Oback Burn, Olav's Wood, South Ronaldsay.  SEPA Ecology Sampling 9th October 2013
Sample Number	2367531	2376227
Location	500113	500112
Location Description	Oback Burn d/s minor road to Windwick	Oback Burn d/s Hestly
Date Sampled	09-Oct-13	09-Oct-13
BMWP Score	75	80.00
Number of Scoring Taxa	15	17.00
ASPT	5	4.71
Taxon name	Abundance	Abundance	BMWP score	Type
Leuctridae	30	200	10	Stonefly - rolled wing
Polycentropodidae	50	20	7	Caseless Caddis Fly
Limnephilidae	10	5	7	Cased Caddis Fly
Glossosomatidae	1	x	7	Cased Caddis Fly
Hydroptilidae	x	2	6	Cased Caddis Fly
Gammaridae	50	100	6	Freshwater Shrimp
Dytiscidae	x	1	5	Diving Beetle
Elmidae	50	20	5	Riffle Beetle
Hydraenidae	2	x	5	Moss Beetle
Scirtidae	50	5	5	Aquatic Beetle
Simuliidae	10	10	5	Black fly larvae
Tipulidae	10	10	5	Crane fly larvae
Pediciidae	10	10	5	Crane fly larvae
Baetidae	20	5	4	Mayfly (Blue windged olives)
Glossiphoniidae	x	1	3	Leech
Hirundinidae	x	1	3	Horse Leech (Haemopsis sanguisuga)
Hydrobiidae	50	30	3	Snail
Sphaeriidae	1	50	3	Freshwater Cockle
Chironomidae	30	20	2	Non-biting Midge larvae
Oligochaeta	30	20	1	Worms
Hydracarina	5	x	0	Mite
Note:
Horse Leech (Haemopsis sanguisuga)
Despite the name, it does not attack horses and indeed cannot bite mammalian skin at all. This species can be quite large, reaching up to 15cm. Their greenish colour and size helps to identify them
They feed on smaller animals such as midge larvae and snails but sometimes move onto land in search of earthworms. They are very sensitive to chemical traces in the water and find their prey this way
Widespread and common though under recorded in Britain