Capítulo 2. Los estudiantes de postgrado y el personal docente e investigador como usuarios de la biblioteca
2.2 Las características de los estudiantes
Main survey 1977-79 1984-86 1991-94 2000-02 2009-10
Positive sites/total - 77-79 sites - all sites 14/169 17/169 17/174 45/169 46/174 85/169 90/174 135/169 140/174 % Positive - 77-79 sites - all sites 8.28% 10.06% 9.77% 26.62% 26.44% 50.30% 51.72% 79.88% 80.46% Spot-checks were carried out in an additional 61 whole or partial 10km squares.
Alternate 50km Square NT n/e NU s/w NY n/e NZ s/w
Positive/total 10km squares 1/1 13/14 20/21 25/25
Summary of results for each catchment Cheviot/East Northumberland (16)
Main survey 1977-79 1984-86 1991-94 2000-02 2009-10
Positive sites/total 13/86 14/86 33/86 63/86 79/86
The surveys and the alternate squares spot-checks show that otters in this area now use all the available watercourses, even small coastal streams like the Embleton Burn, and the coast. The very small number of negative sites in the area are either on very small streams such as the Portland Burn or at coastal sites which were difficult to survey adequately.
Tyne (17)
Main survey 1977-79 1984-86 1991-94 2000-02 2009-10
Positive sites/total 0/39 1/39 9/39 17/39 26/39
The surveys and the alternate squares spot-checks show that otters have now re-colonised most of the available watercourses. The small number of negative sites in the catchment are on very small streams or at coastal sites which were impossible to survey, and were thus assumed to be negative, or those which were very difficult to survey adequately. The upper part of the catchment was only surveyed as part of the alternate squares spot-checks but these show that otters are present on all the major watercourses and at least some minor streams.
Wear (18)
Main survey 1977-79 1984-86 1991-94 2000-02 2009-10
Positive sites/total 0/15 0/15 0/15 3/15 8/15
The surveys and the alternate squares spot-checks show that the otter population in the catchment has now expanded to re-occupy all the available watercourses. The small number of negative sites are either on very small streams or at sites at which access was refused and were thus assumed to be negative. An alternate squares spot-check on the Hawthorne Burn and local surveys (T. Coult, pers. comm.) show that otters are now using some of the small coastal streams or ‘denes’ where cover is good but fish stocks are small. It seems likely that otters are accessing these from the sea and probably finding prey on the coast as well.
Main survey 1977-79 1984-86 1991-94 2000-02 2009-10
Positive sites/total 0/29 2/34 4/34 7/34 27/34
There has been a major expansion in range in the headwaters of the Tees. The otter population now uses all the available watercourses within the surveyed area. The alternate squares spot-checks show that they are also widely distributed within the rest of the
catchment.
Discussion
There has been a further major expansion of the range of otters in the Northumbrian Region since the last survey and otters are now using all the available watercourses and much of the coast. However while otters now use the overwhelming majority of the rivers and streams in the region, this has happened relatively recently and it is unlikely that otters are yet at carrying capacity (see section 6.4). It is however likely that they will reach this level within a very few years if current trends continue.
Otters appear to be using the whole of the coast in this region with otter signs found on the Tweed estuary, at Holy Island and at coastal streams further south, including small coastal streams or ‘denes’. Some of these are quite isolated from the river network so otters are almost certainly accessing these from the sea. They provide a source of freshwater and have good cover for lying up but can have only a small prey resource. It is therefore assumed that otters are also using the sea for foraging in these areas.
4.3 Yorkshire Region
Surveys were carried out in the following 50km squares – NY s/e (4), NZ s/e (25), SD s/e (13), SE n/w (129), SE s/e (81), SK n/w (18), TA n/w (14).
Description of region
The majority of the rivers in the region arise in the Pennines, although the Derwent and Esk arise on the North Yorkshire Moors. In their headwaters all these rivers have steep
gradients, but soon reach the more low-lying areas through which they meander to reach the Humber Estuary, with the exception of the Esk which flows directly to the North Sea at Whitby. The floodplains often provide high quality arable farmland, most of which is intensively farmed, while much of the upland area is moorland, including the North Yorks Moors, and there are some large conifer plantations. The River Derwent has been
designated a Special Area of Conservation (SAC) with otters as a qualifying species. The human population is concentrated mainly in the south of the region in the older industrial and mining centres of Leeds, Sheffield, Bradford, Huddersfield, Doncaster, Rotherham, Barnsley and Halifax but there are also the urban centres of Hull, York and Harrogate. This region now forms, with the Northumbrian Region, part of the Environment Agency North East Region. Different northern boundaries of the Yorkshire Region have been used in the reports of past surveys. In this survey, as in the 2000-02 survey, Yorkshire Region is taken to include the Easington Beck but not the Kilton Beck.
Water quality
The northern part of the region is mainly upland and agricultural generally with good water quality although some rivers suffer from acidification and agricultural runoff. The southern part of the region, with a long history of industry and mining, has had serious pollution problems in the past but water quality is now generally good although some problems from minewater seepage and episodic incidents of industrial and sewage discharges persist.
Fisheries
Populations of coarse fish and trout in the rivers of South and West Yorkshire have
increased markedly following reductions in pollution and improvements to habitat. Salmon and sea trout are now returning in good numbers to rivers like the Ure and most rivers support healthy populations of coarse fish. Eel numbers have decreased drastically in the region but they are still present in the lower and middle reaches of most rivers. Ongoing work to improve fish passage for all species should see populations continue to improve.