There are two species of anglerfish or monkfish (Lophius piscatorius & Lophius budegassa) caught in Scottish waters; catches are almost exclusively of the "white bellied" monkfish; L. piscatorius. The "black bellied" monkfish is far less common. Monkfish are one of the most commercially valuable species for Scottish whitefish fishermen, and are of particular economic importance on the west coast.
Monkfish stocks are considered to be continuous across the northern shelf surrounding Scotland and in 2011 contributed to Scottish landings of over 7,629 tonnes worth £26.4 million in 2011. Anglerfish are caught in a variety of mixed fisheries from shallower water nephrops grounds in the North Sea to specialist continental shelf edge fisheries where ground nets are used.
There are two species of anglerfish, in Scottish waters. The less common black-bellied angler, Lophius budegassa, and the 'white' monkfish, Lophius piscatorius. The biology of both species is similar.
Monkfish occur in an unusually wide range of depths, extending from very shallow inshore waters down to at least 1,100 m. Small monkfish can be caught in shallower water over most of the northern North Sea and west-coast grounds, while large fish, the potential spawners, used to be found at all depths but are now scarce in water shallower than 100-150 m.
Spawning takes place mainly during the first six months of the year, mostly in relatively deep water (150-1,000 m). Although monkfish have a long spawning season, each female probably produces only one batch of eggs, unlike many other demersal species. Female monkfish only begin to reach maturity around the age of seven years when they have grown to a length of about 70cm. Many are therefore likely to be caught long before they reach full maturity. Monkfish have an unusual spawning habit involving the release of eggs in a huge ribbon of jelly that floats to the surface and drifts with the currents; there is some evidence that females rise in the water column at this time. A single egg ribbon can be more than 10 metres long and can contain well over 1 million eggs. After hatching, the young monkfish spend three or four months in mid-water, sometimes drifting long distances, before settling on the bottom at a size of 5-12cm.
Monkfish feed mainly on fish, although shellfish and even seabirds are sometimes found in their stomachs. They lie on the seabed and attract prey to within range of their enormous mouths by twitching a 'fishing rod', or lure, that extends from the top of the head, in front of the eyes.
No accepted analytical assessment can be presented for this stock. Recent dedicated anglerfish surveys carried out by Marine Scotland Science in Division IVa and Subarea VI indicate a decline in abundance in 2007- 2009 and stable biomass in recent years. No reference points have been defined for these stocks. Previous reference points are no longer considered to be valid. The available information is insufficient to evaluate exploitation status. Therefore, catches should be reduced. No management objectives are known to ICES.
Landings of anglerfish increased markedly to the mid 1990s but have since decreased partly as a result of restrictive TACs.
ICES continues to advise that the effort in fisheries that catch anglerfish should not be allowed to increase and the fishery must be accompanied by mandatory programmes to collect catch and effort data on both target and by-catch fish. ICES have previously advised a two-stage approach for management of the angler fishery. The first stage was to substantially improve the quality and quantity of data collected on the fishery while maintaining exploitation at its current level. This first stage of data collection was expected to take at least five years, establishing useable time-series of fisheries-dependent and independent data.
TACs are set separately for the North Sea and West Coast components.
At the December 2011 meeting in Brussels, the Council of Ministers of the EU set the Total Allowable Catches for monkfish as follows:
Area IV & VI, EC waters of IIa & Vb 15,844 9,319
& International waters of XII & XIV.
Joint industry science surveys for anglerfish commenced in 2005 and have continued since. Chartered commercial vessels and Marine Scotland Science's research vessel Scotia carry out stratified random surveys across ICES Divisions IVa VIa and VIb. An industry/science steering group advises on survey protocols and net design. In 2006, 2007 and 2009, Ireland also participated in the survey, providing valuable information for the southern parts of VIa. As yet the series is too short to conclude anything on absolute population trends, but the survey is expected to continue for several more years. ICES have approved the use of these surveys as indicators of relative changes in the population of anglerfish: biomass increased in most areas from 2005 to 2008, but decreased in 2009.
Other developments have included the submission of industry diaries and tally book data to Marine Scotland Science and extra onboard observer data has been collected. The tally book programme has now drawn to a close.
Recent scientific genetic studies have shown that there is no evidence of separate stocks between the North Sea, west of Scotland, Kattegat and Skagerrak. Particle tracking studies have indicated interchange of larvae between areas indicating that they come from the same biological stock.