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Samples of halibut eggs in nature have led to theories that development occurs near the sea bed and, alternatively, well up in the water column. Resolution of the conflicting theories and information which should assist culturists in providing the proper environmental conditions for egg development and hatching were the subjects of this study. The neutral buoyancy salinity (NBS) of Pacific halibut eggs and larvae ranged between 29.8–34%. Eggs and larvae with higher NBS (> 35%) were usually abnormal or stressed. Thus, eggs found near the seabed may be nonviable.  相似文献   
2.
We examined trends in the growth regulatory hormones growth hormone (GH) and insulin-like growth factor-I (IGF-I) from August to December in chinook salmon. Fish on 100% (ad libitum) and 64% rations of a low fat high protein diet, and a 64% ration of commercial feed (BioOregon-grower) were sampled twice a month. Fish were kept on simulated natural photoperiod at constant temperature. GH declined in late August and early September, consistent with photoperiodic regulation. No effects of ration or diet composition on GH were found. IGF-I increased to a peak on 4 October 1998 and declined thereafter. High dietary ration and the higher fat commercial diet increased IGF-I. Fish length and IGF-I level were positively correlated. This study shows that a peak in IGF-I may occur in the fall in chinook salmon. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
3.
Blood samples were collected from captive Pacific halibut, Hippoglossus stenolepis , at intervals of about six weeks from early December 1986 to late November 1987. Concentrations of plasma androgen and estradiol-17β were determined by radioimmunoassay. The plasma concentrations of steroid were highest during autumn and winter in halibut that matured during late winter. The concentrations of steroids in samples collected in December were above 2 ng/mL (estradiol) or 1 ng/mL (androgen) in maturing females and below 0.5 ng/mL for both steroids in non-maturing females. The levels of steroids decreased rapidly about one month before spawning. In a mature male, androgen began to rise in August and November, and reached a peak of 7 ng/mL in early December. One month before spawning, the androgen concentration fell to 0.16 ng/mL. Estradiol concentrations were detectable in the male and varied little during the year. In immature fish, neither androgen nor estradiol changed significantly throughout the year. These results suggest that the concentrations of estradiol or androgen measured in blood samples taken during December may be used to determine the sex and state of maturation of Pacific halibut.  相似文献   
4.
The present study was designed to obtain basic endocrine information on GTH I and GTH II in previtellogenic and prespermatogenic coho salmon (immature). Levels of GTH II in pituitary extracts were 6.5 ± 2.0 and 6.7 ± 2.0 pg/μg pituitary protein in male and female fish, respectively. In contrast, the pituitary content of GTH I was approximately 100-fold higher than GTH II (1.302 ± .22 and 1.173 ± .21 ng/μg pituitary protein in male and female fish, respectively). Plasma levels of GTH II in immature salmon were not detectable by RIA whereas plasma GTH I levels were approximately 0.62 ± 0.12 and 0.78 ± 0.13 ng/ml in male and female fish, respectively. Highly purified coho salmon GTH I and GTH II stimulated testicular testosterone production and ovarian estradiol productionin vitro in a similar manner, though GTH II appeared more potent than GTH I. Therefore, it appears that although the salmon pituitary contains predominantly GTH I prior to puberty, the gonad can respond to both GTH I and GTH II.  相似文献   
5.
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.  相似文献   
6.
Yearling coho salmon (Oncorhynchus kisutch) were fed diets containing triiodothyronine (T3; 4 or 12gmg), propylthiouracil (PTU; 1.5 or 6.0 mg/g), or both T3 (12g/g) and PTU (1.5 mg/g) from January 10 to May 29. Plasma T4 and T3, concentrations were maintained within normal physiological limits in all groups of treated fish. Increases in plasma thyroxine (T4) occurred in late April in groups receiving the high dose of T3 or PTU, or the combination of T3, and PTU. Peaks of plasma T4 occurred in May in the other groups. Thyroid follicle epithelial cell height was increased in the groups in the following order: highest; PTU (6.0 mg/g), PTU (1.5 mg/g), PTU + T3, control, T3 (4gmg/g), T3 (12g/g); lowest. In March specific binding of T3 by liver nuclei was not affected by treatment with T3 (12g/g) but was decreased 30% by treatment with PTU (6.0g/g). Body growth, food conversion efficiency, and pigmentary changes were increased by T3 (12g/g), decreased dose-dependently by PTU, and unaffected by the other dietary treatments. All treatments altered body proximate composition. Food consumption and the ability to osmoregulate in seawater were decreased in fish fed 6.0 mg/g PTU, but were unaffected by the other dietary treatments. These results suggest that during smoltification: 1) Thyroid hormones may be involved in control of thyroidal function and body growth and pigmentary changes, 2) Hypo-osmoregulatory competence is not further stimulated by exogenous T3 and 3) PTU does not block T4 synthesis but may block T3, action by interfering with nuclear T3 binding.  相似文献   
7.
Growth of Pacific halibut Hippoglossus stenolepis larvae was studied in the laboratory during 1989 and 1991. Larvae increased in length from 6.3 mm at hatching to 9.9 mm 20 d post-hatch. The average daily length increment was 0.17 mm. Dry weight of the larvae increased from an average of 210 μg at hatching to 570 μ g on day 20, providing a specific growth rate of 4.99. During the same period, mean yolk sac weight decreased from 1,390 μ g to 646 μ g, resulting in a yolk to body conversion efficiency of 48.5%. At hatching, the larval body made up only 13% of total dry weight. On day 20, the larval body made up 46.9% of the total weight. Larvae started feeding at a length of 12 mm after about 90% of their yolk sac had been absorbed.  相似文献   
8.
Eggs of Pacific halibut were incubated under various environmental conditions. Optimum hatching occurred over a temperature range from 6 C to 8 C, whereas temperatures of 3, 10, and 11 C were lethal. Development time from fertilization to 50% hatching varied from 250 h (9 C) to 320 h (6.5 C). Salinity effects on hatching were not as critical as temperature, as long as eggs were floating during the incubation period. Light intensity between 5 and 15 lux did not affect hatching success, but high light intensity (15 lux) and red and blue light (5 lux) produced high levels of larval abnormality. Simulated transport of unfertilized eggs indicated that the eggs can be safely moved and that fertilization rate is acceptable during the first 12 h after collection.  相似文献   
9.
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10.
The expression levels of growth hormone receptor (GHR) and insulin-like growth factor (IGF-I) in gonads of maturing coho salmon were measured by real-time PCR. The GHR and IGF-I mRNAs showed different gene expression pattern between male and female. These results suggest that a sexual dimorphism may exist in the GHR and IGF-I mRNA expressions of coho salmon during gonadal maturation  相似文献   
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