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The Community of Arran Seabed Trust (COAST) is running a year-long media campaign to raise awareness of the many exciting habitats and species to be found in Arran’s seas, many protected by the South Arran Marine Protected Area.
Each month, they will focus on a particular habitat or collective group of inter-linked species. Their September article features fish and shellfish. There is more information on COAST’s social media or visit www.arrancoast.com
If we are asked what the sea provides for us, most of us probably think of the food that it produces.
This will include fish and shellfish (such as lobsters, crabs, prawns, scallops and mussels) which are some of the more familiar species that we find around Arran and elsewhere around Scotland and the UK.
Fisheries were once seen as a limitless resource, a viewpoint illustrated by the words of the Victorian scientist T H Huxley in his inaugural address to the Fisheries Exhibition in London in 1883: ‘I believe that .… probably all the great sea fisheries are inexhaustible: that is to say that nothing we do seriously affects the number of fish.’
Today we now know that it is all too easy to over-fish wild stocks of marine life with serious consequences for both ourselves and the marine environment.
The community on Arran experienced this directly with the catastrophic decline of commercial fish stocks in the Clyde through the 1980s and its associated loss of livelihoods, income and even island events such as the annual Lamlash Fishing Festival.
Action by COAST and the Arran community to establish the Lamlash Bay No Take Zone (NTZ) and protect the South Arran Marine Protected Area (MPA) from dredging and trawling was a direct response to this loss of fish stocks and marine life.
This hard-won protection is working, as shown by the results of collaborative projects with universities and researchers – increased marine life in parts of the NTZ and MPA, and larger shellfish in the NTZ which produce more eggs.
Studies also show that young cod prefer areas with more seabed marine life.
While we do not yet know whether fish stocks in the Clyde will ever recover, the NTZ and MPA are showing the potential for protected and recovering seabed habitats to contribute to the recovery of commercially important fish, shellfish and other species; increasing numbers of snorkellers and scuba divers want to see this recovery for themselves, bringing additional economic benefit to the island.
Altogether around 500 fish species may occur in UK seas although only around 250-300 of these are likely to be permanent residents; both the largest European fish species, the basking shark, and the second-smallest European fish, the diminutive goby, have been recorded around Arran, the latter seen for the first time this year during citizen science surveys as part of the UK-wide Seasearch project.
Identification of many fish species can prove difficult as they are masters of camouflage meaning you cannot rely on colouration as a method of identification.
Instead a starting point is to look at the variable body shape of different fish species, which adapts them to their particular lifestyle and the environmental conditions in which they live.
Some species living predominantly on the seabed, such as gobies, blennies and sea scorpions, may have quite a short, chunky body, sometimes with a relatively large head (such as with the long and short-spined sea scorpions and angler fish).
Others that live in the water column, such as mackerel, saith and pollack have more torpedo-shaped bodies that enable them to move quickly and efficiently through the water.
Flat fish go through a very unusual and unique anatomical change when they are very small, where the eye on one side of the body moves round so that both eyes are on the upper side of the fish, while the other side becomes the underside in contact with the seabed.
As with fish, we have a wealth of different shellfish in our seas, with some, such as winkles, dogwhelk, shore crabs and hermit crabs, relatively easy to find.
Others, however, can be more cryptic.
Nut crabs, for example, are small crabs with a body that is only the size of a fingernail.
They are generally found amongst gravel and broken shells and so can be hard to spot as they look very similar to the small stones and shell fragments in the areas they inhabit.
Equally cryptic are bivalve shellfish that live within the sediment – often the only sign of these are their filter feeding siphons protruding above the surface of the seabed.
Fish and shellfish have important ecological roles in the marine environment – as described in the article in the Banner in July, fish provide food for larger marine species such as dolphins, porpoise, sea birds and otters.
Through their own feeding activities, both fish and shellfish play an important role in the cycling of nutrients in the sea and influence the structure of marine life communities.
Some shellfish, such as lobsters and crabs scavenge on dead and decaying material as well as feeding on smaller animals and organic particles within the seabed sediment.
Others, such as limpets and winkles, graze on marine plants or, in the case of scallops and other bivalves, feed on small food particles that they extract from the sea water they filter through their bodies.
Fish and shellfish are affected by a range of different human impacts in addition to those associated specifically with fishing, including loss and damage to marine habitats as a result of developments and pollution.
Warming seas as a result of climate change are leading to shifts in the distribution of marine fish in UK waters, meaning some species such as cod are shifting their range further northwards.
Research has found that while juvenile fish of some species are getting bigger as sea temperatures rise, adult fish are getting smaller.
Warming seas can also lead to more frequent and severe harmful marine algal blooms which can be directly harmful to fish and shellfish and increase the risk of marine biotoxins being present in shellfish.
It is in our own interests to look after our seas – evidence shows how fish and shellfish populations can respond when areas are protected and not overfished or degraded.
A well-managed South Arran MPA has significant potential to support sustainable fisheries and other sustainable marine-based businesses into the future.