Progress 10/01/99 to 09/30/05
Outputs
Maine landings have been variable for the last 100 years. Two earlier periods of low harvests in the late 1920s, and mid 1960s were followed by a substantial recovery of the fishery. Soft-shell landings have dramatically declined in Maine over the past 25 years due to low productivity of clam flats in Eastern Maine. Eastern Maine clam flats are subjected to high tidal water exchange ratios dispersing larvae offshore, heavy predation by green crab populations not limited by winterkill and high fishing pressure on diminished stocks. Digging/fishing of previously protected breeding stocks due mitigation of pollution closures also decreases clam sets. Reestablishment of depleted clam stocks depends on pedivelgers successfully setting on mudflats after moving with the tides and currents for two weeks or longer depending on water temperature. The large tidal amplitude and resulting high flushing and water turnover rates in bays and estuaries in the Gulf of Maine could move
clam larvae offshore away from the intertidal clam flats where they normally set. Tides increase moving northerly and easterly up the Maine Coast with the largest tides in eastern most Maine where landings remain low. Offshore dispersal of larvae would be increased further at a low summer/fall water temperatures along the eastern Maine coast since development of larvae to the pediveliger stage is delayed and the pelagic dispersal period until setting is lengthened. However, clam populations have successfully reestablished themselves in the past despite this large tidal amplitude. Small clam sets are not a new problem and may be depend on sporadic events such as favorable winds occurring when pediveliger larvae are located in surface waters and can be pushed shoreward as has been observed for the megalopae larvae of blue crabs in the Delaware Bay. However, 100,000 acres of pollution closures in Maine with their previously undisturbed clam populations have been opened to harvesting
since 1993 reducing adult breeding stocks and potentially negatively impacting already low larval recruitment onto the flats. Fishing effort corresponds with clam catch. There is limited opportunity for employment in eastern Maine and entry into the clam fishery requires minimal investment, allowing clam populations to be quickly exploited unless fishing effort is controlled. The recent increase in clam stocks and landings in eastern Maine since 1998 has been matched by an increase in the number of clam licenses issued Decreasing fishing effort by issuing fewer licenses or closing flats could be useful in reestablishing and maintaining shellfish stocks. The extension of the range of the green crab up the coast of New England has negatively impacted clam populations particularly in areas such as eastern Maine where winterkill of crabs is reduced by warmer winter water temperatures. Between 1880 and the present, the sea surface temperature in the Gulf of Maine increased by .643oC.
Global warming and rising water temperatures in the Gulf of Maine could result in larger green crab populations and heavier predation on shellfish stocks.
Impacts
Management practices which have been utilized have not been successful at reestablishing the presently diminished clam populations in E Maine. Opening flats to harvesting previously closed due to pollution may temporarily increase harvests while decreasing breeding populations, making reestablishment of diminished clam populations difficult. Future conservation efforts should be directed at increasing recruitment, and decreasing predation and fishing effort. To enhance recruitment, clam breeding preserves where harvesting is prohibited could be established. Clam mariculture could be used to produce both steamers and sets to repopulate local flats while the individuals on the stocked flats grow to market size. Entire bays could be managed to produce harvests from both cultivated and wild clams while producing sufficient larvae for a natural set. Rotational digging of flats should be evaluated to maintain breeding populations while allowing adults to grow without
breakage and reburial from premature digging. Areas which are dug in the rotation could be repopulated with a natural set or juvenile seed from areas with high density sets. A green crab sampling program should be reimplemented to describe and measure the effect of crab populations on clam stocks. Crab sampling could be conducted by municipalities as part of their State mandated survey of local clam flats. If crab populations are determined to be one of the factors limiting reestablishment of clam stocks, techniques for crab control should be developed and implemented.
Publications
- W.R. Congleton, Jr., B.R. Pearce. M.R. Parker, and Brian F. Beal. 1999. Mariculture Siting: A GIS description of intertidal areas. Ecological Modelling 116, no. 1: 63-75.
- Vassiliev, T., W.R. Congleton, Jr., B.F. Beal and S. Fegley, 1999. An investigation of Mya arenaria (soft-shell clam) recruitment in Maine. Journal of Shellfish Research, 18, no.1, pp. 311-312.
- Tracy Nason and William R. Congleton, Jr. 1999. Digging for Better Data. GPS World Showcase Vol 10. No. 8: p. 18.
- Vassiliev, T., W.R. Congleton, B. Beal and S. Fegley. 2000. Larval recruitment of Mya arenaria (soft-shell clam) in Eastern and Southern Maine. Journal of Shellfish Research, 19, no. 1: pp. 626-627.
- David Cousens, Bill Adler, Bob Bayer, and Bill Congleton. December, 2001. Lobster Population Assessment: Moving Towards a More Realistic Model. Fisherman's Voice, p. 13.
- W. R. Congleton, Jr., B. R. Pearce, and M. R. Parker. 2002. Growth and dispersal studies of Mya arenaria using a numerical flow model. Journal of Shellfish Research, 21, no 1: p. 398.
- Prince, D.L., R. Bayer, Christina Congleton, S. Colby. D. LaVine, D. Volmuth, K. Brooks, M. K. Berry, W. Congleton, and J. Vetelino. 2002. A rapid method for assessing stress in the American Lobster using a hand held glucometer. Journal of Shellfish Research, 21, no 1: p. 437.
- W.R. Congleton, Jr, and B.R. Pearce. 2003. Growth of Mya arenaria in intertidal areas. Coastal Engineering Today. Gainesville, FL.
- W.R. Congleton, Jr., B.R. Pearce. M.R. Parker, and R.C. Causey. 2003. Mariculture Siting: Tidal currents and growth of Mya arenaria. Journal of Shellfish Research, 22, no. 1: 75-84.
- J.Jacques, C. Gillman, R.C. Bayer and W.R. Congleton, Jr. Green Crab, Carcinus Maenas (L.), susceptibility to mortality at low water temperature, and offshore movement in winter. Maine Biological and Medical Sciences Symposium 2004, MDI Biological Laboratory, Salisbury Cove, ME. Congleton, W.R., Jr., T. Vassiliev, R.C. Bayer and B.R. Pearce. 2005. A survey of trends in Maine soft-shell clam landings. National Shellfisheries Association Program and Abstracts of the 97th annual meeting. p. 21.
- Bayer, R.C., W.R. Congleton, R. Brasslett, B.R. Pearce and D. Cowan. 2005. Magnetic resonance (MR) and computed tomography (CT) images of normal and shell diseased lobsters. National Shellfisheries Association Program and Abstracts of the 97th annual meeting. P. 14.
- Vassiliev, T., R. Bayer, W. Congleton, R. Bushway, and J. Vetelino. 2005. Heavy metal concentrations in lobster (Homerus americanus). 2005. National Shellfisheries Association Program and Abstracts of the 97th annual meeting. pp. 54-55.
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Progress 10/01/03 to 09/30/04
Outputs
The soft-shell clam, Mya arenaria (L. 1758), is the bivalve fishery with highest landed value in Maine. Landings have been extremely variable over the last century with present landings a quarter or less of their historical highs. Decreased Maine landings are primarily due to decreased harvests in Eastern Maine. Maine landings have been variable the last 100 years. Two earlier periods of low harvests in the late 1920s and mid 1960s were followed by a substantial recovery of the fishery. Since low clam harvests have persisted since the mid 1980s, it can be asked if the Maine Coast still provides an environment favorable to reestablishing a robust clam fishery. Different management and conservation practices have not been effective in maintaining or increasing clam harvests in Eastern Maine. Reestablishment of depleted clam stocks depends on pedivelgers successfully setting on mudflats after moving with the tides and currents for weeks. The large tidal amplitude and
resulting high flushing and water turnover rates in bays and estuaries in the Gulf of Maine could move clam larvae offshore away from the intertidal clam flats where they normally set. Tides increase moving northerly and easterly up the Maine Coast with the largest tides in eastern most Maine where landings remain low. Offshore loss of larvae would be increased further at a low Summer/Fall water temperatures along the E Maine Coast since development of larvae to the pediveliger stage is delayed and the pelagic dispersion period lengthened. The 100,000 acres of pollution closures in Maine with their previously undisturbed clam populations have been opened to harvesting since 1993 further reducing adult breeding stocks and potentially negatively impacting already low larval recruitment. Fishing effort has increased slightly, but efficiency/catch has been limited by the hand harvesting methods utilized. Fishing effort corresponds with clam catch. There is limited opportunity for
employment in Eastern Maine and entry into the clam fishery is easy with minimal investment, allowing clam populations to be quickly exploited. The recent increase in clam stocks and landings in Eastern Maine since 1998 has been matched by an increase in the number of clam licenses issued. Decreasing fishing effort by issuing fewer licenses or closing flats could be useful in reestablishing and maintaining shellfish stocks. The extension of the range of the green crab up the coast of New England has negatively impacted clam populations particularly in areas where winterkill of crabs is limited by warmer winter water temperatures (such as E Maine). Warmer winter waters in the Eastern Gulf of Maine have only infrequently caused sufficient heavy winter mortality to check the growth of green crab populations. Global warming and rising water temperatures could result in larger crab populations and heavier predation on shellfish stocks. Future conservation efforts should be directed at
increasing recruitment, and decreasing predation and fishing effort. In addition, clam mariculture could be used to increase larval recruitment to the wild fishery.
Impacts
Management practices which have been utilized have not been successful at reestablishing the presently diminished clam populations in E Maine. To enhance recruitment, clam breeding preserves where harvesting is prohibited could be established. Clam farms have already been demonstrated in several locations in Maine using seed from the Beals Island Regional Hatchery. Clam mariculture could be used to produce both steamers and sets to repopulate local flats while the individuals on the stocked flats grow to market size. Entire bays could be managed to produce harvests from both cultivated and wild clams while producing sufficient larvae for a natural set. Rotational digging of flats should be evaluated to maintain breeding populations while allowing adults to grow without breakage and reburial from premature digging. Areas which are dug in the rotation could be repopulated with a natural set or juvenile seed from areas with high density sets. Solutions such as these
should be considered before the clam fishery experiences the type of decline seen in some of the other fisheries in the Gulf of Maine. A green crab sampling program should be reimplemented to describe and measure the effect of crab populations on clam stocks. Crab sampling could be conducted by municipalities as part of their State mandated survey of local clam flats. If crab populations are determined to be one of the factors limiting reestablishment of clam stocks, techniques for crab control should be developed and implemented.
Publications
- J. Jacques, C. Gillman, R.C. Bayer and W.R. Congleton, Jr. Green Crab, Carcinus Maenas (L.), susceptibility to mortality at low water temperature, and offshore movement in winter. 2004. Maine Biological and Medical Sciences Symposium 2004, MDI Biological Laboratory, Salisbury Cove, ME.
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Progress 10/01/02 to 09/30/03
Outputs
A numerical model for describing flows in intertidal, estuarine and nearshore areas was developed. Significant findings 1. The effect of tidal currents on clam growth was determined in situ. Faster tidal currents resulted in 22-24% greater shell growth. 2. Field data was collected on recruitment of clam larvae onto Maine mudflats. Core samples from mudflats were collected from Eastern and Southern Maine in late fall and winter for two years, sieved and juvenile clams (1.8-6.0 mm) from the set of the preceding summer counted. Densities of juveniles averaged 16.9 / square meter from 120 samples from E Maine and 204.5/ square m in Southwestern ME. Mya larval settlement was also measured by placing spat bags filled with monofilament line in locations in E and S Maine. The Scarborough River in S Maine had significantly (P<.001) more Mya per bag than Mason Bay in E Maine. In S Maine where there was a significant set in the spat bags, more spat were collected in the interior
of the estuary rather than outside the mouth suggesting there is a tendency for larvae to remain in the bays where they are spawned. The results of both of these sampling techniques suggest that the recent declines in clam harvests in E Maine may be at least partially due to poor larval recruitment. 3. Field observations suggest and analysis of trends in nearshore water temperatures suggest that predation is also having a major impact on declines in clam harvests.
Impacts
Management strategies should be adopted to maintain a sufficient breeding population in each bay to repopulate the local flats. This objective could be accomplished by a combination of regulated fishing and mariculture. Clam growout sites are composed of breeding individuals up to the time that they harvested 3 to 5 years of age. If the problem in increasing local clam populations is the small number of larvae retained in the area where they are spawned, clam growout sites could be located to enhance recruitment by increasing the size of the breeding population in a bay. Clam mariculture would be used to produce both marketable clams and larvae to help repopulate the wild fishery in a bay. Clam flat management strategies could be developed and evaluated to increase breeding populations and decrease variability in annual digger harvests through a combination of harvesting both cultivated and wild clams. Such a plans could increase digger harvests and decrease the
annual functions in yields by: a. Maintaining an adequate breeding population in each area; b. Closing flats long enough for the individuals to reach market size; c. Decreasing digger reliance on the irregularity of natural sets by establishing a series of clam plots, one of which could be harvested annually. Differences in growth rates on clam flats within each area and need to thin and transplant dense set in specific localities would necessitate fine tuning this plan to each locality. However, these recommendations depend on identifying management areas sharing a common larvae resource.
Publications
- Vassiliev, T., W.R. Congleton, Jr., B.F. Beal and S. Fegley. 1999. An investigation of Mya arenaria (soft-shell clam) recruitment in Maine. Journal of Shellfish Research, 18, no.1, pp. 311-312.
- Vassiliev, T., W.R. Congleton, B. Beal and S. Fegley. 2000. Larval recruitment of Mya arenaria (soft-shell clam) in Eastern and Southern Maine. Journal of Shellfish Research, 19, no. 1: pp. 626-627.
- W.R. Congleton, Jr., B.R. Pearce. M.R. Parker, and Brian F. Beal. 1999. Mariculture Siting: A GIS description of intertidal areas. Ecological Modelling 116, no. 1: 63-75.
- W.R. Congleton, Jr., B.R. Pearce. M.R. Parker, and R.C. Causey. 2003. Mariculture Siting-Tidal currents and growth of Mya arenaria. Journal of Shellfish Research, 22, no. 1: 75-84.
- Tracy Nason and William R. Congleton, Jr. 1999. Digging for Better Data. GPS World Showcase Vol 10. No. 8: p. 18
- David Cousens, Bill Adler, Bob Bayer, and Bill Congleton. December, 2001. Lobster Population Assessment: Moving Towards a More Realistic Model. Fisherman's Voice, p. 13.
- W.R. Congleton, Jr, and B.R. Pearce. 2003. Growth of Mya arenaria in intertidal areas. Coastal Engineering Today sponsored by John Hopkins University. Gainesville, FL.
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Progress 10/01/01 to 09/30/02
Outputs
The immediate objective is to determine the effect of tidal flushing, length of larval period, coastal geology and larval behavior on opportunity for clam pediveligers to set on intertidal flats in the locality where they were spawned. Procedures-- 1. Coverages of the Maine Coast were obtained from the Maine State Office of GIS. 2. Grids of intertidal depths were created for display in raster format in the GIS and for input into the numerical model to predict tidally driven currents. 3. An explicit numerical model (Blumberg and Mellor-the Princeton Ocean Model) is being adapted to describe bays with intertidal mudflats with clam larvae dispersed and tracked as moved by tidal currents 4. The dependent or response variable, relative opportunity to set, will be the proportion of LaGrangian elements (larvae) present at model initialization which are identified as "stuck" or having set on grid cells identified as clam flats during the last two weeks of the run. Relative
opportunity to set is the proportion of clam larvae which remain over clam flats in the bay they were spawned after they develop to the stage where they are capable of establishing themselves on the clam flats. 5. Simulation runs to determine effect of the physical environment in the Gulf of Maine on the dispersal of clam larvae: a. Tidal ranges: 2.4 m of southwestern ME; 2.8 m of south-central ME; 4 m typical of north-central ME. b. Dispersion periods: 4 weeks in 11 degree C water typical of Eastern ME; 3 weeks in 16 degree C water typical of Southern ME.
Impacts
If the problem in increasing local clam populations is the small number of larvae retained in the area where they are spawned, clam growout sites could be located to enhance recruitment by increasing the size of the breeding population in a bay. Clam mariculture would be used to produce both marketable clams and larvae to help repopulate the wild fishery in a bay. Clam flat management strategies could be developed and evaluated to increase breeding populations and decrease variability in annual digger harvests through a combination of harvesting both cultivated and wild clams.
Publications
- W. R. Congleton, Jr., B. R. Pearce, and M. R. Parker. 2002. Growth and dispersal studies of Mya arenaria using a numerical flow model. Journal of Shellfish Research, 21, no 1: p. 398.
- Prince, D.L., R. Bayer, Christina Congleton, S. Colby. D. LaVine, D. Volmuth, K. Brooks, M. K. Berry, W. Congleton, and J. Vetelino. 2002. A rapid method for assessing stress in the American Lobster using a hand held glucometer. Journal of Shellfish Research, 21, no 1: p. 437.
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Progress 10/01/00 to 09/30/01
Outputs
Current velocities averaged over the flood tide were estimated by a numerical flow model and by clod cards for locations in an Eastern Maine bay and were compared to the annual shell increment of clams collected at the same locations. Statistical models including initial shell size, year of sample, high-low current category estimated by clod cards or the numerical model and interactions explained 57-58% of the variability in growth increment after a difference transformation. High current simulated growth although the effect on growth increment was less than that of year or initial size. The adjusted least squares mean for the growth increment at the sites with low flow as identified by clod cards that averaged 4.35+.37 cm/s was 9.56+.247 mm, and low flow that averaged 2.99+.43 cm/s using the numerical model was 9.51+.274 mm. High flow sites averaging 5.86+.62 cm/s using clod cards had estimated growth increments of 11.90+.323 mm and high sites averaging 5.84+.46 cm/s
using the numerical model had estimated growth increments of 11.70+.33 mm.
Impacts
In aquaculture site selection, either time series estimates of water velocity from numerical models or estimates of average water velocity from clod cards can be used to predict shellfish growth. Estimating currents either by field placement of clod cards or use of a numerical model to describe flows throughout an entire bay is expensive and time consuming. However, the incorporation of current estimates from a numerical model in a GIS (Geographical Information System) would make the information readily retrievable for use in aquaculture siting as well as other applications.
Publications
- Vassiliev, T., W.R. Congleton, B. Beal and S. Fegley. 2000. Larval recruitment of Mya arenaria (soft-shell clam) in Eastern and Southern Maine. 92nd Annual Meeting National Shellfisheries Assn.
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Progress 10/01/99 to 09/30/00
Outputs
Recruitment success or failure would affect clam harvests. Core samples were collected from mudflats in both Southern and Eastern Maine and examined for the number of juvenile recruits settling and surviving to 2 mm. Cumberland County in Southern Maine had significantly more recruits (343.4 m-2 ) than Washington County in Eastern Maine (31.3 m-2 , N=72, P<.0001) in all three years (Vassiliev et al., 1999). The small number of juvenile recruits in Eastern Maine suggests that variation in annual harvests may be due to settlement failure of clam larvae. Spat bags were used to sample pediveliger larvae in the water column to determine. Spat bags are constructed from nylon mesh filled with gill netting and suspended in the water column providing an artificial environment for the clam larvae to set which is protected from most predators. Sample collectors composed of two spat bags, one buoyed 1 m from the surface and the other 1 m from the bottom, were deployed in Southern
Maine (in the Scarborough River Estuary and in Saco Bay near the Scarborough River) and Eastern Maine (in Mason Bay, and in Englishman Bay near Mason Bay). The spat bags were retrieved monthly, sieved through 750 micron mesh, and the number of juveniles (>750 microns) counted (Vassiliev et al, 2000). As expected, setting occurred earlier in Southern Maine due to the higher water temperature with Southern Maine showing statistically more recruits in July (729.9+187.9 recruits/bag) and August (876.8+ 187.9 recruits/bag) than Northern Maine ( < 1 recruit/bag) with recruitment not starting in Northern Maine until October (7 recruits/bag in both Southern and Northern Maine in October). There was no statistical difference in the number of juveniles recovered from the bags near the surface and the bags near the bottom. To investigate both the seasonal pattern and local distribution in regions with high numbers of larvae, the data from Southern Maine were analyzed separately. The number of
larvae collected by the spat bags inside the Scarbourough estuary (653.6+ 108.0) were significantly greater than those collected outside the estuary in Saco Bay (129.3+ 103.8 ). This result indicates a tendency for clam larvae to remain in the bay where they are spawned. Physics based numerical modeling techniques are commonly used to describe the passive distribution of materials in marine environments and have been adapted to describe larval settlement. Since passive dispersion by currents is primarily responsible for the dispersion of clam larvae, a physics based numerical flow model is being used in the present study to describe the retention of clam larvae in bays along the coast of Maine. The theory evaluated is that wild clam populations in the Gulf of Maine are more prone to recruitment failure of larvae onto intertidal flats due to the large tidal amplitude and resulting high flushing rates moving larvae offshore during a larval period which is extended in cool coastal waters
particularly in Eastern Maine which has more open coastal geology.
Impacts
If the problem in increasing local clam populations is the small number of larvae retained in the area where they are spawned, clam growout sites could be located to enhance recruitment by increasing the size of the breeding population in a bay. Clam mariculture would be used to produce both marketable clams and larvae to help repopulate the wild fishery in a bay.
Publications
- W.R. Congleton, Jr., B.R. Pearce. M.R. Parker, and Brian F. Beal. 1999. Mariculture Siting: A GIS description of intertidal areas. Ecological Modelling 116, no. 1: 63-75.
- Nason, T. and W. R. Congleton, Jr. 1999. Digging for Better Data. GPS World Showcase Vol 10. No. 8: p. 18
- Parker, M.R., B.F. Beal, W.R. Congleton, Jr., B.R. Pearce, and L. Morin. 1999. Utilization of GIS and GPS for shellfish growout site selection. Journal of Shellfish Research, 17, no. 5: 1491-1496.
- Vassiliev, T., W.R. Congleton, Jr., B.F. Beal and S. Fegley, 1999. An investigation of Mya arenaria (soft-shell clam) recruitment in Maine. Journal of Shellfish Research, 18, no.1, pp. 311-312.
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Progress 10/01/94 to 09/30/98
Outputs
Populations of Mya arenaria were sampled from an intertidal mudflat within Mason Bay in eastern Maine. Plaster of Paris hemispheres (clod cards) measured relative water motion at each of fifteem sampling sites. The correlation between the 15 estimates of current velocity from a numerical model and clod cards was .96 (p<0.01). Current velocity estimated by either the numerical model or clod cards was related to clam growth increment in all GLM models with R2 ranging from 0.01442 to 0.1640. The effect of water velocity on the annual growth increment ranged from 0.104 to 0.158 mm per cm/sec increase in velocity. The relationship between bivalve growth and the erosion of clod cards could be used in site evaluation for bivalve growout. For estimation of relative water velocities and growth rates at the same elevation within a bay or cove, percentage weight loss deployed clod cards could be used. However, for descriptions of current magnitude and direction over large areas,
numerical modelling techniques would seem more appropriate. Such models may be used in conjunction with at Geographical Information System (GIS) to evaluate potential sites for the cultivation of shellfish. A description of an intertidal bay in eastern Maine was developed in a GIS, incorporating infrared aerial photographs, and maps of bottom types, topography, and bathymetry. Data layers include elevations from nautical charts and carrier-phase GPS measurements made in the bay. Current vectors were layered over other coverages. The data in the GIS, including estimates from the numerical flow model, can be queried to identify and display locations that would optimize growth of infaunal and epifaunal species. A sample query identified sites for shellfish growout aquaculture.
Impacts
(N/A)
Publications
- Pearce, B.R., W.R. Congleton, M. Parker, and B.F. Beal. 1997. Describing intertidal habitats for aquacultural siting. Symposium on Marine Finfish and Shellfish Aquculture, Marine Stock Enhancement, and Open-Ocean Engineering. Durham, NH.
- Congleton, W.R., and B.R. Pearce. 1997. A C++ implementation of an individual/landscape model. Ecological Modeling 103:1-17.
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Progress 10/01/96 to 09/30/97
Outputs
Mya arenaria was sampled from an intertidal mudflat in eastern Maine. Plaster of Paris hemispheres measured relative water motion at 15 sites. Correlation between estimates of current velocity from a numerical model and clod cards was .96. Current velocity estimated by numerical model or clod cards was related to clam growth increment in all GLM models with R2 ranging from 0.01442 to 0.1640. Effect of water velocity on annual growth increment ranged from 0.104 to 0.158 mm per cm/sec increase in velocity. Relationship between bivalve growth and erosion of clod cards could be used in site evaluation for bivalve growout. For estimation of relative water velocities and growth rates at same elevation within a bay, % weight loss of deployed clod cards could be used. For descriptions of current magnitude and direction over large areas, numerical modelling techniques would be more appropriate. Such models may be used in conjunction with a GIS to evaluate potential sites for
cultivation of shellfish. A description of an intertidal bay in eastern Maine was developed in a GIS incorporating infrared aerial photographs and maps of bottom types, topography and bathymetry. Data layers include elevations from nautical charts and carrier-phase GPS measurements made in the bay. Current vectors were layered over other coverages. Data in GIS including estimates from numerical flow model can be queried to identify and display locations that would optimize growth of infaunal and epifaunal species.
Impacts
(N/A)
Publications
- Pearce, B.R., W.R. Congleton, Jr., M. Parker and B.F. Beal. 1997. Describing Intertidal Habitats for Aquacultural Siting. Symposium on Marine Finfish and Shellfish Aquaculture, Marine Stock Enhancement and Open Ocean Engineering. Durham, N.H. p. 28.
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Progress 10/01/95 to 09/30/96
Outputs
Trimble GeoExplorer hand-held receivers were used to take GPS measurements on anintertidal mudflat in Mason Bay in eastern Maines. Foot accuracy in vertical plane was possible by averaging 4 10-min. measurements using phase processing with a 93 km baseline or setting up a local base station with a .64 km baseline to the receiver and taking a single 10-min. measurement. MapInfo GIS was used to combine and analyze data from subtidal elevation measurements from NOAA charts, intertidal GPS elevation measurements, and USGS aerial infrared photographs. Elevation measurements were organized into a triangular irregular network and used to estimate elevations for a grid covering the bay. Current velocities are being estimated using Princeton Ocean Model, modified to describe flooding and drying of grid cells in the bay during simulation of a tide. Other layers show bottom types, bathymetry, and symbols for sample sites tagged with data that can overlay infrared photographs
taken at high and low tide. Data from numerical flow model is used to estimate a time-averaged current velocity for each grid cell, including sites involved in a field trial measuring growth of juvenile clams seeded on the flat in spring 1996. The GLM regression equation from the analysis of this field trial will predict clam growth as determined by spatial variables included in the GIS. This equation could then be used to predict and map growth rates for potential seeding sites for juvenile shellfish throughout the bay.
Impacts
(N/A)
Publications
- Congleton, W.R., and L.M. Farrar. 1996. An object-oriented database with ancestry for controlling inbreeding. AI Applications 10(2): 51-61.
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Progress 10/01/94 to 09/30/95
Outputs
Mason Bay in Eastern Maine was established as the study site for a numerical hydrodynamic model. Subtidal bathmetry data has been taken from the NOAA nautical chart of Englishman's Bay. Contour elevation data for the intertidal mudflats is being collected with GPS in collaboration with Louie Morin (UM, Forest Resources). Benchmarks have been identified at each end of the bay and differential GPS has been utilized to collect mudflat surface elevation data at low tide. More accurate estimates are to be generated by establishing a local base station at one of the benchmarks using the adjustments to GPS positions at the benchmark location to correct the data simultaneously taken by a roving unit in the bay. This intertidal elevation data is being combined with the NOAA subtidal data in MAPINFO (a GIS). The combined xyz file will be input into FASTTABS (a pre-and post-processor for two-dimensional hydrodynamic models) which will generate a TIN (triangulated irregular
network) connecting the depth measurements. Software has been written to generate a depth grid and flag file for the TIN which is required input into the Princeton Oceanographic Model (POM). Current velocity data output from POM will be related to growth rates and natural sets of juvenile Mya arenaria. This data is being collected in collaboration with Dr. Brian Beal, University of Maine at Machias.
Impacts
(N/A)
Publications
- NO PUBLICATIONS REPORTED THIS PERIOD.
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Progress 10/01/93 to 09/30/94
Outputs
A hydrodynamic numerical model is to be developed to estimate planktonic availability through time for infaunal filter feeders in coastal embayments. Model initialization will use bathymetric grid data output from GIS ArcInfo software run on PC. Data on intertidal depths may require techniques for processing infrared aerial photographs of intertidal areas. The gridded data and tidal schedules will be input into the NOAA MECCA program developed to study tidal, wind and density driven currents in bays. Explicit forward in time, centered in space techniques using equations for conservation of mass and momentum will be used to estimate time-dependent vertically averaged tidal velocity vectors for the grid. These tidal vectors will be input into an object oriented program with the vectors as data for the cells. Additional cell data will include infaunal filter feeders. A planktonic input will be estimated for the boundary of the model and depleted by the filter feeders as
the water moves over the grid. Planktonic availability will be estimated and displayed as the program executes or summarized and displayed as a new layer on the ArcInfo display of the bay. Platonic availability should influence site suitability for culturing shellfish.
Impacts
(N/A)
Publications
- CONGLETON JR., W.R., AND M.P. COLCA. 1994. Correlations between measured performance and lifetime income in simulated dairy herds. Agricultural Systems 44: 91-104.
- CONGLETON JR., W.R.,ET AL. 1993. Application of object-oriented programming and remote sensing to assess intertidal sites for aquaculture. Bulletin Aquaculture Assoc. Canada 93-4: 115-116.
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Progress 10/01/92 to 09/30/93
Outputs
A grid can be used to describe a clam flat constructed of individual plots. Bothplots and the grid are viewed as objects described in classes in C++. Each plot has data for eleven size classes of clams, mortality rates from crabs, predatory snails and unspecified mortality by clam size class. Each plot is further described by its tidal elevation, mean particle diameter and boundary and surface components of the water column. These plots are linked together in a grid by a C++ object oriented simulator. Member functions in class plot of growth and attrition update the clams size distribution. Presently, there is insufficient data to describe Mya growth as influenced by: season or temperature, clam density, and density of potentially competing species. In the plot attrition member function, data is lacking to describe the interaction between predation and season, and predation and tidal location of plot. These estimates are required to predict yield from seeding a
specific site with juvenile clams.
Impacts
(N/A)
Publications
- CONGLETON, W.R., JR., B.F. BEAL, B.R. PEARCE, AND R.C. BAYER. 1993. Application of object oriented programming and remote sensing to assess intertidal sites and aquaculture. Program and Abstracts Aquaculture. Canada 93:32.
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Progress 10/01/91 to 09/30/92
Outputs
An object oriented model of a clam flat utilizing an object oriented simulator is being constructed. Model objects will be plots on the clam flat for which descriptive data have been collected. The C++ simulator developed by Congleton (unpublished) will be utilized. The object oriented capability of class inheritance allows the description of a base class (i.e. plot) to be utilized in a more specific child class which describes the clam flat plot. The simulator organizes the plots into a grind object (or class) which describes the entire clam flat. The simulation clock has also been coded in a class allowing combined continuous-discrete simulation with Runge-Kutta integration of difference equations, and discrete events described in a dynamically allocated queue ranked on time of the event. Events in the simulation can involve any object in the model by casting a pointer in the event class to point to an object of the appropriate type. Plot objects in the grind are
linked to adjacent plots in four directions by memory pointers which can be utilized to describe flows or exchanges between grid cells. Although the plot objects in the present application utilizes four pointers for simulation in two dimensions, plots with two additional pointers (plot *up, *down) could be utilized to create three dimensional objects composed of stacks of the grid objects for future applications (i.e. a water column).
Impacts
(N/A)
Publications
- NO PUBLICATIONS REPORTED THIS PERIOD.
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