The Wildlife Trust's North Sea Wildlife Project

Migrating Wildlife

Wildlife found at the coast and out to sea often has strong links to areas found inland at some point within their lifecycle. Below are just a few keys examples highlighting how our inland resources support our marine wildlife.

Lampreys

• Most species are coastal and freshwater
• Some of the phylogenetically oldest fish in the world- very old fossils of them have been found.  They are jawless and have a large sucker covered with teeth, used for hanging on to the sides of fish.  They use their rasping tongue to get at the blood
• They require clean gravel for spawning in rivers, and silt beds for juvenile larvae to burrow into.  
• Present in the Humber throughout the year, swim into smaller rivers eg Ouse to spawn
• Require good water quality at all stages of life- sensitive to pollution.
• Cannot pass barriers like dams and weirs when migrating
• Lamprey ecology is poorly understood
• Lamprey are used as bait by river fishermen-  this is a threat to populations and is discouraged
• Parasitic species that feed on other fish species eg Salmon.  They attach themselves to the flanks of passing fish and feed on their blood
• Three different species- Sea, River and Brook
• Sea lampreys are the largest species found in rivers and can grow to 2.2 kg and as thick as a mans arm.
• A number of areas have been proposed as SAC’s to help conserve the Lamprey.  

Salmon 

• Salmon are anadromous, meaning that they spend most of their lives in saltwater, but return to freshwater to breed.  Salmon do not need saltwater, though, and there are salmon population which spend their whole life in fresh water (‘landlocked’ salmon)
• The amount of time that a juvenile salmon will spend in its natal stream varies from 2-6 years.  Average age correlates with temperature exceeding 7⁰C.
• Salmon can grow up to 1.5m.  During the breeding season, they must swim upstream to spawn, often overcoming obstacles such as waterfalls as they do so.  They have an amazing ability to be able to leap 12 feet in the air.  Salmon always return to the stream that they were born in to spawn, and current theory is that it is due to the particular chemical identity of the water- they find the right stream using their sense of smell. 
• In the last 30 years, the salmon population has experienced a huge decline, and catches have fallen by 80%.  Many populations are on the brink of extinction or have been lost.  It is believed that Atlantic Salmon numbers are only reasonable healthy in four countries- Norway, Iceland, Scotland and Ireland.  In the UK, populations in almost 505 of rivers are at risk, and 30% are endangered.
• Salmon only return to pristine rivers, and so are good indicators of water quality.  The decline of the Atlantic Salmon has been connected to industrial development.  River pollution can severely damage numbers, and the building of dams and changing of the watercourse can make migration impossible. Salmon farming may also be a factor in their decline, as they can spread diseased throughout wild stock, and escaped individuals may erode the gene pool.
• Some conservation measures have been put in place, but populations are not recovering.  Research is going on to find out why this might be.
• The young salmon spend a few days at the mouths of estuaries, getting used to the saltwater, before heading out to sea.
• After spawning, most of the cock fish die.  Some of the hen fish, and only one or two cock fish will survive.  Very few make it back to the sea where the salt water helps them recover.  They do not eat in the freshwater rivers, before or after spawning.  Occasionally, fish will live to spawn two or three times.
• Scientists have created a GM salmon that grows at twice the rate of a normal salmon.  There are very large protests against farming this GM salmon, due to concerns with the genes getting into the environment.