Summaries of reviewed publications references 66 69.

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: 66

Shallow inlets and bays

Sandbanks

Beam trawling

Experimental beam trawling trials to investigate effects on megafauna immediately after fishing and 6 months later on two seabed types - mobile megaripple structures and stable uniform sediment. Control and fished areas were sampled.

Short term changes (within ca. 24hrs) were recorded in the megafaunal community in stable sediments but not in the mobile sediments. There were decreases in the relatively slow moving megafauna eg Aphrodita aculeata, Macropodia deflexa and Asterias rubens. Some mobile species (eg. Pagurus bernhardus and Ophiura ophiura increased in the trawled area and are known to migrate into areas of fishing disturbance. There were also increases in some relatively sessile species eg. Mya truncata in the trawled areas but not statistically significant. The effects on the megafaunal community were not uniform, even though the fished areas were completely swept by the gear at least once. Six months later, seasonal changes had occurred in both communities and the effects of the trawling disturbance were no longer evident.

No significant change in biomass of hydroids and Alcyonium digitatum recorded immediately after fishing although these organisms were the largest proportion of the biomass of beam trawl catches at the study site. Repeated and more intense trawling effort is likely to have a greater effect on these organisms.

Area off north east coast of Anglesey, Liverpool Bay.

Kaiser et al., (1998) Changes in megafaunal benthic communities in different habitats after trawling disturbance. ICES J.Mar.Sci. 55:353-361.

[PR]

REF: 67

Shallow inlets and bays

Sandbanks

Bottom trawling

Author develops a conceptual model of gear impacts across gradients of habitat complexity and levels of fishing effort. Habitats are grouped into 8 general categories and scored according to their complexity. The conceptual model shows the response of the range of seafloor habitat types to increases in fishing effort scored from 0 to 4. It shows a range of changes in habitat complexity based on the effects of fishing grear and predicts reductions in the complexity provided by bedforms from direct smoothing of gear.

 

Auster, P.J. (1998) A conceptual model of the impacts of fishing gear on the integrity of fish habitats. Cons.Biol. 12(6): 1198-1203.

[PR]

REF: 68

Shallow inlets and bays

Sandbanks

Otter trawling

Comparison of two fishing areas over a three year period, one of restricted fishing with light levels of trawling and the other with high levels of trawling. Results indicate that intensive trawling significantly decreased habitat heterogeneity. All the epifaunal invertebrates counted were less abundant in the heavily trawled area. No differences were found in the number of infaunal crustacean species but there were more polychaete species in the lightly trawled area every year, implying that high levels of trawling can reduce biodiversity. This also suggests that high-intensity trawling favours opportunistic species.

High numbers of ophiuroids and the amphinomid polychaete Chloeia pinnata in the highly trawled area may be because they can pass through net mesh unscathed and then benefit from feeding on those organisms that the net crushes or kills. C.pinnata was also found to be the most common invertebrate in the diet of several commercially important flatfish species in both areas suggesting that certain prey species and commercially important fish may be enhanced by some level of trawling disturbance.

Monterey Bay, USA

Engel, J. & Kvitek, R. (1998) Effects of otter trawling on benthic community in Monterey Bay National Marine Sanctuary. Cons.Biol.12(6):1204-214.

[PR]

REF: 69

Shallow inlets and bays

Sandbanks

Otter trawls

Three year study into the effects of otter trawling on a sandy-bottom ecosystem of the Grand Banks. Sediment samples, acoustic measurements and video surveys undertaken.

Habitat effects Statistical analysis of seven size fractions gave no evidence that trawling had any immediate effect on sediment grain size. Sidescan sonar showed the persistence of door tracks was variable from several months to a year. Acoustic data suggest that repeated trawling did not affect sediment texture but increased surface relief or roughness. Small-scale biogenic sediment structure down to 4.5cm also changed. Video surveys showed clear differences in the appearance of the seabed. After trawling hummocks were removed or less pronounced, organic floc was either absent or less abundant and mottled appearance of the seabed less pronounced. Sediment grain size data suggest that there may be natural inter-annual changes that are more pronounced than those caused by the experimental trawling.

Species effects. Video imagery showed organisms and shell has organised into linear features in the trawled areas. At times high concentrations of Strongylocentrotus pallidus were visible and seemed to be scavenging on dead snow crabs. Biological effects have still to be examined.

Grand Banks

Schwinghamer et al., (1998) Effects of experimental otter trawling on surficial sediment properties of a sandy-bottom ecosystem on the Grand Banks of Newfoundland. Cons.Biol 12(6): 1215-1222.

[PR]

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