Fish of the River

RIVER LIFE

As a river that passes through some interesting and complex geology and topography and areas of land and habitat so unique in the cotext of country that it was worthy of inclusion in the Dartmoor National Park, it is no surprise to find it supporting a diverse array of life. Here are a few key species that occur within the catchment and that in some way tell the story of the river.
Since this project focuses on fish, two species in particular it makes sense to start with them.

FISHES

'THE LEAPER' - the ATLANTIC SALMON

Altlantic Salmon ©Alister Kemp
Altlantic Salmon ©Alister Kemp

ATLANTIC SALMON (Salmo salar) is the fish of most concern to us here at the River Teign Restoration Project but paradoxically probably also one of the most widely distributed of its family. It is a true Icon of the wild (it is also the fish that features in our project logo). As a species, it has both provided for us and astounded us in equal measure. Everyone has heard of Salmon even if they’ve never seen a live wild one. Part of its fame as a fish is probably down the heroics of its migration; famous for leaping waterfalls and navigating obstacles - and for those brief moments in time, it’s a fish that leaves its mysterious world beneath the surface and briefly enters our own air-breathing realm.

Its return journey back to the water in which it spawned is legendary and epitomises a sense of loyalty, continuity and the struggle of life winning out against the odds. It also tastes nice and is large and spectacular.

For all of these virtues, it’s understandable the Atlantic Salmon is sometimes referred to as ‘the king of fish’. It is also known as ‘the leaper’ in fact its scientific name - says just that. 'Salmo' - is from the Latin for Salmon which probably derives from the word salire - which means to leap in Latin and in case you didn’t get the message the salar bit - means exactly the same!

 

Atlantic Salmon on the way home © Jack Perks

Salmon belong to a family of fish called Salmonids. But not all Salmonids are Salmon (see Brown and Sea Trout). As a family of fish, we have seven native species and a handful of introduced and naturalised ones. They all share some of the necessary qualities of being predators namely, a slender, streamlined shape - honed to hydrodynamic perfection for speed and manoeuvrability. They have a relatively large eye (all the better to see you with) and a large mouth which in all species (except the gummy Grayling) have rows of stout, sharp teeth (all the better to eat you with!).
Salmon are also famous for being a fish of both the Sea and Freshwater, a life-cycle split between these two very different kinds of waters, travellers between habitats, between countries, so let us start at the end.
The bit most folk know a bit about is their return to their spawning grounds. The clean, fast-flowing well-oxygenated gravel lined upper reaches of their home river, the very place they were themselves deposited as eggs.
They aim to get to these sacred places during the winter months when the water is cold and crisp and the gravel beds are flushed with a good flow of water. The exact timing depends very much on the characteristics of the river and of course the seasonal weather. But it is usually in the months between November and January. It’s tempting to think like a human and imagine how to time a journey, like going for a drive or a walk. You know how far it is to your destination and you know the speed you can go and so you leave at the right time to allow you to achieve the journey in the given time. It’s not like that for a Salmon. They can enter the river's estuary from the Sea at almost any time of the year - although the peak times coincide with the highest chance of high water flow, especially in rain-fed ‘spate’ rivers with an upland headwater. These rivers make the best kind of Salmon rivers and their levels can quickly rise and just as quickly fall. The best times for a Salmon to head upstream is therefore in the Spring and in the Autumn.

Once a Salmon has entered freshwater - it changes. Not just in appearance. It loses the silver qualities of its scales and it changes colour, the way its body chemistry handles the change from saline to fresh water and most surprisingly its digestive system deteriorates. This means as soon as they enter freshwater, they stop feeding. No matter whether they are in the river for 7 months or 1 they are living off fat reserves laid down within their bodies. Which explains why the Spring running fish, which will stay in the river the longest are often the largest.

Atlantic Salmon © Geoff Simpson
Atlantic Salmon © Geoff Simpson

"...Who has not seen the scarus rise, decoyed and killed by fraudful flies…”

Marcus Valerius Martialis (AD 86 and 103)

 

It’s one of the biggest mysteries in nature. Why will a Salmon take a Fishermans fly? Nobody really knows what it is that makes an animal that has lost the ability to consume food, still show an interest and on occasions rise for a Fishermans artificial fly.
The whole sport of fly fishing for Salmon relies on this behaviour and yet there is no convincing explanation! Maybe a hazy memory of life before, an irritation or affront to the Salmons sense of being and order. The most plausible is that it is an instinctive feeding reaction that fades and attenuates as the fish becomes sexually mature, who knows for sure but rise they do and have been doing enough to justify a sport that is probably a couple of thousand years old.

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The Final Fling

As the Salmon enter the river they start to mobilise their fat reserves laid down while at sea. This fat often contains pigments derived from crustaceans in their marine diets and this results in their bodies flushing variable amounts of pink, brown and red, which combined with the spots of red and black and variable amounts of intricate patterning. In particular, a Cock Salmon (male) in full courtship regalia is a thing of spectacular handsomeness. Simultaneously to this pigmentation, other changes occur.

His head distorts - jaws no longer needed for feeding elongate and become hooked, the teeth longer and more protrusive. This hardware is put to an alternative use as the Cock fish morph into living battering rams, defending a patch of suitable gravel from other males at their final destination, the end game to their long journey - the breeding grounds.
When a Hen arrives the Cocks compete for her attention and persuade her to visit their particular path of clean well-aerated gravel, a shimmering, shivering courtship ensues.
The perfect substrate for spawning is a nice dense bed of gravel with an individual particle size that falls between 20-60mm in diameter in shallow fast-flowing water. When all the requirements fall into place the hen then begins to create a Redd. This is a depression in the gravel that is caused by her repeatedly turning on her side and fanning and thrashing her body against the gravel
The process of landscaping the gravel also has the added effect of flushing out finer silts, sands and segments that get carried away downstream. She then releases her eggs - smooth pink buttons of perfection, numbering some 450-750 eggs for every 0.45kg of her bodyweight. The male is in close attendance at this time and as she releases her eggs, he mirrors her behaviour and releases his milt liberally. A shivering flank, a puff of milky fluid, his job is done. Some of this milt will meet and fertilise the eggs before they sink and settle into the gaps between the stones. She’ll repeat this several times before completing the job by thrashing a little upstream - which has the effect of displacing more stones that drift down on the current and start to heap up over the fertilised eggs.

Depending on her size and the number of eggs she contains she’ll repeat this, sometimes in different places sometimes in the same spot, sometimes with the same Cock fish in attendance sometimes not. The eggs are now safely embedded deep in the safety of the gravel. Where they will spend the winter months.
Most of the fish, their job done, their life-cycle turned full circle now die. Weakened by the demands of their long and arduous journey they give up. These Kelts as they are called are spent and used up and most now die. Their bodies decomposing and further feeding the river. Nutrients harvested as far away as Greenland, now fertilise our river so that even in death they invest indirectly in the survival of their young by providing food for plants and therefore the insects and smaller lives that will over the next few years become fodder for fry, parr and smolt. (More about what these are in a bit).

Who’s your Daddy?

There are much smaller and sneaky interlopers gate crashing the spawning cresendo at the gravelly Redds. They're are called precocious Parr and they are just that, juvenile male salmon that don’t go to sea, staying small while their sexual organs mature. Their strategy is to wait until the final climax when the Hen fish releases her eggs and quickly nip into the frenzy of thrashing, shivering and nudging big fish and release their own milt into the soup. It might seem like cheating but the simple fact that this strategy exists must mean it works! But there must be some kind of trade off otherwise all Cock salmon would be small. It has been shown that with 20% of their small bodies dedicated to their testes they don’t have the fat reserves to survive hard winters and the data of winter survival of these precocious fish compared with normal Parr is less. They use much more energy. Their small size also makes them prone to predation by nearly every fish-eating predator on the river.

The next part is subtle and secret but every bit as essential to the process of making a Salmon as all the things you already know about migration and leaping. The eggs now tucked away in the interstitial spaces between the particles of gravel develop slowly over the winter. Hidden from predators and the turmoil of winter spates, the cool oxygen-rich water passes over them. These small pinkish spheres (some 5mm or so in diameter) very soon show the black specks of eyes.

Atlantic Salmon (Salmo salar) parr © Jack Perks

Sometime in the early spring, the eggs hatch. They are known as alevins at this stage and are still pretty inactive. They remain within the gravels and feed on their bulbous yolk sac, which they slowly absorb. When this has been fully consumed usually around April-May they need to find their own nutrition and become more mobile. They begin to swim up and out of the gravel - they look more like fish at this stage and are appropriately called ‘swim-up' fry and it is now that they start to depend on another aspect of the river, the invertebrate life it contains. The fry, no more than a few centimetres long at this stage are voracious predators of almost anything that can get in their mouths and they grow quickly. Within a matter of weeks, they begin to show pigments and patterns on their flanks. They are now called Parr and just like the closely related trout Parr they have a set of banded markings down their sides which look a bit like inky thumbprints.
They stay as Parr usually for one to three years, feeding on the hidden bounty of the river. They like the faster riffles and while they are often clustered in favourable parts of the river they are quite territorial, holding reign over their own little patch of the water, from which they eke a living, picking out morsels swept by on the current.

Atlantic Salmon (Salmo Salar) © Jack Perks
Atlantic Salmon (Salmo Salar) © Jack Perks

When the time is right and at some Environmental cue they undergo yet another change and begin the Seaward journey, downstream. This process of getting ready for a life in the ocean is known as ‘Smoltification’ and occurs internally. They change the way their body functions most notably their ability to pump salts across their gill membranes, this change is also marked by a change in behaviour and colouration. They start to shoal, and they lose their Parr marks, laying down a coat of silvery scales, before swimming downstream. They remain in the estuaries adjusting to their new life before heading out to sea.

Their seagoing stage is when they put on bulk, feeding on the rich bounty of crustaceans and smaller fish, they travel in schools. This is where Salmon as we tend to think of them are made. Our Salmon can travel far, South West of Greenland and the Norwegian Sea are two of the prime areas identified.
After anything from one to four years at Sea, they then begin their migration back to their home river to spawn. Fish that only spend a single Winter at Sea are called Grilse and don’t travel as far probably straying no further than the Faroe Islands and the southern Norwegian Sea. While those that stay in the marine environment for longer make bigger journeys, become bigger fish and enter our rivers earlier - these are the Spring run fish.

The cycle is now complete.

salmon-lifecycle1-1

 

The adaptability of the Salmon is what makes them such survivors and while what we have described is the standard life-cycle they will and do break their own rules. Some fish (a tiny percentage the number of which varies from river to river, year to year) live to spawn again. It is mostly Hen kelts that do this. Other returning fish can stray into other estuaries a mechanism that means they can recolonise habitat that has for whatever reason been lost to the fish historically.
Some that can’t make it to their home patch whether by becoming trapped in another part of the river or their access is blocked by a dam (natural or manmade) can spawn in the next available suitable habitat. The fact that not all fish of a year group return to the river in the same year is a further ecological insurance policy.

Atlantic Salmon (Salmo salar) © Jack Perks
Atlantic Salmon (Salmo salar) © Jack Perks

Brown Trout & Sea Trout

The same but yet so completely different

Brown Trout and Sea Trout (Salmo trutta) this is the other Salmonid found in the River Teign. Now straight away this statement needs explaining, this is not a typo and is meant to be singular because a Brown Trout and a Sea Trout are the same things. Both genetically identical, it is the same species - the only difference is at some point in their life cycle a genetic switch is flicked and they change their life strategy and behave differently. Sea Trout and Brown trout are fish that have made two very different life choices.
So what is their story? It makes sense if you think back to the Salmon life-cycle because the Sea trout has a very similar story to tell, with just a few minor differences that we’ll get onto later. So let’s start with the juvenile stages the Fry and the Parr, they have one job to do and that is to grow up and mature and the building blocks that make a Salmon are other animals; A multitude of handy protein packages exists in a healthy river and young trout are ravenous for them; invertebrates, such as various river flies, worms, crustaceans and other smaller fish and fry all form important parts of their diet. If there is plenty to go around then it makes sense for the fish to stay put, in a habitat that they know and therefore they can find the best hiding and feeding spots in it. No point in risking being spotted by moving around and you might end up in the worst habitat than the one you started in.

The Vagabond Trout

However, if there is not enough food, then you’ve nothing to lose. These young trout adopt a do-or-die attitude. It’s thought that this ‘decision’ is made by a combination of genetics and environmental factors. If they cannot get enough food, their energy levels drop below a threshold and this, in turn, turns on the genes for travelling. In short, a genetic switch is flicked and what would have become a homie Brown Trout, turns into a vagabond and goes looking for better supplies. This is when just as with their regal cousin the Salmon they undergo a process of ‘Smoltification’ and they metamorphose into an animal that starts to look and behave differently.

It’s easy to think of Brown trout as being the default and the Sea Trout as something a bit special - but it’s probably best to think of it the other way around. After the ice-sheets of the last glacial period retreated North, Britain's rivers, including the Teign, would have started fishless - and it would have been a slow process of colonisation that occurred, the original Trout would have colonised from the Sea and only then when some decided to stay put did they become trout.
Research seems to suggest that the majority of these Sea Trout are female, it makes sense evolutionarily speaking for the species to send the females off to grow big on the fat of the ocean - as bigger fish beget more eggs. Again around about 1,700 eggs for every Kg of body weight. Also, for the most part, the time in their life-cycle when the switch for this anadromous lifestyle is flicked is in the juvenile stages - however, there is some evidence of mature fish when the conditions demand it making the move as well.

This migratory lifestyle is a trade-off between the risk of travel and a higher chance of becoming dinner for some bird, bigger fish, seal, or otter, the energy cost of the migration and the smoltification against the benefit of surviving to get bigger and to produce more eggs and therefore fish in the river.

Of course just like Salmon when Sea Trout make the journey to the ocean they face many of the same challenges and undergo many of the same internal and external alterations to prepare for a life in a very different habitat. In fact it takes a knowledgeable and discernible fish twitcher to tell Salmon and Sea trout smolts apart from one another.

 

See this video to have a go yourself.

Details to look out for are…

Where are the Black Spots? Salmon don’t have much spotting below the lateral line - a line of sensory organs that run mid-way along the length of the fish from head to tail. Salmon also have only a few spots on the Gill covers, usually one very clear and defined.

General profile. Salmon have a slightly more streamlined shape and are a little more slender.

Where does the line of the jaw end in relation to the position of the eye? Salmon tend to have a shorter jaw and the line of it doesn’t go past the back of the eye.

Shape of the fins - Salmon have longer thinner pectoral fins and their tail is more deeply forked.

Colour of adipose fin. Sea trout have a red/orange adipose fin - the small fin on the back before the tail.

© Salmon and Sea Trout Parr - by kind permission of the Atlantic Salmon Trust

The timing of Sea Trout spawning is similar to Salmon as well, both species seeking gravel beds with a good flow of cool, oxygenated water in the late autumn- winter months. Although trout select slightly different areas of water flow. It’s worth mentioning that even Brown Trout that live in the river will migrate within the system, fish from lower down the river migrating upstream to find suitable gravel runs for spawning. The amount of time spent in the sea varies significantly some fish returning after only a few months at sea, others spending several years. Most fish in the UK spend one winter at sea and return the year after they leave freshwater, some rivers in the south are known for large multi-year fish. Either way their time in the Sea allows them to put on the sort of bulk and lay down fat reserves that they would not be able to achieve in the river. Sea trout tend to spend more time closer to shore and don’t undergo the big migrations of Salmon.

Brown Trout © Jack Perks
Brown Trout © Jack Perks

When sea trout return to the river, most head for their natal home, although they are a bit more casual than Salmon and will make forays into neighbouring rivers and back to sea again, many more wandering into new areas to spawn. When they do finally commit to the upstream migration they tend to do it mostly by night. Torchlight searches of stretches of the river Teign from April into June will sometimes reveal them, holding up on their journey upstream.
Initially, they are quite distinctive, although their large size might be reminiscent of a Salmon, in fact, they are sometimes referred to as Salmon Trout, although Peal or Peel is more usual. A fresh run fish I bedecked in a silver livery of scales, both the skin and these scales are rich in the reflective crystals of guanine, which is great for camouflage in the twinkling upper levels of the ocean - not so good in the river environment.. so very very quickly they revert to a colour scheme more typical of their fluvial cousins and replace the chain-mail coat of shinning brilliance with one of warm Browns, Yellows, Blacks and Reds, subdued tones to blend with shadows below overhangs and in deeper pools.
After spawning, the kelts have a higher chance of survival, while many do die, others repeat the process and come back again. They’ve been known to do up to 13 times. These old female fish are bigger and produce larger numbers of bigger eggs - making them really important to the rivers total population of trout.

Brown trout (Salmo trutta) © Jack Perks
Brown trout (Salmo trutta) © Jack Perks

Those fish that stay in the river are much smaller but no less beautiful fish. These are the native trout that most would think of. Specialists at lurking, many a shadow cast by a big boulder or Rooty over-hang is home to one of these wiley predators. It’s a shame not more of us see them, as they are one of the rivers stunners. Olive-backed, with flanks marked with a melee of spots some black, brown others bright red and orange - see one in good light in its natural realm and there is almost a sheen of yellow and blue as well. One of the biggest problems of telling the stories of fish is that most of us never get to see them properly, views are at best fleeting and then you are only looking down on them from above, a view from which they are supposed to not be seen from, as for a mature fish this is the angle from which most predators look for them. Even anglers will admit, they lose something of their panache when hooked and viewed in a landing net. Your best bet on the Teign is to stealthily approach shallow water with a smooth surface and from a distance, with binoculars watch them. You might just get a sense of their beautiful colours, patterns and behaviour.

Dead fish don’t go with the flow!

Watching Trout or Salmon hang, almost motionless in the current is one of the more pleasurable moments that can be had on the river bank. They just hold their spot, making short Sallies to the surface, to nab a fly, but save for a little undulation. Ever wondered how they do this? It turns out they are so perfect and hydrodynamically tuned to their habitat, recent studies have found that even a freshly dead fish when carefully placed in the current will not only stay put, but they can move forward!!

It turns out that these fish are so perfectly designed by the evolutionary hand that even in a swift current they can expend next to no energy.  Read more here..

The Minnow

Minnow male looking sharp © Jack Perks
Minnow male looking sharp © Jack Perks

The Minnow (Phoxinus phoxinus) is another almost omnipresent fish, commonly found in nearly all but the very head of the river is the Minnow. Shoals of juveniles and fry are often seen swarming in the warm shallows. The name Minnow to some is just a generic name for any ‘tiddler’ but it is an actual bonafide species and one that is often overlooked. It’s a shame really as they are not only a really important part of the river ecosystem they are rather pretty as well.

They have a dark mottled brown back and a pale silver or yellow belly and a variable amount of black and gold, that gathers as a line along the middle length of their body - giving them a clear striped look from a distance.
They are mini these minnows, never getting much more than 14 cm in length and barely tipping the scales at just 20g in weight.
During spawning which can happen anytime over the summer, they form shoals of each sex - the bachelors meet with the females in the shallows, where they chase and dance before coming together in a frenzy of activity very much like miniature Salmon.
During spawning the males turn up the flash and develop a lovely display of Rainbow colours on their flanks from pinks, reds, golden yellows, greens and blues, this sets off the dark tiger striping and at the same time, they develop white fin bases, gill covers and somewhat less attractive (at least to us humans) bloom of white spotty tubercles all over their heads.
They are omnivorous feeding on anything from algae and plant materials to small invertebrates - anything edible that can fit in their tiny mouths. Part of their attraction to me is their inquisitiveness, they are always exploring new possibilities. Dip your toes in the river on a summers day and they’ll come to you for a nibble.
A healthy population of minnows usually means there is plenty of other life around. Their small size also means they are fair game for many other species - from Otter, Kingfisher and Goosander as well as the Salmon and Trout.

Minnows © Jack perks
Minnows © Jack perks

The Bullhead

The Bullhead (Cottus gobio) also known as the Miller's thumb is another rather easily missed fish, but one that when you get to know it is probably one of the most fascinating in its own right. It is also a sign of a healthy river as it needs high-quality clean water and being a strict carnivore plenty of smaller creatures to feed on whether that is invertebrates such as insects, worms, molluscs or crustaceans even small fish. So seeing a Bullhead is always a reason to be cheerful. Seeing one however is the challenge sometimes, as they are bottom-dwelling fish, they don't even have a swim-bladder (an internal organ used by many fish species to maintain neutral buoyancy in the water column). They tend to frequent the gravelly, stony places within the river bed and here their changeable, variably mottled and patterned body, a tessellation of blacks, browns and yellows, makes them blend in chameleon-like to their backgrounds. The common names refer to their appearance, they seem to be just a big head with fins. With the 'froggy' head taking up over 25% of their body length it is complete with a big mouth and high set bulging eyes on top they do have a lumpy look may be looking a little like a calloused miller's thumb (having never seen a miller let alone his or her thumb I can only speculate on this). Personally, though I think this fish rather characterful and underappreciated.

They don't get very big. Again 10cm or so in length and about 20g in weight but for all their small size they pack in quite a bit to be fascinated about. First-up they are members of the Sculpin family which is primarily a family of fish that live in the sea - think of the Short-spined Sea Scorpion a classic rockpool fish and you can start to see the likeness.

They share many of the same characteristics and lifestyle elements. They are solitary, bottom-dwelling, sculking predators, they prefer to shuffle along, almost creeping on a pair of large, butterfly-like pectoral fins, although they do have a turn of speed on them as well. Along their back they have a double dorsal fin, the first one is used a bit like a flag for display.

Sometimes just staring at the gravel few a few minutes, tuning into the patterns and chaos of colours and texture might reveal one, usually a juvenile. As adults, they are very territorial, living like hermits, hidden away under stones and submerged objects, often for the duration of their lives. Coming out at night to feed. In fact, it is a gentle turning of rocks and the like that will most likely turn one up.

In the spring the males lure a female into their territory and into their fortress by singing. It's not much of a song as using such a word might suggest, more of a deep resonant croak, produced by rubbing the bones of their pectoral girdle together. It may also be used to communicate amongst males their territorial claims. The females also sing but not as loudly and probably only as part of a duet with a male.

They dress for the occasion as well, darkening with their fins, particularly the first dorsal fin which becomes edged with a creamy or white strip. When he has impressed her she lays a clutch of pale yellow-white eggs (up to 400 or so) which are stuck to the underside of his home rock where they are fertilised. The female then leaves and the male begins his vigil. Never straying from the 'nest' he aggressively guards against any predators while fanning the brood and keeping them clean of dirt and debris, until they become free-swimming fry, at this stage, they disperse.

Bullheads are, like the minnow a popular prey item for just about anything that can find them although I would imagine they are a bit of a tough mouthful to swallow.

Bullhead © Jack Perks
Bullhead © Jack Perks

Stone Loach

The Stone loach (Barbatula barbatula) is sometimes called a beardie, or groundling it is another super cryptic finned denizen of the Teign. It's a small, bottom-dwelling, camouflaged fish that adds to its secret nature by only really coming out at night to forage. They grow up to 12 cm long and are skinny whippet like fish in profile. Long and lean with a yellowy-brown ground colour marked with variable amounts of dark scales, that can give them a peppered, speckled appearance.

Their long rounded sectioned body is headed up by a dorsally flattened head - that is used a bit like a shovel to push and thrust into fine sands and gravels and under small rocks for prey. This is aided by a set of 'whiskers' around the mouth. Six in total - four at the front of the mouth and another two at the corners. These barbels are what give them many of their names both common and scientific and are sensory in nature, helping the fish locate invertebrate food at night, under objects and buried in the sediment. The stone loach is another good fish (not that there are many bad ones) to see as they indicate clean, fast-flowing well-oxygenated rivers.

 

European Eel

The European Eel (Anguilla anguilla) is of course another famous long distance migrant but unlike our Salmon and Sea trout it goes in the opposite direction. It spends it's juvenile growing stages within the freshwater catchment and then heads out to sea, across the atlantic to the Sargasso sea where it spawns. This life-cycle is known as Catadromous. The Eel is a pecualiar fish and one that has declined massively throughout its range - once a common and widespread species, very few rivers, ditches or ponds were without this lithe and sinuous predator. Nowadays however they are rarer than even the Salmon that the River Teign Restoration project was built around. Having declined by over 95% since the 1980's they are at risk of extinction. You do occasionally still see them particularly at night slinking around between the rocks looking for prey, if you do, enjoy and savour the moment for it may as well be a Giant Panda you're looking at.

European eel © Jack Perks
European eel © Jack Perks

Eels are pretty distinctive and unlikely to be confused with any other species of fish, other than perhaps the two species of Lamprey, which share the same sort of elongated almost serpentine (snake-like) body form. A reasonable look will soon sort things out, most distinctive are that the lamprey has pores on the sides of the head rather than the gills. The migration story of Eels is even more bizarre and curious than that of the Salmon and Sea trout. They start their life some 3500 miles away from our western shores, well we assume they do - nobody has ever seen an Eel spawn or indeed found a male with testes. The only reason that this theory/myth of the Sargasso sea exists is that the very first planktonic life stages of the Eel have been found here - the odd leaf-shaped, transparent Leptocephali. It's thought that they drift as plankton on the Gulf stream over a period of two years until they get to the Western European shores where they metamorphose into a more eely form - these Glass Eels start to make their way up to our river systems and as they start to feed in freshwater, they develop pigments and darken, they are now Elvers.

Glass eel © Jack Perks
Glass eel © Jack Perks

These Elvers now move up and disperse themselves throughout the catchment, wriggling up ditches, leats, ponds and on wet nights overland until they find suitable habitat to hole up in and grow. They'll spend up to thirty years in freshwater developing a dark colour on top and a paler, often yellow underside - they are often referred to as Yellow Eels in this stage. They put on quite a bulk and can get to over a metre in length. They tend to become familiar with a place, hiding up by day in deep water, dense vegetation or in holes and under rocks, swimming out to forage at night. At some trigger, they then will head back downstream to make the return journey to spawn.  In the process of readying themselves for the Sea, they become more silver, their mouth becomes smaller and their eyes bigger, they are now called Silver Eels and usually on an autumn full-moon they will slide off unseen by most, back the estuary and out to sea, they've been tracked as far as the Azores making daily migrations from the surface waters to the depths some 1000 metres down and that is all we really know of them, we assume they get to the Sargasso sea as adults, but nobody knows for sure.

European Eel © Jack Perks
European Eel © Jack Perks
European eel © Jack Perks
European eel © Jack Perks
European Eel © Jack Perks
European Eel © Jack Perks

River Lamprey & Brook Lamprey

Brook Lamprey © Jack Perks
Brook Lamprey © Jack Perks

We have at least two of the three British species within the Teign River system. Both the Brook (Lampetra planeri) and the Sea Lamprey (Petromyzon marinus)All lamprey are a weird bunch, very primitive fish, well they're so bizarre and odd they are technically not even fish, as they don't have jaws or, indeed, gills - the latter is replaced by a series of pores down the side of the head. In contrast, instead of jaws, as adults, they have a sucker that looks like something straight out of an alien monster movie in parasitic species. Other non-fishy qualities include a skeleton made of cartilage, no paired fins or scales.

They also have a larval stage. These strange creatures called Ammocoetes are thin, stringy wisps of life spending most of their time hidden away, buried in the fine gravel, silts and sediments here they filter feed or graze on algae.

 

The Brook Lamprey is the most common and the most likely Lamprey species to be encountered on the Teign, although you'd probably have to be a pretty observant and curious person to notice one. They spend most of their life in the larval form. A long stringy alien-looking beast. Looking like a malformed worm with a head. The ammocoetes are blind with a row of seven rounded pores behind the place where each eye should be. They grow to a maximum length of around 15 cm or so and spend five years buried in the sediments where they filter feed. When fully mature they metamorphose into an adult.

The adult has a conspicuous pale staring eye and the same seven gill pores on either side of the head, which gives it its alternative name of 'nine eyes' (sort of - I might not be good at arithmetic, but I still make this eight!). In addition, it has a sucker disk where its mouth should be, but as an adult, it doesn't feed, and its entire digestive system atrophies when it matures. They then have a short period of time in the springtime to spawn in the shallows before they die.

 

The Sea Lamprey is a much bigger and chunkier beast up to 120 cm long. The adults live in the sea where they parasitise larger fish - attaching themselves to their bodies with a mean-looking toothed sucker disk of a mouth. Rasping a wound through which they feed on the tissues and fluids within. They live like this for 1-2 years before migrating into the river system to spawn en-masse in the shallows during the spring, shortly after which they die. Their ammocoetes are very similar to those of the Brook lamprey, the main difference is that they are more heavily pigmented.

Three-spined Stickle back

This is the fish many of us have had some kind of experience of - it is the quarry of many a school girl or boy armed with net and jam jar. Stickleback might be small but they are

Male Three-spined Stickleback © Jack Perks

particularly pugnacious and characterful. They are most common and most likely to be noticed in the still waters of pond, lakes, ditches and flooded quarries. But the slower moving stretches of the River Teign and its catchment do contain them and while they are not often encountered in the main channel of the top half of the river - it's worth mentioning them for completeness.

Stickleback or more accurately Three-spined stickleback ( Gasterosteus aculeatus) never get very large, the adults-only reaching a maximum length of around 11cm. They are easily recognised by their movements and a good view of one with revealing its rapidly sculling pectoral fins (the fins that stick out on either side of the head) and tail fin. They are incredibly manoeuvrable and due to the transparent nature of their fins, almost appear to hover, and just like a hummingbird, they have the ability to almost magically move up and downside to side even backwards and forwards without seeming to move their body.  The three-spined stickleback is not surprisingly, called such because they have three erectable dorsal spines, all that remains of a reduced dorsal fin. These are used in display and when agitated, but they make an already boney and hard to swallow meal even more unpalatable and uncomfortable.

During the Spring between about April and June is their breeding season. The females swell with eggs and look visibly fat while the males become very territorial and at the same time they change colour with their mottled flanks becoming a deep dark Blue or Green, their eyes a bright metallic sky Blue and their bellies flush Crimson. A male stickleback in full breeding garb is a small force of nature.

He will drive off any rival or indeed any species that stumbles into his patch while building a loose nest of plant debris on the bed. When a ripe female fat with eggs enters his domain he sets about wooing her with his shocking attire and a dance - an energetic zig-zagging complete with much fanning of fins and curling of tail. If he's successful he'll entice her into the nest where she'll deposit her eggs. Once they're laid and fertilised he'll send her packing and guard the eggs and the emergent fry from predators and he'll fan them to keep them clean and we'll oxygenated - a more dedicated fishy father you're unlikely to see.

Three-spined stickleback ©Jack Perks