Biological Assessment Presentations

Monday General Session

Biological Assessment Theme Panel Review Paper, by Steven J. Cooke, Rose E.M. Entsua-Mensah,  Kai Lorenzen, Nigel P. Lester,  John D. Koehn, Robert G. Randall,  So Nam,  Scott A. Bonar,  David B. Bunnell,  Paul Venturelli, Shannon D. Bower and  Ian G. Cowx

Tuesday Oral Presentations

Lebanon Room (Room D209, Floor 2, Building D)

The Foundation of Inland Fisheries–Key Principals of Ensuring Healthy and Productive Freshwater Ecosystems, by Nicolas W. R. Lapointe (Canada), Steven J. Cooke, Jack G. Imhof, Daniel Boisclair, John M. Casselman, R. Allen Curry, Otto E. Langer, Robert L. McLaughlin, Charles K. Minns, John R. Post, Michael Power, Joseph B. Rasmussen, John D. Reynolds, John S. Richardson, & William M. Tonn

Freshwater ecosystems and the fisheries they support are increasingly threatened by human activities. To aid in their management and protection, we outline nine key principles for supporting healthy and productive ecosystems based on the best available science, including: laws of physics and chemistry apply to ecology; population dynamics are regulated by reproduction, mortality, and growth; habitat quantity and quality are prerequisites of fish productivity; connectivity among habitats is essential for movements of fishes and their resources; freshwater species and their habitats are tightly linked to surrounding watersheds; biodiversity enhances ecosystem resiliency and productivity; global processes affect local populations; anthropogenic stressors have cumulative effects; and evolutionary processes can be important. These principles must be considered when identifying management options and developing policies aiming to protect productive freshwater ecosystems and ensure that inland fisheries are sustainable.

Assessing Condition of Freshwater Habitats Using a Landscape Approach: Improving Opportunities for Conserving Inland Fisheries Over Large Regions, by Dana M. Infante (The United States of America) & William W. Taylor

Efforts to conserve and manage freshwater habitats from current and future threats depend on the ability to characterize the natural potential of systems for supporting fisheries of interest, to identify anthropogenic stressors to habitats, and to prioritize and apply effective strategies to achieve fisheries management objectives. Increasingly, such assessments are conducted over large regions, including freshwater habitats of entire countries or even continents, offering new insights into condition of habitats and conservation opportunities. The basis for such large-scale assessments depends on a landscape approach, which asserts that natural and anthropogenic landscape factors of regions drained by freshwater systems can influence habitats and the fisheries they support. Such work has been facilitated with greater availability of remotely-sensed information and through advancements in GIS and database technologies, and they are increasingly viewed as effective management tools, even when site-specific data may be limited. This presentation describes one ongoing effort to assess river habitats of the conterminous United States using a landscape approach and highlights how mangers are using assessment results to more effectively conserve fluvial fisheries. Besides demonstrating the application of this approach, this presentation describes the potential for conducting similar work in other regions, underscoring how a landscape approach can aid in conservation of freshwater fisheries globally.

Biological Assessment of Small-Scale Tropical Inland Fisheries: Navigating Complexity, Limited Knowledge, and Human Responses, by Kai Lorenzen (The United States of America), Robert Arthur, Caroline Garaway, Sarah Martin, & Sophia Nguyen Khoa

Biological assessment of management options for tropical small-scale freshwater fisheries is challenging due to the complexity and interactions of biological, technical, and human factors; lack of scientific knowledge; and the very limited resources commonly available for conducting such assessments. Under these circumstances, assessments based solely on biological principles, often derived from studies of different (temperate) environments, can be misleading. We review case studies from the Mekong region on fisheries impacts of irrigation development, stocking of non-native species and draining of floodplain lakes, contrasting impacts expected a priori from biological principles with those measured in large-scale field studies. In all cases, actual biological outcomes were substantially different from those initially predicted. Reasons for unexpected outcomes included unrealistic assumptions about key bio-physical processes and strong effects of human (fishing effort) responses to the technical interventions being assessed. We recommend adopting a systems perspective to guide even purely “biological” assessments, allowing for the possibility that common assumptions about key bio-physical processes may not hold for the system in question, considering a wide range of management options, and conducting rigorous experimental or observational studies to assess actual outcomes.

Indices for Biological Assessments: Past, Present, and Future, by Craig P. Paukert (The United States of America) & Nicholas A. Sievert

Indices of Biological Integrity (IBIs) for fish communities were developed in the 1980s to assess the ecological integrity of warmwater stream fish assemblages in the United States of America. This composite index used metrics of species richness and composition, abundance, trophic composition, and deformities/disease to develop a single value that represents ecological integrity. Since its development, there has been a proliferation of research to refine the index to account for regional differences and apply the index to lakes, rivers, reservoirs, wetlands, and estuaries worldwide. For example, the index was used to determine the effects of overfishing in the Yangtze River, effluents in Indian and West African rivers, and differentiating reference and disturbed sites in North American and European rivers. Recently research evaluating the individual index components to stressors has emerged to further refine the specific drivers of the index scores. Although the IBI has been very useful and stemmed much evaluation, future direction of these indices may focus on assessing the impacts of climate change on fish assemblages. We recently developed an index that uses fish traits and their responses to warming temperature and altered flow regime to develop a vulnerability index to climate change for Midwest U.S. streams. This vulnerability assessment is highly adaptable where life history traits or responses to temperature and flows are known. The use, evaluation, and criticism of the IBI has led to continued refinement and a move towards newer threats such as climate change.

A Moving Target: Incorporating Spatial Ecology of Fish into Biological Assessment and Management of Inland Fisheries, by Steven J. Cooke (Canada), Michael Power, Susan Doka, Charles Kruege, John Dettmers, & Eduardo Martins

Freshwater fish are mobile, moving vertically and horizontally through the aquatic landscape. Fish move for a variety of reasons, such as to find and exploit patchy resources or to locate essential life-stage specific habitats (e.g., for spawning). Because fish are essentially a moving target, there are inherent challenges with biological assessment. We submit that quantifying and describing the spatial ecology of fish is an important component of biological assessment. Failure to understand the spatial ecology of fish can bias population assessments and lead to erroneous management actions. We highlight the tools available for studying the spatial ecology of fish and how the knowledge generated from such tools feeds into biological assessment and management.

How Standard Fish Sampling Methods Help Improve Biological Assessment Across Political Boundaries, by Scott A. Bonar (The United States of America), Wayne A. Hubert, & Norman Mercado Silva

Standard measuring techniques have been responsible for substantial human progress and are widespread in a variety of disciplines such as medicine, meteorology, water quality, cartography, geology, and industry.  Methods to standardize freshwater fish monitoring are increasingly being developed to allow scientists and managers to compare data across political boundaries.   Standardization is the collection of data using the same gear types fished in the same manner in different waterbodies or in the same waterbody over time.  Use of standardized methods has many advantages.  Standardization of methods reduces variability due to different gear bias.  Fewer sampling gears (with standardization) facilitates validating sampling gears under a wide range of conditions. Using well-accepted standard methods lends additional credibility to a study. Fisheries studies increasingly use data from multiple states, countries, and continents to address threats such as climate change, which occur across larger geographic regions, so standardization allows easier data comparisons and communication.  The American Fisheries Society’s (AFS) standard sampling program is one such example of continent-wide standardization.  An overview of this program demonstrates how scientists and managers can compare data across political boundaries, describes other advantages to standard data collection, and shows how standard data from fish communities can be easily compared using modern computerized techniques.

Understanding the Role of Water Dynamics in Governing Fisheries Productivity and Novel Approaches in Monitoring and Evaluation, by Fiona  Simmance (The United Kingdom of Great Britain and Northern Ireland) & Jeppe Kolding

There is a global gap in understanding trends in small-scale inland capture fisheries production, their contribution to food and livelihood security, and how climate variability impacts them. This is confounded by the complex socio-ecological features of these systems and the difficulty in monitoring and obtaining reliable data. Simple empirical model approaches which require limited data input have been developed since the 1950s to try to understand factors governing fish yields and to predict the potential yield of inland waters. The most recent mode, the Relative Lake Level Fluctuation Index (RLLF) proposed by Kolding and Zwieten (2012), builds on previous work and has shown that water level fluctuation is an important factor governing fish productivity within tropical lakes and reservoirs. This paper will test the RLLF index and examine the relationship between water level fluctuation and fish yield at a water-body level in a shallow, unstable lake system: Lake Chilwa in southern Malawi. An evaluation of available monitoring data will be made and the use of innovative approaches in remote sensing will be outlined for providing fishery-related water level data. The aims of the paper are: (1) to evaluate how effective the RLLF index is in understanding small-scale fisheries trends, (2) to evaluate the role of remote sensing in providing data in data-poor areas, (3) to evaluate the potential use of the model for predicting fisheries production, and (4) to discuss the implications for food security, fisheries management, and resilience in complex socio-ecological systems.

A Fuzzy Logic Approach to Explore the Dynamic of Changes that Affect Inland Fisheries in Central Kalimantan, Indonesia, by Eny Buchary (The Republic of Indonesia and The Kingdom of Sweden), Cameron Ainsworth, & Tracy Van Holt

Inland fisheries contribute to sustaining the livelihoods of riverine communities. These fisheries are affected not only by fish harvest pressure but also by land use changes. Nevertheless, inland fisheries usually receive less priority in national fisheries management strategies. Moreover, given various management constraints, inland fish stocks are consequently rarely assessed and thus, data becomes limited. Local ecological knowledge can be tapped to understand natural resource dynamics, particularly in data-limited situation, and aid management and assessments. We report on preliminary findings that used local ecological knowledge to explore and assess the state of inland fisheries in two watersheds with distinct upland activities in Central Kalimantan, Indonesia. We used fuzzy logic analysis to standardize and quantify the anecdotal evidence on the most exploited fish species in the area. We combined this with additional indicators such as changes in fish body size and intrinsic vulnerability to fishing determined from life history parameters to produce a decadal time series of resource abundance from 1970 to present. We also use mean trophic level of catches and catch-per-unit-effort data from official reported catch statistics of more recent years to establish a scale with which to interpret the changes. The output of the fuzzy logic analyses is a time series of abundance for select species that can be compared with known trends, and in this case, with trends of known landscape changes in adjacent areas. We also examine the trade-offs of this approach for scaling-up.

The Potential of Fishermen Log Books in Fisheries Assessment, by Christian Skov (The Kingdom of Denmark) & Josianne Stottrup

Log books where fishermen report their catch can be a useful and relatively cost effective tool in fisheries assessment, such as revealing long-term population trends in abundance and size distribution. However, it requires an approach where both effort and catch are reported in a standardized way. Here, two examples of fishermen log books are presented. One is for reel-and-rod fishing where anglers report fishing hours together with catch details, and the other is for passive fishing gear where the fishermen fish at fixed positions during a particular time period each month using standardized gear which is supplied by the government. The applicability of the presented methods will be discussed in a global context.

Mobile Technologies and Inland Fisheries Assessment: Insight from a Case-Study of a Popular Smartphone Application in Alberta, Canada, by Paul A. Venturelli (The United States of America), Jason T. Papenfuss, Nick Phelps, & David Fulton

Fisheries assessment requires information about harvest and effort, and how these vary in space and time. Conventional approaches to obtaining this information are costly, limited by diminishing resources, fairly restricted in time or space, and may not be appropriate for all inland fisheries sectors. In this study, we analyzed three years of angler data from a popular mobile fishing application (app) in Alberta, Canada, to identify province-wide, seasonal patterns of (1) lake popularity that were consistent with conventional data, and (2) anthropogenic lake connectivity that has not been widely described in Alberta or elsewhere. This case study, and similar work in other parts of North America and Europe, shows that mobile technologies can provide inexpensive, high-resolution, real-time harvest data and engage stakeholders through citizen science. The challenge before us is to understand the benefits and limitations of this novel tool, and, where appropriate, tailor its use to a diversity of recreational fisheries as well as small-scale commercial and subsistence fishing sectors.

Lunch break

Problems in Catch Assessment and Fisheries Management in the Upper Zambezi River System, Africa, by Denis Tweddle (The Republic of Namibia), Richard A. Peel, Clinton J. Hay, & Olaf L. F. Weyl

The Zambezi River flows for 2,575 km, with a catchment area of 1.32 million km² in eight countries. Floodplain systems on the Upper Zambezi River above Victoria Falls support major subsistence fisheries. Data on subsistence fisheries in the rivers and floodplains are sparse, and floodplain fish catches go largely unrecorded. The true value of the fisheries is not recognised and therefore the fisheries departments are poorly-funded and staffed. Together with an inability to deal with the complications of open-access fisheries and impoverished communities, this results in failure to effectively manage fisheries on an optimally sustainable basis. These failures have resulted in overfishing according to all key indicators, i.e., catch rate, biodiversity, size, and value. Examples are provided of (1) decline in catches of high value species through use of destructive fishing gears, leading to dependence on low-value species previously ignored, e.g., Central and Southern Barotse Floodplains, and (2) exporting wealth at the expense of local communities, e.g., Lake Liambezi. There is an urgent need for the riparian governments to respond to these problems by implementing the FAO’s Code of Conduct for Responsible Fisheries, particularly through initiatives to improve understanding of the true scale of these fisheries through effective monitoring and research. With improved resources, knowledge, and capacity to disseminate appropriate management advice, it is argued that Zambezi fisheries can be better managed through empowerment of fishing communities. Government legislation needs to improve recognition of community rights over resources, and provide an enabling environment in which co-management can be implemented.

Assessment of Fish Ecological Status of Rivers in Poland (EFI Plus PL, IBI PL), by Prus Pawé, Adamczyk Mikó, Buras Pawé, Wíniewolski Weisaw, & Piotr Parasiewicz (The Republic of Poland)

In this paper, we present the recently developed tool for assessment of ecological status applied in a river monitoring program in Poland. Assessment of ecological status of rivers based on fisheries observations is an obligation of EU members as required by Water Framework Directive. Each country is using specific , locally adequate systems. The European Fish Index EFI+ is a multimetric fish index that analyses fish data collected with help of electrofishing technique according to the CEN 14011. It consists of two metrics developed separately for salmonid and cyprinid river zones as two specific indices. The metrics for salmonid index are density of species intolerant to oxygen depletion and to habitat degradation, while the metrics for cyprinid index are number of species which prefer to spawn in running waters and density of lithophilic species. The four metrics were used in the European intercalibration process to validate the national methods of EU members. Another possible option is the use of Index of Biotic Integrity developed in early 1980s in the United States of America. When applied to rivers in in Poland both methods proved to be limited in their assessment of the whole spectrum of Polish rivers. Hence, the chosen assessment method is an adaptation of both above mentioned techniques, which are applied according to the river type. This experiment shows that the combination of techniques can be applied as a foundation for development of sustainable inland fisheries management plans at the regional or global scale.

Assessing Inland Fisheries: What Can be Learned from Australia’s Murray-Darling Basin? by John Koehn (Australia)

Australia’s Murray-Darling Basin (MDB) only converted from a subsistence fisheries by native aboriginal tribes to one that incorporated more wide-scale harvest, including commercial capture fisheries, after the mid-1800s. By 1900, however, there were already concerns raised about potentially unsustainable catch rates for some species and their future. With little concern for catch data, few management changes were made. These fisheries continued to decline, even after reliable market data was available, and are now closed, with take now purely from the recreational fishery. There remains, however, a paucity of data relating to the recreational fishery, and hence a true economic valuation of the fishery. The Murray-Darling Basin is “Australia’s food bowl” and there are competing demands for water and the use of land for agriculture. Without a proper assessment of the worth of fisheries, it is difficult for them to be considered in either economic or social discussions. Overall, MDB native fish populations have suffered substantial declines and are now estimated to be at only 10% of pre-European settlement levels, with efforts are now aimed at addressing threats and rehabilitation of populations. One of the assessment methods for environmental condition monitoring has been the Sustainable Rivers Audit. This audit undertakes standardised sampling (electrofishing) for fish and a range of other variables at randomly selected sites on a rotating basis (every three years). While this has given a range of data indicating that river conditions, in general, are very poor, it has yet to be fully utilised to determine the potential state of the fisheries.

Fishing Down or Fishing Up in Chinese Freshwater Lakes, by Yuyu Wang (The People’s Republic of China), Jun Xu, Xiubo Yu, & Guangchun Lei

Changes in mean trophic level (MTL) of catches have been widely used to reflect the impact of industrial fisheries on aquatic ecosystems because this measure represents the relative abundance of fished species across the trophic level spectrum. In this study, fisheries data from six important freshwater lakes at the middle-lower Yangtze River and Huaihe River reach of southern China from 1949 to 2009 were used to evaluate changes in catch MTL. After fishery markets opened in 1985, fish catches increased significantly in all the lakes. Lakes Poyang and Dongting, which were dominated by omnivores and connect with Yangtze River, showed no significant change in catch MTL before and after 1985. Catch MTL in Lakes Taihu and Hongze increased significantly due to an increase in the proportion of pelagic zooplanktivorous species. The catches in Lake Chaohu were dominated by zooplankton-feeding lake anchovy (Coilia ectenes) and icefish (Neosalanx taihuensis), while Lake Donghu was dominated by phytoplanktivorous carps. Due to low biodiversity, catch MTL of these two lakes showed no significant change before and after 1985. Both fisheries-based and human activities-based drivers influenced the structure and catch MTL of fisheries in Chinese freshwater lakes.

Capture Fisheries Monitoring in the Lower Mekong Basin, by Ngor Peng Bun (The Kingdom of Cambodia), Peter Degen, & So Nam

Inland fisheries of the Mekong River Basin are amongst the largest fisheries in the world. Around 1,100 fish species are estimated in the basin, of which about 850 freshwater fish species have been recorded. Fisheries in the Lower Mekong Basin (LMB) produce annually about 3.9 million tonnes, of which about 2.3 million tonnes are from capture fisheries. The annual economic value of the fisheries is estimated up to US$7.0 billion. The Fisheries Programme (FP) of Mekong River Commission (MRC) aims at coordinated and sustainable development, utilisation, management, and conservation of the fisheries of the Mekong Basin by aiding its member countries to develop and implement sustainable fisheries management and development. FP has been supporting monitoring of fish abundance and diversity since the mid-1990s. These monitoring activities involve the recording of fish catches, fish species diversity, and fish larvae density. Key findings from the Mekong fisheries monitoring explain seasonal changes in the use of fishing gears in terms of type, size, and habitat. Trends in catch rate and catch by species, species abundance, and diversity are analysed and the relationship between fish catch and hydrology for specific fisheries is investigated. Likewise, transboundary migration of key species is examined using available fisheries monitoring data and existing studies in the region. Potential threats to the Mekong fisheries are discussed. The findings are important to better understand status and trends of capture fisheries in LMB and contribute to the assessment of the impacts from water management and basin development activities on fisheries.

Lee Trap Fisheries Monitoring in Southern Lao PDR, by Douangkham Singhanouvong (The Lao People’s Democratic Republic)

Important fish migrations take place in the Lower Mekong River of southern Lao PDR during the dry and wet season months. The riparian communities are aware of these movements and target a large number of species using a wide range of fishing gear. The objectives of the research were to identify the main migratory species, the timing, fish production, direction, purpose, main influencing factors, and the change in magnitude of migration between years. Research into the wet-season movements has been carried out from 2007 to 2013 in one rocky channel (Hoo Som Yai) at the Great Fault Line (Khong district) with support by Fisheries Program of Mekong River Commision (MRC). The catch per unit effort (CPUE) data were recorded directly from fishers operating the Lee traps and measured water flow in Hoo Som Yai from late May to the end of September each year. The data  collected in the wet season from 2007 to 2013 showed the main wet season migrants come from the families Pangasidae , Siluridae catfish, and Cyprinidae. The white fish were the dominant species that passed to this channel and follow by grey fish and a few black fish. The seasonal total catch from 2007 to 2013 varied depending on water flows. The rainfall and water level were perhaps the main factors affecting fish catches.

How National Household Consumption and Expenditure Surveys Can Improve Our Understanding of Fish Consumption Patterns within a Country and the Role of Inland Fisheries in Food Security and Nutrition within a Country, by Simon Funge-Smith (The Kingdom of Thailand)

Inland fisheries are a major source of food and food security throughout the Asian region, but are often overlooked in national statistics and in considerations of food security. Sixty-five percent of the reported global fish catch from inland fisheries is produced by 11 countries in the Asian region produce, but the quality of reporting of inland fisheries remains rather poor, reducing confidence in the data and preventing effective analysis at the sub-national level. Inland fisheries form a vital part of some rural people’s livelihoods and contributes a major source of protein, especially for vulnerable populations. For statistical purposes, these fish are all but invisible in official production figures, but the consumption of fish can be picked up by national household surveys. These surveys are carried out on a regular basis and to a high level of statistical accuracy, and can provide a wealth of information about consumption patterns and habits. This data can also play a vital role in the development of fisheries and natural resource policies that may have considerable impact on the most vulnerable segments of the population. Based on a review of fish and fish product consumption derived from national household consumption and expenditure surveys, this presentation reviews some of the results and the implications for the use of this type of national household consumption and expenditure survey for improving our understanding of inland fisheries and fish consumption. The presentation also covers some of the weaknesses in the use of surveys and how these may be improved to provide far more effective information in support of understanding inland fisheries and their role in food security.

New Estimation Method for Global Freshwater Fish Production, by Andrew M. Deines (The United States of America), David B. Bunnell, Mark W. Rogers, David H. Bennion, Whitney Woelmer, Colin N. Brooks, Amanda G. Grimm, Zachary Raymer, Michael J. Sachs, Robert A. Schuchman, & T. Douglas Beard

The direct assessment of freshwater fisheries production on the global scale is fundamentally hampered by the numerous and dispersed nature of lakes and the ubiquitous deficit of monitoring resources, even in developed countries. Our goal is to provide an alternative to the direct assessment of fisheries production based on ecological theory, empirical fisheries data sets, and remote sensing. Previous studies reveal a strong relationship between chlorophyll concentration and fisheries production across lakes, which we hypothesize can be used to develop predictive models of freshwater fishery production. By surveying published and gray literature, we compiled a database of over 700 lakes for which estimates of commercial, recreational, artisanal, subsistence, or fisheries-independent production estimates were available from around the world. We then used newly developed techniques in remote sensing of freshwater chlorophyll concentrations to develop predictive models of fisheries production. We used cross validation to demonstrate that the models make robust predictions for fish production in lakes across different types of fisheries, environmental, and climatic regions. These models could be used to supplement and “double-check” the results of direct assessments. Our long-term goal is to use these models to provide a novel assessment of freshwater fisheries production at the global scale using global distributions of remotely sensed chlorophyll data.

A Global Estimate of Theoretical Potential Annual Inland Capture Fisheries Production, by David Lymer (The Kingdom of Sweden), Felix Marttin, Gerd Marmulla, & Devin Bartley

Freshwater capture fisheries provide income and nutrition for hundreds of millions of people worldwide and the current global total catches calculated by FAO based on reported and estimated catch data are ~11.6 million tonnes from an officially reported global area of inland water that totals 4.6 million km². There is growing evidence that not all inland fisheries are captured in current statistical data collection systems, e.g., small-scale fisheries and recreational fisheries are to a large extent missing, and at least some of those being reported are evidently underreported. Also, recent estimates of global inland water areas are more than twice as high. Hence, both officially reported inland water areas and inland capture fisheries production figures are likely to be greatly underreported. To better reflect the true value of inland capture fisheries in the international discourse, we provide an estimate of a theoretical potential annual fisheries production from inland waters per continent and type of aquatic habitat based on recent estimates of global inland aquatic habitat areas and average yield measurements from these habitats. We estimate that the global theoretical potential annual fisheries production is on average 6.5 times higher than the official catch data submitted to FAO (between 3 to 11 times higher by continent). To get the statistics right would greatly improve the visibility of the importance of inland water capture fisheries for the food security of people, which should be better acknowledged in development policies, given the importance of food security in the development realm.

Poster Presentations

Posters are on display in the FAO library (ground flo0r) during all three days of the conference. Poster authors will be present with their posters during the poster session reception on Tuesday at 17:00.

Assessing Inland Fisheries in Remote Forest Streams: Evaluation of Participatory Approaches in the Western Ghats Freshwater Ecoregion, India, by Rajeev Raghavan Pichirikkat (The Republic of India) & Neelesh Dahanukar

Assessment of inland fisheries in monsoonal rivers is extremely challenging due to remote areas and habitats which are often inaccessible for routine research and monitoring. Collection of data in such demanding conditions requires alternate approaches, often involving participation of local fishers. The streams flowing through the Western Ghats in India is one such area, known for its unique assemblage of freshwater fish, which are threatened by several anthropogenic stressors. Open-access fisheries encompassing the food, ornamental, and sport sectors exist in the region, many of which target endangered species. Using participatory approaches, we assessed the sustainability of two contrasting fisheries targeting threatened species, the small-scale fishery of mahseer (Tor spp.) for subsistence and sale in village markets, and the unmanaged exploitation of redline torpedo barbs (Sahyadria sp.) for the international aquarium trade. Local fishers trained in collecting length measures provided monthly data for a period of one year. Random visits were made by the project team to the fishing sites to validate data collection techniques, assess quality of data entries, and provide technical help. Length-based approaches were used to assess growth and mortality parameters, and assess exploitation levels. At all but one fishing village, mahseers were subjected to overfishing with populations facing an imminent collapse, while overexploitation of the endangered redline torpedo barbs was observed at two collection sites. The study demonstrates the utility of participatory data collection in assessing the status of remotely located tropical small-scale inland fisheries, and provides evidence for the occurrence of overfishing in such systems.

Egyptian Nile River Fisheries Assessment with Special Reference to Tilapia Fishery, by Sahar F. Mehanna (The Arab Republic of Egypt)

The River Nile, stretching across half of Africa, flows northwards from the tropical mountains and forests of the Equator to the temperate Mediterranean Sea. The Nile River is the longest river in the world at 6,695 km (4,184 miles) long. The length of Nile in the Egyptian borders is about 1,532 km. North of Cairo, the Nile splits into two branches (or distributaries) that feed the Mediterranean: the Rosetta Branch to the west and the Demietta Branch to the east, forming the Nile Delta. The heavy impacts of fishing industry, the introduction of Nile perch and freshwater crayfish, unregistered fishermen and unrecorded catch, as well as the pollution, are the main problems facing the Nile ecosystem. Nile fisheries play an important role in the Egyptian economy where it provides about 10% of harvested fish in Egypt (1990-2013). Tilapias form the major part of the Nile production and constitute about 33% of its total fish production. The present study is done to evaluate the impact of fishing effort on the Nile and tilapia production through fitting a biomass-based model to the catch per unit effort (CPUE) indices to estimate some applicable reference points needed for proposing some regulatory measures for Nile fisheries management.

Size Structure and Sex Maturity Variations on Nile Perch (Lates niloticus L.) in Lake Victoria, by Enock W. Mlaponi (The United Republic of Tanzania), Paul A. M. Van Zwieten, Robert Kayanda, & Charles Mashafi

Growth in fish is indeterminate and their life-history characteristics, such as growth, maturity and mortality, vary according to environmental influences. Following the resource monitoring surveys conducted in Lake Victoria, there was some uncertainty about the length at first maturity in the stock of Nile perch Lates niloticus compared to the 1980s state. In 2008, some scientists reported the length at first maturity had already fallen to between 50 and 55 cm in both males and females from 54 cm for males and 77 cm for females. However, analysis using solver software from the data collected from trawl surveys and two fish processing factories in Tanzania shows there is no significant different (P > 0.05) between previous and current length at the first maturity in the stock of Nile perch where the maturity stage of Nile perch is ranging from 50-60 TL cm for males and 70-80 TL cm for females. These imply that length at first maturity has not decreased as much as it might have been expected to have done. This suggests that the proportions of spawning stock of Nile perch in Lake Victoria are still there and need to be protected.

Composition, Biomass Distribution, and Population Structure of the Fish Stocks in Lake Victoria, Tanzania Side, by Enock W. Mlaponi (The United Republic of Tanzania), Robert Kayanda, B.S. Msuku, & Charles Mashafi

Until the 1970s, Lake Victoria had a multi-species fishery dominated by the tilapiine and haplochromine cichlids. There were important subsidiary fisheries for more than 20 genera of non-cichlid fishes, including catfishes, lung fish, and Labeovictorianus. Stocks of most of these species declined and others disappeared following the introduction of four tilapiines and Nile perch (Latesniloticus) during the 1950s. Since then the commercial fishery in Lake Victoria has been dominated by the Nile perch, Nile tilapia (Oreochromis niloticus) and the native cyprinid species, Rastrineobolaargentea (Dagaa). A number of fish processing plants have been constructed along the shores of Lake Victoria. A series of fish stock assessment surveys were conducted since the first survey in Lake Victoria by Graham in 1929 which revealed a dominance of Haplochromine cichlids. During 1980s, subsequent stock assessment programs were undertaken to generate information on the status of the fish stocks to guide the increased investment interest in the export-oriented fishery. Further fish stock assessment was carried out between 1997-2001 and 2002-2007 using trawling and lakewide hydroacoustic methods to study the seasonal changes in the fish stocks. There are indications that the fishery yield declined from 315,249 tons in 1990s to 270,690 tons in 2006 but there is also a declining trend in lakewide standing stock of Nile perch from 1,936,677 tons (1999), 1,239,961 tons (2001), and 751,523 tons (2006) to 354,633 tons (2009) while the fishing effort in the Tanzanian sector of Lake Victoria increased.

Does Variation in Electrofishing Catch-Per-Unit-Effort Reflect Variation in the Abundance of Fishes? by John H. Chick (The United States of America), C. R. Dolan, & G. G. Sass

Biological assessment of fisheries resources requires sampling methods that can accurately gauge status and trends of fish populations. Assessing the efficacy of a method requires information on the precision of the sampling method (statistical power), and the accuracy of the method (how well the data reflect abundance). Although evaluation of statistical power for fisheries data has become more common in recent years, studies that specifically test for a relationship between sampling data and the actual abundance of fishes (catchability relationship) remain rare. We evaluated catchability relationships for 17 fish species in 10 backwater lakes of the Mississippi and Illinois rivers sampled with boat electrofishing with pulsed-DC current as conducted for the Long Term Resource Monitoring Program (LTRMP), a component of the Upper Mississippi River Restoration Environmental Management Program. Catch-per-unit-effort data from electrofishing samples and estimates of fish abundance (density and wet mass) from rotenone samples were collected in each backwater lake. Eleven species had significant catchability relationships for density or wet mass. This is the first evidence of a significant catchability relationship for pulsed-DC boat electrofishing for these species, although they are all commonly sampled with this method. Electrofishing proved to be consistently biased toward larger individuals within a species, but restricting analyses to stock size or larger individuals did not improve catchability relationships. Combining the results of this study with an earlier power analysis shows that although electrofishing is an accurate method for several species, it can be inaccurate for others even when statistical power is high.

Current State of the Inland Fisheries in Mexico, by Felipe Amezcua (The United Mexican States) & Claire Coiraton

Mexico has over 5,100,000 hectares of inland water bodies comprised of deltas, rivers, streams, lakes, lagoons, ponds, dams, and reservoirs, among others. In most of these water bodies,important artisanal fishing activity has developed; in the year 2010, a total of 129,627 tonnes were landed from inland fisheries, which represented 8% of the total fishing catch of Mexico. The most important species in terms of economic revenue were catfish, carp, tilapia, cichlids, trout, bass, and shortfins. The Mexican government acknowledges that inland fisheries are essential to acquire food sovereignty, and its management is a priority for the development of this activity. Proper management plans are necessary to develope sustainable inland fisheries. However, inland fisheries in Mexico have several issues that need to be resolved if proper management is to be acquired. At present, the most important inland fisheries are from introduced species, such as tilapia, trout, and carp, and little or no research is being undertaken on native species that could be commercially exploited. Fisheries research in Mexico has focused on marine ecosystems, and little or no research has been undertaken in inland fisheries; only one institute in the whole country specializes in these fisheries. There are no norms and regulations for these water bodies, and the statistics on landings are poorly recorded. Therefore the available information is inaccurate and there are signs of over exploitation in most of these systems.The fishers are usually poor and with limited access to financing programs.

Assessing Nursery Habitat for Sabalo (Prochilodus lineatus) in the Parana River Delta, Argentina with Modis-Evi Imagery, by Priscilla G. Minotti (The Argentine Republic) & P. Kandus

Assessing the potential recruitment of commercial fish in large floodplain rivers is complex due to hydrological variability and habitat heterogeneity. As the abundance of eggs and larvae are quantified in the channels, yearlings and juveniles must be sampled in wetland environments with different degrees of connection and permanence of water. The aim of this work is to present a satellite-based indicator of the available nursery habitat for sabalo (Prochilodus lineatus), using the extent and duration of the flooded area during the breeding season as a “proxy” to predict species production and future yield. We used EVI images obtained from the standardized MOD13Q1 product (MODIS-Terra, 16-day temporal composite 250 m pixel) between 2000 and 2013. We conducted an extensive sampling during the 2008-2009 breeding season, covering different types of wetlands. Pixel EVI values were extracted from images corresponding to the same sampling period using GIS software. An EVI threshold was calculated to represent suitable and unsuitable water cover for breeding environments. For each breeding season, we calculated the frequency of suitable habitat on a per pixel basis. The relationship between satellite-estimated nursery area and catch levels mentioned in reports and fishery statistics is discussed. The application of satellite-based ecohydrological indicators allows the monitoring of available nursery areas in large floodplain rivers and can provide criteria to adjust fisheries management accordingly.

Assessment of Lake Trout Egg Fatty Acid Signatures in the Great Lakes: Reflection of Variability in Prey Assemblages, by Sergiusz J. Czesny (The United States of America), Jacques Rinchard, & Dale  Hanson

Prey fish assemblages vary substantially among the Great Lakes, as each ecosystem constitutes an inimitable community and has management strategies adapted to the particulars of its fisheries and conservation needs. Within each system there are also considerable temporal fluctuations in prey assemblage as native and nonnative species undergo sizable abundance oscillations. Thus the nutrients available to top predators utilizing a dynamic prey base vary spatiotemporally. Predators’ tissues, including eggs, can reflect such changes in nutrient intake. In the Great Lakes, lake trout populations have been suppressed by overharvest and sea lamprey predation while lack of their recovery has been linked to prey-driven nutrient deficiencies. We assessed fatty acid signatures of lake trout eggs from multiple Great Lakes in a single year and from Lake Michigan in multiple years to document the amount of variability one can expect on the spatial and temporal scales, respectively. Eggs from various lakes could be readily distinguished based on their fatty acid signatures, although the degree of difference varied among systems. Within Lake Michigan, lake trout egg fatty acid signatures were also variable and grouped based on year of sampling. These results are indicative of large variation in lake trout egg fatty acid signatures among and within the Great Lakes. We will discuss these results in the context of fluctuating prey assemblages and reflect on potential ramifications for lake trout egg quality as well as implications for successful restoration of this valuable native top predator.

Conservation of the Migratory Stocks of Giant River Prawn Macrobrachium rosenbergii in Vembana Lake, Kerala, India, by K. R. Salin (The Kingdom of Thailand)

Vembanad Lake in the southern Indian State of Kerala with its confluent rivers is home to the giant river prawn Macrobrachium rosenbergii. Although the fishery was once abundant, contributing substantially to the livelihood of dependent communities, several factors such as excessive fishing pressure, obstruction of the water flow from the estuarine portion of the lake into Arabian Sea by construction of a barrage, and environmental degradation have led to recent declines. What makes the prawn more vulnerable is the peak fishing season for berried females and blue-clawed males coinciding with the two monsoon seasons (June and October, until April) and the associated breeding migration of prawns. We studied the population structure and availability of berried females of M. rosenbergii in relation to monsoon and water quality parameters continuously for a period of two years in one of the major landing centres, which indicated a significant seasonal variation in sex ratio. Studies on the migratory patterns of M. rosenbergii revealed that they make short distance migrations ranging from 4 to 15 kilometres upstream into the river. Berried females in the catch are often marketed by discounting egg weight or after the eggs are removed before weighing prawns. There has also been an organized collection of berried females as broodstock for prawn hatcheries, which seems to have affected their recruitment to wild population. A simple conservation strategy has been suggested here to keep the egg-carrying females in secured cage enclosures, allowing the eggs to hatch before they are marketed.

Population Studies and Abundance of Freshwater Fishes of Two Major Reservoirs in Ondo State, Nigeria, by Olaronke Olawusi-Peters , Oluayo Anthony Bello-Olusoji (The Federal Republic of Nigeria), Kemi F. Aremu, & Omobolanie R. Adeboye

Globally, efforts are geared toward increase in fish production for food security, improved livelihood of the rural dwellers, and alleviating poverty. Fish seasonal abundance and population dynamics from two major reservoirs constructed primarily for domestic use in the major cities and towns of Ondo State, Nigeria, which also provide fish for local consumption, were examined between 2010 and 2012. The long-term changes in each reservoir’s productivity, in relation to fishes composition and year of construction of each reservoir (49 and 6 years old), were assessed. The pre-stocking assessment of fish in the newly constructed reservoir was determined. The degree of change between years in total abundance, numbers of taxa, and community composition varied considerably between the two reservoirs. The study revealed 16 fish species belonging to 10 families. These include Cichlidae (59.8%), which constituted the dominant fish families in the two reservoirs, with Oreochromis niloticus (47.2%) being the most abundant species. Hepsetidae (0.4%) and Cyprinidae (0.4%) were the least abundant. Other families include Characidae (4.0%), Clariidae (8.1%), Malapteruridae (1.2%), Mormyridae (13.0%), Channidae (7.0%), Clupeidae (1.2%), and Mochokidae (4.9%). The morphometric features of the two most abundant fish species (Oreochromis niloticus and Clarias gariepinus) were determined, such as the weight, total length, standard length, and head length. Some species of freshwater shellfish were observed, with five families in the old and three families in the new reservoirs. A positive correlation (R2=0.9227) was obtained for samples collected from the old reservoir, those from the new reservoir gave a contrasting value (R2=0.201).

Between the Canoe and the Laptop: Fish Sampling in the Upper Rio Negro, by Pieter-Jan van der Veld (The Federative Republic of Brazil)

When we talk about fish shortages, we normally think of problems caused by big scale fishing for the market. It is, however, also a problem for the subsistence fisherman of the Indigenous Peoples of the Upper Rio Negro, who live far from any market or big scale fishery but nonetheless see their livelihood threatened by a diminishing fish supply. To understand the reasons for this shortage, the Instituto Socioambiental (Socio-environmental Institute) – ISA, a Brazilian NGO, together with its Indigenous partner organizations, started a series of initiatives and researches. In this presentation, some of these initiatives will be briefly explained but the focus of the presentation will be the fishery survey of the Tiquie River.

Collaborative Research of Mekong River Fisheries, by David Allen Hewitt, Ut Vu Ngoc, Matthew E. Andersen, John W. Beeman (The United States of America), Harmony C. Patricio, Shaara M. Ainsley, Doug B. Demko, & Craig Conzelmann

The Mekong River in Southeast Asia supports the world’s most productive and diverse fish assemblage and inland fishery, providing food and income opportunities to over 60 million people. Recent appraisals have anticipated substantial effects of impending infrastructure development and climate change on river hydrology and productivity. Such changes could compromise the ability of the Mekong River ecosystem to continue to provide food security to riparian users and threaten the river’s rich biodiversity. Managing for change in the transboundary Lower Mekong River Basin will require considerable information about the river’s fish assemblage. The short-term nature of historic studies and the highly migratory life history of many of the river’s fishes create special challenges to assembling information that can support informed decision making. The U.S. Geological Survey and FISHBIO, with additional support from the U.S. State Department, have developed the MFN Data Bank, an online data portal for fish and fisheries information from the Mekong River, and the Mekong Fish Network that supports scientific communications and local capacity building. A project with researchers at Can Tho University has begun testing standard sampling methods using trawls and gill nets in the Mekong Delta portion of the basin. Initial research questions are focused on seasonal changes in catches, gear selectivity, and length-weight relationships for selected species of economic or conservation interest. Broader implementation of shared sampling methods through the MFN Data Bank could increase understanding of fish diversity and resources at larger scales than has previously been possible.

The Artisanal Freshwater Crab Fishery in Lake Atitlán, Guatemala: An Overview, by Ingo S. Wehrtmann  (The Republic of Costa Rica) & Silvia L. Batres-Ãlvarez

True freshwater crabs are an important component of the fauna of freshwater ecosystems in Central America and especially decapod crustaceans may form part of the diet of the rural population. As far as we know, the only freshwater crab fishery in the Americas takes place in Lake Atitlán, located in the highlands of Guatemala. Here we provide background information for a better understanding of the social setting of this artisanal fishery, and compile available fishery-biological data. Fishermen usually dedicate three days per week to fishing and are almost exclusively men at an age between 30-40 years, most of them with decades of fishing experience. Until recently, local and regional fishery agencies assumed erroneously that they were dealing with a single-species fishery. However, our recent study revealed that at least two different species of two different pseudothelphusid genera are harvested: Potamocarcinus magnus and Raddaus bocourti. These true freshwater crabs are caught mainly with baited traps, and fishermen use simple wooden boats (locally called “cayuco”). Official catch data do not exist, but our study revealed that fishermen captured around 177 crabs per month. The crab fishing activities are influenced by different environmental and anthropogenic factors (e.g., seasonal winds, introduced fish species, increasing water pollution with cyanobacterial blooms). So far, not even basic information is available about the ecology of the harvested crab species, which impedes the development of adequate management measures. We present a proposal on how to increase the local and regional awareness and appreciation for this unique inland fishery resource.

Fishermen’s Ecological Knowledge on Fish Reproduction: Contribution to Fisheries Management in Amazonia, by Fabiana Calacina da Cunha (The Federative Republic of Brazil), Maria G. M. Soares, Luiza Prestes, & Alexandro C. Florentino

The ethnoecology is important to obtain information about the conservation of fishery resources, especially for fisheries management in protected areas. The ecological knowledge of fishermen in the National Forest of Amapá (FLONA-AP), Amapá state, Amazonia, Brazil, was studied to obtain information related to the period and to the place of spawning fish.This information is important for defining actions for more appropriate fisheries management, such as closed system. The information was validated using scientific data. Three species of fish, pacu curupeté Tometes trilobatus, trairão Hoplias aimara, and mandubé Ageneiosus inermis, were used in interviews with artisanal fishermen (n = 63). Also, experimental fishing was carried out for the gonadal development record.The knowledge of fishermen on the breeding period was consistent with data obtained from fisheries, i.e., reproduction occurs during winter (January-May), marked by high rainfall (862-323 mm rainfall) and quotas River (478-520 cm) that floods large marginal areas. The spawning grounds of these fishes were most cited by fishermen as “Baixão” (area of ​​flooded forest near the creek).T. trilobatus also spawn in areas of current in the river and creeks and H. aimara in streams. Unfortunately, there are no scientific data on nesting sites for comparison. We conclude that ethnoecology provides important information for fisheries management because it allows us not only to identify the period of breeding, important for the correct definition of closed season, but also indicates spawning grounds locations as priority areas for conservation.

Role for Hatcheries in Addressing Fish Ecological Resilience: A Systematic Review Approach, by Mohd Ammarr Bin Mohd Aripin (Malaysia) & M. A. Rudd

Over the past century there has been growing interest in artificial fish propagation, driven by concerns about declining of fish populations and species. Hatcheries, or artificial fish propagation and captive breeding, are assuming an important role to restore fish stocks that have been depleted. A systematic review was conducted to prove the ability of hatcheries in addressing fish ecological resilience. The primary question for this systematic review is, “Are artificial fish propagation and restocking or restoration activities capable of increasing fish ecological resilience?” The study focused primarily on studies that report on the empirical evidence of support among scientists or authors regarding the capability of artificial fish propagation and restocking or restoration activities in increasing fish ecological resilience.

Inland Fisheries in India: Status, Challenges, and Opportunities, by Rajeev Raghavan Pichirikkat (The Republic of India) & Appukuttan Bijukumar

Close to 1.5 million tons of fish were caught from the inland waters of India in the year 2012, an increase of 92% over a decade. While this marked increase in production could be linked to an actual increase in harvests,  or an overestimation or improvement in data gathering and reporting, the inland capture fisheries sector in the country has been poorly managed. The greater emphasis on developing aquaculture, while ignoring sustainable management of capture fisheries, is evident from the shifting baselines of catch data, both at the national level, and for individual water bodies, including the River Ganges. Throughout the country, inland fisheries encompassing the food, ornamental, and recreational sectors suffer from “open access” and “common property” paradigms, with potentially serious biodiversity and livelihood consequences. Biological resource use (via inland capture fisheries) is now the second greatest threat to freshwater fishes in the biodiversity hotspots of India, with many threatened species subjected to overfishing. There have been little or no successful efforts to design adequate institutional and governance mechanisms supporting the needs of inland fishers, while the existing relationship between the formal institutions and inland fishing communities lacks mutual trust. The sector, however, provides extensive opportunities to capitalise on the rich and diversified natural capital, as small-scale fisheries continues to provide nutritional and livelihood security to the rural populace. This contribution proposes strategies for improved integrated management of inland fisheries through an ecosystem approach, with the involvement of traditional fish communities and through rehabilitation of freshwater ecosystems.

Population Demography of Beleophthalmus boddarti (Gobiidae) in Mekong Delta, VietNam, by Dinh Minh Quang (The Socialist Republic of Viet Nam)

The population demography of the mudskipper Boleophthalmus boddarti (Gobiidae), a commercially important fish in Southeast Asia, was carried out along the mudflat in the Mekong Delta, Viet Nam, from March 2013 to February 2014. A total of 1,702 individuals collected by a deep net with 15-mm mesh size were used to estimate some basic parameters of its population biology. The total length of this mudskipper was measured after determining the sex based on an external feature (genital papilla), and its total length ranged from 8.0 to 16.0 cm. The sex ratio of B. boddarti was nearly 1:1, and the parameters of von Bertalanffy growth function fitting to the length frequency data were L∞= 16.8 cm, K = 0.8 yr-1. There were two recruitment peaks separated by an interval of 6 months. The fishing mortality (F = 0.21 yr-1) and natural mortality (M = 1.87 yr-1) amounted for 10.1% and 89.9% of the total mortality (Z = 2.08/y), respectively. Relative yield-per-recruit and biomass-per-recruit analyses gave Emax = 0.358, E0.1 = 0.259, and E0.5 = 0.232. This study reported that growth constant (K) of this mudskipper was high, which could be potential for future aquaculture. Moreover, this finding also showed that the fish stock rate was slightly lower than that of potential exploitation, but the mesh size was slightly small, suggesting that the local government should require fishermen to change the mesh size of gill net for future sustainable exploitation and development.

Global Deployment of Electrofishing and Electric Fish Barrier Technology in the Management of Inland Fisheries Resources, by Martin O’Farrell (Ireland)Carl V. Burger, Patrick Cooney, &  Aaron Murphy

Inland fisheries managers and researchers throughout the world are dependent on the availability of sampling tools which allow them to sample fish in rivers and lakes non-destructively. Electrofishing equipment has been manufactured on a commercial scale since the 1960s. The global sales patterns of a leading manufacturer are reviewed in terms of the characteristics of battery-powered and generator-powered shore-based and boat-mounted electrofishing equipment, the country / continent of purchase, and the intended use of the equipment. A review of communications with purchasers and with potential purchasers who failed to follow through on planned purchases because of financial reasons is also included. Electric fish barriers have also been manufactured on a commercial scale since the 1960s. The development of the graduated field fish barrier (GFFB) in the 1980s advanced this technology in terms of reliability and effectiveness. To date more than 60 installations have been completed in North America and in Europe, protecting fish on industrialised rivers and preventing the range expansion of invasive fish species. This paper assesses the contribution of electrofishing technology to the biological assessment of fish populations throughout the world and also looks at how a complementary technology in the form of the graduated field fish barrier enhances inland fisheries resource conservation. The contribution of electrofishing and electric fish barrier technologies to inland fisheries conservation efforts is reviewed and their potential contribution in those areas of the globe, e.g., Africa and Asia, where they are not currently deployed to any significant extent, is explored.

Recovery of Fish Fauna in the Large Lowland Warta River, Polandby Andrzej Kruk (The Republic of Poland), Michal Cieplucha, Grzegorz Zieba, Mariusz Tszydel, Lidia Marszal, Szymon Tybulczuk, Dagmara Blonska, Dariusz Pietraszewski, Bartosz Janic, Wanda Galicka, & Tadeusz Penczak

The Warta River is a tributary of the Odra (Oder) River. It is 795.2 km long. In 1986, the large Jeziorsko dam reservoir was constructed in 306 km of its course. Unified electrocatches of fish and lampreys have been performed along the Warta River since the 1960s. During the last sampling, in 2011-2012, the weakest human pressure was reported for the upstream and lower courses, which resulted in higher numbers of species significantly associated with them and higher species richness. Ichthyofauna in the middle course of the river was in a worse condition due to the strong destabilizing upstream impact of the Jeziorsko dam reservoir, large amounts of wastewater input into the river, and the lack of unpolluted tributaries that could serve as sources of recolonizers. In comparison with the previous sampling occasions (in 1963-66, 1986-88, and 1996-98), a significant increase in species richness was recorded. Significant declines in the stability of occurrence, abundance, or biomass of particular species were rare and related mainly to European eel (a migratory species). The highest numbers of significant increases in the above mentioned population parameters in particular river sections were recorded for burbot, chub, dace, ide, gudgeon, bleak, bitterling, perch, and spined loach. The previous strong negative trend (declines in rheophils, increase in the dominance of roach and perch) was reversed. Further recovery of fish fauna is largely dependent on maintaining good water quality and restoration of the diversity of microhabitats and river continuity in its lateral and longitudinal profiles.