Welcome to the Nethan Valley Association Hatchery and Angling

Pond Life

Mud Snails (Lymnaea glabra) The mud snail is a west European species of local distribution. In Britain it was formerly fairly widely distributed throughout the acidic lowland areas of England, Wales and Scotland as far as Perth. It is now rare, with the largest concentration of records coming from the southern part of the Vale of York. This species has become extinct over large parts of lowland England and shows continuing decline. A three year survey (1995/6/7) of 370 ponds in the Cheshire region found the mud snail to be present in only three ponds. (Pond Critical Biodiversity Survey: 1997).	Smooth Newt (Triturus vulgaris) Conservation status: Although they are protected in Britain under the Wildlife and Countryside Act 1981, their numbers continue to decline across Europe. They are vulnerable to urbanisation, agricultural change and pollution of their habitat. They are not listed by the IUCN. They are nocturnal and spend the day hiding under large stones or compost heaps. Adult newts shed their skin as often as once a week. They emerge from hibernation in February or March, when the temperature is above 0 degrees Celsius and conditions are moist, and head for the breeding sites. They return to land in late July. They are one of the most terrestrial of the newts in Europe. As the grow, smooth newts shed their skin once a week.	Great Diving Beetle (Dytiscus marginalis) Nymph with tadpole in pincers. Great Diving Beetle larvae are the young stage of a large water beetle. They live in freshwater ponds and are fierce carnivores. The large, pointed, sickle-shaped jaws are sunk into the prey like hypodermic needles. Digestive enzymes are pumped into the body of the prey and the resulting 'soup' is sucked back up. Great Diving Beetle larvae will eat anything they can catch. Their favourite prey includes tadpoles and any other insects within reach. They are also cannibalistic and will eat other Great Diving Beetle larvae. Large larvae in the final stage before pupation, are of sufficient size to even catch and eat small fish. The larvae often appear scorpion-like in the water because they move about with their tails extended vertically upwards. They will frequently push the tail up through the water surface to take in atmospheric oxygen through the terminal spiracle (air-hole).
Large Stonefly (Perlodes microcephala) Although common in many rivers, the large stonefly nymphs live beneath stones and hatch into winged adults by crawling onto exposed rocks in the shallows. It is difficult to mimic this behaviour with an artificial fly. The nymphs prefer well oxygenated water, and in warm weather they often congregate in the fast riffles. They take two years or more to reach maturity, unlike many of the smaller species which have a one-year life cycle. Trout rummage among the smaller stones to disturb stonefly nymphs from their hideouts. These big flies appear from the end of March until the middle of June, with the peak of the hatch usually occuring in May. The males have very short wings and are unable to fly, and so the females go about the business of courting before they fly across the river and dip down to lay their eggs.		Tadpoles (pollywog, a larval amphibian) How to care for tadpoles. During the tadpole stage of the life cycle the tadpole breathes by means of autonomous external or internal gills. It does not have arms or legs or reproductive organs until later stages in its life, and has dorsal or fin-like appendages tail with which it swims by lateral undulation, similar to most fish. As a tadpole matures, it metamorphoses by gradually growing limbs and then (in the case of frogs) outwardly absorbing its tail by apoptosis. Lungs develop around the time of leg development, and a tadpole late in development will often swim to the surface of the water to breath air. During the final stages of external metamorphosis, the tadpole's mouth must change from a small round mouth at the front of the head, to a large mouth the same width as the head. The intestine will shorten to accommodate the frog's carnivorous diet.

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