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1.
With increasing awareness of the use of the coastal zone, it is necessary to understand the potential environmental effects of aquaculture practices. This is especially important when non-native species, which may be competitively superior to native species, are cultivated. A 5-year experiment was established to study the environmental effects of the various stages of Manila clam. Tapes philippinarum Adams & Reeve, cultivation, from seeding, through on-growing, harvesting and post-harvesting. The aim was to monitor changes in biological and physical variables in the sediment which may be useful in formulating an environmental management strategy for the cultivation of this species. This paper describes the biological and physical changes that occur in the sediment during the early phase of clam cultivation. We compared the changes in netted plots (with and without clams) and unnetted control areas, 6 months before and after laying the clams. The clams were planted in April 1992 under netting at a density of 500 m-2 (0.16 kg m-2), and in 6 months, had increased their weight to 3.2 kg m-2 but decreased their number to 410 m-2. A significant, but small increase in organic content (net only plots, 3.37%; control plots 2.42%) and in phaeopigment (netted plots, 8.6 mg m-2; control, 5.6 mg m-2) of the sediment in the netted plots relative to the control areas were seen. Short-term sedimentation rates on the netted plots were up to four times higher than in the control areas. The netting also encouraged the settlement of Enteromorpha sp. which, in turn, attracted Littorina littorea to feed on these plots. The infaunal community in the control areas was similar to that in samples 12 months earlier and continued to be dominated by the predatory polychaete Nephtys hombergii. Netted plots (with and without clams) had a greater abundance of deposit feeding polychaetes. particularly Ampharete acutifrons and Pygospio elegans, which were the dominant fauna in these plots. Within the clam treatments, the density of clams had a negative effect on the abundance of cirratulids, although mean abundance was generally greater than in the control areas. There were few physical changes to the experimental area after 6 months. The most important effect appears to be the increased sedimentation rate over plots with netting, which has led to an increase in productivity of those areas. 相似文献
2.
Rita Constantino Miguel B. Gaspar Fábio Pereira Susana Carvalho João Cúrdia Domitília Matias Carlos C. Monteiro 《水产资源保护:海洋与淡水生态系统》2009,19(5):542-553
- 1. Razor clams are found in different habitats ranging from sheltered systems (e.g. lagoons and estuaries) to open coasts. They are distributed worldwide and comprise a small number of species of high economic value. Depending on the specific habitat and species exploited, different mechanical and hand‐harvesting techniques are employed. While the environmental effects resulting from mechanized methods have been described by several authors, the impacts caused by traditional hand‐harvesting methods remain unknown. Therefore, a study was undertaken in Ria Formosa lagoon (South of Portugal) addressing the environmental effects resulting from harvesting Solen marginatus with salt.
- 2. No significant impact on the sediment was found; the main effect was an increase in salinity after covering the area with salt, which decreased rapidly with the flood tide and after a few hours had returned to pre‐harvesting levels.
- 3. No effects on benthic communities were observed, with similar fluctuation patterns recorded in control and experimental areas, the observed differences being attributed to the natural variability of benthic populations.
- 4. Based on the results obtained in the present study, a razor clam fishery using salt in intertidal areas can be considered environmentally ‘friendly’.
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Michel J Kaiser Jeremy S Collie Stephen J Hall Simon Jennings & Ian R Poiner 《Fish and Fisheries》2002,3(2):114-136
Fishing affects the seabed habitat worldwide on the continental shelf. These impacts are patchily distributed according to the spatial and temporal variation in fishing effort that results from fishers' behaviour. As a consequence, the frequency and intensity of fishing disturbance varies among different habitat types. Different fishing methodologies vary in the degree to which they affect the seabed. Structurally complex habitats (e.g. seagrass meadows, biogenic reefs) and those that are relatively undisturbed by natural perturbations (e.g. deep‐water mud substrata) are more adversely affected by fishing than unconsolidated sediment habitats that occur in shallow coastal waters. These habitats also have the longest recovery trajectories in terms of the recolonization of the habitat by the associated fauna. Comparative studies of areas of the seabed that have experienced different levels of fishing activity demonstrate that chronic fishing disturbance leads to the removal of high‐biomass species that are composed mostly of emergent seabed organisms. Contrary to the belief of fishers that fishing enhances seabed production and generates food for target fish species, productivity is actually lowered as fishing intensity increases and high‐biomass species are removed from the benthic habitat. These organisms also increase the topographic complexity of the seabed which has been shown to provide shelter for juvenile fishes, reducing their vulnerability to predation. Conversely, scavengers and small‐bodied organisms, such as polychaete worms, dominate heavily fished areas. Major changes in habitat can lead to changes in the composition of the resident fish fauna. Fishing has indirect effects on habitat through the removal of predators that control bio‐engineering organisms such as algal‐grazing urchins. Fishing gear resuspend the upper layers of sedimentary seabed habitats and hence remobilize contaminants and fine particulate matter into the water column. The ecological significance of these fishing effects has not yet been determined but could have implications for eutrophication and biogeochemical cycling. Simulation results suggest that the effects of low levels of trawling disturbance will be similar to those of natural bioturbators. In contrast, high levels of trawling disturbance cause sediment systems to become unstable due to large carbon fluxes between oxic and anoxic carbon compartments. In low energy habitats, intensive trawling disturbance may destabilize benthic system chemical fluxes, which has the potential to propagate more widely through the marine ecosystem. Management regimes that aim to incorporate both fisheries and habitat conservation objectives can be achieved through the appropriate use of a number of approaches, including total and partial exclusion of towed bottom fishing gears, and seasonal and rotational closure techniques. However, the inappropriate use of closed areas may displace fishing activities into habitats that are more vulnerable to disturbance than those currently trawled by fishers. In many cases, the behaviour of fishers constrains the extent of the impact of their fishing activities. Management actions that force them to redistribute their effort may be more damaging in the longer term. 相似文献
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Potential clam farming areas containing clean sandy sediment accessible at low tide are limited in New South Wales, Australia. The availability of farming infrastructure such as oyster racks and floating devices along with the prevalence of sediment other than clean sand prompted the assessment of farming methods for Tapes dorsatus (Lamarck) and Katelysia rhytiphora (Lamy) and sediment preferences for T. dorsatus. This study indicates that both clam species, when contained in baskets, grow (whole weight and shell length increase) significantly faster (P < 0.05) in the sediment followed by in floating baskets, on racks or on the sediment in that order. However, the survival of K. rhytiphora was significantly higher (P < 0.05) on the rack (99%) than in the other situations (72–85%). A similar trend was observed for T. dorsatus but it was not significant (P > 0.05). Tapes dorsatus held in a sandy-shell substrate grew faster than those cultured in substrates of only shell, sand or mud at the same intertidal site, Survival rates over 6 months were high in all these translocated sediments and ranged from 95 to 100%. Tapes dorsatus grown in the same sediments in a nearby tidally-exchanged subtidal pond reached market size (～ 38 mm) after 6 months of grow-out and were over twice as heavy (whole weight 10.0–11.9 g) as those grown inter-tidally (whole weight 3.7–5.7 g). 相似文献
6.
Marijn Rabaut Ulrike Braeckman Frederik Hendrickx Magda Vincx Steven Degraer 《Fisheries Research》2008,90(1-3):209-216
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. 相似文献
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Shannon L. Meseck Rene Mercaldo‐Allen Julie M. Rose Paul Clark Catherine Kuropat Jose J. Pereira Ronald Goldberg 《Journal of the World Aquaculture Society》2014,45(3):301-311
A before‐after‐control‐impact (BACI) experiment was conducted to examine the effects of hydraulic clam dredging on sediment biogeochemistry of a leased shellfish bed of Mercenaria mercenaria, northern quahog, over the course of an entire growing season. Six study plots (0.67 ha each), three dredged and three not dredged, off of Milford, Connecticut, in Long Island Sound, were sampled from May to October 2009 for porewater fluxes of total ammonia, oxygen, and hydrogen. Particulate samples were also analyzed for grain size, total nitrogen, total carbon, total sulfur, and organic carbon. Statistical analysis indicated no significant difference between dredged and not dredged sites. Grain size and oxygen flux explained 22% of the variation in the total benthic species assemblages; grain size and either total carbon or organic nitrogen explained 18% of the variation in molluscan abundance. Our study demonstrates that one‐time hydraulic shellfish harvesting had minor effects on the sediment chemistry of a leased clam bed. 相似文献
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1. The impact of land-claim on the intertidal areas of the Forth estuary, eastern Scotland is described. It is shown that in recent times almost 50% of the intertidal area has been destroyed for a variety of purposes, including agriculture, harbours and industrial development. 2. The loss of infaunal invertebrate biomass and production from the intertidal habitat has been calculated for each part of the estuary, and by summation for the whole estuary. The loss is discussed in relation to the total biomass and production, both intertidally and subtidally, of the estuary. It is shown that proportionately more biomass and production may have been lost than area. 3. The impact of land-claim on estuarine fish is calculated. Land-claim has removed 24% of the natural fish habitats in the Forth estuary, and thereby removed 40% of their food supply. 4. The impact of habitat loss on birds was observed for one area where observations continued throughout a period of land-claim. For individual bird species at Torry Bay, land-claim had consequences ranging from neutral to substantially negative. Significant declines were found for overwintering populations of dunlin and bar-tailed godwit. Comparisons of pre- and post-land-claim bird feeding usage of this area, showed that the impact of land-claim on local bird populations differed between species. The large scale loss of habitat on the Forth seems likely to have reduced the size of some shorebird populations which overwinter on the estuary. 5. It is concluded that when considering the impact of land-claim on estuaries that, as found in some previous studies, a simple consideration of area lost may be inadequate to describe the effects of land-claim, and the consequences for animals living within the estuary may differ considerably amongst themselves and from area to area. 相似文献
9.
Guido Leurs Brian O. Nieuwenhuis Thije J. Zuidewind Nadia Hijner Han Olff Laura L. Govers 《Fish and Fisheries》2023,24(3):407-426
Intertidal habitats (i.e. marine habitats that are (partially) exposed during low tide) have traditionally been studied from a shorebird-centred perspective. We show that these habitats are accessible and important to marine predators such as elasmobranchs (i.e. sharks and rays). Our synthesis shows that at least 43 shark and 45 ray species, of which 54.5% are currently threatened, use intertidal habitats. Elasmobranchs use intertidal habitats mostly for feeding and as refugia, but also for parturition and thermoregulation. However, the motivation of intertidal habitat use remains unclear due to limitations to observe elasmobranch behaviour in these dynamic habitats. We argue that elasmobranch predators can play an important role in intertidal food webs by feeding on shared resources during high tide (i.e. ‘high-tide predators’), which are accessible and also consumed by terrestrial or avian predators during low tide (i.e. ‘low-tide predators’). In addition, elasmobranchs are able to change the bio-geomorphology of intertidal habitats by increasing habitat heterogeneity due to feeding activities and may also alter resource availability for other consumers. We discuss how the ecological role of elasmobranchs in intertidal habitats is being affected by the continued overexploitation of these species, and conversely, how the global loss of intertidal areas poses an additional threat to an already vulnerable taxonomic group. We conclude that studies on intertidal ecology should include both low-tide (e.g. shorebirds) and high-tide (e.g. elasmobranchs) predatory guilds and their ecological interactions. The global loss of elasmobranch predatory species and intertidal habitat provides additional compelling arguments for the conservation of these areas. 相似文献
10.
《水生生物资源》1999,12(1):45-56
Manila clam (Tapes philippinarum) culture and sediment interactions were tested by comparing two rearing areas, including an oceanic (‘Le-Ferret’) and a more estuarine (‘Les-Jacquets’) sites in the bay of Arcachon (France). The growth of a calibrated clam population (10-mm spat) was monitored in these two areas with a concomitant sediment-water interface survey over a 1.5-year period. Two sites per area, including control and rearing plots, were sampled on a monthly basis. The potential clam farming impacts by bioturbation and interactions were examined at three sediment depths: 0–1, 1–2 and 2–10 cm. Moreover, the main hydrobiological parameters were measured on a weekly basis to establish a relationship between these parameters and sediment-water interface characteristics. The existence of a gradient between the three depths was revealed for most of the parameters examined, with the exception of silt and organic carbon levels, and this regardless of the area examined. Clam growth showed a rate improvement in the oceanic area, which is characterized by a lower silt content. The clam effect was minimal and the activity identified at the ‘Ferret’ site was in fact due to the presence of a net which acted as a particle trap. No significant relationship was established between water column parameters and those of the sediment-water interface at the two geographical sites examined. These results demonstrate that clam rearing had only a limited effect on the environmental sediment parameters (i.e. water percentage, and phaeopigments and silt levels) from a spatio-temporal point of view. Therefore, a return to environmental conditions existing before the implementation of clam fanning is likely to occur upon cessation of this activity. 相似文献
11.
Brett R. Dumbauld Jennifer L. Ruesink Steven S. Rumrill 《Aquaculture (Amsterdam, Netherlands)》2009,290(3-4):196-223
Aquaculture is viewed as a potential mechanism to meet the growing demand for seafood around the world. The future of bivalve shellfish aquaculture in the U.S. hinges on sustainable practices on the part of industry and a more consistent regulatory regime. Bivalve shellfish aquaculture is a recent practice relative to its history in other countries, beginning in the late 1800s along the U.S. West Coast where it is now well established with farm raised product utilizing land-based hatcheries and grow-out directly in numerous estuaries. Bivalve shellfish aquaculture can be viewed as a disturbance which modifies the estuarine system in three ways: 1) changes in material processes — bivalves process food and produce wastes; 2) addition of physical structure — aquaculture introduces the cultured organisms and in some cases a physical anchoring structure; and 3) pulse disturbances like harvest and bed maintenance disturb sediments, remove species in addition to the cultured organisms themselves, and change resource or habitat availability. In U.S. West Coast estuaries, water column and sediment nutrient concentrations are relatively high and influenced by large tidal exchange and proximity to deeper nearshore ocean waters where upwelling controls production during summer months. Bivalves are unlikely to influence material processes except at local bed scales in these systems, although estuary-wide effects could appear as the fraction of cultured area rises or in poorly flushed bays. Bivalve culture clearly modifies estuarine habitat at local community and at landscape scales and effects are most often evaluated against existing structured habitat in the form of submerged aquatic vegetation. Individual activities act as pulse disturbances and the recovery of eelgrass (Zostera marina) to pre-disturbance levels is variable (< 2 to > 5 years). The extent of disturbance depends on the aquaculture practice and the distribution of eelgrass reflects a balance of space competition, pulse disturbance and recovery, and is therefore at dynamic equilibrium on aquaculture beds. Structure provided by aquaculture appears functionally similar to eelgrass for small benthic infauna and mobile epibenthic fauna while use of aquaculture as habitat by larger more mobile invertebrates and fish depends on mobility and varies with life-history stage and taxon being evaluated. Scale seems a very important management consideration and further research at estuarine landscape scales, especially for habitat use by important invertebrates and fish, may prove useful in designing and implementing best management practices. Though local and short term effects from aquaculture are clearly evident in U.S. West Coast estuaries, bivalve aquaculture does not remove area from the estuary or degrade water quality like other anthropogenic influences, and thus has not been implicated in shifts to alternate states or reduced adaptive capacity of the larger ecological system. 相似文献
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1. The case is made for recognition of the marine bivalve Limaria hians as a reef‐forming species, which plays a key architectural role in certain benthic communities around the United Kingdom and Ireland. 2. This species uses byssal threads to construct nests that can coalesce to form reefs that cover hectares of seabed, contain multiple conspecifics and bind sediment. In so doing, L. hians modifies physical, chemical and biological processes at the sediment–water interface. 3. Such nests support a high diversity of associated organisms in coarse‐grade sediments (19 species of algae and 265 species of invertebrates from six discrete nests in Loch Fyne are reported on), although the biological interactions between species both inside and outside this assemblage (e.g. predatory cod) are unknown. 4. Being insubstantial, labyrinthine structures situated on the sediment surface, Limaria nests are sensitive to mechanical impacts, such as those caused by moorings, hydraulic dredging for infaunal bivalves and scallop dredging. 5. At appropriate sites, the status of L. hians can contribute a useful indication of disturbance on coarse‐grade sediments. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
13.
1. Human trampling has been shown to be detrimental to the survival of fauna of terrestrial habitats and on rocky coastal areas. However, its effects on saltmarsh benthic infauna were not known. 2. The abundance of macro-benthic fauna at five locations on a transect across a footpath on the emergent marsh and on the tidalflat at Lindisfarne NNR were sampled during the summer 1994 and winter 1995. 3. The abundances of dominant taxa increased in summer in the intensely trampled path on the unvegetated tidalflat leading to a change in the community structure. These changes were not apparent when the trampling intensity was lower in winter. 4. The abundances of dominant taxa at a less intensively trampled site in the vegetated emergent marsh did not change in either season. 5. The susceptibility of the saltmarsh infauna to human trampling depends on the intensity of trampling disturbance and on the nature of the habitat. The possible effects of human trampling on the macrofauna in these intertidal habitats are discussed with reference to coastal management. © 1996 by John Wiley & Sons, Ltd. 相似文献
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1. Human trampling was investigated in order to quantify the ‘recreational carrying capacity’ of two rocky intertidal areas in northeast England. 2. Estimation of ‘recreational carrying capacity’ was made by subjecting experimental plots in pristine areas of shore to different intensities of sustained trampling. The algal community was subsequently monitored for 16 months. 3. Changes in algal community composition occurred at both sites at all intensities. Compositional changes were rapid (1–2 months) and timing was dependent on both trampling intensity and site. 4. Trampling resulted in consistently reduced abundances of some species, for example fucoids, Phymatolithon lenormandii and turf species. 5. Open space was present in greater quantities in trampled than untrampled plots. In the summer months, this was subsequently colonized primarily by Enteromorpha spp. 6. ‘Recreational carrying capacity’ is being exceeded in some areas at both sites in the summer months. Possible management strategies are discussed in the light of these experimental results. copy 1996 by John Wiley & Sons, Ltd. 相似文献
16.
A study of the environmental effects associated with the trestle cultivation of Pacific oysters, Crassostrea gigas Thunberg, was conducted at a commercial cultivation site in the River Exe estuary, Devon, England. Small, but significant, changes were detected in the macrofaunal community sampled beneath oyster trestles compared with that found in adjacent uncultivated areas. These changes were associated with an increase in organic and silt composition and a reduction in the depth of the oxygenated layer of the sediment beneath the trestles. Water velocity was decreased by the presence of the trestles which probably led to the increase in sedimentation rate observed beneath them. Although biological and physical changes were observed, they were relatively minor compared with the extreme environmental changes associated with the suspended culture techniques used for other bivalve species and fishes. However, other studies suggest that the environmental effects associated with oyster cultivation become more severe in areas of large-scale (hectares) cultivation. 相似文献
17.
1. The effect of habitat fragmentation was investigated in two adjacent, yet separate, intertidal Zostera marina beds in the Salcombe Estuary, Devon, UK. The seagrass bed on the west bank comprised a continuous meadow of ca. 2.3 ha, whilst the bed on the east bank of the estuary was fragmented into patches of 6–9 m2. 2. Three 10 cm diameter core samples for infaunal macroinvertebrates were taken from three stations within each bed. No significant difference was found in univariate community parameters between beds, or in measured seagrass parameters. However, multivariate analysis revealed a significant difference in community composition, due mainly to small changes in species abundance rather than differences in the species present. 3. The species contributing most to the dissimilarity between the two communities were polychaetes generally associated with unvegetated habitats (e.g. Magelona mirabilis) and found to be more common in the fragmented bed. 4. A significant difference in median grain size and sorting coefficient was recorded between the two beds, and median grain size was found to be the variable best explaining multivariate community patterns. 5. The results of the study provide evidence for the effects of habitat fragmentation on the communities associated with seagrass beds, habitats which are of high conservation importance. As the infaunal community is perhaps intuitively the component least likely to be affected by fragmentation at the scale observed, the significant difference in community composition recorded has consequences for more sensitive and high‐profile parts of the biota (e.g. fish), and thus for the conservation of seagrass habitats and their associated communities. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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This work reports on the effects of intertidal planting heights upon the growth and survival of the northern quahog, Mereenaria mercenaria (L.) and the Atlantic sod clam, Spisula solidissima (Dillwyn), in the castal waters of Georgia. Quahogs (N = 100 per cage) at 19.5 mm in shell length were planted in replicate cages (N = 3) placed at the spring (SLW), mean (MLW), one (+1), two (+2), and three (+3) hours above mean low water mark. Surf clams (N = 200 per cage) at 41.5 mm in shell length were placed in replicate cages (N = 3) deployed, as above, in all sites except +3. Quahogs grown at the SLW mark after 15 months were significantly larger than clams planted at other tidal heights. Quahogs planted at the MLW mark were significantly greater in shell length than those planted at the +3, +2, and +1 marks. Clams at the upper three sites were not significantly different in size. An inverse relationship between clam growth and intertidal planting height was evident among surf clams. Surf clams grown at the SLW mark for six months were signplificmtly larger than those at the MLW mark which were larger than those grown at the +1 above MLW mark. No significant differences in quahog survival were detected between intertidal planting sites. There was no significant difference in surf clam survival between SLW (77.5%) and MLW (61%) marks, but there was significantly lower survival at the +1 mark (15%) and no survival at the +2 mark. 相似文献
20.
Eve Galimany Jennifer H. Alix Mark S. Dixon Gary H. Wikfors 《Aquaculture International》2013,21(5):1009-1015
The ribbed mussel (Geukensia demissa, Dillwyn 1817) is a dominant benthic filter-feeder in salt marshes along the North American Atlantic Coast. It has been proposed that the cultivation and harvest of ribbed mussels could be used to bioremediate the eutrophication of coastal waters. To accomplish this, mussels would be grown in suspension culture underwater, which is different than this species’ natural, intertidal habitat in which they are exposed to a tidal regime of submersion and emersion. To assess possible effects of constant submersion upon the feeding behavior of G. demissa, we quantified filter-feeding activities of ribbed mussels collected from either an intertidal location or a permanently submerged (2 months) population in the same embayment. Filtration measurements to determine clearance rates were conducted in aquaria containing ultra-filtered seawater with cultured phytoplankton. Results show that mussels taken from the intertidal population had significantly higher filtration than the submerged population initially, but after 3 days of submersion in the aquaria, this difference disappeared. Moreover, all experimental G. demissa had higher clearance rates during natural low tide than during natural high tide. These results indicate a potential for ribbed mussels to be grown in suspension culture for nutrient bioextraction purposes. 相似文献