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: 71
Shallow inlets and bays
Sandbanks
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Bottom trawling
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Effects of mobile fishing gear at three sites
on a variety of bottom types in the Gulf of
Maine were investigated.
Habitat complexity was reduced by direct
removal of biogenic and sedimentary structures
and the organisms that create structure eg.
reduction of an extensive sponge community
to the occasional small colony on large boulders,
absence of previously widely distributed ascidian,
reduced density of shrimp, dispersal of shell
deposits by mobile gear. Authors discuss how
this reduction in complexity may lead to increased
predation on juveniles of harvested species
and ultimately recruitment to harvestable
stock especially in the northeast USA, where
fish assemblages are part of a system where
predation mortality on postlarval and juvenile
fishes has a major effect on year-class strength.
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Gulf of Maine
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Auster et al., (1996) The impacts
of mobile fishing gear on seafloor habitats
in the Gulf of Maine (northwest Atlantic):
implications for conservation of fish populations.
Reviews in Fish.Sci. 4(2): 185-202.
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REF: 72
Shallow inlets and bays
Sandbanks
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Beam trawling
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Analysis of bycatch of 7 fish and 10 invertebrate
species taken in otter and beam trawls in
an areas north west of the Netherlands which
were registered annually between 1945 and
1983. A fisheries catchability model is developed
using this data. For species with reliable
field data the model results on long-term
trends in abundance were in agreement with
observations eg. considerable decrease in
abundance of Roker and Common skate off Dutch
coast between 1951 and 1960. Model also suggests
that decline of landings of greater weever
in early 1960s often considered to be due
to severe winter and/or introduction of beam
trawlers should also be attributed to effects
of otter trawling. Most differences could
be related to changes in gear and fishing
effort with otter trawlers catching relatively
more fish than invertebrates and beam trawlers
catchability ten times higher than that of
otters for all species considered.
Model estimates suggest that bottom fisheries
had a considerable impact on the abundance
of several bycatch species even before the
Second World War.
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Northwest Netherlands
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Philippart, C. (1996) Long-term impact of
bottom fisheries on several bycatch species
of demersal fish and benthic invertebrates
in the southeastern North Sea. ICES Annual
Science Conference.
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REF: 73
Shallow inlets and bays
Estuaries
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Aquaculture
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Two year study of macrofaunal succession
and sedimentary biogeochemical parameters
of seabed after intensive fish farming discontinued
at 3 sites. All sites had low numbers of taxa
at the beginning of the survey which increased
in the two years but one site remained impoverished.
The increase showed large fluctuations in
one case which the authors attribute to a
secondary input of organic material to the
site which was considered to have set back
recovery by at least 6 months. This points
to the sensitivity of recovering sediments
to additional stress. Improvements in terms
of increased numbers of species and increased
redox potential were recorded together with
decreases in organic carbon, nitrogen and
pore-water ammonia.
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Loch Fyne & Loch Sunart
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Nickell, T.D et al., (1998) The recovery
of the seabed after the cessation of fish
farming: benthos and biogeochemistry. CM 1998/V:1
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REF: 74
Shallow inlets and bays
Sandbanks
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Trawling
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Study of the effects of extensive and repeated
trawl disturbance over 18 months followed
by 18 months recovery in an area which has
been closed to fishing for over 25 years.
Reference and treatment areas sampled.
Habitat effects. The relative differences
in roughness between the treatment and reference
areas increased during the disturbance programme
and declined during the recovery period. The
sediment in both areas was poorly sorted fine
silt and trawling disturbance did not appear
to have any effect on the sediment characteristics
but trenches were left in the sediment by
the trawl doors. Differences in organic carbon
levels were not thought to be ecologically
significant. More than 18 months was required
before the physical characteristics of the
sites became indistinguishable.
Species & community effects. Changes
over time in abundance of individuals occurred
at both sites but a treatment effect was also
observed. Species numbers were greater at
the treatment site after 16 months and remained
so throughout the monitored recovery period.
Numbers of some individuals were also significantly
greater at the treatment site after 10 months
disturbance (eg. Chaetozone setosa
and Caulleriella zetlandica) only returning
to similar numbers after 18 months recovery.
Others declined in density (Scolopolos
armiger and Nephtys cirrosa). There
were no detectable effects on infaunal biomass.
Community effects extended beyond the 18 month
recovery period studied. Such recovery times
suggest that even fishing during a restricted
period of the year may be sufficient to maintain
a community in an altered state.
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Loch Gareloch
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Tuck I.D., et al., (1998) Effects
of physical trawling disturbance in a previously
unfished sheltered Scottish sea loch . Mar.Ecol.Prog.Ser.
162:227-242.
[PR]
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REF: 75
Shallow inlets and bays
Sandbanks
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Water jet dredges
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xperimental dredging in sandy areas swept
by strong tidal flow with a paucity of epifauna
but openings of numerous larger infaunal animals
such as various bivalve species.Tests conducted
using single fishing events rather than repeat
fishing.
Habitat effects. Trenches up to 2m
wide and 0.15 deep at centre were observed.
These started to fill after 5 days and were
no-longer visible after 11 weeks but sediment
in the tracks remained fluidised under a thin
crust of firm sediment. Long term physical
effects are less well understood and may be
exacerbated by repeated fishing of the same
area.
Species and community effects. Immediate
reduction in number of species, individuals
and biomass in fished tracks but measures
of diversity showed no effects. Abundance
of polychaetes reduce and of amphipods increase.
Crab species moved into the region to scavenge
of material disturbed by the dredge. The results
suggest biological effects are only short
term. No effects were recorded after 11 weeks.
Species likely to be damaged (eg.heart urchins
and large bivalves) were rare in the samples
but present in dredge catches where damage
was noted.
Most of the animals in the sediments are
adapted to a mobile environment so other than
being removed or displaced they were not thought
to be greatly affected by the dredging. On
the basis of this work difficult to comment
on areas with more obvious and diverse epifauna.
Authors conclude there is little difference
between the biological impact of water jet
dredges and suction dredging although the
latter may have a greater physical effect
and fish less selectively.
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Western Isles
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Fisheries Research Services (1998) A Study
of the effects of water jet dredging for razor
clams and a stock survey of the target species
in some Western Isles populations. Marine
Laboratory, Aberdeen Report No. 8/98.
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