Relationship between metabolic and reproductive hormones in salmonid fish

Circulating concentrations of estradiol (E₂), vitellogenin (VTG), thyroxine (T₄), triiodothyronine (T₃) and insulin were measured in reproductively maturing four and five year-old Atlantic salmon. Blood samples were collected from the fish in seawater for one year prior to their spawning in November in fresh water. In females, E₂ and VTG were low but detectable from December to July, and then increased to peak levels in September and October. Plasma levels of T₄ and T₃ were relatively constant in winter and spring, and decreased in July. Plasma concentration of T₄ increased in November when the fish returned to fresh water. Plasma T₃ levels remained low during the autumn. Both T₄ and T₃ levels tended to be higher in males than in females during September through November. Plasma insulin concentrations increased during the spring to peak values in May, and then decreased in June and July in fish of both sexes. There was a significant elevation of plasma insulin in males during October, and the levels in males tended to be higher than those found in females during final maturation.     

Dietary astaxanthin improved the body pigmentation and antioxidant function,but not the growth of discus fish (Symphysodon spp.)

To assess the effects of dietary astaxanthin on the growth and body colour of red discus fish (Symphysodon spp.), synthetic astaxanthin was added into the basal diet (beef heart hamburger) with the levels of 0 (control diet), 50, 100, 200, 300 and 400 mg kg^?1 respectively. The six experimental diets were fed to discus fish with an initial body weight of 10.3 ± 0.8 g for 8 weeks. The results showed that the supplementation of 50–200 mg kg^?1 astaxanthin had no significant effects on growth performance of discus fish, but the high supplementation of astaxanthin (300 or 400 mg kg^?1) significantly reduced the weight gain and increased the feed coefficient ratio (P < 0.05). After 4 or 8 weeks of feeding, the L* (lightness) values in astaxanthin‐supplemented groups were significantly lower, while a* (redness), b* (yellowness) and skin astaxanthin contents were significantly higher than the control group (P < 0.05). When the astaxanthin supplementation reached 200 mg kg^?1, skin redness and astaxanthin contents remained relatively stable. When b* was relatively stable, the supplemental astaxanthin was 300 (4 weeks) and 50 mg kg^?1 (8 weeks) respectively. With the supplemental astaxanthin increasing, the astaxanthin retention rate significantly decreased and hepatic total antioxidant capacity was strengthened. The dietary astaxanthin also significantly increased the reduced glutathione level (P < 0.05) when the astaxanthin inclusion was higher than 50 mg kg^?1. The above results showed that dietary astaxanthin could effectively improve the skin pigmentation of red discus fish in 4 weeks and the supplementation level was suggested to be 200 mg kg^?1.     

Astaxanthin deposition in the flesh of Atlantic Salmon, Salmo salar L., in relation to dietary astaxanthin concentration and feeding period

Atlantic salmon, Salmo salar L., were fed nine experimental diets containing from 0 to 200 mg astaxanthin per kg^?1 for six time periods, ranging from 3 to 21 months, in sea cages at Matre Aquaculture Research Station, Matredal, Norway. The sampled fish had an initial mean weight of 115 g and reached a weight of 3.2 kg at the termination of the experiment. Every third month, 10 fish from each dose and time group were sampled and the astaxanthin concentration in the flesh determined. The amount of astaxanthin in the flesh ranged from 0.7 to 8.9 mg kg^?1 at the termination of the experiment. This paper discusses deposition of astaxanthin in the flesh of Atlantic salmon in relation to dietary carotenoid levels in the 0–200 mg kg^?1 range and feeding times of 3–21 months. Under the conditions of this experiment, no significant effect on astaxanthin deposition rate could be achieved by increasing the astaxanthin level above 60 mg kg dry feed^?1. Atlantic salmon should be fed astaxanthin-supplemented diets during the whole seawater stage in order to obtain maximal astaxanthin level in the flesh.     

Stress responses and disease resistance in salmonid fish: Effects of chronic elevation of plasma cortisol

Basal levels of plasma cortisol in unstressed salmonid fish are normally in the range 0–5 ng ml⁻¹. An acute stress such as handling or 1 h confinement caused a temporary elevation of the plasma cortisol levels of both brown trout,Salmo trutta L., and rainbow trout,Salmo gairdneri Richardson, in the range 40–200 ng ml⁻¹ with a return to basal levels within 24–48 h. The extent of the cortisol elevation in response to an acute stress was dependent upon both the species and strain of trout. Chronic stresses, such as prolonged confinement or crowding, resulted in an elevation of plasma cortisol levels to approximately 10 ng ml⁻¹. Under these circumstances, blood cortisol levels remained elevated for periods of up to 4 weeks before acclimation finally occurred. It is shown, by means of intraperitoneal implantation of cortisol, that chronic elevation of plasma cortisol levels in the brown trout results in a dose-dependent increase in mortality due to common bacterial and fungal diseases. This effect is apparent at plasma cortisol levels as low as 10 ng ml⁻¹, levels below those often reported as being representative of ‘unstressed’ fish. These findings are discussed in relation to the known immunosuppressive effects of corticosteroids in teleost fish.     

不同体质量中华倒刺鲃的静止代谢率和生长性能

为了探讨不同体质量中华倒刺鲃能量代谢和生长能力的差异,在25°C条件下分别测定不同体质量大小(10、20、40、100和180 g组)中华倒刺鲃的静止代谢率(RMR);经过为期28 d投喂养殖实验,测定各实验组的特定生长率(SGR)、摄食率(FR)和饲料转化效率(FE);并测定不同体质量大小(10.4～248.1 g)实验鱼的生长激素(GH)水平。随体质量的增加,中华倒刺鲃个体RMR显著增加,单位体质量RMR显著下降;SGR和FR均显著增加;体质量对FE影响不显著;GH水平与体质量间呈显著负相关(r=-0.753,n=30)。单位体质量RMR与SGR(r=0.586,n=51)和FR(r=0.640,n=51)均呈显著正相关,与FE(r=0.100,n=51)关系不显著;SGR与FR(r=0.956,n=51)和FE(r=0.447,n=30)均呈显著正相关;FR与FE(r=0.245,n=30)关系不显著。研究表明,小体质量中华倒刺鲃具有相对更高的维持能量的消耗和生长潜能,归因于小体质量鱼具有更高的摄食消化及同化能力。     

Effects of dietary astaxanthin concentration and feeding period on the skin pigmentation of Australian snapper Pagrus auratus (Bloch & Schneider, 1801)

A single‐factor experiment was conducted to investigate the effects of dietary astaxanthin concentration on the skin colour of snapper. Snapper (mean weight=129 g) were held in white cages and fed one of seven dietary levels of unesterified astaxanthin (0, 13, 26, 39, 52, 65 or 78 mg astaxanthin kg^?1) for 63 days. Treatments comprised four replicate cages, each containing five fish. The skin colour of all fish was quantified using the CIE L^*, a^*, b^* colour scale after 21, 42 and 63 days. In addition, total carotenoid concentrations of the skin of two fish cage^?1 were determined after 63 days. Supplementing diets with astaxanthin strongly affected redness (a^*) and yellowness (b^*) values of the skin at all sampling times. After 21 days, the a^* values increased linearly as the dietary astaxanthin concentration was increased before a plateau was attained between 39 and 78 mg kg^?1. The b^* values similarly increased above basal levels in all astaxanthin diets. By 42 days, a^* and b^* values increased in magnitude while a plateau remained between 39 and 78 mg kg^?1. After 63 days, there were no further increases in measured colour values, suggesting that maximum pigmentation was imparted in the skin of snapper fed diets >39 mg kg^?1 after 42 days. Similarly, there were no differences in total carotenoid concentrations of the skin of snapper fed diets >39 mg kg^?1 after 63 days. The plateaus that occurred in a^* and b^* values, while still increasing in magnitude between 21 and 42 days, indicate that the rate of astaxanthin deposition in snapper is limited and astaxanthin in diets containing >39 mg astaxanthin kg^?1 is not efficiently utilized. Astaxanthin retention after 63 days was greatest from the 13 mg kg^?1 diet; however, skin pigmentation was not adequate. An astaxanthin concentration of 39 mg kg^?1 provided the second greatest retention in the skin while obtaining maximum pigmentation. To efficiently maximize skin pigmentation, snapper growers should commence feeding diets containing a minimum of 39 mg unesterified astaxanthin kg^?1 at least 42 days before sale.     

体质量和温度对星洲红鱼耗氧率、排氨率和窒息点的影响

利用实验生态学方法研究了不同温度和体质量对星洲红鱼(Red Tilapia)耗氧率、排氨率和窒息点的影响。结果显示:水温15~35℃时,星洲红鱼的耗氧率、排氨率和窒息点都随着温度的上升而上升,差异显著(P0.05);耗氧率(Ro)、排氨率(RA)与温度(T)的线性回归方程分别为:Ro=0.066 4T+0.008 6(R2=0.969 3)和RA=3.849 4t+3.927 5(R2=0.916 8)。在体重27.50~201.87 g范围内,耗氧率和排氨率随着体重的上升而减小,窒息点随着体重的上升而上升,差异显著(P0.05);耗氧率(Ro)、排氨率(RA)与体质量(W)的线性回归方程分别为:Ro=-0.042 2W+0.312(R2=0.989 6)和RA=-4.281 8 W+26.4(R2=0.988 4)。结果表明,不同温度和体质量对星洲红鱼耗氧率、排氨率和窒息点有明显影响。     

Relationship between metabolic rate in vitro and body mass in a marine teleost,porgy Pagrus major

The rate of oxygen consumption of minced whole body was determined volumetrically, as an indication of metabolic rate in vitro (M _{in vitro} ), at 20°C in porgy Pagrus major ranging from 0.0002 g (just after hatch) to 2.9 g (67 days old) in body mass. A triphasic relationship was found between M _{in vitro} of individual fish (l.min^–1) and wet body mass W (g). During the prolarval stage accompanied with the transitional period to the postlarval stage (0.00020–0.00023 g, 0–6 days old), the mass-specific metabolic rate in vitro (M _{in vitro} /W in l.g^–1.min^–1) increased with age (D in days) as expressed by an equation M _{in vitro} /W = 3.88 + 0.74/D. During the postlarval stage (0.00031–0.003 g, 8–22 days old), M _{in vitro} /W remained almost constant, independent of body mass following an equation M _{in vitro} /W = 5.24 W^–0.085. During the juvenile and adolescent stages (0.0047–2.9 g, 30–67 days old), M _{in vitro} /W decreased with increasing body mass following an equation M _{in vitro} /W = 1.66 W^–0.235. These results correspond with the triphasic relationship between metabolism in vivo and body mass observed in intact porgy of 0.0002–270 g (Oikawa et al. 1991). It is concluded, therefore, that the dependence of mass-specific metabolic rate on body size exists in vitro as well as in vivo, during the early stages in the porgy. Based on these results, factors controlling the metabolism-size relationship are discussed.     

Variation in growth rate,liver weight and body composition at first sexual maturity in rainbow trout

Rainbow trout around 743 g were fed four different diets over an 8-month period. Maturing males grew faster in the period before spawning (Sept.–Dec.) than maturing females, and significantly faster than immature fish. Mature fish stagnated in growth while the immature fish surpassed the growth of mature fish during the spawning season. The condition factor was moderately influenced by the maturation process. In the period before spawning (Sept.–Jan.) maturing females had a significantly higher hepatosomatic index than males and immature fish. An increase in dry matter and fat and a decrease of protein were observed in the muscle of maturing males and immature fish towards the spawning season, while maturing females had a slight fall in dry matter and fat and a small increase in protein in the same period. Dry matter and fat in muscle of rainbow trout were positively correlated.     

The influence of dietary astaxanthin and temperature on flesh colour in Arctic charr Salvelinus alpinus L.

Arctic charr Salvelinus alpinus L. averaging 150 g were fed six diets containing from 0 to 192 mg astaxanthin per kilogram dry diet al two temperatures (8 C and 12 C), After reaching an average weight of 320 g (102 days at 12 C and 126 days at 8 C), the fish were killed for evaluation of flesh pigmentation using instrumental colour measurement. There was a positive relationship between dietary astaxanthin and muscle redness up to a dietary concentration of around 70 mg kg^-1, where a plateau in pigmentation was reached. Tail sections were more intensely pigmented compared with the neck and dorsal regions. Within each temperature regime, flesh coloration was positively correlated to specific growth rate. Fish maintained at 8 C had significantly higher pigmentation compared to those grown at 12 C.     

温度对不同体质量灰海马耗氧率、排氨率及窒息点的影响

为探究温度对不同体质量灰海马耗氧率、排氨率和窒息点的影响,设置13、18、23、28、32℃5个温度梯度,用大(L)、中(M)、小(S)3种体质量分别为(3.63±1.42)、(1.23±0.22)、(0.47±0.24)g的灰海马进行代谢试验.试验结果:在13～32℃范围内,随着水温的升高,灰海马的耗氧率和排氨率呈现...     

Epizootiology of Renibacterium salmoninarum, the causal agent of bacterial kidney disease in salmonid fish

Abstract. By use of a selective medium, Renibacterium salmoninarum was recovered from rainbow trout, Salmo gairdneri Richardson. With asymptomatic animals, small numbers of Renibacterium colonies were recovered only from the anterior part of the kidney; whereas in clinically diseased fish, dense pure culture growth was obtained from kidney, spleen, heart, blood, ascitic fluid and faeces. There was no evidence for the presence of R. salmoninarum in the water or sediment of 56 freshwater fish farms in England and Wales. Nevertheless, laboratory–based experiments showed that the pathogen was excreted in the faeces of clinically diseased fish. Moreover, there was survival of the bacterial cells for up to 21 days in sediment/faecal material.     

Relationship between body weight and loading densities in fish transport using the plastic bag method

Abstract. The transportation of live fish in sealed plastic bags was examined. Water parameters and loading densities were analysed. Based on several assumptions an estimation of oxygen consumption during transport was performed indicating that metabolism during transport was about three times higher than routine metabolism. There was some evidence that small fish were more affected by transportation stress, and that large fish need a longer starvation time before transport to reduce ammonia excretion sufficiently.     

Digestibility,growth and pigmentation of astaxanthin,canthaxanthin or lutein diets in Lake Kurumoi rainbowfish,Melanotaenia parva (Allen) cultured species

New cultured ornamental fish namely Lake Kurumoi rainbowfish Melanotaenia parva (Allen) run into reduced of colour performances when reared in the aquaria, consequently, fish feed must be added with carotenoids as a pigment source. The aim of this study was to evaluate the digestibility, growth and pigmentation of astaxanthin, canthaxanthin and lutein in diet. Apparent digestibility coefficients (ADC) of dry matter, lipid, protein, carotenoids, growth and pigmentation were studied in twenty fish after 14 and 56 days of observation. The single‐dose supplementation of 100 mg/kg of astaxanthin, canthaxanthin, or lutein diets on fish was fed by apparent satiation. The basal diet without carotenoids was used as control. The result showed that the ADC of carotenoids of test diets was higher compared to control. Fish fed astaxanthin diet had higher survival rate (96.67 ± 2.89%), colour measurements of lightness (57.60 ± 7.46%), a*‐values (4.66 ± 1.20), total carotenoids content in skin (33.75 ± 5.02 mg/kg) and muscle (2.16 ± 0.74 mg/kg). Astaxanthin also increased the growth after 14 days (2.00% ± 0.19%/days) but there was no significantly different at the end of experiment. The yellowish‐orange colour performance was more rapidly achieved by fish fed astaxanthin diet after 28 days experimentation. These values suggested that dietary carotenoids were required and astaxanthin diet was superior to other diets for skin pigmentation of Lake Kurumoi rainbowfish.     

Larval pigmentation, survival and growth of Penaeus indicus fed the nematode Panagrellus redivivus enriched with astaxanthin and various lipids

The highly unsaturated fatty acid (HUFA) content of the free-living nematode Panagrellus redivivus was successfully increased when three different lipid sources (cod-liver oil, marilla oil and capelin oil) from marine animals were used in the nematode culture medium. The lipid enrichment significantly increased the ω3 HUFA content, particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), of the nematodes compared with lipid non-enriched nematodes. Penaeus indicus larvae fed the lipid-enriched nematodes had significantly ( P < 0.05) greater larval survival (69–77%) until metamorphosis than those fed non-enriched nematodes (54%).
This nematode species was also enriched with astaxanthin to determine the effects of this carotenoid on pigmentation, survival and growth during the larval development of P. indicus . The pigment, delivered via nematodes, significantly ( P < 0.05) improved larval coloration and survival (88%) compared with that of placebo-pigmented nematodes (78%). However, there was no strong evidence to show the benefit of either pigment and/or lipid enrichment on larval growth and development of P. indicus .
This study has shown that the nutritional value of the nematodes can be enhanced by the addition of fish oil into the culture medium. Supplementation of EPA and DHA, together with synthetic astaxanthin, allow the nematodes to be used as a sole diet for the larval culture of P. indicus .     

The relationships between fish health, metabolic rate, swimming performance and recovery in return-run sockeye salmon, Oncorhynchus nerka (Walbaum)

The repeat swimming ability and oxygen uptake (Mo2) of adult sockeye salmon, Oncorhynchus nerka (Walbaum), were assessed at ambient water temperatures at three field locations along their migration route. Following these measurements, internal and external fish condition was evaluated according to United States Environmental Protection Agency guidelines. Here we report on the physiological characteristics of fish having either moderate or severe levels of disease and injury. Routine oxygen uptake (Mo2) did not differ between healthy fish and those with indices of ill health. In contrast, fish classified as sick, which included conditions of damaged internal organs, an Ichthyophonus spp. heart infection, a Saprolegnia spp. gill infection, and skin wounds, had a lower post-exercise Mo2 and were unable to repeat their critical swim speed (U(crit)) on the second swim test. Moderate levels of disease or injury did not significantly affect either U(crit) or post-exercise Mo2. We conclude that the ability of adult salmon to recover quickly from exercise may be a useful indicator of sublethal pathologies.     

盐度和规格对光裸方格星虫耗氧率及排氨率的影响

为研究盐度和规格对光裸方格星虫呼吸代谢的影响,采用实验生态学方法,研究了不同盐度梯度(15、20、25、30和35)对3种规格S(2.11±0.60)g、M(6.31±0.85)g和L(8.80±1.40)g光裸方格星虫耗氧率和排氨率的影响。结果显示,盐度对耗氧率和排氨率影响均显著,盐度和规格的交互作用对耗氧率和排氨率影响极显著。盐度在15~25时,耗氧率(OR)和排氨率(AR)均随着盐度的增加而升高,盐度为25时达峰值,之后随着盐度的增加而降低。耗氧率和排氨率与盐度呈一元二次函数关系,OR和AR与盐度的关系可表示为y=–ax2+bx–c。对于耗氧率,a值的范围是0.030~0.044,b值的范围为1.525~2.252,c值的范围为11.824~20.132;对于排氨率,a值的范围是0.009~0.012,b值的范围为0.455~0.593,c值的范围为4.369~5.275。光裸方格星虫的O/N值范围为4.06~14.28。研究表明,光裸方格星虫代谢的最适盐度为25,且对盐度变化的适应能力较强,可通过调整生理代谢水平来适应低盐或高盐环境。     

Comparison of the florfenicol metabolic rate in Portunus trituberculatus individuals with different body weights

We analysed the metabolic rate of large individuals (LIs) and small individuals (SIs) (based on body weight) of 80‐day‐old specimens of Portunus trituberculatus injected with 40 mg/kg florfenicol (FLR). The results showed that FLR contents in the gills and hepatopancreas were higher in the SIs than in the LIs. The activities of erythromycin N‐demethylase and 7‐ethoxyresorufin‐O‐deethylase related to cytochrome oxidase P450 (CYP) were induced after FLR injection and showed a size‐dependent pattern; however, no significant difference in aminopyrine N‐demethylase activity was found between the LIs and SIs. The activity of the phase II enzyme glutathione S‐transferase (GST) increased in the hepatopancreas after FLR injection, and it was higher in the SIs than the LIs. Moreover, induction of CYP2, CYP3, GST, ABCB and ABCG was observed in the first 24 hr after FLR injection. FLR caused more biomolecular damage in the SIs than the LIs, displaying an obvious body weight‐ and time‐dependent pattern. In summary, the SIs exhibited faster FLR uptake and slower depuration in this species, and FLR caused more biomolecular damage to the SIs.     

Effect of esterification on the absorption of astaxanthin in rainbow trout, Oncorhynchus mykiss (Walbaum)

Gastrointestinal and serum absorption of astaxanthin was studied in rainbow trout, Oncorhynchus mykiss (Walbaum) (217 ± 2 g) fed diets supplemented with either esterified astaxanthin (from Haematococcus pluvialis) or free astaxanthin (synthetic, as 8% w/w beadlets) at similar levels (50 mg kg^?1). After 56 days of feeding, there was a significant difference (P = 0.0582) between steady‐state serum astaxanthin concentrations for fish fed free (2.0 ± 0.3 μg mL^?1) or esterified astaxanthin (1.3 ± 0.1 μg mL^?1) at the 90% confidence level. However, following ingestion of a single meal supplemented with free or esterified astaxanthin, the rates of astaxanthin absorption into serum were not significantly different (P > 0.1) (0.8 ± 0.2 µg mL^?1 h^?1 and 1.0 ± 0.4 µg mL^?1 h^?1 respectively). In fish fed both free or esterified astaxanthin, higher absorption (P < 0.05) of astaxanthin by the ileal (0.8 ± 0.14 μg g^?1 and 0.9 ± 0.15 μg g^?1 respectively) compared with the posterior (0.2 ± 0.01 μg g^?1 and 0.3 ± 0.14 μg g^?1 respectively) intestine was recorded. This confirmed the role of the anterior intestine in carotenoid absorption. Non‐detectable levels of esters in digesta taken from the hind intestine suggest the anterior intestine is also the primary region for ester hydrolysis.