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
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Natura 2000 Habitats &
Species
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Fishing Technique
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Effects
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Locations
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Reference
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REF: 21
Shallow marine inlets
Estuaries
(Muddy gravel)
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Clam dredge
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Treatment and control type dredging experiment,
2 passes of a modified oyster dredge.
Habitat effects - Sediment removed
to a depth of between 15-20cm by dredging
and gravel fraction reduced. Sediments may
become more anoxic after dredging. Dredge
tracks most likely to be filled with fine
sediment in low energy conditions therefore
discrete habitat variation will be created.
Resuspended sediment may have serious survival
implications for species unable to deal with
heavy suspended sediment loads.
Species and community effects - Due
to the deep penetration of the dredge all
fauna, with the exception of bivalves (eg
Abra tenuis, Cerastoderma edule and
Mya arenaria) were removed completely
in the short term. It is likely that these
organisms were dislodged and then redeposited
by the dredge or that they migrated or were
passively dispersed into the area from adjacent
undredged areas. Annelids were most badly
affected by the dredge with the exception
of Tubificoides benedeni and a Phyllodocid.
Abundance of bivalves was also greatly reduced
but some found in some dredged samples (small
specimens thought to have been disturbed by
the dredge and re-deposited afterwards).
No clear recovery of fauna evident over the
8 day period of study but opportunistic polychaetes
(eg Capitella capitata and Tubificoides
benedeni) likely to be early colonisers
of disturbed mudflats along with the surviving
bivalves. Authors suggest these will be followed
by active polychaete species eg Eteone
longa and more stable habitat species
such as Cirriformia tentaculata.
Continual disturbance will not favour stable
habitat species, high biomass communities
may occur but are unlikely to contain individuals
of high biomass which may be exploited as
a food source by birds.
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Langstone Harbour
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Southern Science (1992). An experimental
study on the impact of clam dredging on soft
sediment macro invertebrates. Report to English
Nature.
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REF: 22
Shallow bays and inlets
Sandbanks
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Trawling
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Laboratory based experiment investigating
the behaviour of Buccinium undatum
exposed to different prey items.
Species and Community effects - Less
mobile scavengers such as whelks may take
several days to arrive at sites of trawl disturbance.
Whelks are well suited to exploit fisheries
discards as they are very responsive to chemosensory
stimuli exuded from damaged or moribund animals.
98% of whelks caught in a beam trawl survive.
Whelks are capable of exploiting a wide variety
of prey due to their flexible feeding behaviour.
In this experiment they ate Liocarcinus
depurator, Spatangus purpureus, Trisopterus
minutus but not Pleuronectes platessa.
Where whelks are common they have an important
capacity in utilising energy from dead or
damaged animals. Whelks using this competitive
advantage may exhibit local population increases
and in areas of intense beam trawling, such
as the southern North Sea, dead or moribund
animals which result from these activities
could make up a considerable proportion of
the whelk diet.
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Evans P.L. Kaiser M.J. and Hughes R.N. (1996).
Behaviour and energetics of whelks, Buccinium
undatum (L.), feeding on animals killed
by beam trawling. Journal of Experimental
Marine Biology and Ecology. 197: 51-62.
[PR]
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REF: 23
Harbour porpoise
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Record of causes of death in 422 cetaceans
of 12 species stranded on the coasts of England
and Wales between August 1990 and September
1995 via post-mortem examination.
Most frequent cause of death in harbour porpoises
and common dolphins was entanglement in fishing
gear. 38% of harbour porpoises and 80% of
common dolphins diagnosed as being by-caught.
The proportion of by-caught harbour porpoises
increased from 1990 to 1995. Factors such
as changes in fishing effort, technique or
location or changes in the abundance or distribution
of harbour may account for this. Probably
an underestimate of the true incidence of
by-catch in cetaceans. Estimates of the number
of by-caught harbour porpoises cited as being
between 328 and 552 by English fishing fleets
on the Celtic shelf. The proportion of starved
neonatal harbour porpoises higher than starved
common dolphins may relate to the more coastal
distribution of harbour porpoises. More coastal
distribution of harbour porpoises may also
increase their contact with co-factors such
as pollutants making them more likely to die
from species-specific pathogens than common
dolphins. By-catch is a threat to both harbour
porpoises and common dolphins around the coast
of England and Wales. Of 7 Tursiops truncatus
studied only one was determined as being by-caught.
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Kirkwood J.K., Bennett P.M., Jepson P.D.,
Kuiken T., Simpson V.R. & Baker J.R. (1996).
Entanglement and other causes of death in
cetaceans stranded on the coasts of England
and Wales.
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REF: 24
Sand banks
Shallow inlets and bays
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Beam trawling
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Side scan sonar investigation into the effects
of beam trawling in the southern part of the
Danish North Sea.
Habitat effects - Poorly preserved
trawl marks were widely distributed in the
study area except in one area of presumably
coarse grained sediments where there were
numerous extremely well-preserved beam trawl
marks. The substrate appears to have altered
from coarse grained sand or gravel to fine
sand and coarse silt in the trawl marks as
shallow scouring and smoothing from beam trawling
created conditions favouring fine sand/coarse
silt sediment filling the tracks. Effects
of beam trawling on sediment may be long-term
and in some areas may have resulted in a definitive
change of the substrate with implications
for the benthic community.
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Southern North Sea
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Leth J.O. & Kuijpers A. (1996). Effects
on the seabed sediment from beam trawling
in the North Sea. ICES 1996. Annual Science
Conference. Mini-symposium: "Ecosystem Effects
of Fisheries". ICES C.M. 1996/Mini 3.
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REF: 25
Sand banks
Shallow inlets and bays
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Beam trawling
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Experimental investigation into changes in
sediment structure, in- and epifauna, mortality
of by-catch and effects on predators caused
by beam trawling with the application of twice-yearly
fishing perturbations.
Species and community effects - Trawling
causes changes in the abundance of some in-
and epifaunal species. Infaunal diversity
reduced by 54%, epifaunal diversity not significantly
altered. Mortality of animals retained in
the cod-end studied by placing them in tanks.
Results varied greatly between taxa. Mortality
greatest for fish and animals with brittle
skeletal structure such as sea urchins and
swimming crabs, and very low for starfish,
brittlestars and hermit crabs. Benthic species
which are most likely to benefit from the
increased scavenging opportunities brought
about by trawling were starfish and hermit
crabs.
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Red Wharf Bay and Dulas Bay in Liverpool
Bay
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Kaiser M.J., Ramsay K & Spencer B.E.
(1996). Short-term ecological effects of beam
trawl disturbance in the Irish Sea. A review.
ICES C.M. 1996/Mini 5.
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