The effect of sedimentation on the settlement behavior of the American lobster

choppedspleenMechanics

Feb 21, 2014 (3 years and 3 months ago)

77 views

Most

benthic

marine

invertebrates

have

a

complex

life

cycle

involving

a

pelagic

dispersal

phase

followed

by

a

benthic

settlement

phase
.

The

latter

is

often

dependent

on

preferred

substrate

availability
.


Lobster

settlement


During

stage

IV

(
postlarvae
)


Leads

to

a

behavioural

transition

:

pelagic

benthic/cryptic

(
Factor

1995
)


On

gravel

and/or

rocks

(
Botero

&

Atenna

1982
,

Pottle

&

Elner

1982
)


Ecosystem

modifications


Climate

change

:

Extreme

weather

events

more

frequent

(
IPCC

2012
)


Anthropic

activities

:

Agriculture,

waterway

dredging,




Sedimentary

load

and

regimes

affected

:



sedimentation

over

gravel

and

rocky

substrate









The effect of sedimentation on the settlement behavior of the American lobster

(
Homarus americanus
).

Benoit Bruneau & Gilles Miron

Université de Moncton, Moncton, Nouveau
-
Brunswick, Canada, E1A 3E9
















RESULTS AND DISCUSSION

INTRODUCTION


Botero,

L
.

and

Atema,

J
.

1982
:

Behavior

and

substrate

selection

during

larval

settling

in

the

lobster

Homarus

americanus
.

J
.

Crustacean

Biol

2
(
1
)
:

59
-
69


Factor,

R
.

J
.

1995
.

Introduction,

Anatomy,

and

Life

History
al

and

Postlarval

Ecology
.

p
.

1

11
.

In

Biology

of

the

Lobster

Homarus

americanus
.

l

R
.

Factor

(éd
.
)
.

San

Diego,

CA
:

Academic

Press
.

xiii

+

528

p
.


IPCC,

2012
:

Managing

the

Risks

of

Extreme

Events

and

Disasters

to

Advance

Climate

Change

Adaptation
.

A

Special

Report

of

Working

Groups

I

and

II

of

the

Intergovernmental

Panel

on

Climate

Change

[Field,

C
.
B
.
,

V
.

Barros,

T
.
F
.

Stocker,

D
.

Qin,

D
.
J
.

Dokken,

K
.
L
.

Ebi,

M
.
D
.

Mastrandrea,

K
.
J
.

Mach,

G
.
-
K
.

Plattner,

S
.
K
.

Allen,

M
.

Tignor,

and

P
.
M
.

Midgley

(eds
.
)]
.

Cambridge

University

Press,

Cambridge,

UK,

and

New

York,

NY,

USA,

582

pp
.



Miron

G,

L
.

J
.

Walters,

R
.

Tremblay

and

E
.

Bourget
.

2000
.

Physiological

condition

and

barnacle

larval

behavior
:

a

preliminary

look

at

the

relationship

between

TAG/DNA

ratio

and

larval

substratum

exploration

in

Balanus

amphitrite
.

Mar
.

Ecol
.

Prog
.

Ser
.

198
:

303

310


Pottle,

R
.
A
.

and

Elner,

R
.
W
.

1982
:

Substrate

preference

behavior

of

juvenile

American

lobsters,

Homarus

americanus
,

in

gravel

and

silt
-
clay

sediments
.

Can
.

J
.

Fish
.

Aquat
.

Sci
.

39
:

928
-
932

Literature cited

MATERIAL AND METHODS

1.
Postlarva:


Day 2, 3 and 4 of stage IV
postlarvae


Larva provided by the Coastal Zones Research
Institute (CZRI)


2.
Experimental Design:


4 types of substrate:

1.
Gravel (preferred lobster ground)

2.
Low Sedimentation over Gravel

3.
Medium Sedimentation over Gravel

4.
High Sedimentation over Gravel


4 replicates


1 hour focals (duration of observations)


Temperature is kept at 20˚C (rearing temperature)


Experiments carried out on each batch produced
(one batch presented)

3.
Measurements
:


Time budget:


time at 1) surface, 2) water column, 3) bottom


Cephalotorax

length, total weight


Lipid analysis (
Miron

& al.

2000
)

0
20
40
60
80
100
Bottom
Water
Column
Surface
Time budget (%)
D-2
Bottom
Water
Column
Surface
D-3
Bottom
Water
Column
Surface
D-4
Gravel
Low Sedimentation
Medium Sedimentation
High Sedimentation
Figure 1. Time Budget (%) for each larval age (D
-
2, D
-
3 and D
-
4) by treatment (Gravel, low sedimentation,
medium sedimentation, high sedimentation). Behaviors are related to larvae position in the aquarium (Bottom,
Water Column and Surface). Standard
-
errors are presented as upper intervals.

Surface
Water Column
Bottom
0
20
40
60
80
100
Observation Time (%)
Bottom
Water
Column
Surface
0
20
40
60
80
100
Time budget (%)
Figure 3. Time series of larvae age D
-
4 on high sedimentation substrate. Time budget is presented
as stacked barplot .

Surface
Water Column
Bottom
0
20
40
60
80
100
Observation Time (%)
Bottom
Water
Column
Surface
0
20
40
60
80
100
Time budget (%)
Figure 2. Time series of larvae age D
-
4 on gravel substrate. Time budget is presented as stacked
barplot.

1.
Age

(Figure

1
)

:


D
-
2
:

Surface

time

tend

to

decrease

as

sedimentation

levels

increase

while

time

spent

in

the

water

column

increases


D
-
4
:

Surface

time

tend

to

increase

as

sedimentation

levels

increase



D
-
2

and

D
-
4
:

Time

spent

on

bottom

tend

to

decrease

as

sedimentation

levels

increase


D
-
3
:

Patterns

show

no

trend


High

interindividual

variability


More

consistent

D
-
4

settlement

behaviours

2.
Substrate

(Figures 2 and 3)
:


Effect

of

substrate

type

is

more

apparent

for

D
-
4

larvae
.



Sedimentation

=

Total

bottom

time


Sedimentation

=


Frequency

of

bottom

contacts




Objectives
:



Determine

at

which

age

the

settlement

behaviour

is

best

developed

in

stage

IV

postlarvae
.


Measure

the

effect

of

sedimentation

over

preferred

substrate

on

the

settlement

behaviour
.

A

better

understanding

of

the

American

lobster

life

cycle

and

recruitment

processes

is

not

only

important

for

fishery

management

but

also

in

itself

as

part

of

an

ecosystemic

view

of

the

potential

effect

of

climate

change

on

benthic

populations

and

the

industries

that

depend

on

them
.



Larval

deposition

:


Critical

phase

of

the

life

cycle

-

Survival

increase


Affects

population

growth

and

sustainability


Sedimentation

:


Detrimental

on

settlement

behaviour

of

stage

IV

lobsters

(postlarvae)


Increase

in

sedimentation

leads

to

pelagic

behaviours

(ex
.

swimming)


Behaviours

better

defined

for

D
-
4

postlarvae


Behaviours

less

homogeneous

for

D
-
2

and

D
-
3

than

D
-
4

postlarvae

:

may

be

related

to

the

transition

between

pelagic

and

benthic

behaviours

(
Factor

1995
)


More

results

will

soon

be

available

to

complete

this

study
.

The

new

data

will

help

shed

some

light

on

the

different

behaviours

observed

among

stage

IV

postlarvae

aged

from

2

to

4

days

over

different

substrates

.


CONCLUSION