Summaries of reviewed publications – references 51 – 55.

Details are limited to information relevant to the UK marine habitats and species listed in the Habitats Directive and the Birds Directive.

[pr] indicates that the paper is from a peer reviewed journal or report


Natura 2000 Habitats & Species

Fishing Technique




REF: 51




Fyke nets


Further reports of otter deaths in fyke nets and creels. These include 2 males in fyke nets in the upper Ythan estuary after nets in the river for only 3 days, indicating the speed at which an eel fyke net will operate as an otter trap in a catchment with normally high otter density. Also reports the release of an otter from a fyke net providing an example of otter surviving capture when in shallow water if struggles bring the cod-end to the surface.

Deaths in creels reported from a lobster creel in Scapa Flow, crab creel off Isle of Arran and prawn creel off Skye.

Data confirm the potential of eel fyke to attract and kill otters living at very low density. Also appears to be considerable attraction when silver eels begin their seasonal migration - August/September on East Coast, October/November in Severn. This must be one of the last opportunities for otters to feed on eels in quantity before capture becomes too difficult until spring. Overall monthly distribution of all drownings in fykes, creels and fish traps shows a marked concentration in autumn and winter. Partly explained by seasonality of fishing but also when main food may be reduced for seasonal reasons.

Four otter guard test results shows only a significant difference with the square guard but only approximately 17% reduction. This guard is used by the Danes as mandatory on fyke nets. They have been mandatory in some UK regions since the 1980's.

Crustacean trap problem still unresolved and an issue on the rocky coasts of NW Scotland, the Northern and Western Isles.

Ythan Estuary, Scapa Flow, Isle of Arran and off Skye

Jefferies D.J. (1989). Further records of fyke net and creel deaths in British otters Lutra lutra with a discussion on the use of guards. Journal of the Otter Trust. 1989 p13-19.


REF: 52


Shallow inlets and bays

Beam trawling

Review of data on penetration of depth of ticklers and chain arrays of beam trawls.

Habitat effects - Under normal working conditions beam trawls influence only the top layers of the sea bed up to 30mm on muddy ground and up to 10mm on sandy ground. Summary of results to date suggest average penetration depth 4-7cm. The depth depends on the bottom type and structure of the ticklers and does not always penetrate as the gear moves over the seabed at speeds of 6-7 knots.


Groot S.J. de (1995). On the penetration of the beam trawl into the sea bed. ICES C.M. 1995/B:36

REF: 53



Shallow marine inlets and bays



Trammel nets and gill nets (discarded)

90m long gill net (100mm diameter mesh) and trammel net (100mm with 600mm diameter outer mesh) set by commercial fisherman and cut at one end to simulate net loss. Survey of catches by direct observation, still and video photography for the following 9 months.

Species and community effects - Both nets caught large numbers of elasmobranchs which took about 3 weeks to decompose. Gadoids were eaten within 72hrs therefore not possible to tell how many were caught throughout the observation period and estimates were considered by authors to be conservative. Initially both nets caught more fishes than crustaceans but by 20 days crustacean catch was greater than fishes and was greatest 43 days after initial deployment. Catch per 24hr period declined with time and for fish was nearly zero at 70 days for gill net and 22 days for trammel net. Catch per 24hr for crustaceans remained higher than for fish for both nets throughout the study. Reduction of catch rate probably linked to reduction in net size and degree of entanglement. Overall catch over the 134 day experiment was 261 animals in the gill net and 292 in the trammel net.

Maja squinado and Scyliorhinus canicula were the 2 species most commonly caught in both nets. Other species caught were lobster, brown crab, swimming crab, Nurse hound and Smooth hound. All the crustaceans caught known to scavenge carrion. Other scavengers also aggregated to feed on the animals in the nets included A. rubens, M. glacialis, O. fragilis (in large swarms) and E. esculentus. Three shags were also caught. When nets retrieved (3 months after last survey) 2 spider crabs, previously marked were still alive after more than 102 days in the net. Towards the end of the experiment the free end of the nets began to roll up reducing the total length of net.

Authors conclude that total catch of animals during life of a net may be considerable as in the present study but will depend on local fauna, habitat type and environmental conditions at the site.

St Brides Bay, Southwest Wales

Kaiser M.J., Bullimore B., Newman P., Lock K. & Gilbert S. (1996). Catches in 'ghost fishing’ set nets. Marine Ecology Progress Series. 145: 11-16.


REF: 54

Shallow bays and inlets

Mussel dredging

Experimental work in situ and in laboratory to evaluate the importance of the upwelling of sediment during dredging and, in particular, the amount of sediment particles, nutrients and oxygen consuming substances released during dredging as these factors can effect macrophyte and phytoplankton growth as well as affecting fish and bivalves.

Habitat effects - Preliminary results suggest a minimum flux of 2km2, corresponding to about 0.9cm penetration of the gear. The release of particles, nutrients and oxygen-consuming substances seems to have little effect on the overall environmental conditions in the fjord. Where 10-15 boats dredge for several days, authors note that this will alter the local concentrations of nutrients and suspended matter directly, but the effect would probably only be visible or significant, during the dredging operations. Total annual release of suspended particles shown to be relatively unimportant compared with total annual wind-induced resuspension and release of nutrients compared to load from land.

Species and community effects - the effects are probably much more severe on the ecosystem by changing the bottom flora and fauna which may in turn affect water quality. If natural bottom community cannot be established the areas will be characterised by low biodiversity and by opportunistic species dominated by young individuals of small sizes. Overall environmental effects of this disturbance in Limfjorden is not fully understood.

Limfjorden, Denmark

Dyekjaer S.M. Jensen J.K. & Hoffman E. Mussel dredging and effects on the marine environment. ICES C.M. 1995/E:13 ref.K.

REF: 55


Discards and offal from several fisheries

Data from a study of scavenging seabirds in the North Sea and review of literature on quantities of discards. Fishery waste from North Sea fishery is important to seabirds. The sources evaluated here are demersal trawlers and seiners catching gadoids, pelagic trawlers and seiners, and beam trawlers. Authors estimate quantity available amounts to around 62,800t offal, 262,200t roundfish, 299,300t flatfish, 15,000t elasmobranchs and 149,700t benthic invertebrates per year. Beam trawls have the highest rates of discards of fishing fleets in the area. Discard fraction is dominated by flatfish which are less favoured by seabirds potentially supported by fishery waste in the North Sea estimated to be roughly 5.9 million individuals in an average scavenger community. Discards and offal may easily support all scavenging seabirds in southern and southeastern sub-regions of the North Sea for example but only half in the northwest region.

North Sea

Garthe S, Camphuysen K.C.J. & Furness R.W. (1996). Amounts of discards by commercial fisheries and their significance as food for seabirds in the North sea. Marine Ecology Progress Series. 136:1-11.


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