Transcript Statolith and gladius aging of the Southern Arrow Squid

Statolith and gladius
aging of the Southern
Arrow Squid
(Nototodarus sloanii)
Jean F. McKinnon
Department of Marine Science, University of
Otago
George D. Jackson
Institute of Antarctic and Southern Ocean
Studies, University of Tasmania.
Photo by Kerry Perkins
CIAC, Hobart, 2006
Introduction
• The statolith is the most commonly
used structure for ageing, life
history reconstruction and growth
studies. However, the gladius has
been investigated more recently as
a tool for age and growth studies.
Photo by Kerry Perkins
CIAC, Hobart, 2006
Aims
• To age N. sloanii using the statoliths.
• To develop a technique to read the
increments in the gladius.
• To create individual growth curves from
the gladius data.
CIAC, Hobart, 2006
Capture locations for squid
• Squid were collected from
commercial jigging operations
south-eastern
North
Island
West Coast
Canterbury
Otago
Catlins
A
South Snares
South
Island
D
I
K
P
N
H M
G E
J OC
F
Q
B
L
R
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NZ
during
Statolith aging
• Stage of maturity
was noted for
each squid
• Statoliths were
removed from
the statocyst
CIAC, Hobart, 2006
Statolith aging
• The right statolith was
used as a matter of
convention
• The statolith was
mounted on a
microscope slide,
ground on wet
carborundum paper and
polished with 0.05µm
Alumina on felt
• 281 statoliths were
polished (139 male and
142 female)
CIAC, Hobart, 2006
Photomicrograph by Jean McKinnon
Statolith aging
• The increments in the
dorsal dome of the
polished statolith were
counted using a camera
lucida
• To ensure accuracy the
increments were
counted three times for
each statolith with a
month between each
count. Each count had
to be within 10% of the
average to be
considered precise.
Typical Camera Lucida drawing of a statolith
(scale bar = 0.1mm)
CIAC, Hobart, 2006
Statolith aging results
• Squid ranged in age from 29 days to 206
days old.
• There was increase in size, (both mantle
length and weight) with increasing age, but
there was low correlation between age and
either mantle length or weight
• The log transformed slopes of the
regressions for log age versus log mantle
length were significantly different (p<0.05)
for male and female squid.
CIAC, Hobart, 2006
Statolith aging
400
r2= 0.491
350
300
250
200
150
100
50
0
0
50
100
150
200
50
800
600
400
200
0
250
150
200
250
100
150
200
250
200
250
r2= 0.2565
1200
1000
800
600
400
200
0
100
50
Age (days)
Total body mass
(g)
Dorsal mantle
length (mm)
1000
Male
r2= 0.2566
0
r2= 0.377
0
Age (days)
400
350
300
250
200
150
100
50
0
1200
Total body mass (g)
Dorsal mantle length
(mm)
Female
0
Age (days)
50
100
150
Age (days)
CIAC, Hobart, 2006
Statolith aging
• There was considerable overlap when the range of
ages was compared to stage of maturity (Table one).
On average, however, the more mature the squid was
the older it was.
Table one. Maturity stage and age range for Nototodarus sloanii (Males
and females combined
Maturity
Stage
Age Range
Days
Mean Age
days
Std Error
1
2
3
29-116
57-152
86-163
76.71
97.89
119.17
2.67
1.44
1.71
4
5
97-180
110-206
144.52
169.00
5.02
7.99
CIAC, Hobart, 2006
100
Percent of female maturity stages in each age
interval
90
5
25
25
25
25
25
Age at maturity
12
80
70
Mature
60
Maturing
Preparatory
50
Juvenile
Immature
40
Female
30
20
10
0
0-30
31-60
61-90
91-120
121-150
151-180
181-210
25
20
19
Age interval (days)
Percentage of male maturity stages in each age
interval
100
25
90
25
25
80
70
60
Male
50
40
30
20
10
0
0-30
31-60
61-90
91-120
Age interval (days)
121-150
151-180
181-210
CIAC, Hobart, 2006
Increment Validation
Photograph by Kerry Perkins
• Seven juvenile Nototodarus sloanii were caught in a light
trap off the Portobello Marine Laboratory Jetty.
• They were held in a 65L glass tank with flow through
seawater and were fed live zooplankton. They were left to
recover for twenty-four hours.
• The squid were transferred to a 10L bucket containing
calcein at a concentration of 0.5gcalcein/L seawater. They
were left in the bucket for two hours.
• After two hours, the animals were returned to the 65L
holding tank.
• The squid were checked several times a day and were fed
zooplankton in excess once a day.
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Validation
• Calcein was present in the statoliths of
five of the seven squid stained.
• The calcein band was indistinct and
incomplete.
CIAC, Hobart, 2006
Photomicrograph by Jean McKinnon
Validation
Modal Analysis
• A Modal analysis (Uozumi, 1998) was run on
the data collected from three of the Catlins
sites; Haldane 1, Haldane 2 and Haldane 3.
CIAC, Hobart, 2006
Validation
Location of samples used for
modal analysis
North
Island
South
Island
D
I
K
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Validation
• A length composition graph was
created for each sampling date where
length-frequency interval was taken for
every 10mm dorsal mantle length.
• The age of the squid from this sub
sample was regressed against sample
date.
CIAC, Hobart, 2006
Validation
• There was a gradual progression in the modes from
160mm DML to 220 mm DML between 22nd of
January and 30th of January 1999. This suggests
that the squid are from the same cohort.
30
25
22-Jan N= 90
25-Jan N=41
30-Jan N=32
15
10
5
Dorsal mantle length (mm)
CIAC, Hobart, 2006
281-290
271-280
261-270
251-260
241-250
231-240
221-230
211-220
201-210
191-200
181-190
171-180
161-170
151-160
141-150
131-140
0
121-130
Frequency
20
Validation
• The relationship between
the number of increments
and sampling date was
linear The equation for
the regression was
(r2
= 0.08, n = 56)
• The
relationship
was
significant at the 5% level
(ANOVA) The estimated
value of the slope is very
close to one, suggesting
that the periodicity of the
increments is daily
120
100
Number of increments
y = 1.0503 x + 4.0206
140
80
60
40
20
0
21-Jan
22-Jan
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23-Jan
24-Jan
25-Jan
26-Jan
27-Jan
Sampling date
28-Jan
29-Jan
30-Jan
31-Jan
Gladius aging
• The gladii were removed, dried under weight and
stored in labeled tissue paper in tall glass jars.
• 293 gladii were prepared for aging, by wiping the
surface with mineral oil.
• The increments were counted using a dissection
microscope with an adjustable fibre optic light
source.
• Counting criteria were the same as for the statoliths.
CIAC, Hobart, 2006
Gladius aging
• The measurements from the gladius were
used to reconstruct growth curves from the
oldest and youngest individual found at each
sample location.
• Only the increments from two individuals
from each location were measured as it is an
extremely time consuming procedure
• Because growth was extremely variable, the
curves were smoothed by calculating the
running mean
CIAC, Hobart, 2006
Gladius aging
• Gladius increments could be seen on the
central rib and lateral plate.
Increments
Central rib
Lateral plate
Lateral rib
Photomicrograph by Jean McKinnon
CIAC, Hobart, 2006
Gladius aging
• The counts were very similar to those of
the statolith from the same animal.
r2=0.997
150
Gladius age (days)
Gladius age (days)
r2=0.980
150
male
200
female
200
100
50
100
50
0
0
0
50
100
150
200
250
0
50
100
150
200
S tatoli th age (days )
S tatoli th age (days )
Statolith versus gladius increment counts
CIAC, Hobart, 2006
250
Gladius aging
• The growth curves showed a period of slow
growth ranging from 20 to 70 days long then
there may or may not be a period of faster
growth followed by a period of rapid growth.
• There was variation in this pattern which could
not be attributed to location or hatch season.
• Gender appears to be an important factor in the
growth rate of the squid.
• Female squid show growth curves with only a
short period of slow growth, male squid have a
longer period of slow growth.
CIAC, Hobart, 2006
Gladius aging
180
Female growth curve
A
160
140
Gladius increment growth (mm)
120
100
80
60
40
20
0
1
11
21
31
41
51
61
71
81
91
101 111 121 131 141 151 161
160
C
140
•Curves are from squid
from the same location,
with similar hatch
seasons and caught at
the same time.
120
100
80
60
40
Male growth curve
20
0
1
11
21
31
41
51
61
71
81
91
101
111
Gladius increment number
CIAC, Hobart, 2006
Discussion
• Previous research has found N. sloanii aged
up to 270 days, this study 206 days old
(mature at 6 months?).
• May have an ontogenetic migration
• Restricted sample period=> older animals
not present?
• Tropical squid often have life spans of less
than one year and mature earlier than
temperate species.
• Jackson et al (2000), found that N. sloanii
predominantly occur in warmer waters.
• Southland current has subtropical
characteristics.
CIAC, Hobart, 2006
Discussion
• The direct validation of the periodicity of the squid
statoliths using calcein was not a success, however
modal analysis suggests daily periodicity of the
growth increments.
• The juvenile squid in this study did not survive
longer than 48 hours.
• The individual growth curves show that most squid
have rapid growth, but that the degree of that growth
is extremely plastic.
• The growth curves reconstructed for N. sloanii are
different to those reconstructed for most other squid
species. Gender differences not seen.
• This period of slow growth may be an example of the
squid showing “cool” strategies with a slow growing
period which eventually leads to a large size.
CIAC, Hobart, 2006
Discussion
• Gladius growth increments have the
potential to provide information on the
growth of individual squid.
• May be used as an environmental
indicator? Squid growth may be readily
influenced by both biological and
environmental parameters.
CIAC, Hobart, 2006
Acknowledgements
Supervisors/Thesis readers!
Dr George Jackson,
Dr Philip Mladenov
Assoc. Prof. Mike Barker
Squid Collectors
Sea Resources Ltd., Wellington
Master and Crew F. V. Fuji Maru 63
Dr Steve O’Shea , AUT
Master and Crew R.V. Kaharoa
Sandford South Island Ltd
Otakou Fisheries Ltd
Mr Peter Fullerton, Sea Lord Co. Ltd
Master and Crew F.V. Meridien
General
Staff and Students of the
Department of Marine Science and
Portobello Marine Laboratory,
Especially, Kerry Perkins, Bev
Dickson, Karen Bonney and Daryl
Coup
Travel Funding
New Zealand Marine Science Society;
First overseas conference travel
fund
CIAC, Hobart, 2006