Comparisons between the reproductive biology of black bream Acanthopagrus butcheri (Teleostei: Sparidae) in four estuaries with widely differing characteristics

The reproductive biology of Acanthopagrus butcheri has been studied in the permanently open Swan River and intermittently open Moore River estuaries on the lower west coast of Australia (31--32 °S) and in the permanently open Nornalup Walpole and normally closed Wellstead estuaries on the southern coast of Western Australia (34--35 °S). Trends exhibited by gonadosomatic indices, gonadal maturity stages and the sizes and developmental stages of the oocytes demonstrate that A. butcher typically spawns in spring and early summer. However, spawning occurred in salinities ranging from as low as 3.5-8 g L^–1 in the Moore River Estuary to as high as 41-45 g L^–1 in the Wellstead Estuary. Furthermore, water temperatures during spawning were greater in the two northern estuaries (19.7--28.5 °C) than in the two southern and cooler estuaries (17.5--23.4 °C). Histological studies strongly indicate that A. butcheri spawn more than once in a breeding season and demonstrate that the development of its oocytes exhibits group synchrony sensu de Vlaming (1983). The ages and total lengths at which, on average, female and male A. butcheri both first attain maturity in the Swan River Estuary were ca 2 years and ca 215 mm. However, the age at which individual fish in that system reach maturity was influenced by body size. This suggests that the attainment of first maturity at an older age but smaller length in the Moore River and Nornalup Walpole estuaries than is the case in the Swan River Estuary is a consequence of the slower growth rates of A. butcheri in those estuaries. The combination of the young age (ca 2 years) but small length (ca 145 mm) at which maturity is first attained in the Wellstead Estuary could have resulted from selection pressures brought about by high mortality rates and/or heavy fishing pressure in this estuary. The mean fecundity of A. butcheri, based on the combined number of yolk vesicle and yolk granule oocytes found in ovaries just prior to the onset of spawning, was 1580 × 10³. The significance of the sizes at first maturity, minimum legal length for capture, mesh selectivity data and closure of certain regions of estuaries to fishing for the management of the recreational and commercial fishery for A. butcheri is discussed.     

水分胁迫对冷蒿和差不嘎蒿体内水分状况的影响

在土壤正常水分条件下,冷蒿的ψ_w,ψ_π和ψ_π100远远低于差不嘎蒿,RWD、Va及Va·Vs^-1远远大于差不嘎蒿,维系其生命活动的膨压只占差不嘎蒿的30%。土壤极端干旱时,差不嘎蒿的上述参数发生大幅度变化,抗旱能力随之提高。极旱的午后,二种灌木均遭旱害威胁,其水分状况参数值(ψ_w,ψ_O、Va和RWD)相差很小。旱后复灌的情况下,差不嘎蒿上述参数同样发生大幅度变化,各参数值可恢复到对照水平;冷蒿在干旱和复灌期间参数相对变化较小。多水环境使二种灌木束缚水含量明显提高,从外观生长状况看差不嘎蒿优于冷蒿。     

高温高压下成矿元素运移聚集模拟实验

通过不同温度和压力下岩块受力变形的模拟实验,证实了岩块受力变形导致成矿元素的迁移和富集,发现了高温高压下不同元素在同一温压条件下和同一元素在不同温压条件下具有不同的迁移和富集规律。实验表明,构造应力对许多内生金属矿产的形成、矿产中成矿元素的分带现象等都具有十分重要的作用。      

燕山地区中生代构造应力场特征

燕山地区现今的构造、地貌景观,是在漫长的地质历史时期,经历了长期、复杂的建造、改造过程而形成的。从沉积建造及构造形变特点来看,自元古宙至古生界,本区构造运动平缓,建造和改造的特点主要反映基底断裂的控制作用。中、新生代构造运动是燕山地区主要造山作用期,基本特征是强烈挤压形成线状褶皱及推覆构造系统。
中生代时期,本区构造形变显示水平应力作用的主导性,新生代时期,则以均衡代偿导致的隆升作用为主。本文侧重中生代构造应力场及变形挠度场的重塑,借以恢复本区中、新生代构造形变形成的力学过程及运动程式。      

青藏高原西部日土-普兰一带古构造应力值的估算

本文用超显微构造的位错密度法,估算了该地区6次构造事件的古构造应力值。尽管从现在的构造形变特征来看,不同构造事件都是沿近南北方向的伸展或挤压,但其形变强度各不相同,印支运动（晚三叠世）最强,平均差应力值达201MPa,四川运动（白垩纪—早第三纪早期）次之,为183MPa,其它各次构造运动均较弱,阿森特运动（前寒武纪末期）为101MPa,海西运动（早二叠世晚期）为121MPa,燕山运动（晚侏罗世）为130Mpa,喜马拉雅运动（中新世末期以来）为110MPa,加里东运动在本区大部分地方较弱,我们未采集到能反映其构造应力状态的样品。     

石斑鱼鱼虱病的研究 Ⅴ.盐度对南海鱼虱存活的影响

记述了盐度对南海鱼虱CaligusnanhaiensisWu＆Pan不同发育期的影响。在盐度为10以上时,南海鱼虱的幼虫和成虫对盐度的变化有较大的忍耐性,盐度在10—40之间对幼虫和成虫存活没有明显的影响,24h的实验表明,存活率均为100％。然而,虫卵对盐度的变化较为敏感,虫卵孵化的最适盐度范围为20—35,超出此范围虫卵孵化受到影响。当盐度为10时,虽然孵化率可达100％,但孵出的幼虫活动能力差,多数附着于卵囊上而不能正常活动,不久即死亡。盐度为40时,卵子几乎不能孵化。在淡水中,虫卵、幼虫和成虫均不能正常生存。     

鸭绿江口溶解有机碳的研究

１９９６年５月采样测定鸭绿江口溶解有机碳（ＤＯＣ）的含量,得出分布变化特征,并同其它一些河口的溶解有机碳进行了比较。鸭绿江口表层水溶解有机碳的平均含量为２０８μｍｏｌＣ／Ｌ。在盐度大于１．６的河口区,溶解有机碳的分布主要受海水稀释作用控制;在盐度０～１．６的区域溶解有机碳的浓度随盐度的增加而明显增加。在最大混浊带,ＤＯＣ的浓度最高,表明有颗粒有机碳转化为溶解有机碳。丹东市以上流段,河水中溶解有机碳的含量相对较低,说明由丹东市引入的工业及生活污水对鸭绿江水体中溶解有机碳的含量有一定的影响。     

中国对虾生物能量学研究Ⅰ——温度、体重、盐度和摄食状态对耗氧率和排氨率的影响

实验于１９９６年５月～９月对３种规格养殖中国对虾在不同条件下的耗氧率和排氨率进行了测定。结果表明,温度、体重、盐度和摄食状态对其代谢有显著影响。耗氧率（ＱＯ）和排氨率（ＱＮ）与温度正相关,ｌｎＱＯ＝０．０５８Ｔ－２．８９４;ｌｎＱＮ＝０．０７６Ｔ＋１．１１６;而与体重呈负相关,ＱＯ＝０．５１５Ｗ－０．１２６;ＱＮ＝２５．０５Ｗ－０．１９９。在盐度５～３５范围内,中国对虾（３．０２５ｇ±０．０８８ｇ）的耗氧率和排氨率在盐度２８时最小。中国对虾（３．１３ｇ±０．０７２ｇ）摄食沙蚕和配合饲料,在饱食状态下耗氧率比饥饿状态下分别提高了８３．９％和２９．３％,排泄率增加了１１３．８％和９３．６％,表明摄食时蛋白质代谢增加显著。     

斜压海洋动力学的一种三维数值模式──Ⅱ.温度、盐度和垂直涡动粘性系数的计算

根据海水温度和盐度平流扩散方程给出一种数值计算方案并采用混合长度理论给出垂直涡动粘性系数的计算方法。对于温度和盐度方程,其平流过程采用了Lax－Wendroff格式,水平扩散采用显格式,垂直扩散采用隐格式。时间步长主要受平流过程的Courant-Friedrichs-Lewy条件限制。垂直涡动粘性系数计算依据Prandtl混合长度理论,并考虑了海水层化的抑制作用,因而其数值与流场及密度场结构有关。温度、盐度及垂直涡动粘性系数的计算与动力方程中内模态的计算同步进行。应用本模式模拟渤、黄、东海由潮流、密度流和风海流迭加而成的综合海流,得出了良好的结果。     

Influence of Bottom Stress on the Two-layer Flow Induced by Gravity Currents in Estuaries

Baroclinic circulation in highly stratified and partially stratified estuaries is characterised by a two-layer flow: a bottom salt- water inflow and a surface brackish-water outflow. Tidal period variation of the thicknesses of a two-layer flow is observed to be associated with mixing, bottom stress and hydraulic characteristics of superposed tidal and gravity currents. Here, both analytical two-layer hydraulic equations with weak friction and a numerical model including a turbulence closure were utilised to understand the mechanism of the layer tendency within a two-layer flow under different barotropic flow conditions. It has been found that in the weak bottom friction case, a gravity current has two critical solutions at the layer thickness equal to 0·5Hand 0·292H. The layer thickness towards a particular critical solution is dependent on the sign of the bottom stress, i.e. when the bottom stress is opposite (favor) to the bottom gravity current, its layer thickness converges to 0·5H(0·292H). In the case of strong bottom stress and mixing opposing the gravity current, the solutions of the gravity current layer thickness at 0·5Hand 0·292Hwill not be valid. Both mixing and vorticity produced by bottom stress erode the halocline, and produce a high velocity core in the mid-depth, which leads to the thickness of a bottom gravity current greater than 0·5H. These internal hydraulic tendency and mixing processes, varying with time-dependent barotropic tidal current forcing, determine the tidal period variation of the gravity current structure.