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centrum

Fish swimming this way

top spine

bottom

spine

zyg

Analysing Otter Spraint – getting started

These instructions are intended as a quick route into the fascinating world of otter spraint analysis.

There is a host more information available on our website. (https://suffolkotters.wordpress.com)

Collecting and cleaning spraint

All sorts of animals use otter sprainting places including rats. Be meticulous about protecting any cuts

and washing hands after collecting or handling spraint. Latex gloves are advised. We assume you know

what to look for but if in doubt do not collect it. If it smells horrible it isn’t otter. To begin with

concentrate on those with visible fish bones.

We collect our spraint in small deli pots. We put self-adhesive labels before going into the field and

always write the date and location in pencil when we collect the spraint. The spraint is then soaked in

the pot with a teaspoon of biological washing powder and just enough water to cover the spraint. They

need to be left for 24 hours but do not come to any harm if left longer. They are sometimes easier to

clean if left longer. They are washed in a kitchen sieve, (definitely a different one from the one you use

in the kitchen). The cleaner they are the easier they are to identify – so don’t skimp on the cleaning.

We air dry on newspaper. If you are

doing lots at the same time beware of

confusing which spraint goes with

which pot. When fully dry they go

back into the pots until ready for

analysis.

Analysing Spraint

For analysis, most of us use digital microscopes attached to a laptop. A circle of

black card in the bottom of the petri dish makes for better viewing. The

microscopes take pictures which helps us to share difficult-to-identify bones.

Binocular microscopes have better 3D viewing but are more expensive and

usually do not have a camera function.

Do not put too much material in the petri dish at one time and remember you

are not trying to identify every single bone. Concentrate on vertebrae and scales since each spraint will

have loads from each fish. Some vertebrae come from near the tail and are difficult and some are

chewed – ignore them. Feathers and fur we record as bird and mammal respectively. Going further with

your ID is for another day. The following sheets should give you a good start.

All our spraints are checked by two different people.

Technical terms Centrum – the central part of the vertebra. Spines – (1) the long bits of bone sticking off the centrum,

(2) (another meaning) the spiky things on a stickleback’s back and sides.

Zyg (full name – zygapophysis, plural zygapophases) can be at all 4 corners of the centrum. Their size, shape and position are important diagnostic features.

Note - All the vertebra pictures below are as if the fish is swimming from right to left.

Fish vertebra (back bone)

ridge

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Freshwater fish species – basic info for a start Stickleback - One of our commonest fish species. They do not have scales. We get 3- and 10- spined and, as we cannot always be sure which is which, we record them on our database as 'stickleback.’ You will find details later for how to tell the difference - at this stage do not bother. Most of the vertebrae have a large hole.

Vertebra

Spines Spines’ base plate – like a face mask

Cyprinid - The carp family are difficult to identify to species. They include rudd, roach and bream. We group them together on the database. The circular scales are distinctive as they often break up into triangular sections. The vertebrae have a prominent ridge along the sides of the centrum. Both the spines come from the front and the front top zyg points upwards. They are the only family which have a set of extra teeth in their throat known as pharyngeal teeth. These are very distinctive.

Scales Vertebra

Pharyngeal teeth

Perch - The scales are very distinctive. The vertebrae are difficult - especially if you also get bullhead.

Pike - Vertebra with no spines. Very distinctive oblong-ish scales.

Vertebra Scale

Eel - No scales but very distinctive vertebrae with top and bottom spines coming from different ends of centrum

Stone Loach Vertebra - knobbly appearance and boot-shaped zyg.

Bullhead - No scales. Top spine tapers from a broad base. Prominent front top zyg. Distinctive hook-shaped operculum bone (hard bony flap protecting the gills).

Salmonid (Salmon, trout family) Honeycombed centrum - contrasts with v. smooth front and rear margin.

Vertebra Salmonid

Operculum

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Non-fish prey items - fresh water and estuarine Amphibian Frog - Vertebrae a distinctive shape. Bones look more solid than fish bones. (Not sure we can tell toads and frogs apart)

Teeth

Vertebra

Crustaceans

Shrimp - pieces are squidgy when grasped with tweezers.

Bird - Feathers. We haven’t found an easy way to tell bird species apart so we lump them together in the database.

Crayfish – Not found near coast. Usually it’s signal crayfish. Shell fragments obvious – bright red/orange.

Mammal – Fur. Otters swallow some of their own fur through grooming. Identifying fur is difficult so we lump mammals together in the database.

Crab - Only found near coast/estuary. Eyes distinctive.

Insects Fly larva - Beware. These are laid on the spraint after they’ve been deposited.

Beetle - Wing cases

black/ brown, shiny, and v hard

Newt and grass snake will be dealt with in another document

Foot

Eye

Fur

Teeth (vole)

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Brackish/estuarine fish Goby Vertebrae very small. Scales - (not commonly found) can be confused with perch. Goby scales have more ‘fingers’ and they are more deeply cut.

Warning - do not confuse this

scale with perch

Flatfish Centrum looks rectangular, vertically, and has long spines, often broken. The most distinctive feature - little projections on sides - like tiny stabilisers. (Turn it on end to

see)

Vertebra side view

Rockling

V distinctive, strongly-waisted centrum. Fin-like rear zyg. Other members of the cod family are possible, but in our estuaries rockling are the most common.

Blenny/ Eelpout (same thing) Bones sometimes greenish. The vertebrae have a prominent ridge along the sides of the centrum.

Other estuarine species crop up and will be dealt with in another document.

Vertebra

Vertebra –

top view

Scale

You are welcome to use this guide in any way you want.

Please let us know if you improve on it.

More advanced help with identifying species can be found on our website:

https://suffolkotters.wordpress.com.

Contact us through the website.

Many thanks to photographers Arthur Rivett, Gill Hammond, Richard Woolnough,

Dennis Brown, Rodney West, Nicky Rowbottom.