Fish Finder Marine Shellfish Study


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Fish Finder Marine Shellfish Study

  1. 1. A Shellfish Study for the Proposed Expansion of Fish Finder Marine 3645 Atlantic Brigantine Boulevard, Brigantine, New Jersey December 8th & 9th 2011 Survey Conducted For: Fish Finder Marine Joe & Kim Fumo, Owner(s) 3645 Atlantic Brigantine Boulevard Brigantine, New Jersey 08203 Survey Conducted By: Richard Stockton College of New Jersey’s Coastal Research Center 30 Wilson Avenue Port Republic, NJ. 08241 (609) 652-4245 December 8th & 9th, 2011
  2. 2. Fish Finder 1A Shellfish Study for the Proposed Expansion of Fish Finder Marine 3645 Atlantic Brigantine Boulevard, Brigantine, Atlantic County, New Jersey December 8th & 9th, 2011IntroductionA shellfish study was performed on December 8th & 9th 2011 to determine if Fish FinderMarine’s environmental conditions support a viable shellfish population. The shellfish studywas designed and implemented using the Shellfish Survey Guidelines published by the NewJersey Department of Environmental Protection (NJDEP) as authorized by Jeffrey C. Lockwood,1991 National Marine Fisheries Service, Habitat and Protected Resources Division. Theproposed expansion of Fish Finder Marine involves extending the existing (western) fixed pier toa distance 260 feet from the existing bulkhead. The pier would extend in the south to northdirection and would have 5 finger piers spaced 20 feet apart. The proposed marina is borderedon both sides by existing dock structures. The bay floor slopes from a depth at the bulkhead of -0.5 feet out to a depth of -17.7 feet NGVD 27. The target species are those which fall under theNJAC’s Coastal Zone Management Rules under Shellfish habitat. They include: Hard Clam(Mercenaria mercenaria), Soft Clam (Mya arenaria), Easter Oyster (Crassostrea virginica), BayScallops (Argopecten irradians), and Blue Mussels (Mytilus edulis), all of which are shellfish ofcommercial and biological significance.Methods and MaterialsThe study area was selected by analyzing the area of the proposed marina expansion and evenlydistributing the entire study area into uniform sub-sections (chart 1). The range of water depthswas from -0.5 to -17.7 feet below the National Geodetic Vertical Datum of 1927 shown inCatalano’s USACOE Permit Plan.Using ESRI ArcGIS 9.3.1 a virtual grid was set up in the same approximate position of theproposed dock system with corresponding known locations totaling 24 points (chart 1). Thesepoints within the grid served as the locations for both the juvenile and adult shellfish survey.Using the Leica RTK GPS system 1200, the positions of all the data points for both the juvenileshellfish study and the adult shellfish study were obtained.To conduct the juvenile shellfish study the 24 data point locations stored on the GPS systemwere used as waypoints to locate each sample site (chart 1, table 3). At each location, a singleanchor was set to help stabilize the boat. A Wildco Ponar grab sample; with an area of 0.75 sq.ft., was used to acquire the samples. Replicate grabs were often necessary to obtain a full samplesize. Once a full sample was obtained, the material was sifted through a 5mm sieve andinspected for juvenile shellfish. This process was repeated at each individual location.Additional variables such as sediment type, additional bivalve mollusks, as well as aquaticvegetation were also noted at each site. At each location the abundance per square foot (ft2) andsize distribution (mean and range) were also reported (tables 1 and 2).To conduct the adult shellfish study, the site locations stored on the GPS were again used tonavigate to the pre-established locations (chart 1, table 3). At twelve locations two anchors wereset, one at the bow and one at the stern. The anchor lines were let out equally and incrementallyin 10’ sections. Each 10’ section was raked using a 16” x 3” toothed bull rake at each location
  3. 3. Fish Finder 2until a 30’ transect distance was achieved. At all 24 locations a Wildco Ponar grab sample; withan area of 0.75 sq. ft., was used to acquire samples. Replicate grabs were often necessary toobtain a full sample size. Additional variables such as sediment type, other bivalve mollusks, aswell as aquatic vegetation were also noted at each site. At each location, the abundance per ft2and size distribution (mean and range) was also reported (Tables 1 and 2).ResultsA total of 20 Hard Clams (Mercenaria mercenaria) were found in the study area. The sizefrequency distribution of the clams found revealed that multiple year classes were present at thesite. This indicates that natural recruitment is taking place in the study area (table 1, chart 2).Juvenile ShellfishAs reported above the study area was sampled for juvenile shellfish by utilizing a Wildco PonarGrab Sample with an area of 0.75 sq. ft. Twenty four sites were established and sampledrepresenting the area of the proposed marina expansion. One juvenile Hard Clam (Mercenariamercenaria) was found at location S4 resulting in a density 1.333 clams/sq. ft. at that location Atotal of 18 sq. ft. was sampled producing an overall Hard Clam density of 0.055 clams/sq. ft.across the total surface area. Only one juvenile Hard Clam was collected so the mean size was1.2 cm with a range of 0 (table 1).Adult ShellfishAs reported above the twelve sites were sampled using a 16” x 3” toothed bull rake and all 24sites were sampled using a Wildco Ponar Grab Sample with an area of 0.75 sq.ft.. A total of 19adult Hard Clams (Mercenaria mercenaria) were found in the entire area. Each raked site wasraked a distance of 30’. Clams were found in 11 of the 24 sites. Locations S5 (1.333 clams/sq.ft.), S11 (4 clams/sq. ft.), and S23 (1.333 clams/sq. ft.), have densities which indicate viableshellfish habitat. However, a total of 497.88 square feet was sampled with an overall density of0.038 clams/sq. ft. across the entire area. The mean size of the clams collected was 6.37 cm withan overall range of 4.6 from 4.3 to 8.9 cm (table 1).SedimentologyThe sedimentology of the area consisted of fine sandy black mud, very fine sandy black mud,fine muddy black/grey sand, fine muddy black sand, medium muddy black/grey sand, and blackmud (table 2).Aquatic VegetationThere were 2 major species of aquatic vegetation in the study area, Sea Lettuce (Ulva lactuca),and Agardh’s Red Weed (Agardhiella tenera). At 8 locations Phragmites roots were found,indicating that at one time a marsh existed here. The installation of the bulkhead likely resultedin shoreline retreat as a result of scouring (table 2).Other ShellfishA total of, 3 Rock Crab (Cancer irroratus), 3 Mud Dog Whelk (Nassarius obsoletus), 2 juvenileBlue Crab (Callinectes sapidus), and 1 adult Blue Crab (Callinectes sapidus), were found in theprocess of locating shellfish (table 1).
  4. 4. Fish Finder 3ConclusionThe study area at 3645 Atlantic Brigantine Boulevard, Brigantine, Atlantic County, NJ is thelocation of the proposed expansion of Fish Finder Marine. The area was surveyed by utilizingArcGIS software, GPS equipment, grab sampling techniques, and a clam rake to help isolateshellfish in accordance with the NJAC’s Coastal Zone Management Rules. It states that “ashellfish habitat area is defined as an area which… has a current shellfish density equal to orgreater than 0.20 shellfish per square foot”. Both the juvenile and the adult shellfish study haddensities values (averaged across the total surface area) below the cited threshold. Hard Clam(Mercenaria mercenaria) was the only relevant shellfish species found in the study area. Therewere small areas which did support zones of viable habitat according to the cited densitythreshold. Location S4 yielded 1.333 juvenile Hard Clams per square foot. Location S5 yielded1.333 adult Hard Clams per square foot. Location S11 yielded 4 adult Hard Clams per squarefoot. Location S23 yielded 1.333 Hard Clams per square foot. The juvenile clams (thosesurveyed with the 5mm sieve screen) produced a value averaged across the total surface areasampled by the ponar grab samples (18.0 ft2) at 0.055 clams per square foot. The adultsrecovered in the rake and ponar grab sample produced a value averaged across the total surfacearea of 497.88 square feet yielded 0.038 clams per square foot. These numbers indicate that theclam density within the area delineated for the installation of a marina expansion at Fish FinderMarine does not substantiate a viable Hard Clam habitat.
  5. 5. Fish Finder 4 Water Quality Characteristics for Fish Finder Marine, Brigantine, NJ. Site of the Proposed Marina Expansion Temperature, Salinity, Dissolved Oxygen, Depth, pH, Specific Conductivity, and Turbidity Data for Shellfish HabitatIntroduction:The Richard Stockton Coastal Research Center (CRC) completed a juvenile and adult hard clamstudy for the proposed development of Fish Finder Marine, Brigantine, NJ in December 2011.Twenty four sites were survey for juvenile and adult hard clams. In this study, one juvenile clamswas observed and 19 adult clams were obtained within 497.88 square feet of space raked in theproject area. A water quality assessment was also included in the proposal based on the followvariables: temperature, salinity, dissolved oxygen, depth, pH, specific conductivity, and turbidityfor the water just above the sediment surface.Water Quality at the Site:The CRC complied the data on December 8th & 9th 2011 with a study of the water qualityparameters for the 24 sites subjected to clam raking or grab sampling using a YSI water qualityprobe to obtain the results listed in table 7, below. The table lists the site location using the samedesignations used in the clam study. The dissolved oxygen values are shown as both a percentageof the maximum level in seawater and as milligrams per liter of water. The depth ofmeasurement at the mid-tidal elevation stage the work was done is also listed. The specificconductivity is given as well although the salinity is the most common expression of the saltcontent of the water.Conclusions:The average temperature of 10.92 degrees Celsius is normal for the time of year within the bayenvironment of Atlantic County. The salinity is also within normal ranges for mid-tideconditions behind the barrier island, however, the average value of 28.0 ppt failed to fall withinthe optimal range for the Hard Clam of 26.5 to 27.5 ppt. The dissolved oxygen levels areexcellent with average values of 9.66 mg/L, and 105.80% respectively. The pH value of 7.91 iswithin the normal range for all stages of Hard Clam development. None of the remaining waterquality parameters including depth, specific conductivity (44.32 mS/cm), and turbidity (9.30NTU), would dictate that shellfish could not live in the waters of the proposed development ofFish Finder Marine (see appendix at end).
  6. 6. Fish Finder 5
  7. 7. Fish Finder 6 Chart 2: Length Frequency for Hard Clams Collected During Site Inspection at Fish Finder Marine, Brigantine, NJ. December 8th & 9th 8 7 6 5Frequency 4 3 2 1 0 0-25 25-38 38 51 51-63 63-76 76-102 Data Bin Ranges (mm)
  8. 8. Fish Finder 7 Table 1: Sample Sites Used to Determine the Density of Adult and Juvenile Hard ClamsTransect Juvenile Clams (live) Adult Clams (live) Clams Per Site Other Shellfish Observations Transect Length Grab Sample Area Juvenile Hard Clam Density Adult Hard Clam Density Mean Range S1 - 1 Hard Clam: 8.4 cm 1 - Rocks 30 0.75 - 0.024 8.4 0 1 Adult Hard Clam S2 - 1 Hard Clam: 5.5 cm 1 - 30 0.75 - 0.024 5.5 0 Shell 2 Hard Clam: 7.2 cm, 7.4 2 Adult Hard Clam S3 - 2 - 30 0.75 - 0.05 7.3 0.2 cm Shells, Rocks S4 1 Hard Clam: 1.2 cm - 1 - - - 0.75 1.333 - 1.2 0 Razor Clam Shell, S5 - 1 Hard Clam: 4.8 cm 1 - - 0.75 - 1.333 4.8 0 Gravel in substrate 1 Blue Crab Blue Mussel Shells, S6 - - 0 (Callinectes sapidus ): - 0.75 - - - - Hard Clam Shells 4.2 cm 1 Adult Hard Clam S7 - 1 Hard Clam: 7.1 cm 1 - Shell, 1 Adult Razor 30 0.75 - 0.024 7.1 0 Clam Shell 2 Rock Crabs (Cancer Rocks, Hard Clam 3 Hard Clam: 4.6 cm, 4.3 S8 - 3 irroratus ): 3.7 cm, 4.1 shells, Tube worm 30 0.75 - 0.073 4.6 0.8 cm, 5.1 cm cm casings, Oyster shells 5 Hard Clam: 5.7 cm, 6.3 5.7 - cm, 8.3 cm, 8.0 cm, 5.7 5 - - 30 0.75 - 0.123 6.8 2.6 cm 1 Mud Dog Whelk Blue Mussel Shells, S10 - - 0 - 0.75 - - - - (Nassarius obsoletus) Jingle Clam Shells 3 Hard Clam: 7.4 cm, 4.4 1 Rock Crab (Cancer S11 - 3 Tube worm casings - 0.75 - 4 5.86 3 cm, 5.8 cm irroratus): 3.5 cm 1 Juvenile Blue Crab (Callinectes sapidus): 2.6 Significant amount of S12 - - 0 - 0.75 - - - - cm, 2 Mud Dog Whelk Tube worm casings, (Nassarius obsoletus) S13 - - 0 - - 30 0.75 - - - - Tube worm, Juvenile S14 - - 0 - 30 0.75 - - - - Hard Clam Shells Blue mussel Shells, S15 - 1 Hard Clam: 6.2 cm 1 - tube worm casings, 30 0.75 - 0.024 6.2 0 rocks 1 Tube Worm, Tube S16 - - 0 - Worm Casings, Snail - 0.75 - - - - shells 24 Tube Worms, S17 - - 0 - Crushed Blue Mussel - 0.75 - - - - Shells Crushed Blue Mussel S18 - - 0 - Shells, Snail Shells, - 0.75 - - - - Tube Worm Casings S19 - - 0 - - 30 0.75 - - - - S20 - - 0 - - 30 0.75 - - - - S21 - - 0 - 36 Blue mussel shells 30 0.75 - - - - 24 juvenile clam 1 Blue Crab (Callinectes shells, Hard Clam S22 - - 0 - 0.75 - - - - sapidus): 2.9 cm Shells, Blue Mussel Shells Crushed Blue Mussel S23 - 1 Hard Clam: 8.9 cm 1 - Shells, 12 Juvenile - 0.75 - 1.333 8.9 0 Hard Clam Shells Clam Shells, Crushed S24 - - 0 - Blue Mussel Shells, 1 - 0.75 - - - - Tape Worm Adult Shellfish Study: 497.88 sq. ft. sampled, 19 adult Hard Clams = 0.038 clams/sq. ft.; Juvenile Shellfish Study: 18 sq. ft. sampled, 1 Juvenile Hard Clams = 0.055 clams/ sq. ft.
  9. 9. Fish Finder 8 Table 2: Aquatic Vegetation & Sediment TypeSite # Species & viability of aquatic vegetation Sediment Agardhs Red Weed (Agardhiella tenera), and Minimal amounts of Sea S1 Fine Muddy Sand, Black/Grey Lettuce (Ulva lactua) Minimal amounts of Sea Lettuce (Ulva lactua ), and Agardhs Red S2 Fine Muddy Sand, Black Weed (Agardhiella tenera ) Agardhs Red Weed (Agardhiella tenera) , and Sea Lettuce (Ulva S3 Medium Muddy Sand, Black/Grey lactua) S4 Phragmities Roots Fine Sandy Mud, Black S5 Phragmities Roots Fine Sandy Mud, Black S6 Phragmities Roots Fine Sandy Mud, Black S7 Ahardhs Red Weed (Agardhiella tenera) , and Phragmities Roots Medium Muddy Sand, Black/Grey S8 Phragmities Roots Very Fine Sandy Mud, Black S9 Sea Lettuce (Ulva lactua) , and Phragmities Roots Very Fine Sandy Mud, Black S10 Phragmities Roots Very Fine Sandy Mud, Black S11 Sea Lettuce (Ulva lactua) Very Fine Sandy Mud, Black S12 no vegitation found Very Fine Sandy Mud, Black S13 no vegitation found Mud, Black Sea Lettuce (Ulva lactua), and Minimal amounts of Agardhs Red Weed S14 Very Fine Sand Mud, Black (Agardhiella tenera) S15 Sea Lettuce (Ulva lactua) Very Fine Sand Mud, Black S16 no vegitation found Very Fine Sandy Mud, Black S17 no vegitation found Very Fine Sandy Mud, Black S18 Phragmities Roots Very Fine Sandy Mud, Black S19 Minimal amounts of Sea Lettuce (Ulva lactua ) Very Fine Sand Mud, Black S20 no vegitation found Very Fine Sand Mud, Black S21 no vegitation found Mud, Black S22 no vegitation found Very Fine Sandy Mud, Black S23 no vegitation found Very Fine Sandy Mud, Black S24 no vegitation found Fine Sandy Mud, Black
  10. 10. Fish Finder 9Table 3: Fish Finder Marine Shellfish Study December 8th & 9th Survey Points Transect Easting Northing S1 522756.72 204668.65 S2 522731.79 204667.87 S3 522706.71 204667.10 S4 522756.20 204683.68 S5 522731.22 204682.92 S6 522706.17 204682.07 S7 522755.80 204698.64 S8 522730.74 204697.95 S9 522705.79 204697.06 S10 522755.25 204713.77 S11 522730.26 204712.78 S12 522705.27 204712.09 S13 522754.72 204728.62 S14 522729.79 204727.72 S15 522704.86 204727.05 S16 522754.30 204743.53 S17 522729.30 204742.92 S18 522704.30 204742.04 S19 522753.88 204758.60 S20 522728.83 204757.86 S21 522703.78 204757.03 S22 522753.36 204773.60 S23 522728.38 204772.81 S24 522703.36 204772.10
  11. 11. Fish Finder 10 Table 4: Fish Finder Marine Shellfish Study Water Quality Data Specific Temperature Salinity Dissolved Oxygen Dissolved Oxygen Depth ConductivitySite (Celsius) (ppt) (as a %) (mg/L) (feet) pH (mS/cm) Turbidity (NTU) S1 10.89 27.41 111.1 10.07 0.638 7.90 44.21 9.30 S2 11.34 27.55 112.6 10.17 1.490 7.90 44.51 8.90 S3 11.23 27.64 121.5 10.80 1.150 7.86 44.48 8.76 S4 11.24 27.54 102.9 9.45 0.951 7.93 44.05 9.60 S5 11.40 27.55 102.8 9.40 1.468 7.92 44.49 9.55 S6 11.36 27.53 101.0 9.17 1.167 7.93 44.12 9.90 S7 10.80 28.81 103.8 9.32 2.760 7.94 44.74 8.60 S8 10.89 28.77 111.0 10.14 2.993 7.92 44.66 9.20 S9 10.79 28.74 114.6 10.40 3.842 7.75 44.62 9.00S10 10.83 28.57 116.0 10.20 3.813 7.93 44.45 9.80S11 10.77 28.43 97.5 9.08 3.150 7.93 44.31 8.80S12 10.69 28.71 109.8 9.95 4.569 7.88 44.60 10.10S13 10.81 28.46 107.3 9.74 2.701 7.95 44.25 8.20S14 10.76 28.49 104.7 9.51 5.844 7.95 44.33 9.20S15 10.64 28.42 105.1 9.63 3.841 7.94 44.27 8.50S16 10.61 28.28 102.6 9.45 6.261 7.93 44.00 9.10S17 10.56 28.17 102.3 9.42 6.449 7.95 43.89 9.70S18 10.54 28.1 101.5 9.4 2.874 7.94 43.76 10.50S19 11.08 27.41 90.7 8.90 7.801 7.92 44.18 9.10S20 11.07 27.45 102.8 9.41 6.070 7.92 44.78 8.80S21 11.19 27.45 106.4 9.56 2.680 7.92 44.09 9.30S22 10.84 27.49 99.9 9.25 14.800 7.91 44.65 10.10S23 10.93 27.48 109.7 9.97 15.230 7.90 44.23 9.80S24 10.85 27.52 101.7 9.39 8.760 7.91 44.10 9.50Avg 10.92 28.00 105.80 9.66 4.64 7.91 44.32 9.30
  12. 12. Fish Finder 11 References1. J. C. Lockwood, “Shellfish Survey Guidelines”, National Marine Fisheries Service, Habitat and Protected Resources Division, Highlands, N.J., 1991.2. N.J.A.C., “Coastal Zone Management Rules”, 7:7E-3.2, 19-22, (2009).3. R. J. Catalano. PE., “Fish Finder Marine USACOE Permit Application Plan”, (2011).
  13. 13. Fish Finder 12 APPENDIX OF LITERATURE FOUND DISCUSSING HARD CLAM HABITAT PARAMETERSThe References Below Cover Specific Parameters for Mercenaria mercenaria clamsHill, K. (2004). Smithsonian Marine Station at Fort Pierce. Retrieved January 13, 2012, from“In the IRL as in other areas within its range, Mercenaria mercenaria is most abundant in shell-containing soft bottoms. They are also found (in decreasing order of abundance) on sand flats,sand/mud flats and on muddy bottoms (Wells 1957; Pratt 1953). A study by Peterson et al.,(1984) also showed that densities of 0 - 2 year old hard clams in eelgrass (Zostera marina) bedsof North Carolina was more than 5 times the average density of clams in nearby sand flats (9 persquare meter in eelgrass, vs. 1.6 per square meter in nearby sand flats. Further, hard clams fromZostera beds appeared to be somewhat larger, on average, than those from sand flats.Hydrodynamic baffling by seagrasses may be at least partially responsible for the observed result(Peterson et al., 1984). Reduction in currents near the benthos enhances the deposition of finesediments and suspended materials between blades of seagrass, especially near patch edges.Hydrodynamic baffling therefore provides a rich food source for juvenile clams.”Mann, R., Harding, J. M., Southworth, M. J., Wesson, J. A. (2005). Northern Quahog (hard clam) Mercenaria mercenaria abundance and habitat use in Chesepeake Bay. Journal of Shellfisheries Research, 24(2), 509-516.“Clam densities decreased significantly across the four types of substrate with the highestdensities observed in shell substrate followed by sand, mud and anoxic muds in order ofdecreasing occupation (Kruskal Wallis, H = 1,414.27, DF = 3, P < 0.01; Fig. 3). Less than 1% ofall clams collected were from anoxic mud substrates whereas shell, sand, and mud substratescontained 11%, 68% and 21% of clams, respectively. Although shell and sand substratescontained the highest observed densities of hard clams, these substrate types were only present in38% of patent tong samples collected from potential clam habitats.”Mulholland, R. (1984). Habitat Suitability Index Models: Hard Clam. Florida Cooperative Fish and Wildlife Research Unit. FWS/OBS-82/10.77SPECIFIC HABITAT REQUIREMENTS:Embryo, Larva, JuvenilepH. “Calabrese (1972) observed that the successful recruitment of mercenaria requires thatthe pH of estuarine waters not fall below 7.0; he found no significant decrease in the number ofclam embryos developing normally within the pH range of 7.0-8.75, but that number was greatlyreduced at pH 9.0. Survival of clam larvae was normal at pH 6.25-8.75, but the range for normal
  14. 14. Fish Finder 13growth was 6.75-8.50. Although clam larvae can survive at pH 6.25, a pH of 7.0 is required fornormal development of the embryo. Levels of pH below 7.0 limit recruitment of the species(Calabrese 1972).”Dissolved oxygen. “Morrison (1971) found that growth of shelled veligers of M. mercenaria wasnormal when dissolved oxygen concentration was 4.2 mg/l or greater. Growth essentially ceasedat concentrations of 2.4 mg/l and less. Larvae survived extended exposures (14 days) to 1 mg/ldissolved oxygen but grew little. Prolonged exposure to levels of less than 4.0 mg/l lengthenedthe clams planktonic stage and decreased its probability of survival. Embryos developednormally at oxygen levels as low as 0.5 mg/l; however, 100% mortality occurred at 0.2 mg/l.Fluctuations in dissolved oxygen do not affect adult hard clams as much as do fluctuations intemperature and salinity (Stanley and DeWitt 1983). The burrowing ability of M. mercenaria wasneither severely nor permanently impaired by exposure to reduced oxygen levels (less than1mgl1 seawater) for up to 3 weeks (Savage 1976). Pratt and Campbell (1956) found nocorrelation between growth rates and various concentrations of dissolved oxygen. All life stagestolerate nearly anoxic conditions for long periods, though they may cease growing (Stanley andDeWitt 1983).”Salinity. “Salinity appears to be most critical for M. mercenaria during the egg and larval stages(Stanley and DeWitt 1983). At Long Island Sound, New York, eggs developed into straight-hinged veligers only within the relatively narrow salinity range of 20.0 to 32.5 parts per thousand(ppt ), The optimum for development of clam eggs was about 26.5 to 27.5 ppt (Davis 1958).Growth of larvae, once they attained the straight-hinged stage, was comparatively good atsalinities as low as 20 ppt (Davis 1958), but Chanley (1958) found that growth of juvenile M.mercenaria was retarded at salinities of 22.5 ppt or lower. Castagna and Chanley (1973) foundthat metamorphosis of M. mercenaria from veliger to seed clam (byssal plantigrade stage) wasinhibited below 17.5 to 20 ppt.”Temperature. “Davis and Ca1abrese (1964) noted that 1aboratory-rea red straight-hingedveligers of M. mercenaria were capable of ingestion, but not digestion, at 10°C (50°F),- andconsequently did not grow. Growth was positively related to temperature at 18.0° to 30.0°C (64°to 86°F). Growth of straighthinged veligers of M. mercenaria was little affected by temperaturedifferences within the range of 20° to 30°C (68° to 86°F). Although the optimum temperature forgrowth of M. mercenaria larvae was not well defined, growth was optimum at the followingtemperature/salinity combinations: 30°C (86°F)/22.5 ppt and higher, 27.5°C (81.5°F)/17.5 and20.0 ppt, and 25°C (77°F)/15.0 ppt.”Substrate. “The nature of the bottom substrate seems to be the main factor responsible forsettling of larvae and for the qualitative composition of bottom communities (Thorson 1955).Keck et ale (1974) reported from laboratory studies that significantly higher (P ~ 0.05) numbersof M. mercenaria larvae set in sand than in mud; they suggested that the addition of organicmaterial to the sediment may be responsible for reduced setting because of increased bacterialevels, reduced dissolved oxygen, and increased production of hydrogen sulfide. Carriker (1959)recommended that the substrate be firm and free of excessive organic mud for larval clamculture; muddy bottoms can be surfaced with shells, sand, or gravel. Adult Clams were mostabundant in predominantly fine sediments, but in these sediments their abundance was generally
  15. 15. Fish Finder 14a function of the coarseness of the minor constituents. Clams do not grow well in silty substrates.Pratt and Campbell (1956) found an inverse relationship between growth of M. mercenaria andthe fineness of the sediment (expressed as percentage of silt and clay). The inferior growth wasattributed to frequent gi1l clearing, which expended energy and interfered with feeding. Johnson(1977) also reported slower growth of M. mercenaria in finer sediment due to increasedexpulsion of pseudofeces.”Suspended solids. “Davis (1960) noted that both the larvae and egg stage are affected bysuspended solids. “Eggs did not develop correctly at silt concentrations of 3.0 or 4.0 g/L, andstraight-hinged veligers was normal at silt concentrations of 0.75g/L, retarded at 1.0 to 2.0g/L,and negligible at 3.0 and 4.0g/L”. ”