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Guide to Intertidal BivalvesIn Southwest Alaska National Parks

Katmai National Park and PreserveKenai Fjords National Park

Lake Clark National Park and Preserve

National Park Service

Inventory & Monitoring ProgramSouthwest Alaska Network

Dennis C. LeesLittoral Ecological & Environmental

Services075 Urania Avenue

Leucadia, California 92024May 2006

National Park ServiceSouthwest Alaska Network

Inventory and Monitoring ProgramReport Number:

NPS/AKRSWAN/NRTR-2006/02

Guide to Intertidal BivalvesIn Southwest Alaska National Parks

Katmai National Park and PreserveKenai Fjords National Park

Lake Clark National Park and Preserve

Dennis C. LeesLittoral Ecological & Environmental

Services075 Urania Avenue

Leucadia, California 92024May 2006

National Park ServiceSouthwest Alaska Network

Inventory and Monitoring ProgramReport Number:

NPS/AKRSWAN/NRTR-2006/02

Cover Photograph: (Top left)

(Bottom left)

(Right)

Brown bear feeding on softshell clamsin an intertidal mud flat in front of Katmai Wilderness Lodge, KukakBay, Katmai National Park and Preserve. Depth and size relationshipsamong Baltic macomas, oval macomas, softshell and truncatesoftshell clams in the sediment cross-section are approximatelyrepresentative from top to bottom.

Brown bear prospecting for razor clams on broad sand flatin front of Silver Salmon Creek Lodge, Lake Clark National Park andPreserve. Depth and size relationships among Alaska great-tellin,Arctic surf clam, and Pacific razor clams in the sediment cross-sectionare approximately representative from top to bottom.

Researchers sampling on a beach of mixed-soft sediments inMcCarty Lagoon, McCarty Fjord, Kenai Fjords NP. Depth and sizerelationships among northern horsemussel, littleneck clams, bentnosemacomas, and butter clams in the sediment cross-section areapproximately representative from top to bottom.

Recommended Citation

Keywords

Abbreviations

Lees, D.C. 2006. Guide to Intertidal Bivalves In Southwest AlaskaNational Parks: Katmai National Park and Preserve, Kenai FjordsNational Park, and Lake Clark National Park and Preserve.National Park Service Alaska Region, Inventory and MonitoringProgram. 57 pp.

Infauna; bivalve; inventory; intertidal; soft-sediment; SouthwestAlaskaNetwork, Katmai National Park and Preserve; Kenai Fjords NationalPark; Lake Clark National Park and Preserve.

KATM—Katmai National Park and PreserveKEFJ—Kenai Fjords National ParkLACL—Lake Clark National Park and PreserveMLLW—Mean Lower Low WaterNPS—National Park ServiceSWAN—SouthwestAlaska Network of the National Park Service

Guide to Intertidal Bivalves of Southwest Alaska Parks

The National Park Service's primary mission is to conserveunimpaired the natural and cultural resources and values of thenational park system for the enjoyment of this and futuregenerations. Preservation of healthy parks depends on acquiringaccurate and timely information about the condition of naturalresources, monitoring the change of conditions over time, and actingon that information with confidence. The National Parks OmnibusManagement Act of 1998 created a program to collect baselineinformation and to monitor long-term trends in the condition ofnatural resources in national parks. In 2000, this Inventory andMonitoring Program was initiated at Alagnak Wild River, AniakchakNational Monument, Katmai National Park and Preserve, KenaiFjords National Park, and Lake Clark National Park and Preserve.These park units, collectively known as the Southwest AlaskaNetwork (SWAN), contain over 1,000 miles of marine coastline inthe Northern Gulf of Alaska.

In 2004-2006, the SWAN Inventory and Monitoring Programcontracted with Dennis Lees, Littoral Ecological & EnvironmentalServices, to assess the species composition and distribution ofmarine bivalve invertebrates on soft sediment intertidal beaches.Bivalve invertebrates provide an important prey resource forshorebirds, ducks, fish, bears, sea otters, humans, and other marineand terrestrial predators. Because they are sedentary and long-lived, they are sensitive indicators of environmental stress or changein the nearshore marine environment. Information from thisinventory has expanded our knowledge of bivalve invertebrateoccurrence in the SWAN, assisted in the design of a long-termmonitoring program for the parks, and through this Guide willfacilitate the identification and appreciation of intertidal animals.

Alan Bennett, CoordinatorSWAN Inventory and Monitoring Program

Forward


Several members of the staff for the NPS Southwest Alaska Networkcontributed substantially to the successful execution of the studyunderlying this guide. Mr. Alan Bennett's considerable contributionsto program design and logistical and field support were invaluable.Other NPS personnel that accompanied the LEES field teamincluded Laurel Bennett, Shelley Hall, Chief of ResourceManagement for KEFJ, Mr. Ian Martin, KEFJ Ecologist, and Dr. AmyMiller, Ecologist for SWAN. Furthermore, the assistance of Mr.William Driskell and Mr. Howard Teas were critical to the success ofthe bivalve studies. The enthusiasm, interest, knowledge, sharpeyes, and good humor of these individuals were key to the successof this field survey.

Finally, the author wishes to extend thanks to Ms. Nora Foster andDr. Eugene Coan for their permission to use drawings from theirpublications in this guide. These excellent figures, illustrating crucialdiagnostic characteristics, have been important in differentiatingamong similar species.

Acknowledgments

Table of ContentsIntroduction 1

Notes on Habitat, Ecology, Structure and Evolution 6

Descriptive Guide and Comments 15

____________________________________________

___________Habitats..................................................................................... 6Feeding Types .................................................................Modes of Life ................................................................... . 12

__________________________Glychmerididae

...Mytilidae

..............

Ungulinidae..

Thyasiridae..

Lasaeidae..

..Cardiidae

.

.Veneridae

Turtoniidae

Tellinidae

......... 11

........Obtaining and Handling Clam Specimens ................................ 13Risks from Paralytic Shellfish Poisoning ................................... 15

.....16

. 17.............. 18

...................... 19

........................ 20

.......... 21... 22

....................... 23

..... ............. 24

................................................................................... 25

............................ 26

..................................................................... 27

................................................................... 28

.................................. 30

............................... 31............................... 33.............................. 34

..................... 36............................... 37

........................ 38....................... 39

Western Bittersweet (Glycymeris septentrionalis)

Foolish Mussel, also Pacific Blue Mussel, Northern BayMussel, or Edible Mussel (Mytilus trossulus)Northern Horsemussel (Modiolus modiolus)

Rough Diplodon (Diplodonta impolita)

Sily Axinopsid (Axinopsida serricata)

Suborbicular Kellyclam (Kellia suborbicularis)Compressed Montacutid (Neaeromya ?compressa)Robust Mysella (Rochefortia tumida)

Low-Rib Cockle (Clinocardium blandum)Basket Cockle, also Nuttal Cockle (Clinocardium nuttallii)

Lord Dwarf-Venus (Nutricola ?lordi)Littleneck Clam, also Pacific Littleneck Clam (Protothacastaminea)Butter Clam, also Washington Butter Clam (Saxidomusgigantea)

Minute Turton (Turtonia minuta)

Alaska Great-Tellin (Tellina lutea)Salmon Tellin (Tellina nuculoides)Baltic Macoma (Macoma balthica)Expanded Macoma (Macoma expansa)Oval Macoma (Macoma golikovi)Pointed Macoma (Macoma inquinata)Bent-Nose Macoma (Macoma nasuta)

Pharidae................................ 40

............................ 42

.................... 44.................................... 46

.................................... 47............... 49

...................... 50

.................................... 51

Alaska Razor Clam (Siliqua alta)Pacific Razor Clam (Siliqua patula)

Mactridae

Myidae

Hiatellidae

__________________________________________

Arctic Surfclam (Mactromeris polynyma)Pacific Gaper (Tresus nuttallii)

Softshell Clam (Mya arenaria)False Softshell Clam (Mya pseudoarenaria)Truncate Softshell Clam (Mya truncata)

Arctic Hiatella (Hiatella arctica)

Glossary _______________________________________________ 52

Literature Cited 55

The purpose of this guide is to provide assistance to visitors to theSouthwest Alaska Network (SWAN) national parks and NationalPark Service staff in identifying, understanding, and enjoyingbivalves found in intertidal sediments in the SWAN parks. We haveprovided brief sections on the ecology of these clams, includingcomments on their habitats and feeding types, and a descriptiveguide to the clams. The descriptive guide includes drawings andphotographs to depict the appearance of the clams both in the handand, where possible, the appearance of distinguishing indicators oftheir presence in the field. For each species, we have included abrief description of the clam, its typical habitat, and its distributionamong the parks and in the North Pacific.

Bivalves are a critical source of nutrition for major predators such asbears, sea otters, sea (diving) ducks, shorebirds and otherinvertebrates at some time during the year. For example, bearsalong the KATM coast achieve higher rates of energy from razorand softshell clams than those foraging on vegetation (Smith 2004).

In addition to supporting the bears, sea otters, diving ducks, andshorebirds for millions of years, clams have been a major source offood for native Alaskans since their arrival in Alaska 15,000 to20,000 years ago. They have been important in the success ofnative cultures in coastal environments. Evidence of thedependence of the native Alaskans on several species of clams forfood has been well documented in archaeological excavations ofshell middens in the vicinity of old coastal villages.

Bivalves provide insight into a very ancient and very successfulinhabitant of our beaches. Early clams appear in the fossil recordabout 620 million years ago during the Cambrian period. Theybecame one of the dominant life forms in the oceans over 200million years ago and remain so today (Yonge 1960). On softbeaches, clams are a dominant sedentary life form in a variety ofhabitats, have a wide range of physiological tolerances, and areamong the longest living animals, some species living at least 20


Introduction

1


Map of Southwest Alaska National Parks covered in thisGuide: Lake Clark National Park and Preserve; KatmaiNational Park and Preserve, and; Kenai Fjords NationalPark.

Introduction (continued)years. With such longevity and lack of mobility, they are goodindicators of long-term conditions (Bennett 2006). It can beassumed that beaches supporting reasonable numbers of long-lived clams are stable and “healthy.”

2

Introduction (continued)This guide includes descriptions of twenty-nine species inthirteen families that were found in surveys of beaches in threeSWAN national parks during the summers of 2004 and 2005(Lees and Driskell 2004, 2006a, and 2006b). The parkssurveyed were Katmai National Park and Preserve (KATM),Kenai Fjord National Park (KEFJ), and Lake Clark National Parkand Preserve (LACL). Species composition of the clams variedconsiderably by park. Approximately the same number of clamspecies was observed in KATM and KEFJ, but LACL supportsfar fewer species. Only Baltic macomas and softshell clamswere found in all parks. In contrast, half the species were foundonly in KATM (7) or in KEFJ (7).

The two figures on the next page show a number of the shelland soft tissue characters that are used to describe the clams inthe guide. Definitions of these and many other features areprovided in the Glossary. Many other characters, especiallyexternal features, are demonstrated in the figures used toillustrate important characteristics for particular species.

The frequency with which the species occurred in the parksprovides some indication of the likelihood that the clams or theirshells will be encountered while examining park beaches. Manyspecies were observed only rarely in one or more parks. Forspecies indicated by an asterisk (*), the individual clams arequite small and unlikely to be observed without the aid of amagnifying glass or a microscope. Clearly, Baltic macomas andfoolish mussels were encountered far more frequently than anyother species. The second tier for frequency of occurrenceincludes littleneck, butter, and softshell clams, oval macomas,and Arctic hiatellas.

The families are presented in order of evolutionary development(phylogeny), starting with the earliest, most primitive forms. Thescientific and common names and phylogeny used in thisdocument are based largely on the taxonomic treatment ofCoan, Valentich Scott, and Bernard (2000). Drawingsreproduced in the text are based on Foster (1991) and Coan(1971), as cited.

Guide to Intertidal Bivalves of Southwest Alaska Parks 3


Important internal shell features used in descriptions of theclams in this guide (drawing after Foster 1991).

a. adductor musclesb. bodyf. footg. gillsl. ligamentm. mantle edgep. labial palps. siphonv. viscera (i.e.,gonad, digestiveorgans, heart,excretory organs)

Important soft parts used in descriptions of clams in this guide(after Foster 1991).

4

Number of times clam species were observed in samples andtheir distribution among the parks.

SPECIES/PARK KATM KEFJ LACL Total

Western bittersweet 1 1

Foolish mussel 16 88 104

Northern horsemussel 9 9

Rough diplodon 2 2

Silky axinopsid* 8 8

Suborbicular kellyclam* 1 1

Compressed montacutid* 1 1

Robust mysella* 3 16 19

Low-rib cockle 1 1

Basket cockle 11 8 19

Lord dwarf-venus* 1 5 6

Littleneck clam 5 35 40

Butter clam 11 23 34

Minute turton* 7 1 8

Alaska great-tellin 1 1

Salmon telllin 7 7

Baltic macoma 39 69 26 134

Expanded macoma 3 1 4

Oval macoma 19 24 43

Pointed macoma 3 9 12

Bent-nose macoma 1 1

Alaska razor clam 7 7

Pacific razor clam 1 6 7

Arctic surf clam 8 8

Pacific gaper 2 2

Softshell clam 24 4 8 36

False softshell clam 6 5 11

Truncate clam 1 7 8

Arctic hiatella 33 33

Number of Samples inWhich Encountered 177 350 40 567

Number of SpeciesEncountered 22 21 3 29

* Individuals of species too small to be observed without a

magnifying glass or microscope.


Three important functional attributes in our consideration of clamspecies are the type of habitat they inhabit, how they occupy thehabitat, and how they feed and live. These factors have structuralramifications that have been realized through evolution. Theseattributes are discussed in the sections below.

HabitatsThe three major types of sediments found on beaches supportingclams in the parks are low-energy, protected muddy habitats (mudflats), high-energy sandy beaches, and sediments comprisingvarying amounts of silt, sand, gravel, cobbles, and boulders(referred to below as mixed-soft sediments) in low to moderatelyhigh-energy situations. All habitats support one or more speciesutilized as prey by “charismatic” predators such as brown bears,sea otters, diving sea ducks, or shorebirds, or support subsistenceor commercial fishing by man.

The proportion of these habitats varies considerably among thethree parks considered herein. Because clam species typicallyprefer a single generalized habitat type (but may occur in more thanone), dominance patterns by the clams vary markedly among theparks. This is demonstrated clearly in the table above.

Notes on Habitat, Ecology, Structure and Evolution

Typical intertidal mudflat that supports

softshell clams andBaltic macomas.(Head of James

Lagoon, at the north(upper) end of McCarty

Fjord, KEFJ, atapproximately +2.0 ft(0.6 m) above MLLW.

Guide to Intertidal Bivalves of Southwest Alaska Parks6

Mud flats are productive across a wider range of vertical elevationthan the other habitat. Because the sediments are fine, they holdgreater volumes of water during the immersion that occurs duringlow tides. The retained water buffers the animals living in thesediments from desiccation and temperature extremes that canoccur during immersion. Consequently, the bivalve fauna on mudflats is similar from lower tide levels (below Mean Lower Low Water(MLLW) to at least 10 feet above MLLW where salinity remains highenough to support clams during high tide.

Sand beaches typically only support clams up to about 3 feet aboveMLLW. Above that elevation, desiccation and temperatureextremes experienced during low tides exceed the clams' tolerance,especially juveniles living in upper layers of sediment.

Typical sand beach that supports razor clams and surfclams. (Near Silver Salmon Creek Lodge in LACL about3.5 ft (1.1 m) below MLLW.)


Seawater also drains rapidly out of mixed-soft sediments whenwater levels fall during low tides. Consequently, the animals livingin these sediments are similarly exposed to desiccation andtemperature extremes and so significant populations of clams arelimited to a few feet above MLLW.

Mixed-soft sediment with considerable shell debris fromlittleneck and butter clams. (The sediments in thesemixed-soft photographs are located along the north shoreof McCarty Lagoon in McCarty Fjord, KEFJ, about 2.3 feet(0.7 m) below MLLW.)


Because the pebbles, cobbles, and small boulders in the mixed-softhabitats tend to become “cemented” over time as they are jostledand reorganized by wave action and current flow, and fine sedimentfills into the interstices among the larger particles, these particlesprovide an “armor” at the surface that protects the sediment andyoung specimens of many recruiting species from disturbance bywave action. Consequently, many more species can becomesuccessfully established in mixed-soft habitats than are observed inmud or sand habitats and these habitats are far richer than the finersubstrates. This trend is apparent in many other types of organismas well as bivalves (e.g., burrowing shrimp, worms, and seacucumbers).

The three major habitat types are not distributed equally within oramong the parks. KATM has large areas of mud flats north ofKukak Bay, and especially in Kamishak Bay near Douglas River.This same area also has long stretches of sandy beach and sandflats. However, the sandy areas appear to be too exposed tosupport significant intertidal clam populations. The beaches fromKukak Bay south are generally smaller and more varied than in thenorthern region because the coastline is dissected by numerousbays that create a wide variety of exposures and sediment types.Multiple examples of all three major habitat types occur in thesouthern region of KATM.

Typical mixed-softbeach that

supports littleneckand butter clams.


KEFJ is characterized mainly by mixed-soft habitats and mud flats.It has more mixed-soft beaches than the other parks. Exposedsandy beaches are uncommon, resulting in the virtual absence ofrazor and surf clams.

LACL is characterized mainly by mud flats and exposed or semi-exposed sand beaches. Many of the sand beaches support healthypopulations of razor clams. The mud flats that are not overlyinfluenced by freshwater runoff generally support healthypopulations of softshell clams and Baltic macomas. However, dueto the near absence of mixed-soft habitats, species adapted to suchhabitats (e.g., littleneck and butter clams) have not been observed inthis park.

Clam species living in predominantly low-energy, protected muddyhabitats include:

Clam species living in predominantly high-energy sandy habitatsinclude:

Clam species living in low- to moderate-energy, mixed-soft habitatsinclude:

Pointed macomaNorthern horsemussel

Softshell clam

False softshell clamPointed macomaSilky axinopsid

Pacific razor clam

Alaska razor clamSalmon tellin

Littleneck clam

Butter clam

(Mya arenaria)

(Mya(Macoma inquinata)

(Axinopsida serricata)

(Spisula patula)

(Siliqua alta)(Tellina nuculoides)

(Protothaca staminea)

(Saxidomus gigantea)

Truncate softshell clamBaltic macomaOval macoma

Alaska great-tellinArctic surf clam

(Mya truncata)(Macoma balthica)

(Macoma golikovi)pseudoarenaria)

(Tellina lutea)(Mactromeris polynyma)

Foolish musselRough diplodonGaper clams

(Mytilus trossulus)(Diplodonta impolita)

(Tresus spp.)

modiolus)(Macoma inquinata)

(Modiolus


Feeding TypesThe species discussed in this guide have two predominant feedingmodes. All but the macomas and tellinids are obligatory suspensionfeeders. They pump large volumes of water from the water columnover the gills and filter from that water the suspended planktonand/or particulate detrital matter that is then passed into thedigestive tract for nutrition. In contrast, the macomas and tellinidsare facultative suspension/deposit feeders. Depending on thevelocity of the currents sweeping their habitat, they can eitherfunction as a suspension feeder or, under calmer conditions, theyuse their long, flexible incurrent siphons like a vacuum-cleaner hoseto suck up a concentrated layer of organic matter from the surfaceof the sediments around their siphon holes.


Modes of LifeThe bivalves observed during this study typically dwell in one of atleast three different modes. Some, such as foolish mussels, have amostly surficial lifestyle, i.e., they live on top of the sediments.Some species are nestlers, i.e., they nestle at the surface amongthe larger particles or in burrows created by burrowing organisms.These include the Arctic hiatella and robust mysella. But the mostcommon forms are burrowing clams, i.e., those that live burrowed atvarying depths in the sediments. These include such species aslittleneck, butter, razor, and softshell clams. Specimens of thenorthern horsemussel can be found utilizing all three modesdescribed above.

All burrowing species observed during this study connect to theoverlying surface water through incurrent and excurrent siphons ofvarying length. These species extend their siphons throughtemporary openings in the sediment or semi-permanent burrows toconnect to the surface of the sediment and achieve access to thewater column. This is necessary because the water contains foodand oxygenated water. This connection also allows the clams todischarge wastes and reproductive products. The length of thesiphon varies from a few millimeters, in the case of horsemusselsand cockles, to half a meter in the case of gaper clams.

These different modes of life have structural implications for theclams. Those that live at the surface or nestle in burrows of otherorganisms do not have a need for long siphons and diggingcapabilities. Short siphons appear to represent the more primitivecondition in clams. It appears that primitive bivalves rested on thesurface of the substrate and had no need for elongate siphons.Living on the surface, they were more exposed to predators andenvironmental stresses. One strong evolutionary trend appeared toprovide features that would allow the clams to move deeper into thesediments, reducing susceptibility to these factors. But such anadaptation required that burrowing clams develop elongatedsiphons to retain access with the overlying water, which hasstructural implications.


Thus, a clam's mode of life is indicated by various shell structures.Those living at the surface do not need elongated siphons.However, clams with elongated siphons need to be able to retractthem to some degree to escape predators wishing to feed on them.Retraction of siphons imposes a requirement for retractor musclesand these must be accommodated within the shell cavity. Thiscavity is lined with a layer of tissue, the mantle, which envelops thebody of the clam and produces the shell. The interior of the shellexhibits a scar, the pallial line, marking where the margin of themantle attaches to the shell. As the retractor muscles increased insize, the space required to accommodate them is reflected on theinterior of the shell in an invagination of the pallial line as the mantleretracts to make space. This invagination of the pallial line is calleda pallial sinus. As clams evolved to burrow deeper into thesediment, they needed longer siphons and larger retractor muscles,so the pallial sinuses became correspondingly larger. In most deep-burrowing clams, the siphon is often so large that it can't beretracted completely into the shell. Consequently, the posteriorends of the shell have a gap between them to accommodate thesiphon. This is most conspicuous in very deep-burrowing clams likegapers and geoducks.

Two other features characterizing bivalves appear to haveaccompanied the evolution of the burrowing mode of life. Clamsliving on the sediments are generally relatively small and short-lived(1-5 years). In contrast, it appears that as the clams gainedprotection by burrowing into the sediment, they were able to livelonger and grow bigger. Again, this is very apparent in geoducks,which attain weights of up to 5.5 kg (12 lb) and are estimated to liveup to 130 years.


Obtaining and Handling Clam SpecimensGenerally, the identity of clams inhabiting beaches can bedetermined by examining empty shells found on the surface of thesediments. An advantage of these loose, empty shells is that theycan be carried back to camp for close examination with this guide orother references. However, while visiting beaches, visitors may betempted to do some digging to obtain live specimens and get abetter sense how these animals live. A clam digger should only digdirectly where they see what appear to be clam “shows”. Random,undirected digging needlessly disturbs sediments and the residentfauna and, in mixed-soft sediments, the armoring established by thepebble/cobble matrix that protects young clams from winter stormactivity and took many years to become established.

Before a visitor embarks on digging and examining live clams, he orshe should first become familiar with a few basics of clam anatomy,particularly how to recognize the anterior and posterior end of theclam. This will be important in replanting the clam after examinationis complete.

The safest, most environmentally sensitive way to dig a clam, atleast for the clam, is to dig by hand, starting at the siphon hole, andexcavate down to the level of the clam using the burrow as a guide.When the digger gets down to the level of the clam, he or she mayencounter the siphon. Digging should proceed past that point downfar enough that the fingers can grasp the shell beyond its fattestportion and cup it between the fingers. The clam can then beextracted vertically from the sediment.

Far fewer clams will be broken if they are dug by hand. This isimportant because survival of broken clams is low. One must takeconsiderable care when excavating razor clams by hand to avoidcracking the fragile shell and, in addition, to protect one's self fromthe sharp edges of a fractured shell, which act on the fingers muchlike the name of the clam if the digger is careless.


Obtaining and Handling Clam Specimens (continued)When replacing clams in the sediments, most must be placedvertically in the sediment so that the foot (the anterior end) facesdownward and the siphons (the posterior end) face upward. Theyshould be placed in a hole that is approximately as deep as theywere located before extraction. The hole should then be gently filledpartially with mainly fine sediments to hide the clam from predatorsbut allow it to re-establish its siphon hole slowly as the sedimentsrefill the hole.


Risks from Paralytic Shellfish Poisoning (PSP)Visitors boating or camping in the parks may be tempted to harvestand eat mussels or other clams during their visit. This practice isnot advisable unless there is clear local evidence that the localstocks are not contaminated with the toxin responsible for paralyticshellfish poisoning (PSP). PSP, caused by blooms of a particularspecies of phytoplankton, occurs mainly during warmer months,when most people visit the parks. Phytoplankton blooms are oftenlocalized, especially in embayments. Consequently, the fact thatrazor clams tested for commercial operations at Polly Creek, inLake Clark National Park, does not assure that clams harvestedelsewhere in that or another park are safe for human consumption.Moreover, some clams retain the toxin for as much as two yearsafter a PSP episode. Finally, sea otters consuming clams canrecognize and discard the PSP-contaminated tissues so it is notacceptable to use clam-feeding observations as a justification forconsuming clams.

15

Descriptive Guide and CommentsDescriptions are summarized from Foster (1991) and Coan,Valentich Scott, and Bernard (2000). Natural history notes arebased on personal observations or Morris et al. (1980).


DescriptionShell ovate to trigonal, discoidal,compressed to moderately inflated,moderate to thin in thickness;anterior end generally longer, slightlyproduced; posterior margin rounded.Beaks orthogyrate. Radial sculptureevident in unworn specimens, wherethe outer surface is marked with verylow, flat radial ribs and concentricgrowth checks. Hinge plate arched,with taxodont dentition; inner shellmargin crenulate. Periostracumthick, dark, dehiscent, shaggy, finelyhirsute; where worn, the shell ischalky, ash-white, with brown orpurplish flammules. Interior colormarkings match pattern on theshell's exterior. Length to 45 mm(1.8 inches).

HabitatMixed-soft, fine-gravel, or sandhabitats from low intertidal zone to150 m (492 ft).

Significant PredatorsUnknown.

Western bittersweet, rightvalve exterior (after Foster1991).

Western bittersweet, rightvalve exterior (after Foster1991).

Range in Park and PacificDuring the 2004-2005 surveys, thisspecies was found only in KEFJ at asingle site. Reported from ChirikofIsland, Alaska to southern California. Western bittersweet, left valve

interior (after Foster 1991).

Glycymerididae

Western Bittersweet(Glycymeris septentrionalis)

16


DescriptionShell blue-black or brownish,trigonal, flared, outline variable,frequently expanded dorsally.Ventral surface relatively widelaterally; anterior end pointed, oftencurved. Hinge plate dark to light incolor, curved. Anterior adductormuscle scar relatively small;posterior byssal retractor musclescar relatively long, narrow. Interiorwith blue muscle scars and pale bluemargins. Length to 100 mm (3.9 in).

HabitatForm dense extensive beds inmixed-soft habitats or in sparse bedsin mud flats in mid and lowerintertidal zones in rocky and mixed-soft habitats.

Significant PredatorsSea otters, sea ducks, and blackoystercatchers; possibly black bears;crabs, starfish.

Foolish mussel, left valveexterior (after Foster 1991).

Foolish mussel, right valveinterior (after Foster 1991).

Large mussel bed in entrancechannel to McCarty Lagoon.

Close-up of mussel bed in tidalchannel.

Mytilidae

Foolish Mussel,Pacific Blue Mussel, Northern BayMussel, or Edible Mussel(Mytilus trossulus)

Range in Park and PacificDuring the 2004-2005 surveys,mussels were found quite commonlyin large beds in KEFJ, lesscommonly in KATM, generally not inbeds, and were absent in LACL.Reported from Canadian Arcticthrough Bering Sea, south to centralCalifornia.

Individual foolish mussel onrocky substrate.

17

Northern Horsemussel(Modiolus modiolus)

DescriptionShell smooth, rhomboidal,moderately inflated; antero-ventralmargin projecting slightly in front ofumbones. Periostracum dehiscent,anterior and ventral surfaces glossychestnut brown; posterior dorsalsurface hairy, with sparse, short,non-serrate setae, broad on bothsides at base; often encrusted withsand or other particles. Shellbeneath periostracum violet; interioriridescent and whitish. Hairyperiostracum and position of beaksdistinguish this species. Length to180 mm (7.1 in).

HabitatMixed-soft and cobble/boulderhabitats from lower low intertidalzone to 200 m (656 ft). Formsnestling or infaunal beds in muddy,sandy gravel and cobble beds withposterior end of shell at sedimentsurface, using byssal threads to bindrocks and particles together.

Significant PredatorsSea otters, starfish.

Northern horsemussel, left valveexterior (after Foster 1991).

Northern horsemussel, rightvalve interior (after Foster1991).

Adult northern horsemusselshowing rough periostracumand byssal threads.

Mytilidae


Range in Park and PacificFound at several mixed-soft sitesonly in KEFJ. Circumboreal;reported from Bering Sea south tocentral California; Greenland,northern Atlantic Ocean.

18

Rough diplodon, left valveexterior (after Foster 1991).

Rough Diplodon(Diplodonta impolita)

DescriptionShell very inflated, nearly orbicularto spherical, equilateral; postero-dorsal margin short, relativelystraight; beaks high and prominent;shell surface with irregular, lowcommarginal growth lines.Periostracum very thin, generallydark in color, usually eroded andshowing a grayish shell. Hinge teeththick, not deeply bifid; posterioradductor muscle scar decidedlylonger than anterior scar in adultspecimens. Length to 36 mm (14in).

HabitatMixed-soft habitats from lowintertidal zone to 100 m (328 ft).


Rough Diplodon(Diplodonta impolita)


Two specimens of roughdiplodon showing theglobular nature of its shape.

Range in Park and PacificFound at only a few sites in KEFJ.Kodiak Island to Oregon.

Ungulinidae

Rough diplodon, rightvalve interior (after Foster1991).

19

Thyasiridae

Group of adult silkyaxinopsids showing scale.

Silky axinopsid, right valveexterior (after Foster 1991).

Silky Axinopsid(Axinopsida Serricata)

DescriptionShell white, small, thin, smooth,ovate, inflated; umbones prominent,overhang slightly concave antero-dorsal margin; postero-dorsal marginnearly straight; lunule concave,obscure. Hinge plate weak, bothvalves with strong central tooth; rightvalve with obscure, elongate lateral.Periostracum transparent, yellow, orlight green. Length to 8 mm (0.3 in).

HabitatMuddy to sandy mud habitats fromlow intertidal zone to 275 m (902 ft).


Silky Axinopsid(Axinopsida Serricata)


Range in Park and PacificFound at several locations in KEFJ,sometimes abundant. Circumborealand panarctic; Point Barrow, Alaska,Bering Sea and Gulf of Alaska southto Baja California and Gulf ofCalifornia. Western Pacific Oceansouth to northern Japan.

Silky axinopsid, left valveinterior (after Foster 1991).

20


DescriptionShell evenly ovate to globular, ratherthin to translucent, inflated; sculpturelacking. Umbones prominent; hingeplate feeble; hinge with cardinal andposterior lateral tooth in right valve;two cardinal teeth and a posteriorlateral tooth in left valve; resilium liesbetween cardinal and lateral teeth.Periostracum shiny light olive greenor yellowish, thin, adherent overwhite shell. Length to 31 mm (1.2in).

HabitatMixed-soft habitats, often nestling inholes or crevices from low intertidalzone to 20 m (66 ft).


Suborbicular kellyclam, leftvalve exterior (after Foster1991).

Right exterior and leftinterior valve of adultsuborbicular kellyclam.

Range in Park and PacificRare in parks, found at only onelocation in KEFJ. Appears to be arange extension. Circumboreal;Prince William Sound to Peru.Western Pacific south to HonshuIsland, Japan.

Suborbicular kellyclam,right valve interior (afterFoster 1991).

Lasaeidae

Suborbicular Kellyclam(Kellia suborbicularis)

21


DescriptionShell ovate-quadrate tosubquadrate, thin, compressed;anterior and posterior ends broadlyrounded; dorsal margin of right valveoverlaps left valve slightly; sculptureof irregular commarginal ribs andstriations. Umbones small, notprominent. Right valve with verysmall, peg-like cardinal tooth anddeep resilifer, left valve withmatching socket and obliqueresilifer. Periostracum thin, silky todull, transparent to light brown.Length to 20 mm (0.8 in).

HabitatSandy and muddy habitats from midintertidal zone to 700 m (2,297 ft).Probably commensal, nestling inburrows of large burrowingorganisms such as fat innkeepers(Echiurus) and mud shrimp(Upogebia).


Compressed montacutid,right valve exterior (afterFoster 1991).

Compressed montacutid, leftvalve interior (after Foster1991).

Compressed Montacutid(Neaeromya ?compressa)

Range in Park and PacificFound at only one location in KEFJduring this project. Point Barrow,Alaska to San Diego, California.

Right valve exterior of adultcompressed montacutid.

Lasaeidae

22

Robust Mysella(Rochefortia tumida)

DescriptionShell small, thick, chalky,subtrigonal to subquadrate,moderately inflated; inequilateral,anterior end much longer; sculptureof fine commarginal striations.Umbones prominent, often eroded;left valve is edentulous; right valvewith two strong, diverging, subequalcardinal teeth below beaks.Periostracum thick, silky, lightbrown. Length to 5 mm (0.3 in).

HabitatProtected sandy, silty-sand, ormixed-soft habitats from lowerintertidal zone to 973 m (3,192 ft).Nestling at surface or commensal inburrows of burrowing organisms.


Robust mysella, left valveexterior (after Foster 1991).

Robust mysella, right valveinterior (after Foster 1991).

Group of adult robust mysellasshowing small size.


Range in Park and PacificOne site in KATM and several sitesin KEFJ. Beaufort Sea, Alaska, toSan Diego, California, and Gulf ofCalifornia.

Lasaeidae

23

Rough diplodon, left valveexterior (after Foster 1991).

Low-Rib Cockle(Clinocardium blandum)

DescriptionShell medium-sized, oval, somewhatlonger posteriorly, inflated; sculptureof about 45 low ribs sometimesoverlain by feeble commarginalriblets; interspaces generally narrow.Folds on posterior slope weakcompared to C. nuttallii. Externalcolor yellow to brown. Inner shellmargins shallowly crenulate. Lengthto 50 mm (2 in).

HabitatMud flats or muddy habitats fromintertidal zone to 80 m (262 ft).Burrows with posterior end of shellsjust below the surface of thesediment.

Significant PredatorsProbably sea otters, gulls, andstarfish.

Low-Rib Cockle(Clinocardium blandum)


Left and right valves of low-rib cockle.

Range in Park and PacificFound at only one site in KATM.Pribilof Islands, Gulf of Alaska,Prince William Sound, south toSonoma County, California.

Cardiidae

Low-rib cockle, left valveexterior (after Foster 1991).

24

Rightvalves of

subadultbasketcockle.

Basket Cockleor Nuttall Cockle(Clinocardium nuttallii)

DescriptionShell large, thick, inflated; maturespecimens decidedly longerposteriorly, with beaks nearerposterior end; younger specimensmore equilateral; with about 30-35strong rounded, radial ribs, eachtopped with crescent-shaped nodescrossed by commarginal riblets; ribsweak at posterior end. Hinge platenarrow; teeth prominent; innermargin deeply crenulate.Periostracum thin. Shell coloryellowish grey to brown; interiorwhite, often with yellowish blush.Length to 146 mm (5.7 in).

HabitatMuddy and sandy habitats from lowintertidal zone to 180 m (591 ft).Lives with posterior end of shells justbelow the surface of the sediment.Colonies sometimes dense.

Significant PredatorsSea otters, gulls, and starfish.

CBasket Cockleor Nuttall Cockle(Cli di tt llii)


Left andrightvalves ofadultbasketcockle.

Range in Park and PacificObserved in several locations inKATM and KEFJ. Large specimenscommon in earlier studies in LACL.Punuk Islands, near St. LawrenceIsland; Dutch Harbor, UnalaskaIsland; through Gulf of Alaska southto San Diego, California. WesternPacific Ocean from Kamtschatka toHokkaido Island, Japan.

Cardiidae

Basket cockle, left valveexterior (after Foster 1991).

Posteriorview ofvalvessubadult ofbasketcockleshowingdistinguish-ingcharacters.

Largest of the North

Pacific cockles. Lives

up to 16 years.

25

Veneridae

Lord dwarf-venus, rightvalve exterior (after Foster1991).

Lord dwarf-venus, left valveinterior (after Foster 1991).

Lord Dwarf-Venus(Nutricola ?lordi)

DescriptionShell small, white, thick, smooth,trigonal or subtrigonal, moderatelyinflated. Sculpture of commarginalstriations but shell and periostracumbrilliantly polished. Umbonesprominent. Ligament slightlyprotruding. Hinge with three cardinalteeth on each valve, but no lateralteeth. Pallial sinus shallow, pointed.Length to 10 mm (0.4 in).

HabitatMixed-soft habitats from intertidalzone to 20 m (66 ft).


Lord Dwarf-Venus(Nutricola ?lordi)


Range in Park and PacificObserved at only one location inKATM and few in KEFJ.Southeastern Bering Sea, Cook Inletsouth to Punta Pequeña, BajaCalifornia.

26


DescriptionShell subovate to subquadrate,inflated, distinctive cancellatesculpture, with radial andcommarginal ribs. Lunule obscure;escutcheon narrow, in left valve only.External color creamish to brown,sometimes with brownishmaculations and zigzag markings.Inner shell margins finely crenulate.Hinges each with three cardinalteeth, no lateral teeth. Pallial sinusdeep. Length to 80 mm (3.2 in), butusually to 40 mm (1.6 in).

HabitatBurrows up to 20 cm (8 in) deep insemi-protected mixed-soft, sand,sandy-mud habitats from lowerintertidal zone to 10 m (33 ft).


Littleneck clam, right valveexterior (after Foster 1991).

Three medium-sizedlittleneck clams showingscale.

Range in Park and PacificCommon at a few sites in KATM andat numerous sites in KEFJ. AttuIsland in the Aleutians through Gulfof Alaska and Prince William Sound,south to Bahia Santa Maria, BajaCalifornia. Western Pacific from theCommander Islands south toHokkaido, Japan.

Littleneck clam, left valveinterior (after Foster 1991).

Littleneck Clamor Pacific Littleneck Clam(Protothaca staminea)

VeneridaeLittleneck and butter clams

are very important prey

for sea otters and for

human subsistence. They

live at least 15 years.

Littleneck and butter clams

are the “redwoods” in

mixed-soft sediments.

27


DescriptionShell white, solid, thick, ovate-subquadrate, moderate gape atposterior end. Lunule andescutcheon absent. Externalsculpture consists mostly of heavygrowth lines only, although fine,closely spaced, irregularcommarginal ribs can sometimes beobserved. Periostracum thin, lightbrown, frequently worn. Olderspecimens may be stained darkgrey. Ligament conspicuously large,brown. Hinge has three cardinalteeth; one small or no anterior lateraltooth. Inner shell margin is smooth.Pallial sinus deep. Dark-tippedsiphon can be retracted into the shellonly with difficulty. Shell length to136 mm (5.4 in).

HabitatBurrows up to 35 cm (14 in) deep insemi-protected mixed-soft, sand,sandy-mud, or mud habitats fromlower intertidal zone to 40 m (131 ft).


Butter clam, right valveexterior (after Foster 1991).

Butter clam, left valveinterior (after Foster 1991).

Butter Clamor Washington Butter Clam(Saxidomus gigantea)

Range in Park and PacificObserved to be common at severallocations in KATM and numeroussites in KEFJ. Seward Peninsula,Alaska to Kodiak; Kachemak Bay,Cook Inlet; Prince William Soundsouth to Capitola, California.

Right valve exterior of butterclam showing typical dark tipof siphon extending fromshell.

VeneridaeButter clams, largest of

the hardshell clams in

Alaska, live up to 20 years.

28


Posterior view of butter clam showing gapingvalves at posterior end and sand-covered siphonextending from shell.

Butter Clam (continued)(Saxidomus gigantea)

Dorsal view of butter clam showing large externalligament typical of this clam.

Veneridae

29

Turtoniidae

Minute turton, left valveexterior (after Foster 1991).

Minute Turton(Turtonia minuta)

DescriptionShell thin, fragile, inflated, ovate.Central slope stained red to purple.Sculpture of faint commarginalgrowth lines mark outer surface.Periostracum thin. Hinge platenarrow; two teeth in right valve,three in left; weak posterior lateralteeth present in both valves. Interiorof shell light brown. Pallial line weakbut continuous, without pallial sinus.Length to 3 mm (0.1 in).

HabitatRocky and mixed-soft habitats inthe intertidal zone. Attached toepibiota, especially algae, by byssalthreads.


Minute Turton(Turtonia minuta)


Range in Park and PacificObserved at several locations inKATM but only one in KEFJ.Circumboreal; Nunivak Island, St.Paul Island, Pribilof Islands, south inthe Aleutians to Amchitka Island;Prince William Sound south toBarkley Sound, Vancouver Island,British Columbia. Western Pacificfrom Kurile Islands to Honshu,Japan. Minute turton, left valve

interior (after Foster 1991).

Group of adult minuteturtons showing small size.

30


DescriptionShell large, heavy, white, slightlyangular outline, narrowly subovate,longer posteriorly; exterior smoothbut often eroded externally. Low,wide ridge on the shell's innersurface; anterior lateral hinge teethshort, very weak to obscure; pallialsinus moderate, extending two-thirds distance to anterior adductormuscle scar. Periostracum heavy,grey-green, olive to dark brown,usually eroded, or, in smallerspecimens, yellow. Interior is pinkor white with red or yellow patches.Length to 130 mm (5.1 in).

HabitatShallow burrower (up to 15 cm [6 in]deep) in exposed sandy or silty-sandhabitats from lower intertidal zone to100 m (328 ft).


Alaska great-tellin, rightvalve exterior (after Foster1991).

Range in Park and PacificObserved at only a single site inKATM. Frequently observed onexposed sandy beaches in LACLduring other studies. AmericanArctic coast, Chukchi and BeringSeas, to Cook Inlet, Alaska.Western Pacific from Kamchatka tonorthern Japan and Korea.

Alaska great-tellin, left valveinterior (after Foster 1991).

Alaska Great-Tellin(Tellina lutea)

Tellinidae

This is the largest

tellin in Alaska.

31


Exterior of the valvesof the Alaska great-tellin.

Interior of thevalves of the Alaskagreat-tellin.

Alaska Great-Tellin (continued)(Tellina lutea)

Tellinidae

32


DescriptionShell inflated, thick for size,subtrigonal. Sculpture absent, withoccasional growth checks.Periostracum polished, glossy greygreen and yellow. Lateral teethprominent, only a hint of internal rib.Entire shell pink to white, with pinkblotches, sometimes with externalcommarginal red banding; interiorpink and orange. Length to 20 mm(0.8 in).

HabitatShallow burrower in exposedmedium to coarse sand habitatsfrom lower intertidal zone to 75 m


Salmon tellin, right valveexterior (after Foster 1991).

Salmon tellin, left valveinterior (after Foster 1991).

Salmon Tellin(Tellina nuculoides)

Range in Park and PacificObserved only at a few sites inKATM. Southeastern Bering Seaout to Attu Island in the Aleutians;Cook Inlet south to CoronadosIslands, northern Baja California.

Group of valves showing pinkcolor on interior and exteriorand external growth checksfor salmon tellin.

Tellinidae

33

Group of Baltic macomasshowing pink, yellow, andwhite color variants.

Baltic Macoma(Macoma balthica)

DescriptionShell pink, red, yellow, or white,ovate to subovate to subtrigonal,subequilateral, moderately inflated;posterior end rounded to pointed,anterior end rounded. Periostracumoften abraded. Pallial sinuses inboth valves equal in size, deep;pallial line and sinus are confluent.Length to 45 mm (1.8 in), usuallyless than 30 mm (1.2 in).

HabitatModerately shallow burrower (up to20 cm [8 in] deep) in sandy mud tosilty mud in somewhat protected tomoderately exposed habitats withreduced salinity from mid intertidalzone to 40 m (131 ft). Aconspicuous, abundant resident ofmud flats due to feeding tracks.

Significant PredatorsShorebirds, diving sea ducks,flatfish.

Baltic Macoma(Macoma balthica)


Range in Park and PacificCommonly observed andwidespread in muddy habitats inKATM, KEFJ, and LACL. Panarcticand circumboreal. Beaufort Sea toSan Francisco, California. WesternPacific from Arctic south to Japan. Baltic macoma, left and

right interior (after Coan1971).

Individual pink coloredBaltic macoma.

Tellinidae The Baltic macoma was, by

far, the most abundant

macroinfaunal clam species

observed in the SWAN parks.

34


Characteristic stellate feeding tracks from Baltic

Straight movement tracks formed by parasitizedBaltic macomas.

Tellinidae

Baltic Macoma (continued)(Macoma balthica)

35


DescriptionShell thin, subovate, subequilateralto slightly longer posteriorly, slightlyinflated; anterior end rounded,posterior end rounded to slightlyproduced, without dorsal flange.Periostracum shiny, adherent.Pallial sinuses moderate, about thesame size in both valves; pallial lineconfluent with pallial sinus for abouthalf its length. Length to 51 mm (2in).

HabitatProtected or exposed sand andsandy mud flats from mid intertidalzone to 30 m (98).


Exterior of right and leftvalves of expanded macoma.

Range in Park and PacificObserved at three sites in KATM andonly one site in KEFJ. NunivakIsland, Bering Sea, south to AttuIsland in the Aleutians, and toOceano, California.

Expanded macoma, left andright interior (after Coan1971).

Expanded Macoma(Macoma expaansa)

Tellinidae

36


DescriptionShell ovate to round, heavy, inflated,anterior end longer; posterior endacute, rounded to slightly truncate.Periostracum dark, usually worn.Pallial sinus deep in left valve,moderate in right; pallial line in rightvalve detached from pallial sinus forabout half its length; in left valve,pallial line and sinus are slightlydetached or confluent. Length to 50mm (2 in).

HabitatProtected mixed-soft and silty sandhabitats; gravel and sand from lowerintertidal zone to 200 m (656 ft).


Exterior of left valve of ovalmacoma.

Oval macoma, left and rightinterior (after Coan 1971).

Oval Macoma(Macoma golikovi)

Range in Park and PacificCommonly observed in both KATMand KEFJ. Point Barrow, Alaskasouth to Puget Sound, Washington.Western Pacific from Sakhalin Islandto Sea of Japan.

Posterior end of oval macomashowing characteristic flexureof valves.

Tellinidae

37

Interior and exteriorappearance of pointedmacoma.

Pointed Macoma(Macoma inquinata)DescriptionShell elongate-ovate to subovate,moderately inflated; inequilateral,posterior end longer, produced;slight indentation in ventral margin isdistinctive. Pallial sinuses in bothvalves very deep, about equal inlength, confluent. Length to 66 mm(2.6 in).

HabitatProtected mixed-soft habitats orsandy mud flats from lower intertidalzone to 50 m (164 ft).


Pointed Macoma(M i i t )


Range in Park and PacificObserved at few sites in KATM andseveral sites in KEFJ. PribilofIsland, Bering Sea, south to AtkaIsland in the Aleutians; south toSanta Barbara and Mugu Lagoon,California.

Pointed macoma, left andright interior (after Coan1971).

Right valve exterior ofpointed macoma.

Tellinidae

38


Tellinidae

Bent-Nose Macoma(Macoma nasuta)

DescriptionShell narrowly subovate,subequilateral; posterior endproduced, longer than anterior,distinctly bent to the right. Pallialsinus in left valve extremely deep,merging with anterior adductormuscle scar; deep in right valve;pallial sinus and pallial line areconfluent for their entire lengths.Length to 110 mm (4.3 in), usuallyless than 75 mm (3 in).

HabitatBurrows up to 20 cm (8 in) deep inprotected or exposed sandy or siltymud flats or mixed-soft sedimentsfrom lower intertidal zone to 50 m(164 ft).

Significant PredatorsMoon snails.

Range in Park and PacificUncommon, observed on only onelocation in KATM. Cook Inlet andPrince William Sound, Alaska,south to Punta Rompiente, BajaCalifornia.

Bent-nose macoma, ventralexterior.

Bent-nose macoma, dorsalexterior (after Coan 1971).

Bent-nosed macoma, leftand right interior (afterCoan 1971).

39


DescriptionShell heavy, thin when small;anterior end short, rounded;posterior end rounded.Periostracum glossy, thick, light oliveto dark brown. External shell colorwhite, with a central radial brownband, and commarginal brownbands when small; internal colorwhite to purple or purplish brown.Internal rib relatively narrow, nearlyvertical. Vertical interior rib androunded posterior end distinguishthis species from Siliqua patula.

HabitatExposed to semi-exposed sand orsilty-sand habitats from mid intertidalzone to 85 m (279 ft).

Significant PredatorsBrown bears, sea otters, andhumans. Harvested for subsistenceand once commercially in KATM.

Alaska razor clam, left valveexterior (after Foster 1991).

Range in Park and PacificObserved on several sandy beachesonly in KATM. Chukchi and BeringSeas south to Cold Bay, AlaskaPeninsula; Cook Inlet, Alaska, southto Point Conception, California.Western Pacific from KamchatkaPeninsula south to northern Japan.

Alaska razor clam, rightvalve interior (after Foster1991).

Alaska Razor Clam(Siliqua alta)

Pharidae

40


Exterior of valves of Alaskarazor clam showing shinyperiostracum.

Interior of valves ofAlaska razor clamshowing nearlyperpendicular angle ofinternal rib.

Razor clam shows inintertidal beach sand.

Alaska Razor Clam (continued)(Siliqua alta)

Pharidae

41

On the sand flats, the razor

clams, active diggers requiring

sediments that can easily be

liquefied in order to dig or

rebury, appear to represent the

climax community. They are

relatively long-lived (at least 19

years) and can be considered the

“redwoods” of the sand flats.

Pacific razor clam, leftvalve exterior (after Foster1991).

Pacific Razor Clam(Siliqua patula)

DescriptionShell thin; anterior end rounded,proportionately longer than in othereastern Pacific species; posteriorend slightly quadrate. Periostracumadherent, thick, glossy, highlypolished, light to dark olive to darkbrown or purple. External shell withradial purple pattern on beaks;internally white to purple. Internalradial rib anteriorly directed,becoming wider from umbones.Overall, this species is longer withrespect to its height than Siliqua alta.Length to 190 mm (7.5 in).

HabitatBurrow deeply (at least 50 cm [20in] into exposed or semi-exposedsandy or silty-sand habitats fromlower intertidal zone to 85 m (279ft).

Significant PredatorsBrown bears, sea otters, andhumans. Harvested commerciallyand for subsistence in LACL.

Pacific Razor Clam(Siliqua patula)


Range in Park and PacificObserved at only one site in KATMbut commonly observed on exposedsand beaches in LACL. Cook Inlet,Alaska, south to Morro Bay,California.

Pacific razor clam, rightvalve interior (after Foster1991).

Pharidae

42


Exterior of valves for Pacific razor clam showing shinyperiostracum.

Interior of valves for Pacific razor clam showing anteriorly angledinternal rib.

Pacific Razor Clam (continued)(Siliqua patula)

Pharidae

43


Mactridae

Arctic Surfclam(Mactromeris polynyma)

DescriptionShell smooth, broad oval or trigonal-elongate, moderately compressed;subequilateral; posterior sloperounded, not set off; gape atposterior end narrow. Periostracumolive, tan to dark brown, shiny,rugose. Hinge distinctive, with aninternal ligament betweenchondrophores and inverted v-shaped teeth; pallial sinus short.Length to 155 mm (6.1 in).

HabitatBurrows at least 30 cm (12 in) intoexposed or semi-exposed sandy orsilty-sand habitats from lowerintertidal zone to 110 m (361 ft).

Significant PredatorsSea otters.

Range in Park and PacificPeard Bay, Beaufort Sea; throughoutBering Sea; Cook Inlet and Gulf ofAlaska south to Puget Sound,Washington. Western Pacific in Seaof Okhotsk and KamchatkaPeninsula.

Arctic surfclam, right valveexterior (after Foster 1991).

Arctic surfclam, left valveinterior (after Foster 1991).

44


Surfclam shells indicatingdense surf clam bed.

Surfclam shows on exposedsand bar.

Mactridae

Arctic Surfclam (continued)(Mactromeris polynyma)

Right valve exterior of youngArctic surfclam.

Right valve interior young ofArctic surfclam.

Right valve exterior of olderArctic surfclam.

45

On the sand flats, Arctic

surfclams have similar status to

the razor clams. They are long-

lived clams and also appear to

represent the climax community

of sand flats.

Young Pacific gaper clam,left valve exterior.

Pacific Gaper(Tresus nuttallii)

DescriptionShell ovate-elongate, longerposteriorly and more evenly curvedventrally than T. capax, with onlyslightly produced ventral margins insome specimens; posterior endtruncate, gape broad.Chondrophore medium in size,posteriorly directed. Siphons cannotbe retracted into shell; with terminalperiostracal plates, which are lackingin T. capax. Shell length to 225 mm(8.9 in).

HabitatBurrows up to 1 m (39 in) deep intoprotected sandy or muddy habitatsfrom mid intertidal zone to 80 m (262ft).

Significant PredatorsSea otters and starfish.

Pacific Gaper(Tresus nuttallii)


Range in Park and PacificObserved at several locations inKATM. Kodiak Island, Alaska, southto Bahia Magdalena, Baja California.

Young Pacific gaper clam,left valve interior.

MactridaeGapers are the largest

clams living in this region.

The fat gaper (Tresus

capax) is probably more

common in this region

than the Pacific gaper but

living specimens are

difficult to collect and

shells were not confirmed

during the surveys in

SWAN parks.

46


Myidae

Softshell Clam(Mya arenaria)

DescriptionShell thin, white, ovate-elliptical;posterior end produced, attenuate;anterior end narrow. Posterior endpointed, anterior end, rounded.Periostracum thin, dehiscent, lightbrown. Chondrophore withoutanterior buttress. Pallial linedetached from pallial sinus; sinus ofmoderate depth, extending to orslightly beyond beaks. Length to170 mm (6.7 in).

HabitatBurrows down at least 25 cm (10 in)into protected to semi-protectedsandy to muddy mud flats in mid tolower intertidal zone. Generallyabundant where observed.

Significant PredatorsBrown bears, sea otters.

Range in Park and PacificObserved very commonly in KATMand LACL, but in only a few sites inKEFJ. Circumboreal. Icy Cape,Alaska, southern Bering Sea andYukon Delta; Alaska Peninsula,Cook Inlet, and south to ElkhornSlough, California. Western Pacificto Korea, Kurile Islands, andnorthern Japan.

Softshell clam, right valveexterior (after Foster 1991).

Softshell clam, left valveinterior (after Foster 1991).

47

Softshell clams are

relatively long-lived and

achieve large size, have a

broad spectrum of habitat

and food acceptability,

tolerate a wide range of

environmental conditions

such as salinity and

temperature, and are

considered good

colonizers.


Softshell clam shows on mudflat.

Group of excavated softshellclams lying on boulder.

Right valve exterior ofsoftshell clam.

Chondrophore on left valve ofsoftshell clam.

Right exterior and leftinterior valves of softshellclam.

Myidae

Softshell Clam (continued)(Mya arenaria)

48

On mud flats, it is likely that

long-lived softshell clams are

indicators of the climax

assemblage in stable substrate

(the “redwoods” of the mud

flats). In areas where they are

absent, sediments are probably

too disturbed.


False Softshell Clam(Mya pseudoarenaria)

Myidae

DescriptionExternally similar to M. arenaria.Pointed anterior end and sharplyrounded to slightly attenuateposterior end. Chondrophore withanterior buttress. White shell has alight brown periostracum. Details ofthe hinge and pallial line and sinusseparate this species from M.arenaria. Pallial sinus extending toor slightly past umbones, mostlyconfluent with pallial line. Length to110 mm (4.3 in).

HabitatProtected mixed-soft, sandy, ormuddy habitats from lower intertidalzone to 50 m (164 ft).

Significant PredatorsProbably brown bears and seaotters.

Range in Park and PacificObserved at several locations inKATM and KEFJ. Point Barrow,Beaufort Sea, Alaska, throughout theBering Sea; Cook Inlet. WesternPacific south to northern Japan.

False softshell clam, rightvalve exterior (after Foster1991).

False softshell clam, leftvalve interior (after Foster1991).

49


Truncate Softshell Clam(Mya truncata)

Myidae

DescriptionShell subquadrate, inflated; posteriorend abruptly truncate to broadlyrounded. Squarish posterior is uniqueto this species. Sculpture consists ofnumerous commarginal undulationsand growth lines. Chondrophore withanterior buttress. Shell is chalky whitewith papery brown, thick, dehiscentperiostracum, which bridges ventralgape and forms a siphonal sheath.Siphon cannot be retracted into shell.Pallial sinus extending to beaks,broad, confluent with pallial line topartly detached. Shell length to 86mm (3.4 in).

HabitatBurrows down at least 25 cm (10 in)into silty-sand to sandy- or silty-mudhabitats. Lower intertidal zone to 100m (328 ft).

Significant PredatorsProbably brown bears and sea otters.

Range in Park and PacificObserved at only one site in KATMand several sites in KEFJ. Has beenobserved on mud flats in LACL inother surveys. Circumboreal,panarctic. Point Barrow, BeaufortSea, through Chukchi and BeringSeas, Cook Inlet south to PugetSound, Washington. Western Pacificsouth to northern Japan.

Truncate softshell clam,right valve exterior (afterFoster 1991).

Truncate softshell clam, leftvalve interior (after Foster1991).

Right exterior valve andsiphon of truncate softshell.

50

Arctic hiatella, left valveexterior (after Foster 1991).

Arctic Hiatella(Hiatella arctica)

DescriptionShell white, oblong, often distorted,rough, irregular; sculpture of irregularcommarginal growth lines. Umbonesprominent, near anterior end. Small,distinct lunule present. Ligamentattached to short nymph.Periostracum thin, dark, dehiscent;not covering siphon, which may bewhite- or red-tipped. Pallial line ispatchy, discontinuous, with a shallowpallial sinus. Juveniles have twosmall hinge teeth in the left valve andone in the right; adults lack them.Shell length to 78 mm (3.1 in), butgenerally less than 50 mm (2 in).

HabitatNestling in a variety of habitatsincluding rock, especially mixed-softhabitats; burrowing in gravelly mud inmussel beds. Often attached to hardsurfaces with byssal threads. Midintertidal zone to 1,190 m (3,904 ft).


Arctic Hiatella(Hiatella arctica)


Range in Park and PacificObserved at numerous sites inKEFJ, absent in other parks.Cosmopolitan. Point Barrow,Beaufort Sea, throughout the BeringSea, Gulf of Alaska, Prince WilliamSound, south to Chile.

Arctic hiatella, right valveinterior (after Foster 1991).

HiatellidaeArctic hiatellas are widely

recognized as a very successful

colonizing species, among the

first clam species to appear in

disturbed sediments or new

habitats. The specimens

observed are generally highly

variable and probably comprise

more than one species.

Group of Arctic hiatellasshowing right and leftvalves and dorsal andventral sides of valves.

51


Adductor muscle:

Anterior:

Attenuate:Beak:

Bifid:Buttress:

Byssus:

Cancellate:

Cardinal teeth:

Circumboreal:

Chondrophore:

Commarginal:Commensal:Compressed:Conchiolin:

Confluent:Crenulate:Dehiscent:Dentition:Dorsal:Edentulous:Equilateral:Escutcheon:

Muscles connecting the two valves together andused to close or draw them together. Typically, clams in this guidehave an anterior and a posterior adductor muscle.

The front end of a clam, where the mouth and foot aretypically located.

Gradually tapering.The pointed end of the shell above the hinge; the part of the

shell formed first; earliest part of the umbo.Divided in two; forked.

A structure providing support between the hinge and thechondrophore.

Tough conchiolin fibers produced by the foot of somebivalves for attachment to rocks, other bivalves, or other surfacesupon which they live.

Sculpture on exterior of shell a network of both radialand concentric (commarginal) ribs.

Primary teeth projecting laterally from the vicinity ofthe hinge directly below the beaks.

Found throughout cold-water regions south of theArctic, i.e., from Bering Strait to about Point Conception,California.

A large, laterally projecting spoon-like tooth thatsupports an internal ligament. Typically matched with a pit on theopposing valve.

Concentric, parallel to the shell margins.Lives with a host organisms.Flattened, of reduced thickness.

A proteinaceous substance forming byssal threads andthe periostracum covering the exterior of shells

Joined, flowing together.Finely toothed or notched edge.Readily peeling off.

Tooth structure on the hinge plate.The shell margin nearest the hinge.

Lacking teeth.Anterior and posterior ends of shell of about length.A lozenge-shaped indentation on the dorsal surface

of the shell posterior to the beaks, often bordered by a ridge ofshell.

Glossary

52


Flammule:Hinge:

Hinge plate:

Hirsute:Inequilateral:

Lateral teeth:

Ligament:

Lunule:

Mantle:

Muscle scars:

Non-serrate:Orbicular:Orthogyrate:Ovate:Pallial line:

Pallial sinus:

Panarctic:Periostracum:

Posterior:

Flame-shaped color pattern in shell.The point on the dorsal surface of the two valves of a clam

at which they articulate. Generally includes supporting structuressuch as teeth or chondrophores of variable sizes.

The infolded dorsal margin of a valve on which theteeth are found.

Hairy, with short hairs.With umbones displaced from the center of the shell

toward either the posterior or anterior end of the valves so thatone end is longer than the other.

Hinge teeth anterior to and posterior to the cardinalteeth.

A horny elastic structure joining the valves togetheralong the dorsal surface and causing the valve to gape open whenthe adductor muscles relax.

A heart-shaped area on the dorsal margin anterior of thebeaks.

The fleshy outer layer of a molluscan body that secretes itsshell and periostracum, and, in bivalves, forms the tubular foldsthat constitute the siphons.

Impressions on the interior surface of the shellscaused by the attachment of adductor and other muscles.

Smooth; not notched or saw-toothed.Orb-shaped or rounded in outline.

Beaks pointed toward each other.Egg-shaped or oval.

A light scar on the inner surface of the valves generallybetween the adductor muscle scars resulting from the attachmentof the muscles at the edge of the mantle.

Indentation in the pallial line indicating where themantle has retreated to accommodate the retractor muscles forthe siphons.

Distributed throughout the Arctic Ocean.The outermost leathery or parchment-like layer of a

clam shell formed from the proteinaceous material, conchiolin.The back end of the clam; the end containing the

siphons, pallial sinus, and ligament.

Glossary

53


Produced:Quadrate:Radiate:

Resilifer:

Resilium:

Sculpture:

Siphon:

Striation:

Subequilateral:Subovate:Subquadrate:Taxodont dentition:

Trigonal:Umbo (plural umbones):

Valve:

Ventral:

Drawn out, elongated.Rectangular or squarish.

Radiating from the umbo or beak toward the ventralmargin of the shell.

Structure supporting the resilium. Sometimes a tooth,sometimes a socket.

The internal ligament connecting the hinges of the rightand left (opposing) valves.

Patterns of raised or incised ribs on the external surfaceof the valves.

Tube-like projection from the ventral end of the mantlethrough which water is drawn or expelled from the mantle cavity.Siphons are separate in some clams (e.g., macomas) and joinedon others (butter clams, cockles, and gapers).

Fine scratch, groove, or line, sometimes representing agrowth check.

Nearly equilateral.Nearly ovate.

Nearly quadrate.A row of fine teeth of similar size and shape

along the hinge plate found in more primitive clams.Somewhat triangular in outline.

Viewed from the outer surface of a valve,the projecting, curved structure on the dorsal surface, includingthe beak and first-developing part of the shell.

Right or left shell of the two shells that are characteristic of abivalve.

The side of the shell opposite the hinge and dorsalsurface; the bottom of the shell.

Glossary

54


Bennett, A. J., W.L. Thompson, and D.C. Mortenson. 2006. Vitalsigns monitoring plan, Southwest Alaska Network, Inventoryand Monitoring Program. National Park Service. Anchorage, AK.125 pp.

Coan, E. V. 1971. The Northwest American Tellinidae. Veliger 14Supplement. 63 pp.

Coan, E. V., P. Valentich Scott, and F. R. Bernard. 2000. BivalveSeashells of Western North America; Marine Bivalve Mollusksfrom Arctic Alaska to Baja California. Santa Barbara Museumof Natural History. Santa Barbara, CA. 764 pp.

Foster, N. R. 1991. Intertidal Bivalves: A guide to the commonmarine bivalves of Alaska. Univ. of Alaska Press. Fairbanks,AK. 152 pp.

Keen, M., and E. Coan. 1974. Marine Molluscan Genera ofWestern North America. Stanford Univ. Press. Stanford,CA. 208 pp.

Lees, D. C., and W. B. Driskell. 2004. Annual Report for NationalPark Service Intertidal Reconnaissance Survey to AssessComposition, Distribution, and Habitat of Marine/EstuarineInfauna Inhabiting Soft Sediments in the Southwestern AlaskaNetwork - Kenai Fjords National Park and Lake Clark NationalPark and Preserve. Prepared by Littoral Ecological &Environmental Services for Southwest Alaska Network, NationalPark Service. 40 pp.

Lees, D. C. and W. B. Driskell. 2006a. Annual Report for NationalPark Service Intertidal Reconnaissance Survey to AssessComposition, Distribution, and Habitat of Marine/EstuarineInfauna Inhabiting Soft Sediments in the Southwestern AlaskaNetwork - Katmai National Park and Preserve. Prepared byLittoral Ecological & Environmental Services for SouthwestAlaska Network, National Park Service. 34 pp.

Literature Cited

55


Lees, D. C. and W. B. Driskell. 2006b. Intertidal ReconnaissanceSurvey to Assess Composition, Distribution, and Habitat ofMarine/Estuarine Infauna in Soft Sediments in the SouthwestAlaska Network. Prepared by Littoral Ecological & EnvironmentalServices for Southwest Alaska Network, National Park Service.95 pp.

Morris, R. H., D. P. Abbott, and E. C. Haderlie. 1980. IntertidalInvertebrates of California. Stanford University Press. Stanford,CA. 690 pp.

Smith, T. S. and S. T. Partridge. 2004. Dynamics of intertidalforaging by coastal brown bears in Southwestern Alaska.Journal of Wildlife Management. 68(2):233–240.

Yonge, C. M. 1960. Oysters. Collins. London. 209 pp.

Literature Cited (continued)

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