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The abundance of many Chinook salmon ( Oncorhynchus tshawytscha) stocks has declined despite reductions in harvest. We used state-space models parameterized with data from 57 Chinook salmon indicator stocks, ranging from coastal Oregon to southeast Alaska, to quantify long-term (since 1972 release year) changes in juvenile marine survival rate and mean age-at-maturity, as well as identify stock groupings with coherent dynamics. We found that juvenile marine distribution—rather than freshwater life history, run timing, or adult marine distribution—was the best predictor of trends in both survival and age. Only subyearling stocks that enter the Strait of Georgia showed evidence of transitioning to a low juvenile survival period, other groupings exhibited low and stable or cyclical patterns in survival. Conversely, declines in mean age-at-maturity were widespread and do not appear to have stabilized, suggesting that future declines in Chinook salmon population productivity may be influenced by earlier maturation or increased adult mortality, rather than further reductions in juvenile marine survival.

No abstract.

Africa's human population is growing rapidly and is set to account for 40 percent of global numbers by 2100. Further development of its inland waters, to enhance water and energy security, is inevitable. Will it follow the development pathway of industrialized countries, often destructive of ecosystems, biodiversity, and river-dependent social structures, or can it chart a new way into the future based on global lessons of equity and sustainability? This essay tracks the global and African growth of the benefits and costs of water resource developments, explores the reasons for the costs, and offers insights on new scientific thinking that can help guide Africa to a more sustainable future.

An holistic environmental flows (EFlows) assessment, undertaken as part of an environmental and social impact assessment (ESIA), led to improved planning and design of the Gulpur hydropower project (HPP) on the Poonch River, Mahaseer National Park, Pakistan. The park was declared a conservation area primarily because of its two globally threatened fish species, the endangered Mahaseer (Tor putitora) and critically endangered Kashmir Catfish (Glyptothorax kashimirensis). These triggered critical habitat thresholds for the funders, requiring special biodiversity protection measures. Despite the river’s conservation status, these two species are under threat of extinction from unsustainable harvesting and catchment practices, notably non-selective fishing practices and sand and gravel mining in the river bed. The EFlows study analysed various permutations of flow releases from the proposed dam, operational regimes and catchment management options. The need to contain existing adverse impacts on the threatened fish and river ecosystem, combined with the results of the assessment, influenced the planned turbine design, weir location and operational regime of the project. Additional management measures to enhance the protection status of the park and its fish to achieve a biodiversity net gain outcome were developed with conservation management stakeholders and communities. These measures were incorporated into a biodiversity action plan, which was approved by Pakistan’s regulatory authorities and paved the way for approval of the project financing by international lenders. The project represents a valuable case study on mechanisms for achieving ecologically sustainable HPPs.

The Okavango River originates in Angola and flows inland bordering Namibia, terminating in an inland delta in the Kalahari Desert, Botswana. The Delta constitutes one of the largest Ramsar sites in the world and was designated by UNESCO as its 1000th World Heritage Site in June 2014. It is renowned for its plant and animal life, supporting a tourist industry that is the second largest source of income for Botswana. Until recently the river system was not subject to any large-scale water resource development, but independence from colonial powers, cessation of civil unrest in Angola and growing aspirations of the basin's three countries mean that development of the river system is inevitable. The Permanent Okavango River Basin Water Commission (OKACOM) was created by the Member States in September 15, 1994 and is addressing the challenge of how to develop the river basin for the benefit of all its citizens without unacceptably degrading the nature of this iconic river. Two key early activities were completion of a Transboundary Diagnostic Analysis that included an Environmental Flows Assessment, followed by the drawing up of a Strategic Action Programme. There are several International Cooperating Partners supporting aspects of basin development as OKACOM enters its second term and the Member States recognise the governance and other challenges that lie ahead.

For over 100 years, sharks have been encountered, as either directed catch or incidental catch, in commercial fisheries throughout the Northeast Pacific Ocean. A long-standing directed fishery for North Pacific Spiny Dogfish (Squalus suckleyi) has occurred and dominated shark landings and discards. Other fisheries, mainly for shark livers, have historically targeted species including Bluntnose Sixgill Shark (Hexanchus griseus) and Tope Shark (Galeorhinus galeus). While incidental catches of numerous species have occurred historically, only recently have these encounters been reliably enumerated in commercial and recreational fisheries. In this chapter we present shark catch statistics (directed and incidental) for commercial and recreational fisheries from Canadian waters (off British Columbia), southern US waters (off California, Oregon, and Washington), and northern US waters (off Alaska). In total, 17 species of sharks have collectively been encountered in these waters. Fishery encounters present conservation challenges for shark management, namely, the need for accurate catch statistics, stock delineation, life history parameter estimates, and improved assessments methods for population status and trends. Improvements in management and conservation of shark populations will only come with the further development of sound science-based fishery management practices for both targeted and incidental shark fisheries.

The term “environmental flows” is now widely used to reflect the hydrological regime required to sustain freshwater and estuarine ecosystems, and the human livelihoods and well-being that depend on them. The definition suggests a central role for ecohydrological science to help determine a required flow regime for a target ecosystem condition. Indeed, many countries have established laws and policies to implement environmental flows with the expectation that science can deliver the answers. This article provides an overview of recent developments and applications of environmental flows on six continents to explore the changing role of ecohydrological sciences, recognizing its limitations and the emerging needs of society, water resource managers and policy makers. Science has responded with new methods to link hydrology to ecosystem status, but these have also raised fundamental questions that go beyond ecohydrology, such as who decides on the target condition of the ecosystem? Some environmental flow methods are based on the natural flow paradigm, which assumes the desired regime is the natural “unmodified” condition. However, this may be unrealistic where flow regimes have been altered for many centuries and are likely to change with future climate change. Ecosystems are dynamic, so the adoption of environmental flows needs to have a similar dynamic basis. Furthermore, methodological developments have been made in two directions: first, broad-scale hydrological analysis of flow regimes (assuming ecological relevance of hydrograph components) and, second, analysis of ecological impacts of more than one stressor (e.g. flow, morphology, water quality). All methods retain a degree of uncertainty, which translates into risks, and raises questions regarding trust between scientists and the public. Communication between scientists, social scientists, practitioners, policy makers and the public is thus becoming as important as the quality of the science.

The Okavango River system flows through Angola, Namibia and Botswana. It is in near-natural condition and supports globally iconic wetlands and wildlife. The basin’s people are poor and development is inevitable: the next decade is critical. The river could become an example of responsible planning that resolutely addresses the three pillars of sustainable development. Recognizing this, the Member States completed a transboundary diagnostic analysis (TDA) in 2010 funded by the three governments and the Global Environment Facility. A central feature of the TDA was a basin-wide environmental flow assessment using the DRIFT (Downstream Response to Imposed Flow Transformation) holistic approach. This produced scenarios of increasing water resource use that spelled out the costs and benefits in terms of the health of the river ecosystem, associated social structures and local and national economies. The results were used to help create a transboundary strategic action programme, which the Member States...

A fully integrated, physically-based MIKE SHE/MIKE11 model was developed for the Mokolo River basin flow system to simulate key hydraulic and hydrologic indicator inputs to the Downstream Response to Imposed Flow Transformation for Arid Rivers (DRIFT-ARID) decision support system (DSS). The DRIFT-ARID tool is used in this study to define environmental water requirements (EWR) for non-perennial river flow systems in South Africa to facilitate ecosystembased management of water resources as required by the National Water Act (Act No. 36 of 1998). Fifty years of distributed daily climate data (1950 to 2000) were used to calibrate the model against decades of daily discharge data at various gauges, measurements of Mokolo Dam stage levels, and one-time groundwater level measurements at hundreds of wells throughout the basin. Though the calibrated model captures much of the seasonal and post-event stream discharge response characteristics, lack of sub-daily climate and stream discharge data limits the ability to calibrate the model to event-level system response (i.e. peak flows). In addition, lack of basic subsurface hydrogeologic characterisation and transient groundwater level data limits the ability to calibrate the groundwater flow model, and therefore baseflow response, to a high level. Despite these limitations, the calibrated model was used to simulate changes in hydrologic and hydraulic indicators at five study sites within the basin for five 50-year land-use change scenarios, including a present-day (with dam), natural conditions (no development/irrigation), and conversion of present-day irrigation to game farm, mine/city expansion, and a combination of the last two. Challenges and recommendations for simulating the range of non-perennial systems are presented. Keywords : hydrology, non-perennial, MIKE SHE, integrated surface and groundwater modelling

1. Little is known about hydrological influences on tropical waterbird communities. We used a 16-year data set (1991–2007) of waterbird censuses, together with a classification of observed species into foraging guilds, to explore the relationships between natural variations in flow regime, foraging guild and the community composition of waterbirds at the Okavango River in the Caprivi Strip of north-eastern Namibia, southern Africa. 2. We addressed three hypotheses to explain variation in waterbird community composition: (i) exploitation (birds move towards resource-rich patches to exploit periods of high food abundance); (ii) escapism (declines in regional habitat quality force birds to aggregate in perennial waterbodies); and (iii) interaction (bird assemblages are dominated by intra- and interspecific interactions, such as flock formation for breeding or moulting, that can be explained better by life history demands or competition than by resource availability). 3. Waterbirds in different foraging guilds responded strongly but at different periods to changes in the hydrological environment, creating a complex but predictable successional pattern in community composition through time. Deep-water feeders responded fastest (abundance peaking 2 months post-flood), followed by shallow-water feeders (4 months) and emergent vegetation feeders (7 months). Species that forage on short vegetation or in mud showed a bimodal response with peaks in abundance at 3 and 8 months post-flood. 4. Our results indicated a strong effect of the local flow regime and hence supported the exploitation hypothesis. The foraging guild approach allowed us to identify clear patterns in a highly complex ecosystem and shows considerable promise as an analytical tool for similar data sets. Our results further suggest that while the entire bird community will be affected by hydrological alterations such as impoundments, water extraction and climate change, deep-water feeders may be one of the most vulnerable groups.

Provision for environmental flows (EFs) in water use and water-resource developments has been legislated in several southern and eastern African countries. While much of the focus has been on the assessment of EFs for new water-resource developments, some attention has been paid to the possibilities of modifying the operation of existing infrastructure to deliver EFs. This paper summarizes research done to support the re-operation of the Katse Dam in Lesotho, the Clanwilliam and Kogelberg Dams in South Africa, the Cahora Bassa Dam in Mozambique and the Nyumba ya Munga Dam in Tanzania in ways that would reduce their downstream impacts. For each, the original and suggested new operating rules are presented, and the reasons for the suggested changes are summarized. The negotiation and decision-making processes relevant to each dam are also discussed, and some of the challenges faced at two of the dams (Katse and Kogelberg), where revised operating rules have been implemented, are reviewed.

Summary 1. This study summarises our development and application in developing countries of a process for assessing the ecological, social and economic costs and benefits of water-resource developments, as an aid to basin planning. 2. During 15 years of work in Africa and Asia, the process sequentially included the whole river ecosystem and the whole flow regime in the assessment; used a multidisciplinary team and a scenario-based approach that gave equal weighting to the ecological, social, resource-economic and macro-economic costs and benefits of development; quantified or semi-quantified the costs and benefits in data-poor situations, capturing expert opinion and local wisdom as well as data; recognised that the final allocation of water for ecosystem maintenance should be a societal choice of trade-offs between resource protection and development. 3. Flow assessments were increasingly done at the basin rather than project level and introduced the concept and practicality of Development Space as a tool to aid basin planning. 4. Later assessments included valuation of regulating, cultural and provisioning services provided by rivers as part of the cost-benefit analysis. 5. Implementation of managed flows as outlined above is a complex and long-term process that should include a number of major steps, from development of the appropriate legislation to monitoring of management decisions and adaptive management. Country or region-wide implementation at this scale could well take one to two decades, even where the political will and technical skills exist. 6. We conclude by offering eight principles that we believe would promote genuinely sustainable use of rivers.

Under the European Union Water Framework Directive, Member States must put in place a river basin planning framework to determine what measures are necessary to maintain and improve the ecological status for all surface water bodies. The governmental organisations legally responsible for implementing the Directive in the UK have recognised that an appropriate river flow regime is fundamental to maintain a healthy river and, as a result, they need to regulate abstractions and effluent discharges and ensure sufficient water is released from impoundments. This paper reports on the process of producing environmental standards that define the maximum abstraction allowable from UK rivers, to leave sufficient flow to maintain a healthy river ecosystem. As there are currently insufficient data available to determine the relationships between river flow and ecological status empirically, expert knowledge was captured through a series of workshops at which leading UK freshwater scientists defined maximum l...

This article seeks to apply mainstream criminological discourses to refugee policy, using Australia’s refugee policy as a case study. Notions of security, ethnicity, race, social exclusion and xenophobia are all well established within various criminological discourses. This article aims to show that the use of similar discourses in both the criminological and refugee spheres is increasingly prevalent and helps to justify restrictive refugee practices within the context of societal security.

Sustainable use of river ecosystems requires that they be managed holistically. This paper describes an holistic methodology, DRIFT (Downstream Response to Imposed Flow Transformation), for advising on environmental flowsfor rivers targetted for water-management activities. DRIFT's basic philosophy is that all major abiotic and biotic components constitute the ecosystem to be managed; and within that, the full spectrum of flows, and their temporal and spatial variability, constitute the flows to be managed. The methodology employs experienced scientists from the following biophysical disciplines: hydrology, hydraulics, fluvial geomorphology, sedimentology, chemistry, botany and zoology. Where there are subsistence users of the river, the following socio-economic disciplines are also employed: sociology, anthropology, water supply, public health, livestock health and resource economics. DRIFT is a structured process for combining data and knowledge from all the disciplines to produce flow-related scenarios for water managers to consider. It consists of four modules. In the first, or biophysical module, the river ecosystem is described and predictive capacity developed on how it would change with flow changes. In the second, or socio-economic module, links are described between riparian people who are subsistence users of river resources, the resources they use, and their health. The objective is to develop predictive capacity of how river changes would impact their lives. In the third module, scenarios are built of potential future flows and the impacts of these on the river and the riparian people. The fourth, or economic module, lists compensation and mitigation costs. DRIFT should run in parallel with two other exercises which are external to it: a macro-economic assessment of the wider implications of each scenario, and a Public Participation Process whereby people other than subsistence users can indicate the level of acceptability of each scenario. DRIFT has been developed in a semi-arid, developing region, where water-supply problems are pressing, and uncertainties about river-linked ecological and social processes high. The use of DRIFT in this context is discussed.

This article seeks to explain Australia's refugee policy and to identify the various objectives and factors that influence the development of that policy. Australia's refugee programme seeks to: provide a humanitarian response and protection to individual refugees; participate responsibly in the international community; honour its Convention obligations; further the interests of the people of Australia; meet high standards of administration and; acknowledge as much as possible changes in refugee populations. In fulfilling these objectives, Australian governments must weigh and balance various competing factors. These include: humanitarian responsibility, international obligations, social, political, economic and foreign policy factors, as well as efficient administration. In balancing the relative importance of these factors, the Federal government hopes to fulfil all its refugee and humanitarian objectives. However, the pluralistic nature of Australian society and the often conflicting ideals associated with protection of Australia's interests and the preservation of the rights of refugees, means that fulfilment of these objectives is difficult. This article examines the Australian government's response to the Kosovar conflict, to assess the relative success Australia had in fulfilling its refugee policy objectives and identifying the various factors that produced the final result.

This is the 62nd annual report of the British Trust for Ornithology's Ringing Scheme, presenting research carried out and data received in 1998. A study offish‐eating birds, initiated because of a perceived increase of predation on fish populations in inland waterbodies, established that there has been an increase in the proportion of ringed Cormorants that are found inland and that this increase took place before the increase in continental Cormorant populations or the establishment of inland‐breeding in Britain. The rise was coincident with the main period of stocking of inland waterbodies for angling. In addition it was established that birds found in each inland area were from a variety of breeding sites, so control at a particular breeding site will not be effective at controlling predation levels at a particular water body. A major project on habitat fragmentation and woodland birds, which particularly investigated the role of dispersal, was completed. Recovery data were used to calculate mean natal...

In South Africa, modified flow regimes designed to maintain ecosystem functioning at some pre-determined level are recommended for all rivers involved in major water-resource developments. One component of such flow regimes of special interest in the winter-rainfall region of the country is the small pulses of higher flow that occur in the dry season (November–April), here called freshes. Research was carried out in the Olifants River, in the winter-rainfall region of South Africa, on the link between freshes and spawning of an endemic, vulnerable cyprinid, the Clanwilliam yellowfish Barbus capensis. Experimental releases from Clanwilliam Dam on the Olifants River in a previous year showed that a greater than usual spawning success, assessed by larval recruitment levels, was correlated with hypolimnetic freshes released during the species' breeding season (October–January). In the study reported on here, a hypolimnetic fresh of the same size, duration and timing as those linked with successful spawning failed to induce spawning. Differences in the thermal regime of water releases appeared to be responsible. Two warm (19–21 °C), epilimnetic freshes of 15 hours duration were then released, and correlated with fish moving onto the spawn beds and exhibiting pre-spawning behaviour. However, the fish moved downstream away from the spawn beds when cold (16–18 °C) hypolimnetic baseflows were released for 15 hours between the two epilimnetic freshes and continually after the second one. The presence of free embryos and larval B. capensis indicated, from their developmental stages, that spawning had probably occurred before the experimental releases began, when warm (21–23 °C) epilimnetic water was spilling over the dam, and had halted once spillage stopped and hypolimnetic releases began. Indeed, the presence of dead and deformed young suggested that the cold water may have had a detrimental affect on those spawned during the earlier warmer spell. A summary table details the conditions, including the hydraulic characteristics of the spawn beds, believed to induce spawning and support early life stages of B. capensis. It is concluded that freshes released from Clanwilliam Dam at the appropriate time (October–January) should be able to increase spawning success of B. capensis, but only if the water temperature at the spawn site is at or above 19 °C and stable or rising. However, successful spawning will not necessarily lead to high recruitment if water temperatures are not then maintained at appropriate levels for some time for development of the embryos and larvae. This implies that additional epilimnetic releases will be required following critical trigger flows.

This paper describes an investigation of how experimental releases of pulses of high flow from Clanwilliam Dam (Olifants River, South Africa) affect spawning of the Clanwilliam yellowfish, Barbus capensis. This species is endemic to the Olifants River system and is listed as rare in the Red Data Book of fishes for South Africa. Spawning sites are described, as is the spawning behaviour of B. capensis after specific experimental pulses released during the suspected spawning season of the species. Spawning and the developmental stages of embryos, free embryos, and larval B. capensis were studied using direct observations, video recordings, and microscopic examination of live embryos. B. capensis was found to be a repeat-spawner over several days as well as a multiple-spawner throughout the 4 month reproductive season. At present, spawning of B. capensis occurs down-stream of the dam sporadically (and possibly with limited recruitment), concurrent with releases of water for irrigation purposes. Experimental pulses appeared to trigger an increase in spawning activity, as an abundance of larvae was found down-stream 2 months later. It is suggested that a water-release strategy from Clanwilliam Dam could be designed to increase the number of B. capensis in the Olifants River. © 1997 John Wiley & Sons, Ltd.

Environmental water requirement (EWR) assessment methods, for ascertaining how much water should be retained in rivers to sustain ecological functioning and desired levels of biodiversity, have mostly been developed for perennial rivers. Despite non-perennial rivers comprising about 30–50% of the world’s freshwater systems, data on their hydrology, biota and ecological functioning are sparse. Current EWR assessments require hydrological and other data that may not be available for such rivers and some adaptation in the methods used seems necessary. DRIFT is an EWR method for perennial (or near-perennial) rivers that has been developed in South Africa over the past two decades and is now widely applied nationally and internationally. When applied to the semi-permanent Mokolo River, challenges particular to, or accentuated by, non-perennial rivers included the reliable simulation of hydrological data, the extent of acceptable extrapolation of data, difficulties in predicting surface-water connectivity along the river, and the location and resilience of pools, as well as whether it was possible to identify a reference (natural) condition. DRIFT-ARID, reported on here, is an adaptation of the DRIFT approach to begin addressing these and other issues. It consists of 11 phases containing 29 activities. Keywords : EWR, non-perennial, DRIFT, DSS

Methods developed to determine the amount of water required (EWR) to sustain ecosystem services in non-perennial rivers need a different approach to those used in perennial rivers. Current EWR methods were mostly developed for use in perennial rivers. Non-perennial rivers differ from perennial ones in terms of variability in flow, periods of no-flow and related habitat availability. A DRIFT-ARID method (an adaptation of the Downstream Response to Imposed Flow Transformation (DRIFT) method) was developed, tested and adjusted, using the semi-permanent Mokolo River. Field data from five study sites was collected from April to May 2010 by a multidisciplinary team. The results were used in a DRIFT-ARID Decision Support System (DSS) to determine the impact of five chosen development scenarios in the Mokolo River Catchment. An integrated groundwater–surface water MIKE-SHE hydrological model was used to simulate the hydrology of the chosen scenarios. Specific non-perennial river indicators such as onset of dry phase were identified and included in the DRIFT-ARID DSS. DRIFT-ARID has the potential to be used in non-perennial rivers and, once set up, can provide results for future scenarios. The method now needs to be tested on other non-perennial river types, especially episodic rivers where data are scarce or non-existent. Keywords : DRIFT-ARID, non-perennial, EWR, flow method, Mokolo River

The quality and quantity of allochthonous inputs and of benthic organic matter were investigated in a second-order, perennial mountain stream in the south-west Cape, South Africa, between April 1983 and January 1986. Although the endemic, riparian vegetation is sclerophyllous, low and evergreen, inputs of allochthonous detritus to the stream (434 to 500 g m−2y−1) were similar to those recorded for riparian communities worldwide, as were calorific values of these inputs (9548 to 10 032 KJ m−2y−1). Leaf fall of the riparian vegetation is seasonal, occurring in spring (November) as discharge decreases, resulting in retention of benthic organic matter (BOM) on the stream bed during summer and early autumn (maximum 224 g m−2). Early winter rains (May) scoured the stream almost clean of benthic detritus (winter minimum 8 g m−2). Therefore, BOM was predictably plentiful for about half of each year and predictably scarce for the other half. Coarse BOM (CBOM) and fine BOM (FBOM) constituted 46–64% of BOM standing stock, ultra-fine BOM (UBOM) 16–33% and leaf packs 13–24%. The mean annual calorific value of total BOM standing stock was 1709 KJ m−2. Both standing stocks and total calorific values of BOM were lower than those reported for streams in other biogeographical regions. Values of C:N ratios decreased with decrease in BOM particle size (CBOM 27–100; FBOM 25–27; UBOM 13–19) with no seasonal trends. The stream is erosive with a poor ability to retain organic detritus. Its character appears to be dictated by abiotic factors, the most important of which is winter spates.

Monthly samples of macroinvertebrates were collected from the stony-bed and marginal-vegetation habitats of a small river in the south western Cape Province, South Africa. Cluster analyses of the samples revealed assemblages of invertebrates (here referred to as ‘communities’) with clear spatial and temporal distribution patterns in the muer. The species composition of the communities, and their distribution, are described. The relation of the macroinvertebrate distribution to changes in the physico-chemical environment was investigated using stepwise multiple discriminant analysis. The results indicated a strong correlation between the two.

SUMMARY 1. The occurrence, composition and invertebrate fauna of naturally-occurring leaf packs were studied over 24 months in Langrivier, a second-order mountain stream in the south-western Cape, South Africa. Langrivier is shallow and fast-flowing and stores very low levels of allochthonous detritus, although natural leaf packs form an obvious part of the energy base in the stream throughout the year. 2. The occurrence and size of the packs were influenced mainly by stream discharge and by the timing and character of leaf fall from riparian trees. Packs were smallest (minimum dry mass 17 g, minimum volume 1.7–10−5 m3) in winter when discharge was high, and largest (maximum dry mass 191 g, maximum volume 4.2–10−3 m3) in spring when discharge decreased and leaf fall from the evergreen riparian trees began. Through the year the packs covered a mean 0.41 % of the stream bed and had a mean abundance of 0.46 packs m−2 of stream bed. They were ephemeral, lasting on average

In a study of a second-order southern African stream, complementary classification and multidimensional scaling (MDS) techniques revealed longitudinal changes in macroinvertebrate community structure, but no temporal changes. Stepwise discriminant analysis and multiple linear regression were used to identify environmental variables correlated with the community changes but produced conflicting results depending on the information used, possibly because of strong correlations between some of the variables. The MDS plot of biotic samples illustrated that potassium levels correlated most strongly with community distribution. Because of the large number of variables now shown worldwide to correlate with faunal distributions, we suggest ways to choose the variables to suit the kind of study to be undertaken. Attempts to assign the invertebrates to functional feeding groups (FFGs) were unsatisfactory as the relevant categories are poorly defined and often inadequate for classifying the fauna. We suggest that until these categories are more clearly defined, and more uniformly applied, concepts relating to FFGs cannot be tested satisfactorily. The stream community in Langrivier is more similar to communities found in two other mediterranean ecosystems than to those in other southern African rivers, probably because of the greater predictability of flow in the former.