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

Removal of the substratum would also remove the entire population of Spisula solida and so intolerance has been assessed as high with a high recoverability.

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

Spisula solida is a fast burrowing bivalve. If Spisula solida were covered by sediments it would be able to reposition itself within the sediment. The location of the Waterford clam bed (Ireland) was examined in 2001. Fishermen compared the areas of the clam bed that provided the heaviest catches in two years. It was concluded that the location of the heaviest catches had moved slightly to the north-west of the harbour as part of the existing bed had silted up. This reduced the numbers of Spisula solida and the size of the clam patch (Fahy et al., 2003). However, intolerance has been assessed as intermediate to reflect the reduction in the size of the clam bed and Spisula numbers. Recoverability is assessed as high.

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

Levels of suspended sediment are likely to be most relevant to feeding. An increase in suspended sediment is likely to increase the rate of siltation (see smothering above) and the availability of food as Spisula solida is a suspension feeder. However, if the level of suspended sediment become too high it could cause the feeding structures to become clogged. It is unlikely that mortality would occur, therefore intolerance has been assessed as low with a very high recoverability.

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

Levels of suspended sediment are likely to be most relevant to feeding. A decrease in suspended sediment is likely to decrease the availability of food for suspension feeding bivalves. Mortality is unlikely to occur within 1 month (see benchmark) and so intolerance is assessed as low. When suspended sediment levels return to normal, so too should food availability and feeding.

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

Spisula solida can be found occasionally in the intertidal. A change in desiccation at the benchmark level would affect Spisula solida at the upper limit of their distribution and may cause mortalities. Therefore intolerance is assessed as intermediate with a high recoverability.

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

An increase in emergence at the benchmark level, would most likely to reduce the upper limits of Spisula solida and a portion of the population may be lost. Therefore intolerance is assessed as intermediate with high recoverability a recoverability.

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

A decrease in emergence at the benchmark level would benefit individuals ofSpisula solida allowing them to colonize further up the shoreline. Therefore, Spisula solida is tolerant* of this factor.

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

Spisula solida is found in areas ranging from strong to weak water flow. The increased water flow rate at the benchmark level would change the sediment characteristics in which the species lives. The substrata may be disturbed and the sediment on the seabed may erode. This scouring of sand and gravel causes coarse sediments to become unstable and difficult to burrow. Additionally, an increase in water flow may interfere with feeding and respiration.
Increased water flow may also lead to the dislodgement and abrasion of Spisula solida. However, the worn appearance of Spisula solida shells indicate that they inhabit areas of considerable water movement. A proportion of the population of Spisula solida may also be transported to another position on the seabed (bedload transport). Increased water flow may also prevent the settlement of larvae and juveniles decreasing the recruitment to an area (Hiscock, 1983). Therefore intolerance is assessed as intermediate with a high recoverability.

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

Spisula solida is found in areas ranging from strong to weak water flow. A decreased water flow rate may lower the dispersion of planktonic larvae and recruitment from other areas would be minimal. A decrease in water flow at the benchmark level would also result in increased deposition of fine suspended sediment (Hiscock, 1983), changing the sediment characteristics of the habitat in which the species lives. This may cause the substratum to become too muddy for Spisula solida which prefers sandy sediments and mixed sediments and avoids muddy sediments. Some mortality is, therefore, expected and an intolerance of intermediate is recorded. Recoverability is assessed as high

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

Schlieper et al. (1967) state that the upper temperature tolerance of Spisula solida is 30°C. Fahy et al. (2003) stated that the optimum condition of Spisula solida occurred at low temperature. However, Spisula solida does occur in areas as far south as Portugal and Morocco and is unlikely to be affected by an increases in temperature experienced in British and Irish waters. Therefore, Spisula solida would probably be tolerant of an increase in temperature at the benchmark level.

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

Fahy et al. (2003) stated that the optimum condition of Spisula solida occurred at low temperatures. Spisula solida also occurs as far north as sub-arctic Iceland and Norway. Therefore, Spisula solida would probably be tolerant of an increase in temperature at the benchmark level. However, the Spisula solida population of Red Wharf Bay, Anglesey was reported to demonstrate 'exceptionally heavy mortality' as a result of the 1962/63 winter (Crisp, 1964). Futhermore, the clam disappeared from the entire German Bight above the 20 m depth contour line during the 1995/96 winter where water temperatures at the sea bottom dropped to 0°C (M. Ruth, pers. comm.). Therefore, Spisula solida is probably highly intolerant of an acute temperature change, at the benchmark level.

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

Spisula solida does not require light and therefore the effects of increased turbidity on light attenuation are not directly relevant. An increase in turbidity may affect primary production in the water column and therefore reduce the availability of food. A turbidity increase for a year (see benchmark) would reduce the availability of food that would probably affect growth and fecundity and 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

Spisula solida does not require light and therefore the effects of increased turbidity on light attenuation are not directly relevant. A decrease in turbidity would increase primary production in the water column and food availability. Therefore it is likely that Spisula solida would be tolerant of a decrease in turbidity.

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

Spisula solida occurs in wave exposed to wave sheltered areas. This suggests that the species would be tolerant of a certain degree of sediment mobility associated with strong wave action. An increase in wave exposure (at the benchmark level) would place the majority of the population in areas frequently subject to strong wave action and the species may be affected in several ways. 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. Breon (1970; cited in Chícharo et al., 2002) reported that Spisula subtruncata, a species with a depth distribution similar to Spisula solida, exhibited increased burrowing activity when disturbed by wave action. Therefore intolerance is assessed as intermediate with a high recoverability.

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

Spisula solida occurs in wave exposed to wave sheltered areas. Decreased wave exposure at the benchmark level is likely to result in the establishment of more stable muddy sediment habitats. It is likely that this would result in mortality of Spisula solida. Spisula solida may also probably suffer increased competition from species better adapted to life in low energy environments. Intolerance is therefore assessed as intermediate with a high recoverability.

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 effects of noise on Spisula solida.

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

Spisula solida probably has little visual acuity and has been recorded as not sensitive to this factor.

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

The worn appearance of Spisula solida shells indicate that they inhabit areas of considerable water movement showing some tolerance for the effects of water movement on their robust shells (Ford, 1925).
Fishing for demersal species will disturb the surface layer of sediment and any protruding or shallow burrowing species. In Portugal, Spisula solida is caught at a depth of 7-9 m with a tooth dredge that can penetrate the sediment to a depth of 50 cm. Gaspar et al. (2002) noted that 93% of the uncaught Spisula solida were undamaged after experimental trawls, as they were well protected by their thick shells, and only 1% of the uncaught Spisula solida died (Gaspar et al., 2002).

The impacts caused by a fishing dredge significantly increased the number of exposed Spisula solida clams and the abundance of potential predators (Chícharo et al., 2002). The impact of the dredge increased the time needed for Spisula solida to rebury, which rendered them vulnerable to predation for longer periods (Chícharo et al., 2002). Under controlled conditions, it took Spisula solida three minutes to rebury themselves when displaced to the surface. However under trawling/dredging conditions it took Spisula solida nine minutes to rebury back into the sediments (Chícharo et al., 2002). Chícharo et al. (2002) stated that only 6% of Spisula solida not caught by the dredge were damaged and 94% were classified as having none or slight damage. Therefore intolerance has been assessed as intermediate as mortality may occur and recoverability has been assessed as high.

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

Spisula solida can burrow back down into the sediment very rapidly in its preferred substrata when it is displaced to the surface, therefore it is probably relatively tolerant of displacement. Spisula solida are subject to considerable water movements that cause displacement, which can carry individuals to another position where they will once again settle (Ford, 1925). This can be seen when different morphologies of Spisula solida occur in the same area. It is unlikely that mortalities will occur as Spisula solida has a thick solid shell and individual Spisula solida are often found with a worn appearance that is consistent with such activity (Ford, 1925).

The impacts caused by a fishing dredge significantly increased the number of exposed Spisula solida clams and the abundance of potential predators (Chícharo et al., 2002). The impact of the dredge increased the time needed for Spisula solida to rebury and rendered them vulnerable to predation for longer periods (Chícharo et al., 2002). Under controlled conditions it took Spisula solida three minutes to rebury when displaced however under trawling/dredging conditions it took Spisula solida nine minutes to rebury back into the sediments (Chícharo et al., 2002).

However such displacement could result in a loss of recruitment, increased predation and loss of mature individuals which will affect the viability of a population. Therefore intolerance is assessed as intermediate with a high recoverability.

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

Effects of synthetic contamination on bivalves are listed below.

• The burrowing and avoidance behaviour in the bivalves Tellina tenuis, Abra alba and Macoma balthica becomes impaired when they are exposed to phenol but no deaths occurred. Impairment of burrowing can leave bivalves vulnerable to predation and wave action (Møhlen & Kiørboe, 1983).
• High levels of tributyl tin (TBT), was implicated in slow growth and shell malformation 'balling' in the oyster Magallana gigas and larval mortality in Mytilus edulis (Beaumont et al., 1989) reducing recruitment levels. When exposed to 1-3 µgTBT/l Cerastoderma edule and Scobicularia plana suffered 100% mortality after two and ten weeks respectively (Beaumont et al., 1989).

There is also evidence that TBT causes recruitment failure in bivalves, either due to reproductive failure or larval mortality (Bryan & Gibbs, 1991). No information could be found on the effects of synthetic chemicals on Spisula solida. However, given the likely effects of TBT on bivalves, an intolerance of intermediate has been suggested, albeit with very low confidence.

Heavy metal contamination

Evidence

Many bivalve species accumulate heavy metals in their tissues, far in excess of environmental levels. Examples of the sub-lethal effects of heavy metals 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). Bryan (1984), suggested that Hg was the most toxic metal to bivalve molluscs in experimental studies while copper (Cu), cadmium (Cd) and zinc (Zn) were the most problematic for bivalves in the field. For example:

• exposure to 15 parts per billion (ppb) of copper was found to produce deformed embryos in Crassostrea virginicaand 33 ppb proved lethal to their larvae (Bryan, 1984).
• adults, on the other hand could withstand exposure to such levels, although through the immobilization of copper, they become green and unpalatable (Bryan, 1984);
• exposure to 100 ppb of cadmium for 15 weeks induced poor conditions and mortalities in adult Crassostrea virginica (Bryan, 1984).

No information specifically concerning the effects of heavy metal contamination on Spisula solida was found. However, the above evidence suggests that they may demonstrate sub-lethal effects, and in some cases, mortalities due to heavy metal contamination. Therefore, an intolerance of intermediate has been suggested, albeit with very low confidence.

Hydrocarbon contamination

Evidence

The effects of oil on invertebrate molluscs include:

• substantially reduced feeding rates and / or food detection ability probably due to ciliary inhibition;
• an increase in energy expenditure and a decrease in feeding rate, resulting in less energy available for growth and reproduction; and
• reduced infaunal burrowing rates at sublethal concentrations (Suchanek, 1993).

Spisula solidissima, a relative of Spisula solida, was exposed to oil during the North Cape oil spill on the coast of Rhode island (USA) (McCay et al., 2003). The number of bivalve mortalities was estimated by impact assessment modeling of acute toxicity. Results showed that Solida solidissima comprised of 97% of the total loss of bivalve production from the spill affected area with up to 40% mortality. It is probable that hydrocarbons would have a similar effect on Spisula solida, however no specific information could be found concerning the effects of hydrocarbons on Spisula solida. Therefore, an intolerance of intermediate has been suggested, albeit with low confidence.

Radionuclide contamination

Evidence

No information was found on the effects of radionuclides on Spisula solida.

Changes in nutrient levels

Evidence

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 may increase food availability for Spisula solida. However, increased levels of nutrients (beyond the carrying capacity of the environment) may result in eutrophication, algal blooms and reductions in oxygen concentrations that can cause hypoxia. Rosenberg & Loo (1988) reported mass mortalities of the bivalves Mya arenaria and Cerastoderma edule following a eutrophication event in Sweden, however no direct causal link was established. Spisula sp. were reported to accumulate algal toxins (e.g. saxitoxin and neosaxitoxin) in their tissues, and to retain toxins for long periods of time, ranging from months to over three years (see review by Landsberg, 1996). However, Landsberg (1996) found no evidence of resultant neoplasias (cancers) in Spisula sp. and did not report evidence of mortalities in Spisula sp. induced by algal blooms. However, Mahoney & Steimle (1979) reported mass mortalities of Spisula solidissima off the coast of New Jersey, due to of bottom water oxygen deficiency, as a result of the decay of a bloom of the dinoflagellate Ceratium tripos (see oxygenation below). Therefore, while Spisula sp. May be relatively tolerant of algal toxins, algal blooms may indirectly cause mortality due to hypoxia. Therefore, a dramatic increase in nutrient levels may cause some mortality of Spisula solida, and an intolerance of intermediate has been reported.

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

Spisula solida is typically found in full salinity conditions. Spisula solida exhibited the lowest salinity tolerance of excised gill tissues compared to the other species tested. After 24 hours, ciliary activity of 4 to 8 mm² gill pieces was observed in salinities that ranged from 15 to 50 parts per thousand (Theede, 1965; reported in Kinne, 1971b). The whole animal is likely to tolerate changes in salinity for longer, since it can isolate itself from its surroundings by closing its valves. However, at the benchmark level, an acute change for a period of 1 week or a chronic change for a year is likely to result in mortality. Therefore, an intolerance of high has been recorded.

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

Spisula solida exhibited the lowest salinity tolerance of excised gill tissues compared to the other species tested. After 24 hours, ciliary activity of 4 to 8 mm² gill pieces was observed in salinities that ranged from 15 to 50 parts per thousand (Kinne, 1971b). The whole animal is likely to tolerate changes in salinity for longer, since it can isolate itself from its surroundings by closing its valves. Spisula solida is typically found at full salinities (Theede et al., 1969) and is likely to be intolerant of a decrease in salinity. Distributionally, Spisula solida extends into the Kattegat (Sweden) but does not enter the brackish waters of the Baltic Sea as the salinity is lower (Theede et al., 1969). At the benchmark level, an acute change for a period of 1 week or a chronic change for a year is likely to result in mortality. Therefore intolerance has been assessed to be high with a high recoverability.

Changes in oxygenation

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

Evidence

Diaz & Rosenberg (1995) list Spisula solida as sensitive to hypoxic events. Spisula solida exhibited the fastest declines in ciliary movement in excised gill tissue, compared to other species tested at oxygen concentrations of 0.21 mg/l (Theede at al., 1969). Excised gill tissues of Spisula solida showed irreversible damage after 4 days under anoxic conditions after which ciliary movement completely stopped. The tolerance of the whole animal is likely to be longer, since it can shut itself off from the surrounding water by closing its valves.
Decay of an immense bloom of the dinoflagellate Ceratium tripos caused severe hypoxia over a 13,000 km² in the New York bight in 1976 (Mahoney & Steimle, 1979). The oxygen levels dropped 2ml/l (2.8 mg/l) over a wide area, and to as low as 0.1 ml/l (0.14 mg/l) in the worst affected areas, with an associated increase in hydrogen sulphide levels. Spisula solidissima was the most affected species and exhibited an estimated 69% mortality (Mahoney & Steimle, 1979).

Overall, the above evidence suggests that Spisula solida and related species are relatively intolerant of hypoxic conditions. Therefore, a change in oxygenation at the benchmark level would probably cause the population of Spisula solida to collapse and recoverability would be reliant on outside recruitment. Therefore intolerance is assessed as high with a high recoverability.

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

A number of organisms have been found living on and in individual specimens of Spisula solida.

• The gregarine Nematopis schneideri utilizes Spisula solida as an intermediate host (Lauckner, 1983).
• The ciliate Thigmorphyra bivalviorum was found on the gills of Spisula solida (Fenchel, 1965). However no information on their effects on Spisula solida could be found.
• The pea crab Pinnotheres pisum lives inside the shells of living bivalves. Møller Christensen (1962;cited in Lauckner, 1983) found an ovigenous female in Spisula solida. Berner (1952; cited in Cheung, 1967) noted that there was a partial or complete cessation in the production of gametes in those individuals that were infected with Pinnotheres pisum that averaged 1 cm or more in carapace length (CL). Smaller crabs very seldom affect bivalves in the manner above.

Therefore, intolerance is assessed as intermediate to reflect the cessation in the production of gonads, with a high recoverability.

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

There is no information on the effects of non-native species on Spisula solida.

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

Spisula solida is fished commercially. The impacts caused by a fishing dredge significantly increased the number of exposed Spisula solida clams and the abundance of potential predators (Chícharo et al., 2002). The impact of the dredge increased the time needed for Spisula solida individuals to rebury rendering them vulnerable to predation for longer.

Since 1992 a fishery for Spisula solida has taken place in Danish waters. Catches and landings were high in some years but totally absent in others during a ten year fishing period between 1992 and 2002 (Jensen et al., 2003). From 1992 to 1995 the fishery continued without any decrease in cpue (M. Ruth, pers. comm.). However, Spisula solida disappeared from the entire German Bight above the 20 m depth contour line during the 1995/96 winter where water temperatures at the sea bottom dropped to 0°C (M. Ruth, pers. comm.). 1995 also saw the fishery ending due to bad weather conditions (M. Ruth, pers. comm.). In April 1996, when the fishery tried to start again, no living Spisula solida were found (M. Ruth, pers. comm.). The suction dredging gear was subsequently modified to access Spisula solida living at greater depths.

Because the clams are fished commercially, at least some of the population will be removed and, therefore, intolerance has been assessed as intermediate. Even if the clams are not caught, the dredging will at the very least leave the clams more susceptible to predation. Recoverability will probably be high.

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

No specific information was found concerning the effects of the extraction of other species on Spisula solida. Any extraction of other species using fishing gear that penetrates the seabed such as scallop dredging is likely to cause forced disturbances (as above) or remove species as bycatch. Therefore intolerance has been assessed as intermediate with a high recoverability.