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21.
Insulin-like growth factor 1 (IGF1) plays an important role in fish growth. This study investigated the IGF1 response to various nutritional conditions in yellowtail. First, we cloned 1,075 bp of yellowtail IGF1 cDNA, which codes for a protein of 185 amino acids (aa). This is composed of 44 aa for the signal peptide; 68 aa for the mature peptide comprising the B, C, A, and D domains; and 73 aa for the E domain. The mature yellowtail IGF1 showed high identity to IGF1 of other teleosts. Insulin-like growth factor 1 mRNA expression in the liver and white muscle was measured to observe the IGF1 response to various nutritional conditions, because the liver has the highest IGF1 expression and white muscle comprises the largest fraction of the fish body. Only white muscle IGF1 mRNA expression decreased significantly by 3 wk of fasting and recovered by refeeding. In subsequent feeding ratio (1%, 2%, and 3%/BW/d) experiments, significant correlations to growth were observed in white muscle IGF1 mRNA expression at 2- and 6-wk points and in hepatic IGF1 mRNA expression at 4 wk point. These data suggest that IGF1 expression both in hepatic and white muscle is important for somatic growth in yellowtail. Furthermore, white muscle IGF1 mRNA expression showed better responses to somatic growth and nutrition status in our two experiments than hepatic IGF1 mRNA expression.  相似文献   
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Feeding trials were carried out to examine substances that could be used as supplements in low‐protein/high‐lipid diets to improve protein digestion of yellowtails (Seriola quinqueradiata) during winter. Dietary supplementation with synthetic or natural (krill and squid extracts) feeding stimulants (FS) improved feed intake and growth performance of yellowtails. Moreover, the apparent protein digestibility (APD) and pepsin, trypsin and chymotrypsin secretions in fish fed diets supplemented with the different FS were superior to those in fish fed the control diet. These findings suggest that the dietary inclusion of either synthetic or natural FS is a potential tool for improving protein digestion at low water temperatures, and may provide a promising solution for the winter growth retardation experienced in yellowtail culture.  相似文献   
24.
The effects of temperature and salinity on the embryonation period and hatching success of eggs of Benedenia seriolae were investigated. Temperature strongly influenced embryonation period; eggs first hatched 5 days after laying at 28 degrees C and 16 days after laying at 14 degrees C. The relationship between temperature and embryonation period is described by quadratic regression equations for time to first and last hatching. Hatching success was >70% for B. seriolae eggs incubated at temperatures from 14 to 28 degrees C. However, no B. seriolae eggs embryonated and hatched at 30 degrees C and <2% of eggs hatched when incubated at 24 degrees C after transfer to 30 degrees C for 48 h. Embryonation period was similar for eggs incubated in sea water at 25, 30 and 35 per thousand salinity, but increased for eggs incubated at higher or lower salinities. When incubated at salinities ranging from 25 to 45 per thousand, more than 70% of B. seriolae eggs embryonated and hatched. Hatching success was lower at 20 and 50 per thousand salinity and few or no eggs hatched at 10 and 15 per thousand. Hatching of B. seriolae eggs can be prevented by desiccation for 3 min, by immersion in water at 50 degrees C for 30 s or by treatment with 25% ethanol for 3 min.  相似文献   
25.
ABSTRACT:   Artificially hatched Seriola species have the problem of malformation, mainly in their vertebrae, head, and mouth parts. To clarify the cause of vertebral malformation, the effects of hypoxia during embryogenesis on the induction of centrum defects was investigated in artificially hatched amberjack Seriola dumerili . Firstly, 7-somite stage embryos were exposed to waters of 0, 12.5, 25, 50, and 100% dissolved oxygen (DO) for 0.5, 1, 2, 3, 4, and 5 h to confirm the effective dose (DO concentration and duration of exposure) of hypoxia that induces somitic disturbances in newly hatched larvae. Exposure of embryos to 12.5% DO concentration for longer than 0.5 h induced somitic disturbances. Following this result, centrum defects in juveniles were investigated by an induction experiment with embryos exposed to 12.5% DO for 2 h at the gastrula, 1- or 2-somite, 10-somite, 15-somite, or heart beating stage. This experiment revealed that centrum defects were induced only during somitogenesis, and somitic disturbances were the premonitory symptom of centrum defects. These results indicate hypoxia during somitogenesis as a possible cause of centrum defects in amberjack.  相似文献   
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A Lancefield serological group C Streptococcus sp. was isolated from cultured amberjack, Seriola dumerili Risso, and yellowtail, Seriola quinqueradiata Temminck and Schlegel, immunized with Lactococcus garvieae commercial vaccines in Japan. The isolated bacteria were Gram-positive cocci, auto-aggregating in saline, morphologically long chains in growth medium, catalase negative and alpha-haemolytic on blood agar. An almost complete gene sequence of the 16S rDNA of two isolates was determined and compared with that of bacterial strains in the database. The isolates were identified as Streptococcus dysgalactiae based on the results of the 16S rDNA sequence, the bacteriological properties and the Lancefield serological grouping. Oligonucleotide primers specifically designed for the 16S-23S rDNA intergenic spacer region of S. dysgalactiae amplified a gene from all the fish isolates, as well as the type strains alpha-haemolytic S. dysgalactiae subsp. dysgalactiae ATCC430738 and beta-haemolytic S. dysgalactiae subsp. equisimilis ATCC35666, but not those of S. equi ATCC33398, Lactococcus garvieae ATCC43921 and L. garvieae KG9408. The severe necrotic lesions of the caudal peduncle seen in experimentally infected fish were similar to those seen in naturally infected fish.  相似文献   
28.
The self-feeding pattern of yellowtail, Seriola quinqueradiata, maintained in floating net cages was examined throughout a year, and the influence of seasonal changes of the photoperiod and water temperature on the feeding pattern was investigated. Two groups of 50 yellowtail (initial mean body weight about 50 and 80 g, respectively) were kept in two experimental net cages (2×3×4 m deep), with a self-feeding device installed on each. It was possible to maintain yellowtail in net cages using a self-feeder throughout almost a year. The number of daily food demands was greatly affected by the seasonal changes in water temperature. Yellowtail showed high self-feeding activity, above 18 °C; depressing water temperatures did not influence the activity when the water temperature was over 18 °C. However, the activity decreased when the water temperature fell below 18 °C. The feeding pattern in a 24-h period was greatly affected by the temporal changes in light intensity. Annual observations revealed that yellowtail showed generally crepuscular plus nocturnal feeding behavior and had two peaks of feeding activity a day. These peaks appeared at dawn and dusk; moreover, a clear association between the most active time of self-feeding and the period of the greatest change in light intensity was observed. The results suggest that a change in light intensity might stimulate the appetite of yellowtail or that there is a light level at which yellowtail prefer to eat.  相似文献   
29.
SUMMARY: An inhibitory effect of Kunitz and Bowman-Birk soybean trypsin inhibitors (K- and BB-SBTI) was investigated on tryptic and chymotryptic proteinases of a brood of tiger puffer Takifugu rubripes and yellowtail Seriola quinqueradiata . These assist to comprehend the differences in dietary soybean meal (SBM) utility by fish species and to develop low cost SBM diets with low contents of fish meal. The K-SBTI strongly inhibited tryptic proteinase and weakly inhibited chymotryptic proteinase from the hepatopancreas and intestine including pyloric ceca of the fishes. The BB-SBTI strongly inhibited both proteinases of the fishes. The K-SBTI inhibition for tryptic protease and the BB-SBTI inhibition for tryptic and chymotryptic proteases were relatively constant in tiger puffer with growth of 12–199 g bodyweight. In yellowtail with growth of 7–672 g bodyweight, the K-SBTI inhibition for tryptic protease and the BB-SBTI inhibition for chymotryptic protease were also relatively constant. The BB-SBTI inhibition for yellowtail tryptic protease typically fell in the stage from 7 g to 57 g bodyweight, and then decreased slightly or was maintained constantly. These results indicate that there are different inhibitory modes of K- and BB-SBTI and there is inter- and intraspecific diversity of tryptic protease conformation between the two species.  相似文献   
30.
A captive population of California yellowtail (Seriola lalandi) was used to document spawning patterns, including measures of egg production, population fecundity and egg and larval quality from 2007 to 2010. Spawned eggs were also used to document larval development and to develop rearing techniques for aquaculture in the region. Broodstock growth and condition factor were best when feeding rations were maintained at 10–15% body weight week?1 during the warm summer months. A winter ration based on satiation feeding was typically 4% body weight week?1. During the 4‐year study period, the only broodstock health issue was an infestation by the parasitic gill fluke Zeuxapta seriolae, which was readily treated. Spawning occurred naturally in the 140 m3 tank when the ambient water temperature reached 16°C and ended when the temperature exceeded 22°C. Egg production reached a maximum in 2010 when 43 spawn events were recorded from a pool of nine females yielding 36.8 million eggs in total. The average female size at this time was 20 kg, which equated to a total annual population fecundity of approximately 226 000 eggs kg?1 female year?1. Larval rearing trials yielded survival rates as high as 5.8% from egg to 50 days post‐hatch (dph). Successful larval culture methods included the addition of algae paste for green water culture, rotifers (20 rotifers mL?1) at 2 dph and Artemia (5 Artemia mL?1) at 6 dph. Larvae were transferred from the incubation tank at 10 dph to a shallower tank with 33% greater surface area to accommodate the larvae's strong orientation to surface waters. This research represents the first documentation of successful spawning and larval rearing for S. lalandi in the eastern Pacific.  相似文献   
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