Predator and scavenger aggregation to discarded by-catch from dredge fisheries: importance of damage level

Predator and scavenger aggregation to simulated discards from a scallop dredge fishery was investigated in the north Irish Sea using an in situ underwater video to determine differences in the response to varying levels of discard damage. The rate and magnitude of scavenger and predator aggregation was assessed using three different types of bait, undamaged, lightly damaged and highly damaged individuals of the great scallop Pecten maximus. In each treatment scallops were agitated for 40 minutes in seawater to simulate the dredging process, then subjected to the appropriate damage level before being tethered loosely in front of the video camera. The density of predators and scavengers at undamaged scallops was low and equivalent to recorded periods with no bait. Aggregation of a range of predators and scavengers occurred at damaged bait. During the 24 hour period following baiting there was a trend of increasing magnitude of predator abundance with increasing damage level. However, badly damaged scallops were eaten quickly and lightly damaged scallops attracted a higher overall magnitude of predator abundance over a longer 4 day period. Large scale temporal variability in predator aggregation to simulated discarded biota was examined by comparison of results with those of a previous study, at the same site, 4 years previously. The community of predators and scavengers present at the bait was substantially different during the 2 studies. These changes in scavenger community were only partially related to changes in the mean background density of scavenging species.     

Growth and survival of the South African scallop Pecten sulcicostatus in suspended culture

Grow-out studies of the scallop Pecten sulcicostatus, endemic to the South African coast, contribute to an investigation of the suitability of this species for commercial culture. Hatchery-reared juvenile scallops were placed in a suspended culture system at 5 m depth in Saldanha Bay on the west coast of South Africa. Scallops of 78 days old and ranging in size from 4.5 mm to 11.0 mm shell height (mean 6.9 mm), as measured on 2 February 2010, were deployed in Saldanha Bay on 9 February 2010. Subsequent growth was assessed monthly through increments in shell height in relation to changing environmental conditions as determined through continuous measures of temperature and chlorophyll a. Upon termination of the experiment on 15 February 2011, scallops ranged in size from 42.1 mm to 48.7 mm (mean 45.1 mm), representing an increment in shell height of 38.2 mm over one year. The mean growth rate of 0.10 mm day^?1 (mean specific growth rate of 0.0046 day^?1) compares favourably with other commercially cultured species and exceeds previous estimates of growth of naturally occurring populations of P. sulcicostatus. Scallop growth was poorly correlated with either temperature or chlorophyll a concentration, but scallop mortality was closely aligned to the temperature regime of Saldanha Bay, exhibiting high mortalities during mid-summer.     

桑沟湾养殖生态系统浮游植物的粒径结构及浮游生物对栉孔扇贝碳需求的贡献

The biomass and size fraction of phytoplankton in terms of chlorophyll a(Chl a) was measured during four cruises conducted in April, July, October 2013 and January 2014 in mariculture area, the Sanggou Bay, China.Results show that total Chl a levels in the surface seawater of the Sanggou Bay generally range from 0.10 to 20.46μg/L, with an average value of 2.13 μg/L. Nano-phytoplankton was the most important size-fraction and accounted for about 65.1% of total Chl a. In order to evaluate the importance of the "protozoan trophic link" for energy transfer from the microbial loop to filter-feeding feeders, Zhikong scallop Chlamys farreri was then offered a natural planktonic community as potential prey. Results show that scallops obtained carbon source from natural plankton with the rate of 11 033.05 μg/(g·d). Protists(nanoflagellates and ciliates) were the dominant source of carbon retained by scallop(48.78%). The microbial loop provided 58.45% of the carbon source for farmed scallops. These results indicate that the microbial loop represent a valuable trophic resource in mariculture system of the Sanggou Bay.     

Relationships of growth and mortality to enzymatic activity,and the relative mRNA expression of cultured scallops Patinopecten yessoensis in the Yellow Sea,China

The bottom aquaculture of yesso scallop (Patinopecten yessoensis) has developed rapidly in the north of Yellow Sea, China, but not without accompanying productivity problems. We, therefore, conducted field surveys to investigate factors related to growth and mortality rates of bottom-cultured scallops after release. Specifically, we focused on the effects of total antioxidant capacity (TAOC) and three key enzymes involved in antioxidant and metabolic function:glutamic pyruvic transaminase (GPT), lactic dehydrogenase (LDH), and superoxide dismutase (SOD). Across summer and winter, we also measured the relative mRNA expression of GPT and SOD to understand their seasonal variation in the scallops, along with how such variation correlated to growth and mortality. Results show that bottom cultured scallops experienced mass mortality during the first six months post-release. During winter (December), scallops grew more rapidly and suffered less mortality than in summer (August). The observed lower performance probably resulted from less advantageous environmental factors during the summer seasons, such as high temperature and low dissolved oxygen. These environmental stressors enhance protein consumption while decreasing energetic resources in scallops. Furthermore, scallops in summer exhibited high antioxidant levels that probably competed for energy with process integral to growth and survival. These negative factors combined to elevate mortality rates. In conclusion, we provided evidence suggesting correlations between metabolic/antioxidant activity and growth and mortality of bottom-cultured yesso scallops. These correlations implied us an accurate method to estimate the performance of bottom culture system. Suggestions about innovative aquaculture techniques were also discussed in the study. Our results might provide a possible guideline to the improvement of bottom culture techniques for this commercially valuable seafood species.     

Response of Yesso scallop Patinopecten yessoensis to acute temperature challenge: physiological and biochemical parameters

Water temperature is generally considered to be a major factor af fecting the physiological and biochemical activities of marine bivalves. Here, the physiological and biochemical responses of Yesso scallop, Patinopecten yessoensis, to acute water temperature changes in summer were studied. Scallops were transferred directly to a lower temperature( T dec treatment)(from 23°C to 15°C) or to a higher temperature( Ti nc treatment)(from 15°C to 23°C) for 72 h, respectively. Results showed that the oxygen consumption and ammonia-N excretion rates of P. yessoensis decreased signi?cantly in the T dec treatment but increased dramatically at 6 h in the Ti nc treatment( P <0.05). In the T dec treatment, hepatopancreas antioxidant enzyme activities, superoxide dismutase(SOD) and catalase(CAT) activities, increased substantially within 72 h( P <0.05). However, a signi?cant decrease in CAT activity was found at 12 h in the Ti nc treatment( P <0.01).A signi?cant enhancement of acid phosphatase(ACP) activity and malondialdehyde(MDA) content was detected when scallops were acutely exposed to a temperature of 15°C. The levels of Cu/Zn-SOD gene expression in their gills up-regulated signi?cantly in response to acute temperature changes( P <0.01). These data suggest that acute temperature change af fects physiological and biochemical functions, and improve our knowledge of P. yessoensis under conditions of thermal stress.     

DNA damage in the gill cells of the marine scallop Mizuhopecten yessoensis during anoxic stress and aerobic recovery

Anoxia-induced DNA damage in the gill cells of the marine scallop Mizuhopecten yessoensis was assessed with the alkaline comet assay (single-cell gel electrophoresis). The alkaline comet assay method for detecting DNA strand breaks and alkali labile sites in individual cells. DNA damage was determened in the scallops (M. yessoensis) gill cells. The scallops were exposed to air for 8 h showing a clear increase in the levels of DNA damage. After the air exposure, M. yessoensis were re-submersed for a period of 12 h, leading values to return to a pre-aerial exposure level. Control animals were kept immersed during the whole period. The resulting data demonstrate that natural influences, such as oxygen depletion (anoxia) in seawater, can be responsible for the induction of DNA damage. If the scallops were re-immersed in oxic conditions, the anoxically induced breaks were repaired. The main mechanisms influencing the integrity of the DNA structure are discussed in this paper.     

紫扇贝与海湾扇贝种间杂交的研究

为推动中国扇贝养殖业的进一步发展,作者于2008年从秘鲁引进了紫扇贝(Argopecten purpuratus),尝试将紫扇贝与海湾扇贝(Argopecten purpuratus)进行杂交,以期培育出具有优势性状的杂交子代.利用引进的紫扇贝与海湾扇贝进行种间杂交,培育出紫扇贝(雌)×海湾扇贝(雄)杂交扇贝.实验证明紫扇贝的卵子与海湾扇贝的精子可正常受精,受精卵发育正常.杂交扇贝的生长速度在幼虫阶段和成体阶段均快于海湾扇贝.至收获时,杂交贝比海湾扇贝平均壳高、壳长和壳宽分别大27.3%,25.2%和19.3%,体质量增加107.0%,杂种优势明显.     

Application of the biomarker responses in scallop (Chlamys farreri) to assess metals and PAHs pollution in Jiaozhou Bay,China

Scallops (Chlamys farreri) were collected at three sites in the Jiaozhou Bay, China in April and July 2007. The responses of biomarkers were evaluated for assessment of physiological status of scallops and pollution in the areas. Compared with site S1, the activity of aryl hydrocarbon hydroxylase was induced notably (P < 0.05) and glutathione S-transferase activity was inhibited significantly (P < 0.05) in S2 and S3. The levels of DNA alkaline unwinding, DNA protein crosslinks, protein carbonyl and lipid peroxidation were tested and indicated the oxidative stress situation of scallops. There was significant difference of biomarker levels between sampling seasons (P < 0.05), and between digestive gland and gill (P < 0.05). The results provided the reference data for multiple-pollution assessment in the marine environment and indicated that tissue type and seasons affect biomarkers, therefore these factors should be taken into consideration when biomarkers are used for environmental assessment purposes.     

日本蟳捕食栉孔扇贝机制的初步研究

在现场和室内条件下研究了日本蟳(Charybdis japonica)对栉孔扇贝(Chlamys farreri)的捕食机制。现场实验表明,成年日本蟳可以捕食壳高小于5.0 cm的栉孔扇贝,其捕食强度随着水温的升高而增大,而壳高大于5.9 cm的栉孔扇贝则可以免遭日本蟳的捕食;相对于栉孔扇贝,日本蟳更倾向于捕食贻贝;室内实验表明水温低于10℃时,日本蟳对大规格扇贝的捕食作用不明显。相同温度条件下,室内实验日本蟳的捕食强度要低于现场,但其温度系数(Q10)差别不大。在上述实验基础上,本文提出了提高底播栉孔扇贝成活率的方法,即选择大规格的扇贝在水温较低的秋、冬季进行底播,同时添加一部分贻贝作为牺牲诱饵以减少日本蟳对扇贝的捕食。     

高效非损伤性扇贝DN A提取方法的建立及效果评价

本研究建立了一种高效、经济的非损伤性扇贝DNA提取方法,在不影响扇贝个体生存状态的前提下,采用擦拭法和室温裂解相结合的方式在20 min内即可获得个体基因组DNA。以虾夷扇贝(Patinopecten yessoensis)、栉孔扇贝(Chlamys farreri)和海湾扇贝(Argopecten irradians)为实验对象,研究了不同擦拭材料(棉签、滤纸)和不同擦拭部位(外套膜、鳃丝、内脏团)的核酸提取效果,评估了本方法在贝类基因分型领域应用的可行性。研究表明,用棉签、滤纸2种材料擦拭扇贝的鳃丝、内脏团或外套膜组织均能获得主带清晰完整的基因组DNA,且不影响扇贝的存活状态。在3种扇贝中采用棉签擦拭法的DNA得率均高于滤纸法,以这2种方式获得的DNA为模板进行SSR和SNP标记分析,能获得均一稳定的扩增条带,SSR标记分型结果准确可靠。本研究建立了简便、快速进行扇贝基因型分析的非损伤性DNA提取方法,为贝类全基因组选育和珍稀贝类资源的种质保护开发提供了新的技术手段。     

桑沟湾夏、秋季悬浮颗粒物的沉降通量及再悬浮的影响

应用锚式悬挂沉积物捕捉器法,研究了我国北方重要海水养殖区域桑沟湾悬浮颗粒物沉降通量的分布特征,并通过金属Al标记法,同步测定了沉降颗粒物再悬浮比率。结果表明,桑沟湾的底层悬浮颗粒物(SPM)、颗粒有机碳(POC)、颗粒态总氮(PTN)和颗粒态总磷(PTP)平均表观沉降通量分别为1 511.4g/(m2·d)、20.01g/(m2·d)、1.497g/(m2·d)和0.474g/(m2·d),显著高于我国其他近岸海域,但底层沉降颗粒物再悬浮比率平均值高达92.8%,认为在养殖内湾,受再悬浮程度的影响,测得的底层表观沉降通量是中层的2.7倍,秋季明显大于夏季,海带和扇贝养殖区大于牡蛎养殖区。经再悬浮比率校正后的净沉降通量,仍存在着显著的空间和季节变化,但受控因素发生了根本转变;这主要表现为净沉降颗粒物质主要源于生物代谢活动强烈中上层水体,贝类的排泄作用使牡蛎和扇贝养殖区的净沉降通量显著大于海带养殖区,养殖贝类个体增大、排泄量增加使秋季净沉降通量高于夏季。在我国近岸海域,再悬浮作用的影响,会对该区域悬浮颗粒物沉降通量的估算带来巨大误差,因此该作用不容忽视。     

Changes in trophic flow structure of Independence Bay (Peru) over an ENSO cycle

During the strong warm El Niño (EN) that occurred in 1997/98, Independence Bay (14°S, Peru) showed a ca. 10 °C increase in surface temperatures, higher oxygen concentrations, and clearer water due to decreased phytoplankton concentrations. Under these quasi-tropical conditions, many benthic species suffered (e.g. macroalgae, portunid crabs, and polychaetes) while others benefited (e.g. scallop, sea stars, and sea urchins). The most obvious change was the strong recruitment success and subsequent proliferation of the scallop Argopecten purpuratus, whose biomass increased fiftyfold. To understand these changes, steady-state models of the bay ecosystem trophic structure were constructed and compared for a normal upwelling year (1996) and during an EN (1998), and longer-term dynamics (1996–2003) were explored based on time series of catch and biomass using Ecopath with Ecosim (EwE) software. Model inputs were based on surveys and landings data collected by the Instituto del Mar del Perú (IMARPE). Results indicate that while ecosystem size (total throughput) is reduced by 18% during EN, mainly as a result of decreased total primary production, benthic biomass remains largely unchanged despite considerable shifts in the dominant benthic taxa (e.g. scallops replace polychaetes as secondary consumers). Under normal upwelling conditions, predation by snails and crabs utilize the production of their prey almost completely, resulting in more efficient energy flow to higher trophic levels than occurs during EN. However during EN, the proliferation of the scallop A. purpuratus combined with decreased phytoplankton increased the proportion of directly utilized primary production, while exports and flows to detritus are reduced. The simulations suggest that the main cause for the scallop outburst and for the reduction in crab and macroalgae biomass was a direct temperature effect, whereas other changes are partially explained by trophic interactions. The simulations suggest that bottom-up effects largely control the system.     

Contrasting trends in the Northeast United States groundfish and scallop processing industries

In the northeast United States, groundfish landings have declined almost continually since 1983. Fresh groundfish processors have redeployed their marketing capital by substituting other seafood products in place of regional groundfish and expanding into different markets. Meanwhile, northeast U.S. Atlantic sea scallop landings sharply increased starting in 1998, peaked in 2004, remained relatively constant until declining in 2013 and 2014. In order to leverage their favorable access to increased landings, scallop processors invested in development of new products, such as individually quick frozen (IQF) scallops, and invested in marketing activities to attract new customers, including those located in foreign nations. This behavior is consistent with Montgomery and Wernerfelt's theory of diversification in response to excess capacity of firm-specific resources and investments in product development and marketing in firm specific resources. Price and quantity indicators were used to examine the effects of shifting landings and composition of landings on exvessel values. These indicators show that declines in groundfish exvessel values were driven by declining quantities, which is consistent with processors substituting other products rather than biding up exvessel prices. Increases in scallop exvessel values were driven by both increasing prices for all sizes and by increasing quantities for large scallops, which is consistent with investment in marketing for larger scallops.     

Effects of crude oil on the supralittoral meiofauna of a sandy beach

The supralittoral zone of an open sandy beach was dosed with crude oil and changes in the meiofauna monitored. Treatments included weathered and fresh oil on the surface, fresh oil mixed with dispersant on the surface and weathered oil at the water table, all in layers 0·8 cm thick. In all cases the meiofauna was reduced 1 month after dosing but numbers had returned to normal by 5 months except in the site dosed with fresh oil mixed with dispersant. Oil on the surface had greater effects than oil at the water table; fresh oil had a greater effect than weathered oil and fresh oil with dispersant was more toxic than fresh oil alone. Nematodes were least sensitive to the oil and oligochaetes more sensitive, their numbers being correlated with oil concentrations and depth in the substrate. It is concluded that, under all but the heaviest conditions of pollution in their environment, recovery from oil contamination should occur within 5 months in the meiofauna.     

Prey consumption by the juvenile soles, Solea solea and Solea senegalensis, in the Tagus estuary,Portugal

The soles Solea solea and Solea senegalensis are marine flatfish that use coastal and estuarine nursery grounds, which generally present high food availability, refuge from predators and favourable conditions for rapid growth. Two important nursery grounds for these species juveniles have been identified in the Tagus estuary, one in the upper part of the estuary (nursery A) and another in the south bank (nursery B). While S. solea is only present at the uppermost nursery area, S. senegalensis is present at both nurseries. Although they are among the most important predators in these nursery grounds, there are no estimates on their food consumption or on the carrying capacity of the system for soles. The Elliott and Persson [1978. The estimation of daily rates of food consumption for fish. Journal of Animal Ecology 47, 977–993] model was used to estimate food consumption of both species juveniles in both nursery areas, taking into account gastric evacuation rates (previously determined) and 24 h sampling surveys, based on beam-trawl catches carried out every 3 h, in the summer of 1995. Monthly beam trawls were performed to determine sole densities over the summer. Density estimates and daily food consumption values were used to calculate total consumption over the summer period. Sediment samples were taken for the estimation of prey densities and total biomass in the nursery areas. Daily food consumption was lower for S. solea (0.030 g wet weight d⁻¹) than for S. senegalensis (0.075 g wet weight d⁻¹). It was concluded that thermal stress may be an important factor hindering S. solea's food consumption in the warmer months. Total consumption of S. solea over the summer (90 days) was estimated to be 97 kg (wet weight). Solea senegalensis total consumption in nursery A was estimated to be 103 kg, while in nursery B it was 528 kg. Total prey biomass estimated for nursery A was 300 tonnes, while for nursery B it was 58 tonnes. This suggests that food is not a limiting factor for sole in the Tagus estuary. However it was concluded that more in-depth studies into the food consumption of other species and prey availability are needed in order to determine the carrying capacity of this system for sole juveniles.     

Environmental drivers of small scale spatial variation in the reproductive schedule of a commercially important bivalve mollusc

Understanding variability in reproductive schedules is essential to the management of recruitment limited fisheries such as that of Pecten maximus. Small scale (<5 km) variation in gonad condition and the onset of spawning of P. maximus were found among commercial scallop grounds in Isle of Man waters. Environmental and fishing drivers of these spatial patterns were investigated using a generalised additive model. Rate of change in temperature over the month prior to sampling was identified as the short term driver of gonad weight associated with the autumn spawning event. Long term drivers were average annual chlorophyll a concentration, scallop density, stratification index and shell size. The model explained 42.8% of deviance in gonad weight. Within site variation in gonad condition was high, indicating a “bet hedging” reproductive strategy which may decrease the chance of fertilisation especially at low densities. Therefore, areas protected from fishing, where scallop densities can increase may help buffer against reproductive failure. An increase in shell length from 100 mm to 110 mm equated to an increase of approximately 20% in gonad weight. Protecting scallops from fishing mortality until 110 mm (age four) compared to 100 mm (age three) may lead to an overall increase in lifetime reproductive output by a factor of 3.4.     

Cadmium toxicity to three species of estuarine invertebrates

Three species of estuarine invertebrates, Palaemonetes pugio (grass shrimp), Pagurus longicarpus (hermit crab) and Argopecten irradians (bay scallop), were exposed to Cd in flowing seawater at concentrations of 0·06, 0·12, 0·25, 0·5 and 1·0 mg/litre. Incipient LC₅₀ values of 0·53 and 0·07 mg/litre were estimated for bay scallop and hermit crab, respectively. The toxicity curve for grass shrimp had not stabilised, but the incipient LC₅₀ value was estimated to fall within a range of 0·2 to 0·3 mg/litre. Short-term response, as measured by time to 50% mortality at the highest Cd concentration, was 10, 21 and 23 days for the bay scallop, hermit crab and grass shrimp, respectively. Scallop growth was inhibited at all exposure concentrations with a measured 42-day EC₅₀ value of 0·078 mg/litre Cd. Byssal thread detachment precedes death in bay scallops. An EC₅₀ value of 0·54 mg/litre Cd for byssal detachment was measured on day 8 of the bioassay before appreciable mortality. This compared favourably with the incipient LC₅₀ value of 0·53 mg/litre Cd. Cadmium accumulation occurred at all concentrations in bay scallop and grass shrimp.     

Effects of habitat complexity on cannibalism rates in European green crabs (Carcinus maenas Linnaeus, 1758)

The habitat in which predator–prey interactions take place may have a profound influence on the outcome of those interactions. Cannibalism is an intriguing form of predation whereby foraging by predators may contribute to the regulation of their own populations.This is particularly interesting in the case of invasive species, like the widely distributed European green crab (Carcinus maenas). This study explores how habitat complexity influences cannibalism rates in green crab populations of Prince Edward Island, Atlantic Canada. Both laboratory and field experiments were conducted to measure feeding rates by individual adult green crabs on a standard number of smaller conspecifics. In the laboratory, experimental treatments mimicked unstructured to increasingly structured habitats: water, sandy bottom, oyster shells, mussel shells, oyster shells with sandy bottom and mussel shells with sandy bottom. In those trials, adult green crabs consumed several times more juveniles on unstructured habitats than on the most structured ones, with a gradual decrease in predation rates across increasingly complex habitats. Field inclusion experiments used the same approach and were conducted in sandy bottoms, sandy bottoms with a layer of oyster shells and sandy bottoms with a layer of mussel shells. These trials showed similar patterns of decreasing feeding rates across increasingly complex habitats, but differences among treatments were not significant. These results support the idea that complex habitats have the potential to mediate predator–prey interactions, including adult–juvenile cannibalism in green crabs.     

Total oxyradical scavenging capacity and cell membrane stability of haemocytes of the Arctic scallop,Chlamys islandicus,following benzo(a)pyrene exposure

Industrial activities, notably oil and gas industries, are expanding in the Arctic. Most of the biomarkers were developed using temperate organisms living at temperatures above 10 degrees C. Little is known about the biomarker responses of organisms living between -1.88 and 5 degrees C. Therefore, assessment of the toxicity of chemicals to cold-water adapted species is required. In this study, the Arctic scallop, Chlamys islandicus, was selected as a key species for bio-monitoring because of wide distribution in Arctic waters and its commercial value. Test animals, stored in seawater at 2 degrees C, were injected with benzo(a)pyrene (diluted in cod liver oil 5 mg ml(-1)) in the adductor muscle every 24 h for four days giving a final dose of 0, 74 and 90.6 mg kg(-1) wet weight for control, low and high dose, respectively. The biomarkers used were total oxyradical scavenging capacity (TOSC) in the digestive gland and cell membrane stability of haemocytes. TOSC values were significantly reduced (ca. 30%) in exposed groups (P < 0.05), indicating a depletion in oxyradical molecular scavengers. The antioxidant defences appeared to be overwhelmed by the reactive oxygen species as the plasma membranes of haemocytes were destabilised (P < 0.05) probably due to lipid peroxidation. These data indicate that reactive oxygen species (ROS) were produced by Arctic scallops via the metabolisation of benzo(a)pyrene at 2 degrees C.     

Response of excised gill tissue from the New Zealand scallop Pecten novaezelandiae to suspended silt

The role of turbidity in scallop mortality was investigated for two size classes of Pecten novaezelandiae (70 ± 2 mm and 20 ± 1 mm shell height), by using the “crawl” velocity of excised pieces of gill tissue as an indicator of the response to suspended silt. The crawl velocity of 3 × 5 mm pieces of gill tissue was measured in six different silt concentrations (0.025, 0.05, 0.1, 0.2, 0.3. 0.5% silt, by dry weight) and two size classes (< 10 μm and 10–30 um) of silt. Results of the study indicate that juvenile (20 mm shell height) scallops may be less tolerant of suspended silt than larger (70 mm shell height) scallops and that both size classes may be less tolerant of fine (< 10 μm) silt/clay sized particles than coarse (10–30 μm) particles. These conclusions are supported in part by data from the mortality of whole 20 mm scallops exposed to two size classes (< 10 μm and 10–30 μm) and three concentrations (0.05, 0.3, 0.6%, by dry weight) of silt. Increasing concentrations and decreasing particle size of the suspended silt resulted in reduced gill piece crawl velocity and an increase in the mortality rate of the whole scallops. These results suggest controls on human‐induced disturbance of bottom sediments, such as bottom trawling and dredging, may benefit any further scallop bed enhancement programmes by the avoidance of deterioration in water quality and mechanical damage to scallop spat.