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101.
Xiaowu LI Zhongjie LI Jiashou LIU Tanglin Zhang Chaowen Zhang 《Aquaculture International》2011,19(2):301-311
A 74-day growth trial was carried out to investigate the effects of light intensity on the juvenile Chinese mitten crab, Eriocheir sinensis, under semi-natural conditions. The experiment had three light intensity treatment groups, natural light (NL), middle light
(ML), and low light (LL), as light intensity became weaker. The results indicated that light intensity had no significant
effect on molting interval and molting frequency but did have a significant effect on the molting weight gain of the crab.
Molting weight gain in group NL was significantly higher than that in group LL (P < 0.05). Specific growth rate in weight (SGRw) and in carapace width (SGRcw), weight gain, and final body weight were significantly
affected by light intensity (P < 0.05). No significant difference was detected in survival between groups (P > 0.05). The precocious rate in groups NL, ML, and LL was 26.14, 15.48, and 17.14%, respectively. The precocious rate in
group NL was significantly higher than that in groups ML and LL (P < 0.05). Chemical composition of the crab body was significantly affected by light intensity, but the activity of alkaline
phosphatase, trypsin, and pancreatic lipase was not significantly affected by light intensity. The results indicated that
the submitted light intensity was useful in reducing the precocious rate without affecting the normal growth of juvenile E. sinensis. 相似文献
102.
Shiro Itoi Noriyuki Takai Satomi Naya Keitaro Dairiki Akira Yamada Seiji Akimoto Kiyoshi Yoshihara Haruo Sugita 《Fisheries Science》2008,74(3):503-510
ABSTRACT: Gnomefish Scombrops boops and Scombrops gilberti are commercially important fishes in Japan, but these species are often confused in the markets because of their morphological similarity. To identify these two species, we performed nucleotide sequencing and restriction fragment length polymorphism (RFLP) analysis on 16S ribosomal RNA (rRNA) gene and the control region in mitochondrial DNA. Five and 12 nucleotide substitutions were observed between species in the 777-bp 16S rRNA gene and 471-bp control region, respectively. Diagnostic restriction sites for discriminating between S. boops and S. gilberti were found in the 16S rRNA gene, but not in the control region. Polymerase chain reaction (PCR)–RFLP analysis using two enzymes, Eco NI and Mva I, clearly discriminated between S. boops and S. gilberti identified by meristic characters. The PCR–RFLP analysis identified most of the 168 Scombrops young caught in the coastal waters of the Izu and Miura peninsulas as S. boops , suggesting that S. gilberti juveniles are rare in this area. 相似文献
103.
Anne H. Beaudreau Eric J. Ward Richard E. Brenner Andrew O. Shelton Jordan T. Watson Jennifer C. Womack Sean C. Anderson Alan C. Haynie Kristin N. Marshall Benjamin C. Williams 《Fish and Fisheries》2019,20(4):601-619
Heterogeneity in human responses and decision‐making can contribute to the resilience of social–ecological systems in the face of environmental, political and economic pressures. In fishery systems worldwide, the ability of harvesters to maintain a diverse portfolio of fishing strategies is important for building adaptive capacity. We used a case‐study approach to examine the complexity of factors that inhibit or promote diversification in fisheries of Alaska, one of the major fishing regions of the world. Through a combination of harvest records and literature review, we explored shifts in participation and portfolio diversity in Alaskan fisheries over three decades. The four case‐studies examined the responses of fishers, fleets and communities to multiple, intersecting pressures, including biological declines, market and price dynamics, fishery privatization and the 1989 Exxon Valdez oil spill. These cases illustrate how stressors acting at multiple scales can encourage or constrain opportunities for diversification, and that these opportunities may be spread inequitably across participants. Overall, we found evidence for reduced participation and increasing specialization in Alaskan commercial fisheries. While numerous factors explain these trends, policies like individual quota systems and the increasing cost of entry into fisheries are forcing consolidation at local to regional scales. A portfolio approach to managing fisheries that reduces barriers to diversification and includes broad representation of resource users and communities in management may help to maintain opportunity and choice for fishers. 相似文献
104.
Monosex male culture of C. quadricarinatus is proposed for increasing yields because males reach a larger size at harvest than females. An experiment was done to evaluate
the effects of androgenic gland extract and temperature on sex reversal and somatic growth in early juvenile females. Females
were exposed to the following experimental conditions: C: control food and temperature maintained at 26 ± 1°C; HT (high temperature):
control food and temperature maintained at 28.5 ± 1°C; VHT (very high temperature): control food and temperature maintained
at 31 ± 1°C; AG: food with enriched with androgenic gland (1/10 dose for each juvenile per day) and temperature maintained
at (26 ± 1)°C. The juveniles were weighed, sexed, and growth increment (GI) and growth rate (GR) were calculated twice a month.
The HT and AG groups differed from the C group in GI and GR indicating a greater somatic growth. At the end of the experiment,
the HT and AG groups had similar weight but only the HT group had enhanced oocyte diameter, with some vitellogenic oocytes
compared to the C group. In the HT group, there was significant sex reversal, as indicated by development of male and intersex
male characteristics in different individuals. Both temperature and AG diet have a high potential for culture of this species
because of their enhancement of somatic growth; higher temperature increases the proportion of males, a desirable characteristic
of cultured populations. 相似文献
105.
The ontogenetic development of the digestive enzymes amylase, lipase, trypsin, and alkaline phosphatase and the effect of
starvation in miiuy croaker Miichthys miiuy larvae were studied. The activities of these enzymes were detected prior to exogenous feeding, but their developmental patterns
differed remarkably. Trypsin activity continuously increased from 2 days after hatching (dah), peaked on 20 dah, and decreased
to 25 dah at weaning. Alkaline phosphatase activity oscillated at low levels within a small range after the first feeding
on 3 dah. In contrast, amylase and lipase activities followed the general developmental pattern that has been characterized
in fish larvae, with a succession of increases or decreases. Amylase, lipase, and trypsin activities generally started to
increase or decrease at transitions from endogenous to exogenous feeding or diet changes, suggesting that these enzymatic
activities can be modulated by feeding modes. The activities of all the enzymes remained stable from 25 dah onwards, coinciding
with the formation of gastric glands and pyloric caecum. These results imply that specific activities of these enzymes underwent
changes due to morphological and physiological modifications or diet shift during larval development but that they became
stable after the development of the digestive organs and associated glands was fully completed and the organs/glands functioned.
Trypsin and alkaline phosphatase were more sensitive to starvation than amylase and lipase because delayed feeding up to 2 days
after mouth opening was able to adversely affect their activities. Enzyme activities did not significantly differ among feeding
groups during endogenous feeding; however, all activities were remarkably reduced when delayed feeding was within 3 days
after mouth opening. Initiation of larvae feeding should occur within 2 days after mouth opening so that good growth and survival
can be obtained in the culture. 相似文献
106.
107.
Sung-Yong Oh Choong Hwan Noh Rae-Seon Kang Chong-Kwan Kim Sung Hwoan Cho Jae-Yoon Jo 《Fisheries Science》2008,74(4):846-852
ABSTRACT: Compensatory growth, feeding rate, feed efficiency and chemical composition of juvenile black rockfish (mean weight 1.43 g) were investigated for 35 days after a 14-day feed deprivation treatment under four feeding conditions: one group continuously fed (control) and the other three groups fasted for 5 days (F5), 10 days (F10) and 14 days (F14). All fasted fish were re-fed from day 15. Only F5 achieved the same body weight as the control, indicating that complete compensation occurred in F5. The specific growth rate (SGR) of F5 was the highest at day 21 and then decreased thereafter, showing higher values than the control at days 21, 28 and 42. In contrast, although SGRs of F10 and F14 were higher than that of the control during the whole refeeding period except day 21, they did not catch up the control in body mass, indicating that only partial compensation occurred in F10 and F14. The feeding rate (FR) of all groups except F14 changed in a pattern similar to SGR (Spearman's rank correlation, r s > 0.9), suggesting that SGR varied depending on FR. Similar feeding efficiencies (FEs) were found in the four groups and they did not vary significantly during the whole refeeding period, suggesting that FE was not the factor affecting SGR. At day 14, the ratios of lipid to lean body mass in F10 and F14 were lower than those in the control and F5, and there was no difference between the control and F5. At day 49, however, only F14 showed a lower value than the other three groups, and there was no difference among the three groups. These results indicate that juvenile black rockfish fasted for 5–14 days can exhibit compensatory growth after refeeding, but timing and degree vary depending on the duration of feed deprivation. 相似文献
108.
Nancy P. Chaves Luis E. Pocasangre Fritz Elango Franklin E. Rosales Richard Sikora 《Scientia Horticulturae》2009,122(3):472-478
Eight endophytic fungal and bacterial isolates with antagonistic activity against Radopholus similis were evaluated in vivo for their individual and combined effects on biocontrol of R. similis and on the growth of “Grand Naine” cultivar banana plantlets in the greenhouse. Penetration efficiency (PE) of R. similis was between 3 and 21% in 29 biological agents (BAs) treatments, less than the 29% of the nematode-alone control (p ≤ 0.0001); 24 of the BAs treatments did not differ from the PE of 5% for a nematicide control. Twenty nine BAs treatments exhibited antagonistic activity against nematodes which reduced final population levels between 18 and 93%, relative to those on nematode-alone control plants (p ≤ 0.0001), and 14 BAs treatments were statistically similar to the nematicide treatment (88% reduction). Twenty four BAs treatments had increments of plant root biomass ranging from 20 to 58%, greater than the control plants; 37% of the treatments with single and combined BAs inoculations had root length increments ranging from 29 to 54% compared with control and chemical treatment. The nematicide, Terbufos 10GR, did not affect plant growth. 相似文献
109.
Paul C. Stoy Mathew Williams Mathias Disney Ana Prieto-Blanco Brian Huntley Robert Baxter Philip Lewis 《Landscape Ecology》2009,24(7):971-986
Transferring ecological information across scale often involves spatial aggregation, which alters information content and
may bias estimates if the scaling process is nonlinear. Here, a potential solution, the preservation of the information content
of fine-scale measurements, is highlighted using modeled net ecosystem exchange (NEE) of an Arctic tundra landscape as an
example. The variance of aggregated normalized difference vegetation index (NDVI), measured from an airborne platform, decreased
linearly with log(scale), resulting in a linear relationship between log(scale) and the scale-wise modeled NEE estimate. Preserving
three units of information, the mean, variance and skewness of fine-scale NDVI observations, resulted in upscaled NEE estimates
that deviated less than 4% from the fine-scale estimate. Preserving only the mean and variance resulted in nearly 23% NEE
bias, and preserving only the mean resulted in larger error and a change in sign from CO2 sink to source. Compressing NDVI maps by 70–75% using wavelet thresholding with the Haar and Coiflet basis functions resulted
in 13% NEE bias across the study domain. Applying unique scale-dependent transfer functions between NDVI and leaf area index
(LAI) decreased, but did not remove, bias in modeled flux in a smaller expanse using handheld NDVI observations. Quantifying
the parameters of statistical distributions to preserve ecological information reduces bias when upscaling and makes possible
spatial data assimilation to further reduce errors in estimates of ecological processes across scale. 相似文献
110.