Summaries of reviewed publications references 76 80.

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

Effects

Locations

Reference

REF: 76

Shallow inlets and bays

Sandbanks

Bottom trawling and dredging.

Review paper. Authors suggest that effects of bottom trawling are the marine equivalent of forest clearcutting, acting as a major threat to biological diversity and economic sustainability, and occurring at a rate two orders of magnitude higher than forest loss worldwide. Reasons include reduction in structural complexity of benthic communities, alternation of biogeochemical cycles, and slow recovery after disturbance. The effects can be large and long-lasting on benthic communities as well as young stages of some commercially important fishes although other species benefit when structural complexity is reduced. Recent experimental studies on trawling and dredging impacts on benthic communities are tabulated.

The paper describes the extent and severity of the activity noting that advances in fishing technology have virtually eliminated de facto refuges from trawling, and that frequency of trawling is orders of magnitude higher than other severe seabed disturbances. It calls for the establishment of refuges free of mobile fishing gear, modification of fishing methods and a precautionary approach to management.

 

Watling, L. & Norse, E.A. (1998) Disturbance of the seabed by mobile fishing gear: a comparison to forest clearcutting. Cons.Biol. 12(6):1180-1197.

[PR]

REF: 77

Shallow inlets and bays

Estuaries

Mudflats and sandflats

Reefs

Sandbanks

Seabirds

Various

Review paper describing direct and indirect effects of fishing gears on benthic fauna and habitat, fish community structure and trophic interactions.

Effects on habitats and benthic communities most readily identified and last longest in those areas that experience infrequent natural disturbance. Initial effects can be dramatic, additional effects more difficult to detect. Authors concluded that once an ecosystem enters the fished state, diversity, structure and fish production tend to remain relatively stable across a wide range of fishing intensities. Fishing has accelerated and magnified natural declines in abundance of many forage fishes and this has led to reduced reproductive success and abundance in birds and marine mammals. Dramatic and apparently compensatory shifts in the biomass of different species in many fished ecosystems are considered to often be driven by environmental change rather than indirect effects of fishing. When predator or prey fill a key role, fishing can have dramatic indirect effects on community structure

Authors conclude that many marine ecosystems are overfished and that better management is needed. Population-based management, management which minimises the direct and indirect effects of fishing and the case for marine reserves as an adjunct to other management methods are discussed.

 

Jennings, S. & Kaiser, M.J. (1998) The effects of fishing on marine ecosystems. Adv.Mar.Biol. 34:201-352.

[PR]

REF: 78

Shallow inlets and bays

Sandbanks

Bottom trawling

Report on the results of international research project investigating the effects of different types of fisheries on the North Sea and Irish Sea benthic ecosystem. Provides an overview of the effects of bottom trawling on marine communities with chapters on physical impact, direct mortality due to trawling, scavenger response to trawling, comparison of undisturbed and disturbed areas and long term trends in demersal fish and benthic invertebrates.

Recommendations are made for future studies including approaches to management and fishing methods. For more conclusive evidence on the long-term effects of beam trawling on benthic ecosystem authors call for study of relatively large areas closed to fisheries for many years.

 

Lindeboom, H.J & de Groot, S.J. (Eds) (1998) The effects of different types of fisheries on the North Sea and Irish Sea benthic ecosystems. RIVO-DLO Report C003/98

REF: 79

Shallow inlets and bays

Sandbanks

Suction dredging

Comparative study of dredged and undredged sites to investigate effects of suction dredging on razor clam. Undredged site was characterised by an absence of small razor clams, contained the largest individuals, and a higher density of razor clams. At the dredged site the population had changed considerable in the 7 years of spasmodic dredging. The most notable differences were the absence of a middle size range of clams and a decline in the number of large razor clams. Shells from the dredged site hand considerably more disturbance marks/damage to the outer shell layer than at the control site with 70% showing the highest level ie. Deep clefts in the outer shell layer embedded with sand grains.

Observations of the reburying of razor clams collected by airlift and subsequently released onto the surface of the sediment suggested that they are highly vulnerable to attack from predatory crabs and will experience a high level of mortality after removal.

Orphir Bay and Bay of Ireland, Orkney Islands

Robinson, R.F. & Robinson, C.A. (1998) The direct and indirect effects of suction dredging on a razor clam (Ensis arcuatus) population. ICES J.Mar.Sci 55:970-977.

[PR]

REF: 80

Gill net

Survey of lost gill net over a three year period using submersible. Known ghost net sites at depths between 30m and 127m on a variety of seabed types, surveyed quantitatively by transects. 700m long ghost net on Stellwagen Bank in a boulder field grading to silt-clay substrate was visited on two occasions. Species caught include dogfish, bluefish, lobster, spider crab and edible crab. Hagfish were often seen preying on the dogfish and bluefish. A 470m long ghost net surveyed for two consecutive years had dogfish as the most predominate vertebrate catch. Cancer crabs were the most common invertebrate catch. Codfish were not seen in the ghost gillnet, nor were there identifiable remains of cod at the base of the net.

Gulf of Maine

Cooper, R.A. (1988) Manned submersible and ROV assessment of ghost gillnets on Jeffries and Stellwagen banks, Gulf of Maine. NOAA Undersea Research Programme Research Report 88-4.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Next Section