐weight ratio increased. GDH and PK decreased their activities. In the red muscle glycogen store, the glycogen per fish‐weight ratio and glucose were reduced. Juvenile matrinxãs, under sustained swimming, were physiologically and biochemically adapted to exercise as indicated by improved blood flow, transport and oxygen uptake, FCR, amino acid and protein incorporation and growth. Continuous exercise is a good practice for B. cephalus cultivation.     

注射T4对日本鳗鲡血清、卵、早期幼苗甲状腺激素含量变化及对幼苗存活率的影响

对产卵前的雌鳗注射了不同剂量的甲状腺素(T4),然后利用放射性免疫法(RIA)测定了雌鳗血清、卵、胚胎及幼苗各发育时间段三碘甲腺原氨酸(T3)和甲状腺素(T4)的含量变化。结果发现,注射外源T424h后,随着雌鳗血清中的T4含量达到峰值,T3含量也达到了峰值。说明日本鳗鲡体内存在5’-单脱碘酶。与此同时,随着血清中T3和T4含量达到峰值,卵中的T3和T4含量也达到了峰值,进而证明母体中的T3和T4能够转入鳗鲡幼苗。进一步调整T4的注射剂量和时间后发现,在21℃水温条件下,T4的剂量为10～15mg·(500g)-1时,注射催产针前12h注射的效果最好。用该方法注射T4后,幼苗各发育时间段的存活率与对照组比较存在显著差异,出膜第9天的存活率由对照组的1.3%提高到22.0%。但日本鳗鲡幼苗最终未能存活,说明甲状腺素并不是影响日本鳗鲡幼苗存活的唯一因素。     

The influence of dietary protein and energy levels on growth, survival and thyroid hormone (T3 and T4) composition of Lates calcarifer larvae

Two growth trials were conducted to determine the effects of different dietary protein (450–550 g kg^?1) and energy contents (18–22 MJ kg^?1) on growth, survival and carcass thyroid hormone (T3 and T4) levels of barramundi (Lates calcarifer) larvae. Larvae fed diets containing 21 and 22 MJ kg^?1 dietary energy performed consistently better than those fed diets containing 18 and 19 MJ kg^?1 dietary energy in terms of final dry weight and total length, while those fed 20 MJ kg^?1 had intermediate values for both the parameters. No effects of dietary protein level were discernable from the physical parameters measured; however, larvae fed diets containing the lowest protein and energy combination (450 g kg^?1 protein/18 MJ kg^?1 energy) had significantly lower carcass T4 levels than larvae in all other treatments, except for those fed the 500 g kg^?1 protein/18 MJ kg^?1 diet, which had an intermediate value. The results indicate that the optimum diet for L. calcarifer larvae from 14 to 28 days after hatch should contain 500 g kg^?1 protein and a minimum of 21 MJ kg^?1 dietary energy. Carcass T4 content was influenced by macronutrient inclusion level, and correlated significantly with growth, described by the total length. Reduced T4 levels may indicate a depressed larval status in this species.     

Improvement of ovulation induction by additive injection of 17,20β‐Dihydroxy‐4‐pregnen‐3‐one after human chorionic gonadotropin administration in a pelagic egg spawning marine teleost,nibe croaker Nibea mitsukurii (Jordan & Snyder)

This study aimed to develop the consistent ovulation induction method in a pelagic egg spawning marine teleost, nibe croaker Nibea mitsukurii. Attempts to induce oocyte maturation and ovulation in nibe croaker using human chorionic gonadotropin (hCG; 0.5 IU g^?1) resulted in the normal progression of oocyte maturation and hydration, but a failure to induce ovulation in many individuals. This ovulation disorder was similarly observed even when the dose of hCG was increased 10 times (5 IU g^?1) or decreased to one tenth (0.05 IU g^?1), indicating that it cannot be completely overcome solely by hCG administration. However, this ovulation disorder could be completely overcome by subsequent administration of 17,20β‐dihydroxy‐4‐pregnen‐3‐one (DHP) at the appropriate dose (0.5 μg g^?1) and time (20 h after hCG administration). An increase in the number of individuals that ovulated due to DHP administration led to an increase in individuals producing larvae, resulting in an approximately threefold increase in the estimated number of larvae produced compared with the group of fish administered hCG alone. Thus, this ovulation induction method using DHP administration after hCG was demonstrated to overcome the ovulation disorder in nibe croaker and could be applicable to commercially important species with similar ovulation problems.     

Growth performance, body composition and plasma thyroid hormone status of channel catfish (Ictalurus punctatus) in response to short-term feed deprivation and refeeding

A 6-week feeding trial was conducted to investigate the effects of short-term feed deprivation on inducing compensatory growth and changes in thyroid hormone levels of channel catfish. Feeding treatments consisted of the following four regimes of 2-week duration: satiate feeding (control), no feed for 3 days then feeding to apparent satiation for the next 11 days, no feed for 5 days then feeding to apparent satiation for 9 days, and no feed for 7 days then feeding to apparent satiation for 7 days. These regimes were repeated three times over the 6-week trial in which 25 channel catfish fingerlings, initially averaging 15 g each, were stocked into each of 12, 38-l glass aquaria supplied with supplemental aeration and flow-through water. Depriving fish of feed had a pronounced effect in that fish lost weight in as little as 3 days. Returning the fish to a satiate feeding regime caused a resumption of growth, equal to control growth only in the case of the 3-day deprived treatment, but all periods of feed deprivation failed to induce a period of catch-up growth adequate to compensate for previously lost weight. Feed efficiency also was not improved by the periods of feed deprivation, and restricting feed in excess of 3 days lowered feed efficiency. Fish condition indices were not altered at the termination of the trial. Muscle lipid, muscle protein and liver protein also were not different among feeding regimes. Liver lipid was elevated in fish deprived of feed for more than 3 days every 2 weeks. Plasma thyroxine (T₄) and triiodothyronine (T₃) were equally depressed by 3 days from the onset of feed deprivation. Both hormones rose significantly within 24 h of realimentation, with the greatest increase observed in animals subjected to the briefest feed deprivation. These results support a role for thyroid hormones in the promotion of growth in channel catfish. Whereas feed deprivation appears to rapidly reduce activity of the hypothalamo-pituitary-thyroid axis, the high correlation observed between T₄ and T₃ in all treatments suggests that peripheral deiodinating systems are capable of rapidly generating T₃ from T₄ upon realimentation. More rapid recovery of thyroid hormone production following realimentation may minimize the effects of feed deprivation on growth and feed efficiency of fish subjected to the 3-day deprivation treatment when compared to longer periods.     

Estimation of Arachidonic Acid Requirement for Improvement of Pre‐maturation Growth and Egg and Larval Quality in the Female Blue Gourami (Trichopodus trichopterus; Pallas, 1770): A Model for the Anabantidae Family

This study investigates the dietary arachidonic acid (ARA) requirement from juvenile to maturation stage in an anabantid model fish, the blue gourami, Trichopodus trichopterus. Specifically we determined the optimum dietary ARA content to maximize juvenile growth and subsequent sexual maturation and to improve the quality of their eggs and offspring. Five experimental diets containing 0.02, 0.53, 1.05, 1.60, and 2.12% ARA (of dry weight) were fed to juveniles over 5 mo. The results showed that whole‐body fatty acid profile of broodstock significantly changed in fish fed diets of different ARA content (ANOVA, P < 0.003). The highest contents of 18:2n‐6 and Σn‐6 were obtained in fish fed 0.53% ARA, and a decreasing trend was observed with elevated dietary ARA levels. Monthly specific growth rate (SGR) measurements revealed significant differences in the juvenile stage, but the SGR of broodstock was unaffected by dietary ARA. Protein and ash content of whole‐body broodstock showed no differences among groups, while lipid content decreased as ARA levels increased. Maximum volume of the oocyte was obtained in the 1.05% ARA group, while the yolk sac size increased as dietary ARA increased. The optimum growth and survival of the larvae produced by broodstock were recorded in the 2.12 and 1.6% ARA groups, respectively. It was concluded that despite the presumed ability of freshwater fish to synthesize and meet their highly unsaturated fatty acid requirements, dietary ARA higher than 1.05% had significant stimulatory effects on growth of juveniles but no obvious influence on the growth of matured fish. Also, higher ARA levels (1.6–2.12%) were found to improve the quality of eggs and offspring.     

Growth,biochemical composition,innate immunity and histological performance of the juvenile humpback grouper (Cromileptes altivelis) after treatment with recombinant fish growth hormone

Humpback grouper take a long time to grow to marketable size. In this study, recombinant Epinephelus lanceolatus growth hormone (rElGH) was applied orally and by intraperitoneal injection to accelerate their growth. Daily application of crude rElGH at a dose of 50 mg kg^?1 in commercial diet for 42 days or with injections of 0.2 μg rElGH g^?1 total body weight every 2 weeks resulted in significant increases in growth performance, protein and lipid content, plasma glucose, liver glycogen and innate immunity compared to control groups. Relative weight gain from the oral and injection doses above compared to C? (Control negative, only commercial diet without rElGH treatment or chemical substances related to treatment, either for oral or injection route) were 40.25% and 38.77%, respectively. There was no specific histological damage to the kidneys, liver or spleen that was attributable to rElGH administration. These results strongly suggested that the stimulation of growth and immunity following oral and intraperitoneal administration was due to a specific action of rElGH and that recombinant GH is safe for fish consumption.     

Effects of photoperiod and night‐time aeration rate on swim bladder inflation and survival in Pacific bluefin tuna,Thunnus orientalis (Temminck & Schlegel), larvae

Success of swim bladder inflation (SBI) is crucial for early survival of Pacific bluefin tuna (PBF) larvae, because it reduces larval sinking death by enhancing buoyancy. In Experiment 1, we examined the effect of photoperiod on SBI and survival in PBF larvae by comparing photoperiods of 9L: 15D (9L), 14L: 10D (14L: natural photoperiod), 19L: 5D (19L) and 24L: 0D (24L) during 2–10 days post hatch (dph). In Experiment 2, the combined effects of photoperiod (24L and 14L) and nighttime aeration rate (enhanced night‐time aeration: ENA of 1300 mL min^?1 as a countermeasure for sinking death and 130 mL min^?1) on the survival and SBI were also examined during 2–10 dph. Moreover, in Experiment 3 the effect of photoperiod on vertical distribution of larvae in night‐time was examined on 3–5 dph. Photoperiod of 24L in Experiment 1 significantly inhibited SBI compared with 14L and 19L; nevertheless, it significantly improved survival compared with other photoperiods with a dark period. On the other hand, the shortened light period (9L) showed significantly reduced SBI and also survival. In Experiment 2, the countermeasure for sinking death of ENA under 24L did not further improve the survival; rather it tended to reduce the survival. In Experiment 3, larvae distributed less in the bottom layer in 24L than in 14L, suggesting the reducing effect of 24L on sinking death. The results indicate that 24L without ENA is suitable for survival which is the most serious problem in PBF larviculture.     

Effects of estradiol‐17β on survival,growth performance,gonadal structure and sex ratio of the tiger puffer,Takifugu rubripes (Temminck & Schlegel, 1850), fingerlings

Systematic research was performed to assess the survival, growth performance, gonadal structure and sex ratio during and after sex reversal induced by estradiol‐17β in tiger puffers. The fish of 20 days after hatching (dah) were immersed in different doses (0.2, 2, 20, 100 ppb) for 60 days. There were significant differences in survival rates among groups (p < .05). With the increase in the estradiol‐17β dose, the survival rates of tiger puffers decreased, revealing a linear regression relationship with log₁₀ (estradiol + 1; p < .05). The growth tendency of fish in the low‐dose group was similar to those in the control group over the same period. The growth in the 20 ppb dose group was significantly slower than in the low‐dose and control groups in fish of same age (p < .05), but was significantly faster than in the 100 ppb dose group (p < .05) after 60 days. Intersex fish were categorized into intersex I, II and III types, according to the feminization degree from low to high. Phenotypic intersex puffer fish were found in the 2, 20 and 100 ppb dose groups. Intersex ratios in 2, 20 and 100 ppb were 10%, 43.3% and 46.7%, respectively, the ratios except the ones in 2 ppb group being significantly higher than those in the control group (p < .05). Moreover, 100.0% male induction for intersex II and III types occurred in 20 and 100 ppb groups. Together, these results indicated that estradiol‐17β at a dose of 20 ppb was most effective for pseudo‐female production.     

Influence of dietary lipid sources on growth,reproductive performance and fatty acid compositions of muscle and egg in three‐spot gourami (Trichopodus trichopterus) (Pallas, 1770)

Five isonitrogenous (420 g kg^?1 crude protein) and isoenergetic (16.3 kJ g^?1) practical diets were formulated to contain fish oil (FO), Kilka fish oil (KFO), linseed (LO), canola (CO) and soybean (SBO) oils fed to juveniles of three‐spot gourami (Trichopodus trichopterus) (initial weight 1 ± 0.03 g) three times per day to apparent satiation for 14 weeks. Results showed the mean final weight of brooders was not significantly affected by dietary oil sources. Specific growth rate for fish fed in SBO and CO diets was statistically higher than for fish fed diet LO. Fish fed diets CO and KFO showed in significantly higher GSI value compared with other diets. Absolute fecundity was greatest in fish fed diets KFO and CO, which significantly differ with other treatments. Except for KFO diet, high fertilization percentages (87.3–93.45%) were observed in other treatments. Fatty acid composition of muscle and egg was found to be positively correlated with their respective dietary lipid sources. High levels of EPA, DHA and n‐3 HUFA in brooders fed diet FO negatively affect egg quality parameters. Therefore, the results demonstrated that vegetable oil‐based diets (CO, SBO and LO, respectively) can positively affect on growth performance of juveniles compared with fish oil‐based diets. Furthermore, CO and LO diets, respectively, showed positive effects on reproductive performance in T. trichopterus compared with fish oil diets during experimental period under controlled conditions.     

Stimulation of growth performance without causing stress response in young red sea bream, Pagrus major (Temminck & Schlegel), by photoperiod manipulation

Three photoperiods (12L:12D, 16L:8D and 24L:0D) were used to investigate the growth performance and stress response in red sea bream, Pagrus major (body weight 200–400 g). Fish were fed a commercial diet to apparent satiation, two times a day for 8 weeks. Fish exposed to a 24L:0D photoperiod showed a significantly higher weight gain (%) than those exposed to other photoperiods (P<0.05). The best specific growth rate and feed conversion efficiency were achieved at 24L:0D and 16L:8D, without significant differences among them. Although fish exposed to 16L:8D showed a significantly higher plasma level of cortisol than those exposed to other photoperiods in the third week, there was no major variation in the cortisol level among the treatments either at the sixth week or at the end of this study. There were no significant differences either in the haematocrit level or the plasma levels of glucose, total cholesterol and total protein among the treatments during this study. The results revealed that the growth performance of red sea bream reared from 200 to 400 g can be stimulated significantly using a continuous (24L:0D) photoperiod without any measurable significant stress response in fish.