- 1 About sea fish
- 2 Wolf fish, Catfish Anarhichas lupus
- 3 Basking sharks
- 4 Basking shark tagging project
About sea fish
Scottish waters support a large variety of fish species, partly thanks to the wide variety of habitats and conditions that can be found. Some species live in open water while others are better suited to being near the seabed, either in deep, dark waters or in shallow water near the coast. Sea bed habitats come in great variety too: sand, mud, gravel, pebbles and rocks all attract different species of fish. Other fish thrive where algae, corals, sponges and other marine life have grown on the seabed.
All our fish have important roles to play in the marine environment and rely on healthy and clean seas, but many species are also commercially fished and are extremely valuable to the national and rural economies. SNH provide input to many marine fisheries management initiatives.
Fish species may be categorised by the section of the water column in which they live: demersal or pelagic. Pelagic fish, such as mackerel and herring, swim in the water column near the surface or mid-water, often in large shoals. Demersal species live close to or on the sea bed and include cod, haddock, whiting, monkfish and flatfishes such as plaice and sole.
Dogfish, Pollock and wrasse are a few fish that can be caught from the shores. Sharks, skates and rays (elasmobranchs) are also caught by anglers, often from boats because these species tend to live in deeper water. There is more information on elasmobranchs below.
Sharks, skates and rays – elasmobranchs
This group of fish have skeletons made out of cartilage, but often have well developed jaws. There are many species of shark within Scottish waters, but the largest and probably the most well known is the Basking shark. Skates and rays are a group of fish that have large wing-like fins that allow them to glide through the water effortlessly. The Common Skate is scarce in Scottish waters, but as a UK BAP species there are a number of actions developed to try to help conserve this fish.
Species with important roles
In some ways all species play an important role in the balance of the natural environment by helping to control the populations of their prey, being an important food source for their predators or by performing other functions such as the recycling of nutrients. However, there are some species which have particularly obvious roles. One of the best examples in Scotland is the sandeel, which is a very important food source for many of Scotlands seabirds, particularly the puffin. Sandeel populations previously declined due to commercial fishing pressure but are now considered to be struggling to recover in some areas due to the impact of climate change on their synchrony with plankton blooms.
Small, shallow-water fish
Many fish find homes in rock pools around our rocky shores. If you are lucky you can spot blenny, gobies, butterfish, pipefish and many more. These habitats contain lots of other plants and small animals that such fish feed on, as well as providing a hiding place from larger predators.
Other spectacular fish in our waters include the formidable Wolf fish which has huge teeth it uses to crush food. Scorpion fish are experts at camouflage, blending in to their surroundings with ease. The sunfish is the largest bony fish in the world and is a rare treat to be seen in Scottish waters.
Wolf fish, Catfish Anarhichas lupus
This fearsome-looking fish is not as aggressive as it looks – it will not attack unless provoked, and its fangs are used for gripping and crushing the shells of creatures it eats. With its large, blenny-like head, bulging eyes and thick, tapering eel-like body, an adult wolf fish can grow to around 120cm long and weigh more than 20kg. Its thick grey skin is often wrinkled, and there are often scars on its face from encounters with crabs and other prey.
Where does it live?
A colder-water fish, this species occurs all around Britain, but we only see them regularly in relatively shallow water on the Scottish east coast and in north east England. It is common in Scandinavian fjords and occurs in deeper water down to 450m as far south as the Bay of Biscay.
On rocky seabeds wolf fish use a large crevice or space beneath a boulder as a lair, often occupying a suitable hole for a long time. One wolf fish named George became a well-known attraction for divers at St Abbs for many years, being easily found in the same hole at only 10m. St Abbs is still considered the best place in the UK to see them. Wolf fish also inhabit sediment seabeds, especially if there are scattered rocks for shelter. Young fish may shelter in kelp forests.
How does it live?
A wolf fish’s lair is often easy to spot, surrounded by the remains of its meals – the shells of molluscs, crabs and urchins. As well as its long fangs, the wolf fish has teeth embedded in its palate, helping it to crush hard-shelled prey. The fish spawn in winter, laying clumps of yellow eggs under stones or overhangs, and the male fish guards these for 2 to 3 months until they hatch. During this time the father tries to intimidate potential predators – divers report that he will puff himself up and click his teeth if they approach too close! The larvae drift for some time in deep water at 100-200m before taking up life on the seabed. Wolf fish take 6 to 7 years to reach spawning age, and are thought to live for around 20 years.
Why worry about basking sharks?
Because basking sharks swim at the surface, these magnificent fish are easily harmed, either deliberately or accidentally. Basking sharks were once fished commercially on a small scale around Scotland for their huge livers, which contain oils formerly used in various industries. The peak recorded kill was almost 250 sharks in 1947, but, in response to concerns over dwindling numbers, the basking shark has had full legal protection since 1998 under the Wildlife & Countryside Act 1981 (as amended by the Nature Conservation (Scotland) Act 2004).
Currently, potential threats include bycatch in fishing nets, and disturbance or impact by jet-skis, speedboats and other vessels. The Scottish Wildlife Watching Code provides best guidance for wildlife watching operators, and continued measures to raise awareness of the code and of the location of Scottish hotspots are invaluable in conservation of this extraordinary fish. There is a UK Biodiversity Action Plan for the basking shark, now taken forward by the Scottish Government as part of the Scottish Biodiversity Strategy . Globally, its conservation status is assessed as vulnerable.
How to recognise them
No other marine creature behaves quite like a basking shark, cruising slowly along at the surface. It can be mistaken for two sharks following each other, because the prominent dorsal fin and the top of its tail fin often show above the surface at the same time. When feeding, the rounded tip of its snout may also show above the water, and no other fish has such a huge mouth! The fish are dark slaty grey to black, with paler belly.
Where do they live?
Basking sharks are found in temperate seas across the world. Although spending much time in the open ocean, they are attracted inshore to places with regular, reliable tidal fronts (places where different water masses meet), where the tiny plankton it eats is concentrated. In Scottish waters, basking sharks are seen most commonly off western coasts, and especially around the outer Firth of Clyde. Recent studies funded by SNH, collating data collected by the Wildlife Trusts, have confirmed two other hotspots for basking sharks: in Gunna Sound, between Coll and Tiree, and around the rocky islet of Hyskeir, southwest of Canna. Considerable numbers of sharks have been consistently recorded here up to four times the numbers seen elsewhere in the UK.
The sharks are highly migratory, but long-distance tracking of individuals only began recently, and it is still unknown whether they migrate between lower and higher latitudes or between deep and shallower water. Their livers contain a large proportion of oil typical of deepwater sharks, which may indicate that they spend some time in deep water.
How do they live?
Basking sharks are usually solitary, but occasionally gather in aggregations of 100 or more where feeding is especially rich. In an hour, a feeding basker can filter 1.5 million litres (330,000 gallons) of water through its gills, extracting tiny crustaceans that resemble pink, swimming grains of rice. Sharks in Scottish hotspots can often be seen in large groups, and showing courtship behaviour, though otherwise we know little about their breeding. One captured basking shark gave birth to six live young, 1.5 to 2m long. The fish probably matures late and reproduces slowly, making it particularly vulnerable to overfishing, especially as fisheries catch many more females than males.
Basking shark tagging project
Scottish Natural Heritage and the University of Exeter ?have joined forces in an exciting new tagging project which will help to solve some of the mysteries about?basking shark behaviour.
- How long do basking sharks remain feeding in certain?areas?in Scottish?waters?
- How are?the sharks using these?areas?which are important to them for feeding and potentially breeding?
- Where do basking sharks go after their summer feeding in Scotland’s seas?
- Do the sharks?remain in deeper waters?off Scotland over winter?
These are some of the questions we hope this project will help?to answer. Many of you have contacted us with your own queries about the basking shark tagging project, so we have produced a list of the most frequently asked questions.
We?have?tagged 20 basking sharks in 2012 off Scotland’s west coast and used 2 types of tags. For the first time in Scotland?the?sharks’ movements?are being displayed online in near-to-real time.?Please follow?the link to join us as we monitor the basking sharks’ tracks! Long-term tags will not provide information until Spring next year – with details of?shark movements over the winter.
Scroll down to?watch?a?short video taken during the tagging phase of the project.
What do you call a shark basking in Scottish waters?
We asked you to help us?name the eight sharks which we have been following in near-to-real time and we received more than 200 name suggestions! It wasn’t easy but we eventually named the sharks Elgol, Solas, Cearban, Gill,?Marna, Cailleach, Roy and Fionnlagh. Thanks very much to everyone who sent in suggestions.
You can help the project by returning any detached tags you come across. The tags ?are designed to eventually?detach from the sharks and they can?get washed-up onto the beach. The tags will provide us with a lot of information whilst attached to the sharks but if we can retrieve them after they fall off we can learn even more. If you return a tag you can also claim a reward!
Several tags?have now?detached from their sharks. So please keep an eye open when you are on the shore and let us know if you find a tag like those in the photo on the left.
If you do?find a tag,?please contact the Scottish Natural Heritage Oban Office on 0300 244 9360, or email?- [email protected]