Physical Disturbance and Marine Benthic Communities: The Effects of Mechanical Harvesting of Cockles on Non-Target Benthic Infauna

Hall, Stephen J.; Harding, M. James

doi:10.2307/2404893

Cited by 79 publications

(61 citation statements)

References 17 publications

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“…On the basis of experiments to study the effects of cockle-dredging on non-target species in an intertidal area in Scotland, Hall & Harding (1997) concluded that, although the non-target benthic fauna may suffer high levels of mortality, 'recovery is rapid and the overall effect on populations is probably low' (but see Ferns, Rostron & Siman 2000). Hall & Harding (1997) also suggest that effects might vary with plot size.…”

Section:         mentioning

confidence: 99%

Long‐term indirect effects of mechanical cockle‐dredging on intertidal bivalve stocks in the Wadden Sea

Piersma

Koolhaas

Dekinga

et al. 2001

Journal of Applied Ecology

166

181

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Summary1. There is world-wide concern about the effects of bottom-dredging on benthic communities in soft sediments. In autumn 1988, almost a third of the 50-km 2 intertidal system around the island of Griend in the western Dutch Wadden Sea was suction-dredged for edible cockles Cerastoderma edule and this study assessed subsequent effects. An adjacent area not directly touched by this fishery and an area from which the mussel Mytilus edulis beds were removed, served as reference areas. 2. Sediment characteristics, together with the total stock size and settlement densities of Cerastoderma , Baltic tellin Macoma balthica and soft-shelled clam Mya arenaria , were documented during 11 successive autumns before (August-September 1988) and after (August-September 1989-98) the suction-dredging event in fished and unfished areas. Four other areas in the Dutch Wadden Sea, where changes in densities of juvenile bivalves from 1992 to 1998 were measured, served as additional reference locations. 3. Between 1988 and 1994, median sediment grain size increased while silt was lost from sediments near Griend that were dredged for cockles. The initial sediment characteristics were re-attained by 1996. 4. After the removal of all Mytilus and most Cerastoderma , the abundance of Macoma declined for 8 years. From 1989 to 1998, stocks of Cerastoderma , Macoma and Mytilus did not recover to the 1988 levels, with the loss of Cerastoderma and Macoma being most pronounced in the area dredged for cockles. Declines of bivalve stocks were caused by particularly low rates of settlement in fished areas until 1996, i.e. 8 years after the dredging. 5. A comparison of settlement in the short (1992-94) and medium term (1996-98) after cockle-dredging in several fished and unfished areas spread over the entire Dutch Wadden Sea, showed a significant negative effect of dredging on subsequent settlement of Cerastoderma . Macoma also declined, but not significantly. 6. We conclude that suction-dredging of Cerastoderma had long-lasting negative effects on recruitment of bivalves, particularly the target species, in sandy parts of the Wadden Sea basin. Initially, sediment reworking by suction-dredging (especially during autumn storms) probably caused losses of fine silts. Negative feedback processes appeared to follow that prevented the accumulation of fine-grained sediments conducive to bivalve settlement.

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Section:         mentioning

confidence: 99%

Long‐term indirect effects of mechanical cockle‐dredging on intertidal bivalve stocks in the Wadden Sea

Piersma

Koolhaas

Dekinga

et al. 2001

Journal of Applied Ecology

166

181

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“…In a comparative study between the effects of the hydraulic dredge and tractor dredger, Hall and Harding (1997) found that the former gear had a higher impact on the benthic fauna. However, this impact was smothered within 56 days.…”

Section: Discussionmentioning

confidence: 99%

“…The ecological effects of cockle harvesting using mechanical methods are well documented (e.g. Moore, 1991;Rostron, 1993;Rostron, 1995; see review by Rees, 1996;Hall and Harding, 1997;Ferns et al, 2000;Piersma et al, 2001), whereas studies on the impacts of non-mechanical methods (such as the harvesting techniques used in Ria Formosa or hand raking) on the ecosystem (e.g. Spencer, 1996;Kaiser et al, 2001) are scarce.…”

Section: Resumen: Impacto De La Pesca Del Berberecho Con Artes No Mecmentioning

confidence: 99%

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mentioning

confidence: 99%

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Immediate effect of intertidal non-mechanised cockle harvesting on macrobenthic communities: a comparative study

Leitao¹,

Gaspar²

2007

Sci. Mar.

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Palabras clave: Cerastoderma edule, berberechos, impactos de la pesca, rastro de mano, cuchillo de marisqueo, Ría Formosa.such as tractor dredging, suction dredging or hydraulic dredging techniques (Hall and Harding, 1997;Ferns et al., 2000). There is a growing concern and considerable debate within the scientific community concerning both the magnitude of the impact of these mechanical methods on habitat complexity and the ability of harvested areas to recover. However, if the high number of harvesters involved in the cockle fishery is taken into consideration, the impacts of non-mechanised cockle harvesting on the ecosystem should also be considered since they could produce similar environmental effects as mechanical harvesting. In Ria Formosa, a coastal lagoon located in the Algarve coast (southern Portugal), bivalve species have been harvested since ancient times (Ruano, 1997). Among the species that are harvested, the cockle (Cerastoderma edule) is one of the most significant. Historically, cockle harvesting has been carried out by hand over extensive beds that are exposed during low tide, with fishermen digging and overturning the sediment, using a local traditional fishing gear called a harvesting-knife (HK). However, over the last six years an increasing use of hand-dredges (HD) for cockles has been recorded, despite being an illegal fishing gear according to the Ria Formosa Natural Park's present regulation. As a result of HD usage, conflicts have arisen between fishermen using traditional methods (HK) and those using the HD. HK fishermen argue that using hand dredges inside the lagoon causes a huge impact on the macrofauna. HD fishermen believe that this impact is minimal and similar to the impact induced by the HK, since the HD catches are almost exclusively composed of cockles. Nevertheless, no one has yet assessed the effects of the two fishing methods on the ecosystem.Despite the importance of the cockle fishery, the Ria Formosa is also an area of considerable conservational importance, primarily for its expanse of intertidal habitats and saltmarshes. This reinforces the need to assess the environmental impacts of this fishery. The ecological effects of cockle harvesting using mechanical methods are well documented (e.g. Moore, 1991;Rostron, 1993;Rostron, 1995; see review by Rees, 1996;Hall and Harding, 1997;Ferns et al., 2000;Piersma et al., 2001), whereas studies on the impacts of non-mechanical methods (such as the harvesting techniques used in Ria Formosa or hand raking) on the ecosystem (e.g. Spencer, 1996;Kaiser et al., 2001) are scarce. Cockle beds are inhabited by a variety of other benthic organisms (non-target species) and thus, similarly to other fisheries, harvesting causes disturbances to associated macrobenthic fauna (e.g. Beukema, 1995;Kaiser, et al., 1998;Gaspar et al., 2003). Moreover, removing, damaging or killing some species from a community can alter its structure in the short and/or long term (e.g. Hall et al., 1993;Dayton et al., 1995;Philippart, 1998;Ferns et al., 2000). How...

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“…We suggest that recovery from disturbance occurs gradually through adult migration from sediments surrounding the plots rather than by recruitment of juveniles as the timing and duration of the experiment excluded recruitment as a recovery mechanism. This dispersal may depend on sediment bed-load transport of large amounts of sediment and adult fauna into areas that have been trawled or because of exposure to wave action and currents, as suggested in Hall and Harding (1997) (mechanical harvesting of cockles) (as cited in Kaiser et al, 2001). Intertidal L. conchilega reefs are probably more resilient to trawling because of (1) their adaptation to continuous natural disturbances (wave action and wind stress) and (2) the smaller number of associated species.…”

Section: Recovery Mechanismmentioning

confidence: 99%

Experimental beam-trawling in Lanice conchilega reefs: Impact on the associated fauna

et al. 2008

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To study fisheries impact at the species level in temperate sandy bottom areas, a controlled field manipulation experiment was designed focusing on areas with high densities of the habitat-structuring, tube-dwelling polychaete Lanice conchilega (i.e. L. conchilega reefs). The hypothesis was that the impact on L. conchilega would be minimal, but that the fauna benefiting from the biogenically structured habitat would be impacted by beam-trawling. In this study, the impact of beam-trawl passage on intertidal L. conchilega reefs and its associated fauna was quantified. A treatment zone was exposed to a one-off experimental trawling. Subsequently, the impact on and recovery of the associated fauna was investigated for a period of 9 days post-impact. Community analysis showed a clear impact followed by a relatively quick recovery as apparent through MDS analysis (stress 0.06), a significant (p < 0.001) IMS of 0.61, through ANOSIM analysis: significant (p = 0.001) dissimilarities between treatment and control and through SIMPER analysis (decreasing dissimilarities over time). This impact and subsequent recovery was largely explained by two species: Eumida sanguinea and Urothoe poseidonis. Species analysis confirmed the beam-trawl passage significantly (p = 0.001) impacted E. sanguinea for the whole period of the experiment. The experiment confirmed that closely associated species of L. conchilega reefs are impacted by beam-trawl fisheries. This small-scale intertidal study provides some pointers which indicate that the tightly associated species will be impacted significantly when beam-trawling L. conchilega reefs in subtidal areas.

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Physical Disturbance and Marine Benthic Communities: The Effects of Mechanical Harvesting of Cockles on Non-Target Benthic Infauna

Cited by 79 publications

References 17 publications

Long‐term indirect effects of mechanical cockle‐dredging on intertidal bivalve stocks in the Wadden Sea

Long‐term indirect effects of mechanical cockle‐dredging on intertidal bivalve stocks in the Wadden Sea

Immediate effect of intertidal non-mechanised cockle harvesting on macrobenthic communities: a comparative study

Experimental beam-trawling in Lanice conchilega reefs: Impact on the associated fauna

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