Summaries of reviewed publications – references 56 – 60.

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: 56

Shallow inlets and bays


Beam trawling

Distribution of fishing effort by 25 Dutch commercial beam trawlers analysed and show that in 8 of the most heavily fished rectangles in the North Sea, 10% of surface area trawled less than once in 5 years, 33% less than once in a year. The surface area of the seabed trawled more than 10 times a year estimated at 3%.

Authors note two key parameters to be considered in relation to the impact of beam trawling on benthic fauna; depth of penetration of the beam trawl in relation to sediment type, and spatial distribution of beam trawl effort. They note that the areas of intensive beam trawling have been trawled intensively for several years and still provide profitable fishing grounds and comment that without ample benthic food for plaice and sole, these fishing grounds would have lost their profitability for fishing. However a further comment is that it is not unlikely that the benthic community in intensively trawled areas shifted towards a dominance of highly productive opportunistic species.

Southern North Sea

Rijnsdorp A.D., Buijs A.M., Storbeck F. & Visser (1996). Micro-scale distribution of beam trawl effort in the southern North Sea between 1993 and 1996 in relation to the trawling frequency of the sea bed and the impact on benthic organisms. ICES C.M. 1996/Mini 11.

REF: 57

Shallow inlets and bays


Scallop dredging

Update on studies relating to areas closed to fishing. Two described here. Other studies reported are trawling experiment on the Grand Banks, North Sea Plaice Box, Loch Gareloch (Scotland) and Gullmar Fjord (Sweden).

Comparison of community structure in areas of high and low scallop dredging on northern Georges Bank shows undredged sites had higher densities of shallow burrowing and epibenthic species, more abundant Modiolus modiolus and more abundant small fish. Hard-shelled molluscs were equally abundant at dredged and undredged sites as well as scavenger species suggesting that scavenger abundance was not food limited. No consistent differences in mean size and weight of species between dredged and undredged sites. Many polychaete species were only abundant at the undredged sites because of the complex habitat there. Habitat complexity was higher at the undredged sites due to present of Filograna implexa, bushy bryozoans and hydroids.

Closed area (from 1989) of scallop ground off Port Erin, Isle of Man is being used to assess environmental impact of scallop dredging. Benthic community and physical habitat has been compared with adjacent areas since 1994 and two plots within the closed area experimentally dredged at 2 month intervals. Results to date show differences in the epifaunal communities including greater species consistently more abundant in undredged areas. Further analysis shows this was due to absence of dredging and not variations in sediment or depth. Overall higher densities of shallow burrowing and epibenthic species at the undredged sites but particular species noted for their vulnerability to dredging eg A. digitatum, Anseropoda placenta, Luidia sarsi, Cellaria fistulosa and E. esculentus. There was no evidence of longer-lived benthic species at undredged sites but this was not surprising due to relatively short time since effective closure of the area. Scavenger species were common at both dredged and undredged sites with A. rubens consistently more abundant on the dredged sites. Ratio of polychaetes to molluscs was lower at the dredged sites and may be due to greater habitat complexity in the closed area although authors also note that infaunal bivalves were probably not adequately sampled.

Northern Georges Bank, NW Atlantic

Port Erin, Isle of Man

ICES (1996) Report of the Working Group on Ecosystem effects of fishing activities. ICES C.M. 1996/Assess/ Env:1. Ref: G.


REF: 58

Shallow inlets and bays


Beam trawling

Review of impacts of bottom trawling

Habitat effects - Effect of trawls will be influenced by substrate. Visibility of markings depend on substrate and currents and depth of penetration up to 30mm on muddy ground and 10mm on sandy ground.

Species and community effects - Some groups of animals eg hydrozoans, echinoderms (eg heart urchins) suffer heavy damage by trawling, others escape relatively easily (eg gastropods, hermit crabs).

Author speculates that it is not unlikely that in the long-term a shift in species and numbers may occur as has been found in the German Wadden Sea where polychaetes are on the increase and molluscs and crustaceans in decline but that this is unlikely to have a negative effect on fish stocks. Large quantities of benthic animals become available as food source for fishes. Temporary covering due to sand movement is not exceptional and they will survive, and a shift in species distribution from one group or groups of animals to another cannot be ruled out in the long-term. Author comments that as this shift is, in principle, reversible it constitutes no major threat to benthic life.

North Sea

Groot S.J. de (1984). The Impact of bottom trawling on benthic fauna of the North Sea. Ocean Management 9:177-190.


REF: 59

Grey seal

Common seal

Harbour porpoise

Diving seabirds


Survey into the effects of predator control measures around aquaculture facilities. Grey seals, common seals, cormorants, shag and mink were the most prevalent predators with most of the fish farms surveyed suffering losses to some or all of them. Eider duck and, on some occasions oyster catchers are known to feed on shellfish farms. Predator control measures can be detrimental to all these species which can get tangled and drown in predator nets. Tangling in fish farm nets, mostly top nets and predator nets, was reported from 68% of the 47 sites visited. The animals reported caught were seals, herons, cormorants, shags but also gulls, eider duck, black guillemot, great northern diver, gannet, dolphins (unspecified), harbour porpoise and even a basking shark. Seals, herons, cormorants and shags have also been shot by fish farm operators to protect the stock.

The main impacts of predator control around fish farms are disturbance, displacement and killing both directly and indirectly. More detailed information is needed to assess the significance to local populations but author suggests that it is likely to be acute given the concentration of destructive control measures around individual farms.


Ross A. (1988). Controlling nature’s predators on fish farms. Marine Conservation Society, Ross-on-Wye. 96pp.

REF: 60


General effects of fishing

Life history of 24 species of sturgeon summarised with details of the three different life histories depending on whether the adults remain in fresh water, move into brackish water or finally move into the sea.

Sturgeons are of economic importance as stocks are exploited. Accidental catches in trawls and nets sometimes happen at sea (eg juveniles caught when trawling for clupeid fishes in the Black Sea) but it occurs especially at the mouths of large rivers when fishing for other species. Other impacts, physical obstacles for migrating fish and physical impacts on spawning and nursery areas are also described together with possible mitigating measures. The need to develop techniques for artificially rearing of sturgeon is proposed.


Rochard E., Castlenaud & Lepage M. (1990). Sturgeons (Pisces: Acipenseridae); threats and prospects. Journal of Fish Biology. 37 (Supplement A); 123-132.


Next Section