Lamprey Sp.

Lifecycles

The river Ness is host to all three UK Lamprey species. These are Brook Lamprey (Lampetra planeri), River Lamprey (Lampetra fluviatilis) and the Sea Lamprey (Petromyzon marinus).

Lampreys are primitive, jawless fish, they possess a simple skeleton comprising of cartilage. They have no paired fins and no scales. They are often confused with eel due to their form, however they can be easily distinguished by their sucker, and seven pairs of gill slits.

The Brook lamprey is the smallest and most common. They spawn between March and June depending on water temperature. Each female lays up to 1200 eggs in a shallow redd excavated in a sandy/gravelly bed. After spawning the adults die. Eggs take around three weeks to hatch into larvae or ammocoetes. Ammocoetes filter organic particle from the mud and silt that they live in. Ammocoetes do not posses’ eyes, they do have a light sensitive spot on the top the head.

Once fully transformed, they have fully functional eyes and may reach a length of 25cm.They are relatively slow growing taking up to five years to reach the stage where they transform into adults, this takes place in the Autumn/winter prior to spawning. This transition includes atrophy of the gut so the adults do not feed.

 The River lamprey is larger, adults can reach a length of 50cm. They have a different life history to the brook lamprey. After four or five years in freshwater, the rive lamprey spends on or two years at sea. It is parasitic and feeds on other fish in particularly estuarine fish so it probably remains coastal. Attaching to a salmon or sea trout it not only obtains a food source but also an easy ride into freshwater. Once there it ceases to feed as it reaches sexual maturity. It spawns the following spring. Males and females scoop a hollow or redd into which the female deposits up to 20,000 eggs. He larvae feed on organic material and bacteria found on the river bed and in mud and silt. 

The larger Sea Lamprey has a life history similar to the river lamprey but venture further out to sea and parasitises a wider variety of fish species often causing death. On its return to freshwater, it spawns in gravel shallows. Females can lay up to 200,000 eggs. Sea lampreys are usually mottled dark and light brown and can reach a length of 90cm, it has radiating rows of sharp rasping teeth and one tooth plate.

Sea lamprey redds have been recorded in the mainstem river Ness along with one or two dead individuals. Sea Lamprey have also been recorded on camera.