基于上升流效应的单位鱼礁建设模式研究

人工鱼礁上升流是流场区水体垂向交换、混合、循环的主要驱动因素之一,是人工鱼礁环境功能实现的基本环节。该研究通过数值实验方法获得4种投放量、7种布设间距共28种建设模式下米字型鱼礁上升流流场数据,提取并分析了代表流场作用能力的3个性能指标来评估上升流流场效应并准确定位上升流区,包括上升流,强度,范围及位置参数,进而为合理规划单位人工鱼礁建设模式提供参考。结果表明,4种投放量在0～1.5倍鱼礁单体边长(S_(la))的布设间距下相对体积效率最佳,布设间距为0～1.5 S_(la)、投放量为432空m~3时上升流平均相对速度最高;0与1.5 S_(la)布设间距下单位体积贡献率较高;1.0～3.0 S_(la)布设间距的上升流相对面积较高,对应相对面积高度基本相同,为0.5～1.0。进一步以不同海域上升流作用形式差异为出发点,指出确定上升流区的新思路,并提出以上升流流场最佳效应为前提的最优单位人工鱼礁建设模式选择方法。     

基于单位鱼礁规模的米字型人工鱼礁流场效应定量研究

流场效应是人工鱼礁发挥其生态效应的基础,流场效应强弱受单位鱼礁规模影响,同时是衡量人工鱼礁建设模式优劣与规划人工鱼礁建设模式的重要参考因素,流场体积是表征流场效应强弱的重要指标。本研究基于数值实验方法,分析米字型人工鱼礁在4种布设模式下28种单位鱼礁规模的流场体积变化规律,并建立上升流、背涡流流场体积与人工鱼礁建设规模指标的多元非线性模型。结果表明,单位鱼礁建设一级指标投放量(T_a)、布设间距(L_d)及目标速度比(R_u)与上升流体积分别呈线性、三次函数及幂函数关系,建立上升流体积回归模型为V_u=T_a×(0.002L_r~2-0.055L_r-2.429V_R×R_u+0.011R_u~(-1.833)+0.227L_d+0.437),回归拟合R~2为0.957,相对误差为18.61%。与背涡流体积分别呈幂函数、三次函数及指数函数关系;结合单位鱼礁建设二级指标相对边长(L_r)、容积率(V_R),背涡流体积回归模型为V_b=R_u×(-0.543L_r~2+2.388L_r)–51.779V_R~2+75.045V_R+1.449×10~(-4)T_a×e~(12.049 Ru)+1.620L_d×T_a,回归拟合R~2为0.938,相对误差为10.09%。该流场体积回归模型可用于规划指导均匀布设模式的人工鱼礁建设,为"减量增质提效"的人工鱼礁建设策略提供参考。     

布设间距对多孔方型人工鱼礁流场效应影响的数值模拟研究

采用计算流体动力学(CFD)技术,研究了不同布设间距下,多孔方型人工鱼礁周围水流运动的规律,旨在为深入研究人工鱼礁的集鱼原理和海洋牧场建设中人工鱼礁的投放和布设提供更多参考。本研究采用了4种布设间距,分别为0.5、1、1.5和2倍鱼礁高度,基于计算机数值模拟技术,模拟了速度为0.8m/s的水流流经2个礁体的过程,分别观察鱼礁周围水流运动情况。结果显示,多孔方型人工鱼礁内部和周围存在缓流区、背涡流区、上升流区、死水区等有显著特征的区域;多孔方型人工鱼礁上升流的最大速度与来流速度的比值约为0.95倍;多孔方型人工鱼礁周围上升流最大抬升高度与鱼礁高度之比约为2.1;多孔方型人工鱼礁的结构在一定程度上为鱼礁周围的流态多样性提供了较有利的作用;多孔方型人工鱼礁的布设间距对2个鱼礁单体间的旋涡数量和旋涡方向有较大影响,也对涡量大小和涡量分布范围产生影响。研究表明,在一定范围内,布设间距越大,涡量越大,分布范围越广,但超过一定范围后,涡量不再增大,分布范围也不再扩大;多孔方型人工鱼礁的布设间距越大,背涡流在X方向和Y方向的影响面积越大。研究结果清晰地展现了不同布设间距下的人工鱼礁的流场效应,对在特定条件下进行人工鱼礁投放和布设具有重要意义。     

复合M型人工鱼礁粒子图像测速二维流场试验研究

为了获得复合M型人工鱼礁的流场效应,为鱼礁的结构设计提供理论依据,选取3个不同水流流速(6.7 cm/s、11.0 cm/s、18.0 cm/s),采用粒子图像测速(PIV)技术,对复合M型人工鱼礁的二维流场进行测试。结果表明:礁体迎流面和背流面分别产生上升流和背涡流,其规模随着来流速度的增加而增大;当鱼礁圆柱孔与流向夹角为90°时所产生的上升流高度为礁高的53%~90%,背涡流面积为迎流面积的0.7~1.3倍;夹角为0°时上升流高度为礁高的33%~83%,背涡流面积为迎流面积的40%~60%;90°工况下上升流平均流速是0°工况时的1.1~2.7倍,背涡流的最大回流速度为0°时的3.0~9.0倍。鱼礁投放时采用鱼礁圆柱孔与水流流向垂直的摆放形式流态较好。     

不同侧板结构对八棱柱型人工鱼礁流场效应的影响

为了解侧板结构对八棱柱型人工鱼礁流场效应的影响，实验基于计算流体力学方法(computational fluid dynamics, CFD)，利用大涡模拟(LES)对4种不同侧板结构的八棱柱型人工鱼礁周围流场变化进行数值模拟，并以上升流体积、背涡流体积和向上输运通量等为流场效应指标进行了分析，同时利用水槽实验对数值模型进行验证。结果显示，水槽实验流速与2种尺寸数值模拟流速的均方根误差最大不超过0.065。0°垂直迎流时，2种来流速度下，A型、C型和D型礁的上升流体积较B型礁最大分别高35.6%、244.1%和80.1%，背涡流体积较B型礁最大分别高193.5%、115.8%和88.8%。C型和D型礁的向上输运通量均大于A型礁，且C型礁最大向上输运通量是D型礁的1.29倍。不同迎流角度下，C型礁和D型礁的上升流体积和背涡流体积在4种角度下差异显著，且迎流面投影面积和上升流体积及背涡流体积之间相关系数较小。研究表明，实验所采用的数值模拟准确可靠；侧板数量增加对于提升八棱柱型人工鱼礁流场效应尤其是上升流效应作用明显；下层侧板固定时，上层为倾斜侧板有利于提升礁体的上升流效应，上层为垂直侧板时...     

人工鱼礁流场效应的模型实验

摘要：本文针对正方体、金字塔及三棱柱人工鱼礁模型，选取三个不同工况6m/s、9m/s和12m/s，通过风洞实验研究不同类型人工鱼礁单体和不同组合正方体模型的流场效应。结果表明，模型迎流面和背流面分别产生上升流和背涡流，其规模随来流速度的增大而增大；相同来流速度下，同种模型空心模型的上升流和背涡流规模较实心模型小，空心模型背涡流回流速度随模型空隙率增大而减小；不同模型z方向的湍流强度均大于x方向。对于组合模型，随着来流速度的增大，中心点流速均逐渐增大；一定来流速度下，当模型间距在1~1.5倍模型尺度时，流场变化最大；且模型平行组合比垂直组合产生的流场效应更大。     

基于结构差异性正方体鱼礁的流场效应研究

人工鱼礁结构差异是影响流场规模效应的主要因素之一,本研究选择大字型、米字型、回字型、交叉型、框架型和实体型6种鱼礁单体,分析均匀布设模式下礁体自身结构特征对流场效应的影响规律,进一步建立结构差异性单位鱼礁的规模效应模型.基于流场效应规律提出礁体结构特征指标分别为鱼礁空方体积比、透空率和迎流面相对截面积,进一步得到上升流...     

组合式金字塔型人工鱼礁水动力学分析

人工鱼礁是海洋牧场的重要组成部分,对于修复海洋生态环境、提高渔获量有重要价值。人工鱼礁的投放可以使得鱼礁周围流场发生变化,对于鱼类摄食、庇护都有重要的影响。本研究对人工鱼礁的水动力学特性进行研究,采用计算流体动力学软件Fluent和基于N-S方程对组合式金字塔型人工鱼礁的流场进行分析。比较了4种流速(0. 1、0. 2、0. 3和0. 4 m/s)下鱼礁流场的变化情况,得到了周围涡量和压力的分布特征,给出了该型人工鱼礁的三维紊流区,并同其他类型人工鱼礁进行了对比。结果显示:涡量主要分布于导流盘后方区域,且越远离导流盘的地方涡量越弱;不同来流速度下,上升流的最大高度约为鱼礁高度的1. 53倍,鱼礁涡量区高度约为鱼礁的高度,背涡区长度随着水流速度的增加而增加;不同流速下,紊流区的范围基本不变。     

基于流场数值仿真的人工鱼礁组合优化研究

基于特征礁水槽集鱼实验,研究了不同结构人工鱼礁和不同背景速度下黑鲷幼鱼在各流速区段出现频度,以鱼类出现频度高、水平流速为背景速度的0.7倍和0.8倍以下的流场空间体积作为背涡流范围指标,以垂向上升流速为水平来流速度的0.1倍和0.2倍以上的空间体积作为上升流范围指标,基于Fluent、采用大涡模拟法(LES)的湍流模型,进行数值水槽建模,以4种单位鱼礁组合方案为例来分析不同组合流场效应的差异和优劣。研究表明,边长3 m的正方体鱼礁,以20～30个单礁、1～2倍礁距进行五点式、对称型单位鱼礁组合投放为宜,这样既能发挥礁体的协同效应,又能使单位鱼礁的调控范围达到最大化。     

规模化透水性人工鱼礁阻流效应的数值模拟

为在大尺度海洋模型中合理体现透水性人工鱼礁组合，基于海洋数值模式FVCOM（finite volume community ocean model）模拟了大陈岛拟建人工鱼礁区的水动力情况，比较了阻滞力法、实心礁法和附加底摩擦法在投礁前后的垂向流速、礁顶平面流速、水体向上输运通量和背涡流体积的差异，并根据投礁前后的流速差异，应用经验公式预测了投礁一年后底床泥沙冲淤情况。数值模拟结果表明，礁体组合迎流面产生上升流，礁体背流面流速减小，涨急时刻所形成缓流区长度在礁体组合长度20倍以上，年底床淤积厚度约0.05 m。阻滞力法以减少来流的动态功率密度来模拟礁体对水流的阻滞作用，可有效合理地实现对透水性人工鱼礁流场效应的模拟，避免了实心礁法在透水性鱼礁模拟中过高估计流场效应的问题，也没有附加底摩擦法只适用于低矮礁体的缺陷。阻滞力法可根据透水性礁体的造型、迎流面积、组合个数、布放方式和所处水层而设置各向和各水层的阻流参数，不仅适用于置底型透水性鱼礁，也适用于浮鱼礁。阻滞力法的建立、完善和应用对于今后的人工鱼礁水动力学和生态动力学研究具有重要意义。     

Artificial reef placement: a red snapper,Lutjanus campechanus,ecosystem and fuzzy rule‐based model

Abstract This study on reef placement involves two aspects: (1) the development of a bioenergetics model for red snapper, Lutjanus campechanus (Poey), in Gulf of Mexico waters off the coast of Alabama, where significant numbers of artificial reefs are thought to exist, and (2) a fuzzy rough set model by which parameters determined from the bioenergetics model can provide a decision tool for optimally spacing artificial reefs during deployment. The bioenergetics and consumption rates of L. campechanus by age class foraging on artificial reefs in the Gulf of Mexico off the coast of Alabama provided input into the fuzzy rule‐based model. After conducting multiple simulations, highest certainty in optimal reef spacing was achieved for reef distances between 0.50 and 0.95 km such that no more than two fit within a 1‐km² area. Results can inform fisheries managers about placement of artificial reefs to affect the health and survival of reef‐associated species.     

Effect of stocking density on survival and growth performance of pikeperch, <Emphasis Type="Italic">Sander lucioperca</Emphasis> (L.), larvae under controlled conditions

The effect of stocking density on the survival and growth of pikeperch, Sander lucioperca (L.), larvae was examined in two consecutive experiments. In experiment I, 4-day-old larvae [body wet weight (BW): 0.5 mg; total body length (TL): 5.6 mm] were reared in 200-l cylindro-conical tanks in a closed, recirculating system (20 ± 0.5°C) at three stocking densities (25, 50 and 100 larvae l⁻¹) and fed a mixed feed (Artemia nauplii and Lansy A2 artificial feed) for 14 consecutive days. At densities of 25 and 100 larvae l⁻¹, growth rate and survival ranged from 2.7 to 1.9 mg day⁻¹ and from 79.2 to 72.3%, and fish biomass gain ranged from 0.6 to 2.0 g l⁻¹, respectively. There were two periods of increased larval mortality: the first was at beginning of exogenous feeding and the second during swim bladder inflation. In experiment II, 18-day-old larvae (BW: 35 mg; TL: 15.6 mm) obtained from experiment I were reared under culture conditions similar to those of experiment I, but at lower stocking densities (6, 10 and 15 larvae l⁻¹). The fish were fed exclusively with artificial feed (trout starter) for 21 consecutive days. At densities of 6 and 15 larvae l⁻¹, the growth rate and fish biomass gain ranged from 28.8 to 23.1 mg day⁻¹ and from 2.0 to 3.3 g l⁻¹, respectively. The highest survival (56.5%) was achieved at a density of 6 larvae l⁻¹. Mortality at all densities was mainly caused by cannibalism II type behaviour (27–35% of total). In both experiments, growth and survival were negatively correlated and fish biomass gain positively correlated with stocking densities. The present study suggests that the initial stocking density of pikeperch larvae reared in a recirculating system can be 100 individuals l⁻¹ for the 4- to 18-day period post-hatch and 15 individuals l⁻¹ for the post-19-day period.     

塔型桁架人工鱼礁流场效应及稳定性

本研究利用物理模型试验和粒子图像测速技术,对塔型桁架人工鱼礁模型在6种换算流速0.031 m/s、0.063 m/s、0.095 m/s、0.126 m/s、0.158 m/s和0.190 m/s (实际流速0.2 m/s, 0.4 m/s, 0.6 m/s, 0.8 m/s, 1.0 m/s和1.2 m/s)下产生的流场效应与物理稳定性进行研究。结果表明,流速达到1.2m/s时,礁体不会发生漂移和倾覆,说明该礁型具有良好的稳定性。单体礁在45°和90°迎流方式下,最大上升流流速和上升流平均流速随来流速度增加而递增,90°摆放单体礁最大上升流流速为来流速度的15.6%～21.0%, 45°摆放单体礁最大上升流流速为来流速度的16.3%～23.5%;上升流面积和高度随来流速度的增大先增加后减小,均在来流速度为0.095 m/s时出现最大值;缓流区面积均随来流速度的增加而减小;在相同来流速度下, 45°迎流时礁体缓流区面积大于90°迎流;在45°和90°摆放方式下,缓流区长度与礁高比值均随来流速度的增加呈下降趋势,且下降趋势逐渐平缓;45°迎流时缓流区长度为礁体高度的13～24倍, 90°迎流时缓流区长度为礁体高度的11～22倍。塔型桁架人工鱼礁礁体前后没有涡流形成,但具有较好的缓流作用,在礁体后方形成了较大规模的缓流区。     

Relationship between concentrations of odorous compounds and biomass of phytoplankton and actinomycetes in freshwater ponds of Beijing,China

The odorous compounds including geosmin and 2-methylisoborneol (MIB) were detected in intensively cultivated freshwater ponds in Beijing, China, by coupling head space solid-phase microextraction with gas chromatography mass spectrometry (GC-MS). Moreover, the biomass of phytoplankton and actinomycetes in the fishponds were determined simultaneously, and the relationship between the concentrations of these odorous compounds and the biomass of phytoplankton and actinomycetes was assessed. The results showed that among the odorous compounds detected, geosmin was the main one, and concentrations of 1.22–35.58 ng l⁻¹ were found in all fishponds. Besides, MIB with 1.39–6.00 ng l⁻¹ was found in parts of fishponds. Six phyla and 22 genera of algae were observed in the fishponds with a biomass of 17.33–178.34 mg l⁻¹, among which dominant phyla were Bacillariophyta and Euglenophyta. Four genera of actinomycetes with a gross biomass of 0–76 × 10⁴ ind l⁻¹ were found in the fishponds, of which Streptomyces spp. was the dominant genera. This indicated that geosmin concentration in fishponds was related with the total biomass of the dominant algae. The results showed that Melosira spp. and Cyclotella spp. were the main microalgae to cause off-flavor in Beijing’s intensively cultivated freshwater ponds in summer and autumn, while Euglenophyta and other algaes played a small role in causing off-flavor.     

人工鱼礁区不同底质对底栖游泳生物群落特征的影响

为探究人工鱼礁投放后的不同底质对底栖游泳生物群落结构特征的影响,实验以海区中央投放的构件礁划分半径为20、400和600 m 3个样带,采用地笼与摄像相结合的方法,分别于2017年6月和8月、2018年6月 (2次)、2019年6月和7月在小竹山岛人工鱼礁区进行了6个航次的调查。应用相对重要性指数 (IRI)、主坐标分析 (PCoA)和单因素方差分析等分析群落时空组成变化,利用广义加性模型 (GAM)研究环境因子对单位捕捞努力量 (CPUE)和多样性指数的影响。IRI和PCoA测定结果显示,地笼主要捕获日本蟳、海燕、大泷六线鱼、许氏平鲥及其他梭形鱼类;摄像主要捕获海燕等棘皮类、葛氏长臂虾、纹缟虾虎鱼、六丝钝尾虾虎鱼、钟馗虾虎鱼及矛尾刺虾虎鱼。单因素方差分析显示,两种采样方法在200和400 m样带的CPUE均较高,与600 m样带有显著差异,但年份间无显著差异。GAM模型显示,CPUE随投礁年份和底质类型的复杂度增加而增加,与构件礁及石块礁底质呈正相关,且受盐度及温度影响。多样性指数在样带、年际间无显著差异,GAM模型显示,其在地笼渔获物的多样性指数显著高于摄像,并受盐度、透明度影响,但与底质类型无关。本研究揭示了不同底质对底栖游泳生物的影响,证明了地笼与摄像结合调查方法的互补性,为多种鱼礁底质的管理提供参考依据。     

Composition of ovarian fluid in endangered Caspian brown trout, <Emphasis Type="Italic">Salmo trutta caspius</Emphasis>, and its effects on spermatozoa motility and fertilizing ability compared to freshwater and a saline medium

In this study, ovarian fluid composition and its effects on the motility and fertilizing ability of sperm were studied in endangered Caspian brown trout, Salmo trutta caspius, and were compared with a saline activation medium (125 mM NaCl, 30 mM Glycine, 20 mM Tris–HCl, pH = 9.0) and freshwater as the control. The ovarian fluid was composed of sodium 164.4 ± 4.4 mM l⁻¹, potassium 1.8 ± 0.1 mM l⁻¹, calcium 0.6 ± 0.1 mM l⁻¹, magnesium 0.4 ± 0.02 mM l⁻¹, chloride 127.4 ± 5.9 mM l⁻¹, total protein 389.5 ± 89.6 mg 100 ml⁻¹, cholesterol 9.3 ± 1.2 mg dl⁻¹, and glucose 3.3 ± 0.2 mM l⁻¹. The percentage of motile spermatozoa and the duration of sperm motility were significantly higher in ovarian fluid (62 ± 3%, 74.6 ± 0.8 s) than freshwater (35 ± 4%, 44 ± 1 s), but they did not differ significantly from saline medium (56 ± 3%, 74.3 ± 0.7 s) (P > 0.05). Higher eyeing rates were observed after the activation of sperm in ovarian fluid and saline solution than freshwater when 35,000 or 350,000 spermatozoa per egg were added into the activation media. However, no significant differences were observed at higher concentrations of spermatozoa per egg (730,000) (P > 0.05). Also, this study showed that the ovarian fluid composition can be considered as a species-specific character among salmonid fishes. As a conclusion, the results of this study recommend the use of ovarian fluid or the saline solution as an activation medium in the artificial reproduction of Caspian brown trout.     

Effects of stocking density on survival and growth of juvenile tench (<Emphasis Type="Italic">Tinca tinca</Emphasis> L.)

In two 120-day experiments, performed in the laboratory at 22°C, the effects of stocking density on the survival and growth of juvenile tench (Tinca tinca L.) were evaluated. Fish were kept in fibreglass tanks, supplied throughout with flow of artesian water, and fed a dry diet for salmonids, in excess, supplemented with restricted amounts of Artemia nauplii. In the first experiment four-month-old juveniles (0.31 ± 0.04 g and 32.00 ± 1.17 mm TL) were stocked at four densities—0.18, 0.88, 1.05, and 2.10 g l⁻¹. Survival was high (>89%) for all treatments. Final densities ranged between 1.10 g l⁻¹ (significantly lowest) and 10.46 g l⁻¹ (significantly highest). The density increase was significantly higher (611%) for fish stocked at the lowest initial density (0.18 g l⁻¹) than for fish stocked at 0.88, 1.05, and 2.10 g l⁻¹, for which the density increase averaged 457%. In the second experiment, 4.5-month-old juveniles (0.58 ± 0.17 g and 39.54 ± 0.83 mm TL) were stocked at three densities—1.05, 3.00, and 4.00 g l⁻¹. Survival was high (>96%) for all treatments. Final densities ranged between 4.08 and 16.53 g l⁻¹ and were significantly higher for greater initial densities. The density increase was greatest (413%) for fish stocked at the highest density (4 g l⁻¹) and was not significantly different for fish stocked at 1.05 and 3 g l⁻¹. Considering all the densities in the two experiments, for stocking at 4 g l⁻¹ the final density was 15 times higher than that reached after stocking at 0.18 g l⁻¹, without harmful effects on survival and growth. This final density (equivalent to 16.53 kg m⁻³) is in the range recommended for other fish species in this period under intensive conditions.