Impact of flood control schemes on river fish migrations and species assemblages in Bangladesh

A mark-recapture programme at the Pabna Irrigation and Rural Development Project (PIRDP) site in NW Bangladesh showed that Catla catla, Channa striata and Wallago attu migrated through the sluice gates, both with and against prevailing currents in different season, while the smaller Anabas testudineus, Glossogobius giuris and Puntius sophore did not. Species assemblages were significantly different inside and outside the flood control, drainage and irrigation (FCDI) schemes, with up to 25 species absent or less abundant inside compared to outside. The majority of these species were large predators or conspicuous members of the highly prized migratory 'whitefish' category, including silurid catfish, Indian major carps, mullets and clupeids. In their absence, species inside FCDI schemes were dominated by much smaller resident 'blackfish' species. Assemblages inside FCDI schemes thus had both a reduced species richness, and a unit value reduced by up to 25%. It was concluded that FCDI schemes such as the PIRDP negatively affect fish species assemblages and stock values, by reducing the accessibility of impounded floodplains to migrant fish. Though some fish are capable of penetrating existing sluice gates, management measures are required to encourage the passage of more species.     

Flood regime,dam regulation and fish in the Upper Paraná River: effects on assemblage attributes,reproduction and recruitment

The flood regime is the most important force determining seasonality in neotropical rivers. In the Upper Paran River floodplain, it is the primary factor influencing biological processes. The aim of this paper is to summarize information on the influence of dam-controlled floods on some fish assemblage attributes, reproduction and recruitment in the Upper Paran River floodplain, providing preliminary guidelines for dam operation upstream. Fish were collected in different habitats of the Upper Paran River floodplain (river, channels and lagoons) in the period from 1986 to 2001. The high water period in the Paran River usually occurs from November/December to April/May. Annual variation in the hydrograph affects species with distinct life history strategies differently, and influences the composition and structure of fish assemblages. Large floods were associated with higher species richness. Frequencies of individuals with ripe and partially spent gonads, which indicate spawning, were higher during the period of increasing water level. Dependence on floods seems to be lowest in sedentary species that develop parental care, and highest in large migratory species that spawn in the upper stretches of the basin and use flooded areas as nurseries. Migratory fishes were favored by annual floods that lasted more than 75 days, with longer floods yielding larger populations. The occurrence of high water levels at the beginning of summer is fundamental to the spawning success of migratory species. However, the flood may be less important for recruitment of juveniles if it is of short duration. Dam operation upstream (releasing more water during the raining season) has potential to promote greater floods with appropriate duration improving recruitment, particularly for migratory species.     

River‐lake migration of fishes in the Dongting Lake area of the Yangtze floodplain

Over the past few decades, fish resources have declined severely owing to the river–lake disconnection within the Yangtze River floodplain. Studies on fish migrations between rivers and floodplain waters are imperative for fish resources restoration and lake management. However, few studies have as yet documented the migration rhythms of river–lake migratory fishes. Monthly investigations of the fish assemblage structure were conducted in three regions of the Dongting Lake, which is connected to the Yangtze River. Main results were: (i) Fish catches varied greatly, depending on the water level and area of the lake; (ii) Ten river–lake migratoty species were caught during the study, 80% of these during July–October when the water level was high. Species richness and relative abundance both decreased with increasing distance from the river, and the timing of peak abundance occurred later in the year; (iii) Abundance of grass carp (Ctenopharyngodon idella) and silver carp (Hypophthalmichthys molitrix) peaked in July and August and were mainly composed of 0 + fishes. The results revealed that the key time for migration into the lake is July–August. Combining the results from previous studies, a comprehensive view is given of migration patterns of four domestic Chinese carps; (iv) Brass gudgeon (Coreius heterodon), appeared to migrate into the Dongting Lake as two separate shoals, differentiated by body size. They also appeared to remain close to the lake mouth area. Based on the above results, two recommendations can be made for river–lake migratory fish conservation in the Yangtze floodplain: prolonging the current fishing ban period of April–June to April–September; and opening sluice gates for as long as possible during April–September in order to maximize the opportunities for fish migration.     

Fish passage experience at small-scale hydro-electric power plants in France

There are more than 1,700 small-scale hydro-electric power stations in France today, which can be found on the majority of rivers with migratory species in them. This article gives an overview of the different types of fish facilities in use at these small-scale hydro plants. The relative advantages and drawbacks of each type of fish pass are discussed, with reference to the requirements of migratory species and the site-specific constraints. Emphasis is placed on the problems of attraction and maintenance. The article also mentions the various techniques used to evaluate existing or recently constructed fish passes. Experience in using bypass facilities combined with trashracks for downstream juvenile salmonids and eels are related. The author points out the severe cumulative impact which may occur due to the existence of several small-scale hydro projects on the same river. He presents his view on the priorities for research on fish passage facilities, especially on “fish friendly” small-scale hydropower intakes. Guest editors: R. L. Welcomme & G. Marmulla Hydropower, Flood Control and Water Abstraction: Implications for Fish and Fisheries     

Migratory movements of pacu, Piaractus mesopotamicus, in the highly impounded Paraná River

A mark‐recapture study was conducted in 1997–2005 to investigate movements of stocked pacu, Piaractus mesopotamicus, in the Paraná River Basin of Brazil, Paraguay, and Argentina. Fish raised in cages within the Itaipu Reservoir and in ponds were tagged externally (n = 2976) and released in the Itaipu Reservoir (53.2%) and bays of its major tributaries (46.8%). In total, 367 fish (12.3%) were recaptured. In all, 91% of the pacu moved away from the release site; upstream movements were more extensive than downstream movements. Pacu traveled upstream a maximum of 422 km (average of 41.3 km) at a maximum rate of 26.4 km day⁻¹ (av. 0.8). Downstream movements were limited in terms of number of individuals and distance moved. Fish released during the wet season moved farther than those released during the dry season, and feeding rather than spawning might have been the compelling reason for movement. Although fish passed downstream through dams, none of the marked fish were detected to have moved upstream through the passage facilities. Pacu showed movement patterns not radically different from those of other neotropical migratory species, but their migratory movements may not be as extensive as those of other large migratory species in the basin.     

Hydrological seasonality dictates fish fauna of the lower Araguaia River,Tocantins-Araguaia basin

Hydrological seasonality of flow dictates diversity in tropical aquatic ecosystems. Large tropical rivers and tributaries are typically more depth and shows increased flow velocity and area in flood than in dry season. A thorough analysis of seasonality effect on fish community structure can provide valuable information of major forces driving tropical communities. However, these types of analyses have been limited by poor knowledge of tropical diversity, human impacts on environment, and biased sampling methods. We used a pristine large tropical river (and tributaries) and five types (12 gill nets, beach seine nets, longlines, branch baited hooks, and cast nets) of fishing gears to present an evaluation of flow seasonality effect on fish community. We sampled fourteen sites in river channel and tributaries in the lower Araguaia River. Sampling was conducted in flood (March and May 2009) and dry (July and September 2009) seasons of a typical seasonal year. Species richness, Shannon Diversity and Evenness, mean similarity of binary data, and abundance (CPUE) were analyzed by PERMANOVA and PCoA. We also analyzed the species most correlated (by Spearman correlation rank) with flood and dry season. Features differed significantly between flood and dry seasons, but not between channel and tributaries. The composition and abundance of community, and the representative species of flood and dry changed quite along the year. Flood showed lotic-related species, and dry presented lentic-related species. Thus, we achieved an alternation of fish community between season, both for channel and tributaries.     

Spatial and Temporal Patterns of Diversity and Distribution of the Upper Juruá River Fish Community (Brazilian Amazon)

We studied spatial and temporal patterns in fish species composition and diversity at the upper Juruá River located in the west Brazilian Amazon. We collected with gillnet 822 fishes belonging to 90 species in the main Juruá River, its tributaries and the floodplain lakes during wet and dry seasons. Fish abundance and species richness were greater in the dry season. During that season, fishes may be concentrated due to the low water level, being caught more easily by gillnets. There has been a trend towards a greater fish biomass caught in lakes. This might be associated with a greater environmental stability as lakes may be less subject to large variations in water level. The fish communities differed between the two seasons and between lakes and the lotic environments (main river and tributaries). Fish species from the family Curimatidae were most abundant in the lakes, while Pimelodus spp. and Hypostomus spp. predominated in the main Juruá River. Seasonal variations in fish communities may be related to differences in the migratory behavior among fish species. Such spatial and temporal patterns influencing fish community structure at the Upper Juruá Extractive Reserve must be accounted for in management and conservation strategies.     

Influence of irrigation infrastructures and water quality on fish assemblages in Lake Tana tributaries,north-west Ethiopia

Lake Tana is one of East Africa’s largest freshwater bodies, yet many of its fishes are migratory and utilize in-flowing tributaries as critical spawning habitat. However, factors such as expanding water resources developments and sand mining along these rivers and streams may disrupt this ecosystem function. We monitored juvenile and adult fish abundance and water quality across five lake tributaries from August 2014 to April 2015 to examine how irrigation schemes and water quality affect assemblage and population structure. Adult assemblages were dominated by Labeobarbus cyprinids and varied between tributaries, albeit without separation by irrigation development or sand mining. Overall, adult abundances of the dominant migratory Labeobarbus species were four-fold higher below the Shini River irrigation weir than upstream. Contrastingly, juvenile abundances were often significantly higher above these structures. Juvenile abundances decreased on average by 46% along the first 1000 m of two irrigation canals, suggesting poor habitat suitability or high mortalities from water withdrawals. Water quality varied more between rivers than sampling times, but without any separation of tributaries by irrigation or sand mining. Conductivity and turbidity-related parameters had the highest correlation with adult assemblage structure and individual species abundances. These findings indicate that Lake Tana tributaries must be managed on a case by case basis, with more focus given to mechanisms allowing fish to bypass irrigation developments and the direct assessment of fish populations between sand mining and other sites.

     

Lower Mekong Fish Passage Conference: Applying innovation to secure fisheries productivity

The Lower Mekong Basin (LMB) is one of the most biodiverse regions in the world. It contains almost 1,100 fish species and supports a regional population of almost 60 million people. Fish provide protein, essential micronutrients and income for many of these people. Further, over 85% of fish are migratory and undertake small‐ and large‐scale movements to access spawning, feeding and nursery habitat. In recent times, irrigation and hydropower development have threatened the long‐term sustainability of fisheries resources in the region, and there is a need to develop robust mitigation measures in order to protect and improve fish passage and fisheries productivity. Recognising this, a conference, with 160 delegates from 14 countries brought together global experts in the fields of riverine development, fish passage and aquatic ecosystem management to demonstrate how applied research has been used over the last decade to enhance policy and decision‐making across the LMB and to discuss future directions.     

Early fish growth varies in response to components of the flow regime in a temperate floodplain river

1. The biological productivity of floodplain rivers is intimately related to their flow regimes and it has been proposed that fish production should be linked to components of the flow regime in productivity models. To assess applicability of existing models of productivity in floodplain rivers, we tested predictions about growth during the early life stages of a common, short‐lived fish (Australian smelt Retropinna semoni) in a non‐flow‐altered, temperate Australian floodplain river. 2. The morphometric condition of larval and juvenile fish measured over a five‐year period was positively related to annual discharge, but the highest average seasonal growth rates occurred in two years of contrasting hydrology, one with early spring flooding and the other with predominantly low flows and a late season (within channel) flow pulse. 3. Analysis of daily growth measures indicated that timing, river height, the duration of in‐channel flow events and antecedent flood events are all significant factors influencing the early growth of Australian smelt. The flexible manner in which fish growth responds to these factors appears to be an effective early life history strategy for a short‐lived species occupying a highly variable environment. 4. Growth rates conformed to some predictions of the Flood Pulse Concept (in particular the Extended Flood Pulse Concept), but specific growth responses suggest that the Riverine Productivity Model and tenets of the Low Flow Recruitment Hypothesis best describe the production of Australian smelt in this system. We suggest that none of the existing conceptual models adequately describes fish productivity in temperate Australian floodplain rivers but that aspects of each are likely to be relevant under different flow conditions.     

Fish Collections Taken from a Small Agricultural Water Withdrawal Site on the Groot River,Gamtoos River System,South Africa

Summary

Periodic water releases from Beervlei Dam on the Groot River of the Gamtoos River System were planned to flush the riverine pools of brack water and replace the pools with better quality water which was used to flood irrigate lucerne lands. Fish collections were made in a small irrigation canal situated on the banks of the Groot River. Three fish species were collected. Results indicated that up to a total of 131 smallscale redfin minnows, Pseudobarbus asper, are removed from the system every five minutes at this one small water withdrawal site. Larger minnow specimens and carp, Cyprinus carpio, were entrained during high river flows. When the river flow was reduced there were higher catches of young of the year fish. The fish are carried with the pumped water, which is flood irrigated onto lucerne fields, resulting in stranding and eventual mortality. It is recommended that the use of suitable screens, such as wedge-wire screens, could reduce the number of fish removed from the system during these irrigation periods.     

Seasonal changes in European whitefish muscle and invertebrate prey fatty acid composition in a subarctic lake

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Comprehensive passage (COMPASS) model: a model of downstream migration and survival of juvenile salmonids through a hydropower system

Migratory fish populations are impacted worldwide by river impoundments. Efforts to restore populations will benefit from a clear understanding of survival and migration process over a wide-range of river conditions. We developed a model that estimates travel time and survival of migrating juvenile salmonids (Oncorhynchus spp.) through the impounded Snake and Columbia rivers in the northwestern United States. The model allows users to examine the effects of river management scenarios, such as manipulations of river flow and spill, on salmonid survival. It has four major components: dam passage and survival, reservoir survival, fish travel time, and hydrological processes. The probability that fish pass through specific routes at a dam and route-specific survival probabilities were based on hydroacoustic, radio telemetry, PIT tag, and acoustic tag data. We related reservoir mortality rate (per day and per km) to river flow, water temperature, and percentage of fish passing through spillways and then fit the relationships to PIT-tag survival data. We related fish migration rate to water velocity, percentage of fish passing through spillways, and date in the season. We applied the model to two threatened “Evolutionarily Significant Units” (as defined under the US Endangered Species Act): Snake River spring/summer Chinook salmon (O. tshawytscha Walbaum) and Snake River steelhead (O. mykiss Walbaum). A sensitivity analysis demonstrated that for both species survival through the hydropower system was responsive to water temperature, river flow, and spill proportion. The two species, however, exhibited different patterns in their response. Such information is crucial for managers to effectively restore migratory fish populations in regulated rivers. Guest editors: R. L. Welcomme & G. Marmulla Hydropower, Flood Control and Water Abstraction: Implications for Fish and Fisheries     

Fish length exclusively determines sexual maturation in the European whitefish Coregonus lavaretus species complex

The probability that a fish matures at a certain age and length (the so‐called probabilistic maturation reaction norm, PMRN) was analysed for a European whitefish Coregonus lavaretus species complex population living in the Austrian pre‐alpine Lake Irrsee. Fish length was found to be the only relevant determinant of maturation probability, and females matured at slightly smaller sizes than males.     

Relationships between fish assemblages, macrophytes and environmental gradients in the Amazon River floodplain

During the flood season of 1992–1993, 139 species of fishes were collected from a floodplain lake system in the central Amazon Basin. Fish species distribution was examined relative to abiotic variables in seven vegetation strata on Marchantaria Island, Solimões River. Both environmental variables and species distributions were influenced by a river channel to floodplain-interior gradient. Species diversity was significantly higher in vegetated areas than in unvegetated areas, with deeper water Paspalum repens stands harbouring the highest diversity. As a result, species richness and catches were positively related to habitat complexity, while catch was also negatively related to dissolved oxygen (DO) and water depth. Low DO and shallow waters appeared to act as a refuge from predation. Fish assemblages were related to water chemistry, but species richness was not. Canonical correspondence analysis provided evidence that floodplain fish assemblages formed by the 76 most common species were influenced by physical variables, macrophyte coverage and habitat complexity, which jointly accounted for 67% of the variance of fish species assemblages. Omnivores showed no pattern relative to the river channel to floodplain-interior gradient while detritivores were more likely to be found at interior floodplain sites and piscivores closer to the river. Piscivores could be further separated into three groups, one with seven species associated with free-floating macrophytes in deep water, a second with five species found in shallow waters with rooted grasses and a third with six open water orientated species. The results suggest that fish assemblages in the Amazon floodplain are not random associations of species.     

Evidence of stenotopy and anthropogenic influence on carbon source for two major riverine fishes of the Lake Victoria watershed

Stable isotope analysis was used to investigate the migratory status and to determine the relative contribution of allochthonous and autochthonous sources of carbon for the major riverine fish species ( Barbus altianalis and Labeo victorianus ) in rivers draining the Kenyan side of Lake Victoria. The two fish species derived carbon from both C4 and C3 plant sources, although L. victorianus exhibited less enriched isotopic carbon values. Fish samples from stations under direct influence of effluents from sugar factories exhibited enriched δ¹³C signals. Assuming that this reflects carbon sourcing from riparian C4 plants, it suggests that carbon from terrestrial sources can be a major energy source in some rivers. This heavy carbon enrichment associated with sugar factories was spatially restricted and occurred in all seasons, implying that sub-populations of the two fish species are non-migratory. The large migratory populations of these two species, for which Lake Victoria was once famous, may be no more.     

SPATIO-TEMPORAL VARIATIONS OF FISH ASSEMBLAGES IN THE DONGTING LAKE北大核心CSCD

Lake Dongting is the second largest floodplain lake along the Yangtze River basin. However, the study on fish communities in the Dongting Lake is limited, lacking systematic research on the spatio-temporal variations of fish assemblages in this area. Fish were sampled seasonally from December 2012 to October 2014 in the Dongting Lake. 80 fish species belonging to 54 genera, 17 families, and 7 orders with dominant Cyprinidae accounting for 58.8% of the total species were collected. The species richness reduced by 36 in contrast with the historic records. The number and percentage of riverine and river-sea migratory species decreased by 13 (2.2%) and 4 (3.0%) respectively in comparison with historic records. We detected significant seasonal and regional differences in species composition and biodiversity. The diversity and evenness of fishes were significantly higher in summer and autumn than those in other seasons. Meanwhile, significantly lower diversity was observed in the east Dongting Lake than other regions. Our results indicated that seasonal flood pulses and, assisting by river-lake connectivity may play a fundamental role for the fish resources supplement in floodplain lakes. This study demonstrated significant spatio-temporal variations of fish assemblages in the Dongting Lake, which provided scientific foundations for fish conservation in this area. © 2019, Institute of Hydrobiology, Chinese Academy of Sciences. All rights reserved.     

Environmental influences on seasonal distribution of coastal and estuarine fish assemblages at Wemindji,eastern James Bay

Synopsis The coastal fish assemblages of Wemindji, eastern James Bay, were studied in 1987 and 1988 to describe seasonal utilization of the Maquatua River estuary and the adjacent coastal waters by marine and anadromous fishes. Fish diversity was low (11 sp.) and experimental gill net catches were highly variable between sites in the estuary and coastal waters, and also seasonally at a given site. During summer, the estuarine fishes were numerically dominated by two marine species, the fourhorn sculpin,Myoxocephalus quadricornis, and the slender eelblenny,Lumpenus fabricii, and also by juvenile cisco,Coregonus artedii, and juvenile lake whitefish,C. clupeaformis. In coastal waters, three marine species were abundant: the shorthorn sculpin,M. scorpius, the arctic sculpin,M. scorpioides and the Greenland cod.Gadus ogac. In contrast with the estuary, large (> 270 mm) cisco and lake whitefish were abundant in coastal waters indicating extensive movements of these species in James Bay during the summer. Distribution patterns were influenced by a combination of physical conditions (salinity and temperature) and biological characteristics (habitat choice, migration and reproduction) depending on the season.     

Variability of fish diets between dry and flood periods in an arid zone floodplain river

The fish assemblages of an arid zone floodplain river, Cooper Creek, Queensland, Australia, were sampled during two dry periods in isolated waterholes and on the inundated floodplain during the early and late phase of a major flood event. Diets were described for nine native species and compared within and between dry and flood periods. In the dry season, when fishes were restricted to waterholes, diets were characteristically simple with narrow diet breadths. Movement onto the floodplain during flooding clearly increased feeding opportunities, with greater diet breadths evident in all species. Despite obvious potential for terrestrial inputs, diets tended to be dominated by aquatic resources in both the waterholes and on the floodplain. Stomach fullness, however, varied little between dry season waterhole and floodplain samples. Fishes appeared to feed on potentially lower value resources such as detritus and calanoid copepods during the dry season, when waterholes were isolated and food resources were limited. They were then able to capitalize on the 'boom' of aquatic production and more diverse food resources associated with episodic flood events.