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ORIGINAL PAPER
Reproductive status of Octopus pallidus, and its relationship
to age and size
Stephen C. Leporati ÆGretta T. Pecl Æ
Jayson M. Semmens
Received: 22 January 2008 / Accepted: 22 July 2008
ÓSpringer-Verlag 2008
Abstract Age-specific information on individual octopus
reproductive development and investment from wild pop-
ulations has until recently been unobtainable. Using daily-
formed increments within stylets (internal shells) the
individual ages of 503 wild Octopus pallidus were deter-
mined. In addition, detailed reproductive information was
collected for each of the aged octopus, along with repro-
ductive data for an additional 925 octopus. All of the
octopus were collected from Bass Strait waters in south-
eastern Australia from November 2004 to November 2006.
This information was used to investigate seasonal trends in
reproductive scheduling and investment, fecundity and egg
size. Maturation in O. pallidus primarily depends on size
with little relationship to age and is highly variable
between genders, with females [350 days still maturing in
comparison to all males [142 days being mature. Size at
50% maturity for females was approximately 473 g, which
is considerably larger than male 100% maturity at \250 g.
This indicates that for females at least, maturity does not
necessarily come with age. Seasonal scheduling in repro-
ductive investment between genders revealed an optimal
spawning period between late summer and early autumn.
These results reinforce the view that individual growth and
maturity is highly variable in cephalopods.
Introduction
To accurately understand the population dynamics of a
species and ensure the ecologically sustainable develop-
ment of associated fisheries, it is essential to have an
understanding of the reproductive biology, age and growth
of the species being investigated (King 1995). Size-at-
maturity and seasonal patterns in maturation have been
determined for several octopus species (i.e. Octopus
bimaculoides, Forsythe and Hanlon (1988b); Eledone
massyae, Alvarez Perez and Haimovici (1991); Octopus
mimus, Cortez et al. (1995); Octopus vulgaris, Otero et al.
(2007)). Accompanying age information for any octopus
species in the wild has not been obtainable, until very
recently (Leporati et al. 2008). Octopus populations are
known to have variable sizes-at-maturity between and
within genders (Boyle and Knobloch 1982,1983; Voight
1991), high individual growth plasticity (Forsythe and Van
Heukelem 1987), generally short life spans (\2 years)
(Boyle and Rodhouse 2005), and the majority of their bio-
logical processes (i.e. growth, food consumption and egg
development) strongly influenced by temperature and diet
(DeRusha et al. 1987; Klaich et al. 2006). In this context,
age information has been a primary missing factor leading
to reproductive scheduling being completely unexplored.
Reproductive scheduling plays an intrinsic role in octopus
population abundance, where significant declines in
recruitment can occur if environmental conditions and
resources are unfavourable during optimal spawning peri-
ods for these short lived and semelparous organisms (Cortez
et al. 1995; Boyle and Rodhouse 2005). The addition of
reliable reproductive scheduling information may assist the
effective management of octopus fisheries, potentially
reducing the likelihood of population crashes due to over-
exploitation (Ferna
´ndez-Rueda and Garcı
´a-Flo
´rez 2007).
Communicated by J.P. Grassle.
S. C. Leporati (&)G. T. Pecl J. M. Semmens
Tasmanian Aquaculture Fisheries Institute,
Marine Research Laboratories, University of Tasmania,
Private Bay 49, Hobart, TAS 7001, Australia
e-mail: Stephen.Leporati@utas.edu.au
123
Mar Biol
DOI 10.1007/s00227-008-1033-9
Stylets, also referred to as vestigial shells, are paired
structures found in the mantle musculature at the distal end of
funnel retractor muscles in octopus (Bizikov 2004; Dou-
bleday et al. 2006). Stylet increment analysis is a newly
developed method of octopus age estimation that utilises
concentric growth rings found within stylets, fulfilling a
similar role to statoliths in squid and otoliths in teleosts
(Semmens et al. 2004). The periodicity of ring deposition has
been validated as daily in known age captive Octopus pal-
lidus up to 245 days (Doubleday et al. 2006), and this method
has recently been applied to determine the growth of a wild
population of O. pallidus (Leporati et al. 2008). With the
introduction of stylet increment analysis, hatch-dates can be
back calculated and when combined with reproductive
information, seasonal patterns in reproductive investment
can be determined and both growth and recruitment can be
calculated at individual and population levels (Pecl 2004).
This has broad ecological relevance due to the important
predator/prey roles octopuses play in the majority of the
world’s marine ecosystems (Hanlon and Messenger 1996).
Octopus pallidus is a benthic species with no pelagic
stage in its development. It has a depth range of 7–275 m
and is found from the Great Australian Bight around Tas-
mania to southern New South Wales (Stranks 1988,1996).
Mean size at hatching is *0.25 g (Leporati et al. 2007) and
adults have a maximum size of 1.2 kg. As a semelparous
species, females stay with their eggs until they hatch,
shortly after which they die. Octopus pallidus is the target
species of a rapidly expanding Bass Strait fishery (Ziegler
et al. 2007), with fishery logbook data revealing that cat-
ches have increased from 6 t in 1990 to 81 t in 2007.
Despite the increase in catch, very little is known about the
distribution, abundance, diet, size-at-maturity, fecundity,
sex ratios, movement and migration patterns, and stock
status of this species.
This study investigated how reproductive status was
related to age and size, for a wild population of Octopus
pallidus. The specific objectives were: (1) determining size
and age at maturity, (2) analysing patterns of reproductive
investment over different hatch and haul seasons (3)
investigating fecundity and egg size on a seasonal basis, (4)
examining patterns of seasonal reproductive scheduling
between sexes and (5) determining the effects of continual
and concentrated fishing pressure on the age and repro-
ductive structure.
Materials and methods
Specimen collection and dissection
Samples were collected during November 2004 to
November 2006, over 21 independent sampling trips, in an
area of Bass Strait lying between longitude 145°06.73 and
145°44.03 east; and latitude 40°18.401 and 40°53.22 south,
Tasmania, Australia. Bottom set long lines were used to
collect the samples. The lines were *3.7 km long with
*500 pots attached (pot volume =3,000 ml) made from
moulded plastic and set on sandy substrates at 18 locations
at variable depths of 26.0–50.4 m (mean 35.0 m, ±1.21
SE). To determine the effects of continual fishing pressure
on the age and reproductive structure of a localised popu-
lation, a shorter (1 km) single research line was maintained
at the one continuous location using a Global Positioning
System (GPS) receiver (40°43.324 south; 145°20.013 east
and 40°43.788 south 145°20.49 east). For biological sam-
pling a target sub-sample of at least 70 individuals was set
for each trip. Mean seasonal sea surface temperatures from
1985 to 2006 were derived from satellite data downloaded
from the National Oceanic and Atmospheric Administra-
tion (NOAA) USA web page (www.noaa.gov). Austral
seasons were as follows: summer, December–February
(mean 16.7°C), autumn March–May (mean 16.6°C), winter
June–August (mean 12.7°C), and spring September–
November (mean 12.8°C). Sea surface temperatures were
used as a proxy as bottom temperature data were unavail-
able. This was considered a valid approach due to the
generally shallow depths (25–50 m), high wind mixing,
strong tidal currents and season variability in water circu-
lation observed in this region of Bass Strait (Sandery and
Ka
¨mpf 2007).
After landing, morphological measurements and dis-
sections were performed on fresh specimens. Whole weight
(WW) and eviscerated body weight were measured and the
visceral mass of each specimen fixed in formaldehyde
(10%), acetic acid (5%), calcium chloride (1.3%) and
freshwater (83.7%) solution. After a period of 14–28 days
the visceral mass was transferred to 70% ethanol for
preservation. The reproductive organs of a sub-sample of
50 females in various reproductive stages were freshly
weighed prior to preservation, and again after 14 days, in
order to determine the effects of preservation on the weight
of the reproductive organs.
The reproductive organs were removed from the pre-
served visceral mass and weighed to 0.001 g for each
octopus. The parameters measured for males were: the
whole reproductive complex (MRW), which was then
dissected so the testis, and Needham’s sack could be
weighed independently. The presence or absence of sper-
matophores in the Needham’s sack and penis was noted.
Parameters weighed for females were: the whole repro-
ductive complex (FRW), which was then dissected so the
ovary, left and right distal oviducts, left and right oviducal
glands, and left and right proximal oviducts could be
weighed independently. Somatic weight was determined by
subtracting the weight of the MRW or FRW from the WW.
Mar Biol
123
Maturity stages
Maturity stages were determined by visual identification of
characteristics in the preserved reproductive organs and
derived from scales used by Alvarez Perez and Haimovici
(1991) and Smith et al. (2006). Each scale was expanded
and modified for O. pallidus accordingly. For males four
reproductive stages were determined: (I) immature, the
accessory gland systems and testis are indistinct; (II)
maturing, testis larger than the accessory gland and visible
through the wall of the genital bag; (III) mature, testis and
accessory gland of similar size and spermatophores present
in the penis and/or Needham’s Sack; and (IV) spent, testis
small and striated and spermatophores present in the penis
and/or Needham’s Sack. For females five reproductive
stages were determined: (I) immature, small ovary generally
weighing \3 g with no follicles present and a thick outer
wall, small white oviducal glands located mid-way down
very narrow proximal and distal oviducts; (II) maturing,
ovary slightly larger and with a thinner wall than stage I
with follicles and or very small eggs present, oviducts
longer and white oviducal glands larger and positioned
further up the proximal oviduct; (III) mature, ovary very
large ([20 g) packed tightly with elongated striated eggs
without stalks, the oviducal glands are large and dark in
colour and positioned high up the proximal oviduct; (IV)
spawning, majority of eggs have stalks, are fully formed and
less compressed than in stage III, eggs present in the ovi-
ducts and dark oviducal glands located further down the
proximal oviduct; (V) post-spawning, shrunken ovary with
only follicles and a few fully formed eggs still present,
oviducts slightly reduced in size unless containing eggs, the
oviducal glands smaller but still dark in colour.
Fecundity and egg size
The number of eggs in the ovaries and oviducts of stage III
(n= 173) and IV (n=104) females were counted as
estimates of potential fecundity. To calibrate the technique
20 stage III individuals had all their eggs counted, the
remaining 153 individuals had a sub-sample of 20% of the
weight of the ovary counted. Due to the smaller number of
eggs in stage IV females, these 104 individuals had all their
eggs counted. To provide an indication of mature egg size,
the total lengths of 20 eggs were measured from 20 stage
IV individuals. Due to uniformity of egg lengths the
remaining 84 individuals had only 10 eggs measured; all
lengths were measured to the nearest 0.001 mm. The
number of eggs from brooding females in 12 pots were
counted, along with the number of eggs in the ovary and
oviducts, and compared to stage III potential fecundity
estimates to provide an indication of how many eggs are
laid by a female and how many are resorbed in the ovary. A
sub-sample of ten eggs from five of the pots were measured
and compared with eggs found in the ovaries of the cor-
responding females.
Ageing
Age was determined using stylet increment analysis
(Doubleday et al. 2006; Leporati et al. 2008). Stylets were
extracted from the mantle musculature and preserved in
70% ethanol. A transverse section was cut from the region
immediately after the elbow on the posterior side of the
stylet (Doubleday et al. 2006). The section was positioned
on a glass microscope slide and embedded in thermo-
plastic cement (Crystal Bond
TM
509). The slide was then
placed on a hotplate (approximately 130°C) until the
crystal bond was viscous enough to be moulded. The sec-
tion was then ground on damp 1,200-lm sand paper and
progressively polished on 12, 9 and 5-lm damp lapping
film to a thickness of approximately 0.5 mm. A final polish
on a pellon PSU PA-K polishing disk impregnated with an
alumina powder (0.05-lm) and water slurry was performed
to remove surface scratches. The section was then viewed
under a compound microscope (Nikon Eclipse E400),
connected to a video camera (Leica DC300F) and com-
puter using Leica IM50 (version 1.20) software. At 4009
magnification, approximately 5–10 images were taken per
section depending on the width of the section. Images were
taken sequentially from the nucleus to the outer edge fol-
lowing the clearest line of concentric rings. The images
were then stitched together Using Adobe Photoshop (ele-
ments) to create a composite plane of the section (Fig. 1).
The concentric rings were then counted using a hand
counter from the nucleus to the outer edge. Ages were only
determined for a sub-sample of individuals, all of which
were taken from the permanent research line. This was
conducted so the effects of continual fishing pressure on
age structure could be determined.
Data analysis
Paired T-tests were performed to determine if there were
any significant differences between the preserved and fresh
organs, and the WW of males and females. Chi-square (v
2
)
was performed to assess differences in the sex ratios among
seasons. Pearson’s correlations were performed to deter-
mine the strength of the relationship between fecundity and
WW, somatic weight, ovary weight and age. Size-at-
maturity (WW) was determined by calculating the point
where 50% of the females were mature. This was estimated
by creating a relative frequency distribution for 20-g
weight classes and fitting the results by the least squares
method to a logistic curve with the formula (Tafur et al.
2001):
Mar Biol
123
Pi¼1
1þeðaþbWiÞ
where Pirepresents the relative frequency of the mature
individuals in weight class Wi,aand bare the regression
constants, and 50% maturity weight (MW50%) =a/b.
The mean standardized residuals for the relationship
between WW and MRW, and WW and FRW were calcu-
lated as an indication of an individual’s investment in the
development of reproductive organs at time of capture
(Pecl and Moltschaniwskyj 2006). The residuals, defined as
the difference between the actual measured weight and the
predicted weight, were calculated using mean non-linear
regression (Model II) equations based on log-transformed
data. To standardize the residuals they were divided by the
standard deviation of the predicted values. The resultant
values were either negative or positive values, with the
negative representing individuals that had less reproductive
investment than expected for their size. ANOVAs were
performed to determine if there were differences in
reproductive investment among female reproductive
stages, and hatch and haul seasons, with post hoc least-
significant difference (LSD) tests used to determine the
nature of any differences. Only mature stage III males and
IV females were used in the haul season analysis to ensure
the reproductive investment results were comparable and
not influenced by immature and post-spawning individuals.
For the hatch season analysis only stage III and IV females
aged between 155 and 275 days were used to insure that
accurate comparisons could be made between individuals
of similar ages and stages of development. A restricted age
range was used in these analyses as growth and repro-
ductive development are linked in captive octopus, where
younger individuals generally grow faster on average than
older individuals (Forsythe 1993). Using a restricted age
range ensured that results demonstrated seasonal influences
on reproductive development as opposed to the effects of
differing growth rates. The specific range of 155–275 days
was chosen because it constituted 35% of the total age
range and 70% of the sample. Hatch season analysis was
not performed for males due to insufficient numbers. All
data were tested for normality prior to analyses and log
transformed (log 10), where necessary.
Results
A total of 466 males and 962 females were collected
for reproductive analysis. The weights of the preserved
and fresh reproductive organs were significantly different
(t=-8.865, df 28, P=0.000), with the preserved organs
on average 13% heavier than the fresh. This effect was
uniform across all samples, and weights were subsequently
corrected accordingly, prior to any analysis. The WW for
males ranged from 245 to 1,004 g (mean =568 g ±5.001
SE) and for females 243–981 g (mean =519.7, ±3.554
SE), with no significant difference in WW between the
sexes (t=0.659, df 465, P=0.51). Sex ratios were sig-
nificantly different among seasons (v
2
=420.592, df 11,
P=0.000) (Fig. 2). Females dominated at a mean of 69%
(±6.114 SE) of the catch across all seasons. However,
during the 2004–2005 and 2005–2006 summers, female
sex ratios were at their lowest levels for each of the cor-
responding years.
All males caught were stage III (n= 399) and IV
(n= 66) individuals, except for a single stage II male.
Spermatophores were found in the penis or Needham’s
sack of all of the males, except for the solitary stage II
Fig. 1 Composite image of a
stylet at 9400 magnification
(reduced to 46%), taken from a
female Octopus pallidus, total
weight 377 g, estimated age
202 days
Mar Biol
123
male. All female reproductive stages were represented in
the catches: stages I (n= 105), II (n= 137), III (n= 412),
IV (n= 169), V (n= 139). MW50% for females was 473 g
(Fig. 3).
Ages were determined for 94 males and 409 females,
with back-calculated hatch dates revealing that spawning
occurred throughout the year. The males ranged in age
from 142 to 589 days (mean =259 days, ±7.623 SE),
whereas the females ranged in age from 110 to 475 days
(mean =243 days, ±3.182 SE). Reproductive develop-
ment showed no relationship with age for females with
the proportions of immature, mature and post-spawning
females consistently represented in most age classes
(Fig. 4). The youngest post-spawning (stage V) female was
121 day old in contrast to the oldest immature female
(stage I), which was 459 day old.
The mean standardized residuals for the MRW–WW
relationship for stage III males were significantly different
among seasons (F=12.777, df 8, P=0.000) with peaks
in reproductive investment occurring during the summer
(Fig. 5a). The mean standardized residuals from the FRW–
WW relationship for mature females (stages III and IV)
also displayed significant differences among seasons
(F=15.637, df 8, P=0.000) with generally lower
reproductive investment during the autumn than spring in
each year (Fig. 5b). Significant differences in reproductive
investment of mature females (stage III and IV) were also
evident among hatch seasons (F=2.787, df 7, P=0.011),
with females from the early winter and spring 2004 hatch
seasons displaying the lowest levels of reproductive
investment followed by progressively higher investment in
the subsequent hatch seasons (Fig. 6).
Potential fecundity estimates for stage III females ran-
ged from 270 to 910 eggs (mean =634, ±8.235 SE), 58%
of which were within the range of 550–700 (Fig. 7).
Fecundity was significantly correlated with WW (Pearson
correlation =0.647, n=172, P=0.000, r
2
=0.419),
and with somatic weight (Pearson correlation =0.568,
n=172, P=0.000, r
2
=0.329), and ovary weight
(Pearson correlation =0.544, n=172, P=0.000,
r
2
=0.328), but not age (Pearson correlation =-0.032,
n=55, P=0.815, r
2
=0.004). However, there were
significant differences among haul seasons (F=4.257, df
8, P=0.000), with peak fecundity occurring during the
summer of 2004–2005 followed by a progressive decline
until the spring of 2005 (Fig. 8). The number of individuals
with both hatch date and fecundity data was limited to
n=55 distributed over eight seasons (mean =6.1 ±
1.585 SE) with no significant differences detected among
females from all hatch seasons (F= , 0.624, df 8,
P=0.753). Octopus with stage IV ovaries had a fecundity
range of 18–590 eggs (mean =197.38 eggs, ±14.740 SE)
with egg sizes ranging from 9.07 to 13.45 mm
(mean =11.57 mm, ±0.067 SE). Egg size showed no
relationship with age (n=36, r
2
=0.0061), WW
(n=101, r
2
=0.0205), somatic weight (n=101,
r
2
=0.0169) or ovary weight (n=101, r
2
=0.0392). The
number of eggs female
-1
counted in the 12 pots that
contained brooding females ranged from 466 to 778
(mean =424, ±43.774 SE). Lengths of the eggs in the pots
0
1
2
3
4
5
6
spring 04
summer 04/05
autumn 05
winter 05
spring 05
summer 05/06
autumn 06
winter 06
spring 06
Haul season
Proportion of females to males
n = 69
n = 200
n = 213
n = 201 n = 210
n = 209
n = 140
n = 70
n = 116
Fig. 2 Proportion of female to
male Octopus pallidus caught
per haul season with nvalues.
The octopus were sourced from
all lines
Mar Biol
123
(mean =12.02 mm ±0.102 SE) were equivalent to those
in the ovary and oviducts of each female examined
(mean =11.83 mm ±0.101 SE).
Discussion and conclusions
Maturation in Octopus pallidus is primarily size-depen-
dent, with little relationship to age. Even at the latter stages
of the life span (i.e. 300 days) an older but smaller female
can still be maturing, when much younger larger females
have already matured. This supports the increasing view
that cephalopods are highly dynamic organisms that grow
and mature with great degrees of individual variability,
often influenced by external factors such as temperature
and diet (Moltschaniwskyj 2004), and biological factors
such as genetic differences (Triantafillos 2004). By
including age information, this study has provided insights
into the seasonal reproductive scheduling of O. pallidus,
revealing that even though spawning occurs year round,
there are distinct seasonal trends in reproductive invest-
ment for males and females. Peak female reproductive
investment occurred during spring (ovary maturation) in
conjunction with increases in male reproductive investment
(spermatophore production) during summer, leading to a
potential optimal spawning period during late summer,
60
whole weight (g)
% mature
100
75
50
25
0
MW50%= 473 g
120 180 240 300 360 420 480 540 600 660 720 780 840 900
Fig. 3 Size (whole weight) at
50% maturity (MW50%) for
O. pallidus females from all
lines in 20-g weight classes,
n= 657
n = 5 n =32 n =34 n =54 n =45 n =56 n =49 n =40 n =24 n =18 n =12 n =11 n =6 n =2 n =2 n =2 n =2 n =1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Age (days)
Proportion
110
immature mature spent
130 150 170 190 210 230 250 270 290 310 330 350 370 390 410 430 450 470
n =12
Fig. 4 Proportion of immature (stages I, II), mature (III, IV) and spent (V) Octopus pallidus females from the research line in each 20-days age
class
Mar Biol
123
indicated by reductions in both male (spent) and female
(egg laying) reproductive investment during the autumn.
Female size at 50% maturity was *473 g indicating
that females larger than this are most likely to be mature
and increasingly so as their weight increases. However, this
pattern was not mirrored for WW \473 g. Given that O.
pallidus is a semelparous species, like the vast majority of
benthic octopus species (Norman 2000), females that were
either in reproductive stages IV or V generally weighed
less than stage III females, because sub-473 g females
included immature, spawning and post-spawning individ-
uals. As observed in other octopus species, i.e. Octopus
mimus (Cortez et al. 1995)and Octopus bimaculatus
(Ambrose 1988), this was not just a product of weight
reduction from the laying of eggs, but also the decrease in
somatic weight for stages IV and V octopus as the females
lost muscle mass after laying their eggs.
All males sampled in this study were [250 g, mature
and older than 142 days, indicating that males mature at a
size \250 g. Octopuses \250 g are generally not caught
in the O. pallidus commercial fishery, suggesting that
immature males are generally not vulnerable to fishing
pressure. In contrast, all five female reproductive stages
were represented in the sampling, even though all females
sampled were in the same age and size range as the males,
caught with the same fishing gear, and during the same
times and locations. Male and female O. pallidus are
known to reach similar maximum sizes and ages, and have
spring 04
summer 04/05
autumn 05
winter 05
spring 05
summer 05/06
autumn 06
winter 06
spring 06
Haul season
-0.12
-0.10
-0.08
-0.06
-0.04
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
Mean standardized residual +/-SE
A
n = 39
n = 52
n = 25
n = 39
n = 71
n = 101
n = 104
n = 115
n = 36
C
C
B
AB
A
A
A
A
(b)
-0.05
-0.04
-0.03
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
0.05
Mean standardized residal +/- SE
A
n= 9 n= 18
n= 15
n= 26
n= 58
n= 45
n= 45
n= 118
n= 65
A
A
A
AB
AC
A
C
AB
(a)
Fig. 5 Mean standardized
residuals for the relationship
between whole weight (WW)
and the whole reproductive
complex weight for stage III and
IV Octopus pallidus from all
lines, with significant
differences in mean
standardized residuals between
haulseasons denoted by letters
(A, B, C) derived from LSD
post hoc tests. aMales and
bfemales. Values above the
line indicate higher levels of
reproductive investment for
their size, whereas values below
the line indicate lower levels of
reproductive investment
Mar Biol
123
similar growth rates calculated over the life span of the
individual (Leporati et al. 2007), indicating that males
mature at a considerably smaller size and generally
younger age (\250 g, \110 days) than females ([460 g,
?–350 days).
Gender-specific size-at-maturation patterns have been
observed in Octopus vulgaris (Alvarez Perez and Haimo-
vici 1991; Herna
´ndez-Garcı
´a et al. 2002; Rodriguez-Rua
et al. 2005; Otero et al. 2007), Eledone massyae (Alvarez
Perez and Haimovici 1991) and Octopus bimaculoides
winter 04
spring 04
summer 04/05
autumn 05
winter 05
spring 05
summer 05/06
autumn 06
Hatch season
-0.16
-0.14
-0.12
-0.10
-0.08
-0.06
-0.04
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
Mean standardized residual +/- SE
A
AB
B
BC
BC
n= 8
n= 11
n= 24
n= 11
n= 17
n= 24
n= 23
n= 9
C
AB
A
Fig. 6 Mean standardized
residuals for the relationship
between whole weight (WW)
and the whole female
reproductive complex weight
(FRW) for stage III and IV
Octopus pallidus from each
hatch-season, with significant
differences in mean
standardized residuals denoted
by letters (A, B) derived from a
LSD post hoc test. Dashed line
represents expected levels of
reproductive investment. Values
above the line indicate higher
levels of reproductive
investment for their size,
whereas values Fig. 2below the
line indicate lower levels of
reproductive investment. All
octopus were sourced from the
research line
0
5
10
15
20
25
250-300
Number of eggs
% Frequency
300-350 350-400 400-450 450-500 500-550 550-600 600-650 650-700 700-750 750-800 800-850 850-900 900-950
Fig. 7 Percent frequency for number of ovarian eggs for stage III female Octopus pallidus from all lines, n= 180
Mar Biol
123
(Forsythe and Hanlon 1988a). The later reproductive
development and larger size-at-maturity of females com-
pared to males is necessary to build a strong somatic base
to withstand the required energy shift associated with
committing a larger proportion of body mass to reproduc-
tive development (Otero et al. 2007). This was observed in
the present study where 12% of the WW of females was in
the reproductive organs in comparison to only 2% of WW
in males. In addition, earlier maturation of males allows for
opportunistic mating between mature males and immature
females, for female octopus, i.e Octopus tetricus (Joll
1976) and O. vulgaris (Rodriguez-Rua et al. 2005), have
the ability to store sperm over lengthy periods and to use
them at the onset of maturity. Size-at-maturity and age
information is integral for the future management of
commercial octopus fisheries and can be used in potential
management initiatives such as gender-specific size
restrictions on catch, or combined with gender composi-
tion, catch, size and growth data, to help determine the
potential impacts of commercial fishing on a population.
Reproductive investment increased progressively with
each subsequent hatch season in octopus caught on the
research line. A potentially related trend was observed in
the size and growth information derived from the same data
set (see Leporati et al. (2008)), where octopus from pro-
gressive subsequent hatch seasons displayed reductions in
size and increased growth rate. These trends may be
attributed to the intentional fishing down of the population
around the research line, where larger females were being
removed and replaced by smaller, younger, faster growing
females that invested proportionally more energy in
reproduction. A possible explanation for this is that larger
individuals commonly win competitions for brood sites
(shelters such as pots) (Aronson 1986), thus leading to
larger females being the first to be removed when an area is
fished down. Following this trend, the next group to occupy
the pots would be the faster growing individuals that reach
a large size quickly and hence reach size-at-maturity ear-
lier, equating to higher levels of reproductive investment.
This is an important consideration for the management of
octopus fisheries and indicates that repeated pressure on the
one area may lead to size-selective fishing mortality. The
extent to which repeated fishing pressure could affect a
local octopus population will vary with reproductive
strategy. A holobenthic species, like O. pallidus that has
100s of eggs and benthic dispersal of hatchlings, could be
more prone to localised impacts than merobenthic species,
which have 100,000s of eggs and more broadly distributed
planktonic dispersal of hatchlings (Narvarte et al. 2006).
These effects could also be seasonally and spatially vari-
able depending on bottom temperature, with optimal
spawning periods identified for some octopus species, i.e.
O. vulgaris (Otero et al. 2007), and maturation and egg
development generally slower at lower temperatures within
a species natural range (Caveriviere et al. 1999). Prolonged
brooding at lower temperatures could also result in greater
competition for remaining brood sites, and the likelihood of
brooding females being caught in the fishery. These
impacts on the composition of the O. pallidus population
have direct ecological consequences (Coleman and Mobley
1984; Arrenguı
´n-Sa
´nchez 2000). However, to determine
the full extent of these effects, further investigations into
spring 04
summer 04/05
autumn 05
winter 05
spring 05
summer 05/06
autumn 06
winter 06
spring 06
Haul season
500
520
540
560
580
600
620
640
660
680
700
720
740
760
780
Fecundity
A
n= 18
n= 22
n= 21 n= 17
n= 19
n= 22
n= 18
n= 18
n= 18
A
A
A
A
A
A
AB
B
Fig. 8 Mean potential
fecundity per haul-season for
female Octopus pallidus from
all lines, with significant
differences in mean fecundity
denoted by letters (A, B)
derived from an LSD post hoc
test
Mar Biol
123
O. pallidus’ role in the trophic structure of the Bass Strait
ecosystem are required. Such studies should include prey
profiles, habitat usage at different life stages, and seasonal
patterns in predator and prey abundances.
Male catch rates and reproductive investment peaked
during the summer. With octopus growth rates generally
greater at higher temperatures (Semmens et al. 2004), this
suggests that a pulse in fast growing mature males may
have occurred during the summer months. Female
reproductive investment was generally highest during the
spring and lowest during the autumn, with no evident
relationship to seasonal catch-rates. However, when
placed in context with male reproductive schedules, a
potential optimal-breeding season was apparent, i.e.: peak
female reproductive investment (late stage III egg vitel-
logenesis) occurred during spring, which was followed by
the summer pulse in the number of mature males, which
was then followed by the autumn decrease in female
reproductive investment (late stage IV spawning). This
suggests that the peak-spawning season for O. pallidus is
around late summer and early autumn. This is supported
by laboratory findings on O. pallidus hatchling growth,
where octopus hatched at higher temperatures (summer)
grew faster and ultimately larger than those hatched at
lower temperatures (spring), even if hatchlings experi-
enced equivalent degree days (Leporati et al. 2007). A
similar example of seasonal reproductive scheduling was
found in wild Octopus bimaculatus (Ambrose 1988),
where eggs laid during the coldest months were generally
non-viable and took 60–100 days to hatch, whereas eggs
laid during the warmer months had high viability and
took only 30–40 days to hatch. The delay in hatching due
to cold temperatures resulted in most of the octopus
hatching during summer/autumn, regardless of when they
were laid. Even relatively small temperature changes can
have a significant influence on cephalopods’ physiological
responses, which in turn can affect the structure of a
population (Grist and des Clers 1999). However, it must
be considered that O. pallidus is a year round spawner
and has a maximum life span of *18 months (Leporati
et al. 2008), hence this should be regarded as an optimum
spawning period, as opposed to a discrete spawning
season.
The maximum potential fecundity of O. pallidus was
910 eggs, however, a more typical fecundity range of 550–
700 eggs was identified. The number of eggs actually laid
for many octopus species is dictated by available substrate,
quality (structure, material and shape) of the shelter used
(Iribarne 1990) and resorption rates in the ovary (Melo and
Sauer 1998). When considering the mean egg count of 422
eggs female
-1
from the 12 pots containing mothers with
egg batches, it seems that O. pallidus lay a large proportion
of the available eggs.
Fecundity was positively correlated with somatic
weight, and was also influenced by seasonal temperature
changes, with fecundity *10% higher during summer/
autumn than during winter/spring. This coincides with the
optimal spawning period identified in this study and the
general observation of increased growth at warmer tem-
peratures (within the natural range of a species) for many
octopus species (Forsythe 1993; Cortez et al. 1995; Lepo-
rati et al. 2007), which results in size-at-maturity being
reached at an earlier age. These trends indicate that O.
pallidus hatched during summer/autumn may grow faster,
mature earlier and have potentially higher fecundity than
those hatched during winter/spring.
Continual local fishing pressure appeared to have altered
the age and reproductive structure of the female O. pallidus
population, reflecting size selective fishing mortality,
which could lead to smaller sizes at maturity, fecundity,
and ultimately recruitment. The magnitude of such effects
on a localised holobenthic octopus population is unknown
and requires further investigation. However, by avoiding
heavy localised fishing pressure, particularly during the
optimal spawning periods, and monitoring sex ratios and
the size of mature females, the potential for localised
population depletion could be minimized.
This is the first study to investigate the relationship
between reproductive development and age in a wild
population of octopus, demonstrating that reproductive
development in females is primarily a size-dependent
process and that maturation is reached at a broad range of
ages. Maturation is more closely linked to size and the
parameters that govern growth, such as temperature and
probably also diet. Even though age was not related to
maturation, age information still plays an essential and
interconnected role by enabling the reliable and accurate
determination of growth (Semmens et al. 2004). Hence,
this study has supplied the missing factor (age) in our
understanding of the population dynamics of O. pallidus,
and will contribute to the ecological sustainability of the
O. pallidus fishery.
Acknowledgments We thank the Hardy family, the captains and
crews of the William L and the Seafarer, Z.A. Doubleday, T. Hib-
bered, FI. Trinnie and D. Young and all the workers at T.OP Fish Pty
Ltd who assisted in sample collection. This study was supported with
funding from The Department of Primary Industries and Water. This
experiment complied with current Tasmanian and Australian laws and
was approved by the Animal Ethics Committee of the University of
Tasmania under project No. A0008130.
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