Bute’s freshwater fish – a checklist

Freshwater Fishes

A checklist of the Freshwater Fishes of Bute


Brown Trout, Loch Quien 13th April 2008 © Norrie Mulholland

Brown Trout, Loch Quien 13th April 2008 © Norrie Mulholland



Fishes comprise a diverse group of some 32,000 species of limbless vertebrates and are found in aquatic habitats around the world, ranging from upland lakes and rivers to deep oceans (Everard 2013). Forty-one species of freshwater fishes are native to Britain and Ireland, and a further twelve species have been introduced. Most fishes, and certainly all of the freshwater fishes of Britain and Ireland, are ‘cold blooded’ (technically known as ‘ectothermic’), their blood temperature varying with the ambient water temperature, which has a significant influence on their seasonal behaviour. All fishes swim using fins and breath largely through gills.

Within the animal kingdom fishes belong to:-

Phylum: Chordata

they are subdivided into three classes:-

Class: Agnatha – jawless fish (c.50 species worldwide)

Class: Chondrichthyes – cartilaginous fish (c.600 species worldwide)

Class: Osteichthyes – bony fish (c.32,000 species worldwide)

Subclass Actinopterygii (Ray finned group)

Subclass Sarcopterygii (Fleshy or lobe finned fish)


All freshwater fishes found on Bute belong to:-

Class: Osteichthyes – bony fish

Subclass Actinopterygii (Ray finned group)

The Island of Bute has many freshwater lochs, including Bull Loch, Greenan Loch, Kirk Dam, Loch Fad, Loch Ascog, Dhu Loch, the waterworks reservoir south of Barone Hill often referred to as ‘Little Dhu’, Loch Quien and Loch na Leighe (Plan Loch). There are no major rivers, but many burns, of which the largest are probably Drumachloy Burn (including Ettrick Burn) and Balnakailly Burn.

In 1976, Jack Gibson and Alex Stephen made the first attempt at cataloguing the freshwater fish occurring on Bute, and since then little further work has been done to record the islands freshwater fishes. Whilst considerably more than one hundred species of marine fishes have been found around the shores of Bute, only thirteen species (including Flounder, which is not a true freshwater species) are known to frequent the island’s freshwater, of which at least four species have been introduced as anglers’ quarry. In addition to Flounder, mullet are also often found around freshwater outlets, although not known to penetrate upstream (A McDonald). All of the species found on Bute are widely distributed in Britain. Salmon and Eel (the British population of which has crashed in recent years) are the only species of conservation concern. Whilst there may appear to be few species of freshwater fish on Bute, there is far greater diversity than on the neighbouring islands of Arran and Great Cumbrae.

Bute’s freshwater fishes, perhaps surprisingly, do not include Minnow Phoxinus phoxinus. Often used as ‘live-bait’ they have escaped from to time to time and there have been old reports of introduction, but none have led to established populations. Sea Lamprey Petromyzon marinus, is often classified as a freshwater species, but on Bute there are only three records, all from the sea, a sight record at Ettrick Bay on 31 May 1985 and one found dead at Kilchattan Bay on 3 September 1988 (Gibson 1990, 2004) and near the mouth of Balnakailly Burn in 2011 (A McDonald). Also, Gibson & Stephen (1976) and Gibson (2004) reported that Common Goby Pomatoschistus microps had been identified from shore pools at Kilchattan Bay, Dunagoil Bay and St Ninian’s Bay and although clearly well distributed around the coast, it has not been recorded from any freshwater sites.

Whilst, in most cases, the species found on Bute have not changed over the years, the population size certainly does, and waters that were dominated by one or two species thirty years ago, may well now be dominated by an entirely different one. Predation, climate change, illegal movement of fish, level of stocking and angling pressure have all altered fish populations of Bute waters in some way. With the advent of heavily stocked waters on the Scottish mainland disease and viruses can rapidly spread and devastate populations. Natural fluctuations occur all of the time: populations of Perch in particular are prone to severe decline then growth, which in turn affects the predators that prey on them. Eels, once common in many waters, have suffered a massive global decline, from which Bute has not escaped. It is our duty to maintain our waters in a healthy state and protect natural populations of fish to the best of our ability (A McDonald).

Freshwater fishing on Bute attracts many anglers from the mainland, with Loch Fad being the principal site. As a result, angling has a significant impact on the island’s economy. Farm fishing began on Loch Fad in the mid-1970s and the well-stocked loch became one of Scotland’s best known trout fisheries, with more than twenty boats available for hire. Loch Ascog, deepened and enlarged during the last century when it became the main water-supply for Bute, is well known for pike and perch fishing. Loch Quien, a shallow, fertile loch holds good numbers of Brown Trout. Greenan Loch has been stocked with Carp, Tench, Bream and Roach.

To ensure the island’s lochs remain prime fishing localities, it is important to be very careful to avoid the inadvertent spread of organisms between waters, which could be achieved by the simple precaution of washing, or disinfecting boots, nets and other equipment. However, in August 2013, the Loch Fad Fisheries was closed until further notice as a result of an outbreak of freshwater lice in the loch.

Freshwater lice are crustaceans, and are the largest external parasite that can infest fish. Although found throughout the world, in Britain there are three main species Argulus filiaceous, Argulus coregoni and Argulus japonicas. The severity of damage caused to an individual fish is determined by the size of the fish and the number of lice attached. However, in addition to the physical injuries and consequent stress to the fish, they also carry the risk of transmitting bacterial infection and viral diseases to the fish. During the summer months, when the louse becomes active as the water temperature rises, it has been detected at several fresh water fisheries across Scotland and often devastates fish stocks. It lays eggs that survive throughout the winter and hatch in the spring, therefore cold winter temperature which may kill adult lice, do not usually impact on the population that hatch the following spring. It remains to be seen to what extent the fish populations of Loch Fad are affected, but meanwhile no further stocking is taking place.

We thank Andrew McDonald, from Bute Angling & Outdoor Centre for providing much of the information on current status and distribution of Bute’s freshwater fish. Paul McTaggart has also provided useful information.

Species Systematic List

Order Isospondyli

Family Salmonidae

Atlantic Salmon Salmo salar

Native to Britain. Adults are fast-swimming predatory fishes, feeding on invertebrates and smaller fish. They take to the sea to feed throughout the adult stage, but return to fresh waters to spawn in their native rivers (Everard 2013).

Gibson & Stephen (1976) said that during the ‘autumn run’ considerable numbers of Salmon ascended for some distance up the Ettrick Burn, where they were occasionally caught by rod fishers, but that no Salmon reach any of the lochs.

Whilst many run-up Loch Riddon, most appear to skirt around Bute on their approach, but it is still found in the lower reaches of Drumachloy/Ettrick Burn and Balnakailly Burn, although not as frequently as Sea Trout (A McDonald).


Trout (Brown Trout/Sea Trout) Salmo trutta

Native to Britain. This is a very adaptable species, including the Sea Trout which has a similar life-cycle to that of Atlantic Salmon. It is a species of clean and cool streams, rivers and lakes, with the Sea Trout also occupying estuaries and coastal seas (Everard 2013).

The New Statistical Account mentioned in 1840 that there were ‘excellent trout’ in Greenan Loch at that time. Gibson & Stephen (1976) wrote that Trout was common in most Bute burns and lochs. They indicated that the non-migratory Brown Trout S. t. fario was fairly common in Greenan Loch, which was evidently stocked with 300 fish in 1969. Loch Quien carried a good stock of Brown Trout, but had been regularly stocked. Gibson & Stephen reported that although in the past Trout had been fairly plentiful in Loch Fad, they had by 1976 become uncommon there. Gibson (2004) reported that in 1992, the Isle of Bute Angling Association reintroduced Brown Trout to Loch Fad, with intermediate stocking since then, resulting in a successful Brown Trout fishery, in addition to the extensive Rainbow Trout population.

Bute Museum displays a cast of a Trout taken in Loch Fad in 1932 which weighed 10¼ lb. Gibson & Stephen believed this was a Bull Trout S. t. lacustris.

Gibson & Stephen (1976) also reported that a third subspecies, the migratory Sea Trout S. t. trutta, which was common in off-shore waters, regularly ascended the Ettrick Burn and occasionally some other burns, but did not reach any of the lochs. In 1969, 1,000 Sea Trout were introduced to Loch Quien by Bute Estate, however, although some were caught, it was believed that most of these escaped to the sea by way of the outlet burn that flows into Scalpsie Bay. It remains a common species around Bute, and is often caught around freshwater outlets, particularly Drumachloy/Ettrick Burn and Balnakailly Burn (A McDonald).

Wild and stocked Brown Trout are present in Loch Quien, some still occur in Bull Loch, Loch Fad and Kirk Dam, but there has been no recent record from Greenan Loch (A McDonald).


Sea Trout, parr, Drumachloy Burn 25th May 2013 © Ron Forrester

Sea Trout, parr, Drumachloy Burn 25th May 2013 © Ron Forrester


Rainbow Trout Oncorhynchus mykiss (Salmo gairdneri)

Introduced to Britain, now naturalised. The Rainbow Trout is indigenous to the west coast of North America, where it inhabits rivers flowing into the Pacific Ocean. In the British Isles, due to frequent introductions, Rainbow Trout are regularly encountered in rivers and large lakes with good quality water, but only some populations are known to breed. It feeds on aquatic and terrestrial invertebrates and small fishes (Everard 2013).

Rainbow Trout has been widely introduced to many waters throughout the west of Scotland. Gibson & Stephen (1976) believed that 300 young Rainbow were introduced to Greenan Loch by the Bute Angling Association in 1969 and 1,000 yearlings to Loch Quien in 1975 by Bute Estate. Rainbow Trout, however, seldom succeeds in establishing itself as a breeding species, therefore in order to maintain a significant population it is necessary to introduce young fish on a regular basis.

Gibson (2004) recorded that a substantial Rainbow Trout cage farm was established on Loch Fad in late 1976, with Loch Fad becoming a highly developed and popular commercial fishery for the angling fraternity. Loch Fad has subsequently been restocked several times each week with Rainbow Trout between 1 lb 4 oz and 12 lb in weight.

Gibson (2004) also reported that Woodend Burn, the main inflowing burn to Loch Fad, had become one of the few places in Scotland where Rainbow Trout have been proved to breed in a natural state.

Rainbow Trout continues to only be found in Loch Fad, and following the louse infestation the ‘fish farm cages’ have been removed. Loch Fad has over the years produced some large specimens up to 42 lb in weight. There are no longer any Rainbow Trout in either Loch Quien or Greenan Loch, although they may still occur in Kirk Dam (A McDonald).


Rainbow Trout, Loch Fad 5th March 2011 © Norrie Mulholland

Rainbow Trout, Loch Fad 5th March 2011 © Norrie Mulholland


Order Haplomi

Family Esocidae

Pike Esox lucius

Native to Britain. It is a large predatory freshwater fish that occurs in standing and flowing waters. Pike prey predominantly upon other fish, and are cannibalistic, but will also take small amphibians, mammals and birds, including ducklings. They have pronounced solitary habits and are usually found in the middle to lower layers of water, generally in association with submerged vegetation and other obstructions in which they lie in wait for prey (Everard 2013).

Gibson & Stephen (1976) said that Pike were very common in Loch Fad and Loch Ascog and that references to the ‘abundance’ of Pike in both Lochs go back to the 1840s. They believed that there were no Pike in any other Bute lochs. Some very large Pike have been caught in Loch Fad, including one that was 29 lb which was ‘killed in the Dam, Loch Fad on 3 March 1927’, a cast of which was in Bute Museum. Gibson (1980) was further able to record that Lord David Stuart caught a pike weighing just over 30 lb in Loch Fad in the early 1940s.

Pike continue to be common in both Loch Fad, and Loch Ascog, although those in Loch Ascog have not attained the weight of specimens caught in Loch Fad. Interestingly Pike in Loch Ascog have a slightly different shape of head (larger) to those in Loch Fad (smaller), presumably having evolved as a result of feeding habits. Pike occur in the Kirk Dam, have fairly recently been introduced to Loch Dhu, and also occur in the ‘Little Dhu’ waterworks reservoir, where surprisingly for such a small water, specimens of up to 20 lb have been recorded (A McDonald).


Pike, jack, Loch Fad 18th May 2006 © Norrie Mulholland

Pike, jack, Loch Fad 18th May 2006 © Norrie Mulholland


Pike, Loch Ascog 17 June 2014 © Norrie Mulholland

Pike, Loch Ascog 17 June 2014 © Norrie Mulholland


Order Ostariophysi

Family Cyprinidae

Common Carp Cyprinus carpio

Introduced to Britain periodically since the 15th century, now widely naturalised. Common Carp is one of the largest and most widespread freshwater fishes found in the British Isles and can live for 40 years. It is a species of still water and larger, slow flowing rivers. Often found on or near the bed of pools and rivers, it will rise to the surface to feed on insects and other floating material (Everard 2013).

Carp was introduced to Greenan Loch in 1992/93 with some additional stocking several years later. This introduction was initially very successful and in 2004 there remained a substantial, self-sustaining population, with several specimens of up to 20 lb being caught (Gibson 2004). However, there was no proof of any breeding taking place and numbers declined. It is several years since the last Carp was caught and the species may now be extinct on Bute (A McDonald).


Tench Tinca tinca

Native to Britain. Tench inhabits densely weeded still waters and river backwaters. It is omnivorous, juveniles feeding extensively on a range of invertebrates and algal matter, while older fish prefer to grub on loch or river beds for molluscs, aquatic insects and crustaceans, and also eat plants (Everard 2013).

Tench was introduced to Greenan Loch in 1992/93, at the same time as Common Carp and Common Bream. They succeeded in establishing an apparently self-sustaining population. However, at Greenan Loch they have only been caught in small numbers, and although they can grow to 15 lb, only fish of a small size have been caught there (Gibson 2004). They continue to occur in Greenan Loch (A McDonald).


Roach Rutilus rutilus

Native to Britain. One of the most widespread species of freshwater fish in Britain, it is found in standing and flowing waters, usually in the middle or lower layers. It is omnivorous, juveniles feeding extensively on small invertebrates and algae, older fish tending towards a more plant and detritus-based diet (Everard 2013).

Gibson & Stephen (1976) said that there were ‘a few Roach in Greenan Loch’. In 1980, Jack Gibson was able to add that Roach was also to be found in Loch Fad and Loch Ascog

Good numbers of Roach are currently found in Greenan Loch and Loch Fad. At Loch Ascog there has been a recent ‘explosion’ in numbers, with fish up to 3 lb in weight. Roach also occur in the Kirk Dam and ‘Little Dhu’ waterworks reservoir, and have been preent in Dhu Loch for the last few years. At Greenan Loch, they are known to hybridise with Bream (A McDonald).


Roach, Loch Ascog 4th August 2013 © Norrie Mulholland

Roach, Loch Ascog 4th August 2013 © Norrie Mulholland


Common Bream Abramis brama

Native to Britain. Common Bream is a shoaling species that is widespread in standing and slow-flowing waters. It has an omnivorous diet, and is particularly well-adapted to grubbing up chironimid (bloodworm) larvae from soft silt. Young fish feed extensively on small invertebrates, whereas older fish tend towards a more varied diet. It commonly occurs in the lower layers of water, feeding on the bed or rivers or lochs (Everard 2013).

Bream was introduced to Greenan Loch in 1992/93, at the same time as Common Carp and Tench. It was still present in 2004, with an apparently self-sustaining population, but, like Tench, the fish were of a small size and only found in small numbers (Gibson 2004).

Bream continue to be present in Greenan Loch where they have been known to hybridise with Roach (A McDonald).


Order Apodes

Family Anguillidae

Eel (European Eel) Anguilla anguilla

Native to Britain. Although some remain at sea, having been bred at sea, most Eels spend the rest of their life in flowing and standing fresh and brackish waters. When mature, males (7-14 years) and females (9-19 years) descend to sea September – December and after five months reach breeding grounds in the Sargasso Sea area of the south-west North Atlantic.  It is a widespread predatory species that feeds on a range of smaller fish and larger invertebrates. Individuals tend to hide away in deeper water and obstructions by day, often burying themselves in soft sediment or inhabiting caves. They become more active at night, hunting at all depths. Eel has declined rapidly over the past few years (around 90% of a decrease since 2000) and although still widespread in Britain, it is now considered to be at high risk of extinction. It has further conservation importance as it is the preferred food for other species of concern, such as Otter and Bittern (Everard 2013, Miller & Loates 1997).

In 1976, Gibson & Stephen reported that Eel was ‘very common in all Bute waters; off-shore, along the streams and burns, and in most lochs’. However, there has been a significant drop in Eel numbers throughout Bute in recent years. Although Loch Fad holds the largest population, it is now comparatively low, whilst the species appears almost extinct on all other waters (A McDonald).


Order Percomorphi

Family Percidae

Perch Perca fluviatilis

Native to Britain. Perch is a striking, boldly marked predatory fish that is found in both standing and flowing water, including the upper, more diluted reaches of estuaries. It is a shoaling species generally found in the middle to lower layers of the water column, often near sunken trees, submerged vegetation and other obstructions, from which it launches predatory raids. The young feed extensively on small invertebrates, whereas older ones consume small fishes and large invertebrates. Shoals of hunting Perch are often the cause of ‘explosions’ of small prey fish at the surface as dusk approaches (Everard 2013).

Gibson & Stephen (1976) referred to the New Statistical Account (1840), which reported the abundance of Perch in Lochs Fad and Ascog. This was still the case in 1976, when there were also ‘a great many’ in Loch Quien, where Lord Bute had introduced trapping in order to ‘keep down the numbers’, and also ‘some’ in Loch Dhu.

Good numbers of Perch still occur in Loch Fad, Kirk Dam and Loch Quien. At Loch Ascog, where some large specimens are to be found, the population occasionally suffers marked declines, but currently good numbers occur. Loch Dhu used to have a very large Perch population, but this has declined in recent years since the introduction of Pike to that water. Perch are also found in ‘Little Dhu’ waterworks reservoir, but, perhaps surprisingly are absent from Greenan Loch (A McDonald).

Perch, Loch Ascog 17 June 2014 © Norrie Mulholland

Perch, Loch Ascog 17 June 2014 © Norrie Mulholland


Order Scleroparei

Family Gasterosteiidae

Three-spined Stickleback Gasterosteus aculeatus

Native to Britain. Three-spined Stickleback is a small but extremely hardy species of still waters, small streams, river edges, ditches and estuaries. It is commonly found in the margins of water bodies, sometimes forming dense shoals. In some rivers, particularly in Scotland, it sometimes migrates downstream into estuaries and coastal waters to overwinter. This is primarily a carnivorous species that feeds on small invertebrates (Everard 2013)

Gibson & Stephen (1976) reported that they had a few records of Three-spined Stickleback from near the mouths of burns, and that many years previous Miss Dorothy Marshall and Dr Sheina Marshall had found some in a burn near Loch Dhu, and also in the vicinity of the Hermitage, between Ascog and Kerrycroy. Gibson (1980) recorded that ‘a good many additional records had come to light’, including from Loch Ascog, and that it had become clear that it was fairly widely distributed on Bute.

It is currently known to be common in Kirk Dam, Loch Quien and Greenan Burn.

Three-spined Stickleback, Greenan Burn 30th November 2013 © Norrie Mulholland

Three-spined Stickleback, Greenan Burn 30th November 2013 © Norrie Mulholland


Ten-spined Stickleback (Nine-spined Stickleback) Pungitius pungitius

Native to Britain. Ten-spined Stickleback is a small fish of still waters, small streams and river edges, where it favours dense vegetation and occasionally forms shoals. Distribution of the Ten-spined Stickleback in Britain is more restricted than that of the Three-spined Stickleback, owing to its preference for well vegetated ponds and streams, together with its intolerance of strongly saline waters (Everard 2013). The number of dorsal spines varies from 7-12, but most have nine or ten spines.

This species was not recorded from Bute by Gibson & Stephen (1976), and there have been no published records until now. On perusing this website in November 2013, Norrie Mulholland realised that he had in fact collected Ten-spined Stiicklebacks in Greenan Burn for Bute Museum’s fish tank on several occasions, but had previously been unaware of the significance. He therefore went back to Greenan Burn and collected one on 30th November 2013 which he photographed. Norrie has collected specimens of Ten-spined Sticklebacks and also Three-spined Sticklebacks between the outlet from Greenan Loch and where the burn runs under the road at the entrance to Greenan Farm. Currently this is the only known locality on Bute for this species.

Ten-spined Stickleback, Greenan Burn 30th November 2013 © Norrie Mulholland

Ten-spined Stickleback, Greenan Burn 30th November 2013 © Norrie Mulholland



Order Heterosomata

Family Bothidae

Flounder Platichthys flesus

Whilst technically not a true freshwater fish, Flounder is a common marine species around Britain’s shores that regularly enters rivers. Typically, it enters the intertidal zone with the incoming tide, and then moves with the rising water up into estuaries, or river mouths, to feed on invertebrates and small fish (Everard 2013).

Gibson & Stephen (1976) recorded that Flounders were common around all suitable parts of the Bute shores, and that they were regularly seen or caught far up some of the burns. It is still present around freshwater outlets (A McDonald).


                                           Fish species occurring in Bute Lochs

Species                                Bull      Greenan  Kirk Dam     Fad        Ascog    Dhu     Quien  na Leighe

Atlantic Salmon

Brown/Sea Trout             Yes                          Yes                 Yes                                     Yes        Yes

Rainbow Trout                                                                        Yes

Pike                                                                     Yes                 Yes         Yes        Yes

Common Carp                                Yes

Tench                                               Yes

Roach                                               Yes            Yes                Yes          Yes

Common Bream                             Yes

Eel                                       Yes        Yes           Yes                Yes          Yes                      Yes         Yes

Perch                                                                  Yes                Yes          Yes        Yes        Yes

Three-spined Stickleback                              Yes                                 Yes        Yes       Yes



We hope to update this website at regular intervals, so please report all unusual or interesting freshwater fish sightings to ron.butemuseum@gmail.com . Observations will be acknowledged. Also we would be pleased to receive any photographs taken on Bute of any fish, which improve upon those currently shown.


Everard, M. 2013. Britain’s Freshwater Fishes. WildGuides Ltd., Old Basing, Hampshire.

Gibson, J.A. & Stephen, A. 1976. The Freshwater Fishes of the Island of Bute. Transactions of the Buteshire Natural History Society 20: 71-75.

Gibson, J.A. 1980. Recent Notes on the Lower Vertebrates of the Island of Bute. Transactions of the Buteshire Natural History Society 21: 97-98.

Gibson, J. A. 1990. The Sea Lamprey on the Island of Bute. Transactions of the Buteshire Natural History Society 23: 59-60.

Gibson, J.A. 2004. Supplementary notes on Bute Vertebrates. Transactions of the Buteshire Natural History Society 26: 99-107.

Miller, P.J. & Loates, M.J. 1997. Collins Pocket Guide: Fish of Britain & Europe. Harper Collins, London.


3.2.16 (RWF)