Cotehill Loch is a loch

Loch

Loch is the Irish and Scottish Gaelic word for a lake or a sea inlet. It has been anglicised as lough, although this is pronounced the same way as loch. Some lochs could also be called a firth, fjord, estuary, strait or bay...

 located in Scotland in the Aberdeenshire

Aberdeenshire

Aberdeenshire is one of the 32 unitary council areas in Scotland and a lieutenancy area.The present day Aberdeenshire council area does not include the City of Aberdeen, now a separate council area, from which its name derives. Together, the modern council area and the city formed historic...

 area, approximately one mile (1.5 km) northwest of the coastal town of Collieston

Collieston

Collieston is a small former fishing village on the North Sea coast in Aberdeenshire, Scotland. The village lies just north of the Sands of Forvie Special Protection Area, between Cruden Bay and Newburgh.-History:...

 and two miles (3 km) east of the Ythan Estuary

Ythan Estuary

The Ythan Estuary is the tidal component of the Ythan River, emptying into the North Sea approximately north of Aberdeen, Scotland. The estuary’s tidal action extends a full inland and has characteristic widths of between and . Besides the tidal channel there are several types of interfaces to...

. The area the loch covers is 2.7ha.
A survey carried out in 2002 by ecologists from the University of Glasgow

University of Glasgow

The University of Glasgow is the fourth-oldest university in the English-speaking world and one of Scotland's four ancient universities. Located in Glasgow, the university was founded in 1451 and is presently one of seventeen British higher education institutions ranked amongst the top 100 of the...

 found that the eutrophication

Eutrophication

Eutrophication or more precisely hypertrophication, is the movement of a body of water′s trophic status in the direction of increasing plant biomass, by the addition of artificial or natural substances, such as nitrates and phosphates, through fertilizers or sewage, to an aquatic system...

 of the water was leading to a "decline in plant species diversity". It was noted in the same study, that the loch's "marginal vegetation" of reedswamp grasses and other plants present around it were still "flourishing".
The loch is said to contain three-spined stickleback

Three-spined stickleback

The three-spined stickleback, Gasterosteus aculeatus, is a fish native to much of northern Europe, northern Asia and North America. It has been introduced into parts of southern and central Europe.-Distribution and morphological variation:...

 and perch

Perch

Perch is a common name for fish of the genus Perca, freshwater gamefish belonging to the family Percidae. The perch, of which there are three species in different geographical areas, lend their name to a large order of vertebrates: the Perciformes, from the Greek perke meaning spotted, and the...

.