Clam Production Research Articles

Integrated modelling in coastal lagoons: Sacca di Goro case study

A coupled 3D hydrodynamic-biogeochemical model was developed and implemented for the Sacca di Goro coastal lagoon. The model considers nutrient and oxygen dynamics in water column and sediments. Among the biological elements, phytoplankton, zooplankton, bacteria, Ulva sp. and commercial shellfish (Tapes philippinarum) were taken into consideration. Nutrients fluxes from the watershed and open sea, as well as atmospheric inputs, heat flux, light intensity and wind shear stress at the water surface constituted the model forcing functions. The comparison of numerical results with available measurement data indicated that the model was able to capture the essential dynamics of the lagoon. This model has also been used to estimate clam productivity and its impacts on water quality and lagoon properties.

External Shape Differences between Sympatric Populations of Commercial Clams Tapes decussatus and T. philippinarum

The actual Italian production of clams is chiefly sustained by the native Tapes decussatus and the fortuitously imported Tapes philippinarum. Both species are commercialized as “Vongola verace”, but the commercial value of T. philippinarum is lower. The discrimination of species by sight is usually difficult and it cannot be done by observation based on shell morphology but only when animals open their valves hence displaying the two siphons. In this study, we propose a new, noninvasive method to discriminate individuals of both species based on the analysis of the external shape of their shells. Accordingly, in sympatric populations at two sites of the Po river outlet, we have chosen individuals (63 for T. decussatus and 57 for T. philippinarum) of comparable commercial size for which a certain genetic discrimination was previously done. Pictures of the left side valve were taken for all specimens. Their profiles were analyzed with the elliptic Fourier analysis. The mean outline for each species was graphically extracted. The coefficients of the harmonic equations were analyzed by multivariate classification (partial least squares discriminant analysis [PLSDA]). Results showed a high percentage of correct classification of individuals of both species (96.6%). Contour analysis reflected the overall shell shape and thus identified morphological aspects that were difficult to recognize and quantify in sight. The high percentage of correct classifications obtained by combining the analysis of elliptic Fourier harmonics with PLSDA demonstrated the feasibility of this method to discriminate species with a high level of resemblance.

Role of Water Temperature in Hard Clam Aquaculture

FA-151, a 9-page illustrated fact sheet by Kerry Weber, Leslie Sturmer, Elise Hoover, and Shirley Baker, describes the effects of water temperature in hard clam production in Florida — how it is measured, how it affects their physiology, signs of temperature stress, and how to manage for water temperature. Includes a glossary and references. Published by the UF Department of Fisheries and Aquatic Sciences, October 2007. FA151/FA151: The Role of Water Temperature in Hard Clam Aquaculture (ufl.edu)

Measures of hydraulic dredge efficiency and razor clam production, two aspects governing sustainability within the Scottish commercial fishery

A study was made of the efficiency of a commercially available hydraulic dredge design in use on the west coast of Scotland and of the annual biomass production of two different razor clam (Ensis spp.) beds within the Clyde Sea area. These two parameters, viz fishing efficiency and population annual production, are fundamentally important to any proper attempt to assess the long term sustainability of a fishery. The hydraulic dredge used in this study was found to have an absolute efficiency of 90.1% when expressed in terms of the collected wet weight biomass, representing the first time that the efficiency of a hydraulic dredge of this nature has been measured rather than simply inferred from track width. This indicates that this dredge design has the potential to remove the majority of a clam population, including undersized immature individuals, within a 45 cm swath in a single tow. Annual production estimates were also made for two separate razor clam beds. One population of Ensis siliqua was located in Irvine Bay and the other two populations (one E. siliqua and one E. arcuatus) occurred in a mixed bed on Hunterston Sands. Each location was sampled quantitatively on a regular basis using the same hydraulic dredge. Dredged areas were measured by SCUBA divers so that the population densities could be calculated for each sampling event. Size-classes within each population were identified from siphonal shell breadth measurements and production estimates were calculated using a size-cohort analysis procedure designed for stocks exhibiting recruitment but that do not have separable age-classes. Production of all three populations was low during the study (1.82–18.08 g AFDW 10 m-2) as were the production/biomass estimates (0.01–0.11). These data indicate that populations of Ensis spp. on the west coast of Scotland are slow-growing and typical of K-selected species. These data highlight the conflicting pressures facing any razor clam fishery: the design of extremely efficient hydraulic gear and the slow-growth of the target species. It is clear that the future commercial exploitation of these species will need very careful management to ensure sustainability and avoid fishery over-depletion.

An integrated modelling approach for the management of clam farming in coastal lagoons

The development of shellfish farming was analyzed with a coupled watershed and 3D biogeochemical model for the Sacca di Goro coastal lagoon (Northern Adriatic Sea, Italy). Sacca di Goro is the second site in Europe for the production of the Manila clam ( Tapes philippinarum). Different scenarios were identified and analyzed, considering clam productivity under different environmental conditions, namely with and without macroalgal blooms. In addition, the influence of climatic variability – dry, average and wet years – was assessed. Model simulations indicated that macroalgal blooms have an important negative impact on clam productivity due to the risk of anoxia and subsequent clam mortality. Furthermore, simulation results evidenced that meteorological conditions also affect clam productivity, especially in a dry year due to a shortage of food supply.

Growth and survival rates of carpet shell clam (Tapes decussatus Linnaeus, 1758) using various culture methods in Sufa (Homa) Lagoon, Izmir, Turkey

The carpet shell clam (Tapes decussatus Linnaeus, 1758) is a candidate species for aquaculture development in Turkish waters. Our study aimed to assess the efficiency of three different methods (i.e., net, box and fenced ground) to maximize clam production. Two different net materials (hard plastic net and polyamide net) were tested in the net method trials. Conducted over 1 year between October 2001 and October 2002, an initial calibrated clam population, characterized by a 26.25±0.035mm shell length and 3.85±0.06g total wet weight was sampled on a monthly basis to carry out the experiments. By the end of the rearing cycle, clams reached 34.13±0.38mm and 9.09±0.27g in shell length and total wet weight, respectively. Significant differences in shell length and total wet weight among culture methods (P<0.05) were reported. Both maximum growth and total wet weight, as well as survival rate (64%) were obtained using the hard plastic net method. Those overall results were likely due to both limited algae accumulation and crab predation when using hard plastic net. Therefore, this method appears the most suitable to develop further larger experimental clam aquaculture trials. Additional studies required to develop clam culture in Turkish waters are discussed.

Modelling phosphorus and suspended particulate matter in Ringkøbing Fjord in order to understand regime shifts

The focus in this work is on the conditions in Ringkøbing Fjord (Denmark), where there have been major regime shifts during the last 30 years. The regime shift in the 1990s is discussed in this paper and concerns reductions in nutrient input from land and changes in salinity. The changes in these abiotic have drastically influenced the structure and functioning of the ecosystem [e.g., in phytoplankton production, water clarity, macrophyte cover and biomass of clams]. This work concerns the modelling and understanding of such changes and the aim is also to consider patterns in variability in the data that may explain the regime shift. The model used is a general, dynamic process-based mass-balance model for total phosphorus (TP) and suspended particulate matter (SPM). The model uses ordinary differential equations (the ecosystem scale). The calculation time is 1 month to reflect seasonal variations. We quantify, e.g., sedimentation, resuspension, diffusion, mixing and retention. The model has previously been tested for coastal areas of different character and shown to predict TP, SPM, Secchi depth, chlorophyll and the oxygen saturation in the deep-water zone very well (within the uncertainty bands of the empirical data). We show that the model, with new calculation routines for macrophytes and clams, also describes the conditions in Ringkøbing Fjord well, which means that the model is a useful general tool for interpretations of changes in coastal ecosystems. The model is simple to apply in practice since all driving variables may be readily accessed from maps or regular monitoring programs.

Integration of consumer-targeted microalgal production with marine fish effluent biofiltration – a strategy for mariculture sustainability

EU regulations recommend effluent treatment and nutrient recycling for aquaculture sustainability, so a study was undertaken to provide base-line data for the integration of commercial fish-farm effluents with the production of microalgae. The project relates to a specific bivalve consumer (Tapes decussatus) and biofiltration. Effluent inorganic nutrient composition was assessed and evaluated as culture media for Phaeodactylum tricornutum, Tetraselmis suecica and Tetraselmis sp. Optimization of the microalgal compartment included studies on preparation of a simple medium, nutrient or dilution rate manipulation and nutrient removal. Cell harvest was increased chiefly by N correction (6-fold for Tetraselmis sp.) and semi-continuous or continuous operation (by a factor of 3 to 11). Nutrient removal efficiency was high for ammonium and nitrite-nitrogen (80–100%), depending on species, nutrient ratio (Si correction for P. tricornutum) and culture regime for nitrate (41–100%) or phosphorus (21–99%). Data obtained under cyclostat cultivation (yields of 1.38 and 0.50×106 P. tricornutum or Tetraselmis sp. cells mL−1 d−1 and nutrient uptake rates of 2.32 mg N L−1 d−1 and 0.96 mg P L−1 d−1) were used to show clam production and simultaneous wastewater treatment possibilities through the proposed fish-microalgae-clam integrated aquaculture system.

Clam farming quality as a management tool: A proposal based on recent studies in Northern Adriatic lagoons

The rapid and extensive spread of the clam Tapes philippinarum in Northern Adriatic lagoons, mostly in the lagoon of Venice (550 kmq), has led to severe exploitation by mainly free fishing, thus breaching the law. To contrast this unsustainable overexploitation, to which the present decreasing clam harvests are at least partly due, the local fishing authority has recently prepared a Master Fishing Plan for clam production, which is at present under way: the free fishing system must be replaced by a licencing system aimed at regulating market supply and mainly at converting more than 1000 fishermen into clam farmers. Moreover, a number of regulations for both vessels and harvesting techniques and management rules, such as daily clam harvests and fishing times, have been established. Although these newly introduced regulations may be regarded as valuable tools for preserving both the lagoon environment and the resource itself, they do not adequately consider protection for consumers. Although the licensed water areas have been evaluated as safe according to Italian law, at present no guarantees certify the quality of the clams harvested from them, due to the fact that the lagoon of Venice has polluted areas from which clams may be collected illegally and recycled to the legal market simply by putting them into the approved licensed areas before harvesting and marketing them. This paper therefore proposes a number of measures to be undertaken within the framework of good farming practices. The aim is to improve product quality by certification procedures in all production phases, and to guarantee the definite origin of farmed clams.

Restoration that targets function as opposed to structure: replacing lost bivalve production and filtration

Abundant suspension-feeding bivalves have a dominant organizing role in shallow aquatic systems by filtering overlying waters, affecting biogeochemical processing, and diverting production from the water column to the benthos. In degraded aquatic systems where bivalve popu- lations have been reduced, successful restoration of ecosystem functions may be achieved by target- ing the revival of bivalve populations. The 'North Cape' oil spill on the coast of Rhode Island (USA) provides an opportunity to demonstrate the feasibility of scaling bivalve restoration to meet quantita- tive goals of enhanced production. After this oil spill, mortalities of bivalves were estimated by impact assessment modeling of acute toxicity, and results were confirmed by comparisons with counts of dead and moribund animals on local beaches. Computation of lost bivalve production included future production expected from affected animals, had they lived out their expected life spans. This calcu- lation of production forgone required a demographic model that combined age-specific mortality with individual growth. Application of this modeling approach to surf clams Spisula solidissima, the species that comprised 97% of the total loss of bivalve production from the spill, illustrates the detailed implementation of scaling restoration to match estimates of losses. We consider the factors known to limit abundance and production of surf clams and other marine bivalves (hard clams, Amer- ican oysters and bay scallops) and review the advantages of hatchery stocking, transplantation, habi- tat restoration, and reduction of fishing pressure in selecting a reliable and efficient restoration action. Age-specific estimates of the scale of population enhancement required to restore production showed that fewer additional animals were needed when larger (older) animals were added, but at the expense of greater grow-out requirements. Relaxation of fishing was most effective for hard clams. Accurate scaling of restoration was most sensitive to mortality rate, and the most efficient restoration involving seeding of small bivalves would be accomplished using surf clams. Monitoring of the restoration option chosen to compensate for the bivalve loss following the 'North Cape' oil spill can serve to test the underlying demographic assumptions and accuracy of the restoration scaling.

A First Generation Stochastic Bioeconomic Analysis of Algal Bloom Control in a Coastal Lagoon (Sacca di Goro, Po River Delta)

Abstract. In this work we have developed a very simple stochastic mathematical model of Ulva spp. growth to quantitatively evaluate the economic costs of algal harvesting and the related benefits in terms of avoided‘economic loss’of clam production due to an effective prevention of algal blooms and the consequent anoxic crises. Algal growth was simulated by means of a discrete time difference equation of Ulva biomass where the finite growth rate depends only upon water temperature. In order to explicitly include environmental variability, a seasonal autoregressive model calibrated on available data was used to simulate water temperature. Different harvesting scenarios were analysed in terms of the number of harvesting vessels employed and the threshold biomass of Ulva at which vessels start to operate. Costs of algal harvesting and disposal, as well as monetary damages resulting from the collapse of clam production as a consequence of algal blooms, were assessed by interviewing the managers of the Clam Fishermen's Union of Goro. A Monte Carlo approach was used to estimate the mean and total statistical distribution of costs and benefits of different harvesting strategies. Our analysis shows that the most cost‐effective management policy is attained with 4–6 vessels operating at low algal density able to harvest as much Ulva as possible with intensive and short interventions at the beginning of the seasonal growth.

今，アサリが危ない 千葉県のアサリ漁業の現状

The annual fisheries production of the manila clam Ruditapes philippinarum in Chiba Prefecture markedly declined to below 20, 000 metric tons (mt) in 1979, after reached 70, 000 mt at its maximum in the late 1960s. The decline was mainly due to the large-scale coastal development, e. g. the reclamation of the shallow tidal areas where the clam fisheries were intensively operated. However, clam fisheries production gradually decreased even after the cessation of a series of reclamations in 1979. In the Kisarazu area, clam production has been maintained between 5, 000 and 6, 000 mt since the late 1970s in spite of a de rease in the occurrence of wild clam seed. This is most probably due to 2, 000 to 3, 000 mt of seed clam transplanted from other areas and/or prefectures. On the contrary, in the northern Chiba area, where clam production relies only upon wild clam stocks without any transplantation, the clam population has been frequently affected by “Aoshio”, a bacterial bloom caused by upwelling of oxygen-deficient seawater, as well as by river floods of muddy freshwater and winter mortality. Despite these problems, the clam fishery in the northern region has continued during recent decades, because the clam stock has recovered rapidly after mass mortality in many cases. However, clam production sharply decreased from ca. 10, 000 mt in the late 1970s to 800 mt in 1999 due to the poor occurrence of wild juvenile clams. Although the causes of accidental mass mortality have been almost fully revealed, the reason for the decrease in wild juvenile clams is still not known.

Impact of Tapes philippinarum farming on nutrient dynamics and benthic respiration in the Sacca di Goro

The introduction of the short-necked clam Tapes philippinarum into the Sacca di Goro has over a short period made this coastal environment one of the top European clam production sites. In recent years, this activity has been seriously impacted due to the appearance in the lagoon of large macroalgal beds and the occurrence of dystrophic events causing anoxia and massive deaths of molluscs in the cultivated areas.

Review of regulations and monitoring of Italian marine aquaculture

Summary Italian aquaculture has peaked at a production of 245 000 t in 1998, mainly due to mussel and clam production. In the case of finfish production, although freshwater fish production is stable, euryhaline fish production is constantly growing, reaching more than 14 000 t in 1998. With regard to the legal framework which regulates aquaculture activity and protects the environment, Law no. 152, which implements ECC Directive 91/271 and ECC Directive 91/676, was promulgated in 1999. This law replaces Law no. 319 of 1976, Law no. 130 of 1992, Law no. 131 of 1992 and other related laws. The final objective to be achieved by these laws, is to be able to describe each water body with ‘good’ water quality status by the end of 2016, but by the end of 2008 each single water body should be rated as having ‘sufficient’ status. There is no legislation regarding food control in Italy. With regard to the use of veterinary chemicals and authorizations for the registration of new drugs, Legislative Act no. 119 of 1992, implementing ECC Directive 81/852, ECC Directive 87/20 and ECC Directive 90/676, Legislative Act no. 66 of 1993, Legislative Act no. 110 of 1995 and Legislative Act no. 47 of 1997 were promulgated in order to control the use of drugs in reared animals, with the primary aim being protection of the health of human consumers.

Determination of the etiological agent of brown ring disease in southwestern Spain

DAO Diseases of Aquatic Organisms Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials DAO 29:181-188 (1997) - doi:10.3354/dao029181 Determination of the etiological agent of brown ring disease in southwestern Spain Castro D, Santamaría JA, Luque A, Martínez-Manzanares E, Borrego JJ Since 1989 the presence of organic brown deposits on the inner surface of the shells of cultured manila clams Tapes philippinarum associated with episodes of high mortality has been recorded on the southern Atlantic coast of Spain. The gross signs observed in diseased clams were identical to those previously described in France as brown ring disease (BRD), caused by strains of Vibrio tapetis sp. nov. This bacterial pathogen has been isolated in several French clam production areas, and recently in BRD-affected clams cultured in Galicia (NW Spain) and Portugal, using bacteriological procedures. However, this methodology has failed to detect the pathogen in microbiological studies carried out in southwestern Spain. In the present study, an immunodetection test, based on the indirect immunofluorescence (IIF) technique, was developed, using polyclonal antisera to V. tapetis whole cells and against outer membrane (OM). This method provided evidence for the presence of the bacterium in all the BRD-affected clams analysed. V. tapetis was also detected by the same method in healthy (i.e. asymptomatic) clams, which indicates its opportunistic character. Brown ring disease · Vibrio tapetis · Immunodetection · Microbiological analyses Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in DAO Vol. 29, No. 3. Publication date: June 19, 1997 Print ISSN:0177-5103; Online ISSN:1616-1580 Copyright © 1997 Inter-Research.

Occupational IgE-mediated sensitization and asthma caused by clam and shrimp

To confirm occupational asthma caused by clam and shrimp in a food company worker, the following investigation was planned in 60 other exposed workers (56 participants). Before the production period of clam and shrimp, a medical and occupational questionnaire was carried out and skin and RAST testing were done with common inhalants and clam, shrimp, crab, and lobster extracts. During the production period, environmental monitoring was performed with personal and general samplers; inhalation testing with methacholine was proposed to subjects with immediate skin reactivity to clam, shrimp, or both. After the production period, all subjects with an immediate skin reaction to clam, shrimp, or both and either a history of rhinoconjunctivitis, asthma, or bronchial hyperresponsiveness were seen by a specialist. Including the index case in whom occupational asthma to clam and shrimp had been confirmed, four (7%) subjects had a history of rhinoconjunctivitis and two (4%) had a history of asthma during the period of clam production, whereas three (5%) subjects had rhinoconjunctivitis and two (4%) had asthma during the shrimp production. Three (5%) subjects had immediate skin reactivity to clam, and nine (16%) subjects to shrimp. Four (7%) subjects had increased specific IgE antibodies (RAST binding ≥3%) to clam and eight (14%) to shrimp. Significant associations were found between immunologic reactivity to clam and shrimp on the one hand and to crab and lobster on the other. Environmental monitoring demonstrated clam and shrimp on the air sampling filters. Occupational asthma caused by clam was confirmed by specific inhalation challenges in one subject in addition to the index case. These two subjects had skin reactivity and increased specific IgE antibodies to clam, shrimp, or both. By including the initial subject, the prevalence of immediate sensitization is 5% to 7% to clam and 14% to 16% to shrimp. Two (4%) subjects had occupational asthma caused by clam, and one (2%) had occupational asthma caused by shrimp.

Occupational IgE-mediated sensitization and asthma caused by clam and shrimp

Background: To confirm occupational asthma caused by clam and shrimp in a food company worker, the following investigation was planned in 60 other exposed workers (56 participants). Methods: Before the production period of clam and shrimp, a medical and occupational questionnaire was carried out and skin and RAST testing were done with common inhalants and clam, shrimp, crab, and lobster extracts. During the production period, environmental monitoring was performed with personal and general samplers; inhalation testing with methacholine was proposed to subjects with immediate skin reactivity to clam, shrimp, or both. After the production period, all subjects with an immediate skin reaction to clam, shrimp, or both and either a history of rhinoconjunctivitis, asthma, or bronchial hyperresponsiveness were seen by a specialist. Results: Including the index case in whom occupational asthma to clam and shrimp had been confirmed, four (7%) subjects had a history of rhinoconjunctivitis and two (4%) had a history of asthma during the period of clam production, whereas three (5%) subjects had rhinoconjunctivitis and two (4%) had asthma during the shrimp production. Three (5%) subjects had immediate skin reactivity to clam, and nine (16%) subjects to shrimp. Four (7%) subjects had increased specific IgE antibodies (RAST binding ≥3%) to clam and eight (14%) to shrimp. Significant associations were found between immunologic reactivity to clam and shrimp on the one hand and to crab and lobster on the other. Environmental monitoring demonstrated clam and shrimp on the air sampling filters. Occupational asthma caused by clam was confirmed by specific inhalation challenges in one subject in addition to the index case. These two subjects had skin reactivity and increased specific IgE antibodies to clam, shrimp, or both. Conclusion: By including the initial subject, the prevalence of immediate sensitization is 5% to 7% to clam and 14% to 16% to shrimp. Two (4%) subjects had occupational asthma caused by clam, and one (2%) had occupational asthma caused by shrimp. (J A LLERGY C LIN I MMUNOL 1995;96:608-17.)

Hatchery production of diploid and triploid clams, Tapes dorsatus (Lamarck 1818): a potential new species for aquaculture

To assess the potential for hatchery production of the venerid clam, Tapes dorsatus, diploid and triploid clams were produced and ongrown until the spat reached 5–8 mm in size. Triploidy percentages at metamorphosis that ranged from 56 to 85% were induced using a 15-min exposure to 1 mg/l cytochalasin B. No differences were observed in the growth rate of sibling diploid and triploid T. dorsatus larvae. Survival of diploid clams to pediveliger stage was however higher. Post-metamorphic growth and survival of diploid and triploid clams remained the same until the clams were removed from the hatchery to outdoor nurseries. Throughout the larval and early spat phases of production, T. dorsatus growth was similar to that reported for the Manila clam, Tapes philippinarum. Based upon its ease of culture, rapid growth and marketability, T. dorsatus are thought to have considerable aquaculture potential.

Substrate Additive Studies for the Development of Hardshell Clam Habitat in Waters of Puget Sound in Washington State: An Analysis of Effects on Recruitment, Growth, and Survival of the Manila Clam, Tapes philippinarum, and on the Species Diversity and Abundance of Existing Benthic Organisms

To meet demands of expanding tribal and recreational hardshell clam fisheries, the Washington State Department of Fish and Wildlife has been developing new hardshell clam habitat. In Oakland Bay, near Shelton, Washington, two artificial substrates were studied to determine the best substrate for use in improving Manila clam (Tapes philippinarum) production. Treatments consisted of a control of natural substrate; a 10 cm layer of nonuniform size gravel ranging from 6 mm to 19 mm in diameter; and a 10 cm layer of a 50∶50 mixture of gravel and crushed oyster shell ranging from 10 mm to 30 mm in diameter. Effects of these substrates on species diversity and relative abundance of existing, benthic organisms were also investigated. Recruitment of Manila clam seed, less than 10 mm shell length, was significantly higher (p<0.05) in the control plots than in the gravel and gravel + shell plots, which showed no significant differences. Recruitment improved in the gravel and gravel + shell plots after a layer of organic debris and fine sediments collected on them. Manila clam survival was significantly higher in gravel and gravel + shell plots compared to control plots. No significant differences in survival were observed between gravel and gravel + shell plots. Manila clam biomass in the gravel and gravel + shell plots was significantly higher than in control plots. Between the gravel and gravel + shell plots there was no significant difference in biomass. Minor differences in species diversity and abundance of existing benthic organisms were observed among treatments. Gammarid amphipods and nemertean worms were enhanced in gravel and gravel + shell plots. Densities of polychaete worms were slightly lower in gravel and gravel + shell plots compared to control plots.

Influence of Intertidal Aquaculture on Benthic Communities in Pacific Northwest Estuaries: Scales of Disturbance

We reviewed the scale and intensity of disturbance, and the response of benthic and epibenthic communities, to intertidal aquaculture activities in Pacific Northwest estuaries. Available data indicate a spectrum of influences on the ability of estuaries to sustain biota unrelated to the cultured species. Certain disturbances, such as adding gravel to mudflats and sandflats to enhance clam production, may subtly impact certain benthic and epibenthic invertebrates without changing the carrying capacity for estuarine-dependent taxa, such as juvenile Pacific salmon (Oncorhynchus spp.). However, habitat shifts might alter the relative suitability for different salmon species. In contrast, acute disturbances that produce large-scale changes in community dominants, such as manipulation of burrowing shrimp or eelgrass with pesticides or mechanical harvesting and manipulation of oyster grounds, strongly influence the carrying capacity for many fish and macroinvertebrates. Ensuring that estuarine ecosystems are sustainable for the breadth of processes and resources requires a comprehensive assessment of both natural and anthropogenic disturbance regimes, landscape influences, and the effects of local management for particular species on other resources.