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1.
Monthly investigations were mae on the population of Chinese freshwater crab,Sinopotamon yangtsekiense Bott, 1967 from April, 1984 to March, 1985. The data on 4413 specimens show that the growth was affected mainly by temperature. During the April to November growth period, the crabs' major development occurred from June through October. One year was required for a fine white oocyte to develop into a mature egg. The reproduction period was June–October. Females bearing eggs were taken from June–August, and crabs with young were found from July–October. The females reproduced once a year but could for more than one year. The number of eggs carried by a female varied greatly according to the size of the crab, ranging from 30 to 100 eggs. New-born crabs become mature after 1–2 years. The sex ratio was approximately 1∶1 in the overall population. However, the larger crabs are predominantly male. The age distribution ofS. yangtsekinese was estimated from size frequency histograms. There were more adult crabs (over 70%) from June to October and more immature crabs (over 50%) from November to May.  相似文献   

2.
The reproductive biology of bream A bramis brama(L.) was studied from 546 fish collected from the lower reaches of the Irtysh River in Xinjiang, north-west China, from March to November 2013. The overall sex ratio(M/F) was 1.06:1, and was not significantly diff erent from the theoretical 1:1 ratio( P 0.5). However, there was a dominance of males during the pre-spawning season(1.33 in March and 1.56 in April, P 0.5), while females were dominant during the peak spawning season(0.88 in June, P 0.5). The monthly variation in gonadosomatic index(GSI) and proportion of gonads at each macroscopic maturity stage, indicated that A. brama spawned once a year with peak spawning occurring from late May to June. The unimodal distribution of oocyte diameter each month indicated that A. brama is a single spawner, with a high degree of spawning synchronicity. The standard lengths(SL 50) and ages( A 50) at first maturity for males and females, were 178 and 204 mm, and 5.6 and 6.8 years, respectively. The mean absolute fecundity(AF) was 77 311 eggs per fish, and mean relative fecundity(RF) was 162 eggs per gram of body weight(BW). The AF of A. brama increased linearly with increasing of gonad weight(GW), eviscerated weight(EW) and standard length(SL), but was not significantly correlated with age. As, A. brama in the lower reaches of the Irtysh River reaches reproductive maturity relatively late in their life span, is mature for a short period and spawns in aggregations, this fish is vulnerable to overexploitation.  相似文献   

3.
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4.
Based upon analysis of the seasonal fluctuation of GSI (gonado-somatic index), the spawning period of the hairtail extends from April to October. The maximum time difference between the early and the late brood individuals is about half a year. It is possible to distinguish the early brood and the late brood on the basis of the diameter of the first ring, setting 1.32 mm as a border line. Therefore, the identification of the first ring was solved in dispute.The maturation stages can be identified on the basis of the macroscopical and microscopical characteristics of the ovary; i.e., immature (II-A, B), maturing (III-C, D, E, IV-F), mature (IV-G, V-H, VI-I) and recovering (VII-J). Maturation is completed in the course of one year from different brood seasons. The smallest size at first maturity in female was about 170-180 mm in length and 80-100 grams in weight.There were two discrete groups in autumn which shown the same population unit in which those individuals may separate temporarily into different  相似文献   

5.
Samples were collected monthly from the sea area around Zhangzi Island,northern Yellow Sea,from July 2009 to June 2010.Vertical net towing was used to examine spatial and temporal variability in zooplankton abundance and biomass.Overall,C alanus sinicus and Saggita crassa were the dominant species found during the study period,while the amphipod T hemisto gracilipes was dominant in winter and spring.Vast numbers of the ctenophore species of the genus Beroe were found in October and November.It was not possible to count them,but they constituted a large portion of the total zooplankton biomass.Zooplankton species diversity was highest in October,and species evenness was highest in April.Zooplankton abundance(non-jellyfi sh)and biomass were highest in June and lowest in August,with annual averages of 131.3 ind./m3and 217.5 mg/m3,respectively.Water temperature may be responsible for the variations in zooplankton abundance and biomass.B eroe biomass was negatively correlated with other zooplankton abundance.Longterm investigations will be carried out to learn more about the infl uence of the environment on zooplankton assemblages.  相似文献   

6.
企鹅珍珠贝人工苗生长的初步观察   总被引：3，自引：0，他引：3  
为了解企鹅珍珠贝生长规律，观察了壳高2.5～5.0mm的出池幼苗，按月测量其生长参数和成活率，以及环境因子。结果表明，企鹅珍珠贝生长最快的月份为7～11月和次年4～6月，壳长，壳高和壳宽月均增加量分别为3.8～13.0mm、4.7～11.2mm、2.3～3.8mm，月成活率97.8%～98.6%。企鹅珍珠贝生长最慢月份是11月至次年3月。  相似文献   

7.
Black rockfish(Sebastes schlegeli) is an important species for culture; however, its reproductive characteristics have not been fully documented. In this study, we investigated the morphology and developmental process of germ cells in this ovoviviparous rockfish in reproductive season(October 2011–November 2012) with histological methods. We found that the gonad of mature fish showed notable seasonal changes in developmental characteristics and morphological structure. The sperm cells matured during a period lasting from October to December, significantly earlier than the oocytes did. A large number of spermatozoa and other cells occurred in testis at different developmental stages. Vitellogenesis in oocytes began in October, and gestation appeared in April next year. Spermatophores were discovered for the first time in Sebastes, which assembled in testis, main sperm duct, oviduct and genital tract, as well as ovarian cavity in October and April. These organs may serve either as production or hiding places for spermatophores and spermatozoa which were stored and transported in form of spermatophores. Testicular degeneration started from the distal part of testis in April, with spermatophores assembled in degenerating testis and waiting for transportation. The copulation probably lasted for a long period, during which the spermatozoa were discharged in batches as spermatophores. These spermatophores were coated with sticky materials secreted from the interstitial areas of testis and the main sperm duct, then transported into ovary.  相似文献   

8.
This study was to evaluate the effect of stocking densities on the nitrogen and phosphorus budgets for a polyculture of the crab Portunus trituberculatus and the Pacific white shrimp Litopenaeus vannamei.The shrimps(initial weight,0.012 g)were cultured at a density of 45 shrimp m-2,and juvenile crabs(initial weight,0.024 g)were cultured at five densities of 0,3,6,9,and 12 crabs m-2.The treatments were grouped as C0S45,C3S45,C6S45,C9S45,and C12S45,respectively.Water quality parameters,growth of shrimp and crabs,and nitrogen and phosphorus budget were measured.The results indicated that the shrimp performances in polyculture treatments C3S45 and C6S45 were superior to those in the crab-free treatment(C0S45).The crab in treatments C3S45 and C6S45 exhibited a significantly higher final mean weight and carapace width/length than those in treatments C9S45 and C12S45.The final size and survival of crabs had a negative correlation with the increasing crab stocking density.The contents of total phos-phorus and total nitrogen and the comprehensive contamination index values were higher in the C9S45 and C12S45 treatments than in the other treatments.The conversion ratios of nitrogen for crab and shrimp growth in treatment C3S45 were significantly higher than those in the crab-free treatment.These findings indicate that polyculturing shrimp with crabs at suitable densities can improve productivity,profitability,nutrient utilization,and the environmental quality.From the 60-day treatments,the optimal culture densi-ties were 3-6 crabs m-2 and 45 shrimps m-2.  相似文献   

9.
东海中南部海域锈斑蟳渔业生物学和数量分布   总被引：2，自引：0，他引：2  
研究了1998—1999年东海区虾蟹类调查所获的部分锈斑蟳样品与1998~2004年在东海拖虾作业与蟹笼作业等周年逐月渔获物中采集的锈斑蟳样品的生物学特性,结果表明:东海锈斑蟳渔获群体的甲长范围为26~105mm,甲宽范围为36~165 mm,体重范围为5~610 g,雄性个体平均要略大于雌性个体;周年雌蟹略多于雄蟹,性比为1∶0.94,繁殖期为7~12月,繁殖高峰期为8~10月,不同个体怀卵量在113 867~1 594 167粒之间;调查海区10月开始出现幼蟹,5月生长加速,最小抱卵个体的甲长为60 mm,甲宽为85 mm,体重为110 g。另根据1998~1999年调查资料分析得知:锈斑蟳主要分布在长江口渔场以南水深60 m以内海域,中心区分布在闽东渔场,渔期为11月~翌年2月,是舟山、长江口渔场三疣梭子蟹汛期结束后,蟹笼、流刺网作业的又一主捕对象。  相似文献   

10.
In this study,we investigated the community structure of crustaceans(decapod and stomatopod) inhabiting the sandy mud bottoms of Laizhou Bay(northeastern China) monthly from May 2011 to April 2012.Investigation was stopped from December 2011 to February 2012 because of the extreme weather and sea ice.A total of 205,057 specimens belonging to 31 species(shrimp,15;crab,15;and stomatopod,1) were collected in 148 hauls.From 2011 to 2012,Oratosquilla oratoria was the dominant biomass species(47.80%),followed by Charybdis japonica(15.49%),Alpheus japonicas(12.61%),Portunus trituberculatus(6.46%),and Crangon spp.(4.19%).Crangon spp.was the most dominant species by individual(32.55%).O.oratoria was the most-frequently encountered species(81.76%),followed by Palaemon gravieri(70.95%),C.japonica(65.54%),A.japonicas(62.16%),and P.trituberculatus(54.73%).The biomass density increased from August to September 2011 and decreased from March 2012 to April 2012.The dynamics of the ecological indices evolve in a similar manner,with high values of diversity and evenness and rich species from May to June 2011 and low values from September to October 2011.O.oratoria,C.japonica,and P.trituberculatus differed by biomass data between groups I(samples obtained from September to October 2011) and II(samples in other months).These species contributed more than 70% to the similarity of the crustacean community structure.Furthermore,the subsets of environmental variables that best matched the crustacean-assemblage structure were as follows:water depth(WD) in summer(June to August);sea surface temperature(SST),dissolved oxygen(DO),and WD in autumn(September to November);and DO,salinity,and WD in spring(March to May).The calculated correlation coefficients and significance level were higher in the period of July to August 2011 than in other months.Comparing 2011 to 2012 with 1982 to 1983,the species composition remained stable.However,the dominant species changed significantly.High value and large species,such as F.chinensis,P.trituberculatus,and T.curvirostris,have been replaced by low value and small species(i.e.,Crangon spp.,P.gravieri,and C.japonica).  相似文献   

11.
Mass occurrence of Salpa fusiformis was observed in the Southern Yellow Sea in May and June 2007. In order to investigate its population recruitment and environmental adaptation, temporal variation of abundance, diel vertical migration (DVM) and length frequency distribution of both aggregate and solitary forms were studied with samples collected from eight months during September 2006 to August 2007. S. fusiformis presented in six months other than September and October 2006, and average abundance of aggregate and solitary forms peaked in June and May, respectively. In December, aggregate forms were absent in the bottom layer and performed irregular DVM from surface to 50 m depth, while solitary forms was too scarce to perform diel vertical distribution analysis. Both aggregate and solitary forms presented reverse DVM in May and June. They migrated upwards during daytime and concentrated in surface layer at sunset. The bimodal distribution of aggregate forms was found in April and the average size was largest in this month. In other months, the smaller aggregate forms (1-5 mm) dominated in populations except for May, when the modal size ranged from 2 to 8 mm. The average size of solitary forms was largest in December, followed by April. The skewed nomal distribution of solitary forms was found in May and June, with the modal size of 2-7 mm and 5-13 mm, respectively.  相似文献   

12.
We collected Vimba vimba throughout the spawning season (mid April to mid June, 2007) in Gorgan Bay (south-western Iran) and investigated its age, growth, and reproductive traits. The maximum age was 5+ years. Both sexes grew allometrically (positive for males: b=3.140 9 and negative for females: b=2.791 4). The von Bertalanffy growth functions were described by the formulae L t =32.565(1-e−0.184(t+0.530)) for males and L t =35.950(1-e−0.179(t+0.529)) for females. The overall sex ratio was balanced, but males were predominant in the smaller size classes and females in the larger size classes. Based on the gonadosomatic index (GSI) values, spawning appears to occur between late April and late May in the bay. The highest mean GSI was 6.44 for males in early May and 20.36 for females in late April. Absolute fecundity varies from the minimum of 5 436 eggs for age 3+ fish to the maximum of 36 141 eggs for age 5+ fish. Fecundity was also positively correlated with fish size (length and weight). Egg diameter ranged from 1.05 to 1.70 mm in the mean of 1.42 mm. There was no correlation between female size and ova diameter.  相似文献   

13.
周年采集环沟格特蛤（Katelysiarimularis）分别测定生长指标（总重、软体部重、性腺重、肝重和软体部干重等）并用组织切片观察性腺发育的状况，以确定性腺发育的周期和时间。组织的光镜研究说明环沟格特蛤雌雄性腺发育均可分为增殖期、生长期、成熟期、排放期和休止期。在厦门吴冠镇环沟格特蛤1月开始其性腺发育,3月进入生长期，5～6月成熟，5～11月都有产卵，每年7月11月各有一次排卵高峰期。  相似文献   

14.
Horizontal starch gel electrophoresis was used to investigate the biochemical genetic structure of Chinese mittencrab Eriocheir sinensis and Hepu mitten crab E. hepuensis. Sixteen putative enzyme-coding loci were examined for forty-nineChinese mitten crabs and thirty-eight Hepu mitten crabs. Nine loci, AAT-1 *, AAT-2 *, G3PDH*, GPI*, IDHP-1 *, IDHP-2 *,MDH-1 *, MDH-2 * and PGM * , are polymorphic in Chinese mitten crab, and seven, AAT-1 *, AAT-2 *, GPI *, IDHP-1 *,MDH-1 *, MDH-2 * and PGM * , are polymorphic in Hepu mitten crab. The proportion of polymorphic loci and the expectedheterozygosity are 0.562 5 and 0.080 3 for Chinese mitten crab, and 0.437 5 and 0.075 4 for Hepu mitten crab. The Nei' s ge-netic distance between two species is 0.002 4.  相似文献   

15.
Pectenotoxins (PTXs) are a group of marine algal toxins. In this study, the accumulation and depuration of pectenotoxins in brown crab Cancer pagurus were investigated. Crabs were fed with toxic blue mussels Mytilus edulis for 21 days and then depurated for 42 days. Toxins were extracted with methanol from the digestive glands of contaminated crabs, uncontaminated crabs (control group) and from blue mussels for comparison. Extracts were analyzed by liquid chromatograph coupled with tandem mass spectrometry (LC-MS-MS). The concentrations of PTX-2, PTX-2 SA, 7-epi-PTX-2 SA, and PTX-12 were analyzed in two batches of toxic blue mussels and the crabs. A one-compartment model was applied to describe the depuration of PTXs. The half-life of PTXs was estimated to be 6-7.5 days. After depuration for 42 days, the amount of PTXs measured in the crab digestive glands was less than 1 μg/kg.  相似文献   

16.
1　Introduction　Thelifecycleofhorseshoecrabsislengthywhencom paredtoothermarinearthropodssuchasbluecrabsandshrimpspecies (Sekiguchietal.,1988) .Thetwospecies,TachypleustridentatusandCarcinoscorpiusrotundicauda,knowntooccurinHongKongrequire ,respectively ,betweenthirteentofourteenandtentoelevenyearstomaturebeforedepartingtheirnurserybeachesfordeeperwaters (ChiuandMorton ,1999a ;Sekiguchietal.,1988) .Thelivingenvironmentofthenurserybeacheswheretheeggsarelaidandincu bated ,andfromwhichtheyoun…  相似文献   

17.
Reservoir impoundment changes original fluvial habitats into lentic environments. Fish species adapted to lentic habitats may take the advantage of such habitat changes and show typical life history traits might facilitate the population increase. Siniperca kneri rarely occurred in fishery landing in the Three Gorges Reservoir(TGR) area before its impoundment in 2003, but it is now a dominant species. In this study, a total of 438 females of S. kneri were collected monthly during September 2012 through January2014 using gill nets in the TGR. The age, growth, and reproductive biology were then investigated, and compared with other S. kneri populations. The standard length at age 1 was 149.9 mm in the TGR, which is larger than the three compared populations(i.e., Sandaohe Reservoir, Xinfengjiang Reservoir, and North River), but smaller than one(the Guishi Reservoir). The youngest mature female in the TGR was age 1,which is younger than that of the two compared populations(i.e., Xinfengjiang Reservoir and the North River). The relative fecundity in the TGR was 140 eggs/g, which is higher than that of the only available compared population(Xinfengjiang Reservoir, 96 eggs/g). Our results demonstrated that S. kneri in the TGR tended to have faster growth in the first year, a younger age at first maturation, and higher reproductive ef fort.We suggest that such opportunistic-tended life history traits might facilitate rapid increase of the population.  相似文献   

18.
Accordion-shaped traps are widely used in China to catch the Asian paddle crab Charybdis japonica but traps of conventional design often catch juvenile crabs. A new type of accordion-shaped trap with an escape vent (L×W=4.3 cm×3.0 cm) was designed and a comparative study between the newly designed and conventional traps was performed in the artificial reef area of Zhuwang, Laizhou Bay, China from June to August 2012. The mean catch per unit effort (CPUE) of undersized crabs was significantly lower in the vented traps than in the conventional traps (paired t -test, n=30, P<0.001), while the CPUE of marketable crabs was significantly higher in the vented traps (paired t-test, n=30, P<0.001). The mean size of crabs (carapace length) caught in the vented traps was significantly larger than in conventional traps (paired t-test, n=29, P<0.001). The ratio of undersized crabs was 35.05±2.57% in conventional traps and 12.53±0.69% in vented traps (significantly lower, paired t-test, n=29, P<0.001). Therefore, a 4.3 cm×3.0 cm escape vent was considered appropriate for C. japonica fishing in the artificial reef area. This finding will assist the development of more sustainable and efficient crab fishing methods using accordion-shaped traps.  相似文献   

19.
From 8 April to 11 October in 2005, hydrological observation of the Rongbuk Glacier catchment was carried out in the Mt. Qomolangma (Everest) region in the central Himalayas, China. The results demonstrated that due to its large area with glacier lakes at the tongue of the Rongbuk Glacier, a large amount of stream flow was found at night, which indicates the strong storage characteristic of the Rongbuk Glacier catchment. There was a time lag ranging from 8 to 14 hours between daily discharge peaks and maximum melting (maximum temperature). As melting went on the time lag got shorter. A high correlation was found between the hydrological process and daily temperature during the ablation period. The runoff from April to October was about 80% of the total in the observation period. Compared with the discharge data in 1959, the runoff in 2005 was much more, and the runoff in June, July and August increased by 69%, 35% and 14%, respectively. The rising of temperature is a major factor causing the increase in runoff. The discharges from precipitation and snow and ice melting are separated. The discharge induced by precipitation accounts for about 20% of the total runoff, while snow and ice melting for about 80%.  相似文献   

20.
Wang  Pengpeng  Zhang  Fang  Sun  Song  Wang  Weicheng  Wan  Aiyong  Li  Chaolun 《中国海洋湖沼学报》2020,38(4):1256-1269
The population explosion of jellyfish Aurelia coerulea occurred in Jiaozhou Bay,China in 2009.The potential predation impact of A.coerulea on zooplankton was investigated.Population clearance potential and residence time(t_(1/2)) for copepods were calculated from laboratory clearance rates and measurements of jellyfish size and abundance from May to August 2009 in Jiaozhou Bay.Clearance rates varied widely with prey organisms,but they were not significantly different among various prey concentrations.Medusae captured rotifers,fish larvae and hydromedusae more efficiently than fish eggs,copepods and chaetognaths.Ephyrae captured rotifers and hydromedusae more efficiently than fish larvae and copepods.Clearance rate linearly increased with the cro s s sectional area of A.coerulea(size from 0.3 to7.1 cm).Water temperature also had a marked effect on clearance rate and this was related to the increased beat freque ncy as water temperature increased.In early May 2009,A.coerulea potentially cleared the volume of water in the Bay less than 0.001 times a day,but this value was estimated to be more than 0.3 times a day in July.The t_(1/2) for copepods was less than 6 d in June and July.Abundances of copepods,hydromedusae and chaetognaths were extremely low in 2009 compared to 2008 and 2010(jellyfish non-bloom years).Large predation pressure by the A.coerulea population occurred to control zooplankton communities in Jiaozhou Bay.A.coerulea,when present at a high population level,can be a keystone species in Jiaozhou Bay and control the trophic structure here.  相似文献   

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