Valuing freshwater salmon habitat on the west coast of Canada

Changes in land use can potentially reduce the quality of fish habitat and affect the economic value of commercial and sport fisheries that rely on the affected stocks. Parks and protected areas that restrict land-use activities provide benefits, such as ecosystem services, in addition to recreation and preservation of wildlife. Placing values on these other benefits of protected areas poses a major challenge for land-use planning. In this paper, we present a framework for valuing benefits for fisheries from protecting areas from degradation, using the example of the Strait of Georgia coho salmon fishery in southern British Columbia, Canada. Our study improves upon previous methods used to value fish habitat in two major respects. First, we use a bioeconomic model of the coho fishery to derive estimates of value that are consistent with economic theory. Second, we estimate the value of changing the quality of fish habitat by using empirical analyses to link fish population dynamics with indices of land use in surrounding watersheds. In our example, we estimated that the value of protecting habitat ecosystem services is C$0.93 to C$2.63 per ha of drainage basin or about C$1322 to C$7010 per km of salmon stream length (C$1.00=US$0.71). Sensitivity analyses suggest that these values are relatively robust to different assumptions, and if anything, are likely to be minimum estimates. Thus, when comparing alternative uses of land, managers should consider ecosystem services from maintaining habitat for productive fish populations along with other benefits of protected areas.     

BIOECONOMIC ANALYSIS OF SELECTED CONSERVATION PRACTICES ON SOIL EROSION AND FRESHWATER FISHERIES1

ABSTRACT: Farmers can generate environmental benefits (improved water quality and fisheries and wildlife habitat), but they may not be able to quantify them. Furthermore, farmers may reduce their incomes from managing lands to produce these positive externalities but receive little monetary compensation in return. This study simulated the relationship between agricultural practices, water quality, fish responses to suspended sediment and farm income within two small watersheds, one of a cool water stream and one of a warm water stream. Using the Agricultural Drainage and Pesticide Transport (ADAPT) model, this study related best management practices (BMPs) to calculated instream suspended sediment concentrations by estimating sediment delivery, runoff, base flow, and streambank erosion to quantify the effects of suspended sediment exposure on fish communities. By implementing selected BMPs in each watershed, annual net farm income declined $18,000 to $28,000 (1 to 3 percent) from previous levels. “Lethal” fish events from suspended sediments in the cool water watershed decreased by 60 percent as conservation tillage and riparian buffers increased. Despite reducing suspended sediments by 25 percent, BMPs in the warm water watershed did not reduce the negative response of the fisheries. Differences in responses (physical and biological) between watersheds highlight potential gains in economic efficiency by targeting BMPs or by offering performance based “green payments.”     

ASSESSING ENVIRONMENTAL EFFECTS OF SEVERE SUSTAINED DROUGHT1

ABSTRACT: Evaluation criteria for reservoir and stream resources were developed to provide decision makers with feedback on environmental consequences of water allocation decisions under conditions of severe sustained drought within the Colorado River Basin by using the AZCOL gaming simulation model. Seven categories of flow dependent resources were identified which highlight resource states associated with reservoirs or river reaches within the AZCOL model. AZCOL directly simulates impact of water management decisions on five resource categories: threatened, endangered or sensitive fish; native nonlisted fish; wetland and riparian elements; national or state wildlife refuges; and hatcheries or other flow dependent facilities. Two additional categories - cold and warm water sport fish - are not modeled explicitly but are incorporated in the evaluation of monetary benefits from recreation on Colorado River waters. Each resource category was characterized at each time step in the simulation according to one of four environmental states: stable, threatened, endangered, or extirpated. Changes in resource states were modeled by time and flow-dependent decision criteria tied to either reservoir level or stream flows within the AZCOL model structure. Gaming results using the AZCOL model indicate environmental impacts would be substantial and that water allocation decisions directly impacted environmental resource states.     

Fish Assemblage Responses to Water Withdrawals and Water Supply Reservoirs in Piedmont Streams

Understanding effects of flow alteration on stream biota is essential to developing ecologically sustainable water supply strategies. We evaluated effects of altering flows via surface water withdrawals and instream reservoirs on stream fish assemblages, and compared effects with other hypothesized drivers of species richness and assemblage composition. We sampled fishes during three years in 28 streams used for municipal water supply in the Piedmont region of Georgia, U.S.A. Study sites had permitted average withdrawal rates that ranged from < 0.05 to > 13 times the stream’s seven-day, ten-year recurrence low flow (7Q10), and were located directly downstream either from a water supply reservoir or from a withdrawal taken from an unimpounded stream. Ordination analysis of catch data showed a shift in assemblage composition at reservoir sites corresponding to dominance by habitat generalist species. Richness of fluvial specialists averaged about 3 fewer species downstream from reservoirs, and also declined as permitted withdrawal rate increased above about 0.5 to one 7Q10-equivalent of water. Reservoir presence and withdrawal rate, along with drainage area, accounted for 70% of the among-site variance in fluvial specialist richness and were better predictor variables than percent of the catchment in urban land use or average streambed sediment size. Increasing withdrawal rate also increased the odds that a site’s Index of Biotic Integrity score fell below a regulatory threshold indicating biological impairment. Estimates of reservoir and withdrawal effects on stream biota could be used in predictive landscape models to support adaptive water supply planning intended to meet societal needs while conserving biological resources.     

A DECISION SUPPORT SYSTEM TO MANAGE SUMMER STREAM TEMPERATURES1

ABSTRACT: Warm summer stream temperatures due to low flows and high air temperatures are a critical water quality problem in many western United States river basins because they impact threatened fish species’habitat. One way to alleviate this problem is for local and federal organizations to purchase water rights to be used to increase flows, hence decrease temperatures. Presented is a Decision Support System (DSS) that can be used in an operations mode to effectively use water acquired to mitigate warm stream temperatures. The DSS uses a statistical model for predicting daily stream temperatures and a rule‐based module to compute reservoir releases. Water releases are calculated to meet fish habitat temperature targets based on the predicted stream temperature and a user specified confidence of the temperature predictions. Strategies that enable effective use of a limited amount of water throughout the season have also been incorporated in the DSS. The utility of the DSS is demonstrated by an example application to the Truckee River near Reno, Nevada, using hypothetical operating policy and 1988 through 1994 inflows. Results indicate that the DSS could substantially reduce the number of target temperature violations (i.e., stream temperatures exceeding the target temperature levels detrimental to fish habitat).     

ENERGY,ENVIRONMENTAL, AND ECONOMIC IMPLICATIONS OF SOME RECENT ALBERTA WATER RESOURCES PROJECTS1

ABSTRACT: Most of us are aware, or feel we are aware, of the impacts of major water resources projects on our lives. “Dam-lovers” note the life-saving flood-risk reduction and recreational benefits of a proposed reservoir, while “dam-haters” bemoan the future drowning out of the wildlife habitat of its river valley, and the recreational disbenefits to stream (as opposed to lake) fishermen. Water supply projects can often be given such a revered status, assuming the “obvious” tenet that water, air, food, and shelter are basic requirements of decent living, that the economic viability of the project may not even be assessed. Water resources planners are supposed to impartially weigh the environmental and economic benefits, and especially now, the energy implications of all proposed water projects, but many times the partial views of political or public advocates may be hard to ignore. The assumptions used in the planning of four recent water projects in the Province of Alberta will be presented and some revisions suggested which materially affect their Benefit/Cost ratios. In one project that is still in the public hearing stage, the economic analysis will be revealed, indicating that the original B/C ratio of about 1.6:1 might be more realistically placed at 0.6:1. In another project just completed, the apparent lack of an economic or energy analysis that has resulted in a perpetual and unnecessary energy load on the province, will be described.     

THE IMPORTANCE OF BEAVER TO WETLAND HABITATS AND WATERFOWL IN WYOMING1

ABSTRACT: Beaver (Castor canadensis) are habitat‐modifying keystone species, and their activities broadly influence many other plants and animals. Beaver are especially important to waterfowl in the western U.S. where riparian and wetland habitats comprise less than 2 percent of the landscape yet provide habitat for greater than 80 percent of wildlife species. Wyoming is currently ranked sixth of the 50 states in the size of its breeding waterfowl population, and beaver ponds may play a significant role in providing habitat for these birds. The objectives of this research were to: (1) identify streams in Wyoming where beaver are currently present, extirpated, or used to manage riparian habitat; (2) identify areas where beaver could be relocated to create wetlands and improve riparian habitat; (3) compare wetland surface areas between areas that have beaver with those that did not; and (4) compare waterfowl numbers in areas with and without beaver. Using a survey of 125 land managers in Wyoming, we found that beaver have been removed from 23 percent (6,497 kin) of the streams for which managers had direct knowledge (28,297 kin). The same managers estimated that there are over 3,500 km of streams where beaver could improve habitat conditions. The riparian width in streams with beaver ponds averaged 33.9 m (95 percent CI = 25.1–42.7 m) in contrast to 10.5 m (CI = 8.6–12.4 m) in streams without beaver. During waterfowl surveys we counted 7.5 ducks/km (CI = O.9–14.4 ducks/kin) of stream in areas with beaver ponds and only O.1 ducks/km (no CIs calculated) of stream in similar areas without beaver present. Beginning in 1994, we restored beaver to 14 streams throughout Wyoming in an effort to create wetlands and improve riparian habitat. Waterfowl have been quick to respond to these important habitats. We feel that beaver restoration and management can be used to improve habitat in drainages where conflicts with other land uses are minimal.     

THE BUREAU OF RECLAMATION'S ROLE IN AMERICA'S GROWTH1

ABSTRACT. The Bureau of Reclamation was created to implement the Reclamation Act of 1902 and subsequent legislation to conserve and develop the water resources of the western states for maximum efficient use. This has been accomplished by the planning and construction of major multiple use projects which now supply water to approximately eight million acres of land which annually produce 52 million tons of food and fiber with a gross crop value of approximately $2 billion. Fifteen million people are served with municipal and industrial water supplies and hydroelectric power from Bureau projects now returns $160 million annually to the Treasury. Flood control, recreation, and fish and wildlife enhancement are other major benefits. The Bureau of Reclamation is now undertaking a Westwide Survey of water resources and of the needs of the future which is more far-reaching than anything heretofore accomplished. The information accumulated during this ten-year survey will determine whether there is a necessity for consideration of major interbasin transfer of water supply.     

Regulated flushing in a gravel-bed river for channel habitat maintenance: A Trinity River fisheries case study

The operation of Trinity and Lewiston Dams on the Trinity River in northern California in the United States, combined with severe watershed erosion, has jeopardized the existence of prime salmonid fisheries. Extreme streamflow depletion and stream sedimentation below Lewiston have resulted in heavy accumulation of coarse sediment on riffle gravel and filling of streambed pools, causing the destruction of spawning, nursery, and overwintering habitat for prized chinook salmon (Salmo gairdnerii) and steelhead trout (Oncorhynchus tschawytscha). Proposals to restore and maintain the degraded habitat include controlled one-time remedial peak flows or annual maintenance peak flows designed to flush the spawning gravel and scour the banks, deltas, and pools. The criteria for effective channel restoration or maintenance by streambed flushing and scouring are examined here, as well as the mechanics involved.The liabilities of releasing mammoth scouring-flushing flows approximating the magnitude that preceded reservoir construction make this option unviable. The resulting damage to fish habitat established under the postproject streamflow regime, as well as damage to human settlements in the floodplain, would be unacceptable, as would the opportunity costs to hydroelectric and irrigation water users. The technical feasibility of annual maintenance flushing flows depends upon associated mechanical and structural measures, particularly instream maintenance dredging of deep pools and construction of a sediment control dam on a tributary where watershed erosion is extreme. The cost effectiveness of a sediment dam with a limited useful economic life, combined with perpetual maintenance dredging, is questionable.     

Restoration of a Canadian Prairie Wetland with Agricultural and Municipal Wastewater

3 /day (800,000 US gallons) of municipal wastewater and beef processing wastewater. A large nongovernmental organization hastened restoration with a development process that outlined restoration goals and management objectives to satisfy a dual mandate of wastewater treatment and wildlife habitat creation. In 1995, after five years of wastewater additions, the basins had been refilled and the surrounding uplands had been acquired and restored. The Frank Lake Conservation Area currently provides high-quality habitat for a variety of wildlife in a region where many of the native plants and animals species have been lost due to habitat loss and fragmentation. The success of upland and water management strategies is reflected in the increase of target species' abundance and richness: 50 shorebird species, 44 waterfowl species, 15 raptor species, and 28 other new bird species have returned to the marsh since restoration. As well, significant N and P reduction occurs as waters flow through the first basin of the marsh. The management strategies of this project that satisfied a dual mandate serve as a model to guide managers of other large-scale wetland restoration projects.     

MANAGEMENT OF BASEFLOW AUGMENTATION: A REVIEW1

ABSTRACT: Baseflow augmentation refers to the temporary storage of subsurface water in floodplains, streambanks, and/or stream bottoms during the wet season, either by natural or artificial means, for later release during the dry season to increase the magnitude and permanence of low flows. Management strategies for baseflow augmentation fall into the following categories: (1) range management, (2) upland vegetation management, (3) riparian vegetation management, (4) upland runoff detention and retention, and (5) the use of instream structures. The benefits of a management strategy focused on baseflow augmentation are many, including: (1) increased summer flows, (2) healthier riparian areas, (3) increased channel and bank stability, (4) decreased erosion and sediment transport, (5) improved water quality, (6) enhanced fish and wildlife habitat, (7) lower stream temperatures, and (8) improved stream aesthetics. This review has shown that baseflow augmentation has been successfully accomplished in a few documented cases. Given its clear impact on soil and water conservation, particularly in the semiarid western U.S., it appears that baseflow augmentation is a concept whose time has come. Research is needed on how to successfully integrate baseflow augmentation within comprehensive resource management strategies.     

The need for constructing endangered fish habitats that conform to climate-driven flow changes in a western U.S. river

Warmwater fish habitat in the San Juan River of the southwestern United States has been reduced by over 30% as a result of water depletion, reservoir inundation, and cold-water dam releases combined with drought-related changes in hydrology. This reduction and a suite of other factors have contributed to declines in native fish populations including the federally endangered Colorado Pikeminnow (Ptychocheilus lucius) and Razorback Sucker (Xyrauchen texanus). Conservation efforts for these species include determining flow needs; protecting, managing, and augmenting habitats; and stocking hatchery fish. But the young of stocked fish have low survival due largely to a paucity of nursery habitat not being reformed and maintained under current conditions. Flow recommendations for Navajo Dam releases designed to mimic the river's natural hydrograph have not been met due to water shortages, and the desired outcomes of increased channel complexity and enhanced fish habitat have not been observed. Forecasted hydrology that includes ongoing drought shows that achieving the flow targets through further dam reoperations is unlikely. Mechanical construction of early life-stage habitats is a highly recommended complement to flow management for offsetting the effects of flow reduction and habitat loss. Habitats with features that are effective and resilient under a range of flows are important in counterbalancing the effects of climate change.     

Habitat Improvements and Fish Community Response Associated with an Agricultural Two‐Stage Ditch in Mower County,Minnesota

Water quality and stream habitat in agricultural watersheds are under greater scrutiny as hydrologic pathways are altered to increase crop production. Ditches have been traditionally constructed to remove water from agricultural lands. Little attention has been placed on alternative ditch designs that are more stable and provide greater habitat diversity for wildlife and aquatic species. In 2009, 1.89 km of a conventional drainage ditch in Mower County, Minnesota, was converted to a two‐stage ditch (TSD) with small, adjacent floodplains to mimic a natural system. Cross section surveys, conducted pre‐ and post‐construction, generally indicate a stable channel with minor adjustments over time. Vegetation surveys showed differences in species composition and biomass between the slopes and the benches, with changes ongoing. Longitudinal surveys demonstrated a 12‐fold increase in depth variability. Fish habitat quality improved with well‐sorted gravel riffles and deeper pool habitat. The biological response to improved habitat quality was investigated using a Fish Index of Biological Integrity (FIBI). Our results show higher FIBI scores post‐construction with scores more similar to natural streams. In summary, the TSD demonstrated improvements in riparian and instream habitat quality and fish communities, which showed greater fish species richness, higher percentages of gravel spawning fish, and better FIBI scores. This type of management tool could benefit ditches in other regions where gradient and geology allow.     

Integrated Management to Create New Breeding Habitat for Dalmatian Pelicans (Pelecanus crispus) in Greece

/ An integrated management plan to create favorable nesting habitat for the world-endangered Dalmatian pelicans, was tested at Kerkini irrigation reservoir, a Ramsar wetland. The lake is the major wintering site of Dalmatian pelicans in Europe, where the species lives year-round without breeding. The rise of water level at the reservoir during spring (exceeding 5 m) has an impact on the whole system, including several birds, which lose their nesting habitat. Although the integrity of the wetland demands ecological restoration with changes in its hydrologic regime, local socioeconomic conditions allow only habitat level interventions. During the planning phase of the management plan, both the ecological and social context of the interventions were considered. Monitoring of all pelican habitats and populations provided the scientific basis, while a socioecological survey on knowledge/attitudes of local fishermen toward wetland identified conflicts with specific resources and planned management. To gain public support, a broad information/education program was implemented. The education program for fishermen was based on the findings of the socioecological survey. The in situ management involved experimental construction of floating rafts, platforms over water, dredged-spoil islands, and platforms at various sites of the wetland. Monitoring of the managed habitats showed that most waterbirds used them for resting and roosting. Common terns nested on the rafts, cormorants on the platforms, and Dalmatian pelicans on the man-made island. Under the prevailing hydrologic and weather conditions, islands seem to be the most suitable habitat for pelican nesting. It is concluded that wildlife habitat management should integrate the ecological component, related to the needs of the species and ecosystem, with the social one, expressed by cooperation and involvement of the local community.KEY WORDS: Integrated management; Pelican; Nesting habitat; Habitat management; Reservoir-wetland; Public participation, Greece     

Conservation Opportunities for Securing In-Stream Flows in the Platte River Basin: A Case Study Drawing on Casper,Wyoming’s MunicipalWater Strategy

The Platte River Basin consists of tributaries largely in Wyoming, Colorado and Western Nebraska, with the main stem in Central Nebraska. Critical wildlife habitat on the main stem requires additional in-stream flows. The watershed is one hosting multiple resources, a variety of users, and managed by an array of state and federal agencies. This study proposes a basis for securing in-stream flows for the Platte River. Candidate water supply mechanisms are suggested based on the way in which Casper, Wyoming secured water for its municipal needs. Canal lining is compared to a dam project, increasing reservoir storage, and purchasing water rights, with consideration also made for water pricing to reduce municipal use. Comparisons are based on economic efficiency, potential water conservation, and property rights criteria. Canal lining, coupled with demand management, is shown to conserve water best, given the set of efficiency and cost criteria for in-stream flow enhancement. The approach offers an opportunity to organize the water supply choice context in a transboundary watershed when quantitative information is limited.     

ENVIRONMENTAL DESIGNS FOR STREAMBANK PROTECTION PROJECTS1

ABSTRACT: Streambank protection projects are intended to prevent streambank erosion, thereby preventing streambank failure and maintaining a desirable channel alignment. Streambank erosion is a natural process of unaltered, dynamic river systems, and protection projects seek to impose stability on this natural system. The environmental impacts of such projects are primarily changes to terrestrial and aquatic habitats and to aesthetics. Adverse environmental impacts have been minimized and enhancement of existing habitat and aesthetics have been achieved through the development of new, innovative designs or modifications to existing designs and through use of construction and maintenance practices that promote habitat and aesthetics. Designs based on channel flow characteristics, e.g., revetments using a variety of structural materials, can result in preservation of wildlife habitat by reducing the use of structural protection by matching the erosion potential of flow at the bank with the protection capability of the materials used. Designs based on streambed stabilization prevent bank failure caused by bank undermining, result in preservation or establishment of streamside vegetation, and enhance aesthetics. Protection schemes that manage and preserve floodplains, berms, and riparian areas preserve the natural condition of the floodplain area. Designs based on deflection of erosive flows, e.g., dikes, minimize disturbance to the bank vegetation and create low-velocity aquatic habitats. Use of vegetation for bank protection is most effective when used in combination with structural components. Construction and maintenance practices can be scheduled and modified to minimize impacts to floodplain areas and to enhance wildlife habitat while preserving the integrity of the protection structure.     

Resource protection for waterbirds in Chesapeake bay

Many living resources in the Chesapeake Bay estuary have deteriorated over the past 50 years. As a result, many governmental committees, task forces, and management plans have been established. Most of the recommendations for implementing a bay cleanup focus on reducing sediments and nutrient flow into the watershed. We emphasize that habitat requirements other than water quality are necessary for the recovery of much of the bay's avian wildlife, and we use a waterbird example as illustration. Some of these needs are: (1) protection of fast-eroding islands, or creation of new ones by dredge deposition to improve nesting habitat for American black ducks(Anas rubripes), great blue herons(Ardea herodias), and other associated wading birds; (2) conservation of remaining brackish marshes, especially near riparian areas, for feeding black ducks, wading birds, and wood ducks(Aix sponsa); (3) establishment of sanctuaries in open-water, littoral zones to protect feeding and/or roosting areas for diving ducks such as canvasbacks(Aythya valisineria) and redheads(Aythya americana), and for bald eagles(Haliaeetus leucocephalus); and (4) limitation of disturbance by boaters around nesting islands and open-water feeding areas. Land (or water) protection measures for waterbirds need to include units at several different spatial scales, ranging from “points” (e.g., a colony site) to large-area resources (e.g., a marsh or tributary for feeding). Planning to conserve large areas of both land and water can be achieved following a biosphere reserve model. Existing interagency committees in the Chesapeake Bay Program could be more effective in developing such a model for wildlife and fisheries resources.     

Predicting Fish Growth Potential and Identifying Water Quality Constraints: A Spatially-Explicit Bioenergetics Approach

Anthropogenic impairment of water bodies represents a global environmental concern, yet few attempts have successfully linked fish performance to thermal habitat suitability and fewer have distinguished co-varying water quality constraints. We interfaced fish bioenergetics, field measurements, and Thermal Remote Imaging to generate a spatially-explicit, high-resolution surface of fish growth potential, and next employed a structured hypothesis to detect relationships among measures of fish performance and co-varying water quality constraints. Our thermal surface of fish performance captured the amount and spatial-temporal arrangement of thermally-suitable habitat for three focal species in an extremely heterogeneous reservoir, but interpretation of this pattern was initially confounded by seasonal covariation of water residence time and water quality. Subsequent path analysis revealed that in terms of seasonal patterns in growth potential, catfish and walleye responded to temperature, positively and negatively, respectively; crappie and walleye responded to eutrophy (negatively). At the high eutrophy levels observed in this system, some desired fishes appear to suffer from excessive cultural eutrophication within the context of elevated temperatures whereas others appear to be largely unaffected or even enhanced. Our overall findings do not lead to the conclusion that this system is degraded by pollution; however, they do highlight the need to use a sensitive focal species in the process of determining allowable nutrient loading and as integrators of habitat suitability across multiple spatial and temporal scales. We provide an integrated approach useful for quantifying fish growth potential and identifying water quality constraints on fish performance at spatial scales appropriate for whole-system management.     

EFFECTS OF WATERSHED BEST MANAGEMENT PRACTICES ON HABITAT AND FISH IN WISCONSIN STREAMS1

ABSTRACT: We evaluated the effectiveness of watershed‐scale implementations of best‐management practices (BMPs) for improving habitat and fish attributes in two coldwater stream systems in Wisconsin. We sampled physical habitat, water temperature, and fish communities in multiple paired treatment and reference streams before and after upland (barnyard runoff controls, manure storage, contour plowing, reduced tillage) and riparian (stream bank fencing, sloping, limited rip‐rapping) BMP installation in the treatment subwatersheds. In Spring Creek, BMPs significantly improved overall stream habitat quality, bank stability, instream cover for fish, abundance of cool‐ and coldwater fishes, and abundance of all fishes. Improvements were most pronounced at sites with riparian BMPs. Water temperatures were consistently cold enough to support coldwater fishes such as trout (Salmonidae) and sculpins (Cottidae) even before BMP installation. We observed the first‐time occurrence of naturally reproduced brown trout (Salmo trutta) in Spring Creek, indicating that the stream condition had been improved to be able to partially sustain a trout population. In Eagle Creek and its tributary Joos Creek, limited riparian BMPs led to localized gains in overall habitat quality, bank stability, and water depth. However, because few upland BMPs were installed in the subwatershed there were no improvements in water temperature or the quality of the fish community. Temperatures remained marginal for coldwater fish throughout the study. Our results demonstrate that riparian BMPs can improve habitat conditions in Wisconsin streams, but cannot restore coldwater fish communities if there is insufficient upland BMP implementation. Our approach of studying multiple paired treatment and reference streams before and after BMP implementation proved effective in detecting the response of stream ecosystems to watershed management activities.     

River Dolphins in Bangladesh: Conservation and the Effects of Water Development

Platanista gangetica ) are threatened in Bangladesh from the effects of dams, large embankment schemes, dredging, fisheries bycatch, directed hunting, and water pollution. Visual surveys of the section of the Jamuna River located between the divergence of the Old Brahmaputra River and the confluence of the Padma River and the section of the Kushiyara River located between the Bangladesh–India border and the confluence of the Korangi River recorded a sighting rate of 0.13 sightings/km (mean group size = 1.8 dolphins) and 0.08 sightings/km (mean group size = 3.8 dolphins), respectively. These sections of river were considered to be priority areas for investigation because several water development projects have already been constructed and more are planned for the areas. During the surveys we examined the remains of dolphins caught accidentally in plastic gillnets and observed fishermen catching the fish species Clupisoma garua using dolphin oil and body parts as a fish attractor. Additional studies are needed to assess the status of dolphins and effects of water development and fisheries bycatch. Feasibility studies should be conducted on designating dolphin/fish sanctuaries and creating artificial habitat or enhancing existing habitat in eddy countercurrent scour pools to mitigate deleterious impacts. The environmental requirements of river dolphins reflect the needs of productive and biotically diverse tropical rivers.