The Marine Life Information Network

Substratum loss

Benchmark. All of the substratum occupied by the species or biotope under consideration is removed. A single event is assumed for sensitivity assessment. Once the activity or event has stopped (or between regular events) suitable substratum remains or is deposited. Species or community recovery assumes that the substratum within the habitat preferences of the original species or community is present. Further details

Evidence

Venerupis corrugata lives infaunally in mixed sandy sediments, often attached to small stones or shell fragments. Removal of the substratum would remove the entire population of the species and therefore intolerance is recorded as high. Recoverability is recorded as high (see additional information below).

Smothering

Benchmark. All of the population of a species or an area of a biotope is smothered by sediment to a depth of 5 cm above the substratum for one month. Impermeable materials, such as concrete, oil, or tar, are likely to have a greater effect. Further details.

Evidence

Venerupis corrugata typically burrows to a depth of 3-5 cm and is often attached to small stones or shell fragments by byssal threads. It is an active suspension feeder and therefore requires its siphons to be above the sediment surface in order to maintain a feeding and respiration current. Kranz (1972) (cited in Maurer et al., 1986) reported that shallow burying siphonate suspension feeders are typically able to escape smothering with 10-50 cm of their native sediment and relocate to their preferred depth by burrowing. This is likely to apply to the proportion of the Venerupis corrugata population which is not firmly attached by byssal threads. However, those individuals that are attached may be inhibited from relocating rapidly following smothering with 5 cm of sediment and some mortality is expected to occur. Intolerance is therefore recorded as intermediate. Recoverability is recorded as high (see additional information below).

Increase in suspended sediment

Benchmark. An arbitrary short-term, acute change in background suspended sediment concentration e.g., a change of 100 mg/l for one month. The resultant light attenuation effects are addressed under turbidity, and the effects of rapid settling out of suspended sediment are addressed under smothering. Further details

Evidence

Venerupis corrugata is an active suspension feeder, trapping food particles on the gill filaments (ctenidia). An increase in suspended sediment is therefore likely to affect both feeding and respiration by potentially clogging the ctenidia. In Venerupis corrugatus, increased particle concentrations between low and high tide resulted in increased clearance rates and pseudofaeces production with no significant increase in respiration rate (Stenton-Dozey & Brown, 1994). It seems likely therefore that Venerupis corrugata would also be able to clear its feeding and respiration structures, although at high particle concentrations, there may be some energetic cost. Over one month, there is not likely to be any mortality. Intolerance is therefore recorded as low. When the suspended sediment falls to typical levels, feeding and respiration would be expected to quickly return to normal so recoverability is recorded as very high.

Decrease in suspended sediment

Benchmark. An arbitrary short-term, acute change in background suspended sediment concentration e.g., a change of 100 mg/l for one month. The resultant light attenuation effects are addressed under turbidity, and the effects of rapid settling out of suspended sediment are addressed under smothering. Further details

Evidence

Venerupis corrugata is an active suspension feeder, feeding on phytoplankton and particulate organic food. A decrease in suspended sediment would decrease food availability and therefore may impair growth rates. However, over a one-month period (the benchmark) it is unlikely that survival would be affected. Hence, intolerance is recorded as low. When turbidity returns to normal levels, the growth rate should soon return to normal and hence recoverability is recorded as very high.

Desiccation

1. A normally subtidal, demersal or pelagic species including intertidal migratory or under-boulder species is continuously exposed to air and sunshine for one hour.
2. A normally intertidal species or community is exposed to a change in desiccation equivalent to a change in position of one vertical biological zone on the shore, e.g., from upper eulittoral to the mid eulittoral or from sublittoral fringe to lower eulittoral for a period of one year. Further details.

Evidence

The majority of the population of Venerupis senegalensis live infaunally in muddy sand, a substratum with a high water content, and is therefore protected from desiccation stress. Additionally, bivalves are able to respond to desiccation stress by valve adduction during periods of emersion. It is likely that the species would be able to retain enough water in the shell to prevent mortality during the benchmark exposure period of one hour. However, during the period of emersion, the species would not be able to feed and respiration would be compromised, so there is likely to be some energetic cost. Intolerance is therefore recorded as low. On immersion, metabolic activity should quickly return to normal and recoverability is therefore recorded as very high.

Increase in emergence regime

Benchmark. A one hour change in the time covered or not covered by the sea for a period of one year. Further details

Evidence

Venerupis corrugata occurs on the lower shore and so is vulnerable to an increase in emergence. The species does not colonize further up the shore and therefore must be limited by one or more factors including desiccation, temperature and wave exposure. The benchmark for emergence is an increase in exposure for one hour every tidal cycle for a year. During this time, exposed individuals will not be able to feed and respiration will be compromised. Over the course of a year, it is expected that the resultant energetic cost to the individuals highest up the shore will lead to some mortality and therefore intolerance is recorded as intermediate. Recoverability is recorded as high (see additional information below).

Decrease in emergence regime

Benchmark. A one hour change in the time covered or not covered by the sea for a period of one year. Further details

Evidence

Venerupis corrugata thrives in the subtidal zone and would therefore be tolerant of a decrease in emergence. It is possible that a decreased emergence regime would allow the species to colonize further up the shore.

Increase in water flow rate

A change of two categories in water flow rate (view glossary) for 1 year, for example, from moderately strong (1-3 knots) to very weak (negligible). Further details

Evidence

Venerupis corrugata thrives in low-energy environments such as sheltered beaches where the tidal flow is weak (Connor et al., 1997a). The benchmark for an increase in water flow would be a change to strong flow for one year (see glossary). This would place the species outside its habitat preferences and some mortality would be likely to occur, probably due to interference with respiration and feeding, although this is poorly understood. In addition, the increased water flow rate will change the sediment characteristics in which the species lives, primarily by re-suspending and preventing the deposition of finer particles (Hiscock, 1983). This may result in erosion of the preferred habitat, which would contribute further to mortality. Intolerance is therefore recorded as intermediate. Recoverability is recorded as high (see additional information below).

Decrease in water flow rate

A change of two categories in water flow rate (view glossary) for 1 year, for example, from moderately strong (1-3 knots) to very weak (negligible). Further details

Evidence

Venerupis corrugata thrives in low-energy environments such as sheltered beaches where the tidal flow is weak (Connor et al., 1997a). It is an active suspension feeder capable of generating its own feeding and respiration current by ciliary action. The species is therefore likely to tolerate a decrease in water flow rate. However, it should be noted that decreases in water flow will also result in an increased risk of smothering and changes in oxygenation. These factors are discussed in their relevant sections.

Increase in temperature

1. A short-term, acute change in temperature; e.g., a 5°C change in the temperature range for three consecutive days. This definition includes ‘short-term’ thermal discharges.
2. A long-term, chronic change in temperature; e.g. a 2°C change in the temperature range for a year. This definition includes ‘long term’ thermal discharges.

For intertidal species or communities, the range of temperatures includes the air temperature regime for that species or community. Further details

Evidence

The geographic range of Venerupis corrugata extends to northern Africa. Therefore, the species must be capable of surviving in higher temperatures than it experiences in Britain and Ireland and thus would be expected to tolerate temperature change over an extended period. A population of Venerupis corrugata endured a temperature rise from 13 to 18°C over 5 hours in a rockpool and then a drop to 14°C following inundation by the tide, with no obvious ill effects (Stenton-Dozey & Brown, 1994). Albentosa et al. (1994) investigated the scope for growth of Venerupis corrugata (studied as Venerupis pullastra) by considering rates of ingestion, respiration and excretion at varying temperatures. Scope for growth was found to increase with temperature until the optimum at 20°C after which it declined. Hence, it is expected that Venerupis corrugata would be able to tolerate a long-term, chronic temperature increase and a short-term acute change with no mortality. However, a rapid increase in temperature may result in sub-optimal conditions for growth and reproduction and therefore an intolerance of low is recorded. When the temperature decreases, metabolic activity should quickly return to normal and therefore recoverability is recorded as very high.

Decrease in temperature

1. A short-term, acute change in temperature; e.g., a 5°C change in the temperature range for three consecutive days. This definition includes ‘short-term’ thermal discharges.
2. A long-term, chronic change in temperature; e.g. a 2°C change in the temperature range for a year. This definition includes ‘long term’ thermal discharges.

For intertidal species or communities, the range of temperatures includes the air temperature regime for that species or community. Further details

Evidence

The geographic range of Venerupis corrugata extends to northern Norway. Therefore, the species must be capable of survival at lower temperatures than it does in Britain and Ireland and would be expected to tolerate a chronic temperature decrease over an extended period. However, in the harsh British winter of 1962-63, when the south coast experienced temperatures 5-6°C below average for a period of two months, Venerupis corrugata (studied as Venerupis pullastra) suffered 50% mortality around the Isle of Wight and near 100% mortality in Poole Harbour (Waugh, 1964). The species is less tolerant therefore of acute decreases in temperature and an intolerance of intermediate is recorded. Recoverability is recorded as high (see additional information below).

Increase in turbidity

1. A short-term, acute change; e.g., two categories of the water clarity scale (see glossary) for one month, such as from medium to extreme turbidity.
2. A long-term, chronic change; e.g., one category of the water clarity scale (see glossary) for one year, such as from low to medium turbidity. Further details

Evidence

Venerupis corrugata does not require light and therefore is not directly affected by an increase in turbidity for the purposes of light attenuation. An increase in turbidity may affect primary production in the water column and therefore reduce the availability of phytoplankton food. However, phytoplankton will also immigrate from distant areas and so the effect may be decreased. As the turbidity increase only persists for a year, decreased food availability would probably only affect growth and fecundity so an intolerance of low is recorded. As soon as light levels return to normal, primary production will increase and hence recoverability is recorded as very high.

Decrease in turbidity

1. A short-term, acute change; e.g., two categories of the water clarity scale (see glossary) for one month, such as from medium to extreme turbidity.
2. A long-term, chronic change; e.g., one category of the water clarity scale (see glossary) for one year, such as from low to medium turbidity. Further details

Evidence

Venerupis corrugata does not require light and therefore would not be affected by a decrease in turbidity for light attenuation purposes. It is possible that decreased turbidity would increase primary production in the water column and by micro-phyto benthos. The resultant increase in food availability may enhance growth and reproduction in Venerupis corrugata, but only if the food was previously limiting.

Increase in wave exposure

A change of two ranks on the wave exposure scale (view glossary) e.g., from Exposed to Extremely exposed for a period of one year. Further details

Evidence

Venerupis corrugata characteristically inhabits muddy sand in low-energy environments. This suggests that it would, in some way, be intolerant of an increase in wave exposure. An increase in wave exposure by two categories for one year would be likely to affect the species in several ways. Fine sediments would be eroded (Hiscock, 1983) resulting in the likely reduction of the habitat of Venerupis senegalensis. Strong wave action may cause damage or withdrawal of the siphons, resulting in loss of feeding opportunities and compromised growth. Furthermore, individuals may be dislodged by scouring from sand and gravel mobilized by increased wave action. For the above reasons, some mortality would be likely to occur and intolerance is recorded as intermediate. Recoverability is recorded as high (see additional information below).

Decrease in wave exposure

A change of two ranks on the wave exposure scale (view glossary) e.g., from Exposed to Extremely exposed for a period of one year. Further details

Evidence

Venerupis corrugata inhabits muddy sand in low-energy environments, including 'extremely sheltered' on the wave exposure scale (Connor et al., 1997a). It is an active suspension feeder and is capable of maintaining a feeding and respiration current by ciliary action. It is therefore unlikely to be affected by a decrease in wave exposure. However, it should be noted that decreased wave exposure will lead to changes in oxygenation and an increased risk of smothering due to siltation. These factors are discussed in their relevant sections.

Noise

1. Underwater noise levels e.g., the regular passing of a 30-metre trawler at 100 metres or a working cutter-suction transfer dredge at 100 metres for one month during important feeding or breeding periods.
2. Atmospheric noise levels e.g., the regular passing of a Boeing 737 passenger jet 300 metres overhead for one month during important feeding or breeding periods. Further details

Evidence

No information was found concerning the intolerance of Venerupis corrugata to noise. The siphons are likely to detect vibrations and are probably withdrawn as a predator avoidance mechanism, but the species is probably not sensitive at the level of the benchmark.

Visual presence

Benchmark. The continuous presence for one month of moving objects not naturally found in the marine environment (e.g., boats, machinery, and humans) within the visual envelope of the species or community under consideration. Further details

Evidence

No information was found concerning the intolerance of Venerupis corrugata to visual disturbance. It is not a visual species and is not likely to be sensitive.

Abrasion & physical disturbance

Benchmark. Force equivalent to a standard scallop dredge landing on or being dragged across the organism. A single event is assumed for assessment. This factor includes mechanical interference, crushing, physical blows against, or rubbing and erosion of the organism or habitat of interest. Where trampling is relevant, the evidence and trampling intensity will be reported in the rationale. Further details.

Evidence

Despite their robust body form, bivalves are vulnerable to physical abrasion. For example, as a result of dredging activity, mortality and shell damage has been reported in Mya arenaria and Cerastoderma edule (Cotter et al., 1997). Similarly, beam trawling in sand sediments was shown to adversely affect a number of bivalve species depending on their size, the robustness of their shells or density (Bradshaw and van Santbrink, 2000). Venerupis corrugata is a shallow burrower and may be damaged by the passing of a scallop dredge and so intolerance is recorded as intermediate. Recoverability is assessed as high (see additional information below).

Displacement

Benchmark. Removal of the organism from the substratum and displacement from its original position onto a suitable substratum. A single event is assumed for assessment. Further details

Evidence

When displaced and returned to the surface of the substratum, Venerupis corrugata is able to bury itself (e.g. Kaschl & Carballeira, 1999). This probably occurs naturally due to shifting sediments caused by storms. However, while exposed at the sediment surface, the species is more vulnerable to predation and some mortality may occur. Intolerance is therefore recorded as intermediate. Recoverability is recorded as high (see additional information below).

Synthetic compound contamination

Sensitivity is assessed against the available evidence for the effects of contaminants on the species (or closely related species at low confidence) or community of interest. For example:

• evidence of mass mortality of a population of the species or community of interest (either short or long term) in response to a contaminant will be ranked as high sensitivity;
• evidence of reduced abundance, or extent of a population of the species or community of interest (either short or long term) in response to a contaminant will be ranked as intermediate sensitivity;
• evidence of sub-lethal effects or reduced reproductive potential of a population of the species or community of interest will be assessed as low sensitivity.

The evidence used is stated in the rationale. Where the assessment can be based on a known activity then this is stated. The tolerance to contaminants of species of interest will be included in the rationale when available; together with relevant supporting material. Further details.

Evidence

No information was found concerning the effects of synthetic chemicals specifically on Venerupis corrugata. However, inference can be drawn from related species. Beaumont et al. (1989) concluded that bivalves are particularly sensitive to tri-butyl tin (TBT), the toxic component of many antifouling paints. For example, when exposed to 1-3 µg TBT/l, Cerastoderma edule and Scobicularia plana suffered 100% mortality after 2 weeks and 10 weeks respectively. There is also evidence that TBT causes recruitment failure in bivalves, either due to reproductive failure or larval mortality (Bryan & Gibbs, 1991). Venerupis decussata was found to be a potentially useful indicator of TBT pollution; concentrating and tolerating high levels of the compound in its tissues (bioconcentration factors ranged from 10,000 to 40,000) (Gomez-Arica et al., 1999). In light of the intolerance of other bivalve species, intolerance of Venerupis corrugata to synthetic chemicals is assessed as high. Recoverability is recorded as high (see additional information below).

Heavy metal contamination

Evidence

The capacity of bivalves to accumulate heavy metals in their tissues, far in excess of environmental levels, is well known. Reactions to sub-lethal levels of heavy metal stressors include siphon retraction, valve closure, inhibition of byssal thread production, disruption of burrowing behaviour, inhibition of respiration, inhibition of filtration rate, inhibition of protein synthesis and suppressed growth (see review by Aberkali & Trueman, 1985). Kaschl & Carballeira (1999) investigated the effect of sediment contamination on Venerupis corrugata (studied as Venerupis pullastra) by exposing the species to sediments spiked with copper sulphate. Following placement of clams on the sediment surface, slowing of burial was observed in proportion to the concentration of copper added to the sediment. The effect was detectable at a pore water concentration of 95 µg Cu/l. At the highest copper concentrations (spiking solution concentration > 125 mg Cu/l), the majority of clams closed up and did not bury. Spiking of the sediments with copper also resulted in re-emergence between 24 and 120 hours after burial, a behaviour not observed in controls. The proportion of clams re-emerging increased with the copper concentration in the sediment, and was concluded to be an avoidance behaviour. Kaschl & Carballeira (1999) suggested that the delay in burial at low copper concentrations was due to physiological disruption as it did not avoid exposure to the toxin and further increased the risk of predation. At higher concentrations, there was a payoff between toxin avoidance (by valve closure or re-emergence) and predator avoidance. The copper 10-day LC₅₀ for Venerupis corrugata was found to be 88 µg/l in sandy sediments (Kaschl & Carballeira, 1999). For reference to polluted UK sediments, copper concentration in the interstitial water of Restronguet Creek sediments has been measured at 100µg/l (Bryan & Langston, 1992). Abbot (1977) investigated the intolerance of Venerupis corrugata (studied as Venerupis pullastra) to molybdenum and concluded it was not toxic at levels realistically encountered in the marine environment. In light of the lethal and sublethal effects of copper, intolerance of Venerupis corrugata to heavy metals is assessed as high. Recoverability is recorded as high (see additional information below).

Hydrocarbon contamination

Evidence

Suchanek (1993) reviewed the effects of oil on bivalves. Sublethal concentrations may produce substantially reduced feeding rates and/or food detection ability, probably due to ciliary inhibition. Respiration rates have increased at low concentrations and decreased at high concentrations. Generally, contact with oil causes an increase in energy expenditure and a decrease in feeding rate, resulting in less energy available for growth and reproduction. Sublethal concentrations of hydrocarbons also reduce byssal thread production (thus weakening attachment) and infaunal burrowing rates. No information was found on the effects of hydrocarbons on Venerupis corrugata specifically. Mortality following oil spills has been recorded in other bivalve species, e.g. Mya arenaria (Dow, 1978; Johnston, 1984) and Cerastoderma edule (SEEEC, 1998). Therefore, it is possible that some mortality of Venerupis corrugata would result from hydrocarbon contamination and an intolerance of intermediate is recorded. Recoverability is recorded as high (see additional information below).

Radionuclide contamination

Evidence

Stamouli & Papadapoulou (1990) investigated bioaccumulation of radioactive trivalent Chromium 51 (Cr-51) in a Venerupis species from Greece. Cr-51 is derived from nuclear tests, and disposal of radioactive waste and is one of the principal corrosion products of nuclear powered ships. Cr-51 was found to rapidly accumulate in Venerupis sp., predominantly in the shell, and reached a stable level in 8 days. No mortality was reported after 20 days. No further information was found concerning the effect of radionuclides on Venerupis corrugata.

Changes in nutrient levels

Evidence

No information regarding the direct effects of nutrients on Venerupis corrugata was found. However, increased nutrients are likely to enhance ephemeral algal and phytoplankton growth, increase organic material deposition and enhance bacterial growth. At low levels, an increase in phytoplankton and benthic diatoms may increase food availability for Venerupis corrugata, thus enhancing growth and reproductive potential (e.g. Beiras et al., 1993). However, increased levels of nutrient (beyond the carrying capacity of the environment) may result in eutrophication, algal blooms and concomitant reductions in oxygen concentrations (e.g. Rosenberg & Loo, 1988). Rosenberg & Loo (1988) reported mass mortalities of Mya arenaria and Cerastoderma edule following a eutrophication event in Sweden, although no direct causal link was established. It is likely therefore that a dramatic increase in nutrient levels would cause some mortality of Venerupis corrugata and so an intolerance of intermediate is recorded. Recoverability is recorded as high (see additional information below).

Increase in salinity

1. A short-term, acute change; e.g., a change of two categories from the MNCR salinity scale for one week (view glossary) such as from full to reduced.
2. A long-term, chronic change; e.g., a change of one category from the MNCR salinity scale for one year (view glossary) such as from reduced to low. Further details.

Evidence

Venerupis corrugata inhabits areas with full salinity (Connor et al., 1997a) and therefore probably relatively tolerant of increases in salinity. No information was found concerning intolerance to hypersaline conditions.

Decrease in salinity

1. A short-term, acute change; e.g., a change of two categories from the MNCR salinity scale for one week (view glossary) such as from full to reduced.
2. A long-term, chronic change; e.g., a change of one category from the MNCR salinity scale for one year (view glossary) such as from reduced to low. Further details.

Evidence

No information was found concerning the effects of decreasing salinity on Venerupis corrugata specifically. However, Lange (1972) reported that the muscle volume of Venerupis rhomboides, a stenohaline species, increased as salinity decreased, and hence concluded that the species was unable to regulate its muscle volume. Euryhaline bivalve species, however, e.g. Mya arenaria, Cerastoderma edule, were able to regulate muscle volume with changing salinity. Venerupis japonica displayed a variety of behavioural reactions in response to reduced salinity in the Sea of Japan (Yaroslavtseva & Fedoseeva, 1978). Salinities typically encountered ranged from 11-30 psu over the course of a day. Venerupis japonica was active down to 20 psu, below which it reacted with siphon withdrawal and valve closure. Mortality occurred if salinity remained below 14 psu for an extended period. Venerupis corrugata occurs in variable salinity conditions (Connor et al., 1997a). The benchmark includes a change of 2 categories on the salinity scale for a week (see glossary). This would place some of the population in a reduced salinity environment (<18 psu) and it is likely that some mortality would occur. An intolerance of intermediate is therefore recorded. Recoverability is recorded as high (see additional information below).

Changes in oxygenation

Benchmark.  Exposure to a dissolved oxygen concentration of 2 mg/l for one week. Further details.

Evidence

Venerupis corrugata is an aerobic organism and therefore will be intolerant in some degree to lack of oxygen. No evidence was found for specific effects of reduced oxygenation on Venerupis senegalensis but inferences can be drawn from the effects on other species. Jorgensen (1980) recorded the effects of low oxygen levels on benthic fauna in a Danish fjord. At dissolved oxygen concentrations of 0.2-1.0 mg/l the bivalves, Cerastoderma edule and Mya arenaria, suffered mortality between 2 and 7 days. Rosenberg & Loo (1988) reported mass mortalities of Mya arenaria and Cerastoderma edule in Sweden, following a eutrophication event which resulted in low oxygen concentrations over several years (often <1 ml O₂/l). At the benchmark level of exposure (2 mg/l for one week) it is expected that some mortality of Venerupis senegalensis would occur and an intolerance of intermediate is recorded. Recoverability is recorded as high (see additional information below).

Introduction of microbial pathogens/parasites

Benchmark. Sensitivity can only be assessed relative to a known, named disease, likely to cause partial loss of a species population or community. Further details.

Evidence

Navas et al. (1992) investigated the parasites of Venerupis corrugata (studied as Venerupis pullastra), from a population in south west Spain. The following were recorded:

• 36.6% prevalence of Perkinsus atlanticus; trophozoites found in the connective tissue of different organs with a very intensive hemocytic response, encysting the parasite and destroying tissue structure,
• 96.6% prevalence of ciliates in gills, including Trichodina sp.,
• 11.8% prevalence of turbellarians,
• 11.1% prevalence of trematodes.

Perkinsus atlanticus was also recorded as causing mortality in Venerupis decussatus and Venerupis aureus. Freire-Santos et al. (2000) recorded the presence of oocysts of Cryptosporidium sp. in Venerupis senegalensis (studied as Venerupis pullastra) collected from north west Spain and destined for human consumption.
The parasite loads of Venerupis senegalensis have the potential to cause mortality and therefore an intolerance of intermediate is recorded. Recoverability is recorded as high (see additional information below).

Introduction of non-native species

Sensitivity assessed against the likely effect of the introduction of alien or non-native species in Britain or Ireland. Further details.

Evidence

No information was found concerning the intolerance of Venerupis corrugata to alien or introduced species.

Extraction of this species

Benchmark. Extraction removes 50% of the species or community from the area under consideration. Sensitivity will be assessed as 'intermediate'. The habitat remains intact or recovers rapidly. Any effects of the extraction process on the habitat itself are addressed under other factors, e.g. displacement, abrasion and physical disturbance, and substratum loss. Further details.

Evidence

Venerupis corrugata is a very important commercial shellfish in Spain. It is harvested from the wild and raised in aquaculture (Jara-Jara et al., 2000). No information was found concerning the effect of harvesting on wild populations but it can be assumed that high mortality would occur in the intertidal where populations are more accessible to harvesters. However, not all individuals would be found and small ones would probably be left. The subtidal population is less likely to be exploited. An intolerance of intermediate is therefore recorded. Recoverability is recorded as high (see additional information below).

Extraction of other species

Benchmark. A species that is a required host or prey for the species under consideration (and assuming that no alternative host exists) or a keystone species in a biotope is removed. Any effects of the extraction process on the habitat itself are addressed under other factors, e.g. displacement, abrasion and physical disturbance, and substratum loss. Further details.

Evidence

Commercial extraction of other infaunal species is likely to have an effect on Venerupis corrugata where their distributions overlap. Hall & Harding (1997) demonstrated that commercial cockle harvesting by suction dredging had significant effects on soft-sediment infaunal communities. Following dredging, species numbers were reduced by up to 30% and abundances by up to 50%. Bait harvesting has also been shown to impact infaunal bivalves. For example, mechanical harvesting for Arenicola marina resulted in a drastic reduction in the population of Mya arenaria in the Wadden Sea (Beukema, 1995). Some mortality of Venerupis corrugata may occur therefore due to harvesting of other species so an intolerance of intermediate is recorded. Recoverability is recorded as high (see additional information below).