A TweedStart Resource
Key to the Freshwater Fish Species of the Tweed Catchment
Look at the two pictures of fish above. Use the Family key pages 1, 2 and 3 to identify the family the fish belongs to. Then go to the page shown for that family to identify the species of fish.
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Page 1 Family Key
The Lamprey Family No eyes
Lampreys are thin “snake like” like fish. They look like eels but have no eyes and no fins immediately behind the head.
no fins behind the head
Go to page 4
Has eyes The Eel Family
Eels are thin “snake like” like fish. They look like Lampreys but can be told apart as Eels have eyes and have fins immediately behind their head. fins behind the head
Go to page 5
The Carp Family Dorsal fin
The dorsal (back) fin varies in size but is mostly towards the rear of the fish. If barbels are present on the mouth there will be less than five.
Go to page 6
The Loach Family
Small fish with several barbells around the mouth. They generally are a “mottled” colour. Barbells Go to page 7
2
Page 2 Family Key
The Pike Family Dorsal fin Long slender fish with a large head and mouth. The dorsal (back) fin is located towards the tail end of the fish.
Go to page 7
The Salmon Family Adipose fin
Small, fleshy adipose fin present, mouth in middle of head.
Go to page 8
The Grayling Family Dorsal fin Adipose fin
Small, fleshy adipose fin present, mouth on underside of head. Very large dorsal (back) fin.
Go to page 9
Three spines The Stickleback Family
Small fish with three spines on its back.
Go to page 9
3
Page 3 Family Key
The Goby Family
Small fish with very large head and mouth. Pectoral fins (just behind the head) large and rounded.
Go to page 9
The Perch Family
Large dorsal (back) fin with numerous spines. Fins on underside of fish are often orange coloured.
Go to page 10
The Flounder Family
Fish completely flattened with both eyes on the one side of the head.
Go to page 10
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Species Key Page 4
Lamprey Family: Petromyzontidae
There are three different species of Lamprey in the River Tweed system; River, Brook and Sea Lampreys. River and Brook Lampreys can’t be told apart without the use of a microscope. However Sea Lampreys can be distinguished from River & Brook Lampreys by looking at the tail.
The fin around the end of the tail is clear/yellowish = River or Brook Lamprey
The fin around the end of the tail has black pigment spots = Sea Lamprey
Sea Lamprey Petromyzon marinus Native
River Lamprey or Brook Lamprey Lampreta fluviatilis or Lampreta planeri Both Native
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Page 5
Eel Family: Anguillidae
There is only one species of Eel in the Tweed system – The European Eel.
European Eel Anguilla anguilla Native
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Page 6
Carp Family: Cyprinidae
Roach Rutilus rutilus Introduced
Obvious, large scales visible. Fins on underside of fish are orange.
Tench Tinca tinca Introduced
Has a “greenish appearance”. No obvious, large scales.
Common Gudgeon Gobio gobio Introduced
Has Barbells on its mouth, a small dorsal fin and has dark “patches” on its side.
Common Carp Cyprinus carpio Introduced
Has barbells on its mouth, a large dorsal fin and no “patches” on its side.
Dace Leuciscus leuciscus Introduced
Small fish with large, obvious scales. Fins on underside not orange.
Minnow Phoxinus phoxinus Probably Introduced
No large obvious scales. Black “stripe” down side of fish. Males can develop dark red colour around head at spawning time.
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Page 7
Loach Family: Balitoridae
There is only one species from the Loach Family in the Tweed system – The Stone Loach.
Stone Loach Barbatula barbatula Introduced
Pike Family: Esocidea
There is only one species from the Pike Family in the Tweed system – The Pike.
Pike Esox lucius Introduced
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Page 8
Salmon Family: Salmonidae Gill Cover Adipose fin
Atlantic Salmon Salmo salar Native
Tail very forked. Usually only one or two large spots on the gill cover. Fins usually not orange.
Gill Cover Brown/Sea Trout Salmo trutta Native
Tail only slightly forked if at all. Usually lots of spots on gill cover. Tail and adipose fins usually have some orange colouring.
Adipose fin
Rainbow Trout Oncorhynchus mykiss Introduced
Numerous small spots on tail. Pink stripe runs down the side of the fish.
Arctic Charr Salvelinus alpinus Native
Numerous spots all over the body but not on fins. Males often have an orange belly and white tips to the fins.
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Page 9
Grayling Family: Thymallidae Adult Grayling
There is only one species from the Grayling family in the Tweed system – The European Grayling.
European Grayling Thymallus thymallus Introduced Juvenile Grayling
Stickleback Family: Gasterosteidae
There is only one species from the Stickleback family in the Tweed system – The Three Spined Stickleback.
Three-spined Stickleback Gasterosteus aculeatus Native
Goby Family: Cottidae
There is only one species from the Goby family in the Tweed system – The Common Bullhead
Common Bullhead Cottus gobio Introduced
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Page 10
Perch Family: Percidae
There is only one species from the Perch family in the Tweed system – The European Perch.
European Perch Perca fluviatilis Introduced
Flatfish Family: Pleuronectidae
There is only one species of Flatfish found in the Tweed system – The Common Flounder.
Flounder Platichthys flesus Native
SCN 2-01a
KS2 Science – classification – give reasons for classifying animals based on specific characteristics.
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