The Fish

This page is merely a reference section cataloguing the varies species of freshwater fish that you are likely to find in UK rivers together with notes on where in the river you would normally find them.  I have also included details of their life cycles.

 

Atlantic Salmon.

 

Few fish can match the reputation or fighting prowess that the salmon holds within the hearts and minds of UK river anglers.  At certain times of the year salmon leave the sea and head up river to spawn instilling magic and mystery to all who seek to capture them.

Adult salmon enter the rivers with their silvery sea coats but this soon fades once they have been in freshwater for some time.  The cock fish develop a rich blend of reds and browns whilst the hen fish remain dull grey in comparison.  The hen fishes head remains short but the cock fish develops a longer jaw with an upturned lower jaw called a “kype”.

Salmon make their journey towards their spawning grounds in a series of leaps resting in between within known “pools” and it is here that the salmon angler targets them.  Strictly speaking, salmon are not supposed to feed once they enter  freshwater but none the less they do take various flies and lures with shrimp being a favoured bait at certain times of the year.  It is said that salmon take the anglers lures and flies out of sheer annoyance once they are in freshwater and this could well be true seeing that most salmon takes are violent affairs.

Salmon spawn in fast flowing water between October and January in a “redd” made by the female.  Each female produces about 1500 eggs per kilogram of body weight.  After spawning almost all the cock fish die.  A good percentage of the females survive and are called “kelts” after spawning.  Many females also spawn for a second time.  The 6mm orange eggs hatch after about 12 weeks into “alvins”.  These grow on to be fry until they reach around 7cm long when they become parr.  When the salmon parr reach around 13cm and have developed the physiology that will enable them to cope with salt water life they become silver smolts and head off to sea.

UK smolts mostly head off towards the Faeroe Islands, the Norwegian Sea or the west coast of Greenland where they become “grilse”.  Some return back to the UK to spawn after just one winter whilst others remain at sea for two or three years before returning.  The vast majority of salmon do return not only to their native rivers but also the exact tributary where they were born.  This remarkable journey is aided when the salmon swim close to the surface out at sea using the sun, moon and stars, the earth’s magnetic field and prevailing sea currents as navigational aids.  The final entry into their home rivers estuary is guided by “smell” or “taste” of the river.

As salmon parr in fresh water they feed on a range of invertebrates.  At sea salmon feed on a range of fish including capelin, sand eels, herring, sprats and small cod.  They also eat many types of crustaceans including krill.

 

Brown Trout- Sea Trout.

The brown trout (Salmo trutta) live their entire lives in freshwater whilst the sea trout ( Salmo. Trutta morpha truttapends) spends most of its life around the estuaries and coastline of the UK.   Both species are highly prized by anglers for their fighting ability and the undeniable fact that both are very good to eat!

Brown trout do not run true in colouration whilst their sea counterpart always has a black spotted bright silver colouration.  Adult trout pair and spawn in small shallow streams between late September and December sometimes as late as February.  The 5mm orange eggs are laid in a redd made by the female which are fertilised by the male then covered by the female.  Hatching takes around six to nine weeks when the young go from the alevin to fry stage.  They grow on to become parr until reaching one to three years old when the fish assume adult colouration and move to their appropriate feeding areas.

River forms of brown trout migrate down to deeper water within freshwater rivers whilst trout parr that give rise to sea trout develop their silver colouration and head to sea as sea trout smolts. Unlike salmon sea trout spend most of their lives close to shore or in estuaries where they feed.

Freshwater brown trout eat invertebrates of all kinds and will take lesser fish like minnows etc.  Larger lake forms like the ferox eat lesser fish of all types whilst the sea trout eat shrimps, prawns, crabs and fish.

 

 

 

 

Bitterling. 

The bitterling is a very small fish and perhaps one of our lesser known species.  During the breeding season the males become much brighter than the females whilst the female develops a long egg depositing tube or “ovipositor” as its correctly known which extends from her vent about 6cm long which is equivalent to her body length.  The sole purpose of this tube is for depositing eggs into freshwater mussels.

Spawning begins in April or May by the presence of freshwater mussels and its the sight of these mussels that actually triggers reproduction.  The male selects a particular mussel which becomes the centre of its territory and he defends it vigorously whilst keeping a look out for passing females.  Eventually one is found that is ready to mate and they court around the selected mussel.  Eventually the females ovipositor stiffens and she inserts it into the gaping mantle cavity of the mussel where she lays about 25 eggs that stick to the mussels gill.  The male bitterling then sheds milt containing sperm at the entrance of the mussels breathing tube and the mussels inadvertently sucks in the sperm to fertilise the eggs.  The eggs hatch after three or four weeks when the 10mm long bitterling fry swim away from the mussel.  The relationship between the bitterling and mussel is not a one sided affair however because the bitterling breeding season coincides with the mussel spawning season as well.  Mussel larvae attach themselves to the mating bitterling skin and gills who swim away to eventually disperse the mussel larvae when it falls off thus helping to spread the mussel population.

Bitterling browse upon microscopic algae on boulders and silkweed.  They also eat invertebrates and other aquatic insects.  When the water temperature falls below 8c in the winter they withdraw to deep weedy water and go into suspended animation.

 

Barbel.

Barbel are perhaps one of our rivers hardest fighting fish and for this reason have become a very sought after species by UK river anglers.  Even in the smaller sizes of the species its fighting ability is legendary being built for speed and power with its slender body and powerful tail.

Barbel begin the migration to their spawning grounds when the water temperature reaches 15c.  Favoured spawning sites are always in the faster stretches over clean gravel in 30-50cm of water.  Depending on the river and population of barbel present thousands of barbel can congregate at spawning time.  The male fish tend to arrive first and its quite a spectacle to see them lie in the fast shallow water shoulder to shoulder.  When the females arrive and the water reaches 15c the spawning spectacle begins.  The female will be chased around by several males until she shudders and lays her eggs on the gravel which are then fertilised by several males.  The 2mm eggs are very sticky so adhere to the gravel and usually hatch after 10-15 days.  The larval barbel stay in the gravel for two or three  days living on their yolk sacks after which they form shoals moving to slacker water where they eat tiny particles of food.  Young barbel are speckled in colour similar to a gudgeon but they grow very quickly and can weight 1kilo after two years.

Barbel feed almost entirely on invertebrates which are found on the riverbed including freshwater shrimps, water snails, caddis larvae, mayfly nymphs.  They will also seek out midge larvae in more silty areas.  Having said that barbel will also eat pretty much everything that the angler presents to them so they are fairly easy to catch.  Like a lot of fish they like feeding nocturnally so catch rates are always going to be higher for the night fishing angler.

 

Bleak.

 

The bleak is a small fish with a small head and large eyes and apart from sometimes being targeted by anglers as a match winner if vast shoals are present, are not of much interest to river angler generally.

They spawn when the water temperature reaches 15c.  Bleak do not pair, instead large shoals gather then several males will chase ripe females into the shallows  where the females lay upwards to 5000 eggs and several males fertilise them.  The 1.5mm eggs stick to boulders or weed and hatch with seven to ten days.  Initially the larvae feed on their yolk sacks then the fry shoal up feeding on microscopic algae and invertebrates.

Bleak are actually a vital species for river life as many other fish and bird species depend on healthy bleak populations for their own survival.  Fish like perch, pike, chub, zander , brown trout, all hunt bleak shoals whilst birds  like kingfisher, heron, and terns all depend on them as well.

 

Bronze Bream.

Bronze bream are synonymous with UK angling as a match winning species, pleasure angling species or specialist angling species combined.  Although hardly ever regarded as a fighting fish akin to say barbel, it remains a popular anglers choice none the less with virtual angling pilgrimages being centred around the Lochs and rivers in Ireland.  The specimen sized bream are notoriously difficult to catch perhaps more so than most other species.

Spawning begins when the water reaches 12c and takes place in weedy areas of shallow water.  Males develop spawning “tubercles” on their heads and shoulders prior to spawning.  The females lay their eggs in batches over a period of several days at night in weed or over gravel with each female laying anywhere between 80,000-110,000 eggs per kilo of body weight.  The larval bream feed on their yolk sacks then form shoals feeding on algae and planktonic organisms until winter.  Adult bream return to deeper water immediately after spawning.

 

Silver Bream

Skimmer bream, the juvenile size of the bronze bream, is often mistaken by anglers to be silver bream.  Silver bream are never slimy where as the bronze bream always is.  The eye of the silver bream is much larger than that of the bronze variety as well.  Silver bream live in slow weedy rivers and the species is better known for being in lowland lakes, meres, ponds, canals and fenland drains.

Silver bream spawn when the water reaches 14-15c amid a complex splashing display in weedy shallow water.  Most females produce 40,000-50,000 eggs and like their bronze counterparts egg laying takes place in batches over several days.  This practise ensures if there is sudden drought or catastrophe when water levels drop all the eggs are not left high and dry as would be the case if egg laying took place all at once.

Silver bream are omnivorous so will eat water weed as well as invertebrates, molluscs and insects.

 

 

Carp.

 Its introduction to England and Wales started as early as the 1300′s, when carp were imported from mainland Europe and reared in stew ponds. Introduced initially by monks as a food source, carp became established and were stocked into estate lakes and fisheries, and once available, quickly became a target for anglers.  Carp are a long lived fish with some individuals being recorded to live well in excess of 60 years.

Basically there are two types of carp, the common carp and the mirror carp and less so the leather carp (named so because it has no scales on its body).  Strains within the mirror variety include the “linear” because it has a straight row of scales along its linear line.  The “fully scaled” because it has large plate scales all over its body.

Carp spawn when the water temperature reaches 17-18c so spawning is never a successful even year upon year and rarely so in northern Europe.  When the temperature has been reached carp gather in weedy shallows where the female lays her two million 1.5mm eggs over a period of several days.

Larval carp feed on their yolk sacks for two to three days then swim to the surface to take a gulp of air to fill their swim bladders then begin to feed on planktonic organisms including algae and tiny crustaceans.

Adult carp are omnivorous so will eat almost anything.  In angling terms the range of bait that can be employed to catch carp is vast.  (Read the Bait section for detailed information)  Carp are also a shoal species that mainly feed nocturnally.

Carp are great survivors so can thrive in a wide range of watery environments.

 

Wels Catfish.

The wels catfish lives in large, warm lakes and deep, slow-flowing rivers. It prefers to remain in sheltered locations such as holes in the riverbed, sunken trees, etc. It consumes its food in the open water or on the bottom.  The catfish is a voracious predator who when grown large enough will attack most fish it can swallow with water voles, brown rats, ducklings and moor hen chicks appearing on its menu as well.

Catfish will not breed until the water temperature has reached 20c.  The female produces up to 30,000 eggs per kilogram of body weight. The male excavates and guards the nest until the brood hatches, which, depending on water temperature, can take from three to ten days. The male will continue to guard the larval catfish whilst they remain in the redd until they have eaten their yolk sacks and dispersed where they feed on invertebrates close to the bottom.  The young catfish become piscivorous at the end of their first year when they reach 20-25cm.

Specialist anglers target large catfish due to the fishes immense power once hooked so stout tackle is definitely required.  Catfish are solitary feeders that are mostly crepuscular or nocturnal in behaviour.

Crucian Carp

 

For its size, the crucian carp remains a very hardy fish which can stand water conditions that would kill other species.  They are also reputed to be capable of surviving being buried in the mud of a dried up ponds during the summer.

Spawning begins when the water reaches 14-15c with a group of males pursuing a single female in weedy shallow water.  Each female will lay about 250,000 eggs which are fertilised by the males.  Eggs hatch in two to three days with the larval carp feeding on the yolk sacks.  The fry feed on plankton and algae before turning to larger food as they grow.

Unlike other species the crucian carp do not lay their eggs in batches so run the risk of having their eggs left high and dry in times of sudden drought.  For this reason whole year classes of crucians can be missing at some venues.

Although the crucian carp is not held in the same esteem as its larger carp cousins the crucian remains high on the target list for true specimen anglers.

 

Chub.

 

For many years the chub became the mainstay for river angling across the country.  When young, the chub is a fairly easy fish to catch but once they have grown to specimen sizes they switch mode completely to become one of the hardest.  Big chub are very wary so a stealthy approach is vital for success.

In late spring when the water temperature approaches 12c adult chub move from their wintering grounds and head for their spawning sites.  These are in the shallow water over clean gravel very often in marginal shallows and feeder streams.  Chub are communal breeders so several males will join a female once she is ready to lay her eggs.  Each female lays around 40,000-50,000 1mm eggs per kilo of body weight and these stick to the gravel or weed.  The larvae hatch in around 10 days and move into the shallows once their yolk sacks have been eaten.  Here they will eat particles of organic detritus, algae and tiny invertebrates before turning to their adult diet once grown on.

During the summer adult chub often stay around the spawning sites until autumn where after they move back into deeper water to spend the winter.  Although very shy and wary, the chub has an immense dietary range so the angler can employ an extensive choice of bait when targeting them.

In specialist angling terms, six pounds is the bench mark for a much sought after capture.  Stalking chub is especially exciting and there is more on this in the “Methods and Tactics” section.

 

Dace.

Dace populations on certain rivers can be abundant whilst on other rivers their numbers have fallen dramatically.  Many believe the decline is due to slightly polluted rivers becoming less or unpolluted which reduces organic matter and the midge and black fly larvae which the dace feed on.

Dace spawn when the water reaches 12c and gather in shallow fast steamy water below rapids or weirs.  Spawning mostly takes place at night when several males pursue a single female until she is ready to lay her eggs.  Fry feed on microscopic algae and invertebrates but quickly grow on to join the adults by the time autumn arrives.

Unlike many cyprinids dace feed right through the winter so are a favoured species for match anglers to target.  Being a prolific shoal fish dace also form an important part of the rivers echo system as many predators feed on them at all stages of their life.  Birds such as kingfishers, goosanders and common terns take the fry whilst herons and cormorants take the adult fish.  Pike, perch, chub and zander also shadow the dace shoals.

 

Eel.

Eels live a fascinating life and are a migratory species that is born out at sea then comes back to freshwater to feed and grow.  The eel goes through three stages in its life from the larval form, the elver or glass eel stage which arrives in our rivers, the yellow eel stage is the one we all know well with its drab dark olive-brown dorsal surface and yellow sides and belly.  The silver stage is when its diet changes and the snout broadens, it is now fully grown and ready to return to the sea.  The eels back grows darker to near black and the sides and belly become silvery white.  The mouth muscles shrink, the snout becomes more pointed and the eyes grow larger.

At this final stage eels migrate downriver towards the sea when they travel across the ocean to the Sargasso Sea area of the Atlantic to spawn during February and March  at depths as much as 500 m.  All the adults die after spawning.  The 1mm eggs contain droplets of oil which make the eggs float where they drift on the currents until they hatch.  Newly hatched larvae are small at only 7mm long but they grow very quickly feeding on their yolk sacks then microscopic plankton.  As they continue to grow they are carried on the North Atlantic Drift towards Europe a journey that will take around a year.  As they reach the European Continental Shelf the larval stage ( leptocephalus ) have grown to around 75mm then metamorphose into  the elver stage.  The elvers come into brackish water during the spring and early summer with many of the male elvers staying longer in the brackish estuaries to feed whilst the females move on sooner.  Indeed, it is thought the females travel further inland than the males.

Obstacles such as dams, weirs and waterfalls are no barrier for young eels who can use the slightest crack to slither up them.  The eel is also one of the few fish that can survive out of water.  They have large gill chambers that they can keep full of oxygenated water and they can close their gills to prevent their fragile gills from drying out.  Eels can travel snake like over land to reach ponds and lakes that have no connection to a river system.   This overland migration usually takes place at night normally after rain when the ground is wet.

When the eel is fully grown and the time comes to migrate back to sea as a silver eel in autumn, it waits for the river to become high often on a new moon.  On departure, up to 25% of an eels weight is fat, reserved fuel necessary for making the year long journey to the Sargasso Sea.  Read more about fishing for eels in the “Methods and Tactics” section plus the highly important chapter on unhooking eels properly.

 

Grayling.

Grayling were once a persecuted species on game river beats because it was mistakenly thought they competed with salmon parr and wild trout for food.  However studies have concluded there is no competition between graying and trout and that when there is, the brown trout remains the dominant species.

Grasyling spawn in relatively cold water between 5-9c in fast shallow water over fine gravel in rivers. The female cuts a redd and lays her eggs which is fertilised by the males.  Grayling larvae remain in the redd until their yolk sacks are exhausted then move to open water to seek food.  Year classes of grayling can be highly variable in their first year.  Hot summers with low river levels can result in that years production dying whilst heavy loses can also be afflicted on their numbers in autumn and winter if huge floods and spates occur.  Young grayling cannot withstand floods and spates like the adult fish can.

Grayling feed on all forms of invertebrate on the river bed but will also take flies on the river surface.  Trout will  lie “on the fin” just below the surface to take every fly that comes by them where as the grayling will rise off the bottom to take only individual flies each time they rise.   The grayling can be caught in the coldest of weather when no other fish appears to be feeding.

 

Gudgeon.

Young anglers learn to catch fish by catching gudgeon first perhaps more than any other river species as a single maggot trotted down stream mostly draws in their attention.  It has often been said that if gudgeon grew to the sizes that barbel do they would be the most powerful fish in the river

Gudgeon spawn when the water reaches between 14-15c in very shallow water at night.  Several males  fertilise the eggs which the female lays over sand, gravel or weed.  The female lays her eggs in batches to increase their chance of survival as they are susceptible if water levels fall rapidly or if there is a sudden flood.

Being a small shoal fish the gudgeon forms an important part of the river echo system as many other fish and bird species prey upon them.  Gudgeon populations can be affected by the elimination of organic pollution on some rivers.

 

Brook Lamprey.

The brook lamprey is the only one that does not parasitise other fish or venture out to sea as it lives its entire life in freshwater.  The brook lamprey is the smallest one of its kind in Europe reaching a maximum length of only 10-15cm.

Mating begins when the water reaches 10c and the adult fish emerge from the silt where they have remained buried.  They form spawning knots of up to 16 fish and their initial writhing’s form the shallow nest where the fertilised eggs are laid.  The eggs are then covered but it is uncertain which sex does this then the adult fish die within several days of spawning.  The eggs hatch into “ammocoete larvae” and emerge from their nest to be washed downstream to their silty bottomed nursery areas. Here the ammocoetes will burrow and feed until they mature after several years when they metamorphose into the adult form.  Still staying hidden in silt, under rocks or in weed by day, the adult form does not feed but waits until the spawning season to arrive.

 

 

 

 

Minnow.

At some time during the summer one can expect to see the familiar sight of children fishing out minnows with nets on canes placing their catch in jam jars held by a string handle.  Indeed such a sight is one synonymous with childhood summers spent by the waters edge with their parents.

Spawning occurs in water less deep than their own bodies in early spring or when the water reaches 12c.  The minnow shoals may even travel several miles to get to suitable areas.  Young fry move into the shallowest margins where they feed on tiny particles, algae and tiny zooplankton.

Adult minnows spend the spring and summer in vast shoals and feed on tiny invertebrates.  When a large insect falls onto the river surface several minnows will take hold of the insect and drag it under where the shoal devours it.

Minnows are especially significant to the river habitat.  If minnow populations collapse it could affect the whole aquatic ecosystem as so many other species remain dependent on minnow shoals for food.

 

Millers Thumb.

The Millers Thumb is a particularly ugly little fish one that often has children puzzled the first time they catch one.

Breeding takes place at around 10c when the male finds a suitable hollow beneath a boulder with the male enticing the female in to mate.  She lays her eggs in the hollow and he fertilises them.  The male then guards the hollow ferociously until the larvae hatch around 4 weeks later.  The larvae remain in the hollow with the male still guarding them until the yolk sacks have been eaten when they disperse into the river.

Millers Thumb is one of the main foods for the predatory trout as the trout feeds at night when the millers thumb is most active.  Herons, kingfishers, goosanders, otters and feral mink will all take them.

 

Perch.

 

The wolf pack.  Perch are totally synonymous with rivers and river fishing and now that the species has recovered fully since the 1960′s outbreak of perch disease they are a highly targeted species for the true specialist angler with any fish going over four pounds a fish of a lifetime.

Perch spawn in April and May amongst weeds, jetty piles, fallen tree branches or any underwater snag that it in shallow water.  The males arrive first and as soon as the females arrive several males will rush in to fertilise eggs she lays.  The 2-3mm eggs are laid in “strands” in and around the underwater features but in some years breeding production might be lost if their is a sudden drought that dries up spawning areas.

Larval perch remain attached to the spawning site until their yolk sacks have been eaten normally within three weeks when they disperse to feed on planktonic organisms.  As the fry grow they begin to feed on small invertebrates as they grow but remain attracted to invertebrates even when fully grown.  By and large though adult perch remain attracted to other fish such as sticklebacks, minnows and various fry species.  Big perch will often take prey up to 50% their own size as well.

Big perch will also feed during the night and also throughout the winter.

 

Pike.

Few fish can unlock the primeval urge in the angler to go hunting  like the pike can.  With its reputation for evil malevolence, rows of razor sharp fangs and cold eyes which display its no mercy qualifications the tigress of the river and lake remains at the pinnacle of evolution personified.   Since prehistoric times the pike has waited in the shadows to strike and has hardly changed its deathly lethal technique since then.

Pike move towards their spawning grounds weeks before spawning time begins.  The males often arrive first with the giant females gliding in soon after in very shallow weedy locations.  Pursued by several males one lucky fellow gets to lay by her side “eye to eye” when she releases her eggs and the male fertilises them.  If that male does not shed enough sperm to do the job she will wait whilst another male comes to lay with her and repeat the fertilisation process.  Evolution of this magnificent species has designed the males to be shorter than the much larger females so as to be the right length for making the mating ritual effective.  If they were the same size much of the sperm would be lost whilst the males being shorter ensure all of his sperm covers the eggs.

The 2.5mm yellow-brown eggs are laid as a sticky mass on vegetation and they take 10-15 days to hatch.  The larval pike digests its yolk sack then begins to feed on planktonic food when its mouth develops at 12mm long. At 5cm long it begins to eat tiny fish.  Male pike mature more quickly than females at 2-3 years old whilst the females mature at around 3-5 years.  Pike prey on each other but they have few predators once they are fully grown.  Ospreys will take small pike as they become easy targets for the birds as they lay very close to the surface during the summer months.  Perhaps the biggest predator of large pike is now the otter since its reintroduction.

The pikes major predator was undoubtedly man who used to cull them at every opportunity.  Thankfully with the sterling work of groups like the Pike Anglers Club attitudes have totally changed towards this magnificent fish so they are now regarded as a great asset to most coarse fisheries.

 

Roach.

A lot of seasoned anglers cut their first angling teeth whilst fishing for roach as its probably the first species most begin to fish for exclusively with hemp and tare fishing under a trotted float being a prime example.

Roach breed when the water temperature reaches 10c with the males moving into the spawning areas which are in shallow water over dense water weed.  The females come in soon after and rub their vents over the weed and boulders to make sure the eggs stick then the male fish fertilise them.  The eggs hatch between 4-12 days and the larval roach stay attached to the weed until their yolk sacks have been exhausted when they swim off to feed on planktonic organisms.  Because the eggs are laid in shallow water eggs can be left high and dry so fail to hatch resulting in year classes of fish missing in a population.  Some rivers are experiencing roach population collapses and unsuccessful egg hatching could be part of the reason.

Roach are omnivorous so will eat most invertebrates, insects and certain types of water weed.  They are also a very important shoal prey for pike, chub, zander and perch.  Big roach in excess of two pounds are becoming rarer now days so fish of this size are highly prized by anglers seeking to catch them.

 

Rudd.

Rudd are extremely pretty fish with their bright ruby red fins, shiny golden scales and bright eyes.  Some anglers get confused between rudd and roach but they are very easy to tell apart by looking for the following differences;  If you look at the roach’s dorsal fin it is directly in line with its pelvic fin below.  The dorsal on the rudd is set back further than its pelvic fin below.  The roach has 9-12 scales along its lateral line whilst the rudd has 9-10.  The roach has 9-12 anal fin rays whilst the rudd has 10-13.  Roach have red iris’s whilst the rudds are golden with a red fleck on the upper side.

Spawning is the same as with roach as is their diet as both fish are omnivorous however if roach are present in the same vicinity the roach will outnumber the rudd.

 

 

 

 

Ruffe.

This little drab fish was once in demand by gourmets!  Don’t let its size fool you because its one of the most voracious carnivores in the river.

Ruffe spawn between March and May in shallow water and the eggs hatch after 7-10 days.  The larvae eats its yolk sack then disperse to feed on invertebrates before turning to the adult diet as they grow on.

Because they are voracious predators ruffe eat large numbers of bottom spawning fish eggs which can cause some major problems especially in lakes where the ruffe have been introduced.  One lake in particular experienced a ruffe introduction which resulted in some land-locked “Ice Age relic” fish being put under threat.  In Scotlands Loch Lomond the introduction of ruffe caused concern for the native powan stocks as the ruffe eats a large proportion of powan eggs.  Its a similar story where ruffe have been introduced in lakes containing arctic charr.

 

Three and Nine Spined Stickleback.

 

 

 

 

 

 

 

 

 

Ask any classroom filled with young children to name a local wild fish and the chances are most will say stickleback.  Along with the minnow these fish often appear for a short while in their jam jars when out and about at the waters edge with their nets.

Some  strains of Northern Range three spined stickleback are sea going but these occur mainly in Iceland, Scotland, Scandinavia, and northern Russia.  Most of the nine spined sticklebacks in our range remain in freshwater but some will migrate down to brackish water to breed.

Three Spinned sticklebacks breed from mid March to June in shallow weedy water.  The male builds a nest out of weed that is glued together with secretions from its kidney then guards it and the surrounding area from other males.  A female is enticed into the nest by the male making an intricate zig zag dance at one end of the nest where she lays her eggs which are fertilised by the male.  She will lay her eggs in batches either all in the one nest or will go to another nest.   The male guards the nest fanning  the eggs with his pectoral fins to ensure a constant flow of oxygenated water and they hatch after about 4 weeks.  After hatching the larvae remain in the nest for 6-8 days guarded by the male until they disperse.

Three spined sticklebacks are taken by a range of predators.  Kingfishers in particular have to be careful that they swallow the stickleback head first otherwise the fishes spines would get caught in the birds throat.

The nine spined stickleback often referred to as the “ten spined” because it can also sometimes have ten spines breeds more or less in the same way that the three spined stickleback does but is not as common as the three.  The nine also does not tolerate other fish so is often found in shallow water of 10cm or less where oxygen levels are too low for other fish to survive.

 

 

 

 

 

 

 

Stone Loach.

Stone Loach have a long breeding season that lasts from April right through summer till August.  The female chooses a position where she will deposit her eggs in a depression or hollow beneath a boulder or in weeds where she lays her eggs.  These are fertilised by the male then the female guards the vicinity until the eggs hatch in around 2 weeks.  Stone Loach fry develop their barbels after about five weeks when they are 15mm long and they remain in tight shoals throughout the summer in shallow water where other aquatic predators rarely venture.  Once one batch of eggs has developed the female will lay another so that over a complete breeding season she will have laid around 10,000 eggs.

Stone Loaches are a favourite food of kingfishers and herons with aquatic fish such as trout, chub, perch, eels and small pike eating them.

Organic pollution which creates low levels of oxygen in the water can be tolerated by some fish but not stone loaches.  As such the species has been lost from some river stretches.  Where the water remains clean there are abundant numbers of stone loach.  Most naturalists use the presence of salmonids as an indicator of clean or polluted waters, but because the stone loach requires even cleaner water than salmon or trout, it is a better indicator of clean unpolluted water.

 

Tench.

Early mists rolling off a river or lake at the break of dawn with tiny bubbles fizzing on the surface as small fish dimple around in the glass like surface paints the picture of any tench fishing trip.

With its sturdy body and powerful tail the tench is built for sport and in a fishing context the species is steeped and revered with angling history.

Spawning is definitely a warm summer affair as a temperature of 19-20c is required in order for them to breed.  Weedy shallows are chosen for breeding where the female lays her eggs on weed with the males coming in to fertilise them.  The female will lay her eggs in batches over several days until she shed almost 150,000 eggs per kilo of body weight.  The 5mm larval tench hatch in 4-8 days staying attached to the weed until their yolk sacks have been absorbed.  They then disperse to begin life feeding on zooplankton within the weed bed.

Adult tench eat a wide range of invertebrates including algae and pondweed and will stand quite warm water going to 30c and more.  If the water goes above that however the tench will switch to feeding exclusively at night.

 

Zander.

 

 

Translocation of zander to the River Great Ouse system occurred in 1960, when mature zander were taken from Woburn to stock ponds of the then Great Ouse River Authority.The fish bred successfully in the ponds and ninety seven individuals from this stock were subsequently released into the Great Ouse Relief Channel at Stowbridge in March 1963 The species subsequently spread throughout the Fenland drain system and the rest as they say is history with zander continuing to colonise other river systems.

Their introduction however was not the dreadful disaster that many predicted back in the day as zander find their level naturally.

Zander breed in April to June in water between 1-3 m deep with adults arriving at suitable sites when the water reaches 12c.  Weedy sites are preferred when several males follow a female until she lays her eggs then a male will move in to fertilise them.  Both parents then guard the eggs until they hatch after 7-10 days.  The larvae feed on their yolk sacks whilst their fins, teeth and mouths develop before swimming away to feed on small crustaceans and insect larvae as fry.  Adult zander will take any fish to eat that is approximately 10% of its own body length.  Although they will feed during the day feeding intensity grows at dawn or dusk when poor light prevails.  Zander have specially adapted eyes for seeing in low light and murky water conditions so the fish will feed hard in high water when the river is coloured as they can see more than their prey can.  Although feeding will slow in extremely low temperatures they will continue to feed throughout the year apart from their short breeding season when feeding ceases.