Northern Ireland's Priority Species

Lophius piscatorius – sea monkfish


Lophius piscatorius Linnaeus, 1758

The sea monkfish, also known as the anglerfish is commonly found in coastal waters all around the UK and Ireland. It is large in size, growing up to a maximum length of 200cm. They are present in waters ranging from 20m down to 550m but can migrate to spawn in waters at a maximum depth of 2000m. An unusual characteristic of the monkfish is how it feeds. It has a single spiny ray on its dorsal fin that it uses like a ‘fishing rod’ to lure in potential prey. Once they get close enough, it engulfs them with its large mouth and rows of inward facing teeth. It attracts a wide variety of prey in this manner, including flatfish, gurnards, rays and eels.

In brief

  • Monkfish are regularly caught by both commercial fishing trawlers and research vessels in Northern Irish waters
  • Its preferred habitat type is sandy or muddy bottoms at depths between 20 and 550m
  • It can be seen throughout the year at fishing ports in Northern Ireland
  • It is a UK priority species categorised as an international threat. It has been included in the UK Biodiversity Action Plan (BAP)
  • The main threat to the UK monkfish population is overfishing. It has a relatively long timescale to reach maturity making it even more vulnerable to overfishing

Species description
The distinguishing features of this species are the flattened body and very broad head. It has large, curved, inward facing rows of teeth on both the upper and lower jaws. It has scale-less skin and the dorsal and anal fins are low and approximately equal in size. It is a brown or brown-green colour on top with a white underside except the hind parts of the pectorals and the anal fin are black. Its mottled pattern gives it good camouflage when lying on the sea bed.

Life cycle
Female monkfish grow larger and reach older ages than males. Maturity occurs at around eight years for females and five years for males. The monkfish migrates to very deep waters to spawn (up to 2000m). Its eggs are laid in sheets which can form large rafts up to 10m long. These sheets will typically contain 1 million eggs. Hatchlings live freely in open water until they are around 8cm long, when they take up life on the sea bed.

Similar species
Its unusual appearance makes it hard to confuse with other species. However, it does have one relative that closely resembles it. Although its distribution is generally more southerly the black-bellied monkfish (lophius budegassa) can sometimes be found further north and is very similar to the monkfish however it cannot grow as large (max length 100cm) and the main distinguishing feature is the darker colour of its underside.

How to see this species
Monkfish are commonly caught by trawlers in the Northern Irish fleet. They can be seen being sold fresh at fishing ports and markets in Northern Ireland.

Current status
Distribution of the monkfish in Northern Ireland is widespread, regularly being caught as by-catch from trawlers. It has not been evaluated by the IUCN and therefore is not protected under its red list. The lack of knowledge and data on numbers of mature monkfish in the seas surrounding the UK makes it very difficult to quantify the current status of the fishery and whether current catch numbers are sustainable.

Why is this species a priority in Northern Ireland?

  • UK priority species list, classed under criteria 1 as an ‘International Threat’

Threats/Causes of decline
The main threat to the monkfish is from overfishing. Its habitat leaves it vulnerable to being caught as by-catch in trawl nets. The majority of individuals landed are below the age of sexual maturity which is worrying given that they haven’t had the chance to breed yet. It leaves the population as a whole vulnerable to exploitation and with a long recovery time if populations were to be depleted.

Conservation of this species

Current action
The EU have put in place a Total Allowed Catch (TAC) of 15 601 tonnes for all of the UK fishing fleet. This number is based on the amount of monkfish that have been landed and discarded by the UK fleet in recent years. This limit stops the population being over exploited and goes some way to helping keep the fishing of this species sustainable.

Proposed objectives/actions
With the monkfish being placed on the UK Biodiversity Action Plan (BAP) list the proposed objectives of this plan are for the UK and EU to implement effective fisheries management, fully incorporating scientific advice and undertake research into factors effecting recruitment levels and population response to climate change.

What you can do
Try to make sure that any monkfish you eat is caught from a sustainable source in order to protect future populations.

Further information


Pictorial - Europe Quotas

ICES status


Fish Base

Ofstad, L., H. & Laurenson, C. (2007). Biology of anglerfish Lophius piscatorius in Faroese waters. ICES CM 2007/K:07.

Naylor, P. (2005). Great British Marine Animals. Cornwall: Deltor. 215.

Laurenson, C., Priede, I.G., Bullough, L.W., Napier, I.R. (2001). Where are the mature anglerfish? – the population biology of lophius piscatorius in northern European waters. The Life History, Dynamics and Exploitation. CM 2001/J:27.

Wheeler, A. (1969). The Fishes of the British Isles and NW Europe. London: Macmillan and Co. 284-285.

Text written by:
Robert Rossell

iNaturalist: Species account : iNaturalist World Species Observations database