Generic li smp version 2 11.18.

P AGE 74 OF Table Table 3.2. 4. Settin comp curren pediv oyster resorb shellf metam 5. The e specie consis of em progr Common Name Quahog American Oyster Soft Shell Clam Bay Scallop Blue Mussel Razor Clam F 308 3.1. Summary The approxima of each stag ng metamorp etent to metam nt state of kno eliger will att rs who cemen bing the velum fish leave the morphic but p T exception to th es reproduce v sting of indiv mpty capsules. ess using non GenusSp Mercenar r Crassostr Mya aren Argopect Mytilus e Ensis dire of the reprodu ate duration of ge is influenced phosis in biva morphose to owledge is su tach itself to t nt to the subst m, developing larval phase a prior to reprod Table 3.3. Settin he general rep via internal fe vidual capsule The multiple n-fertile eggs pecies ria mercenaria rea virginica naria ten irradians dulis ectus C HAP ctive character f the larval stag d primarily by alves is often a specific hab ummarized in the substrate, trate on their g gills and un and enter into ductive matur ng cues for the productive cy ertilization fo es linked toget e larval devel as a nutrient s Trochophore D‐s 12 ‐ 24 h 12 ‐ 20 h 12 ‐ 24 h 12 ‐ 24 h 5 ‐ 24 h 12 ‐ 15 h TER 3: B IOLOG ristics of comm ges of shellfish environmental stimulated by bitat type. The Table 3.3. W normally thro left valve, an ndergoing othe o the juvenile rity, commonl shellfish speci ycle outlined a ollowed by the ther in a strin opment stage source. The ju stage veliger Umbon velige 1 ‐ 5 d 3 ‐ 15 20 ‐ 48 h 6 ‐ 7 d 1 ‐ 5 d 6 ‐ 7 d 17 ‐ 48 h 5 ‐ 6 d 1 ‐ 3 d 8 ‐ 12 1 ‐ 4 d 5 ‐ 7 d GY mercially impor h important to R l temperature a y the exposur e setting cues When appropri ough the actio nd will transf er morpholog stage of deve ly referred to ies included in above occurs e production ng and anchor es occur withi uvenile post-m ned er Pediveliger d 8 ‐ 20 d d 10 ‐ 12d d 10 d d 10 d d 24 ‐ 30 d d 8 ‐ 12 d N OV rtant shellfish Rhode Island w and food avail re of a pedive s vary with th iate habitat is on of byssus form to the ad gical changes. elopment, def as “spat”. n Chapter 3. with the whe of an elongat red to the sub in the capsule metamorphic Metamorphosis Rearin 10 ‐ 21 d 24‐ 14 ‐ 21 d 21‐ 10 ‐ 35 d 19‐ 10 ‐ 14 d 23 o 25 ‐ 30 d 15 o 13 ‐ 16 d 19 o VEMBER 18, 201 in Rhode Islan waters. The du lability. liger that is he species and encountered, threads exce dult body form . With setting fined as post- elks. Both wh ted egg mass strate by a ser e, where the la c whelks emer ng temperature; Refere ‐28 o C; Hadley Whetsto ‐21 o C; Stallworthy 1978 ‐24 o C; Loosanoff Davis o C; Leavitt Karney 200 o C; Hayhurst 2001 C; Flanagan 2013 14 nd. uration d our , the ept for m by g, the helk ries arvae rge nce one 2007 s 1964 05 N OVEMBER 18, 2014 C HAPTER 3: B IOLOGY P AGE 75 OF 373 from the egg capsules through an exit port in the side of the capsule. With this form of development, the dispersal of crawling juvenile whelks is much more limited than that of bivalves, which are free- swimming for up to 4 weeks during early development. On average, both whelk species deposit 20 to 50 eggs per capsule with a string consisting of 20 to 150 capsules. 6. With the exception of the oyster which permanently attached to the substrate they have chosen, the bulk of our shellfish species have the capacity to continue to change location as they grow through the juvenile stage. Some have the capacity to actively move by swimming bay scallop and razor clam or “walking” with their foot mussel and quahog while others can initiate a passive mechanism for movement, including incorporation into the sediment bedload transport associated with tidal currents soft shell clams or quahogs or forming a tool for dragging in the current byssal drifting in razor clams. Although the details of why a juvenile shellfish may initiate movement are not well understood, it is assumed that the environmental conditions associated with the initial settlement site may not be appropriate and the shellfish can initiate their variety of dispersal tools to change their location based on the chance of landing at a more suitable site. In general, as an individual clam grows larger, their ability to move becomes more restricted such that large-scale movement in adults is rarely observed. 7. Growth in individual shellfish, from larva to adult stages, is dependent on a variety of factors that mostly can be impacted by water quality parameters, such as temperature, dissolved oxygen or salinity, and food availability. Water temperature in these ectothermic animals animals whose body temperature varies with the environment controls the rate of metabolism and many other important biological processes, such as filtration and feeding rates. As such, shellfish growth rate varies seasonally with the fastest growth rate occurring within the range of water temperatures described as optimal for the species and the growth progressively decreasing as the temperature moves away from the optimal range. Salinity and dissolved oxygen have much the same affect on growth as conditions shift away from optimal ranges; however, these salinity changes are generally not observed as seasonal variations and while dissolved oxygen exhibits seasonal variation, summer low oxygen levels are associated with specific environmental events, such as episodes of heavy rainfall or degradation of eutrophic plankton blooms. 8. Food availability for filter feeding shellfish is a function of the plankton quality and flux. Plankton quality reflects the nutrient composition of the single-celled alga as well as the physical characteristics of the filtered particle; for example, filter-feeders target specific size ranges of particles for ingestion. Plankton flux is a function of the density of the microalgal particles in the water column combined with the rate at which the particles are available to the animal for filtration, i.e. the flow of particles across the siphonal intake of the individual shellfish. Many factors influence food flux, including the level of primary productivity in the water body, the water flow characteristics associated with the location where the shellfish settled, and the density of competing filter-feeding organisms in the vicinity of the individual clam, oyster or scallop. Situations such as reduced water flow, low plankton productivity or high densities of filtering organisms in the neighborhood, can all lead to a reduced availability of food for an individual resulting in slower growth. 9. The exception to a general discussion on mollusk feeding is the predatory gastropods, the whelks Busycotypicus canaliculatum and Busycon carica. Rather than filter food particles from the water column, these two snails are active predators and scavengers that have a mouth part proboscis adapted for inserting into a mollusk that has been opened slightly and initiating a presumptive toxin- mediated release of saliva that relaxes andor kills the prey and allows the valves to be opened further, to the point where the radula can tear off sections of prey flesh for ingestion. The strategy for initially opening the prey varies depending on the overall morphology of the shellfish Carriker 1951. If it is a bivalve that cannot completely seal shut its valves e.g. soft shell or razor clam then the proboscis has easy access to the soft tissue once the whelk grasps the valves of the prey with its muscular foot. If the bivalve can tightly seal its valves shut i.e. quahog or oyster, the whelk grasps the valves with its foot and waits for the bivalve to gape slightly as the bivalve starts to pump respiratory currents following the disturbance. As the bivalve gapes, the whelk inserts the edge of its shell beak into the P AGE 76 OF gap, w can in Anoth margi break the sh the wh to she 10. The o popul thresh chang rapid to be shellf 11. Befor to the the im Section 330.1 Stanl Other cherry and Shellfish F 308 wedging the v nsert its probo her strategy re in of the shell king open a ga hell of the wh helk does not ell repair resu overall effects lationmanage hold; age and ges in the env shellfish grow recognized an fish resources re delving into e management mportant shell n 330. Uniq

1. Quahog M

ley Dewitt r common nam ystone clam, a Table 3.4. valves open. W oscis into the eported for th l to chip away ap in the shell elk such that t grow and it i lting in zero s s of changes in ement parame or size at firs ironment are wth resulting nd accounted in Rhode Isla o the aspects t of shellfish i lfish species a que Attrib Mercenaria 1983, Everso mes: hard clam and chowder Environmenta C HAP With this foot valves and re he whelks is to y the thinner e l margin. This often it has b is proposed th size increase n the growth eters as recrui st reproductio negative, for in earlier rec for as shellfi and. of shellfish b in Rhode Isla are presented butes of Sh mercenaria ole 1987, Prat m, hard-shell clam. al conditions rep TER 3: B IOLOG thold, the whe elax the adduc o hold the biv edge of the sh s has consequ been reported hat the energy over time Ca patterns of sh itment into th on; fecundity; example incr ruitment into ish manageme iology that di and, a quick su below. hellfish Sp a tt et al. 1992, ed clam, roun eported for the GY elk works the ctor muscles o valve in its fo hell and gain uences to the p that during so y normally ap astagna and K hellfish can im he fishery, i.e. and life expe reased water t the fishery, t ent strives to irectly affects ummary of th pecies Imp Whetstone e nd clam, little quahog Merc N OV e valves open of the clam or ot and hamm access to the predator, in th ome time gro pplied to grow Kraeuter 1994 mpact such im . attainment o ectancy. Whil temperature m they are chan improve the p s issues identi he unique attr portant to et al. 2005 eneck clam, to cenaria mercen VEMBER 18, 201 by prying un r oyster furth mer at the vent soft tissue by hat it also bre owth observat wth is realloca 4. mportant shell of a legal size le not all proj may lead to m ges that will n production of ified as impor ributes of each Rhode Isl op neck clam, naria. 14 ntil it her. tral y eak tions, ated lfish ected more need f rtant h of and , N OVEMBER 18, 2014 C HAPTER 3: B IOLOGY P AGE 77 OF 373 1. Range The native range of the quahog is from the Gulf of St. Lawrence to Texas with a peak in abundance from Cape Cod, Massachusetts to Virginia. It has been successfully introduced into California Crane 1975, Hawaii Ziegler 2002, Europe Richardson Walker 1991 and China Chang et al. 2002. 2. Morphology and Identification This clam has a thick shell with short siphons and sometimes has a purple band on the ventral margin of the inside of the shell. It can grow up to 130 mm with morphometric ratios of lengthheight: 1.25, and length to width: 1.90. The elliptical shell is grayish white with concentric growth lines observable on the shell exterior. In wild populations, a rare reddish shell color pattern is sometimes observed at 1-2 of the population Eldridge et al. 1976, Walker et al. 1980, Humphrey and Walker 1982. Identified as a variety of quahog M. mercenaria var. notata, the unique shell markings are characterized as a red angular or zig-zag marking on the greywhite shell Verrill 1873, Smith 1961. Due ot the simple genetic construct of the coloration marker Chanley 1959, notata quahogs have been utilized by shellfish hatcheries as a marker for commercially reared quahogs, as hatcheries can enhance the overal density of notatas to 45-50 of the population through selective breeding Dillon and Manzi 1988, Littlefield 1991. 3. Habitat The quahog is an infaunal clam that burrows near the sediment surface and preferentially settles in sand to sandy mud. Adults can be found buried to about 2 cm in depth with smaller individuals burrowing deeper. Primarily subtidal, found up to a depth of 20 m, the quahog is also found intertidally in bays and estuaries. 4. Fisheries The quahog is the fifth largest fishery landed in Rhode Island with a dockside value of approximately 5 million in 2012. It is the largest fishery within Narragansett Bay and the coastal ponds of the state, where it is harvested by bullrake or by SCUBA. Dredging for quahogs is not allowed in RI state waters. In addition, there is a significant recreational fishery for quahogs within the state, again by hand harvesting in intertidal and shallow subtidal areas, although little data are available to characterize this aspect of the fishery. 5. Population Dynamics The quahog is commonly found throughout Narragansett Bay and in all of the RI coastal ponds although the highest densities are located in the upper one-half of the Bay. It can exist in very dense assemblages in RI waters, where reported densities have been as high as 500 individualsm 2 with an average density of 78m 2 in an area historically known for strong quahog production Greenwich Bay Rice et al. 1989. Based on the latest projection of standing stock in Narragansett Bay by RI- DEM Marine Fisheries, the stratified mean density of quahogs across the Bay is consistently between 2 and 3 quahogsm 2 RIDEM 2014. Natural mortality is similar to most bivalves, where the highest rate of natural mortality occurs during the earliest life history stages and the rate decreases as the bivalve grows Connell 1983. 6. Growth Characteristics Quahog growth in Narragansett Bay has been carefully monitored over many years, with the current growth characteristics depicted in Figure 3.3 Rice et al. 1989. The time to achieve legal size in Narragansett Bay quahogs has been getting longer over the past 50 years where the current estimate for a quahog achieving legal size is approximately 3-4.8 years Figure 3.4, Jones et al. 1989, Henry Nixon 2008. 7. Ecology P AGE 78 OF a. F de th pr re b. P R in qu W an th c. Pr co 3 B be of Figure 3. and Shellfish F 308 eeding Habits ependent on t he clam food resence in RI esearch is nec arasites and D Rhode Island a nconsequentia uahog disease Winnapaug Po nd the infecte he disease in l redation: It is ontrol factor i .5, along with Bricelj 1992. ecomes signif f thickening o 3. The valve le Management s: The quahog the food quali d flux. Recen waters may b cessary to full Disease: No s although mon al maladies S e Quahog Pa ond Westerly ed organisms local waters. s widely recog in wild quaho h the maximu On average, t ficantly less a of the shell A ength of quahog t Plan, Versio C HAP g feeds by filt ity as well as nt research sug be affecting th ly understand ignificant dis nitoring of sel Smolowitz, pe arasite Unkno y, RI in the m were remove gnized that na ogs. A list of c m size of clam the quahog is a controlling f Arnold 1984. gs from three N on II TER 3: B IOLOG tering phytop the rate of de ggests that ch he growth and these change sease situation ected batches ers. comm. O wn – QPX w mid-2000’s alt d from the po atural mortali common pred m that can be reported to r factor at betw Narragansett B 1989. GY plankton from elivery of the hanges in the p d reproductio es Henry and ns have been s of wild quah One situation was reported a though the sit ond, resulting ity, i.g. predat dators on the e preyed on by reach a size th ween 25 and 4 Bay sites plotte N OV m the water co food particle patterns of ph on of the quah d Nixon 2008 noted for wil hogs has reco of a potential at an aquacult tuation was q g in no further tion, is the pr quahog are in y each predat hreshold wher 40 mm length ed as a function VEMBER 18, 201 olumn so grow e to the siphon hytoplankton hog although . d quahogs in ognized nume lly significant ture site in quickly recogn r developmen imary popula ncluded in Fig tor species fr re predation , due to the d n of age Rice 14 wth is ns of more rous t nized nt of ation gure rom egree et al.