1

Cohort structure and habitat association of the Pinna nobilis

population in Northern Corsica at STARESO

Kenan Chan & Emma Chiaroni

Abstract

The Mediterranean fan mussel, Pinna nobilis can grow to be over a meter in length and

are typically found half submerged in the sand within Posidonia oceanica. In recent years, P.

nobilis has been under increasing pressure due to collection and habitat destruction. Previous

studies have examined P. nobilis population structure elsewhere in the Mediterranean, however,

our study investigated the specific demographics of the population at STARESO Marine

Research Station, located on the Northern coastline of the French island of Corsica. We created

an equation that enabled non-lethal age determination based on the maximum width of the

individual. Our study was based on principles of the intermediate disturbance hypothesis and

aimed to quantify environmental disturbances. We looked at depth and substrate as an indicator

of disturbance, with shallower regions being more exposed to high wave action and composed of

rocky substrate. We found evidence that suggest that P. nobilis associates with the

environmentally stable P. oceanica meadows at STARESO and that there exists distinctive

cohorts within the population.

Introduction

The intermediate disturbance

hypothesis (IDH) predicts that levels of

species diversity will be maximal in

environments experiencing intermediate

levels of disturbance (Aronson et al 1995,

Connell 1978, Connell 1979, Sousa 1979).

Elevated disturbance environments favor

species with high reproductive capacity and

low competitive ability, whereas low

disturbance environments allow for some

species to become competitively dominant,

causing the formation of a climax

community (Connell 1979).

Although the IDH was based off

terrestrial ecological succession, it can be

applied to the marine environment.

Environmental disturbances in the marine

environment manifest in the form of

hydrodynamic forces, shifting substrate and

anthropogenic activity. In order to develop

conservation strategies there must be

scientific knowledge on the effects of

environmental disturbances on species

assemblage and diversity (Richardson et al.

2004).

The Mediterranean fan mussel,

Pinna nobilis, can grow to be over a meter

in length and is typically found half

submerged in the sand within Mediterranean

seagrass, Posidonia oceanica, (Katsanevakis

et al. 2008). Fundamental knowledge of P.

nobilis biology is limited, however, studies

have revealed a depth-related size

segregation (Garcia-March et al. 2007 A, B).

Studies performed off the Mediterranean

coast of Spain suggest that smaller P. nobilis

were found in sandy sheltered areas and

rocks at shallow depths, while large

individuals were are found to be associated

with P. oceanica meadows at deeper levels

(Garcia-March et al. 2007 A). There is also

2

little knowledge about the recruitment of P.

nobilis, however evidence suggests that

settlers recruit over a depth gradient. The

majority of settlement occurs in late autumn

and winter (Garcia-March et al. 2007 A,

Richardson et al. 2004).

Habitat destruction, pollutants, and

collection have caused P. nobilis to be listed

as an endangered species in the

Mediterranean (Richardson et al. 1999,

Richardson et al. 2004). P. nobilis used to be

widely distributed within the shallow coastal

waters of the Mediterranean, but in recent

years, increases in anthropogenic activity,

including the development of resorts and the

destruction of P. oceanica meadows, have

caused P. nobilis populations to decline.

Expanding on the limited scientific

knowledge of P. nobilis ecology will aid in

making informed decisions regarding the

protection of this species. This study

investigated the role of environmental

disturbance, by using depth as a proxy for

disturbance, with the age related segregation

of individuals within the P. nobilis population

on the Northern coast of Corsica at the

STARESO Marine Research Station. Our

study looked at four main hypotheses: (1)

Does the STARESO Pinna nobilis population

show cohort structure; (2) Do P. nobilis show

a substrate preference with respect to cobble,

boulder, sand, and P. oceanica; (3) Do P.

nobilis show an association for more stable

communities (3a) Is there a positive

association with deeper depths; (3b) Does the

age vary between the different subregions at

STARESO; North, Harbor and South; and (4)

Is there a shared trend in orientation between

individuals?

METHODS

Study Area

STARESO Marine Research Station

is located on the Northern coastline of the

French island of Corsica. The station is a

relatively protected site allowing for the

observation of species that inhabit the

prolific sea grass meadows. There is a small

breakwater that creates a shallow sheltered

boat harbor. To the North and South of the

station are steep cliffs that line the coastline,

creating unique geological formations

including cobble fields and vertical walls.

We used SCUBA for all aspects of

the field data collection. In order to find

individual P. noblis previously found in the

2012 BIOE 159 course, permanent transect

lines were set up in three locations (Map);

(1) the STARESO harbor (2) North of the

STARESO harbor and (3) South of the

STARESO harbor. All transects were set up

to replicate those established in 2012

(Elsmore and McHugh 2012). The Harbor

transect extended from the ladder within the

harbor (N42.58026, E8.72418), to a

permanent PVC pipe (N42.57988,

E8.72449) 50 meters out at a heading of 150

degrees. The North transect extended 85

meters from the North PVC pipe

(N42.58004, E8.72499) inshore (N42.58075,

E8.72503) at a total distance of 85 meters.

The South transect ran between the South

PVC pipe offshore (N42.57951, E8.72475)

and continued for 60 meters (N42.57934,

E8.72410) inshore. The shallowest end of

each transect was assigned meter mark 0.

3

Map: Map of STARESO with 3 permanent transects

(marked in red), North individuals (blue) Banana

individuals (purple), Harbor individuals (yellow) and South

individuals (green) plotted in Google Maps.

Each of the three study locations had

their own distinguishing features. The

Harbor’s substrate included cobble and

boulders, man-made jacks, and P. oceanica

patches. Depth ranged from 0 to about 10m.

The North location was lined with large

boulders and cobble mounds that dropped

off quickly to a P. oceanica dominated

landscape. The North location also included

a few unique formations dubbed the

Bananas for their sickle, banana-like shape.

The Bananas were regions where P.

oceanica receded away from bare sand due

to erosion. The South was composed of

steep rocky walls that met contiguous P.

oceanica meadows. Both the North and

South study sites typically sloped from 5 to

20 m offshore.

General Data Collection

To test whether P. nobilis abundance

and age are higher in areas of low

disturbance, we recorded the depth,

maximum exposed length, submerged length

(figure 1),

Figure 1: Total length, maximum exposed length and

submerged length shown.

orientation, arc thickness, maximum width

(figure 2B), distance from transect and

meter-mark on the permanent transect for

each found individual. Depth was measured

by placing a dive computer where the

mussel met the substrate (depth

measurements were taken using the Imperial

system due to our dive computers settings).

A.

B.

Figure 2A/B: Figure 2A depicts the measurement of the

arc width while Figure 2B shows the maximum width.

The maximum exposed length and

maximum width were measured with rulers

while the submerged length (figure 1) was

4

measured with a PVC pipe that was inserted

into the substrate until it met resistance

(submersion technique), where the byssal

threads of the P. nobilis meet the rhizomes

(Richardson et al 1999).

Orientation was determined with a

compass, using reciprocal headings along

the margin where the two valves meet. The

thickness of the valves was measured with

calipers from the top of the P. nobilis valves

(figure 2A). A meter tape was used to

measure the distance from the permanent

transect line to the mussel.

We used this data to run a Binomial

Probability test with a critical p-value of

0.05 to determine if a difference existed

between shallow and deep depth zones. To

determine the average age of the mussels at

each location, we ran an ANOVA test using

a critical p-value of 0.05 in JMP Pro 11

(JMP Pro 11 was used in all subsequent

statistical tests). To test for a shared

orientation between individuals at

STARESO, we used a Chi-Squared test with

a critical p-value of 0.05.

Once the mussels were sized and

their positions noted, GPS coordinates were

taken for each individual via a float and

surface support. We then plotted GPS

coordinates using Google Earth and Google

Maps to visualize the distribution of the

mussels.

Habitat Association

In order to quantify P. nobilis habitat

association with certain substrates, we

carried out Uniform Point Contact (UPC)

surveys at each mussel using 9 total points

on a 1 square meter PVC quadrat (figure 3)

(note: center mark placeholder was always

P. nobilis individual). This data was then

used with a wider spread UPC data set1 to

1 An expansive UPC data set was conducted by J. Harrison, L. Hernandez, and E. Williams that consisted of both onshore and

offshore transects every 10 meters at each of the 3 permanent transect (appendix 1).

run a Chi-Squared test in to test for an

association. We set our critical p-value to

.05.

Figure 3: 1m² with 9 UPC points.

Demographics: Pinna nobilis age

distribution and cohort structure at

STARESO

In order to relate age to a

morphometric measurement, we established

a total length to maximum width

relationship using measurements collected

from dead P. nobilis. Shells collected for

this purpose ranged from 11.8 cm to 69.5

cm. Total length, maximum width, shell

thickness, arc length, shell volume, adductor

scar length, and adductor scar ring (figure 4)

number were recorded.

Figure 4: Adductor mussel scars on the internal side of a P.

nobilis valve. Photo: Kenan Chan

By graphing measurements of total length

against maximum width from the dead

individuals, the following linear relationship

was determined:

5

Equation 1

Total Length = 2.8836 (Max Width) – 5.5516

The total length of each live P.

nobilis was determined using Equation 1,

and then compared to the lengths obtained

by the submersion technique practiced in the

field. Total length and maximum width data

were utilized in constructing a von

Bertalanffy growth equation for the

STARESO population. The von Bertalanffy

growth equation:

𝐿(𝑡) = 𝐿∞(1 − 𝑒−𝑘(𝑡−𝑡0))

Drawing upon previous studies on P.

nobilis age and growth (Richardson et al

1999), the upper limit was set as the largest

individual in the population; a dead

individual from STARESO with a total

length of 69.5cm. The growth constant k

was determined through the relationship

between total length and the number of

adductor scar rings. Adductor scar rings

acted as a measurement of age (Richardson

et al 1999, Richardson et al 2004). 𝑡0 is the

age at which the organism is size zero; this

was set as the youngest and smallest

individual, which was a dead individual

from the STARESO harbor, that was 3 years

old and 11.8 cm in total length. By

customizing the von Bertalanffy growth

equation to the STARESO P. nobilis

population, we produced Equation 2.

Equation 2

𝑊(𝑡) =[69.5(1 − 𝑒−0.1823(𝑡−3))] + 5.5516

2.3836

𝑤ℎ𝑒𝑟𝑒 𝑊 𝑖𝑠 max 𝑤𝑖𝑑𝑡ℎ 𝑎𝑡 𝑡𝑖𝑚𝑒 𝑡 (𝑦𝑟𝑠)

To determine the age distribution of

the STARESO population, Equation 2 was

rearranged to solve for age as a function of

maximum width. This allowed for field

measurements of maximum width to be

converted into age as displayed in Equation

3 below. In the past, P. nobilis had to be

removed from the substrate to examine the

adductor muscle scar rings in order to

determine age. The examination of the

adductor muscle scar rings necessitated the

lethal removal of the animal from its valves.

The von Bertalanffy equation developed in

this study is a non-lethal tool that allowed us

to obtain estimates of age.

Equation 3

𝑡 =𝑙𝑛 [1 −

(2.8836𝑊 − 5.5516)69.5 ]

−0.1823+ 3

𝑤ℎ𝑒𝑟𝑒 𝑊 𝑖𝑠 max 𝑤𝑖𝑑𝑡ℎ

The results of Equation 3 were input

into JMP to create a histogram displaying

the age distributions. This allowed for the

identification of possible cohort structure

within the STARESO P. nobilis population.

To analyze the age distribution produced by

Equation 3, we ran a cluster analysis.

Results

Pinna nobilis Cohort Structure at

STARESO

Through the use of the modified von

Bertalanffy equation, we were able to

establish an estimated age for each of the P.

nobilis individuals. We were then able to

group them into cohorts. Four distinct

cohorts were found (Appendix 2). The first

cohort ranged from approximately 3-6 years,

the second from 8-11 years, the third from

12-15 years, and the last cohort ranged from

approximately 20-22 years. Using a cluster

analysis in JMP (figure 5), we could see

how the cohorts were divided and the

relative sizes of each cohort.

6

Figure 5: P. nobilis cohorts at STARESO. Each separate

cohort is separated by a different color. The cohort age

increases from top to bottom.

The general age distribution of the entire

STARESO population was graphed (figure

6) and showed peaks and valleys, indicative

of cohort structure.

Figure 6: Age structure of the mussel population. Number

of individuals in each age class vs. Years (age).

Habitat Association of Pinna nobilis at

STARESO

We found that the mussels showed a

stronger association with P. oceanica than

with any other substrate or primary

placeholder (sand, boulder, and

cobble) (Chi-Square: 122.65, df: 3, P<

.0001). The expected P. oceanica count was

162.45, normalized from the general UPC

data1, but the observed value was much

higher at 239 observations. With boulder,

we found the opposite, with an expected of

88.57 and only 3 observed points. The

observed values for sand and cobble were

consistent with the expected values. Cobble

had 16 observed points and an expected of

14.35 points while sand had 22 observed

points and an expected 14.6 points.

Depth and Age Distribution with Respect

to Disturbances

We ran a Binomial Probability test

between shallow (0-25ft) and deep (26-50ft)

depth zones using a critical p-value of 0.05

and yielded a significant p-value of 0.04.

We determined that the mussels exhibited a

higher association with the deeper depth

zone (26-50ft).

Using an ANOVA we tested the ages

of individuals with respect to the location.

We found the North individuals to be

significantly older (P=.0486, df:2) than the

individuals in the South and the Harbor

(figure 7) at an average age of 13.9 years

old.

Figure 7: Mean age of P. nobilis individuals at their

respective locations; North, Harbor, South.

Orientation of Pinna nobilis

We constructed a Mosaic Plot (figure 8) and

ran a Pearson Chi-Square Test (Chi-square:

7

2.48, df: 3, P= .7795) and found there to be

no trend in valve orientation. The expected

values for each 30 degree increment was

13.3 individuals.

Figure 8: Expected Quantity (left column) vs. Actual

Quantity (right column) of P. nobilis individuals who fall

under their respective 30-degree orientation range.

Discussion

Pinna nobilis Cohort Structure at

STARESO

In our study we were able to

construct a von Bertalanffy growth equation

for the STARESO Pinna nobilis population.

The results of the equation suggested that

the P. nobilis population at STARESO does

in fact display cohort structure (Appendix

2). Using maximum width as a measurement

for size (Katsanevakis 2005), we were able

to determine that larger individuals were

inherently older (Richardson et al. 1999).

Out of a total of 40 mussels, four

cohorts were identified: 3-6 years, 8-11

years, 12-15 years, and 20-22 years old. The

largest cohort was 8-11 years old. This

suggests that there may have been favorable

oceanographic conditions 8-11 years ago for

P. nobilis recruitment, such as an influx of

cold (~12°C) seawater at STARESO

(Richardson et al. 2004).

While we attempted to maintain

equal levels of effort when searching for

small and large individuals in the seagrass,

the density of P. oceanica during the study

period made it difficult to locate small

individuals. Smaller P. nobilis were easier to

find in areas with reduced seagrass cover.

The lower number of small individuals

involved our study could be a potential

source of error when investigating the

existence of the cohort structure. A study by

Katsanevakis (2005) investigated the size

frequency distribution of P. nobilis in a

Grecian marine lake. Katsanevakis

identified three size classes which

corresponded to three cohorts within the

lake population: maximum width 1-7 cm, 9-

15 cm, and 15-21 cm. Using Equation 3 to

convert maximum width into age, these

three size classes convert into the age groups

0-4 years, 5-7 years, and 7-12 years old. The

cohorts found by Katsanevakis are similar in

structure to the cohorts we found at

STARESO, suggesting that fluctuations in

P. nobilis recruitment may correspond to

environmental fluctuations (Richardson et

al. 2004.)

Habitat Association of Pinna nobilis at

STARESO

The UPC habitat association results

suggest that P. nobilis displays a strong

association with P. oceanica (Garcia-March

et al. 2007 A, B, Richardson et al. 1999,

Richardson et al. 2004). P. oceanica

meadows stabilize the hydrodynamic

environment by creating a dampening effect

from waves and currents. The P. nobilis that

inhabit P. oceanica meadows benefit from

the reduced water movement created by the

densely packed blades and are protected

from potentially harmful wave action

(Coppa et al. 2010, Hendricks et al.

Expected Quantity Actual Quantity

8

2011). Little is known about the settlement

processes of P. nobilis, but studies have

revealed that larva settle over a depth range.

This means that P. nobilis do not actively

settle on a specific substrate, but rather

suggests that post-settlement mortality is

lower on certain substrates. Since larva

settle over a range of depths, and therefore a

range of habitats, there must be certain

factors of P. oceanica that promote P.

nobilis survivorship.

The mussels displayed a strong

disassociation to boulder (expected: 88.57

and observed: 3). At STARESO, boulder

and cobble habitats were found in the

shallow depth zones. Due to their shallow

locations at STARESO, these substrates

make the mussels susceptible to wave

action. P. nobilis that settle in these shallow

substrates are more vulnerable to harmful

hydrodynamic activity than individuals who

settle in P. oceanica. The depth of the P.

oceanica beds at STARESO also plays a key

role in maintaining the stability of the

habitat.

Depth and Age Distribution with Respect

to Disturbances

In order to determine if P. nobilis

associates with stable environments, we

compared depth to mussel abundance, and

location (North, South, and Harbor) to P.

nobilis age. When comparing P. nobilis

abundance to depth, it was determined that a

higher number of the individuals studied at

STARESO reside within the 26ft-50+ ft

(~7.5-15+ m) depth zone. This depth range

corresponds our observed range of P.

oceanica at STARESO. The shallowest

depth limit of the sea grass (~5-6 m) is

restricted by wave action (Infantes et al.

2009). The distribution of mussels in terms

of depth supports the hypothesis that P.

nobilis associates with P. oceanica. By

associating with deeper water habitats, P.

nobilis is sheltered from potentially harmful

wave energy.

The results of the ANOVA test

confirmed that older animals inhabit the

North more so than the Harbor and the

South locations. The habitat in the North is

almost entirely composed of P. oceanica

meadows with the exception of sloping

boulders and a cement jack wall at the

border of the Harbor and North locations.

Older individuals associate more with the

North over any other location possibly due

to the region’s low levels of environmental

perturbation. Water movement decreases

with depth (Bryson 1961), making the

North, which was the deepest out of all three

locations, the most hydrodynamically stable

site. The low levels of environmental

disturbance created by the depth and the

dampening effect of P. oceanica, form a

favorable environment for reducing post-

settlement mortality of P. nobilis. By

associating with the hydrodynamically

stable P. oceanica in the North, P. nobilis

are less likely to be harmed by wave action

or shifting substrates allowing them to reach

older ages.

Orientation of Pinna nobilis

We investigated the presence of a

potential trend in valve orientation. Initially,

we predicted that the animals would orient

themselves to reduce drag as large P. nobilis

are commonly pulled out of the substrate

during storms (Coppa et al. 2010, Garcia-

March et al. 2007 B). We determined that

there was no trend in valve orientation. The

lack of a trend is likely due to the settlement

processes of P. nobilis (Cabanellas-

Reboredo et al. 2009,Garcia-March et al.

2007 A). When P. nobilis larvae settle in an

environment they likely settle in one

position for their entire life span. Some

changes in orientation may occur due to

shifting substrates; P. nobilis most likely

9

retains its original settlement orientation.

Although we found no trend in valve

orientation, an interesting follow up study

could examine the role of valve orientation

in reducing drag (Garcia-March et al. 2007

B). If the valve orientation of a P. nobilis

was parallel to water flow, then it should

possess better hydrodynamic efficiency than

a conspecific with a valve orientation that is

perpendicular to the water flow.

Conclusion

The results of our study make it

apparent that P. nobilis associates with P.

oceanica over any other habitat. By

comparing age structure and distribution

with habitat, it was revealed that

environmental stability plays a role in the

depth-age segregation described in previous

studies. Younger P. nobilis are more likely

to be associated with shallow high

disturbance habitats. Older P. nobilis are

strongly associated with deeper areas with

low levels of environmental perturbation.

While our study investigated an explanation

to the depth-size segregation, the mechanism

behind this pattern has yet to be determined.

When collecting data in the field, we noticed

that P. nobilis possessed a relatively uniform

distribution. It is possible that larva sense

chemical cues from adult P. nobilis that aid

in choosing an appropriate settlement habitat

(Kobak 2001, Thrush 1996). However, the

uniform distribution suggests the existence

of specific mechanisms that regulate the

number of individuals within a given area.

As mentioned previously, high levels of

post-settlement mortality in rocky shallow

habitats may add to the depth-size

segregation of animals.

The intermediate disturbance

hypothesis provides insight into the

distribution of P. nobilis at STARESO. Old

individuals associate with the most stable

environment at STARESO; the deeper water

P. oceanica meadows. Young animals

associate with shallow water areas with

diverse substrate assemblages such as the

harbor. Post-settlement mortality is

potentially lower in P. oceanica meadows,

therefore strengthening the association of P.

nobilis to P. oceanica. Because it is listed as

an endangered species, it is critical to

understand the population ecology of P.

nobilis for continued protection efforts.

Scientific knowledge about the habitat

associations of P. nobilis age groups is

important in making conservation decisions

to preserve and rehabilitate the species back

to original numbers.

References

Addis, P. et al. Density, size structure, shell orientation and epibiontic colonization of the fan mussel

Pinna nobilis L. 1758 (Mollusca: Bivalvia) in three contrasting habitats in an estuarine area of Sardinia (W

Mediterranean). Scientia Marina 73, 143-152, doi:10.3989/scimar.2009.73n1143 (2009).

Aronson, R. B. & Precht, W. F. Landscape patterns of reef coral diversity- A test of the intermediate

disturbance hypothesis. Journal of Experimental Marine Biology and Ecology 192, 1-14, doi:10.1016/0022-

0981(95)00052-s (1995).

Bryson, A. E. Film notes for waves in fluids. National Committee for Fluid Mechanics Films. Harvard

University. (1961)

Cabanellas-Reboredo, M. et al. Recruitment of Pinna nobilis (Mollusca: Bivalvia) on artificial

structures. Marine Biodiversity Records 2, e126, doi:10.1017/s1755267209001274 (2009).

10

Connell, J. H. Diversity in tropical rain forests and coral reefs - High diversity of trees and corals is

maintained only in a non-equilibrium state. Science 199, 1302-1310, doi:10.1126/science.199.4335.1302

(1978).

Connell, J. H. Intermediate-disturbance hypothesis. Science 204, 1345-1345,

doi:10.1126/science.204.4399.1345 (1979).

Coppa, S., Guala, I., De Lucia, G. A., Massaro, G. & Bressan, M. Density and distribution patterns of

the endangered species Pinna nobilis within a Posidonia oceanica meadow in the Gulf of Oristano (Italy).

Journal of the Marine Biological Association of the United Kingdom 90, 885-894,

doi:10.1017/s002531540999141x (2010).

Davenport, J. et al. Size-differential feeding in Pinna nobilis L. (Mollusca: Bivalvia): Exploitation of

detritus, phytoplankton and zooplankton. Estuarine Coastal and Shelf Science 92, 246-254,

doi:10.1016/j.ecss.2010.12.033 (2011).

Elsmore, K. and McHugh, T. Distributions of two sea urchins, Paracentrotus lividus and Arbacia

lixula, and their habitat associations in the Northwest Mediterranean at STARESO, Corsica France. Marine

Ecology Field Quarter. (2012)

A) Garcia-March, J. R., Garcia-Carrascosa, A. M., Cantero, A. L. P. & Wang, Y. G. Population

structure, mortality and growth of Pinna nobilis Linnaeus, 1758 (Mollusca, Bivalvia) at different depths in

Moraira bay (Alicante, Western Mediterranean). Marine Biology 150, 861-871, doi:10.1007/s00227-006-0386-

1 (2007).

B) Garcia-March, J. R., Perez-Rojas, L. & Garcia-Carrascosa, A. M. Influence of hydrodynamic

forces on population structure of Pinna nobilis L., 1758 (Mollusca : Bivalvia): The critical combination of drag

force, water depth, shell size and orientation. Journal of Experimental Marine Biology and Ecology 342, 202-

212, doi:10.1016/j.jembe.2006.09.007 (2007).

Garcia-March, J. R., Garcia-Carrascosa, A. M. & Pena, A. L. In situ measurement of Pinna nobilis

shells for age and growth studies: A new device.Marine Ecology-Pubblicazioni Della Stazione Zoologica Di Napoli I 23, 207-217, doi:10.1046/j.1439-0485.2002.02781.x (2002).

Garcia-March, J. R., Marquez-Aliaga, A., Wang, Y. G., Surge, D. & Kersting, D. K. Study of Pinna

nobilis growth from inner record: How biased are posterior adductor muscle scars estimates? Journal of Experimental Marine Biology and Ecology 407, 337-344, doi:10.1016/j.jembe.2011.07.016 (2011).

Hendriks, I. E., Cabanellas-Reboredo, M., Bouma, T. J., Deudero, S. & Duarte, C. M. Seagrass

Meadows Modify Drag Forces on the Shell of the Fan Mussel Pinna nobilis. Estuaries and Coasts 34, 60-67,

doi:10.1007/s12237-010-9309-y (2011).

Infantes, E., Terrados, J., Orfila, A., Canellas, B. & Alvarez-Ellacuria, A. Wave energy and the upper

depth limit distribution of Posidonia oceanica.Botanica Marina 52, 419-427, doi:10.1515/bot.2009.050 (2009).

Katsanevakis, S., Lefkaditou, E., Galinou-Mitsoudi, S., Koutsoubas, D. & Zenetos, A. Molluscan

species of minor commercial interest in Hellenic seas: Distribution, exploitation and conservation status.

Mediterranean Marine Science 9, 77-118 (2008).

Katsanevakis, S. & Thessalou-Legaki, M. Spatial distribution, abundance and habitat use of the

protected fan mussel Pinna nobilis in Souda Bay, Crete. Aquatic Biology 8, 45-54, doi:10.3354/ab00204

(2009).

Kobak, J. Light, gravity and conspecifics as cues to site selection and attachment behaviour of

juvenile and adult Dreissena polymorpha Pallas, 1771.Journal of Molluscan Studies 67, 183-189,

doi:10.1093/mollus/67.2.183 (2001).

Najdek, M., Blazina, M., Ezgeta-Balic, D. & Peharda, M. Diets of fan shells (Pinna nobilis) of

different sizes: fatty acid profiling of digestive gland and adductor muscle. Marine Biology 160, 921-930,

doi:10.1007/s00227-012-2144-x (2013).

Rabaou, L., Tlig-Zouari, S. & Hassine, O. K. B. Distribution and habitat of the fan mussel Pinna

nobilis Linnaeus, 1758 (Mollusca : Bivalvia) along the northern and eastern Tunisian coasts. Cahiers De

Biologie Marine 49, 67-78 (2008).

Richardson, C. A., Kennedy, H., Duarte, C. M., Kennedy, D. P. & Proud, S. V. Age and growth of the

fan mussel Pinna nobilis from south-east Spanish Mediterranean seagrass (Posidonia oceanica) meadows. Marine Biology 133, 205-212, doi:10.1007/s002270050459 (1999).

11

Richardson, C. A., Peharda, M., Kennedy, H., Kennedy, P. & Onofri, V. Age, growth rate and season

of recruitment of Pinna nobilis (L) in the Croatian Adriatic determined from Mg : Ca and Sr : Ca shell profiles.

Journal of Experimental Marine Biology and Ecology 299, 1-16, doi:10.1016/j.jembe.2003.08.012 (2004).

Sousa, W. P. Disturbance in marine inter-tidal boulder fields - The no-equilibrium maintenance of

species-diversity. Ecology 60, 1225-1239, doi:10.2307/1936969 (1979).

Thrush, S. F., Hewitt, J. E., Pridmore, R. D. & Cummings, V. J. Adult/juvenile interactions of infaunal

bivalves: Contrasting outcomes in different habitats. Marine Ecology Progress Series 132, 83-92,

doi:10.3354/meps132083 (1996).

Vafidis, D., Antoniadou, C., Voultsiadou, E. & Chintiroglou, C. Population structure of the protected

fan mussel Pinna nobilis in the south Aegean Sea (eastern Mediterranean). Journal of the Marine Biological Association of the United Kingdom 94, 787-796, doi:10.1017/s0025315413001902 (2014).

Appendix

Appendix 1: UPC map by J. Harrison, L. Hernandez, and E. Williams 2014. Transects done both onshore and offshore every 10

meters at each of the 3 permanent transect, North, Harbor and South.

Appendix 2: Cohort structure within the P. nobilis population at STARESO. Age based on derived equation is represented on the

x-axis and clustered cohorts are shown in the rows. The bar graphs are based off the total number of individuals at a given age.

Cohort age increase top to bottom.

12