Diet and Feeding Habits of Octopus hubbsorum Berry, 1953, in the Central Mexican Pacific

Abstract

Abstract. The diet and feeding habits of Octopus hubbsorum were analyzed using 226 individuals obtained from commercial artisan catches in the Central Mexican Pacific from July, 1999, to August, 2000. Organisms ranged from 43 mm to 230 mm in dorsal mantle length. The diet comprised 53 types in seven phyla; crustaceans, mollusks, and fishes were the main groups. In general, the crustaceans were dominant; in particular, species of brachyurans, carideans, and anomurans, with values of more than 40%, according to the index of occurrence and the indexes of importance in weight and number. The diet is affected by sex, size, sexual maturity, and the season of the year. The females fed preferably on mollusks (gastropods and bivalves) and had a higher proportion of food in their stomachs than males, while the males fed mostly on crustaceans and members of the group ‘‘others.’’ The type of prey and its proportion also vary as the organism grows; new species of prey were found more frequent in larger octopuses. The juveniles contained a lower number of prey species than the mature individuals. The males showed a clear tendency to increase the number of prey groups from warm to temperate environmental conditions. These results confirm that O. hubbsorum is an opportunistic predator.

Full text

Diet and Feeding Habits of Octopus hubbsorum Berry, 1953,
in the Central Mexican Pacific
ERNESTO LO
´PEZ-URIARTE, EDUARDO RI
´OS-JARA
Laboratorio de Ecosistemas Marinos y Acuicultura, CUCBA, Universidad de Guadalajara, Las Agujas, Nextipac,
Zapopan, Jalisco. C.P. 45110. Tel: (52)33-37771156
(e-mail: ernlopez@cucba.udg.mx)
AND
MO
´NICA ELIZABETH GONZA
´LEZ-RODRI
´GUEZ
Instituto de Acuicultura y Pesca, Secretaria de Desarrollo Rural, Gobierno del Estado de Jalisco
Abstract. The diet and feeding habits of Octopus hubbsorum were analyzed using 226 individuals obtained from
commercial artisan catches in the Central Mexican Pacific from July, 1999, to August, 2000. Organisms ranged from
43 mm to 230 mm in dorsal mantle length. The diet comprised 53 types in seven phyla; crustaceans, mollusks, and
fishes were the main groups. In general, the crustaceans were dominant; in particular, species of brachyurans,
carideans, and anomurans, with values of more than 40%, according to the index of occurrence and the indexes of
importance in weight and number. The diet is affected by sex, size, sexual maturity, and the season of the year. The
females fed preferably on mollusks (gastropods and bivalves) and had a higher proportion of food in their stomachs
than males, while the males fed mostly on crustaceans and members of the group ‘‘others.’’ The type of prey and its
proportion also vary as the organism grows; new species of prey were found more frequent in larger octopuses. The
juveniles contained a lower number of prey species than the mature individuals. The males showed a clear tendency
to increase the number of prey groups from warm to temperate environmental conditions. These results confirm that
O. hubbsorum is an opportunistic predator.
INTRODUCTION
Octopus hubbsorum has a wide geographical distribu-
tion, ranging from the central Gulf of California
(28u559N, 113u329W) to the southern coast of Oaxaca,
Mexico (16u109N, 95u149W) (Lo´pez-Uriarte et al.,
2005). It constitutes practically half of the catch of
the octopus fishery in the Mexican Pacific, totaling
nearly 1000 tons per year (SAGARPA, 2002). During
the last decade, this resource has occupied one of the
first five places of the coastal fisheries of Jalisco (Rı
´os-
Jara et al., 2004).
Octopuses are ferocious carnivores, feeding during
the day or night on a wide variety of prey species,
which are detected either by vision or by touch (Hanlon
& Messenger, 1996). At all stages of development,
octopuses are active predators, feeding mainly on
crustaceans, mollusks, and fishes; but ophiuroids,
polychaetes, chaetognaths, and siphonophores consti-
tute part of the diet of some species. The proportion of
these types of food depends on the species, the sex, and
the sexual maturity of the individuals (Nixon, 1987).
Because of their opportunistic behavior, prey density
also has an important effect on feeding; the octopods
consume the most common prey available in their
habitats (Wolterding, 1971; Hochberg & Couch, 1971;
Hanlon, 1975; Van Heukelem, 1976; Ambrose &
Nelson, 1983; Ambrose, 1984). However, mature
females reduce their intake of food by up to 50%two
weeks before spawning and for at least three weeks
afterward; feeding is also reduced during the winter
when temperatures are under 15uC (Borer, 1971).
There have been no studies on the feeding behavior
and diet of O. hubbsorum. The only previous report was
made from observations of the shells of gastropods and
bivalves found outside the caves and shelters of adult
octopuses living in the shallow rocky areas of Bahia de
Coastecomate, Mexico (19u139470N and 104u439440W)
(Raymundo, 1995).
The present study aims to describe, first, the diet of
O. hubbsorum in the central Mexican Pacific through
the analysis of stomach contents, and, second, the
feeding dynamics using different indices to evaluate the
possible effect of sex, size, stage of maturity, and the
seasons of the year. This contribution to the studies of
the Mexican species of octopuses is the first detailed
description of the feeding habits of this species.
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The Veliger 51(1):26–42 (January/April XX, 2008)
THE VELIGER
#CMS, Inc., 2008

MATERIALS
AND
METHODS
Area of study: The littoral of Jalisco is located in the
central Mexican Pacific (between 20u409Nand18u589N).
This study was conducted in the central region of Jalisco,
where Octopus hubbsorum is exploited commercially.
This region extends approximately 38 km from Punta
Soledad (19u369470N, 105u129130W) to Punta Farallo´n
(19u239220N, 105u029170W) (Figure 1). The coastline of
this region is characterized by sandy beaches alternating
with rocky shores and cliffs. In the shallow areas, there
is a complex substratum of bedrock, boulders, rock
rubble, and sandy bottoms, with small rocks inter-
spersed with patches of sand covered with a layer of fine
sediment consisting largely of detritus particles. The
more heterogeneous rocky bottoms have higher abun-
dance and a greater variety of macroalgae, inverte-
brates, and fishes. In some of these areas, several species
of stony corals (Pocillopora spp. and Porites spp.) grow
together, forming aggregations with a characteristic
flora (macroalgae) and fauna (crustaceans, echino-
derms, molluscs, polychaetes, gorgonians, and fishes).
<
The region has warm–wet climate, with the rainy
season occurring mostly during the summer. Temper-
atures range from 32.3uC in September to 20.6uCin
January (mean 525.2uC) (Secretarı
´a de Programacio´n
y Presupuesto, 1981). The surface-water temperature of
Bahia Chamela is higher from June to September
(26.0–30.6uC) and lower from February to May (22.8–
26.6uC); the difference between the maximum value
(July 530.6uC) and the minimum value (February 5
22.8uC) is approximately 8uC (Silva-Segundo et al.,
2006). Cumulative monthly precipitation ranges be-
tween 800 mm and 1500 mm, with the highest values
from June to September and the lowest from February
to April (Villalpando & Garcı
´a, 1993). There is a mixed
semidiurnal tidal cycle with two unequal high tides and
two unequal low tides each day. The region is strongly
influenced by tropical storms and cyclones during the
warm, wet season. Coastal waters are relatively
The Veliger veli-51-01-04.3d 24/11/09 22:32:31 27
Figure 1.
E. Lo´pez-Uriarte et al., 2009 Page 27

productive and have the influence of three main surface
currents: (1) the North Equatorial Countercurrent,
with warm waters from the south (June–September);
and (2) the Gulf of California Current (October–
January) and (3) the California Current (February–
May), both of which bring cooler waters from the
north (Wirtky, 1965, 1966). Therefore, there is well
defined seasonality with three main seasons during the
year: (1) a warm–wet season from June to September,
which corresponds to the rainy period of the year, with
warm surface-water temperatures higher than 26uC; (2)
a warm–dry season from October to January, when the
surface-water temperature is still warm and the rainfall
is scarce or absent; and (3) a cool–dry season from
February to May, when the surface temperature falls to
approximately 22uC and there is low rainfall.
Methods: A total of 562 individuals of Octopus
hubbsorum were obtained from the commercial artisan
catches made by local fishermen at three different
localities of the central region of Jalisco. Time of
capture was between 8:00 a.m. and 3:00 p.m. at depths
shallower than 30 m. Collection of individuals began in
July of 1999 and ended in August of 2000.
The dorsal mantle length (DML), total body weight,
and sex of each individual were first determined in the
field, and then all individuals stored at 220uC. After
thawing, the maturity stage was assigned in the
laboratory using the scale of Guerra (1975) as revised
by Cortez, Castro & Guerra (1995).
To analyze the diet and feeding habits, a total of 226
specimens were used. The visceral mass of each
specimen was separated (by dissecting the mantle)
and weighed (60.1 g). Also, the digestive tract was
separated from the rest of the visceral mass and
weighed (60.01 g). The contents of the digestive tract
was then separated and the prey items were counted
and identified to the lowest possible taxon. The
different types of prey were grouped according to
taxonomic affinities, resulting in five putative groups:
mollusks (including only gastropods and bivalves),
cephalopods, crustaceans, teleosts and other items.
Several indexes were used to describe the diet and to
compare the items according to sex, size, stage of
maturity, and the seasons of the year (Hyslop, 1980;
Castro & Guerra, 1990; Sa´nchez and Obarti, 1993;
Cortez et al., 1995):
1. Fullness Index FI~Wsc=WtðÞ100
Wsc 5weight of the stomach contents. Wt 5
total weight of the specimen (Hyslop, 1980).
The results of FI were grouped in levels
according to the different degrees of filling of
the stomachs, as suggested by Herna´ ndez-
Lo´ pez (2000): FI 50 (level I, empty
stomach); 0 ,FI #0.3 (level II, almost
empty stomach), 0.3 ,FI ,1 (level III, half
full stomach), FI $1 (level IV, full stomach).
2. Vacuity Index VI~Es=TsðÞ
1100
Es 5number of empty stomachs, Ts 5total
number of stomachs analyzed (226).
3. Occurrence Index OI~Ne
i
nPi~1
Ne

1100
Ne
i
5number of stomachs with the prey item
i;nP
i~1
Ne
5total number of different prey
species
;
.
4. Importance in Weight Index IWI~Wi=WtðÞ
1100
Wi 5weight of each type of prey i,Wt 5
total weight of all prey items.
5. Importance in Number Index INI~Ni=NtðÞ
1100
Ni 5number of individuals of each type of
prey i,Nt 5total number of individuals of all
prey items.
To analyze the influence of size on the diet and the
feeding habits of O. hubbsorum, two groups were
considered: (1) juveniles (60–100 mm DML) and (2)
adults (.100 mm DML). Among the adults, three
maturity groups were compared: immature, mature,
and senescent (females) or discharged (males). Matur-
ing specimens were included in the mature group. The
seasons of the year considered for these analyses were
(1) warm–wet season (June to September), (2) warm–
dry season (October to January) and (3) cool–dry
season (February to May).
Comparisons of the indexes (FI,VI,OI,IWI,and
INI) between groups were made by means of a chi-
square test (Sokal & Rolf, 1969). The level of statistical
significance used was a50.05.
RESULTS
Size and sex proportion of the octopus population:
Figure 2 shows the size (dorsal mantle length, DML)
and stage of maturity (immature, mature, and senes-
cent) of 514 individuals of Octopus hubbsorum sampled
from the commercial artisan catches in the central
region of Jalisco. The DML ranged from 43 to 230 mm
(mean 5110.43 mm 6SD 42.78 mm). The sex
proportion was 1.35:1 (296 females, 218 males). The
larger sizes (DML) were recorded for the females (t5
3.29; P,0.01), range 43 to 230 mm (mean 5111.36 6
SD 26.33 mm) and the smaller sizes for the males,
range 43 to 162 mm (mean 5104.49 6SD 21.49 mm).
Composition and conservation of the prey items: A total
of 53 different prey items were identified in the stomach
content of the octopuses. These items included almost
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Figure 2. =
E. Lo´pez-Uriarte et al., 2009 Page 29

The Veliger veli-51-01-04.3d 24/11/09 22:32:39 30
Table 1
Composition of diet of Octopus hubbsorum.
Ocurrence (N) Weight (g) Number (N)
total %total %total %
Crustacea 294 57 225 46 2157 88
Estomatopoda 16 3%22 1%
Gonodactylidae Gonodactylus stanchi
Pseudosquillidae Pseudosquilla adiastata
Caridea 77 15%192 8%
Palaemonidae Pontonia sp.
Alpheidae Alpheus malleator
Alpheus lottini
Alpheus sp.1
Synalpheus digueti
Synalpheus nobilii
Synalpheus sp.
Anomura 14 3%20 1%
Porcellanidae Clastotoechus diffractus
Pachycheles biocellatus
Pachycheles panamensis
Pachycheles sp. 1
Pachycheles sp. 2
Petrolisthes edwardsii
Petrolisthes glasselli
Petrolisthes haigae
Petrolisthes sp. 1
Petrolisthes sp. 2
Brachyura 187 36%1923 79%
Majidae Mithrax denticulatus
Mithrax sp.
Thoe sulcata
Theleophrys cristulipes
Xanthidae Paracthea sulcata
Microcasiope xantusii
Xamthodius stimposoni
Liomera cintimana
Platyactea dovi
Pilumnus gonzalensis
Paraxanthias insculptus
Mollusca 152 30%124 26%199 8%
Cephalopoda 54 11%86 18%72 3%
Octopodidae Octopus hubbsorum
Octopus sp.
98 19%38 8%127 5%
Bivalvia 27 5%71%36 1%
Mytillidae Modiolus sp.
Unidentified No. 1
Unidentified No. 1
Unidentified No. 2
Unidentified No. 3
Gastropoda 71 14%31 6%91 4%
Muricidae Unidentified No. 1
Unidentified No. 2
Unidentified No. 1
Unidentified No. 2
Pisces 41 8%116 24%47 2%
Teleostei 41 8%116 24%47 2%
Muraenidae
Unidentified No. 1
Unidentified No. 2
Page 30 The Veliger, Vol. 51, No. 1

complete prey and fragments of several body structures
in different stages of digestion. Only a small percentage
(5%) was recorded as consisting of complete and
freshly eaten organisms, while almost 95%of the
material was fragmented or partially digested. Organ-
isms from seven taxonomic groups were identified
(Table 1): Thallophytes (macroalgae), Annelida, Ar-
thropoda (subphylum Crustacea), Mollusca, Echino-
dermata, Chaetognata, and Chordata (subdivision
Teleostei).
The taxonomic identification of crustaceans was
based on the carapaces, rostra, dactyls, chelipeds, other
appendages, and eggs in different stages of maturity. In
the case of gastropod mollusks, the identification was
made using the opercula and fragments of shells; in the
case of bivalve mollusks, using fragments of the valves
and the byssus. The octopod prey were recognized
using body fragments (arms, beaks, and lenses) or the
almost complete small juveniles; the egg masses of
other octopuses were also present in the stomachs.
Complete chaetognath individuals were found in the
samples, but only fragments of spines and body
fragments of echinoderms, including their characteristic
mouthparts. The polychaetes were identified using
body fragments with multiple appendages. Recently
caught fishes were almost complete, and other body
parts (spines, bones, scales, and otoliths) were also
present. Finally, the small pieces of macroalgae in the
samples are probably an indication of the habitat or
substratum where the prey were caught by the
octopuses.
Diet: The diet of O. hubbsorum is composed mainly of
members of three groups: mollusks, crustaceans, and
fishes. The crustaceans dominated in the samples,
according to the frequency of their occurrence in the
samples (57%), their weight (46%), and their number
(88%). The brachyuran decapods occurred in 36%of
the samples and represented 79%of the total number
of prey. Other decapod crustaceans, the carideans, and
anomurans, were less common in the samples (15%and
3%, respectively). The mollusks were the second most
important group, according to the frequency of their
occurrence in the samples (30%), their weight (26%),
and their number (8%). Cannibalism of O. hubbsorum
was important in frequency (11%) and weight (18%),
The Veliger veli-51-01-04.3d 24/11/09 22:32:41 31
Ocurrence (N) Weight (g) Number (N)
total %total %total %
Others 27 5%19 4%42 2%
Annelida Polychaeta Unidentified No. 1
Unidentified No. 2
Chaetognatha
Aphragmopohora Unidentified No. 1
Echinodermata
Diadimastidae Unidentified No. 1
Unidentified No. 2
Equinometridae Unidentified No. 1
Unidentified No. 2
Ophiuroidea Ophiocomidae sp.
Talophytas Padina sp.
Total 514 100%485 100%2445 100%
Table 1
Continued.
Table 2
Values of the Fullness Index (FI) for the females, males, and total individuals of Octopus hubbsorum. Content in the
digestive tract: I (empty), II (almost empty), III (half full), IV (full).
Females Males Total
IIIIIIIVIIIIIIIVIIIIIIIV
Juvenile 14.81 53.70 31.48 0 11.53 53.84 34.61 0 13.20 53.77 33.01 0
Adult 29.69 38.46 27.69 4.61 10.63 70.21 19.14 0 21.42 51.78 24.10 2.67
E. Lo´pez-Uriarte et al., 2009 Page 31

but it represented only 3%in number. Teleost fishes
were the third most important taxonomic group,
according to their occurrence in the samples (8%),
weight (24%), and number (2%); the presence of
juvenile moray eels (family Muraenidae) is probably
unusual for O. hubbsorum. Finally, the prey items
belonging to the phyla Talophyta, Annelida, Echino-
dermata, and Chaetognata showed percentages lower
than 5%in occurrence, weight, and number, and they
were combined in the group ‘‘others.’’ Most prey items
of this group were not identified to species, and some
were probably incidental, as in the case of the
macroalgae.
Fullness index (FI ): The results indicate that O.
hubbsorum feeds almost constantly in the area of study.
Most octopuses analyzed (126 females and 100 males)
contained prey in their digestive tracts with different
degrees of fullness. According to the Fullness Index
(FI), nearly 80%of the stomachs were in the categories
II (almost empty) or IV (full) (Table 2; Figure 3). The
amount of food in the stomachs was significantly
different among females and males (X
2
54.73; df 51;
P,0.05); the females recorded higher amounts than
males. The total population showed a tendency to
decrease the amount of food with the relative size of the
individuals. This tendency was more evident among the
females, more of which had stomachs in category II
(almost empty). Category IV (full) was observed only
in the stomachs of adult females. Although the values
of FI were higher during the warm–dry season, there
were no significant differences between the seasons of
the year (P.0.05). Females showed higher FI values
(.26%) than males during the period of study (X
2
5
8.72; df 53; P,0.03), except during the warm–dry
season (P.0.05) (Table 3).
Vacuity index (VI): Nearly 20%of the stomachs of O.
hubbsorum were empty. There were no significant
differences in the Vacuity Index (VI) between females
The Veliger veli-51-01-04.3d 24/11/09 22:32:41 32
Figure 3.
Table 3
Seasonal values of the Fullness Index (FI) for the females, males, and total individuals of Octopus hubbsorum.
Content in the digestive tract: I (empty), II (almost empty), III (half full), IV (full).
Females Males Total
I II III IV I II III IV I II III IV
Warm–wet 24.48 44.89 28.57 2.04 20 70 10 0 23.18 52.17 23.19 1.45
Warm–dry 7.69 53.84 38.46 0 12.5 45.83 41.66 0 10 50 40 0
Cool–dry 26.66 42.22 26.66 4.44 7.69 67.30 25 0 16.66 55.21 26.04 2.08
Page 32 The Veliger, Vol. 51, No. 1

The Veliger veli-51-01-04.3d 24/11/09 22:32:44 33
Figure 4.
Figure 5.
E. Lo´pez-Uriarte et al., 2009 Page 33

and males (P.0.05). Figure 4 shows the tendency of
the VI vary according to the maturity stage. There was
no significant difference in the VI between immature
and mature individuals (P.0.05). However, the
proportion of empty stomachs increased to nearly 85%
in the senescent females, and the value of the index was
significantly different (X
2
516.39, P,0.001). The
values of the males and females were not significantly
different in immature (P50.169) and mature (P5
0.056) individuals. On the other hand, there were
significant differences in the proportion of empty
stomachs observed between the seasons of the year.
The warm–wet season showed the highest proportion
of empty stomachs (37.82%), while the lowest was
observed in the cool–dry season (X
2
56.55, P50.038)
(Figure 5).
The Occurrence index (OI), the importance in weight
index (IWI), and the importance in number index (INI):
The relative importance of each group of prey
(crustaceans, mollusks, fishes, cephalopods, and the
group ‘‘others’’) depended of the index in which it was
expressed: OI,IWI or INI. The Kruskal-Wallis test
indicated differences between juveniles (60–110 mm
DML) and adults (.110 mm DML) in the indices of
occurrence (OI)(H541.61; P,0.005), weight (IWI)
(H 531.96; P,0.001), and number of prey (INI)
(H 520.17; P,0.028). The values of the three indices
increased between the interval of 65 mm and 110 mm
DML (Figure 6, 7, and 8), and decreased gradually
toward the larger sizes.
The IWI values showed differences in the feeding
habits between males and females of Octopus hubb-
sorum. The crustaceans and the group ‘‘others’’ were
preferred by males, while the females preferred the
mollusks (gastropods and bivalves) and fishes (Ta-
ble 4). In the cases of cannibalism (cephalopod prey),
there was no clear pattern of preference between sexes.
The variety and proportion of new prey items in the
diet increased with the size of the individuals. This was
more evident in the case of crustacean prey, which
declined in importance in the stomach contents as the
size of the octopuses increased from 75 mm to 160 mm
DML. Consequently, the importance of other prey
(gastropods, bivalves, cephalopods, fishes, and ‘‘oth-
ers’’) increased in these individuals, suggesting a change
in the feeding habits with increasing size. This pattern
was also observed in the IWI and INI (Figures 7 and 8).
The Veliger veli-51-01-04.3d 24/11/09 22:32:48 34
Figure 6.
Page 34 The Veliger, Vol. 51, No. 1

The Kruskal-Wallis tests indicate significant differences
in the values of IWI and INI between the size intervals
(H541.74, P,0.001; H520.17, P,0.028,
respectively).
Dietary comparisons of the different groups of prey
as a function of the size revealed that the mollusk prey
were more important in juvenile individuals (,110 mm
DML), while the cephalopod prey were more impor-
tant in the adults (.110 mm DML) of both sexes
(Table 4). The fishes were more important in the
juvenile females and in the adult males. No differences
were found in the crustaceans and the group ‘‘others’’
between juveniles and adults.
The IWI showed higher values in the inmature
individuals of both sexes for crustaceans and the group
‘‘others’’ (Table 5); similar results were found in
juveniles and adults (Table 4). The mollusks, cephalo-
pods, and fishes were more important in the mature
and senescent octopuses (Table 4b). The INI values
showed significant differences between sexes only in the
group ‘‘others’’: the males had more prey items from
this group (Table 6).
All groups of prey had variations in the values of OI,
IWI,andINI during the period of study (Figure 9). The
males showed a more evident pattern; the three indexes
had a tendency to increase from the warm–wet season to
the cool–dry season. The cool–dry season not only
showed the highest values of OI,IWI,andINI, but also
the highest proportion of cephalopods and teleost
fishes. The crustaceans were dominant at all times, with
values above 40%in both sexes. However, crustaceans
increased their occurrence (IO)andweight(IIW)inthe
samples during the warm–wet season (P,0.05), but
not their importance in number (IIN). The high
proportion of crustaceans in the digestive tracts during
the warm–wet season is remarkable, with percentages
between 81%and 97%for the three indexes. During the
warm–dry season, the mollusks were significantly more
important in the samples according to the OI and IWI
values (P,0.05), but not according to the INI value.
According to the OI and the IWI,thefemalesand
males followed a similar pattern, since the participation
of the five groups of prey increased from the warm–wet
season to the temperate–dry season. However, this
The Veliger veli-51-01-04.3d 24/11/09 22:32:51 35
Figure 7.
E. Lo´pez-Uriarte et al., 2009 Page 35

tendency was not clear with the INI. The participation
of crustaceans was always important, with values
between 40%and 90%of the INI. In general, mollusks
(gastropods, bivalves, and cephalopods) were best
represented during the warm period of the year
(warm–wet and warm–dry seasons).
DISCUSSION
AND
CONCLUSIONS
Previous studies on the diet of other species of Octopus
report that they are active carnivores that feed mainly
on crustaceans, mollusks, and fishes, while echino-
derms, polychaetes, chaetognaths, and siphonophores
form part of their diet in smaller proportions (Nixon,
1987; Guerra, 1978; Smale and Buchan, 1981; Am-
brose, 1984; Cortez et al., 1995; Grubert et al., 1999).
Additionally, these studies describe significant changes
in the relative importance of the prey as a function of
the sex, size, stage of maturity, and the season of the
year. The diet and feeding habits of O. hubbsorum in
the central Mexican Pacific is consistent with these
descriptions.
The method employed for assessing the diet is very
important, since some procedures may overemphasize
the importance of some kinds of prey relative to others.
For example, the use of traps to asses the diet of O.
vulgaris may result in a higher proportion of fishes
relative to other prey, especially invertebrates, because
octopuses and fishes were caught together in the traps
(Herna´ndez-Lopez, 2000). Also, a procedure based on
the collection of food debris around octopus middens
would not record the consumption of fishes (Ambrose
& Nelson, 1983; Ambrose, 1986; Mather, 1991). The
only previous record on the diet of O. hubbsorum was
based on this latter procedure (Raymundo, 1995),
which indicated only remains of crustaceans and shells
of gastropods and bivalves. The study of the content of
the digestive tracts has been commonly used to study
the diet of Octopus spp., and it is considered a reliable
method because it gives evidence of the consumption of
invertebrates and fishes with hard skeletons and shells
that may be used for taxonomic identifications.
A good evaluation of the diet of cephalopods should
take into consideration a sample size that represents the
different members of the natural populations, including
juveniles, adults, and the senescent of both sexes. The
sample size may be different according to the
cephalopod species. Shchetinnikov (1986) estimated
The Veliger veli-51-01-04.3d 24/11/09 22:32:54 36
Figure 8.
Page 36 The Veliger, Vol. 51, No. 1

The Veliger veli-51-01-04.3d 24/11/09 22:32:57 37
Table 4
Comparisons of the Importance in Weight Index (IWI) between sexes and size of the individuals of Octopus hubbsorum.*5significant, ** 5
highly significant.
Prey
Total Juveniles Adults Females Males
R=R=R =Juvenile Adult Juvenile Adult
Crustacea 55.81 ** 62.68 57.57 * 65.41 54.54 * 61.10 57.57 ns 54.54 65.40 ns 61.10
Mollusca 18.19 ** 8.78 21.21 ** 13.32 16.62 ** 5.89 21.21 * 16.62 13.32 ** 5.89
Cephalopoda 15.53 ns 13.47 6.66 * 10.93 21.02 * 15.09 6.66 ** 21.02 10.93 * 15.09
Teleostei 9.43 * 6.66 13.48 ** 2.78 6.79 ** 9.08 13.48 ** 6.79 2.78 ** 9.08
Other 1.01 ** 8.40 1.06 ** 7.55 1.01 ** 8.83 1.06 ns 1.01 7.55 ns 8.83
Total 100 %1749 1318 660 503 1089 815 660 1089 503 815
x
2
(g.l. 54) 161.4 86.9 125.6 79.4 43.6
p:,0.001 ,0.001 ,0.001 ,0.001 ,0.001
Table 5
Comparisons of the Importance in Weight Index (IWI) between sexes and stage of maturity of the individuals of Octopus hubbsorum.*5significant,
** 5highly significant.
Prey
Immature Mature Females Males
R=R =Immature Mature Senescent Immature Mature
Crustacea 58.52 ** 68.79 51.13 * 56.80 58.52 ** 51.13 ** 41.02 68.79 ** 56.80
Mollusca 19.01 ** 6.03 12.78 ns 11.25 19.00 ** 12.78 ** 36.41 6.03 ** 11.25
Cephalopoda 9.33 * 13.27 28.54 ** 13.88 9.33 ** 28.54 ** 10.76 13.27 ns 13.88
Teleostei 12.32 ** 0.51 7.00 ** 11.94 12.32 ** 7.00 ns 7.17 0.51 ** 11.94
Other 0.80 ** 2.72 0.52 ** 6.11 0.80 ns 0.52 ** 4.61 11.38 ** 6.11
Total 100%898 580 598 720 868 571 195 580 720
x
2
(g.l. 54) 194.1 71.3 96.3 80.8 89.11
p:,0.001 ,0.001 ,0.001 ,0.001 ,0.001
E. Lo´pez-Uriarte et al., 2009 Page 37

that approximately 20 stomachs per sample were
enough to describe the diet of squid populations from
the oceanic waters off Peru. Grubert et al. (1999) used a
sample of 137 male and female individuals to describe
the diet and feeding strategy of Octopus moarum along
the southeastern coast of Tasmania. In the Canary
Islands, Herna´ndez-Lo´ pez (2000) determined experi-
mentally that a minimum sample size of 13 stomachs
per month of Octopus vulgaris was sufficient to obtain
80%of the prey categories for this species. In the
present study, a sample of 226 individuals of O.
hubbsorum of both sexes from a wide range of sizes
and different stages of maturity were analyzed during
an annual cycle. The general coincidence in the feeding
habits of O. hubbsorum with other species of Octopus
and the ample variety of prey items found suggests that
the methodology and the sample size were satisfactory.
It is known that octopods are active hunters at night;
they search for food mainly during the sunrise and
sunset hours and make only short infrequent feeding
trips during the day (Mather & O’Dor, 1991; Mather,
1991). The time of the day may also affect their feeding
habits; for example, predation of O. vulgaris on fishes
may change during the diurnal and nocturnal periods
of the day (Nigmatullin & Ostapenko, 1976). Most
octopods digest rapidly; in some species, the digestive
process may last 14 hr at temperate temperatures
(Boucher-Rodoni et al., 1987); in the case of O. cyanea,
individuals required 12 hr to complete the digestion at
30uC (Boucher-Rodoni, 1973). Our observations sug-
gest that Octopus hubbsorum has nocturnal feeding
behavior because most individuals were caught during
the morning hours with food in their stomachs,
indicating that the prey had likely been eaten recently
or only a few hours before. However, since all
individuals were obtained from commercial catches
during a short time span (between 8:00 a.m. and 3:00
p.m.), there is no evidence of possible variations in the
predatory behavior as a function of the time of the day.
Future research should extend sampling to other
periods of the day to obtain a better knowledge on
the natural diet and the feeding habits of this species in
the central Mexican Pacific.
Octopus hubbsorum feeds on nearly 50 different prey
species during the year. This is a relatively broad diet,
compared with other species of Octopus; for example,
22 and 28 species were found in O. vulgaris (Ambrose &
Nelson, 1983; Mather, 1991), 25 species were found in
O. dofleini (Hartwick et al., 1981), and 12 species were
found in O. maorum (Grubert et al., 1999). However,
the dietary ranges of those other species are likely to be
greater, since all of those studies were performed in
relatively limited time spans (18 days to 8 months). The
diversity of prey items found in O. hubbsorum is
comparable with the 55 prey species found in a four-
year study of O. bimaculatus (Ambrose, 1984), which
The Veliger veli-51-01-04.3d 24/11/09 22:32:58 38
Table 6
Comparisons of the Importance in Number Index (INI) between sexes and stage of maturity of the individuals of Octopus hubbsorum.*5significant,
** 5highly significant.
Prey
Total Adults Immatures Females Males
R=R =R=Immature Mature Senescent Immature Mature
Crustacea 87.55 ns 88.72 87.15 ns 88.91 89.16 ns 91.06 89.16 ns 88.11 ** 64.15 91.06 * 86.44
Mollusca 5.82 ns 4.51 6.37 ns 4.41 5.62 * 2.98 5.62 ns 4.41 ** 22.64 2.98 * 6.02
Cephalopoda 3.42 ns 2.53 3.52 ns 2.62 2.19 ns 1.86 2.19 * 4.41 ns 5.66 1.86 ns 3.20
Teleostei 2.25 ns 1.50 2.37 ns 1.54 2.19 * 0.55 2.19 ns 2.20 ns 3.77 0.55 * 2.44
Other 0.94 ** 2.72 0.57 ** 2.50 0.82 ** 3.53 0.82 ns 0.84 ns 3.77 3.53 ns 1.88
Total 100%1376 1088 1051 839 729 537 729 589 53 537 531
x
2
(g.l. 54) 16.37 18.43 22.15 6.01 35.02 17.10
p:,0.003 ,0.001 ,0.001 0.198 ,0.00-
1
,0.002
Page 38 The Veliger, Vol. 51, No. 1

was considered the practical limit of prey for that
species.
Similar groups of prey have been reported in natural
populations of other species of Octopus,suchasO.
vulgaris (Nigmatullin & Ostapenko, 1976; Guerra,
1978; Hatanaka, 1979; Smale & Buchan, 1981; Sa´ nchez
& Obarti, 1993; Herna´ndez-Lopez, 2000), O. bimacu-
latus (Ambrose, 1984), O. mimus (Cortez et al., 1995)
and O. maorum (Grubert et al., 1999). All of those
species feed mainly on crustaceans, mollusks, and
teleost fishes, although their relative importance in the
diet varies as a function of the species.
The Veliger veli-51-01-04.3d 24/11/09 22:32:58 39
Figure 9.
E. Lo´pez-Uriarte et al., 2009 Page 39

Since cephalopods are opportunistic predators, they
should consume different prey according to their
availability. Therefore, the area in which the species
live should affect their diet (Nixon, 1987; Hartwick et
al., 1981; Ambrose, 1984). Thus, the same species may
have differences in the types of prey consumed as a
function of the distribution of the populations. This is
evident in the case of the populations of O. vulgaris
from the North Atlantic coast of Africa (Guerra, 1978)
and the Mediterranean Sea (Sa´nchez & Obarti, 1993).
The variety and availability of the prey is, in turn,
generally related to the complexity of the habitat.
Octopus hubbsorum is the target species in the
octopus fisheries of the Mexican Pacific (Aguilar-
Cha´ vez, 1995; Rı
´os-Jara et al., 2001). The fishermen
capture this species from the intertidal and shallow
subtidal zones to depths of 30 m during semiautono-
mous diving. This octopus is uncommon in the
intertidal zone, and it is typically found hiding in
crevices and small caves in the rocky and coralline
(stony coral) substrates that are more common in the
shallow areas. These substrates offer a variety of
microhabitats, and they support a wide selection of
potential prey species. Reports on the distribution and
abundance of benthic species of mollusks and crusta-
ceans from the coast of Jalisco indicate that the prey
species of O. hubbsorum are common in the shallow
subtidal environments in which this species lives
(Ya´n˜ez-Rivera, 1989; Schmidtsdorf, 1990; Lo´pez-Ur-
iarte & Rı
´os-Jara, 2004; Rı
´os-Jara et al., 2006).
There is no information on the bathymetric distri-
bution of O. hubbsorum. According to local fishermen
(personal communications), there are certain periods of
the year when larger individuals (adult females and
males) are found more frequently than usual at
shallower depths. This suggests seasonal vertical
movements of the adult individuals that may be related
to changes in the diet through a depth gradient. If the
senescent (postspawing) females of O. hubbsorum
behave like the senescent females of other octopus
species, then they reduce their feeding activity and
remain close to the eggs while brooding. Thus, they
would be found more frequently, during certain periods
of the year, in the crevices and caves of the shallower
rocky and coralline areas where fishermen usually dive.
These vertical movements could explain not only the
differences in the diet of the adult individuals but also
the seasonal differences in the prey composition found
through the year of study.
The feeding strategy of O. hubbsorum is complex.
The size, state of maturity, and sex of the individuals
influenced their diet. The importance of the different
prey species changes as the octopus grows and new
species are added to the diet. The larger (.65 DML)
adult and senescent individuals of O. hubbsorum
increased the proportion of cephalopods, fishes, and
the group ‘‘others’’ in their diet, and they reduced the
consumption of crustaceans and mollusks. These
individuals ingested proportionally more types of prey
than the juveniles. This is a common feature of
cephalopods (Boucher-Rodoni et al., 1987; Hanlon &
Messenger, 1996), and it has also been documented in
other species of Octopus (Nigmatullin & Ostapenko,
1976; Guerra, 1978; Castro & Guerra, 1990; Cortez et
al.,1995).
However, Herna´ndez-Lo´pez (2000) reported some
overlap in the diet among juveniles and adults of O.
vulgaris. Other reports on feeding habits of cephalo-
pods suggest that there is not a large difference between
the diet of juveniles and that of adults among the
coastal species of octopuses (Boucaud-Camou &
Boucher-Rodoni, 1983; Bouche-Rodoni et al., 1987).
In the case of O. vulgaris, Guerra (1978) reported a
change in the diet with respect to a depth gradient,
particularly in the importance of the species of
crustaceans consumed.
There were also significant differences in the diet
between adult males and females of O. hubbsorum,
which were probably related to the higher reproductive
costs of females. A higher proportion of food by weight
in adult females than in adult males of O. mimus has
been associated with differences in the nutritional needs
of the two sexes (Cortez et al., 1995). Female octopuses
require more energy for reproduction than males
(O’Dor & Wells, 1978). In O. vulgaris, the high
deposition of lipids in the yolk has been considered as
a limiting factor for egg production by adult females
(O’Dor et al., 1984). This may be true also of O.
hubbsorum on the coast of Jalisco.
Octopus hubbsorum had a higher proportion of
empty stomachs in mature and senescent females than
in males of the same stages. A similar condition has
been reported in other species, such as O. mimus, from
the coast of Chile (Cortez et al., 1995); the mature
females of this species have less opportunity of catching
prey (Mangold, 1987). This effect has been attributed
to an inhibition of the appetite due to hormonal
changes during this stage in the life cycle (Wodinsky,
1978). Also, the senescent females of O. hubbsorum
ingested proportionally more items of the group
‘‘others’’ than did the senescent males. Cortez et al.
(1995) suggested that the increased ingestion of the
group ‘‘others’’ among the senescent females of O.
mimus may be related to a reduction in their feeding
activity associated with their need to remain close to
the eggs while brooding, so that they tend to ingest
more of the food available around the octopus
middens, including those small and not very motile
invertebrates of the group ‘‘others.’’
During the annual cycle, the composition of the diet
of O. hubbsorum did not vary very much; the
crustaceans were dominant at all times, with values
The Veliger veli-51-01-04.3d 24/11/09 22:33:03 40
Page 40 The Veliger, Vol. 51, No. 1

above 40%in both sexes. The other groups of prey had
variations in their occurrence, weight, and number,
depending on the sex and the season of the year. The
males did not feed on cephalopods and fishes during
the warm–wet season, while females did not feed on the
group ‘‘others’’ during the warm–dry season. However,
variations in the proportions of prey items were evident
among the seasons of the year. This behavior is similar
to that reported for O. mimus, in which the main prey,
the fishes, decline in proportion during fall and winter
as the importance of other prey, such as crustaceans,
increases (Cortez et al., 1995). There is a similar change
in the diet of O. vulgaris, in which fishes and octopods
that constitute the main items of prey during winter
and spring are replaced by crustaceans at the beginning
of summer.
In summary, the diet and feeding habits of O.
hubbsorum in the central Mexican Pacific are consistent
with previous descriptions for other Octopus spp.
Species-specific related behavior could be the cause of
some differences, but these variations may also be
related to the regional distribution of the populations
studied. The results of the present study indicate that
O. hubbsorum is an opportunistic predator that feeds
during the night on a wide variety of prey. More
detailed studies using different sampling methodologies
at different times of the day and night are needed to
allow us to learn more about the natural diet and the
feeding habits of this species.
Acknowledgments. Our thanks to local fishermen at Careyes,
Punta Pe´rula, and Chamela for providing the individuals of
Octopus hubbsorum used in this study. The professors and
students of the Laboratorio de Ecosistemas Marinos y
Acuicultura helped during data collection in the field. This
work had the financial support of SIMORELOS-CONACyT
(Project No. 1998-03-06-21) and Universidad de Guadalajara,
Me´xico.
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playas rocosas de la costa del estado de Jalisco, Me´xico.
Tesis de Licenciatura. Facultad de Ciencias, Universidad
de Guadalajara. Guadalajara, Me´xico.
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Authors Queries
Journal: The Veliger
Paper: veli-51-01-04
Title: Diet and Feeding Habits of Octopus hubbsorum Berry, 1953,
in the Central Mexican Pacific
Dear Author
During the preparation of your manuscript for publication, the questions listed below have arisen. Please attend to these
matters and return this form with your proof. Many thanks for your assistance
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Reference
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for all figures?
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E. Lo´ pez-Uriarte et al., 2009 Page 43