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太湖梅梁湾生物控藻围栏内鲢、鳙摄食生态和控藻效果的研究
Alternative TitleEcological studies on food habits of two biomanipulation fish, silver and bighead carp, in a large fish pens with their effects on water quality and plankton communities
柯志新
Subtype博士
Thesis Advisor谢平
2008-06-12
Degree Grantor中国科学院水生生物研究所
Place of Conferral水生生物研究所
Keyword 生物操纵 富营养化 蓝藻水华 食性 日摄食量 生态位 滤食率 资源多态
Abstract利用滤食性鱼类(鲢、鳙)的直接牧食来控制水体浮游植物过度生长的非经典的生物操纵理论被认为是特别适合于有大型群体藻类(如微囊藻)爆发、且水体浮游动物以小型种类为主的水体。近年来国内对蓝藻水华控制的应用需求日益增加,运用放养鲢、鳙鱼的方式控制水体蓝藻的过度生长已经在太湖、滇池、巢湖等水体广泛试用。本文系统研究了太湖梅梁湾生态修复区内生物控藻围栏中的鲢、鳙鱼的摄食生态学以及其对水质和浮游生物的影响,并探索了春末夏初太湖梅梁湾浮游植物的群落结构的季节演替的驱动因子。主要结果如下: 围栏内的鲢、鳙都表现出了较快的生长速度,2005年鲢、鳙的年平均生长速度分别为3.18 g day-1和4.05 g day-1。6月到7月之间鲢的生长速度最快,达到8.14 g day-1,而5月到6月之间鳙鱼的生长速度最快,为10.5 g day-1。鲢、鳙都以浮游动植物为食,鳙对浮游动物的摄食更多一些。在鲢的肠含物里浮游植物始终都是占绝对优势的,周年平均的生物量比例为68.5%。然而,鳙鱼的肠含物中除了7月和8月以蓝藻为主要优势以外,其余时间都是以浮游动物占绝对优势,周年平均浮游动物组成为64.7%。 鲢、鳙均具有明显的昼夜摄食节律,在鳙鱼中表现得更为明显。7-10月间,鲢、鳙的摄食高峰一般发生在下午2点到傍晚6点,摄食低谷一般在早上6点到10点之间; 5月的摄食节律和其他月份近乎相反,摄食高峰发生在早上6点,分析认为这也许和摄食的主要浮游植物的种类不同有关。采样期间,鲢的摄食强度显著高于鳙,鲢的最大日粮发生在8月,为19.93%,鳙的最大日粮发生在9月,为11.61%;二者的最低日粮都发生在10月,分别为3.53%和4.25%。平均来看,鲢的日粮需求(13.62%)是鳙鱼(6.79%)的两倍多。鲢、鳙对浮游植物的清除能力平均分别为0.73 L g-1 h-1和0.31 L g-1 h-1 ;对浮游动物的清除能力分别为0.32 L g-1 h-1和0.76 L g-1 h-1。鲢摄食清除蓝藻的能力远大于鳙,我们认为鲢是比鳙更加优越的控藻种类。为了更有效的改善水质,以控藻为目的的养殖行为要严格控制鳙鱼的放养比例。 我们比较研究了2005年围栏内外的理化因子和浮游生物群落结构的差异。由于鱼类的排泄、扰动等作用,围栏内营养盐的平均浓度比围栏外的高,但差异不是很明显。鲢、鳙的摄食对浮游甲壳动物群落结构产生了显著的影响,围栏内外的周年平均浮游甲壳动物的总生物量分别为1.83 mg L-1和2.39 mg L-1,围栏外的显著高于围栏内(T-test,P < 0.05);围栏外枝角类的周年平均生物量为1.86 mg L-1,显著高于围栏内的1.26 mg L-1(T-test,P < 0.05);围栏内外桡足类的周年平均生物量分别为0.57 mg L-1和0.53 mg L-1,围栏内外差异不显著。围栏内的桡足类与枝角类的比值的周年平均值为0.67,围栏外的为0.57,除了7月和10月以外,围栏内的桡足类与枝角类的比率总是高于围栏外,但统计分析没有表现显著差异。围栏内的周年平均浮游植物总生物量(8.39 mg L-1)低于围栏外(9.74 mg L-1),最大生物量出现在8月(围栏内为28.52 mg L-1,围栏外为54.43 mg L-1),周年浮游植物总生物量围栏内外没有显著差异。在4月至11月间围栏内微囊藻的平均生物量(3.78 mg L-1)远低于围栏外(7.95 mg L-1),同时围栏内的微囊藻毒素的平均浓度(0.52 μg L-1)也远低于围栏外(0.82 μg L-1),但都没有达到显著差异。围栏内的周年的平均叶绿素a浓度为43.73 μg L-1,低于围栏外的48.06 μg L-1,周年围栏内外的叶绿素a含量也没有表现出显著差异。围栏是个开放的系统,当前的放养密度(7月为40 g m-3)似乎太低以至于不能使这些指标在围栏内外达到显著差异水平。 我们比较了2004年和2005年不同放养密度的情况下鲢、鳙的摄食生态位宽度和二者的食物重叠情况。在2005年放养密度增加的情况下,鲢、鳙肠含物中的浮游动物的比例均比2004年均有所减少,其中鲢减少的幅度比鳙更大。鲢的摄食生态位宽度大于鳙,鲢、鳙生态位宽度的Shannon-Weaver指数在2004年平均分别为1.38和1.13,在2005年分别为1.40和1.25。鳙鱼的摄食生态位宽度和水体中的浮游甲壳动物的生物量呈显著负相关关系(P < 0.01),但是在鲢中并没有表现出相关性。鲢、鳙的饵料组成显著重叠,在密度大、竞争加剧的2005年二者的食物重叠程度均有所减小,2004年鲢、鳙的Schoener食物重叠指数平均为0.7,2005年的为0.58。鱼类的生长数据显示,2004年鲢、鳙的生长速度和肥满度指数均大于2005年。相比较而言,鲢拥有更广的食性生态位宽度,具有更强的环境适应能力,鲢的生长速度受放养密度的影响比较小。在低密度的放养情况下,鲢、鳙可能从竞争压力下释放出来从而转向摄食更多的浮游动物,而影响它们的控藻能力。 在我们采集的所有样本中,鲢的平均相对肠长为10.30±2.31,远高于鳙的5.83±0.88。鲢、鳙肠道的总长度和标准体长均表现出极显著的线性相关(P < 0.001)。在主要的生长季节(4-11月),2005年鲢的平均相对肠长为10.77,显著大于2004年的9.23(T-test,P < 0.01);鳙在2004和2005年的平均相对肠长分别为5.74和6.03,两年没有显著性的差异。鲢、鳙的相对肠长在周年中均表现出了明显的季节变化,在夏季达到最大值,冬季最小。鲢、鳙最大的相对肠长都发生在2005年的6月,分别为13.45和6.83;最小的相对肠长发生在2005年的2月,分别为6.82和4.84。在2005年,鲢的相对肠长与其肠含物中浮游动物的比例接近显著负相关(P = 0.112)。鲢、鳙肠长的变化可能是对饵料质量和摄食强度发生变化的一种适应机制。2005年1-10月鲢、鳙的肝重比指数的平均值分别为1.57%和1.91%,在大多数月份下,鳙的肝重比指数大于鲢鱼。鲢、鳙的肝体比指数均呈现出明显的季节变化,二者的最大的肝体比指数都发生在3月,分别为2.16%和3.48%;最小肝体比指数都发生在8月,分别为1.16%和0.96%。鲢、鳙的肝体比指数与其肠含物中浮游动物所占的比例之间均呈正相关关系,其中鲢的接近显著相关水平(R = 0.589,P = 0.073),鳙的达到显著正相关(R = 0.652,P < 0.05)。生物个体的形态特征与其所利用的资源环境有非常紧密的联系。研究结果发现,鲢、鳙的一些器官形态会随着环境的变化而出现快速的适应性的调整。 我们还运用相关性分析和典型对应分析研究了2004年和2005年春末夏初太湖梅梁湾浮游植物季节演替的控制因子。春末夏初的梅梁湾水域内,蓝藻(主要是微囊藻)迅速的取代绿藻(主要是丝藻)成为水体的优势浮游植物;同时浮游甲壳动物也由大中型种类占优势变成小型占优势。分析表明:浮游植物种群的动态变化主要受非生物的理化因子影响,影响率最大的理化因子依次为温度、硝态氮、透明度、氨氮和亚硝氮;浮游甲壳动物种群结构对浮游植物群落动态变化的影响较小,其中最有影响力的种类依次为窄腹中剑水蚤、角突网纹溞和象鼻溞。研究认为,春末夏初太湖梅梁湾的浮游植物群落的季节演替主要是由温度和上行作用(主要是氮营养盐)的变化所推动,该水体中的浮游动物对浮游植物的下行作用比较弱。
Other AbstractCyanobacterial blooms are causing severe problems in many lakes and reserviors due to increasing eutrophication in recent years. Bio-control of algae through introduction of filter-feeding fish (such as silver carp Hypophthalmichthys molitrix and bighead carp Aristichthys nobilis) has been one of the most environmentally sound management propositions recently. This biomanipulation strategy is effective especially under eutrophic or hypertrophic conditions where phytoplankton community is dominated by colonial species and zooplankton community is dominated by microzooplankton. In China, silver and bighead carps are being used or tested in many lakes such as Lake Dianchi in Yunnan Province, Lake Chaohu in Anhui Province, and Lake Taihu in Jiangsu Province for the control of cyanobacterial blooms. In this thesis, we studied not only the feeding habits of silver and bighead carps which were stocked in large fish pens for the control of cyanobacterial blooms but also the impact of silver and bighead carp on the plankton communities and water quality. In addition, the controlling factors of spring-summer phytoplankton succession were also evaluated in Meiliang Bay, Lake Taihu. The main results and conclusions are as follows. The pen-cultured silver and bighead carp all displayed fast growth. In 2005, the average growth rates of silver and bighead carps were 3.18g day-1 and 4.05g day-1, respectively. The maximum daily increments of the body weight of silver and bighead carps were 8.14g in June – July, and 10.5g in May – June, respectively. The survival rates of silver and bighead carp were estimated to be 26.5% and 41.6%, respectively. Silver carp fed mainly on phytoplankton but bighead carp mainly on zooplankton. Throughout the year, phytoplankton were predominant in the gut contents of silver carp, and the average biomass contribution was 68.5% with a range of 26.4% - 91.6%; however, zooplankton were predominant in the gut contents of bighead carp, and the average biomass contribution was 64.7% with a range of 15.4% - 98.4%, except in July and August when the gut contents of bighead carp were also dominated by phytoplankton. There was an obvious feeding rhythm in silver and bighead carps. From July to October, feeding activity was most active between 14:00-18:00 h while the least between 06:00-10:00 h. However, in May, we observed a reversed feeding rhythm with a feeding peak at 06:00. Our results suggest that dominant plankton species in the lake water might be another important factor affecting feeding rhythm of silver and bighead carps. The feeding intensity of silver carp was significantly stronger than bighead carp in every month (P < 0.1). Silver carp had the highest mean gut fullness rate in August (8.12%), while bighead carp was in September (4.87%). Daily rations of silver and bighead carp were estimated by Egger’ model in the main growing season. The average daily ration was 13.62% for silver carp and 6.79% for bighead carp. Filtration rate was calculated from the daily ration and the density of plankton in the lake. During May - October, mean filtration rate of silver and bighead carp for phytoplankton were 0.73 L g-1 h-1 and 0.31 L g-1 h-1, respectively, and mean filtration rates for zooplankton were 0.32 L g-1 h-1 and 0.76 L g-1 h-1, respectively. Silver carp had a stronger ability of eliminating phytoplankton than bighead carp. To achieve a successful biomanipulation with a minimum effect of ichthyoeutrophication, the stocking proportion of bighead carp should be controlled in the future practice. In 2005, the mean values of nutrient concentrations were generally higher in the fish pens than in the surrounding lake. However, no physicochemical parameters were significantly different between the fish pens and the surrounding lake (P > 0.1) except for pH (P = 0.08). Annual mean biomass of crustacean zooplankton was significantly higher in the surrounding lake (2.39mg L-1) than in the pens (1.83 mg L-1) (T-test, P < 0.05). Biomass of cladocerans was significantly higher in the surrounding lake (1.86 mg L-1) than in the fish pens (1.26 mg L-1) (T-test, P < 0.05). The copepods/cladocerans ratio was always higher in the fish pens than in the surrounding lake, but the difference was not significant (P > 0.1). Total phytoplankton biomass, Microcystis biomass and microcystin concentration were lower in the fish pens than in the surrounding lake water, but the difference was not statistically significant. Annual total biomass of phytoplankton was 8.39 mg L-1 in the fish pens and 9.74 mg L-1 in the surrounding lake. Annual mean chlorophyll a concentration was lower in the fish pens (43.73 µg L-1) than in the surrounding lake (48.06 µg L-1), but the difference was also not statistically significant. In the present study, the stocking density of silver plus bighead carp (about 40 g m-3 in July) was likely too low to achieve a significant difference in the above parameters between in the fish pens and in the surrounding lake. In the main growth season (from April to November), we evaluated the diet niche breadth, diet overlap and growth of silver and bighead carp in 2004 with a low stocking density and in 2005 with a high stocking density. Both carps predated more zooplankton in 2004 than in 2005. Diet breadth index (Shannon-Weaver index) of silver and bighead carp was 1.38 and 1.13 in 2004, 1.40 and 1.25 in 2005, respectively. Silver carp had a broader diet breadth than bighead carp. Diet breadth of bighead carp was significantly correlated with abundance of crustacean zooplankton (p < 0.01), but such correlation was not significant for silver carp. Diet overlap estimated by Schoener’s similarity index was relatively high between silver and bighead carp. Their diet overlap obviously declined in 2005, with an average value of 0.7 in 2004 and 0.58 in 2005. Higher stocking density increased the diet breadth but decreased diet overlap in both carps. In addition, growth rates of silver and bighead carps were also significantly lower in 2005 than in 2004. It appears that silver and bighead carp were released from diet competition and shifted to feed on more zooplankton at low density, decreasing the efficiency of controlling cyanobacterial blooms. In the present study, the average relative gut length was 10.30±2.31 for silver carp and 5.83±0.88 for bighead carp. There were significant correlations between gut length and standard body length for silver and bighead carp (P < 0.001). In the main growth seasons, silver carp significantly increased their relative gut length when feeding on more phytoplankton in 2005 (p < 0.01, 9.23 in 2004 and 10.77 in 2005, respectively); the relative gut length of bighead carp was 5.74 in 2004 and 6.03 in 2005, respectively. There was a nearly significant negative correlation between zooplankton proportion in the diet and the relative gut length when silver carp were stocked in a high density in 2005 (p = 0.112). Such resource polymorphisms in gut may be a good indication of temporal adaptation to resource conditions. During January to October in 2005, the hepato-somatic index of silver and bighead carp was 1.16% and 0.96%, respectively. There were significant correlations between the hepato-somatic index of silver and bighead carp and the zooplankton proportion in their gut contents (P = 0.073 for silver carp, P < 0.05 for bighead carp). Environmental variation can induce dramatic changes in the traits of organisms. Our results provided a field evidence for understanding the functional basis of resource polymorphisms and the evolution of phenotypic plasticity in planktivorous filter-feeding fishes. During May to July in 2004 and 2005, the spring-summer successions of phytoplankton and crustacean zooplankton were weekly examined in Meiliang Bay, Lake Taihu. During the study period, the ecosystem of Meiliang Bay was characterized by (i) clearly declined nitrogen compounds (nitrate, TN and ammonium) and slowly increased phosphorus compounds (TP and SRP), (ii) increased total phytoplankton density and rapid replacement of chlorophyta (mainly Ulothrix) by cyanobacteria (mainly Microcystis), and (iii) rapid replacement of large-sized crustaceans (Daphnia and Moina) by small-sized ones (Bosmina, Limnoithona and Ceriodaphnia). Results from CCA and correlation analysis indicate that the spring-summer phytoplankton succession was primarily controlled by abiotic factors. Cyanobacteria were mainly promoted by increased temperature and decreased concentrations of nitrogen compounds. The pure contribution of crustacean was low for the variation of phytoplankton suggesting a weak top-down control by crustacean zooplankton in the subtropical Lake Taihu.
Pages148
Language中文
Document Type学位论文
Identifierhttp://ir.ihb.ac.cn/handle/342005/12252
Collection学位论文
Recommended Citation
GB/T 7714
柯志新. 太湖梅梁湾生物控藻围栏内鲢、鳙摄食生态和控藻效果的研究[D]. 水生生物研究所. 中国科学院水生生物研究所,2008.
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