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51-658: The River Chess is a chalk stream that rises near Chesham in the Chiltern Hills , and flows for 11 miles (18 km) through Buckinghamshire and Hertfordshire to its confluence with the River Colne in Rickmansworth . The Chess, along with the Colne and Gade , gives rise to the name of the district of Three Rivers . The name arose by back-formation from the town of Chesham . The River Chess fall

102-531: A pan-North American study, the main cause being human pollution. The number of fish species and subspecies to become endangered has risen from 40 to 61, since 1989. For example, the Bigmouth Buffalo is now the oldest age-validated freshwater fish in the world, and its status urgently needs reevaluation in parts of its endemic range. About 2 ⁄ 3 of the total freshwater fisheries in China are in

153-672: A species introduced to the British Isles originally for the fur trade. In 2004 a water vole recovery project was set up by the Chilterns Chalk Streams Project and the Environment Agency , combining mink control with habitat improvement to try to halt this decline. In 2005 a survey found that the water vole population had recovered to 18% of its 2001 levels. A less positive story is that of the native white-clawed crayfish , which has suffered at

204-467: A temporary reservoir by regulating the amount of water supplied to the springs. This is why many chalk streams in the UK have stable flow regimes that vary only slightly over time. The temperature of the emerging surface water is fairly stable and rarely deviates from 10 °C (50 °F). On cold winter mornings, water vapour from the relatively warm stream condenses in the cold air above to form fog. Chalk

255-410: A wide range of conditions, preferring a water temperature around 80 °F (27 °C). Warmwater fish can survive cold winter temperatures in northern climates, but thrive in warmer water. Common warmwater fish include catfish , largemouth bass , bluegill , crappies , and many other species from the family Centrarchidae . In 2021, a group of conservation organizations estimated that one-third of

306-615: Is 200 feet (60 m), and its length is 11 miles (18 km). It is fed by groundwater held in the chalk aquifer of the Chiltern Hills and rises from three springs which surface as Vale brook, from Bury Pond, and alongside the Missenden Road near Pednor just to the north of Chesham. It flows within culverts beneath the town before flowing in a southeasterly direction through Waterside . The river flows below parkland landscaped by Capability Brown at Latimer House and

357-566: Is a vital part of aquatic ecosystem stability, so changes to stream and river water temperature can have large impacts on biotic communities. Many aquatic larvae use thermal cues to regulate their life cycles, mostly notably here, insects. Insects are a large part of most fish diets, so this can pose a great dietary problem. Temperature can cause changes in fish behavior and distribution habits as well by increasing their metabolic rates and thus their drive to spawn and feed. Linear systems are more easily fragmented and connectivity in aquatic ecosystems

408-575: Is defined as a species that does not naturally occur in a certain area or ecosystem. This includes eggs and other biological material associated with the species. Non-native species are considered invasive if they cause ecological or economic injury. The introduction of exotic fish species into ecosystems is a threat to many endemic populations. The native species struggle to survive alongside exotic species which decimate prey populations or outcompete indigenous fishes. High densities of exotic fish are negatively correlated with native species richness. Because

459-597: Is invasive worldwide, and there are multiple efforts to remove them from their non-native ecosystems. Both species are among the " 100 of the World’s Worst Invasive Alien Species ," as determined by the IUCN Invasive Species Specialist Group based on their effect on anthropogenic activities, environmental biodiversity and their ability to act as a case study for important ecological issues. Hybridization involves

510-480: Is slightly soluble in rainwater because rain is naturally slightly acidic . The products of chalk weathering are dissolved in rainwater and are transported in stream flow. Chalk streams transport little suspended material (unlike most rivers), but are considered " mineral -rich" due to the dissolved calcium and carbonate ions . The surface water of chalk streams is commonly described as "gin clear". The channel bed consists of angular flint gravel derived from

561-442: Is vital. Freshwater fishes are particularly vulnerable to habitat destruction because they reside in small bodies of water which are often very close to human activity and thus easily polluted by trash, chemicals, waste, and other agents which are harmful to freshwater habitats. Land use changes cause major shifts in aquatic ecosystems. Deforestation can change the structure and sedimentary composition of streams, which impacts

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612-583: The Metropolitan line stations of Chesham , Chorleywood and Rickmansworth , giving visitors the chance to walk either part or the entire route. The route can be followed in either direction and is clearly way-marked. Most of the route is on public footpaths, but there are short sections on roads. Chalk stream The beds of the rivers are generally composed of clean, compacted gravel and flints , which are good spawning areas for Salmonidae fish species. Since they are fed primarily by aquifers ,

663-659: The River Thames , River Lea and River Colne ): Chalk streams of the Yorkshire Wolds : Chalk streams of Lincolnshire : There are several chalk streams in the Lincolnshire Wolds including Chalk streams of Kent: Chalk streams of Norfolk: Chalk streams of Suffolk: Freshwater fish Freshwater fish are fish species that spend some or all of their lives in bodies of fresh water such as rivers , lakes and inland wetlands , where

714-478: The Victorian era supplied London , being transported on the newly constructed Metropolitan Railway . Today the only working watercress beds are at Moor Lane, Sarratt . In 2014, persistent overflows from Chesham Sewage Treatment Works forced the watercress farm to cease sales, and to continue operation the farm now uses well water. The Chess Valley Walk is approximately 10 miles (16 km) long and links with

765-410: The brown trout , grayling and bullhead . To support the fish population there is a rich diversity of both invertebrates and of insects, including the mayfly . The valley has a long history of human habitation. There are a number of Roman villa sites along the valley, including Latimer Park. At Sarratt strip lynchets can be seen in terraces along the hillside made by the action of ploughing along

816-437: The salinity is less than 1.05%. These environments differ from marine habitats in many ways, especially the difference in levels of osmolarity . To survive in fresh water, fish need a range of physiological adaptations . 41.24% of all known species of fish are found in fresh water. This is primarily due to the rapid speciation that the scattered habitats make possible. When dealing with ponds and lakes, one might use

867-577: The southern United States at high elevation . Common coldwater fish include brook trout , rainbow trout , and brown trout . Coolwater fish species prefer water temperature between the coldwater and the long warmwater species, around 60 to 80 °F (16–27 °C). They are found throughout North America except for the southern portions of the United States. Common coolwater species include muskellunge , northern pike , walleye , and yellow perch . Warmwater fish species can survive in

918-481: The 210 rivers classified as chalk streams globally, 160 are in England. A list of chalk streams in England gives a total of 224. Chalk is a highly porous and permeable rock, and rain falling onto chalk topography percolates directly into the ground, where the chalk layer acts as an aquifer . The groundwater flows through the chalk bedrock, re-emerging lower down the slope in springs . The chalk acts as

969-477: The Chess from fish farms and trout fisheries is the rainbow trout , thought to have been introduced to the Chess in the early 20th century. They have since gone on to establish one of a handful of self-sustaining populations in the UK. Some of the flow of the Chess results from the outflow of treated sewage from Chesham Sewage Treatment Works, which is material during dry conditions. During heavy rainfall, overflow at

1020-494: The Nile perch into Lake Victoria, possibly to improve sport fishing and boost the fishery. In the 1980s, the Nile perch population saw a large increase which coincided with a great increase in the value of the fishery. This surge in Nile perch numbers restructured the lake's ecology. The endemic cichlid population, known to have around 500 species, was cut almost in half. By the 1990s, only three species of sport fish were left to support

1071-399: The UK has caused the chalk streams to dry up. This has caused ecological damage and stagnant sewage that flows through the rivers and increasing phosphate levels. Although chalk streams are generally watercourses originating from chalk hills, including winterbournes , streams, and rivers, the term chalk stream is used even for larger rivers, which would normally be considered too large for

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1122-788: The Yangtze Basin. Many Yangtze fish species have declined drastically and 65 were recognized as threatened in the 2009 Chinese red list . The Chinese paddlefish , once common to the Yangtze River, is one of a number of extinctions to have taken place due to the degradation of the Yangtze, alongside that of the wild Yangtze sturgeon . Intentional anthropogenic reconstruction and rerouting of waterways impacts stream flow, water temperature, and more, impacting normal habitat functionality. Dams not only interrupt linear water flow and cause major geological channel shifts, but also limit

1173-551: The amount of water available to fishes in lakes, streams and rivers and have the potential to change the trophic structure because of these alterations of the habitat and the limitations to movement and connectivity. Unnatural water flow below dams causes immense habitat degradation, reducing viable options for aquatic organisms. Upstream migration is hindered by the dam structure and can cause population declines as fishes don't have access to normal feeding and/or spawning grounds. Dams tend to affect upstream species richness, that is,

1224-514: The best conditions for fly fishing , and most specifically, dry fly fishing . The chalk streams hold a good number of wild salmonid fish species such as the brown trout ( Salmo trutta ), and grayling ( Thymallus thymallus ). In addition to these there are also considerable numbers of stocked brown trout and stocked rainbow trout ( Oncorhynchus mykiss ). The rich invertebrate life and characteristic transparent shallow water make chalk rivers and streams particularly suited to fly fishing. Many of

1275-405: The bodily salt concentration on a level lower than the surroundings, and vice versa. Many species solve this problem by associating different habitats with different stages of life. Both eels, anadromous salmoniform fish and the sea lamprey have different tolerances in salinity in different stages of their lives. Among fishers in the United States, freshwater fish species are usually classified by

1326-615: The chalk stream springs are also used as sites for watercress production, due to the constant temperature and clean, alkaline , mineral-rich spring water. The Mid Hants Watercress Railway in Hampshire is so named on account of its use for transporting watercress to London from local chalk streams. A number of the chalk aquifers and associated groundwater sources related to chalk streams and rivers are used for water abstraction by local and national water utility companies. The over-abstracting of chalk streams by private water companies in

1377-580: The exotic species is suddenly introduced to a community, it does not have any established predators or prey. The exotic species then have a survival advantage over endemic organisms. One such example is the destruction of the endemic cichlid population in Lake Victoria via the introduction of the predatory Nile perch ( Lates niloticus ). Although the exact time is unknown, in the 1950s the Ugandan Game and Fisheries Department covertly introduced

1428-499: The extinction of the yellowfin cutthroat trout ( Oncorhynchus clarkii macdonaldi ) found only in the Twin Lakes of Colorado, USA. The yellowfin cutthroat trout was discovered in 1889 and was recognized as a subspecies of the cutthroat trout ( Oncorhynchus clarkii ). The rainbow trout was introduced to Colorado in the 1880s. By 1903, the yellowfin cutthroat trout stopped being reported. It is now presumed extinct. The rainbow trout

1479-436: The flow rate, mineral content and temperature range of chalk streams exhibit less seasonal variation than other rivers. They are mildly alkaline and contain high levels of nitrate , phosphate , potassium and silicate . In addition to algae and diatoms , the streams provide a suitable habitat for macrophytes (including water crowfoot ) and oxygen levels are generally supportive of coarse fish populations. Of

1530-808: The grounds that it was damaging to the local environment. The Chess Valley is partly within the Chiltern Hills Area of Outstanding Natural Beauty (AONB), with wildlife characteristic of chalk streams and chiltern hills. It supports several key species listed in the Government's UK Biodiversity Action Plan. Mammals such as the water vole , birds including the green sandpiper , grey heron , grey wagtail , little egret , osprey , mute swan , European stonechat , water rail and kingfisher , flora such as water crowfoot , purple loosestrife , hemp agrimony , water forget-me not and branched bur-reed . Freshwater fish , found include specifically

1581-460: The habitat functionality for many fish species and can reduce species richness, evenness, and diversity. Agriculture, mining, and basic infrastructural building can degrade freshwater habitats. Fertilizer runoffs can create excess nitrogen and phosphorus which feed massive algae blooms that block sunlight, limit water oxygenation, and make the habitat functionally unsustainable for aquatic species. Chemicals from mining and factories make their way into

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1632-471: The hands of another American import, the signal crayfish . Originally imported by the aquaculture industry, the signal crayfish was seen as a way for trout farms to diversify and exploit new markets. However, due to their expert, escapologist nature, signal crayfish soon escaped into surrounding river systems and quickly spread throughout the majority of the UK's southern river system. Signal crayfish have carried crayfish plague , to which they are resistant, but

1683-460: The mating of two genetically different species ( interspecific hybridization ). It is dangerous for native species to hybridize because hybrid phenotypes may have better fitness and outcompete the two parent species and/or other fishes in the ecosystem. This could irreversibly compromise the genetic identity of one or both of the parent species and even drive them to extinction if their range is limited. The rainbow trout discussed above hybridized with

1734-428: The native white-clawed crayfish is not. The result has been the gradual eradication of native crayfish from the UK's rivers. In the case of the Chess, white-clawed crayfish have been extinct since the mid-1990s. The Chess is also home to a number of invasive alien plant species including Japanese knotweed , Himalayan balsam and Orange balsam . Not all imports have quite such a catastrophic effect. Another escapee into

1785-470: The natural flint deposits found embedded within the chalk geology that contains relatively low amounts of clay and silt deposits. The unique characteristics of chalk stream ecology are due to stable temperature and flow regimes combined with highly transparent water and lack of sand grade sediment particles. The chalk streams have been intensively managed for many generations. In the 20th and 21st centuries, much of that management has been aimed at producing

1836-498: The number of fish species in the ecological community. Additionally, dams can cause the isolation of fish populations, and the lack of connectivity creates possible problems for inbreeding and low genetic diversity. The loss of connectivity impacts the structure of community assemblies and increases the fragmentation of habitats, which can compound existing problems for vulnerable species. Temperature alterations are another unintended consequence of dam and land use projects. Temperature

1887-422: The once multispecies fishery, two of which were invasive. More recent research has suggested that remaining cichlids are recovering due to the recent surge in Nile perch commercial fishing, and the cichlids that are left have the greatest phenotypic plasticity and are able to react to environmental changes quickly. The introduction of the rainbow trout ( Oncorhynchus mykiss ) in the late 19th century resulted in

1938-531: The river passes several disused water mills which supplied power and water for paper manufacture during the 18th and 19th Centuries. At Rickmansworth it joins the River Colne to the east of the town. The river banks are mostly not public rights of way, and only small stretches of the river are accessible. It is navigable only in its lower reaches. The river suffered from a severe lack of water for approximately two years between 2004 and 2006 and again in 2011 and 2012. Well below average rainfall over long periods

1989-580: The same basic models of speciation as when studying island biogeography . Freshwater fish differ physiologically from saltwater fish in several respects. Their gills must be able to diffuse dissolved gases while keeping the electrolytes in the body fluids inside. Their scales reduce water diffusion through the skin : freshwater fish that have suffered too much scale loss will die. They also have well developed kidneys to reclaim salts from body fluids before excretion . Many species of fish do reproduce in freshwater, but spend most of their adult lives in

2040-461: The sea. These are known as anadromous fish, and include, for instance, salmon , trout , sea lamprey and three-spined stickleback . Some other kinds of fish are, on the contrary, born in salt water, but live most of or parts of their adult lives in fresh water; for instance the eels . These are known as catadromous fish . Species migrating between marine and fresh waters need adaptations for both environments; when in salt water they need to keep

2091-472: The site of a 1st Century Roman villa close to the village of Latimer ; to the north of Chenies ; through unimproved water meadows at Frogmore and the watercress beds at Sarratt Bottom to the west of Sarratt . The Chess flows under the M25 motorway at Solesbridge Lane, before passing through the private housing estate of Loudwater , whose name was historically associated with the river at this point. Below this

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2142-524: The slope and thought to have been the site of medieval vineyards. Human habitation has altered the valley and the river in many ways, not all of them beneficial for wildlife. River modifications such as dredging and widening slow the current, allow silt to accumulate and smother the gravel riverbed. Changes in the land use adjacent to the river can also have impact. Water meadows have been replaced by arable fields and building developments, altering drainage patterns and causing pollution. Abstraction of water from

2193-653: The soil and go into streams via runoff. More runoff makes its way into streams since paved roads, cement, and other basic infrastructure do not absorb materials, and all the harmful pollutants go directly into rivers and streams. Fish are very sensitive to changes in water pH, salinity, hardness, and temperature which can all be affected by runoff pollutants and indirect changes from land use. Freshwater fish face extinction due to habitat loss, overfishing, and " forever chemicals ." Conservation efforts, sustainable practices, and awareness are crucial in maintaining fish populations and species diversity. An exotic (or non-native) species

2244-694: The term stream . The Somme in northern France is a chalk stream on a larger scale. Winterbournes are known by different names depending on region: Chalk streams of the Southern England Chalk Formation in Berkshire , Hampshire , Wiltshire , Dorset and the Isle of Wight : Chalk streams of the Southern England Chalk Formation in the Chiltern Hills , Hertfordshire and Surrey (tributaries of

2295-476: The underlying chalk aquifer reduces river flows and lowers the river's ability to tolerate drought. The introduction of alien species to the catchment has had a major effect on the wildlife of the river. Water vole populations declined catastrophically along the Chess between 2001 & 2003 with a 97% population decrease being observed. This population crash was caused mainly by the North American mink ,

2346-441: The water temperature in which they survive. The water temperature affects the amount of oxygen available as cold water contains more oxygen than warm water. Coldwater fish species survive in the coldest temperatures, preferring a water temperature of 50 to 60 °F (10–16 °C). In North America, air temperatures that result in sufficiently cold water temperatures are found in the northern United States, Canada, and in

2397-517: The works results in untreated sewage being released to the river. In 2014, a release persisting 5 months occurred, with substantial effects on river quality. Upgrade works to address the increased flow into the works have subsequently been completed. Historically, the clear chalk stream water of the River Chess, together with the fertile land, was ideal for growing watercress , and this industry which flourished in both Chesham and Rickmansworth in

2448-437: The world's freshwater fish species were at risk of extinction. A global assessment of freshwater fishes estimates an average decline of 83% in populations between 1970 and 2014. The protection of 30% of Earth's surfaces by 2030 may encompass freshwater habitat and help protect these threatened species. There is an increasing trend in freshwater fish for local taxonomic, functional, and phylogenetic richness in more than half of

2499-490: The world's rivers. This increase in local diversity is primarily explained by anthropogenic species introductions that compensate for or even exceed extinctions in most rivers. A study and an interactive map by EWG using its results show freshwater fish in the U.S. ubiquitously contain high levels of harmful PFAS , with a single serving typically significantly increasing the blood PFOS level. About four in ten North American freshwater fish are endangered, according to

2550-459: Was a contributory factor. Winter rainfall is particularly important for replenishing ground water. However, the exceptional rainfall in April and June 2012 allowed the ground water to slowly rise at a time of the year when ground water levels usually start to fall. Consequently, levels in the river Chess were showing signs of improvement by July 2012. Local speculation during the river drought of 2005

2601-402: Was that over-extraction for bottling, by Nestlé 's Powwow Water was a significant contributing factor. Indeed after extraction had stopped, and the river recovered somewhat, the bed was now so overgrown it was a struggle for the river to fully recover until much of the growth was removed by volunteers in 2012. In 2005 Councillor Justine Fulford campaigned to prevent the extension of the licence on

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