Anglerfish, Celtic Sea and Biscay, Tangle nets
Targeting and behaviour
Anglerfish are targeted using ‘tangle nets’ of large (>200 mm mesh size) in mixed fisheries targeting anglerfish (monkfish), rays, turbot and brill, mostly on the continental shelf, but also in deeper waters down to a maximum of 600 m depth. These nets are set on the seabed with anchors and marker buoys at both ends. They can be several kilometres in length and are set for 24-72 hours; in some deeper waters there are regulations governing soak times to a maximum of 72 hours (EC 227/2013). The catch is simply snared by entanglement in the large, fine meshes.
The main issues concerning static netting for anglerfish are avoiding bycatches of fish and cetaceans and avoiding ‘ghost fishing’ where lost nets continue to fish. In deeper waters Within the EU and NEAFC (www.neafc.org) areas there are sponge and coral habitats identified as vulnerable.
Evidence of bycatch levels
Fish and shellfish
Enever, et al., (2007) report average discards rates for discards in static net fisheries in ICES sub area VII at 22% by weight; however this is an average figure for a number of fisheries using a number of mesh sizes. Tangle nets set for anglerfish are likely to be selective because of their large mesh size, however, most fish discards are likely to be due to low marketability of certain species, management (shortage of quota) or quality reasons. In certain areas, edible crabs are taken as by-catch. It is difficult to remove them whole from the nets so they are often de-clawed and only claws retained.
Demersal static nets can be made highly size selective for their main target species. Loss of quality, which is a cause of discarding, due to excessive soak time (the length of time the gear is in the water) is countered by short soak times; less than 72 hours. De clawing of crustaceans (principally edible crabs) is regulated by EU legislation (850/98) and local bye-laws, to deter targeting crabs using static gears.
In many areas static nets have been found to catch a bycatch of small cetaceans, most frequently harbour porpoise. Although they catches may be infrequent, the important issue is the effect on the cetacean populations.
Because of their wide ranging populations, conservation of small cetaceans is regulated under a series of international agreements. In European waters (excluding the Mediterranean) the ASCOBANS (Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas) agreement is relevant.ASCOBANS has agreed a maximum bycatch limit of 1.7% of the population of harbour porpoises, based on knowledge of their reproduction, and the EU (EC regs 812/2004) has implemented a requirement for the use of ‘pingers‘ in certain European fisheries aimed at fulfilling this requirement. The pingers emit a sound signal which deters the porpoises from being entangled in the gear. There have been a number of experinmental tests (Larsen and Eigaard 2014) which have shown that these deterents are effective. It has taken some time and effort to develop a pinger which is robust enough to use operationally, but this legislation should now be fully implemented in UK fisheries for vessels larger than 12 m. There have been surveys, the SCANS survey (Small Cetaceans of European Atlantic water and the North Sea) of ceatacean populations in European waters in order to monitor their numbers, in 1994, 2004 with one being developed for 2016. No adverse trends have been detected, although there are only two surveys so far, with wide confidence intervals in the estimates of the population numbers.
‘Ghost fishing’ can been defined as the mortality of fish and other species that takes place in lost or abandoned fishing gear, which continue to catch fish and crustaceans as well birds and marine mammals. Because static gears are left in the sea to catch fish for a period, the risk of ghost fishing is higher for these gears.
Static nets represent a very high investment by the fishermen, and therefore there are substantial incentives to avoid losing gear. One of the highest risk factors is the gear becoming entangled in mobile gear (trawlers and dredgers) gear and being towed away. Fishermen adjust their fishing strategy to take this into account, and this takes the form of;
- Good marking of the gear with highly visible buoys (there are EU regulations stipulating minimum requirements)
- Setting gear in areas and at times when mobile gear fisheries are not active; they use vessel tracking devices to track the likely directions of trawlers
- Avoid using gear in times and places where tidal currents are excessive to optimise fishing and avoid the gear being swept away. For this reason static netting activity is reduced during spring tides in some areas
In areas of high wave and tidal action, lost nets are likely to entangle and bundle up, effectively ceasing to fish within a few weeks (Revill & Dunlin, 2003). In deeper waters, or areas less affected by hydrodynamic action, lost gear tends to fish for longer (Sancho, et al., 2003). EU regulations (EC 227/2013) have recently been introduced stipulating measures which vessels should take to avoid losing these types of gears, especially in deep waters on the continental slope. This includes a ban on fishing below in waters below 600 m, and specific measures to control fishing effort and practices, including soak time and the requirement for the vessel to remain in the vicinity of her gear in the depths between 200 and 600 m. Tangle netting is banned in waters below 200 meters in international waters (www.neafc.org). Since it is believed that anglerfish spawn in deep waters below 600 m these measures which control static netting in deep water are likely also to protect the spawning stock of anglerfish.
Enever, R., Revill, a., & Grant, a. (2007). Discarding in the English Channel, Western approaches, Celtic and Irish seas (ICES subarea VII). Fisheries Research, 86(2-3), 143–152. doi:10.1016/j.fishres.2007.05.013
Larsen F. and Eigaard O. R., 2014. Acoustic alarms reduce bycatch of harbour porpoises in Danish North Sea gillnet fisheries. Fisheries Research 153, 108-112
Revill, A. S., & Dunlin, G. (2003). The fishing capacity of gillnets lost on wrecks and on open ground in UK coastal waters. Fisheries Research, 64(2–3), 107–113.
Sancho, G., Puente, E., Bilbao, A., Gomez, E., & Arreg, L. (2003). Catch rates of monkfish (Lophius spp.) by lost tangle nets in the Cantabrian Sea (northern Spain). Fisheries Research, 64(2-3), 129–139.