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Overview of the Sumner Clam Research Program and Description of 2018 Research Plans

Authors:
Bill Zoellick at Schoodic Institute at Acadia National Park
Bill Zoellick
  • Schoodic Institute at Acadia National Park
Students from Sumner Memorial High School
Students from Sumner Memorial High School
Students from Sumner Memorial High School
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Abstract

The Sumner Memorial High School (SMHS) Clam Research program is designed to provide opportunities for students to learn by engaging in authentic scientific work. Equally important, it aims to help the towns that it serves – currently, Steuben and Gouldsboro – manage softshell clam resources In the fall of 2017, SMHS students assisted the Maine Department of Marine Resources and the Downeast Institute in the collection and processing of softshell clam samples from a number of sites in Steuben and Gouldsboro. In addition, students began work on repurposing an abandoned lobster pound for use as a research site. SMHS students have prepared other posters for presentation at the Maine Fishermen’s Forum that describe the lobster pound repurposing and present findings from a study of clam settlement. In this poster, we step back to take a broader view of the project. We describe the purposes the project is intended to serve, outcomes from the 2017 work, and plans for the 2018 season.
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Outcomes from 2017 Work!
SMHS Pathways students assisted in collecting the DMR’s
John Small Cove data (see the poster titled “A Study of Clam
Settlement in John Small Cove”) and also helped Kyle
Pepperman of DEI collect data from sites in Steuben and
Gouldsboro. The DEI studies used 6” plastic pots containing
a known number hatchery clams (Beal et al., 2001; 2002) and
found that:!
• Clam settlement and growth varied across different sites.!
• There were places where there was a lot of settlement
even though there were few adult clams due to predation.!
The John Small Cove study, which is described in detail in
the “Study of Clam Settlement” poster, considered high tide
and low tide locations in addition to the effect of protective
netting. As illustrated in Figure 1, settlement boxes covered
by water for more time had more clams and larger clams.!
The findings from the DEI studies, when considered together
with the John Small Cove data, suggest that:!
• Crab predation can kill most of the clams in an area.!
• There can still be good settlement in places without mature
clams.!
• Nets can make a difference.!
• To get a good measures of clam settlement and growth we
need to do everything possible to keep crabs out of the
boxes used to measure settlement.!
• It might be possible to grow clams so that they are big
enough to avoid crab predation (shell length > 30 mm
according to Beal et al. (2016)) by locating clam “nurseries”
so that they are submerged most of the time.!
These ideas became the basis for planning the work we will
do in 2018 in the research area that the students are creating
on the site of an abandoned lobster pound.
Introduction!
In the fall of 2017 students from Sumner Memorial High
School (SMHS) assisted the Maine Department of Marine
Resources (DMR) and the Downeast Institute (DEI) in the
collection and processing of softshell clam samples from
a number of sites in Steuben and Gouldsboro. In
addition, students began work on repurposing an
abandoned lobster pound for use as a research site.!
SMHS students have prepared other posters for
presentation at the Maine Fishermen’s Forum that
describe the lobster pound repurposing and present
findings from a study of clam settlement.!
In this poster we step back to take a broader view of the
project. We describe the purposes the project is intended
to serve, outcomes from the 2017 work, and plans for the
2018 season.
!
Purpose
The SMHS Clam Research program is designed to
provide opportunities for students to learn by engaging in
authentic scientific work. Equally important, it aims to
help the towns that it serves – currently, Steuben and
Gouldsboro – manage softshell clam resources. Some of
the help comes in the form of extra hands to help with
conservation work on the clam flats. But the program
also assists towns by developing and deploying data
collection methods and protocols that students can use
to answer important questions such as:!
• Where is clam settlement most abundant?!
• What is the rate of clam growth and where is growth
the fastest?!
• Where is predation most aggressive and destructive?!
Answers to these questions will be different for each bay,
cove, or other site that a town manages. Knowing how
sites differ will help towns manage the clam fishery.!
Once Schoodic Institute learns how to do this well with
SMHS and the towns that it serves, we will work toward
expanding the program to other towns and schools.
!
Acknowledgments!
This project draws upon the skills, talents, and know-how
of teachers, students, town shellfish committees, the
Maine DMR, and the Downeast Institute. Financial
support is provided by the Elmina B. Sewall Foundation
through the Whole Schools, Whole Communities initiative
within the ELLMS (Environmental Living and Learning for
Maine Students) network.!
Plans for 2018!
Our goals for he 2018 season are to:!
• Investigate the relationship between the amount of
time that clams are underwater and the rate of
growth. (We will use the new gate on the research
pound to vary water levels.)!
• Investigate the effect of using protective netting
with different mesh sizes (4.2 mm, 6.4 mm, 12.8 mm)
on settlement.!
• Create and test a working prototype of an easy-to-
deploy clam settlement collector that towns can use
to compare clam settlement at different sites.!
• Develop methods for collecting information about
green crab density and life cycle at different sites.!
Our aim is to develop standardized protocols that other
schools and towns can use to collect data about clams
and clam predators in their own clam flats. By 2019 we
hope to have curriculum materials and teacher
professional development to accompany the protocols,
along with a means for towns and schools to share the
data that they are collecting about clam populations,
settlement, and growth along the Maine coast.!
For more information contact Bill Zoellick at the Schoodic
Institute: !
bzoellick@schoodicinstitute.org!
Bill Zoellick - Schoodic Institute#
Students from Sumner Memorial High School Pathways Program
Research Resources
Abraham, B. J., & Dillon, P. L. (1986). Species Profiles: Life Histories and Environmental
Requirements of Coastal Fishes and Invertebrates (Mid-Atlantic): Softshell Clams (No. Biological
Report 82(11.68)). National Wetlands Research Cener, Fish and Wildlife Service
Beal, B. F. (2006). Biotic and Abiotic Factors Influencing Growth and Survival of Wild and Cultured
Individuals of the Softshell Clam (Mya Arenaria L.) in Eastern Maine. Journal of Shellfish
Research, 25(2), 461–474.
Beal, B. F., & Kraus, M. Gayle. (2002). Interactive effects of initial size, stocking density, and type of
predator deterrent netting on survival and growth of cultured juveniles of the soft-shell clam, Mya
arenaria L., in eastern Maine. Aquaculture, 208(1), 81–111.
Beal, B. F., Nault, D.-M., Annis, H., Thayer, P., Leighton, H., & Ellis, B. (2016). Comparative, Large-
Scale Field Trials Along the Maine Coast to Assess Management Options to Enhance
Populations of the Commercially Important Softshell Clam, Mya arenariaL. Journal of Shellfish
Research, 35(4), 711–727. http://doi.org/10.2983/035.035.0401
Beal, B. F., Parker, M. R., & Vencile, K. W. (2001). Seasonal effects of intraspecific density and
predator exclusion along a shore-level gradient on survival and growth of juveniles of the soft-
shell clam, Mya arenaria L., in Maine, USA. Journal of Experimental Marine Biology and
Ecology, 264(2), 133–169.
Tan, E. B. P., & Beal, B. F. (2015). Interactions between the invasive European green crab,
Carcinus maenas (L.), and juveniles of the soft-shell clam, Mya arenaria L., in eastern Maine,
USA. Journal of Experimental Marine Biology and Ecology, 462, 62–73.
!
Overview'of'the'Sumner'Clam'Research'Program'
and'Description'of'2018'Research'Plans
Figure'1.'Differences'in'the'distribution'of'clam'size'at'lower'and'higher'positions'
along'the'tidal'gradient.'Boxes'covered'by'water'more'of'the'time'contained'more'
clams'and'larger'clams.
Background
Drawing on research undertaken by the Downeast
Institute, U.S. Fish and Wildlife Service, and others (see
the list of Research Resources), the students and adults
in this project approach this work in the context of rapid
ecological changes in Maine’s clam fishery. In particular,
we begin with the assumption that control of green crabs
and other predators is essential to management of the
fishery. It is within that context that we inquire into local
variation and opportunities with regard to clam settle-
ment, clam growth, and predation control.
!
ResearchGate has not been able to resolve any citations for this publication.
Comparative, Large-Scale Field Trials Along the Maine Coast to Assess Management Options to Enhance Populations of the Commercially Important Softshell Clam, Mya arenaria L.
Article
Full-text available
  • Dec 2016
During the past 40 y, commercial production of softshell clams,Mya arenaria, in the soft-bottom intertidal zone in Maine, United States, has decreased nearly 75%whereas dockside revenues have increased ca. 200%. The fishery is comanaged by coastal communities (some individually, some working together as a regional unit) and the state of Maine acting through its Department of Marine Resources. A number of shellfish management tools are available to clammers and stewardship committees to help increase or improve harvests. One of these, used by some communities, is the "conservation closure." This is when large acres of mudflats (sometimes≥200) are closed to harvesting and fallowed for periods as long as a year because either the area is no longer productive, too few legal size clams (≥50.8-mm shell length) exist, or the community wishes to practice some direct measure to improve harvests such as transplanting clams from one area of the intertidal to another. A series of comparative, large-scale manipulative experiments were conducted at each of two intertidal mudflats in three geographically distinct coastal communities along the Maine coast during 2014-2015 to examine potential management tools for areas closed for conservation purposes. Specifically, tests were conducted to determine the efficacy of using plastic predator-deterrent netting (18.21 m²; 4.2- or 6.4-mm aperture) to enhance: (1) recruitment of 0-y class wild juveniles, (2) survival of greater than or equal to 1-y class wild juveniles, and (3) wild stocks using cultured juveniles. Findings demonstrated that indiscriminate placement of nets did not result in consistent enhancement of wild recruits (occurring once in 12 trials). Survival of greater than or equal to 1-y class individuals was not enhanced in netted versus control plots at any of the six sites in 2014, but occurred in four of six sites in 2015. Cultured clam survival (May to October 2015) at the four sites where nets functioned properly varied from 65% to 100% and was independent of aperture size; however, where siltation was heavy ormud snails [Tritia (=Ilyanassa) obsoleta] deposited massive numbers of egg capsules on the nets (both scenarios resulting in anoxic conditions in the protected plots), survival ranged from 0% to 48%. Average annual and wintertime seawater temperatures in the Gulf of Maine have risen gradually during the past two decades, and this has been accompanied by increases in clam predators such as the invasive European green crab, Carcinus maenas. In this climate, conservation closures or other large-scale, indirect shellfish management tools cannot be effective in creating new wealth or maintaining jobs associated with the clam fishery in most areas. Therefore, to adapt to changes and increase diversification in the clamming industry in Maine, clammers should be encouraged to farm small (ca. ≤ 10 acres) intertidal tracts where netting and other predator-deterrent measures can be maintained easily and routinely, and where exclusive rights to harvest the farmed shellfish are granted to the individual.
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Biotic and abiotic factors influencing growth and survival of wild and cultured individuals of the softshell clam (Mya arenaria L.) in Eastern Maine
Article
Full-text available
  • Jan 2009
A series of intertidal field experiments was conducted from 1986–2003 in eastern Maine to examine biotic and abiotic factors influencing the growth and survival of wild and cultured individuals of the softshell clam, Mya arenaria L. Separate experiments examined: (1) the efficacy of transferring sublegal wild clams (<50.8 mm SL) from areas near the high intertidal zone where shell growth was slow to areas where growth was predicted to be faster; (2) effects of tidal height on wild and cultured clam growth; (3) effects of spatial variation on cultured clam growth; (4) dispersion and growth of cultured juveniles in small experimental units; (5) effects of the naticid gastropod, Euspira heros Say, predation on survival of wild and cultured clams and (6) the species composition of large, crustacean predators that forage intertidally during periods of tidal inundation. Protective netting (4.2 mm aperture) increased recovery rate of transferred clams by 120% and resulted in a 3-fold enhancement of wild recruits. Effects of tidal height on wild clam growth revealed complex behaviors in >0 y-class individuals. Clams growing near the upper intertidal take >8 y to attain a legal size of 50.8 mm SL, whereas animals near the mid intertidal generally take 4.5–6.5 y. Unexpectedly, clams initially 38–54 mm SL and growing near the extreme low tide mark at a mud flat in Eastport, Maine, added, on average, <2 mm of new shell in a year, which was 8–10 mm SL less than animals at higher shore levels. It is hypothesized that biological disturbance by moon snails, that consumed >90% of clams at the low shore levels, contributed to this slow growth. In another field trial from 1986–1987, moon snails and other consumers were allowed access to clams ranging in size from 15–51 mm. E. heros preyed on clams over the entire size range and attacked clams between 31–40 mm at a rate that was nearly double what had been expected. Mean snail size was estimated to range from 10–52 mm shell height (SH), based on a laboratory study that yielded information about the linear relationship between snail size and its borehole diameter. In an experiment from June to September 1993, moon snails consumed >70% of juvenile clams (ca. 10 mm SL) within a month after planting at each of three tidal heights. Snail sizes ranged from 15–20 mm SD with larger individuals occurring near the upper intertidal zone. Green crabs, Carcinus maenas (L.) also prey heavily on softshell clam populations, but most studies that use shell damage to assign a predator have assumed that all crushing and chipping predation is because of this invasive species. An intertidal trapping study demonstrated that both green crabs and rock crabs, Cancer irroratus Say, are present during periods of tidal inundation, with the latter species accounting for ca. 40% of large crustacean numbers.
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Species profiles: Life histories and environmental requirements of coastal fishes and invertebrates (Mid-Atlantic): Softshell clam.[Mya arenaria]
Article
  • Aug 1986
The softshell clam supports the third most valuable commercial clam fishery in the United States. Density is highest at depths of 3 to 4 m, temperatures less than 28/sup 0/C, and salinities greater than 3 ppt. Its near-shore habitat makes it easily threatened by pollution. Clam beds in some places have been closed because of contamination by bacteria. Softshell clams are more sensitive to oil pollution than are the other clams that share its habitat. The softshell clam spawns in spring (sometimes in early summer) and again in fall. In 36 to 48 h after fertilization, a pelagic veliger larva develops and persists for 2 to 6 weeks. Then it settles out of the plankton. It attaches to the substrate and can move and reattach itself. Eventually, it adopts the adult lifestyle and occupies a permanent burrow, usually in sandy bottom with less than 50% silt. Adult clams feed by filtering small particles from the water column. Predators of adult clams include crabs, fish, birds, and raccoons. The 24-h LC/sub 50/ values for summer-acclimated clams have been reported as 32.5 to 34.4/sup 0/C. Juveniles and adults can withstand long periods of anaerobiosis.
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Seasonal effects of intraspecific density and predator exclusion along a shore-level gradient on survival and growth of juveniles of the soft-shell clam, Mya arenaria L., in Maine, USA
Article
  • Sep 2001
  • J EXP MAR BIOL ECOL
The relative roles that predation and competition play in regulating populations of infaunal marine bivalves in soft-bottom systems are strikingly different. Exploitative competition for food typically occurs at elevated densities, but crowding rarely results in mortality and competitive exclusion. Predation by decapods, gastropods, and, sometimes asteroids, is more important in controlling patterns of distribution and abundance. Most field tests leading to this synthesis have been conducted between 35°N and 35°S and/or with bivalves in the families Veneridae and Tellinidae. To test the robustness of these ecological processes at another geographic setting (45°N) using a species from another family within the suspension-feeding guild (Myidae), we performed a short-term field manipulation at an intertidal mud flat in eastern Maine, USA. We followed survival and growth of 10,080 juveniles (12.4-mm shell length (SL)) of the soft-shell clam, Mya arenaria L., in field enclosures with and without predator-deterrent netting at three densities (330, 660 and 1320 m−2) along a tidal gradient over four sampling intervals from April to December 1996. We used a generalized completely randomized block design to assess variation in these dependent variables within a given tidal height (high, mid, and low) on a particular date.
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Interactive effects of initial size, stocking density, and type of predator deterrent netting on survival and growth of cultured juveniles of the soft-shell clam, Myaarenaria L., in eastern Maine
Article
  • May 2002
  • AQUACULTURE
Recent declines in commercial harvests of soft-shell clams, Myaarenaria L., in Maine, USA, have prompted state and local officials to consider enhancing wild stocks with hatchery-reared seed. We conducted two manipulative field experiments in the soft-bottom intertidal zone during 1990–1991 in eastern Maine to assess effects of predation, intraspecific competition, and initial planting size on the survival and growth of cultured individuals of Mya.Experiment I (23 June 1990 to 13 June 1991) tested interactive effects of two planting sizes (small=8.5 mm shell length (SL); large=11.8 mm SL) and protective netting on fate and growth of clams. Animals of each size were added to separate experimental units within each of 60 1-m2 areas delimited by a wooden box. To deter predators, 50 boxes were covered with a specific type of plastic netting that differed in aperture size (4.2, 6.4 and 12.8 mm) and degree of rigidity (flexible vs. extruded) while 10 boxes served as controls (without netting). Small clams grew at a faster rate than large clams, but both added approximately 18 mm of new shell by the end of the study. Growth was unaffected by netting size and rigidity, but 13% more clams were recovered alive after a year in protected vs. unprotected treatments (84% vs. 71%). Survival was independent of netting type. The presence of netting resulted in nearly a 3× enhancement of wild spat (<15 mm SL) compared to unprotected controls (568.8±24.4 vs. 199.6±22.8 m−2). This result suggests that the decline of wild stocks in eastern Maine may not be related to recruitment failure, but to post-settlement events, such as predation, which remove clams from the intertidal.In Experiment II (15 April to 6 October 1991), clam (14.6±0.2 mm SL) density was manipulated across four levels from 333 to 2664 m−2 in protected (extruded netting, 12.8 mm aperture) and unprotected 1-m2 boxes. Survival within unprotected boxes was independent of stocking density (79%), but was inversely density-dependent in protected boxes (77% in the lowest density treatment increasing to a mean of 88% in the other three treatments). A negative cubic relationship explained the effect of density on growth.We present the first mariculture strategy for public stock enhancement or private entrepreneurs interested in rearing M. arenaria in Maine and the northeast US. Hatchery-reared juveniles 8–10 mm SL should be planted in the spring near or below mid tide levels at densities between 333 and 666 m−2 and protected with flexible netting (6.4 mm aperture) raised several centimeters above the sediment surface. Netting should be removed from mud flats in the late fall before the threat of ice and severe winter storms. Animals should attain sizes between 25 and 30 mm SL during this time and reach a size refuge from burrowing and other predators. Growth to legal, commercial size (50.8 mm SL) should take another 2–4 years depending on geographic location and mean seawater temperature.
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