Assemblage patterns of fish functional groups relative to habitat connectivity and conditions in floodplain lakes

Miyazono S, Aycock JN, Miranda LE, Tietjen TE. Assemblage patterns of fish functional groups relative to habitat connectivity and conditions in floodplain lakes.
Ecology of Freshwater Fish 2010: 19: 578–585. © 2010 John Wiley & Sons A/S Abstract – We evaluated the influences of habitat connectivity and local environmental factors on the distribution and abundance patterns of fish functional groups in 17 floodplain lakes in the Yazoo River Basin, USA. The results of univariate and multivariate analyses showed that species–environmental relationships varied with the functional groups. Species richness and assemblage structure of periodic strategists showed strong and positive correlations with habitat connectivity. Densities of most equilibrium and opportunistic strategists decreased with habitat connectivity. Densities of certain equilibrium and opportunistic strategists increased with turbidity. Forested wetlands around the lakes were positively related to the densities of periodic and equilibrium strategists. These results suggest that decreases in habitat connectivity, forested wetland buffers and water quality resulting from environmental manipulations may cause local extinction of certain fish taxa and accelerate the dominance of tolerant fishes in floodplain lakes.     

Spatial and temporal patterns in fish community structure and abundance in the largest U.S. river swamp,the Atchafalaya River floodplain,Louisiana

Long‐term monitoring is critical for documenting population and community trends and for management, especially in large river‐floodplain ecosystems that provide important services. Levees have reduced active floodplains in most large rivers, but connectivity in some reaches could promote community resilience. Using multivariate tools and regression, we examined spatial and temporal structure in fish community samples from two decades (>1000 samples, >100 sites) in one of the largest relatively intact river‐floodplain ecosystems in North America – the Atchafalaya River (ARB), Louisiana. Assemblages exhibited significant structure temporally and spatially, with most substantial effects of year and hydrologic subdivisions; however, season and water level also influenced community structure. Temporal trends in communities were limited to few areas, while declines in species richness were more widespread; however, rarefied richness trends suggested that declines were slight. Recent and long‐term declines in abundance of economically important species (e.g., Black Crappie, Largemouth Bass, Bigmouth Buffalo) and increases in others (e.g., Smallmouth Buffalo, Blue Catfish, Freshwater Drum) drove differences among time periods. Our results suggest that the hydrologic subdivisions of the ARB may be an appropriate scale at which to manage fish populations, hydrology and water quality. Although we could not account for several important factors affecting fish communities in the ARB (e.g., hurricanes, major floods), and were limited by sampling variability, our findings highlight the utility of long‐term datasets from large river‐floodplain ecosystems for identifying important scales for management, determining species contributions to community change and forming hypotheses about anthropogenic and environmental drivers of variation in fish communities.     

Trophic Ecology of Arapaima sp. in a ria lake—river–floodplain transition zone of the Amazon

Neotropical floodplains are usually productive systems that are maintained by the nutrient, detritus and sediment inputs provided by the main river channel flood pulse. Ria lakes represent a special feature and habitat in the Amazonian floodplains, being characterised by a dendritic morphology and dependence on terrestrial inputs provided by an intricate stream network. Our objective was to evaluate the trophic ecology of the arapaima (Arapaima sp.). We combined stomach content analysis with measurements of carbon and nitrogen stable isotope values from dorsal muscle to infer the ontogenetic changes in trophic level and isotopic niche width in floodplain and ria lakes. Arapaima diet was dominated by fish from low trophic positions. While most of the stomachs sampled in the study ria lake were full, empty stomachs predominated in samples taken in the floodplain lakes. These differences indicate that ria lakes may provide better feeding grounds for arapaima during the dry season, presumably because ria lakes are interconnected with a large stream network and the main river channel year round. Nitrogen stable isotope results further indicated an ontogenetic dietary shift in arapaima, with piscivory increasing as a function of length in both environments. Carbon stable isotope analysis indicated that energy sources used by arapaima varied by environment, with arapaima using a greater diversity of food sources in ria lakes than in floodplain lakes. Information about the main carbon sources is useful for fishery management because stakeholders may choose to conserve key vegetal groups to ensure the productivity and diversity of aquatic ecosystems.     

Seasonality of energy sources of Colossoma macropomum in a floodplain lake in the Amazon – lake Camaleão, Amazonas, Brazil

Abstract  Stomach content and stable isotopes of tambaqui, Colossoma macropomum (Cuvier), were use to determine seasonality of energy sources in a floodplain lake in the central Amazon. The turnover time of carbon in young tambaqui was fast enough to detect a broad seasonal variation both in stomach content and tissue isotopic signal of carbon and nitrogen. The relative importance of food items varied with water level. C₃ plants (seeds and fruits) contributed between 55% and 95% of the biomass fraction of tambaqui. Zooplankton contributed a minimum of 26% of the nitrogen fraction during periods of flooding, and a maximum of 67% in the dry season. C₄ plants (macrophyte leaves and roots) contributed a maximum of 26% of the biomass fraction and 13% of the N fraction mainly during the flooding period. The feeding habits and behaviour of tambaqui are complex and linked to the flood pulse.     

Identifying potential causes of fish declines through local ecological knowledge of fishers in the Ganga River,eastern Bihar,India

Local ecological knowledge (LEK) can offer insights into fisheries management by describing long‐term changes that are difficult to unravel in data‐poor river‐floodplain fisheries. LEK is derived from complex interactions between fishers’ observations of environmental change and their institutional capacities to manage fisheries. Hence, it is important to understand where and how LEK and formal scientific studies on fish species’ decline could complement each other. In this paper, the causes of decline of 58 fish and two shrimp taxa were identified from LEK data (1999–2019) obtained from river–floodplain fisheries of the Gangetic plains (Bihar, India). Qualitative analyses of LEK were used to generate species‐specific hypotheses and historical insights on their declines. Destructive fishing, overfishing and the Farakka barrage were cited by fishers as the major causes of declines. Potential reasons for these perceptions were explored in relation to fishers’ experiences of conflicts in the region over fishing rights and access.     

Dynamics of floodplain fisheries in Bangladesh, results of 8 years fisheries monitoring in the Compartmentalization Pilot Project

Floodplain fisheries were monitored from 1992 until 2000 in the Compartmentalization Pilot Project in Tangail, Bangladesh. In permanent floodplains about 165 ± 28 kg ha^?1 of fish was caught annually. For seasonal floodplains, this figure was 83 ± 23 kg ha^?1 yr^?1. The fish catch exhibited a strong seasonal variation, with the highest catch in October, when the floodwater recedes towards the river, and the lowest catch during the dry season in April/May. The annual catch varied with the extent of flooding, with high catches in wet years and low catches in dry years. The extent of flooding was quantified through a Flood Index. Plotting the annual yields against this Flood Index provided a significant relation (P < 0.05), confirming the existence of a flood pulse. The fishing effort (f) and the catch‐per‐unit‐effort (CPUE) were significantly related (P < 0.05), whereby the fishing effort increased with increasing CPUE. The results are discussed within the frame of fisheries management in Bangladesh and highlight the need for long‐term data for proper evaluation of fisheries projects and the development of management schemes, and the difficulty of applying standard surplus production models in floodplain fisheries.     

The breeding biology of Clarias albopunctatus Nichols & LaMonte, 1953 in semi-intensively managed ponds in the floodplain of the River Anambra, Nigeria

Abstract— In ponds in the floodplain of the River Anambra, Nigeria, Clarias albopunctatus matured after the first year when they were 101–150 mm in total length. Gonad development was more rapid in males than in females. The breeding season lasted from March to September, and recruitment of the clariids into the artisanal fishery began from the latter month. The number of oocytes in both ovaries ranged from 1974 to 9310. Fecundity-weight relationship was linear and positively correlated: Y = 1451.64+ 77.19 x , r ²= 0.82. Spawnable oocytes, which constituted over 91% of gonad weight, ranged from 1.05 to 1.75 mm in diameter. A minor and major communal spawning involving Clarias macromystax, C. agboyiensis and C. albopunctatus took place in the inundated grassy areas of the floodplain. Migration of 4-month-old juveniles towards the main river or floodplain ponds, which appeared to be triggered by current speed in the spawning ground, occurred during the night and in groups.     

First report of white spot syndrome virus in wild crustaceans and mollusks in the Paraíba River,Brazil

The aim of the present study was to investigate the presence of white spot syndrome virus (WSSV) in the Paraíba River, Brazil. Eight sampling sites were established on the bank of the river near water intake areas for the farming of Litopenaeus vannamei. Ten specimens of the shrimp Palaemon pandaliformis and the gastropods Pomacea lineata and Melanoides tuberculatus were collected at each site. Eighty‐one gill fragments from P. pandaliformis, 40 whole individuals of M. tuberculatus and 26 muscle fragments from P. lineata were collected. All samples were stored in microcentrifuge tubes with 95% ethanol (1:10; v:v). Tests were performed at the Potiporã Molecular Analysis Laboratory (state of Rio Grande do Norte, Brazil) for the detection of WSSV using Loop Mediated Isothermal Amplification with the aid of the LAMP WSSV kit (Concepto Azul, Ecuador). Twenty‐nine per cent of P. pandaliformis, 48% of M. tuberculatus and 8% of P. lineata tested positive. The findings demonstrate that WSSV is present in wild crustaceans and mollusks, which may serve as vectors and/or reservoirs of the virus, thereby posing a potential risk to local shrimp farming. This is the first report of WSSV in wild specimens of M. tuberculatus and P. lineata.     

Feeding patterns in five predatory fishes of the high Paranà River floodplain (PR, Brazil)

Abstract— Between March 1992 and February 1993 five piscivorous fish species, Acestrorhynchus lacustris (Reinhardt, 1874), Hoplias malabaricus (Bloch, 1794), Rhaphiodon vulpinus Agassiz, 1829, Salminus maxillosus , Valenciennes, 1840 and Plagioscion squamosissimus (Heckel, 1840), of the high Paranà River floodplain showed a wide total prey spectrum though only three to four taxa were dominant in their diet. Shrimp, Macrobrachium amazonicum , were also common to the majority of species. Seasonal and spatial variations occurred throughout the study period probably due the availability of prey species. The main resources shared by the predators were also the most abundant in the area, with consumption markedly focused on prey about 5.0 cm long. Detrended correspondence analysis was effective in discriminating two groups of predators species that exploited distinct microhabitats. The predators with the least scores consumed small characids that inhabit mid-water or the littoral region, whereas those with the largest scores consumed prey associated to the bottom.     

The decline of fisheries on the Madeira River,Brazil: The high cost of the hydroelectric dams in the Amazon Basin

Despite being considered beneficial by providing a clean and renewable source of energy, the construction of hydroelectric dams has extremely negative implications for Amazonian fisheries. This study investigated the impacts of the Santo Antônio and Jirau hydroelectric dams on the fishery stocks of the Madeira River. This investigation was based on fish catch data from the Z‐31 fishing colony, located in the municipality of Humaitá, in Amazonas State, Northern Brazil. Data were collected daily and provided information on the date of return from each trip, the fish species targeted, and the total catch (kg) between January 2002 and September 2017. The results indicated reductions of 39% in the mean annual catch and 34% in the mean monthly catches. These results highlight the high price paid by local fish communities for the development of hydroelectric power in the Amazon basin.     

Distribution and establishment of the alien Australian redclaw crayfish,Cherax quadricarinatus,in the Zambezi Basin

1. Crayfish are invasive polytrophic keystone species, which are phylogenetically unique on the African continent. The Australian redclaw crayfish Cherax quadricarinatus is invasive in southern African freshwater systems including the Zambezi River Basin. Surveys conducted across the Zambezi Basin (Botswana, Zimbabwe, Namibia and Zambia) between 2017 and 2019 showed that C. quadricarinatus is broadly distributed across the Upper and Middle Zambezi and is rapidly spreading through natural and human-mediated means across several ecoregions.
2. The probability of capture (P_capture), catch per unit effort (CPUE) and population characteristics of C. quadricarinatus from the recent Barotse floodplain invasion were compared with older invasions from Lake Kariba and Kafue River.
3. The P_capture and CPUE of C. quadricarinatus in the recently invaded region of the Barotse floodplain were similar to those of the older invasions. Mass and carapace length of C. quadricarinatus from the Barotse floodplain were significantly lower than those of C. quadricarinatus from the older invasions. Sex ratios differed significantly between the three invasive populations. The Barotse floodplain population had a disproportionate investment in females (65.3%) and intersex individuals (8.4%). No crayfish were detected in the Zambezian Headwaters or the Okavango Floodplains ecoregions, but current spread rates are 49 km yr⁻¹ downstream and 12 km yr⁻¹ upstream.
4. Investment in population management and the prevention of spread will have high conservation value across the invaded regions in order to restrict crayfish ecological impacts via direct predation and competition. In areas where crayfish are in high abundance, existing fisheries are affected through damage to nets, leading to increased net abandonment and ghost gear pollution in invaded regions.
5. The emphasis should be on developing cohesive transboundary biosecurity policies in southern Africa to limit further spread that will threaten the integrity of freshwater ecosystems. However, long-term monitoring is needed to gauge invasion risk to sensitive areas such as the Okavango Floodplains ecoregion and determine field-based ecological impacts.

     

Effects of flow variation on channel and floodplain biota and habitats of the Sacramento River,California, USA

• 1. Despite progress in the development of conceptual models of river processes, the validation and application of these models to conservation may be limited by a deficit of tools for intermediate‐scale (1–100km) reaches. A model was developed to examine the effect of variation in flow on the responses of two trophic levels in a large temperate river (Sacramento River) and its seasonal floodplain (Yolo Bypass). Field data and hydrologic simulations were evaluated for three hydrologically diverse years.
• 2. The simulations showed much more hydrologic variability in the floodplain than the river, with greater total surface and shallow area, longer hydraulic residence times, and lower water velocities for the floodplain.
• 3. Chlorophyll a levels were significantly higher in the floodplain than in the river, and were negatively associated with flow. These results were consistent with longer hydraulic residence times, increased surface area of shallow water, and warmer water temperatures.
• 4. Copepods and cladoceran densities were similar in the river and its floodplain, and were mostly negatively associated with flow.
• 5. There were significantly higher densities of Diptera and terrestrial invertebrates in the floodplain than the river. Diptera densities in the floodplain were positively associated with flow.
• 6. These results provide evidence of the incremental value of floodplain habitat to the conservation of large rivers. In particular, it appears that providing river–floodplain connectivity can enhance production of lower trophic levels at relatively rapid time scales, probably benefitting secondary consumers, including Chinook salmon (Onchyrhynchus tshawytscha).

Copyright © 2004 John Wiley & Sons, Ltd.     

Effects of artificial substrate and night‐time aeration on the water quality in Macrobrachium amazonicum (Heller 1862) pond culture

The effects of artificial substrate and night‐time aeration on the culture of Macrobrachium amazonicum were evaluated in 12 ponds stocked with 45 prawns m^?2. A completely randomized design in 2 × 2 factorial scheme with three replicates was used. The combination of factors resulted in four treatments: with substrate and aeration (SA), with substrate and without aeration (SWA), without substrate and with aeration (WSA) and without substrate and aeration (WSWA). The presence of substrate in SA and SWA treatments reduced suspended particles (seston) by ~17.3% and P‐orthophosphate by ~50%. The use of aerator (WSA and SA treatments) significantly (P < 0.05) increased the concentration of dissolved oxygen, suspended particles and nutrients in the pond water. These results indicate that the effect of substrate on turbidity and total suspended solids (TSS) values is opposite to the effect of the aerator. The aerators in semi‐intensive grow‐out M. amazonicum farming lower water quality because they increased the amount of detritus and nutrients in the pond water. On the other hand, the use of artificial substrate reduces turbidity values, chlorophyll a, TSS and P‐orthophosphate concentrations. Therefore, the combination of substrate addition and night‐time aeration is not interesting because they have opposite effects.     

Attitudes and opinions of commercial fishermen on whitefish management in the Gulf of Bothnia, Finland

Abstract Catches of anadromous whitefish in the Gulf of Bothnia have declined since theearly 1990s. It is generally assumed that the cause is overfishing. The professional fishermeninterviewed in the present study were united in the opinion that it is necessary to set limits onthe fishing of whitefish, but had differing views about the means of achieving this. Thesedifferent arguments involved separate whitefish stocks, various types of gear and differentmotives for fishing. Most of the professional fishermen accepted a minimum mesh size for gillnets. Other means proposed included setting limits on non-professional fishing and sales ofcatches. There were conflicting attitudes about seasonal restrictions because their experienceswith fishing restrictions for salmon had been negative. On the whole, decision-making requiresmore regional information on whitefish stocks and fishing, but also on the social and economicflexibility of fishermen.     

沁河稀有经济鱼类栖息水域水质与饵料生物调查研究

通过对稀有经济鱼类乌苏里拟鲿(Pseudobagrus ussuriensis)、唇(Hemibarbus labeo)在沁河栖息流域水域生境现状进行调查研究。研究结果表明:调查水域p H值在8.12~8.74之间,离子总量在390~430 mg/L;总碱度在3.04~3.35 m Eq/L,总硬度在4.56~5.24 m Eq/L;三种形式的氮中硝态氮最高,为0.348 mg/L,氨态氮平均值0.260 mg/L,亚硝态氮最低,为0.008 mg/L,氮总量在0.223~1.129 mg/L;活性磷在0~0.009 mg/L,总磷在0.024~0.071 mg/L。调查区域浮游植物调查共检出7门46属(种),其中硅藻门最多,有18属(种),绿藻门次之,有13属(种),其余依次为蓝藻门5属(种),金藻门3属(种),裸藻门3属(种),隐藻门、甲藻门各2属(种)。底栖动物共检出3门5纲12种,其中节肢动物门8种,环节动物门2种,软体动物门的腹足纲2种。大型水生植物共采集到17种。     

Science,capacity building and conservation knowledge: The empowerment of the local community for marine conservation in Rapa Nui

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Large‐bodied fish migration and residency in a flood basin of the Sacramento River,California, USA

River–floodplain complexes represent some of the most variable and diverse habitats on earth, yet they are among our planet's most threatened ecosystems. Use of these habitats by large‐bodied fishes is especially poorly understood, particularly in temperate regions. To provide insight into the factors that affect floodplain assemblages and migration, we sampled large‐bodied fishes with a fyke trap for 7 years in the Yolo Bypass, the primary flood basin of the Sacramento River, California. We collected a total of 18,336 individual fish comprised of 27 species, only 41% of which were native. Year‐round resident species white catfish Ameiurus catus, channel catfish Ictalurus punctatus and common carp Cyprinus carpio (all alien species) were the most abundant and comprised 74% of the total catch. Splittail Pogonichthys macrolepidotus (3.8%), white sturgeon Acipenser transmontanus (2.3%) and Sacramento sucker Catostomus occidentalis (1.1%) were the primary native species. We found that seasonal variation in water temperature and flood stage were important factors affecting the fish assemblage structure and the presence of migratory species. American shad Alosa sapidissima, an alien species, showed highest abundance during the early summer upstream migration, when temperatures were warmer. For native species, the abundances of white sturgeon, splittail, Sacramento pikeminnow Ptychocheilus grandis and Sacramento sucker were all highest during flood pulses. While our results suggest that flow alone is not sufficient to control alien species, the strong linkage between native fish migration and flow pulses highlights the importance of river–floodplain connectivity for the conservation of native fishes.     

Fishers' experiences and perceptions of marine mammals in the South China Sea: Insights for improving community‐based conservation

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潇河支流白马河水质污染的时空变化特征

根据调查资料和河流断面取样点的月度监测数据,研究了潇河支流白马河段水质的时空变化特征,并对水质富营养化程度进行了评价。结果表明,白马河水质较差,属于GB3838-2002《地表水环境质量标准》劣Ⅴ类水质,河流附近乡镇未经处理的生活污水以及造纸废水的排放是造成白马河水质污染的主要原因。从空间尺度上看,化学耗氧量(COD)、氨氮(NH3-N)、总磷(TP)浓度分别沿河流从上游的171.926 mg/L、3.248 mg/L、0.616 mg/L降低到下游的34.920 mg/L、0.560 mg/L、0.208 mg/L,表明白马河水体具有一定的自净能力,但自净能力较差;在时间变化特征上,COD、NH3-N、总氮(TN)浓度10-12月逐渐降低至171.926 mg/L、3.248 mg/L、4.233 mg/L,但COD在1月突然升高至308.772 mg/L,之后又逐渐降低,NH3-N从1月开始快速回升,至2月达到最高值16.576 mg/L,TN在4月达到最高值18.342 mg/L,之后急速降低;总磷浓度在0.397~0.858 mg/L之间波动,无明显变化规律。     

Time‐series analysis of native and non‐native crayfish dynamics in the Thames River Basin (south‐eastern England)

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