Habitat use by fishes after tidal reconnection of an impounded estuarine wetland in the Indian River Lagoon,Florida (USA)

Most of the wetlands located along the Indian River Lagoon (IRL) ineast-central Florida (USA) have been impounded since the 1950's and1960's to reduce mosquito reproduction. Impounded marsh (i.e.,impoundment) dikes physically separate the wetlands from the estuary toallow artificial flooding of the impoundments during the mosquito breedingperiod (May to October). Presently, Rotational ImpoundmentManagement (RIM) is the preferred impoundment management techniquein the IRL. Impoundments maintained under RIM have culverts installedthrough the dikes which are kept closed during the mosquito breedingseason (to control mosquitos) and are allowed to remain open for theremainder of the year (to allow tidal flow). A 24.3 ha impoundment8 km north of Sebastian Inlet that had been isolated from the IRL for over39 years was studied for 12 months to determine habitat use by fishes aftertidal reconnection and the implementation of RIM. Fish sampling wasconducted with a seine in the perimeter ditch and with clover and minnowtraps in the upper marsh and tidal creek areas of the impoundment. Waterlevel, impoundment bottom topography, and the seasonal nursery functionof the impoundment were factors that contributed to observed patterns offish habitat use during the study. Within the first 15 weeks of perimeterditch sampling, an increase from 9 to 40 species was observed. Transientspecies used the perimeter ditch almost exclusively and entered theimpoundment primarily during the spring open period. Juvenile Pogonias cromis (Linnaeus), Elops saurus Linnaeus, Centropomusundecimalis (Bloch), and Megalops atlanticus Valenciennes were themost abundant recreationally important species, respectively. Habitat useby the most abundant resident species (Gambusia holbrooki Girard,Poecilia latipinna (Lesueur), Cyprinodon variegatus Lacepède, andFundulus confluentus Goode & Bean) was influenced primarily bywater level fluctuations. Resident species used the upper marsh and tidalcreek habitats during summer flooded periods and the cyprinodontids leftthe interior surface of the impoundment last as water levels decreased. Thisstudy is the first to document the recovery of fish populations in areconnected impoundment north of Sebastian Inlet using both active andpassive sampling techniques.     

Influences of low-head dams on the fish assemblages in the headwater streams of the Qingyi watershed, China

The influences of low-head dams on the fish assemblages were examined in this study, using fish data collected in six treatment and five reference sites at three low-head dams in the headwater streams of the Qingyi watershed, China. Comparing with those in the reference sites, local habitat variables were significantly altered by low-head dams in the treatment sites, involving wider channel (only in the impoundment area), deeper water and slower flow. Fish species richness varied significantly across seasons, not across site categories, suggesting that these low-head dams did not alter species richness. However, significant decreases in fish abundance and density were observed in the impoundment areas immediately upstream of dams, but not in the plunge areas downstream. Fish assemblage structures kept relative stability across seasons, and their significant difference between-site was only observed between the impoundment areas and the sites far from dams upstream. This variation in assemblage structures was due to the differing relative abundance of some co-occurring species; more lentic but less lotic fish was observed in the impoundment areas. The spatial and temporal patterns of fish assemblages were correlated with local habitat in this study area. Wetted width had negative correlation with fish species richness, abundance and density, respectively. Water temperature also positively affected species richness. In addition, wetted width, water depth, current velocity and substrate were the important habitat variables influencing assemblage structures. Our results suggested that, by modifying local habitat characteristics, low-head dams altered fish abundance and density in the impoundment areas immediately upstream of dam, not in the plunge areas immediately downstream, and thereby influenced fish assemblage structures in these stream segments.     

三峡库区不同水文类型支流大型底栖动物对蓄水的响应

为探究三峡水库修建对库区不同水文类型支流大型底栖动物的影响,于2015年7月和2016年1月对三峡水库四条支流的大型底栖动物进行调研,分别对周期性受蓄水影响支流的非回水区与回水区和长期受蓄水影响支流的非回水区与回水区大型底栖动物群落结构进行比较研究,结果表明:⑴7月份三峡水库145米低水位时期共采集到底栖动物655头计59种(属),在受蓄水影响河段采集到底栖动物4种共40头,优势种为日本沼虾(占受蓄水影响区域的57.5%); 1月份三峡水库175米蓄水时期共采集到底栖动物1123头计69种(属),在受蓄水影响河段采集到16种238头,优势种为锯齿新米虾(占受蓄水影响区域的14.2%)。⑵周期性受蓄水影响支流的非回水区与回水区底栖动物密度、生物量和多样性指数无显著差异(P0.05);长期受蓄水影响支流的非回水区与回水区之间底栖动物密度和Pielou均匀度指数无显著差异(P0.05),但非回水区底栖动物生物量显著高于回水区(P0.05),底栖动物多样性和丰富度极显著高于回水区(P0.01)。⑶7月份影响底栖动物分布的主要环境因子共6个,分别是水深、流速、硝态氮、溶解氧、水温和电导率; 1月份影响底栖动物分布的主要环境因子共7个,分别是水温、溶解氧、总磷、流速、深度、电导率和透明度。     

Distribution and abundance of blackflies (Diptera: Simuliidae) in relation to impoundments in the Buffalo River, eastern Cape, South Africa

1. The abundance of blackfly species along the length (140 km) of the multiply impounded Buffalo River, eastern Cape, South Africa, was studied between 1986 and 1988. 2. Twenty-three species of blackflies were recorded, most of which (95%) were usually found 5–10 km from the source. 3. Impoundments favoured five lower-reach (pest) blackfly species at the expense of two upper-reach (non-pest) species. Impoundments have therefore shifted the distribution of blackfly species ‘upstream’, and have increased the distribution of pest blackflies. 4. The smallest impoundment, situated in the Upper Foothill Stony Run Zone, had the greatest effect on blackfly distribution. 5. There was no typical filter-feeding guild below impoundments. Possible reasons for this included the discharge of toxic algae from impoundments, the lack of compensatory releases, the sudden drying of impoundment tailwaters and the paucity of natural lakes in southern Africa which precludes a pre-adapted ‘outlet’ fauna.     

Colonization and succession of benthic macroinvertebrates in Arcadia Lake,a South-Central USA reservoir

Colonization and succession of benthic macroinvertebrates in Arcadia Lake, an urban reservoir, were studied for four years. Physicochemical conditions including water temperature, dissolved oxygen concentrations, pH, specific conductance, and Secchi disc depth were also recorded. Colonization of the reservoir occured fairly rapidly through a sequence of three invasions. The first, and most significant, colonists were primarily facultative species already present in streams and ponds that were inundated by the impoundment. Later arrivals tended to be limnophilic species that probably came from other bodies of water. Of 30 species encountered in a pre-impoundment collection, only six were still present three years following impoundment. Thirty-three additional benthic macroinvertebrates species invaded the area following impoundment. Dominant taxa in the reservoir included Dero nivea, Limnodrilus sp., Chaoborus punctipennis, Chironomus sp., and Procladius sp. Pollutants accumulating in this urban reservoir, including metals and pesticides, and siltation probably have kept benthic populations relatively low and possibly reduced potential species diversity.     

Food consumption by fish populations in the Warta River,Poland, before and after impoundment

The impact of impoundment on the energy budget and gross ecological efficiency (K ₁) of fish populations in sites upstream from the backwater (AB) and downstream of the dam (CD) of a manmade reservoir (17.6 km²) located in the middle reaches of the lowland Warta River (808 km long), was investigated.Consumption (MJ ha^–1 yr^-1) in four years following the reservoir's impoundment was 34–74% lower in site AB, and 43–75% in site CD than before the impoundment. K ₁ of investigated species was higher before the impoundment and only pike exhibited an inverse efficiency trend. Significant differences were also observed in the diet of certain dominant fish species, which resulted from a change in the food supply as well as a reduction in their life span after the river was dammed.     

Food and feeding of the mormyrid fishes of Lake Kainji, Nigeria, with special reference to seasonal variation and interspecific differences

The feeding habits of mormyrids from Lake Kainji, Nigeria, are discussed in relation to the decreased abundance of these fish since impoundment in 1968. Evidence is presented of both intra-specific seasonal variation in diet and inter-specific trophic divergence. These variable factors are discussed in relation to the degree of success achieved by certain species in the lake.     

水位节律差异对三峡水库消落区不同物候类型1年生植物物种构成的影响

三峡水库蓄水后改变了原有长江自然的水位波动节律,并在三峡库区内形成了两种类型的消落区:蓄水前未经历过水淹的完全水库消落区,其水位节律夏低冬高;以及蓄水前属于自然消落区目前受蓄水和洪汛双重影响的消落区,其水位在冬季和夏季都存在高水位。这与自然消落区冬低夏高的水位节律均存在差别。1年生植物根据萌发结实特性可分为春萌秋实、冬萌夏实型植物和广适性植物3类。在不同消落区选取5个样地划分样带设置固定样方,涨水前和退水后调查发现:各消落区均存在3种1年生植物,但3种类型物种的比例和和优势度存在显著差异。只受夏季洪汛影响的自然消落区共发现1年生植物73种,冬萌夏实型植物以45种占优;而水位节律与之相反的完全水库消落区,1年生植物物种数为85种,其中春萌秋实型植物以45种以及较大的优势度成为该区域的优势1年生物种;双重影响消落区,1年生植物物种总数未明显下降,但是在蓄水和洪汛的双重影响下其种群大小相对较低。水位节律的巨大变化会引起1年生植物优势类型的显著改变,适合生长的1年生植物主要是因为其生长周期与淹没期不完全重叠而成为优势物种类型。     

Assessing the effect of the Three Gorges reservoir impoundment on spawning habitat suitability of Chinese sturgeon (Acipenser sinensis) in Yangtze River,China

The Chinese sturgeon (Acipenser sinensis), a kind of maricolous anadromous migratory fish species, is endangered and protected in China. Historical spawning habitats were distributed in the lower reaches of Jinsha River and the upper reaches of Yangtze River. Since the establishment of the Gezhouba water conservancy pivot in 1981, the migratory route of Chinese sturgeon spawning was blocked. Therefore, the fish was forced to propagate in a new spawning ground which was mainly distributed in the 4-km-long mainstream from Gezhouba Dam to Miaozui in the middle Yangtze River. After water storage and power generation of the Three Gorges reservoir (TGR) in 2003, the propagation of Chinese sturgeon has been impacted gradually. According to field surveys, the fish used to spawn twice a year before TGR impoundment, but only once happened after that. Besides, the spawning scale is also declining with each passing year.In order to simulate and evaluate the effect of TGR impoundment on spawning habitats of Chinese sturgeon, with consideration of their reproductive characteristics, an eco-hydrodynamic model was established by coupling a two-dimensional hydrodynamic model and a fuzzy fish habitat module based on fuzzy logic inference. Flow fields at the studied site in an impoundment scenario and an assumed no impoundment scenario were simulated with the 2D hydrodynamic model. Afterwards, by linking hydrodynamic conditions to the expert knowledge base, the fuzzy habitat model used fuzzy logic inference to compute habitat suitability of the Chinese sturgeon. In addition, the approach was used to propose a suitable instream flow range during the propagation period for Chinese sturgeon. The results indicated that the suitable instream flow needed for Chinese sturgeon spawning in middle Yangtze River should be between 10,000 m³/s and 17,000 m³/s and it also showed that after TGR was put into pilot impoundment operation at the designed water level of 175 m, the habitat suitability has decreased significantly in October. Besides, the water temperature of spawning habitat increased to a higher level in propagation period due to the impoundment of the TGR. All these alterations have had imposed tremendous impacts on the propagation of Chinese sturgeon. Therefore, adjusting impoundment schedule of the TGR to recover the water flow over spawning habitat in October is a crucial way to improve the habitat suitability. Furthermore, the presented method also provides a theoretical basis for further research on the assessment of habitat suitability of aquatic species at a micro-habitat scale.     

The effects of impoundment and regulation upon the stomach contents of fish at Cow Green, Upper Teesdale

The stomach contents of 1003 brown trout, 1551 bullheads and 800 minnows taken from the reservoir basin and below the dam, before and after impoundment of the river Tees, were examined. Their composition reflected observations by other workers on river and reservoir benthos, except for the increase in numbers of Hydra and Nais below the dam, and Mollusca, Hirudinea and oligochaetes in the reservoir.
Trout below the dam ate more Ephemeroptera nymphs and Chironomidae larvae but fewer terrestrial casualties after river regulation, whereas bullheads ate more Mollusca but fewer Plecoptera nymphs. In both species Baetidae nymphs increased in numerical importance relative to Ecdyonuridae. Trout, but not bullheads, took zooplankton discharged from the reservoir.
Before impoundment, trout within the reservoir basin ate chiefly benthic organisms and terrestrial casualties. Inundated terrestrial material, mainly earthworms, formed the bulk of their food for at least three years after impoundment, whilst from the second year onwards Chironomidae and, in some years, Gammarus became increasingly important. Zooplankton was taken by all sizes of reservoir trout.
Bullheads within the reservoir basin ate chiefly river benthos before impoundment, with Ephemeroptera and Plecoptera nymphs predominant in older fish, and aquatic Diptera and Coleoptera also important in the fry. After impoundment, Chironomidae and Gammarus were the main items taken by older bullheads, and Chironomidae and micro-crustacea by the fry. Among all sizes of minnow, Chironomidae, micro-crustacea and detritus increased in numerical importance after impoundment.     

The plankton community of an acid blackwater South Carolina power plant impoundment

Robinson Impoundment, an acid blackwater system in the South Carolina sandhills, serves as a cooling pond for a 854 MW power plant. It is divided by a causeway into an upper and lower impoundment. The upper impoundment is narrow, shallow, exhibits higher flow, and much more periphytic and rooted aquatic macrophyte vegetation. The lower impoundment is wide and deep with many sandy shoreline areas and little macrophyte vegetation.The zooplankton and phytoplankton communities of both the lower and upper impoundment were investigated over a three-year period (1980–1982) in an effort to determine power plant discharge effects on the plankton. Primary productivity rates were low, characteristic of an oligotrophic system. The phytoplankton community was dominated by the Bacillariophyceae and Chlorophyceae in cell density and the Chlorophyceae in species richness. The zooplankton community was dominated numerically by copepods, rotifers, and cladocerans, respectively. Principal zooplankton species includedDiaptomus mississippiensis, Bosmina longirostris, Diaphanosoma brachyurum, Keratella americana, K. cochlearis, Pompholyx sulcata, andConochiloides coenobasis. The rotifers were dominant in species richness, while crustacean zooplankton species richness was usually quite low. Statistical analyses performed using phytoplankton and zooplankton population variables indicated that in most cases upper impoundment densities were significantly lower (p < 0.05) than lower impoundment densities which were likely a function of the lotic upper impoundment habitat. No significant differences were found between the discharge area and the rest of the lower impoundment stations suggesting that localized power plant discharge effects did not occur during the study. Peak midsummer thermal discharge (36.0 ° C) may have caused temporary reductions inD. mississippiensis and several rotifers. Thermal stimulation during summer may have caused population increases for the filter-feeding cladocerans,B. longirostris andD. brachyurum.     

三峡水库坝前段蓄水前后枝角类的周年变化

三峡水库蓄水前后,作者从2002年6月至2004年7月按月在坝前段(茅坪—归州)采集枝角类,研究蓄水前后枝角类的变化,结果显示蓄水前该江段水流急不适合枝角类栖息,仅在水流相对较缓的岸边采集到2种;蓄水后水环境较适宜枝角类生活,周年内共采集到20种,并存在着明显的季节变化和水平分布上的差异,文中对其原因进行了分析讨论。       

Upstream effects of a reservoir on fish assemblages 45 years following impoundment

Fish assemblage structure, rarefied species richness, species diversity and evenness of assemblages upstream of a reservoir in Oklahoma, U.S.A., were compared pre and post‐impoundment as well as in contemporary collections from streams above and below the reservoir. There were significant shifts in assemblage structure between historical and contemporary collections above the reservoir but not between contemporary assemblages above and below the impoundment. Indicator species analysis revealed that the sand shiner Notropis stramineus and fathead minnow Pimephales promelas have declined, whereas largemouth bass Micropterus salmoides and western mosquitofish Gambusia affinis have increased in relative abundance in assemblages upstream of the impoundment. Species richness was lower in contemporary assemblages compared with historical assemblages. Furthermore, contemporary assemblages below the dam had lower species richness, diversity and evenness compared with contemporary collections above the dam. These results highlight the spatial and temporal extent of reservoirs altering fish assemblages upstream of impoundments.     

三峡成库后香溪河库湾底栖动物群落演变及库湾纵向分区格局动态

水库生态系统演替是水库生态学研究及水库管理过程中都比较关注的问题。三峡水库自2003年6月成库以来,有关水库生态系统演替的研究却鲜见报道。以三峡水库香溪河库湾底栖动物为研究对象,分析了自2003年8月—2010年7月3个不同蓄水阶段底栖动物群落的演变状况,并对库湾纵向分区格局的动态变化进行了探讨。结果表明,水库蓄水后,摇蚊科和颤蚓科成为第一批定殖者,并以摇蚊科为主;随后,颤蚓科中的霍甫水丝蚓逐渐成为优势类群;直到2004年4月仙女虫科的肥满仙女虫与霍甫水丝蚓共同主导群落。一期蓄水后约1a,底栖动物密度和物种数呈现出明显的增长趋势,空间上呈现出"中间高、两头低"的格局。库湾总体密度于2006年4月达到最高值,高达24146个/m2。二期蓄水导致底栖动物总密度显著降低,而三期蓄水后则变化相对较小。随着时间的增长,库湾底栖动物偶见种出现的频率逐渐降低,群落逐渐趋于稳定。基于TWINSPAN(two-way indicator species analysis)的分析,一期蓄水后期,香溪河库湾纵向上底栖动物群落结构呈现出稳定的分区格局,库湾中部区域呈现出相同的群落类型,无季节变化;而自二期蓄水开始,库湾纵向上大部分样点的群落类型发生改变,表明二期蓄水的干扰较强;之后呈现出季节性波动,此种格局与水位的季节波动相关联,表明三峡水库底栖动物逐渐适应水库周期性的调度,群落结构呈现稳定的季节性周期波动。     

Effects of impoundment on populations of bullhead Cottus gobio L. and minnow, Phoxinus phoxinus (L.), in the basin of Cow Green Reservoir

The distribution, growth and reproduction of bullhead, Cottus gobio , L., and minnow, Phoxinus phoxinus (L.), were studied at Cow Green Reservoir, Upper Teesdale, for 10 years following impoundment in 1970. Comparisons were made with pre-impoundment results. The length-for-age of bullheads increased after impoundment. The length-for-age of minnows decreased. In winter both species were confined mainly to deep water or to the stone facing of the earth dam. In summer they were found throughout the reservoir though bullheads were scarce in the littoral zone. Female bullheads became sexually mature at an earlier age (84% at age-group I) than before impoundment (33% at age-group I) but no change was apparent amongst males (67–62% in age-group I). The post-impoundment sex ratio did not differ from 1:1 and individual fecundity did not change after impoundment. There was a significant reduction in individual fecundity of the minnow. The mean instantaneous rate of mortality ( Z ) for bullhead of age-groups II to IV was 0.96 ± 0.34 year⁻¹, compared with 0.85 ± 0.29 year in the Tees before impoundment.     

Fish species composition before and after construction of a main stem reservoir on the White River,Colorado

Synopsis The completion in the fall of 1984 of Taylor Draw Dam on the White River, Colorado, formed Kenney Reservoir — thus impounding the last significant free-flowing tributary in the Upper Colorado River Basin. Fishes were sampled above and below the dam axis prior to closure of the dam and in the reservoir and river downstream following impoundment. While immediate effects of the dam to the ichthyofauna included blockage of upstream migration to 80 km of documented range for endangered Colorado squawfish, the reservoir also proved to have profound delayed effects on the river's species composition. Pre-impoundment investigations in 1983–1984 showed strong domination by native species above, within, and below the reservoir basin. By 1989–1990, non-native species comprised roughly 90% of the fishes collected in the reservoir and 80% of the fishes collected in the river below the dam. Initially, fathead minnow, whose numbers quickly increased in the new reservoir, dominated all post-impoundment collections, but red shiner became the most abundant fish collected in the river below the dam by 1989–1990. While agency stocking programs for the reservoir sought to emphasize a sport fishery for salmonids, primarily rainbow trout, local enthusiasm for warmwater sport fishes resulted in illicit transfers of these species from nearby impoundments. Several species, formerly rare or unreported in the White River in Colorado, including white sucker, northern pike, green sunfish, bluegill, largemouth bass and black crappie, were present in the river following impoundment. Our investigation indicates smaller-scale, main-stem impoundments that do not radically alter hydrologic or thermal regimes can still have a profound influence on native ichthyofauna by facilitating establishment and proliferation of nonnative species.Cooperators are the U.S. Fish and Wildlife, the Colorado Division of Wildlife, and Colorado State University     

Australian lungfish, <Emphasis Type="Italic">Neoceratodus forsteri</Emphasis>, threatened by a new dam

The Australian lungfish, Neoceratodus forsteri, exists as remnant natural populations in two rivers of south-east Queensland, Australia, and several translocated populations. Lungfish habitats have been impacted by agriculture and forestry, alien plants and fish and by river impoundment and regulation of flows. The species has been listed as vulnerable under Australian Commonwealth legislation. A proposal to construct Traveston Crossing Dam on the free-flowing main channel of the upper Mary River could seriously threaten the lungfish. The dam can be stopped by Commonwealth legislation if important populations of lungfish in the Mary River are likely to be significantly impacted by the new dam. This paper assembles evidence that impoundment of the Mary River and regulation of river flows are likely to decrease and fragment important lungfish populations, disrupt the breeding cycle, reduce juvenile recruitment, and isolate and decrease habitat availability/quality to such an extent that the species is likely to decline. Proposed mitigation strategies include fish transfer facilities, provision of flow releases from the dam (environmental flows) to sustain lungfish habitat and breeding downstream, and translocation of hatchery-reared juvenile lungfish into suitable natural habitats. These mitigation efforts may not be sufficient to secure the genetic diversity and long-term viability of lungfish populations in the Mary River.     

Zooplankton Communities of a Dammed Estuary in the Bay of Fundy,Canada

The upper estuary of the macrotidal Petitcodiac River, New Brunswick, Canada, was converted to a freshwater impoundment by construction of a causeway in 1968. Thirty years later, zooplankton community structure in the impoundment was characteristic of a disturbed ecosystem. The depauperate zooplankton consisted of a mixture of freshwater and marine/brackish taxa, but was not typical of regional estuaries or lakes. The causeway dam was an obstacle to fish migration, and several anadromous species that would formerly have been represented in the ichthyoplankton were absent. The invertebrate plankton community was dominated by rotifers, likely as a result of frequent water level fluctuations, and highly suspended sediment levels in the water column. Estuarine/marine calanoids (Eurytemora affinis, Temora longicornis, Centropages typicus, Tortanus discaudatus), the mysid Neomysis americana, and Cancer crab zoeae were collected in fresh water up to 14 km upstream of the causeway.     

二滩水电站水库形成后鱼类种类组成的演变

本文对二滩水库建成前后,雅砻江下游长约380km河段的鱼类种类结构、生态类群及相对资源量的变化进行了研究。结果表明水库建成后不同区段的鱼类种类结构发生了变化,喜栖静水和缓流环境的种类逐渐在库区占主导地位,适应急流环境的种类主要分布于库尾和支流等局部水域中,一些外来种已经定居并在某些水域形成了优势种群。在水库建成后的头几年,由于鱼类种群密度增加还导致了渔业捕捞量大幅度上升。针对上述变化,结合雅砻江梯级电站建设可能带来的进一步环境改变,作者提出了建立自然保护江段、开展人工繁殖放流、进行水库生态调度以及防止外来种入侵等措施和建议。