池塘圈养模式研究进展

为了探究潜水推流器作用下八边形养殖池内的污物聚集特点,本研究利用物理模型试验的方法,研究潜水推流器不同的布设角度θ、布设距离比d/a (中垂线模式：d1为推流器叶轮轴线中点与最近的池壁之间的距离,a1为八边形养殖池长边边长;对角线模式：d2为推流器叶轮轴线中点与最近的短边边长之间的距离,a2为八边形养殖池排污口与最近的短边边长之间的距离)、推流器数量n和布设模式对八边形养殖池内污物聚集的影响。试验利用高清相机记录养殖池内的污物分布情况,并使用MATLAB分析计算污物与池中心的距离。实验中通过比较不同工况下污物与池中心距离的最大值的大小,衡量养殖池集污性能的优劣。结果显示,潜水推流器的布设角度θ、布设距离比d/a、推流器数量n以及布设模式都影响池内污物聚集的效果。在本研究设置的布设距离比工况下,潜水推流器布设角度θ为45°时集污效果最优,而当布设角度θ大于70°时,随着布设角度增加,八边形养殖池周边出现集污死角,残饵及粪便距离排污口中心变远且饲料离散程度变大;在30°、40°、45°、50°工况下,污物聚集效果随布设距离比d/a的增大逐渐增强,当布设距离比为1/2时集污效果最好。养殖池集污性能随潜水推流器数量的增加而整体呈现增强的趋势,尤其是潜水推流器数量从1增加至2时,集污性能明显提升,但是持续增加后,集污性能不再有明显的提升。其余设置条件相同的情况下,对角线布设模式下的养殖池集污性能明显优于中垂线布设模式。研究表明,潜水推流器采取对角线模式,布设时不少于2个,布设角度θ为45°附近,此时八边形养殖池集污性能较优。研究结果可为八边形养殖池内潜水推流器的布设方式提供依据与指导。

     

杭州湾北部安氏白虾体长与体重关系的季节变化特征

为掌握安氏白虾（Palaemon annandalei）的生长特性,根据2018年2月、5月、8月和11月于杭州湾北部（30°37''N~30°47''N,121°26''E~121°59''E）进行的张网调查数据,利用幂函数、相对体重和单因素方差分析等方法对其体长与体重关系、肥满度等进行研究。结果显示,安氏白虾的体长、体重组成均具有显著的季节变化特征,从春季至冬季,平均体长和平均体重均呈现逐渐下降的趋势,平均体长和平均体重的季节差异显著（P<0.05）。体长与体重关系参数a为条件因子,反映出安氏白虾种群所处环境的优劣,a值夏季最高,冬季最低,从春季到冬季呈现先升高后又逐渐降低的变化趋势,参数b为异速生长因子,可用来判断安氏白虾种群是否处于匀速生长,b值表现出与a值相反的变化趋势。协方差分析表明,安氏白虾体长与体重关系参数仅春季和夏季间无显著性差异（P>0.05）,其余季节之间均存在显著性差异（P<0.05）。安氏白虾的肥满度从春季到秋季逐渐上升,秋季达到最高值,冬季又降至最低值。方差分析显示,春季和夏季间的肥满度无显著性差异（P>0.05）,其余季节间肥满度均具有显著性差异（P<0.05）。研究表明,杭州湾北部安氏白虾体长与体重关系参数a和b具有显著的季节变化特征,并且这个变化受捕食关系、捕捞压力和环境因子等方面影响。     

小展弦比立式曲面网板的水动力性能

为研究不同倾角和迎流冲角下小展弦比立式曲面网板的水动力性能,通过水槽模型实验计算网板的升力系数(C_L)、阻力系数(C_D)、浮力系数(C_Z)和升阻比(K)。结果显示:(1)C_L和K随冲角(α)的增加呈先升后降趋势,C_D随冲角的增加呈上升趋势;(2)无倾角情况下,冲角为30°时,升力系数最大值C_Lmax=1.699,此时C_D=1.140,K=1.490。冲角为15°时,升阻比最大值K_max=2.421,此时C_L=1.120,C_D=0.463;(3)横倾角(β)在-10°～10°变化时,C_Lmax=1.816(α=25°,β=-10°),K_max=3.405(α=10°,β=-10°)。横倾角为-5°和-10°时,网板具有一定浮力。冲角为10°～30°时,CZ平均值分别为0.16和0.25;(4)纵倾角(γ)在-10°～10°变化时,C_Lmax=1.823(α=25°或α=30°,γ=-10°),K_max=2.729(α=5°,γ=-5°)。纵倾角为-5°、-10°和5°时,网板具有一定浮力。冲角为10°～30°时,C_Z平均值分别为0.16、0.18和0.16。结果表明,该网板的最佳工作冲角范围为15°～30°,该冲角范围内网板C_L>1.1且K>1.45。     

六边形开口方形人工鱼礁阻力系数数值模拟与模型试验比较研究

为了对4种不同开口大小的六边形开口方形人工鱼礁在4种迎流角度下数值模拟和水槽模型试验的阻力系数进行对比验证,分别利用水槽模型和数值模拟试验方法对4种不同开口比（γ_ty=0.0625,0.14,0.25,0.39）六边形开口方形人工鱼礁在4种迎流角度（θ=0°,15°,30°,45°）状态下的阻力进行测定,并计算两种方法的阻力系数。结果表明：（1）在数值模拟和水槽模型试验中,人工鱼礁模型阻力均随着开口比的增大而减小;礁体迎流角度的变化可改变礁体阻力,且在4种迎流角度下,人工鱼礁阻力在θ=30°时最大。（2）人工鱼礁数值模拟与水槽模型试验中,当θ为15°、30°和45°时,阻力系数均随着开口比的增加而增加,具有明显的线性关系,且阻力系数在迎流角度θ=30°时最大。（3）数值模拟与模型试验阻力的相对误差在0.12%~17.18%,平均误差7.43%;礁体阻力系数的相对误差在0.03%~14.64%,平均误差5.26%。阻力及阻力系数误差均在20%以下。水槽模型试验与数值模拟阻力和阻力系数相关系数R分别为0.99和0.80,P<0.001,具有极强的相关性。因此,利用数值模拟精细化研究人工鱼礁水动力性能是可行的。     

循环水养殖系统管式射流集污特性试验研究

工厂化养殖池内的污物聚集效果是养殖池设计建造和运行管理的重要指标,对提升养殖技术和管理水平具有重要意义。针对一种典型的工厂化鱼类养殖池,对边侧管式射流系统驱动下的流场特性和污物聚集效果进行研究,探讨了射流角度、射流流速和循环抽吸方式等因素对养殖池内水体流场特性及污物聚集分布规律的影响。利用手持式ADV流速仪在养殖池内进行布点测量,获得各点流速数值,然后利用MATLAB软件进行流场插值构图,研究养殖池的流场分布特性;污物聚集特性采用图像法进行处理分析。研究表明:管式射流驱动作用下,流速从池心向外呈"V"型变化。在射流角度固定为40°条件下,射流速度越大,池心低流速区域范围越小,污物聚集效果越好。当射流速度达到0.3 m/s时,污物基本聚集于池心;在流速固定的情况下,对污物聚集效果存在一个最佳的射流角度,约为40°。池内循环抽吸模式对流场和污物聚集效果同样有着显著的影响。研究表明,采用底部抽吸时,排污孔附近的径向流速与切向流速均高于边侧抽吸模式,且污物聚集效果明显优于边侧抽吸模式。该研究成果可用于工厂化鱼类养殖池管式射流水力驱动系统的优化设计,在不影响养殖对象生长的前提下,可尽量提高射流流速,最佳射流角度一般为40°左右,并尽量采用底部抽吸模式。     

工厂化对虾养殖池管式射流集污水力特性

工厂化养殖池内水体的流场分布特性直接决定了其对残饵、粪便等的排污性能。本实验研究了管式射流驱动模式下,射流角度与射流流速对养殖池内水体流场与污物聚集特性的影响。养殖池流场特性采用点式流速仪进行布点测量,利用MATLAB软件对流场特性进行分析。采用相机采集的养殖池集污效果图像,并利用Photoshop软件与自行开发的不规则图形面积分析软件对图像进行分析。研究表明,流速从池心向外呈"V"型变化,在射流角度固定的情况下,射流速度越大,池心低流速区域越小,污物向池心的聚集效果越好;在流速固定的情况下,存在一个最佳的射流角度,本实验在24 cm/s流速条件下,射流角度为40°时,池内污物聚集效果最优。结论认为在保证养殖对象生长的前提下,可尽量提高射流流速;在24 cm/s流速条件下,最佳射流角度在40°左右。本研究成果可为工厂化养鱼池、养虾池等管式射流水力驱动系统的优化设计提供参考依据。     

秘鲁外海茎柔鱼渔场分布和水温结构的关系

分布在东南太平洋海域的茎柔鱼是重要的经济性头足类,是我国鱿钓船队的主要捕捞对象之一。研究茎柔鱼渔场分布及其与水温的水平、垂直结构等关系,是探索渔场形成机制及其规律的重要内容。本文根据2006年1-12月我国鱿钓船在秘鲁外海的渔捞记录、表温（SST）和5～180 m垂直水温等资料,用3种方法计算SST的水平梯度（D_max,D_square和D_mean）,用ArcGIS 9.0和Sufer 8.0软件分析绘制单船平均日产量(CPUE)和SST、SST水平梯度关系的分布图、水温垂直结构分布图,分析茎柔鱼渔场分布及其与水温结构的关系。结果表明,全年中心渔场分布在80～85°W、10～17°S,SST为18～28 ℃,产量分布呈现明显的空间变化。其中,6-8月为全年最高产时期,其中心渔场分布在81～83°W、12～13°S,相应的SST为18～23 ℃。SST水平梯度与渔场分布关系密切,水平梯度D_square和产量的拟合度为最优（P<0.001）,中心渔场相应的D_square为0.6～1.7 ℃。水温垂直结构分析认为,6-8月通常在81°W、12～13°S附近形成上升流中心,中心渔场基本位于上升流冷水团边缘81°30′～82°30′W。研究认为,该渔场因上升流而形成,主要分布在上升流引起冷水与外洋暖水的交汇区,与SST、SST水平结构、水温垂直结构关系极为密切。     

我国蓝色粮仓科技创新的发展思路与实施途径

为了提高圆形养殖池的自清洗能力,本研究系统开展了污物汇集试验和流场测量试验。实验针对圆形养殖池双管贴壁进水模式,共设计9个不同的角度工况。利用设置在养殖池正上方的相机记录不同工况下污物的汇集过程,通过分析污物的运动过程以及池内剩余的污物量,量化进水管设置角度对养殖池内污物汇集过程以及自清洗能力的影响。利用PIV技术测量了不同工况下距离池底1、2、10、19 cm (底层、近底层、中层、上层)水层的流场,通过分析流态以及水阻力系数C_t、速度均匀系数DU₅₀等养殖池水动力参数,阐明进水管设置角度对养殖池内污物汇集以及自清洗能力的影响机制。结果显示,进水管设置角度明显影响养殖池的自清洗能力,自清洗能力随着进水管设置角度的增大先增大后减小,在45°~50°工况时养殖池自清洗能力最优;进水管设置角度通过影响底层流速大小和流态影响养殖池的自清洗能力,流速大小决定污物能否起动,流态决定污物能否汇集至出水口。因此,在实际循环水养殖生产中建议将与本研究中类似的养殖池的进水管角度设置为45°~50°,以提高养殖池的自清洗能力,提升循环水养殖系统的综合性能。

     

不同姿态下仔稚鱼采样网用台字形沉降板水动力特性

定量仔稚鱼采样网的使用有利于评估渔业资源补充量和群体数量的动态变化, 为进一步提升渔业资源的可持续利用提供决策依据。为掌握采样网用沉降板水动力特性, 本研究利用水槽模型实验探究仔稚鱼采样网用台字形沉降板在不同倾斜姿态下(内、外、前、后)的水动力性能变化, 并利用 OpenFOAM 的数值模拟方法分析不同姿态下沉降板周围流场变化。结果显示: (1) 不同姿态下沉力系数随倾角和冲角增大均呈先增大后减小趋势, 其均在倾角 5°时达到最大, 内、外倾斜下最大值分别为 1.75 和 1.77 (α=25°), 前、后倾斜下最大值均为 1.78 (α=25°); 阻力系数随倾角增大逐渐减小, 随冲角增大逐渐增大; 沉阻比随倾角和冲角增大均呈先增大后减小趋势, 内、外倾斜下分别在倾角 20°和 10°时最大, 为 3.73 和 3.76 (α=20°), 前、后倾斜下均在倾角 5°时最大, 分别为 3.67 和 3.71 (α=20°)。压力中心系数在不同冲角下基本保持不变, C_pc 随倾角增大逐渐增大, C_pb 随倾角增大基本保持不变。(2) 沉降板外侧的流速随倾角增大逐渐减小; 外倾状态下沉降板边界层分离点随倾角增大逐渐向翼板前缘移动; 前、后倾状态下沉降板后部的流速衰减区随倾角增大逐渐增大。本研究阐明了不同倾斜状态下沉降板的水动力性能变化, 为进一步合理安装和调整沉降板工作姿态提供科学依据。     

热带中西太平洋金枪鱼延绳钓渔获物组成及其多样性

利用金枪鱼漂流延绳钓作业方式, 于 2018 年 5 月至 2019 年 3 月期间在热带中西太平洋海域(2°03′~11°17′S, 163°14′~173°35′E)进行渔获取样, 分析渔获组成及物种多样性, 并使用广义线性混合模型(GLMM)和圆形统计方法分析渔获水深、月相等时空要素对物种多样性、目标种类和兼捕 CPUE 等影响。结果表明: (1) 3673 尾渔获隶属于 9 目 21 科 30 属 35 种, 其中目标种类大眼金枪鱼(Thunnus obesus)和黄鳍金枪鱼(Thunnus albacores)为优势种, 蓝枪鱼(Makaira nigricans)、长鳍金枪鱼(Thunnus alalunga)、镰状真鲨(Carcharhinus falciformis)、帆蜥鱼(Alepisaurus ferox) 和紫魟(Pteroplatytrygon violacea)为重要种; (2)大眼金枪鱼、黄鳍金枪鱼以及兼捕种类 CPUE 分别为(1.662± 0.89) ind/千钩、(1.39±1.45) ind/千钩、(2.52±1.27) ind/千钩。渔获多样性指数 Shannon-Wiener 指数(H′)、Margalef 指数(D)、Pielou 指数(J)分别为(1.78±0.28)、(2.53±0.60)、(0.79±0.09); (3) GLMM 结果显示, 月相(余弦)对大眼金枪鱼的 CPUE 的具有极其显著的影响(P=0.001, CPUE 在满月较高, 而在新月较低), 而月相(正弦)对黄鳍金枪鱼 CPUE 具有边际显著影响(P=0.067, CPUE 在上弦月较高, 而在下弦月较低), 月相兼捕 CPUE 则没有显著影响, 水深对 CPUE 具有极显著的影响(P＜0.001); (4)月相对多样性指数均不存在显著影响, 但水深对渔获 Shannon-Weiner 指数 (H′)和 Margalef 指数(D)均有显著影响(P＜0.001)。研究结果反映出热带中西太平洋海域物种丰富、群落的复杂程度较高、稳定性较好, 群落对环境变化、渔业活动等具有较好的耐受性。     

Rare serotype occurrence and PFGE genotypic diversity of Streptococcus agalactiae isolated from tilapia in China

Previously, we reported 10 PEGE types of 85 tilapia Streptococcus agalactiae(GBS), which shifted from Streptococcus iniae in China, by using PEGE method. Presently, larger and more representative tilapia GBS were isolated, for the ?rst time in China, to characterize their serotypes and genetic diversities more precisely than had done before. 168 GBS strains were distributed in ?ve provinces of China, in which Guangdong, Guangxi and Hainan were the major ones, holding36.9%(62/168), 37.5%(63/168) and 19.6%(33/168), respectively. Serotypes, Ia, Ib and III, were observed in these strains and the most predominant one was Ia(95.2%), which mainly distributed in Guangdong, Guangxi and Hainan. Ia initially occurred in 2009, it shoot up to 32.1% in 2010,but decreased to 16.1% in 2011 before went up to 45.2% in 2012. Ib sporadically occurred during2007–2011, III onlyoccurred in 2012. 14 different PFGE types, including 4 new types(N, O,P and Q), were observed, in which B, D, F and G were the predominant types, holding 83.9%(141/168) of the total GBS strains. Ia corresponded to 11 PFGE types(A–H, N–P), in which type D predominated(51%). Ib represented 3 genotypes(I, J and Q) and III harbored only 2genotypes(N and F). Type N and Fsynchronously presented in Ia and III. In summary, the genetic diversity of tilapia GBS varied by serotypes and changed with geographical locations and years.Although Iastillpredominated, new rareserotypeIII alreadyoccurred in China.     

Purification and partial characterization of GtHs (cfLH and cfFSH) from Indian walking catfish (Clarias batrachus) (L.) and development of a homologous ELISA for cfLH

Two gonadotropins (GtH; Qa and Qb) were purified by gel filtration and ion exchange chromatography from the pituitaries of Indian walking catfish (Clarias batrachus). The presence of GtH during purification was assessed by in vitro oocyte maturation and in vivo steroidogenic activity, and their identities were determined by elution profiles, molecular weight, biological activities and yield. The molecular weights of Qa and Qb were 37 and 42 kDa, respectively, and composed of distinct subunits (Qa: 20 and 14 kDa and Qb: 26 and 18 kDa). Polyclonal antibodies raised against Qa immunostained Qa, Qb and pituitary GtH cells. A competitive Qa‐ELISA was developed whose sensitivity was 6.25 ng mL^?1 (1.25 ng well^?1) with intra‐ (3.5%) and inter‐ (12.4%) assay coefficients of variation. Displacement curves parallel to the standard were obtained with plasma and pituitary extracts of catfish, Qb and carp GtHII. The assay was validated by measuring the plasma Qa levels after LHRH treatment and in relation to ovarian growth in the female catfish during different reproductive phases. Based on the results, Qa and Qb corresponded to fish LH and FSH respectively. The findings will increase the knowledge of the mechanisms controlling fish reproduction and identification of sensitive phases in fish in captivity for hormonal manipulation.     

Growth hormone (GH) and reproduction: a review

Interaction between growth and reproduction occurs in many vertebrates and is particularly obvious at certain stages of the life cycle in fish. Endocrine interactions between the gonadotropic axis and the somatotropic axis are described, the potential role of GH being emphasised. A comparative analysis of these phenomena in mammals, amphibians and fish, suggests a specific role of GH in the physiology of puberty, gametogenesis and fertility. It also shows the original contribution made by studies on the fish model in this field of investigations.     

Controlled infection of Poecilia reticulata Peters (guppy) with Tetrahymena by immersion and intraperitoneal injection

Tetrahymena is a protozoan parasite, which infects guppy, Poecilia reticulata Peters, and causes substantial economical losses in commercial farms worldwide. Studies of guppy infected by Tetrahymena require standardized infection protocols. The LD50 for Tetrahymena infection of guppies by intraperitoneal (IP) injection was calibrated, and the level obtained was 946 parasites per fish. Guppy infection with Tetrahymena by immersion, imitating the natural route of infection via the integument, was studied under normal or stress conditions. Exposure to cold and netting (CNI) and to cold only (CI) followed by immersion exposure to 10 000 Tetrahymena per mL resulted in 22.5% and 19.2% mortality, respectively, as compared to 14.2% and 10% in groups that were netted only (NI) or non‐stressed (I). Histopathology revealed that immersion infection resulted in a systemic infection. Lysozyme levels, measured 3 weeks after infection, were significantly higher in the CNI group (288 μg per mg protein) compared with CI‐, NI‐ and I‐treated groups (94.5, 64 and 62.3 μg mg^?1, respectively). There was no evident parasite immobilization activity in body homogenates, suggesting no development of acquired immunity. Re‐infection by IP injection revealed no increase in protection in any of the treatment groups, mortality range of 56.3–75%, higher than in the non‐exposed control (40.6% mortality).     

Evaluation of a Fast Method Based on the Presence of Two Restriction Sites in the Mitochondrial ND5 (mt ND5) Gene for the Identification of Scomber Species

The purpose of this work was to evaluate the suitability of a method based on the presence of two restriction sites (for Hae III and Hindf I) in the mitochondrial NADH dehydrogenase subunit 5 (mt ND5) gene to identify Scomber species. The evaluation was performed on 144 reference and market samples by sequencing of the entire 505-bp fragment of the mt ND5 gene and of a 464-bp fragment of the Kocher fragment of the cytochrome b gene (mt Cytb). Sequence analysis of any of the two fragments allows the identification of each of the four Scomber species, but S. japonicus and S. colias had the same restriction sites at the ND5 amplicon and would not have been differentiated by this analysis. Similarly, loss of the Hae III site in some S. scombrus individuals would have misidentified them as not being Scomber. All the market products were correctly labeled except one acquired in Spain labeled as originating in the Atlantic and containing S. japonicus.     

Imported ornamental fish are colonized with antibiotic‐resistant bacteria

There has been growing concern about the overuse of antibiotics in the ornamental fish industry and its possible effect on the increasing drug resistance in both commensal and pathogenic organisms in these fish. The aim of this study was to carry out an assessment of the diversity of bacteria, including pathogens, in ornamental fish species imported into North America and to assess their antibiotic resistance. Kidney samples were collected from 32 freshwater ornamental fish of various species, which arrived to an importing facility in Portland, Oregon from Colombia, Singapore and Florida. Sixty‐four unique bacterial colonies were isolated and identified by PCR using bacterial 16S primers and DNA sequencing. Multiple isolates were identified as bacteria with potential to cause disease in both fish and humans. The antibiotic resistance profile of each isolate was performed for nine different antibiotics. Among them, cefotaxime (16% resistance among isolates) was the antibiotic associated with more activity, while the least active was tetracycline (77% resistant). Knowing information about the diversity of bacteria in imported ornamental fish, as well as the resistance profiles for the bacteria will be useful in more effectively treating clinical infected fish, and also potential zoonoses in the future.     

Effect of iodophor disinfection of non‐hardened Salmo trutta eggs on their bacterial and fungus load

This study investigated the efficiency of iodophor disinfection (135 ppm active iodine for 15–30 min) of non‐hardened Salmo trutta eggs against different groups of bacteria and against fungus. Egg samples were taken from non‐disinfected and from disinfected eggs, microorganisms were cultured on specific nutrient media and their mass was measured by turbidimetric methods. Bacteria and fungus mass of non‐hardened eggs could be reduced but not eliminated by iodophor disinfection with 135 ppm active iodine for 15 min. The extent of reduction was 47–65% (Experiment 1). The efficiency of disinfection increased with disinfection time as the reduction in bacteria and fungus mass was 40–55% after 15 min and 58–74% after 30 min (Experiment 2). Disinfection efficiency of iodophor solution diluted in water (reduction 49–57%) and of iodophor solution diluted in sodium chloride solution iso‐osmolar to the oocytes (reduction 52–61%) was similar (Experiment 3). The reduction in bacteria and fungus mass was persistent as it was 39–72% lower in embryos deriving from disinfected eggs than in embryos deriving from non‐disinfected ones (Experiment 4). In conclusion, the tested disinfection method is inadequate to eliminate pathogens completely but it could positively influence immune defence of eggs and embryos.     

Influence of the antibacterial herbs, Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia on the survival, growth and bacterial load of Penaeus monodon post larvae

The indiscriminate use of antibiotics and chemicals in shrimp hatcheries has led to biomagnification and that in turn could lead to rejection of a whole consignment. The application of the bioencapsulation technique as a tool for curative treatment in shrimp larvae was investigated. Herbs having antibacterial properties such as Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia (methanolic extracts) were bioencapsulated in Artemia and fed to Penaeus monodon post larvae PL 1–25. The post larvae were reared in a medium inoculated with pathogenic bacteria such as Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella typhi and Vibrio sp. Post larvae reared in the non-inoculated water and fed with non-enriched Artemia exhibited 90% survival, highest specific growth rate (12.43%) and reduced bacterial load. P. monodon reared in the bacterial inoculated water and fed with the non-enriched Artemia exhibited the lowest survival (10–30%), specific growth rate (8.42–9.1%) and increased bacterial load (2.86 × 10³ to 3.76 × 10⁵ cfu/g). The methanolic extracts of the herbs helped to increase survival and specific growth rate and reduced bacterial load in the P. monodon culture system. Among the three herbal extracts, P. corylifolia enriched Artemia fed post larvae showed the tendency to higher survival (>50%), growth rate (11.5 averaged) and low bacterial load (1.12 × 10⁵ cfu/g). This revised version was published online in August 2006 with corrections to the Cover Date.