Effects of seedling age on the growth stage and yield formation of hydroponically grown long-mat rice seedlings

Understanding the characteristics of rice productivity is of great importance for achieving high yield formation.However,such traits have not yet been studied for different ages of hydroponically grown long-mat rice seedlings(HLMS),which constitutes a new method of seedling cultivation.Field experiments were conducted to evaluate the effects of seedling age on the growth stage,photosynthesis characteristics,dry matter production,and yield of HLMS.A conventional japonica rice cultivar(Wuyunjing 24)and an indica hybrid rice cultivar(6 Liangyou 9368)were used as test materials.The results showed that the whole phase was shortened by 13-15 days for young seedlings(13-day-old)compared with old seedlings(27-day-old),which occurred because the growth process accelerated with the transplantation of young seedlings.As seedling age increased,the dry matter weight of stems of individual plants and of the population increased at the transplanting stage but decreased at the maturity stage(MS).Compared with that of 27-day-old seedlings,the average ratio of panicle weight to total plant dry weight of 13-day-old seedlings during a 2-year period increased by 3.71%for Wuyunjing 24 and by 3.78%for 6 Liangyou 9368 at the MS.Moreover,as seedling age increased,the leaf area index and photosynthetic potential decreased for both cultivars,and the photosynthetic rate markedly decreased at the heading stage(HS).With the exception of that of Wuyunjing 24 from the jointing stage to the HS in 2014,the crop growth rate was higher for young seedlings than for old seedlings.Grain yield significantly decreased with seedling age,but no significant difference was detected between the 13-and 20-day-old seedlings for either cultivar.Therefore,equilibrious and high biological yield formation,vigorous growth in the late stages,and high photosynthetic production capacity are important characteristics and causes of the efficient and sustainable output of photosynthetic systems and for achieving high yield formation in young transplanted seedlings(13-20-day-old).

Growth Characteristics and Resource Evaluation of Sebastes schlegelii in Zhangzidao Artificial Reef Area

[Objective]The paper was to formulate catchable size and total allowable catch of Sebastes schlegelii in Zhangzidao artificial reef area.[Method]Based on analysis of length-weight formula,body length and weight growth equations,and instantaneous mortality rate,the inflection age and critical age of weight growth were calculated,and the biomass of S.schlegelii in Zhangzidao artificial reef area was estimated.[Result]The growth equation of body length was Lt=412.5×[1-e^-0.21（t＋0.65）]and the growth equation of body weight was Wt=1 734.2×[1-e^-0.21（t＋0.65）]^2.92.The inflection age and critical age for weight growth of S.schlegelii were 4.45 and 4.82 a,respectively.The biomass in Zhangzidao artificial reef area was about 456.8 t.[Conclusion]For S.schlegelii flock in Zhangzidao artificial reef area,the catchable length was about 271.2-281.7 mm,the catchable weight as about 509.4-569.5 g,and the total allowable catch was about 60.43 t.

Climate-induced life cycle and growth variations of neon flying squid(Ommastrephes bartramii)in the North Pacific Ocean

Climate change has had large impacts on marine animals,including neon flying squid Ommastrephes bartramii(O.bartramii)in the North Pacific Ocean.O.bartramii statoliths from 2012,2015,and 2016 were used to evaluate the variations in life cycle events.The relationship between mantle length and body weight showed significant differences between years and gender.The oldest squid was collected in 2016 at 271 days old,further proving that O.bartramii has nearly a 1-year life span.The hatching season ranged from December to May and the peak hatching time in 2015 was one-half month later than in 2012 and 2016.Growth rates varied with environmental factors such as sea surface temperature(SST)and chlorophyll a concentration(chl.a),indicating that higher SST and chl.a concentrations led to faster growth.An extreme El Ni˜no event with lower SST in 2015 also led to younger age class and slower growth rates.The occurrence of differences in body size and growth rates between years,caused by the interannual variations of environmental factors,makes it necessary to use separate growth curves for different years when analyzing North Pacific O.Bartramii populations.

Characteristics of Dried Soil Layers Under Apple Orchards of Different Ages and Their Applications in Soil Water Managements on the Loess Plateau of China

Negative soil water balance （i.e., water input 〈 water output） can lead to soil desiccation and subsequently the occurrence of a dried soil layer （DSL）. The DSLs are generally studied at a specific sampling depth （e.g., 500 cm）, and the actual extent of DSLs remains unknown due to the challenge of collecting deep soil samples. To investigate the characteristics of actual DSLs under different ages of apple orchards and ascertain the optimal age of apple orchards for avoiding/controlling the formation of DSLs, soil samples were collected to a depth of 1800 cm under apple orchards of different ages in Changwu on the Loess Plateau of China. As the ages increased, soil water content （SWC） and mean SWC in DSLs showed an overall decreasing trend, whereas while DSL thickness and the quantity of water deficit （QWD） in DSLs demonstrated an increasing trend. The DSL was the thickest （1 600 cm） under the 17-yeax-old orchard, the forming velocity of DSL thickness was the highest at the apple tree growth stage of 9-17 years （168 cm year-l）, and the highest increasing velocity of QWD （-181 mm year-1） was also observed at this stage. The thickness of DSL was significantly correlated with growth age and root depth of apple trees （r 〉 0.88）, whereas the QWD and mean SWC in DSLs were found to have no correlation with them. The optimal age of apple orchards for avoiding/controlling the formation of DSLs was about 9 years. This information provided pertinent references for the management of deep water resources by controlling the growth age of plants. Key Words： deep soil, growth age, plant roots, soil desiccation, soil water content, soil-plant water relation.

Age,growth and length-weight relationship of the white skate,Rostroraja alba(Linnaeus,1758)(Chondrichthyans:Rajidae),from the Gulf of Gabes(Tunisia,Central Mediterranean)

Objective:To investigate the length distribution,sex ratio,length-weight relationship,age and growth of Rostroraja alba in the Gulf of Gabes.Methods:This study estimated age and growth of the white skate,Rostroraja alba by counting vertebral band pairs from 112 specimens taken by commercial fisheries during 2006-2009 from the Gulf of Gabes(Southern Tunisia,Central Mediterranean Sea).Results:This is the first and only known information in regards to the age and growth of this species in Tunisia.Vertebra diameter was strongly correlated with total length and age,which were expressed by linear or cubic regression equations.The oldest female in this study was 35 years and 160 cm,whereas the oldest male was 32 years and 150 cm.The von Bertalanffy growth parameters were TL_(∞)=(202.26±3.40)cm,K=(0.040±0.038)/year and t_(0)=(1.84±0.01)10^(-1)/year for females and TL_(∞)=(198.60±3.61)cm,K=(0.060±0.076)/year and t_(0)=(1.28±0.04)/year for males.Conclusions:This study would be an effective tool for fishery biologists,managers and conservationists to initiate management strategies and regulations for the sustainable conservation of the remaining stocks of this species in the Gulf of Gabes(Southern Tunisia)ecosystem.

Age,growth and length-weight relationship of the rough skate,Raja radula(Linnaeus,1758)(Chondrichthyans:Rajidae),from the Gulf of Gabes(Tunisia,Central Mediterranean)

Objective:To investigate the length distribution,sex ratio,length-weight relationship,age and growth of Raja radula in the Gulf of Gabes.Methods:The age and growth characteristic of the rough skate(Raja radula)inhabiting in the Gulf of Gabes(Central Mediterranean Sea)was determined.A total of 1250 specimens were sampled.According to the marginal increment band its growth was annual.Results:The growth parameters were derived by using the von-Bertalanffy method and were separately evaluated as follows:TL∞=97.2 cm,K=0.15 y^(-1),t_(o)=0.35,and W_(∞)=5.28 kg,and TL∞=76.4 cm,K=0.22 y^(-1),to=0.16,and W∞=3.77 kg,for females and males respetively.The maximum age was 12 years for females and 10 years for males.Conclusions:Results from this research will provide a starting point to develop a management plan for the rough skate in the Gulf of Gabes.Further investigations are necessary to quantify the impact of the existing regulations on the population dynamics and recruitment patterns of this species in the region.

Fisheries management of round sardinella Sardinella aurita along North Sinai coast

Objective:To estimate the biological and population parameters required for proposing a preparation to sustain and manage this valuable fish resource.Methods:Aging was done by scales reading,and growth was estimated by using the back-calculation method.The values of growth parameters L_(∞),k and t_(o)were calculated by von Bertalanffy model.Results:The results of growth parameters L_(∞),k and t_(o)were 28.36 cm,0.184 per year and-0.8437 per year,respectively.Mortality coefficient,survival and exploitation rates estimated to perceive yield per recruit and biomass per recruit.Conclusions:Biological reference points and virtual population analysis were prepared to plan appropriate managements forSardinella aurita fisheries.