© 2004 by ICES/CIEM International Council for the Exploration of the Sea/Conseil International pour l'Exploration de la Mer
Impact of experimental trawling on the benthic assemblage along the Tuscany coast (north Tyrrhenian Sea, Italy)
Centro Interuniversitario di Biologia Marina ed Ecologia Applicata V.le N. Sauro 4, I-57127 Livorno, Italy
*Correspondence to A. M. De Biasi: tel: +39 586 807287; fax: +39 586 809149. e-mail: a.debiasi{at}cibm.it.
The impact of repeated experimental otter trawling, in the north Tyrrhenian Sea (Mediterranean) was investigated using a spatially replicated sampling design. Macroscopic modifications of the seabed morphology were assessed by sidescan sonar. Alterations of the sediment texture and changes in macrobenthic infauna were assessed using a box-corer. The most obvious modifications of the seabed were trawl tracks caused by the passage of trawl doors through the sediments. Ephemeral but significant changes in the sediment composition were observed. Changes in the benthic assemblage were detected only 48 h after experimental trawling. The clearest changes were detected in the molluscan component. The present study suggests that recovery from trawling may take place within one month.
Keywords: fishing impact, grain size, molluscs, north Tyrrhenian Sea, soft bottoms, trawling
Received 11 October 2003; accepted 30 July 2004.
 |
Introduction |
|---|
 Top Introduction Material and methodsResultsDiscussionReferences |
|---|
In recent years, there has been an increasing awareness of the wide effects of fishing on marine ecosystems (e.g. Jennings and Kaiser, 1998; Hall, 1999; Collie et al., 2000; Kaiser and de Groot, 2000).
In Italy, most of the studies undertaken to assess the impact of fishing have been carried out in the Adriatic Sea, which for its morphological characteristics such as flat sea bottoms has always favoured the development of trawl-fishing. Most studies focused on the northern Adriatic, assess the ecological impacts caused by "rapido" trawl gear (Giovanardi et al., 1998; Pranovi et al., 1998, 2000, 2001; Hall-Spencer et al., 1999). Fewer studies were carried out in the Tyrrhenian Sea where the impact of illegal trawling within 3 miles of the coast with special reference to its effects on seagrass beds was assessed (Ardizzone et al., 2000).
The aim of this study was to investigate the impact of repeated experimental trawl disturbance induced by otter trawling, in the northern Tyrrhenian Sea (Mediterranean). In particular, macroscopic modifications of the seabed morphology, alterations to the sediment texture and changes in macrobenthic infauna were assessed. If trawling had no effects on the seabed, then a trawled area should not be significantly different from adjacent unfished areas.
This study took advantage of the restriction in commercial trawling in the investigated area to zones beyond 3 nautical miles of the Italian coasts according to the EC regulation 1626/94.
|
Material and methods |
|---|
|
TopIntroductionMaterial and methodsResultsDiscussionReferences |
|---|
Study area
The study was carried out in an area off the Tuscany coast in front of S. Vincenzo (northern Tyrrhenian Sea) approximately 2 km long and 1.5 km wide (Figure 1). This area was selected after a preliminary survey performed in the summer 1998 for selecting an area unaffected by previous illegal fishing activities and for calculating the minimum sampling area suitable to investigate the benthic communities (De Biasi, 1999). This pre-survey was carried out in a marine area 5 km long and 2.5 km wide between 15- and 35-m depth. Sidescan sonar and underwater video camera were used to investigate the bottom morphology whereas sediment samples were collected to investigate the benthic communities and sediment grain size. For this survey, an unfished marine area located at 32–34-m depth characterized by mud or muddy sand was selected. In addition, the species/area cumulative curves (calculated using only the box-corer samples collected at the same depth range) suggested that six replicates were adequate to provide an accurate assessment of the species present in the area.
|
Experimental design
The experimental cruise was carried out in October 1998 using the commercial otter trawler "S. Margherita" moored at Piombino harbour. The fishing disturbance was induced by 14 repeated tows each of which lasted for 1 h over a period of 24 h. The trawler used for the experimental fishing was a medium-sized vessel (19.5 m overall length, 30.4 gross tonnage, 270 hp), typically using a bottom-trawl net and mostly exploiting fishing grounds located at shallow depths (<150 m).
The fishing gear had the following principal characteristics: two oval iron doors weighing 250 kg each, headline of 26 m length, footrope of 32 m length provided with 36 leads of 1 kg each, without chains; codend of 7 m length provided with 350 meshes of 40-mm stretched mesh size; towing speed was about 3 knots for each experimental fishing operation.
Survey procedure
Sidescan sonar
The seabed morphology was assessed using a Datasonics TTV-195. The survey was carried out before trawling, immediately after, 24 h after, 48 h after, and one month after. It was towed along parallel way-lines, about 2 km long, from south to north at a speed of 1.8–2 m s–1. The range of the sidescan sonar was set at 100 m either side of the centre of the instrument. The distance between two parallel tracks was 160 m. The emission frequency varied between 185–225 kHz.
Sediments and benthic communities
Samples were collected by box-corer, with a frame made of 20 x 20 x 30-cm stainless steel box (sampling area: 0.04 m2), before and after (immediately after – only for sediment analysis – 24 h, 48 h, one month) the experimental cruise in ten stations: five inside the fished area (hereafter T = treatment) and five in the unfished area (hereafter C = control). Two controls were located landward and three seaward with respect to the fished area (Figure 1). Sediment samples were analysed for their particle size according to the Udden–Wentworth Phi classification. Each sample, after washing in 16% hydrogen peroxide for 24 h, was wet sieved on a 63-µm mesh sieve to sort the fine fraction. The sand fraction was sieved through a stack of geological test-sieves ranging from 0 Phi to +4 Phi. The fine fraction was then analysed by sedigraph.
Six replicates were collected for community investigation. Sediments were sieved on board through 1-mm mesh sieve and then fixed in 10% buffered formalin. Samples dyed with Rose Bengal were sorted in laboratory, macrofaunal species were counted and identified to the lowest possible taxonomic level.
Statistical analysis
Data from the six replicate fishing treatment and control box-corer samples were pooled prior to analysis. The PRIMER statistical software package was used to perform analyses of the community data. The data set comprised a total of 201 taxa, of which 46 occurred only as a single specimen. Since such a large number of species occurred at low abundance, the taxonomic resolution was reduced because these low abundance species could impair ability to detect any subtle effects of fishing disturbance. Furthermore, fishing disturbance is likely to affect closely related taxa in a similar manner.
The reduced data set contained a total of 35 taxa or species. A cluster analysis, using the Bray–Curtis similarity index was performed on fourth root transformed data. The resultant similarity matrix was used to perform non-metric multidimensional scaling (nMDS). The differences between seaward and landward controls before the experimental trawling were tested by the one-way ANOSIM. No significant differences were detected (R = 0.146, p = 0.17), so landward and seaward controls were considered jointly in the other analyses. An a priori one-way ANOSIM-test was then performed to determine any significant differences between the fished and control treatments for each of the time intervals before and after the creation of the fishing disturbance. To establish which taxa contributed most to either the similarity or dissimilarity between groupings of data, the SIMPER routine was carried out. The contribution of each species to the Bray–Curtis similarity was calculated after fourth root transformation and the species ranked in order of their contribution to separating each group. Species frequency distribution for each of the groups of fished and control areas was examined graphically using k-dominance curves. The percentage of the commonest species is plotted in the first rank, then the percentage abundance of the next commonest is added and this combined total plotted in the second rank, and so on so as to obtain a cumulative ranked species abundance curve, i.e. the k-dominance curve (Lambshead et al., 1983). The same analysis was carried out at the family level.
|
Results |
|---|
|
TopIntroductionMaterial and methodsResultsDiscussionReferences |
|---|
Bottom topography
The sidescan sonar records from the survey carried out before trawling indicated that both the treatment and control areas were flat and devoid of any distinct topographic features. The seabed appeared homogeneous, covered in fine sediments without tracks caused by previous fishing activities. Immediately after trawling evidence of a considerable disturbance in the experimental area was detected. The tracks were produced by the passage of trawl doors and ran mainly in a north–south direction concurring with the direction of the experimental trawling. In some cases, the distance between two different tracks corresponded to the distance between the trawl doors. By contrast, the trawlnet did not leave any evident marks suggesting only minor physical impact. Twenty-four hours after disturbance, appreciable modifications were not detected. Forty-eight hours after experimental trawling had ceased, the marks of the sonograms appeared less distinct. One month later, these tracks were almost invisible. No fresh trawl tracks were recorded in the control area.
Sediment particle size
The bottom surficial sediments, both in the treatment and in the control stations were almost cohesive and mostly constituted by silt and can be classified as poorly sorted fine silt.
By contrast (Figure 2) the silt and clay percentage in T and C changed over time, landward controls showed higher percentage of silt than treatments while seaward controls showed lower percentage of silt than treatments, although both these differences are not statistically significant. In addition, these differences did not appear to have any effect upon the capability of detecting the fishing impact. In fact, immediately after trawling in the landward control an increase of the clay percentage with a parallel decrease in silt percentage was observed. Twenty-four hours later the situation was completely recovered.
|
Benthic communities
In all, 10 584 individuals belonging to 201 taxa were collected over the study period. Of these 108 were polychaetes, 32 molluscs, 44 crustaceans, and 10 echinoderms. Less abundant taxa included cnidarians, phoronids, sipunculans, platyhelminthes, nemerteans, and nematodes.
From one-way ANOSIM, no significant differences were detected between T and C (before R = 0.092, p = 0.25; 24 h R = 0.008, p = 0.44; 48 h R = 0.080, p = 0.25; one month R = –0.080, p = 0.6) at any time interval.
After reducing the matrix to the 35 major taxa the analyses were re-run. According to the ANOSIM, no significant differences were detected when comparing the fished and unfished sites prior to (R = –0.028, p = 0.61), 24 h after (R = 0.13, p = 0.17), and one month after (R = 0.028, p = 0.33) the fishing disturbance. However, 48 h after fishing small but significant differences between the fished and unfished sites were detected (R = 0.24, p = 0.008). Maldanidae, Levinsenia gracilis, Praxilella sp., and Euspira macilenta were more abundant at trawled sites, whereas Flabelligeridae, Cossura soyeri, and Brada villosa were more abundant at control sites (Table 1).
|
The ordination plot from the multidimensional scaling (nMDS) is shown in Figure 3, where only the centroids are shown. Station-points which are more similar to one another in their faunal composition occur closer together on the bidimensional plane. Although T and C were separated in the first survey – i.e. before the experimental trawling – they become more distinct once the experimental trawling commenced. The most evident differences were observed 24 and 48 h after the disturbance.
|
Moreover, the communities of both treatment and control sites changed differently over time. The reference point gradually changed during the one month period underlying a temporal gradient affecting the benthic community. On the contrary, the temporal gradient of the treatment was not as linear and clearly distinct as the control.
Different results were obtained taking into account molluscs. While there were no significant differences in the fished and unfished sites prior to (R = –0.016, p = 0.25), 24 h after (R = 0.020, p = 0.39), and one month after (R = –0.074, p = 0.70) the fishing disturbance had occurred, significant differences were found 48 h after trawling (R = 0.436, p = 0.02). Turritellidae, Thyasiridae, and Corbulidae were more abundant at treatment sites whereas Montacutidae and Lucinidae were more abundant at control sites (Table 2). Corbulidae and Turritellidae resulted, respectively, more (p < 0.05) and less (p < 0.01) abundant in T than in C.
|
The k-dominance curves for Mollusca showed essentially no difference between treatment and control (Figure 4). Twenty-four hours after trawling, however, the T curve lay over the C curve, and after 48 h the two curves clearly separated with the T lying over the C one. One month later, the separation was less marked, and the control curve almost resumed its pre-trawling position.
|
|
Discussion |
|---|
|
TopIntroductionMaterial and methodsResultsDiscussionReferences |
|---|
The most evident modifications to the seabed inflicted by trawling appear to be the tracks left in the sediments. These signs are clearly due to the trawl doors' passage that left distinct marks visible in the sidescan sonar records. By contrast, no modifications were observed as a consequence of the passage of the net. However, the absence of macroscopic alterations does not necessarily infer that there has been no impact.
The impact of nets on sediments is probably more subtle, indirect, and difficult to quantify or requires other methodological approaches. The passage may induce sediment re-suspension and re-deposition. The results of the present study appeared consistent with this hypothesis. In fact, although ephemeral some alterations in the sediment size distribution were observed. In the landward controls, the content of silt significantly decreased while the clay content significantly increased. These variations in the texture of the sediment may indicate that trawling re-suspended the fine fraction of the sediments and currents transported them landward, where they settled. The very short temporal and spatial scale over which these changes occurred allowed the exclusion of other external factors that could have affected the investigated area. If any alternative event really had happened, its effects would have been highlighted for all the sampling stations. Actually, such changes in the sediment composition were observed only for a set of samples suggesting that the impact was local.
The difficulties in relating trawling to variations in sediment grain size have been documented already. Tuck et al. (1998), for example, found no significant changes in sediment particle size which suggested that the effects on the grain size are not strong and unambiguous. In addition, contrasting results can be a consequence of different time and spatial scale over which the studies have been carried out. In the present study, significant changes were detected only immediately after trawling and they completely disappeared 24 h later. This means that sediment alterations require studies at very short temporal scale.
Parallel demonstration of impact of trawling on the benthos is not an easy task and a wide range of conclusions, even contradictory, have been reported in the scientific literature (Drabsch et al., 2001). In the present study, only some members of the benthic assemblage appeared to be affected by trawling and the biological effects were as ephemeral as the physical ones in accord with some previous studies (Kenchington et al., 2001). It is noteworthy that in such a short period, i.e. 48 h, a well-defined temporal gradient in the controls was observed. In contrast, this temporal gradient was not apparent for the treatments. The different patterns observed may be due to the experimental trawling that affected the temporal dynamics of the benthic assemblages locally. Thus, control and impacted sites changed differently over time. Unfortunately, a comparison with other authors is difficult because daily studies are not common as they are labour intensive, expensive, and the results can be too local for a large consensus among scientists (De Biasi et al., 2002). In addition, there is a lack of previous similar studies with which to compare this one. Although it is incontestable that otter trawling affects the seafloor environment, the kind and degree of impact is difficult to demonstrate (Messieh et al., 1991) and not necessarily consistent among different localities.
In the present study, the clearest changes were detected in molluscan assemblage. The k-dominance curves indicated a shift to dominance of fewer species in the fished area 48 h after the experimental trawling. Some authors suggested that trawling can directly crush or remove, above all, the near-surface organisms (Gilkinson et al., 1998; Hall-Spencer et al., 1999; Bergman and van Santbrink, 2000). However, these effects cannot be totally responsible for the observed pattern, because they should have been observed even 24 h after trawling. Other processes acting more slowly must be invoked to explain a delayed effect. Specific studies carried out by Morton (1996) in an area subjected to suction dredging and trawling suggested that the impact documented upon the benthic molluscan community was a secondary result related to the sediment plumes. However, the same conditions could be advantageous for other organisms. For example, Thyasiridae and Corbulidae, typically considered opportunistic taxa and indicative of instability of surficial layer of sediment (Picard, 1965; Bellan, 1991), can increase in these disturbed conditions. This result is difficult to interpret. These taxa are relatively restricted in their movements, so the hypothesis that they could have been attracted to carrion from the surroundings is not convincing. Moreover, the observed pattern is not consistent with other authors who, analysing long-term data, described large-size bivalves as sensitive to fishing disturbance (Ball et al., 2000). In addition, these data cannot be compared with those of authors who focused their attention mainly on the physical damage to the infaunal bivalves rather than their short-term behaviour and movements (Rumohr and Krost, 1991; Gilkinson et al., 1998).
The experiment presented here describes short-term changes associated with experimentally induced disturbance. All the features taken into account showed some effects 48 h after the trawl impact followed by a very fast recovery within one month. Even the physical macroscopic impact on the seabed morphology clearly decreased within this interval. Moreover, only slight effects were observed. This result can depend on the type of habitat where the study was performed. In shallow areas, the benthic communities experience continual disturbance at various scales (Hall, 1994) both natural and anthropic forming a background which could confound the effects due to a small-scale induced disturbance (Kaiser and Spencer, 1996).
In addition, these results do not necessarily reflect the chronic impact caused by trawls on a real commercial fishing ground (Thrush et al., 1995; Collie et al., 1997; Kaiser et al., 2000) and a general model can, therefore, not be inferred.
This study examined only the effects of a very small spatial scale disturbance. It cannot be excluded that small-scale and short-term disturbances permit a rapid recolonization from surrounding areas. Such recovery mechanisms cannot be effective under frequent large-scale disturbances as other authors suggested (Thrush et al., 1998). On real fishing grounds, wide areas are damaged making the recolonization difficult. It is well known that the fishing effort is not homogeneously distributed. It is usually concentrated in areas that yield the best catches and that do not have obstructions that can damage the gears (Rijnsdorp et al., 1998). Consequently, the recolonization processes are complex and difficult to predict. The relations, if they exist, between the recovery in a never or very low exploited sea bottom and in a highly fished area remain uncertain (Collie et al., 2000).
However, experimental studies, although they do not necessarily reflect a general phenomenon, are important tools for basic studies allowing treatment – control comparisons to be made which is not generally possible in commercially exploited areas. The problem is to identify the appropriate spatial and temporal scales to be able to infer the results from an experimental study to commercial fishing grounds.
|
Acknowledgements |
|---|
The project was funded by the EC (contract DG XIV – n° 97/0020). I wish to thank R. Micheli (Cibm, Livorno, Italy), A. Vannucci (Aplysia, Livorno, Italy), and L. Nicoletti (Icram, Rome, Italy) for their contribution in the field and laboratory; S. De Ranieri (Cibm, Livorno, Italy), M. Kaiser (University of Wales, Bangor, UK), F. Biagi (University of Pisa, Italy), and G.D. Ardizzone (University of Rome, Italy) for their scientific suggestions. P. Sartor (Cibm, Livorno, Italy) provided all the information regarding the experimental vessel and the fishing regulation. Sidescan sonar survey and grain size analysis were carried out by Geomarine s.a.s. (Senigallia, Ancona, Italy). I have really appreciated all the suggestions by M. Bergmann (University of Wales, Bangor, UK).
|
References |
|---|
|
TopIntroductionMaterial and methodsResultsDiscussionReferences |
|---|
-
Ardizzone G.D., Tucci P., Somaschini A., Belluscio A. (2000) Is the bottom trawling partly responsible for the regression of Posidonia oceanica meadows in the Mediterranean Sea? In Kaiser M.J. and de Groot J. (Eds.). The Effects of Fishing on Non-target Species and Habitats(Blackwell Scientific, Oxford, England UK) pp. 37–46.
Ball B.J., Munday B.W., Tuck I. (2000) Effects of otter trawling on the benthos and environment in muddy sediments. In Kaiser M.J. and de Groot J. (Eds.). The Effects of Fishing on Non-target Species and Habitats(Blackwell Scientific, Oxford, England UK) pp. 69–82.
Bellan G. (1991) Characteristic, indicative and sentinel species from the conception to the utilization. In Ravera G. (Ed.). Terrestrial and Aquatic Ecosystems: Perturbation and RecoveryEllis Horwood Lt pp. 95–100.
Bergman M.J.N. and van Santbrink J.W. (2000) Mortality in megafaunal benthic populations caused by trawl fisheries on the Dutch continental shelf in the North Sea in 1994. ICES Journal of Marine Science 57:1321–1331.
Collie J.S., Escanero G.A., Valentine P.C. (1997) Effects of bottom fishing on the benthic megafauna of Georges Bank. Marine Ecology Progress Series 155:159–172.[Web of Science]
Collie J.S., Hall S.J., Kaiser M.J., Poiners I.R. (2000) A quantitative analysis of fishing impacts on shelf-sea benthos. Journal of Animal Ecology 69:785–798.[CrossRef][Web of Science]
De Biasi A.M. (1999) The impact of fishing on the sea bottoms: choosing an experimental area. In Giovanardi O. (Ed.). Impact of Trawl Fishing on Benthic Communities(Il Leggio, Chioggia (VE)) pp. 61–77 131 pp.
De Biasi A.M., Ardizzone G.D., Biagi F., De Ranieri S., Demestre M., Kaiser M., Nicoletti L., Pacciardi L., Sanchez P., Sartor P., Vannucci A. (2002) Changes at very short time scale: an example from the marine benthic communities. Atti Associazione Italiana di Oceanologia e Limnologia 15:45–51.
Drabsch S.L., Tanner J.E., Connel S.D. (2001) Limited infaunal response to experimental trawling in previously untrawled areas. ICES Journal of Marine Science 58:1261–1271.
Gilkinson K., Paulin M., Hurley S., Schwinghamer P. (1998) Impact of trawl door scouring on infaunal bivalves: results of a physical trawl door model/dense sand interaction. Journal of Experimental Marine Biology and Ecology 224:291–312.[CrossRef][Web of Science]
Giovanardi O., Pranovi F., Franceschini G. (1998) "Rapido" trawl fishing in the Northern Adriatic: preliminary observations of the effects on macrobenthic communities. Acta Adriatica 39:37–52.
Hall S.J. (1994) Physical disturbance and marine benthic communities: life in unconsolidated sediements. Oceanography and Marine Biology Annual Review 32:179–239.
Hall S.J. (1999) The Effects of Fishing on Marine Ecosystem and Communities(Blackwell Science, Oxford) 274 pp.
Hall-Spencer J.M., Froglia C., Atkinson R.J.A., Moore P.G. (1999) The impact of rapido trawling for scallops, Pecten jacobaeus (L.), on the benthos of the Gulf of Venice. ICES Journal of Marine Science 56:111–124.
Jennings S. and Kaiser M. (1998) The effects of fishing on marine ecosystems. Advance in Marine Biology 34:201–252.
Kaiser M.J., Ramsay K., Richardson C.A., Spencer F.E., Brand A.R. (2000) Chronic fishing disturbance has changed shelf sea benthic community structure. Journal of Animal Ecology 69:494–503.[CrossRef][Web of Science]
Kaiser M.J. and Spencer B.E. (1996) The effects of beam-trawl disturbance on infaunal communities in different habitat. Journal of Animal Ecology 65:348–358.[CrossRef][Web of Science]
Kaiser M.J. and de Groot S.J. (2000) Effects of Fishing on Non-target Species and Habitats: Biological, Conservation and Socio-economic Issues(Blackwell Science, Oxford) 399 pp.
Kenchington E.L.R., Prena J., Gilkinson K.D., Gordon D.C., Maclsaac C. Jr., Bourbonnais K., Schwinghamer P.J., Rowell T.W., McKeown D.L., Vass W.P. (2001) Effects of experimental otter trawling on the macrofauna of a sandy bottom ecosystem on the Grand Banks of Newfoundland. Canadian Journal of Fisheries and Aquatic Sciences 58:1043–1057.
Lambshead P.J.D., Platt H.M., Shaw K.M. (1983) The detection of differences among assemblages of marine benthic species based on an assessment of dominance and diversity. Journal of Natural History 17:859–874.[CrossRef][Web of Science]
Messieh S.N., Rowell W., Peer D.L., Cranford P.J. (1991) The effects of trawling, dredging and ocean dumping on the eastern Canadian continental shelf seabed. Continental Shelf Research 11:1237–1263.[CrossRef][Web of Science]
Morton B. (1996) The subsidiary impacts of dredging (and trawling) on a subtidal benthic molluscan community in the southern waters of Hong Kong. Marine Pollution Bulletin 32:701–710.[CrossRef][Web of Science]
Picard J. (1965) Recherches quantitatives sur les biocoenoses marines des substrats meubles dragables de la région marseillaise. Recueil des Travaux de la Station Marine d'Endoume 52:3–160.
Pranovi F., Giovanardi O., Franceschini G. (1998) Recolonisation dynamics in areas disturbed by bottom fishing gears. Hydrobiologia 375/376:125–135.
Pranovi F., Raicevich S., Franceschini G., Farrace M.G., Giovanardi O. (2000) Rapido trawling in the Northern Adriatic Sea: effects on benthic communities in an experimental area. ICES Journal of Marine Science 57:517–524.
Pranovi F., Raicevich S., Franceschini G., Torricelli P., Giovanardi O. (2001) Discard analysis and damage to non-target species in the "rapido" trawl fishery. Marine Biology 139:863–875.[CrossRef]
Rijnsdorp A.D., Buys A.M., Storbeck F., Visser E.G. (1998) Micro-scale distribution od beam-trawling 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 Journal of Marine Science 55:403–419.
Rumohr H. and Krost P. (1991) Experimental evidence of damage to benthos to bottom trawling with special reference to Arctica islandica. Meeresforschung 33:340–345.
Thrush S.F., Hewit J.E., Cummings V.J., Dayton P.K. (1995) The impact of habitat disturbance by scallop dredging on marine benthic communities: what can be predicted from the results of experiments? Marine Ecology Progress Series 129:141–150.[Web of Science]
Thrush S.F., Hewit J.E., Cummings V.J., Dayton P.K., Cryer M., Turner S.J., Funnel G.A., Budd R.G., Milburn C.J., Wilkinson M.R. (1998) Disturbance of marine benthic habitat by commercial fishing: impacts at the scale of fishery. Ecological Application 8:866–879.[CrossRef]
Tuck I.D., Hall S.J., Robertson M.R., Armstrong E., Basford D.J. (1998) Effects of physical trawling disturbance in a previously unfished sheltered Scottish sea loch. Marine Ecology Progress Series 162:227–242.[Web of Science]
CiteULike 
Connotea 
Del.icio.us What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||