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Diet of Octopus bimaculatus verril, 1883 (cephalopoda: octopodidae) in Bahia de Los Angeles, Gulf of California.

ABSTRACT Two hundred sixty-one octopuses were obtained from August 2006 to June 2007 in Bahia de Los Angeles, BC, Mexico. Sizes ranged from 58-190 mm in mantle length. Diet was determined from 3 sources: the digestive tract analysis (hard rests), accumulations of hard prey remaining in refuges, and live prey present during capture. Ripe females had the greatest fullness weight index (FWI) whereas spawning/spent females had the lowest. During the spring, female and male octopuses showed the greatest FWI, whereas in summer they showed the lowest, coinciding with the spawning/spent stage. A total of 76 prey items from 8 phyla were found, with Mollusca being the most important phylum and xanthid crabs the most important prey year-round. During autumn and winter, more bivalves were consumed, whereas more crabs were consumed in spring. Males fed mainly on crabs during all gonad development stages, but spent males fed mostly on molluscs. In contrast, females fed mostly on molluscs, except ripe females, which included more crabs in their diet. The octopus Octopus bimaculatus appears to be a specialist consumer, and this selectivity could be a consequence of different energetic demands of each sex during the gonad ripening process.

KEY WORDS: food preference, diet, midden, digestive tract analysis, California two-spotted octopus, Octopus bimaculatus

INTRODUCTION

The California 2-spotted octopus Octopus bimaculatus Verril, 1883, is 1 of the most abundant species in the commercial catches of the Gulf of California coast. It is distributed from Santa Barbara, CA, to the southern Baja California Peninsula, and within the Gulf of California from Puerto Penasco, Sonora and San Felipe, BC, to Bahia de La Paz, BCS. (Hochberg & Fields 1980). It inhabits intertidal and subtidal rocky coasts, where it finds appropriate refuges to hide from predators and spawn (Ambrose 1982).

Octopuses play an important role in the marine environment as both predators and prey (Nixon 1987, Guerra 1992). An understanding of their trophic relationships would help in determining the structure and function of marine ecosystems (Cherel & Hobson 2005). In addition, knowledge of their feeding habits is a key aspect that has a bearing on the survival and growth of these organisms in captivity (Nixon 1966). Octopuses consume a wide variety of prey, including crustaceans and molluscs (Nixon 1987); however, their diet can be influenced by preference and by prey availability (Ambrose 1984), which has consequences for the community. Also, modifications to their feeding behavior and food ingestion are associated with the gonad ripening process (Cortez et al. 1995), although this aspect has not been well studied despite its biological relevance. In general, a decrease in food ingestion has been observed in ripe and broody females of different octopus species in captivity (Joll 1976, Wodinsky 1978, Mather 1980, Smale & Buchan 1981), as well as in the wild (Lopez-Uriarte et al. 2010). This has been confirmed indirectly by a high incidence of ripe females with empty stomachs (Quetglas et al. 2005) as well as by a decrease of energetic reserves in the digestive gland (O'Dor & Wells 1978, Cortez et al. 1995, Zamora & Olivares 2004) and in muscle (Zamora & Olivares 2004).

In general, the study of wild octopus diets is based on stomach content analysis; however, the fragmented state of the stomach contents, caused by the mechanical action of the beak, complicates the analysis. In this sense, only prey with hard pieces can be identified, such as molluscs (shells smaller than the aperture of the mandibular apparatus), crustaceans (exoskeletal fragments), and fish (bones) (Villanueva 1993, Quetglas et al. 1998, Hernandez-Lopez 2000, Cardoso et al. 2004, Quetglas et al. 2005). Another technique used in diet studies is based on the fact that octopuses discard large, hard prey parts, such as crustacean exoskeletons, mollusc shells, or sea urchin tests, which accumulated around their refuge and can be identified and quantified (Ambrose 1982, Ambrose 1983, Ambrose & Nelson 1983, Mather & O'Dor 1991, Dodge & Scheel 1999, Smith 2003). In the literature both techniques are used separately and combined (Smale & Buchan 1981, Cortez et al. 1995), and a third technique, based on direct observation of in situ feeding, has been also used (Smith 2003), which gives a better approximation to the feeding habits of these organisms.

The objective of the current study was to determine the diet of Octopus bimaculatus in Bahia de Los Angeles, combining the three sampling techniques, and analyzing the diet variation in relation to season, sex, and gonad development stage.

MATERIALS AND METHODS

This research was carried out on a dense octopus population in Bahia de Los Angeles, Mexico, on the northwest coast of the Baja California Peninsula (28[degrees]55' N, 113[degrees]30' W) within the Gulf of California. This bay is surrounded by numerous small islands (Barnard & Grady 1968); it has a sandy bottom, and large rocks with fissures and cavities that are used by octopuses as a refuge. The mouth of the bay adjoins Channel de Ballenas, and the water exchange between the channel and the bay allows the mixing of cold water (rich in nutrients) with warm bay waters, which provide primary and secondary productivity in the area year-round and results in high biodiversity (Bustos-Serrano et al. 1996, Delgadillo-Hinojosa et al. 1997).

Samples were obtained from August 2006 to June 2007 between 0800 and 1100 hr by diving with an air compressor "hookah" and catching the octopuses with hooks. Each month, 20-30 different-size Octopus bimaculatus were caught at a depth of 5-12 m. Along with each octopus, recent accumulations of hard prey remains found in the refuge were collected. Some prey that were being ingested by the octopuses at the time of capture were also collected and were recorded as "live prey" observations.

In the laboratory, sex (by direct observation of gonads), total weight (TW) in grams, and the mantle length (ML) and total length (TL) in millimeters were recorded for each organism. The digestive tract was extracted and stored at -20[degrees]C for additional analysis. The gonad development stage was determined histologically as immature, developing, ripe, spawning, or spent (Olivares-Paz et al. 2001, Rodriguez-Rua et al. 2005).

After thawing, the digestive tract (crop and stomach) contents were weighed and preserved in 70% alcohol for additional analysis. The hard rests were used to identify the prey. The fullness weight index (FWI) was calculated as the percent ratio of the weight of the digestive tract contents to the total weight of the organism less the empty digestive tract weight (Hyslop 1980). To assess significant differences in FWI for females, males, and combined among seasons, and gonad development stages, Kruskal-Wallis tests were used.

Taxonomic Identification of Prey

Prey were identified to the minimum possible taxonomic level (with each considered as 1 item) using specialized keys according to the taxonomic group: crustaceans (Brusca 1980, Hendrickx 1995, Kerstitch & Bertsch 2007), bivalves and gastropods (Keen 1971, Brusca 1980, Poutiers 1995), fish (Heemstra 1995, Sommer 1995), polychaetes (Brusca & Brusca 2005), sea urchins and ophiurans (Kerstitch & Bertsch 2007). Echiuran worms and sipunculids were identified by the presence of chetae in the digestive tract (Fisher 1946, Brusca 1980, Brusca & Brusca 2005). Food in an advanced state of digestion was labeled as unidentified organic matter and was quantified as 1 U for each digestive tract in the analysis of frequency of occurrence (FO) only.

Diet Analysis

The diet was analyzed by taking into account information obtained with the three sampling methods (digestive tract, accumulation of prey remains in the refuge, and observation of live prey). The importance of each item (prey category) was determined with two quantitative methods: FO (calculated as the percent ratio of the total number of stomachs containing a given item with respect to the total number of stomachs containing food) (Cailliet et al. 1996) and number (calculated as the percent ratio of the total number of individuals of a prey item with respect to the total number of prey items).

Data were grouped by season--summer (August and September 2006), autumn (October to December 2006), winter (January to March 2007), and spring (April to June 2007)--by sex, and by gonad development stage (immature, developing, ripe, spawning, and spent) (assigned histologically to the same specimens by Castellanos-Martinez 2008). The two immature males were grouped with the developing males and the four spawning/spent females were also grouped because they were of similar size and they fed on the same prey. To compare diets, items were grouped as follows: crabs, bivalves, gastropods, echiurans, fish, and other prey.

To determine the general diet width by sex and by gonad development stage, Levin's index (B) was used with the frequency of occurrence. B values more than 3.0 denote generalist predators; B values less than 3.0 denote specialist predators (Hurlbert 1978).

RESULTS

Two hundred sixty-one Octopus bimaculatus were collected, 120 (46%) were female and 141 (54%) were male. Males measured from 58-190 mm in ML (average ML, 114 [+ or -] 29 mm (SD)) and weighed between 115 g and 2,200 g TW (average TL, 635 [+ or -] 434 g). Females measured from 54-240 mm in ML (average ML, 118 [+ or -] 37 mm) and weighed between 130 g and 3,415 g TW (average TW, 720 [+ or -] 585 g). After reviewing the 261 octopuses sampled, only 203 contained food; 83% had food in the digestive tract, 39% had accumulations of prey remains in their refuge, and 4% had live prey during capture (Fig. 1).

From the total sample, it was possible to assign a gonadal development stage to 87 females and 97 males only, and 5 females contained no food. For the analysis of diet composition by gonad development stage, 82 females with food were analyzed: 41 immature, 14 developing, 23 ripe, and 4 spawning/spent (1 spawning, 3 spent). In addition, 97 males with food were analyzed: 18 immature/developing (2 immature, 16 developing), 47 ripe, and 17 spawning.

General Diet Description

A total of 1,138 prey corresponding to 76 items or prey categories were identified, belonging to 8 phyla: Arthropoda, Mollusca, Echiura, Sipuncula, Echinodermata, Ectoprocta, Annelida, and Chordata. All these phyla were recorded in the digestive tract, 4 were recorded in prey accumulations, and only 3 were noted in live prey (Table 1).

Molluscs were most abundant (52.7% FO), mainly in digestive tracts and accumulations, followed by arthropods (crustaceans) (42.9%) and echiurans (22.2%). Similarly, molluscs were the most abundant phylum in the diet (46.3% N) and included the greatest number of prey categories, followed by arthropods (crustaceans; 44.9%), and echiurans (5%; Table 1).

Unidentified organic matter was the most common item in the digestive tract (45.8% FO), which highlights the high digestion state of prey. When considering all sampling techniques, the most frequent item was xanthid crabs (29%), followed by Echiurus spp. (22.2%), Megapitaria squalida (20.2%), and, in minor amounts, Trigoniocardia biangulata, unidentified gastropods, Glycymeris gigantea, portunid crabs, Euvola vogdesi, and Glycymeris multicostata (Table 1).

Considering all sampling techniques, the xanthid crabs represent a third of the diet (36% N), followed by the bivalve Megapitaria squalida, the worms Echiurus spp., Glycymeris gigantea, Trigoniocardia biangulata, Glycymeris multicostata, and portunid crabs (Table 1).

Seasonal Changes in Diet Composition

During winter and autumn, a high frequency of octopuses had food (considering all sampling techniques; 84% and 83%, respectively), whereas during summer only 55% had food. The greatest abundance of food items from digestive tracts was recorded during autumn, from accumulations during winter, and from live prey during spring (Fig. 1). Significant differences in FWI combined values were found between spring and summer (Kruskal-Wallis, H = 11.42, P < 0.05; Table 2).

Considering all sampling techniques, seasonal changes in diet composition were observed (Fig. 2). Xanthid crabs were a main item consumed during all seasons, although with different importance. During summer, in addition to xanthid crabs (27% FO, 22% N) and echiuran worms (32% FO, 12% N), octopuses also consumed portunid crabs, the concave scallop Euvola vogdesi, and fish in similar proportions. During autumn, xanthid crabs (22% FO, 28% N) and echiuran worms (32% FO, 10% N) were also important, but the consumption of bivalves such as Megapitaria squalida (14% FO, 8% N) and Trigoniocardia biangulata (15% FO, 6% N) increased. During winter, more prey was noted, but Echiurus spp. were not consumed; xanthid crabs were important (26% FO, 26% N), but molluscs such as M. squalida, Glycymeris gigantea, T. biangulata, and Dosinia ponderosa (all more than 24% FO) increased in the diet. In spring, the crabs dominated the Octopus bimaculatus diet completely--in particular, xanthid crabs (61% N), which were present in almost half of all digestive tracts (47% FO). With regard to the unidentified organic matter, autumn had the highest FO value (52%), followed by summer (46%), winter (40%), and spring (30%).

Diet Composition by Sex

The FWIs by sex are presented in Tables 2 and 3. Both, males and females consumed xanthid crabs preferably; however, the importance of secondary prey was different between them. Females consumed, in order of importance, more echiuran worms (24% FO, 7% N) followed by Megapitaria squalida (14% FO, 10% N), whereas males inverted them: M. squalida (25% FO, 9% N) followed by echiurans (24% FO, 5% N; Fig. 3). Crabs were consumed more by males than females, whereas bivalves were consumed less by males than females.

Diet Composition by Gonad Development Stage

Significant differences were found in FWIs by gonad development stage in females (Kruskal-Wallis, P = 0.14; Table 3). The greatest value was recorded for ripe females (0.53 [+ or -] 0.45), and the lowest for spawning/spent females (0.02 [+ or -] 0.01). No significant differences were found in FWIs for the gonad development stages of males.

In general, a tendency toward increasing crab consumption with gonad development was observed, with the greatest crab consumption by ripe octopuses (Figs. 4 and 5, and Table 4). Bivalves seemed to have a greater importance to immature and developing stages of both males and females, but their importance diminished during the ripe stage. Consumption of echiuran and "other prey" (such as fish, echinoderms, and octopuses) was the maximum in ripe females. Immature females had a diet composed mainly of xanthid crabs, gastropods, echiuran worms, and, in a lesser proportion, Megapitaria squalida and Glycymeris multicostata bivalves (Fig. 4). Developing females consumed in number more xanthid crabs, but in frequency more M. squalida. Ripe females consumed mainly xanthid and portunid crabs, and increased the consumption of echiurans. The spawning/spent females consumed less prey. Two females contained only unidentified organic matter; one contained a unidentified decapod and one contained 2 bivalves (Glycymeris gigantea and Gari regular is).

Immature/developing males had the most diverse diet. Their most important prey were xanthids, Megapitaria squalida, echiurans, and bivalves such as Glycymeris multicostata and Trigoniocardia biangulata (Fig. 5). The diet of ripe and spawning males was based almost exclusively on xanthid crabs, and bivalves were secondary prey (mainly M. squalida). However, bivalves were more important in spent males.

Diet Width

According to Levin's index obtained in this study for the whole sample (2.6), Octopus bimaculatus is a specialist consumer. The Levin's index calculated for females was greater (2.8) than for males (2.2), but both are categorized as specialist consumers. In the same manner, the Levin's index obtained for each gonad development stage (immature females, 2.3; developing females, 1.4; ripe females, 1.7; immature/developing males, 2.7; ripe males, 2.0; spawning males, 1.2), confirm that O. bimaculatus is a specialist consumer.

DISCUSSION

Prey proportions can vary daily or seasonally, and therefore octopuses can exhibit feeding cycles that reflect this availability (Hanlon & Messenger 1998). In this sense, there are two possible explanations for the significantly low FWIs found in summer. On one hand, they could be attributed to a faster digestion as a consequence of warmer temperatures (26-32[degrees]C) reported in Bahia de Los Angeles during summer (Yee-Duarte et al. 2009); the complete digestion of stomach contents is estimated to last 16 hours at 14[degrees]C and 12 hours at 18-19[degrees]C (Boucher-Rodoni et al. 1987). On the other hand, a greater number was found during the summer in spawning/spent octopuses (26% females and 31% males) compared with other seasons (Castellanos-Martinez 2008), when it consumes less food. In this sense, it was found that ripe females had significantly greater FWIs whereas spawning/spent females had significantly lower FWIs than the other stages. It has been noted that females decrease food ingestion considerably during egg care (Mather 1980, Mangold 1987, Cortez et al. 1995, Lopez-Uriarte et al. 2010), although this decrease can be similar in males and females (Quetglas et al. 2005). Garcia-Garcia and Aguado-Gimenez (2002) reported greater ingestion rates for Octopus vulgaris females before maturity. Mather (1980) also mentions that physiological changes during female maturation cause a notable increase in food ingestion 2-3 wk before egg laying, when females need more nutrients and energy for egg production.

In agreement with our results, it is better to use the combined three sampling methods (digestive tract, accumulation of prey remains in the refuge, and observation of live prey) for diet analysis in octopuses. The prey obtained with each technique used was as expected--in accumulations, mainly molluscs; in stomach contents, crabs. Samples of live prey (being eaten by octopuses) were useful in two senses: first to confirm that the bivalves found in accumulations were used not only for modification or hiding of the refuge (Smith 2003), and second, they were key to identifying the genus of echiuran worms (recognized by chetae in the digestive tract), which have not been reported previously as prey in octopus diets. Therefore, this kind of sampling was shown to be valuable. Similarly, large crabs and other crustaceans such as lobsters may be detected only as part of the diet of octopuses by direct observation during feeding because they are consumed without their exoskeleton, with the muscle and viscera predigested externally (Ghiretti 1959, Nixon & Boyle 1982, Nixon 1987). Although exoskeletons are discarded near the refuge, they are removed rapidly by currents (Ambrose 1984). Consequently, the xanthid crab Glyptoxanthus meandricus and the decapods Eurypanopeus sp., Speloeophorus schmitti, and Ala cornuta are potential prey, because they were observed commonly during this study in the area.

In several cases, an important relationship between diet composition (and food selection) and the good condition of an organism has been shown, which ensures reproductive success (Jaeger & Lucas 1990). In this case, xanthid crabs were the most important prey of Octopus bimaculatus, such as for Octopus hubbsorum (Lopez-Uriarte et al. 2010). In this sense, it has been shown that farmed octopuses grow more when fed crabs compared with other prey (Nixon 1966, Cagnetta & Sublimi 2000, Dominguez et al. 2004), which was associated with high efficiency in making use of crustacean protein (Garcia-Garcia & Aguado-Gimenez 2002). This supports the high percentage of crabs found in the total diet of O. bimaculatus and, in turn, may explain the larger size and weight that O. bimaculatus reaches in Bahia de los Angeles (mean 116 mm ML and maximum 240 mm ML; mean 696 g TW and maximum 2950 g TW) compared with the reached in the coasts of California, U.S.A. (70-76 mm ML, and 283-556 g TW) (Ambrose 1997). Unlike octopuses in Bahia de Los Angeles, where crabs form a basic part of the diet. In California, O. bimaculatus feed mainly on gastropods (Ambrose 1984).

Our results indicate that males consumed mainly xanthid crabs (mainly ripe and spawning ones), whereas females consumed these crabs in less proportion, even to the extreme that, in spawning/spent females, xanthid crabs were not found. A greater consumption of crabs by males compared with females was found also for Octopus mimus and Octopus hubbsorum (Cortez et al. 1995, Lopez-Uriarte et al. 2010). Crabs could be providing males with a body coloration that is attractive to females, or they could be helping them grow and reach larger sizes, contributing to their reproductive success in two ways.

On the other hand, females cease feeding after spawning because they cannot leave their eggs (Mangold 1987). In this study, 9 females were found caring for eggs; however, five had empty digestive tracts (and were eliminated from the analysis), and the remaining four ate mainly bivalves. In the same manner, Octopus mimus senescent females consume mainly bivalves (Cortez et al. 1995), whereas female Octopus hubbsorum are even cannibalistic (Lopez-Uriarte et al. 2010). Senescent females are weakened and avoid investing time and effort capturing prey that need to be hunted and leaving the eggs unguarded; therefore, they increase their consumption of non-habitual prey (Cortez et al. 1995).

Bivalves comprised the greatest number of prey items (n = 32), and Megapitaria squalida, Trigoniocardia biangulata, and Glycymeris gigantea were important in the diet. These species and the other bivalve species as a whole were very relevant in the diet. However, the importance of bivalves and almost all gastropods in the diet could be overrated because they were counted from accumulations of hard prey remains, which can last several days, compared with prey found in the digestive tract, which last only a few hours (Smith 2003). It has been reported that cephalopods feed according to prey size and availability, as well as inherited according to feeding patterns and individual experience.

Several authors have mentioned that preferences or individual specialization toward certain prey can exist in cephalopods (Hartwick et al. 1984, Iribarne et al. 1991, Mather & O'Dor 1991, Grubert et al. 1999, Anderson et al. 2008); however, these authors did not consider factors such as sex and gonad development stage, which may have influence on diet variations. Only some studies, as ours, have considered such factors in the analysis of diet (Cortez et al. 1995, Hernandez-Lopez 2000, Lopez-Uriarte et al. 2010). In the current study, Octopus bimaculcitus was characterized as a specialist predator according to Levin's index (B < 3). However, specialization behavior increases with gonad ripeness; males focus on crab consumption and females focus on crabs, bivalves, and echiurans. This index has frequently been used to determine diet width in several species, among them octopuses such as Octopus vulgaris (B = 5.7) in the Mediterranean (Ambrose & Nelson 1983), Octopus dofleini (B = 5.2) on the Alaska coast (Hartwick et al. 1984), Octopus maorum (B = 4.5) on the Australian coast (Grubert et al. 1999), and O. bimaculatus (B = 5.8) on the California, USA, coast (Ambrose 1982). All cases, and particularly O. bimaculatus, appear in those studies as generalists (B > 3.0), contrasting with our results. The condition of specialist predator can be a function of the octopuses' ability to learn individually which prey are more available or found more easily during foraging (Anderson et al. 2008), and a function of different personalities (Mather & Anderson 1993). In addition, if the habitat is diverse and there is enough food from which to choose, the octopus will select food according to physiological demands (e.g., the different stages of gonad development, as found in this study). From this, we can deduce that diet selectivity in ripe males and females could respond mainly to the same function, and even helps develop a tolerance for the longer fasting and debilitation of the last life stage.

The high productivity near Bahia de Los Angeles probably provides Octopus bimaculatus with more food options. It shows a selective behavior toward prey (crabs and bivalves), as the optimum foraging theory predicts. When the food density is high, predators specialize on good-quality prey and ignore prey with lower food value (Schoener 1971).

ACKNOWLEDGMENTS

We thank Instituto Politecnico Nacional (SIP 20060858 and 20070360) and Pronatura Noroeste for funding this work. J. Armendariz-Villegas was a fellow student of PIFI (IPN) and CONACyT, and the results presented here are part of her MS thesis. B. P. Ceballos-Vazquez, M. Arellano-Martinez, and A. Abitia-Cardenas received grants from SIBE (COFAA) and EDI (IPN). They and U. Markaida are members of SNI-CONACyT. We thank the following specialized personnel who helped in prey identification: M. Diaz and E. Gonzalez-Navarro (UABCS), and E. Felix-Pico, L. Burnes-Romo, and D. Herrero-Perezrul (CICIMAR-IPN). Thanks to Myla Young and Emmanuel O. Vaughan for revising the English manuscript.

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ELISA JEANNEHT ARMENDARIZ VILLEGAS, (1) BERTHA PATRICIA CEBALLOS-VAZQUEZ, (1) UNAI MARKAIDA, (2) ANDRES ABITIA-CARDENAS, (1) MARCO ANTONIO MEDINA-LOPEZ (3) AND MARCIAL ARELLANO-MARTINEZ (1) *

(1) institute Politecnico Nacional-CICIMAR, Av. Institute Politecnico Nacional sjn. Col. Playa Palo de Santa Rita, La Paz, Baja California Sur, 23096 Mexico; (2) Colegio de la Frontera Sur, Unidad Campeche, Calle 10 X 61 #264, Col. Centro, Campeche, Campeche, Mexico; (3) Universidad Autonoma de Baja California Sur, Carretera a! Sur km. 5, La Paz, Baja California Sur, Mexico

* Corresponding author. E-mail: marellam@ipn.mx

DOI: 10.2983/035.033.0129

TABLE 1.
Prey in the diet of Octopus bimaculatus found in
the total sample and by sampling technique.

                                         Total

Item                                  FO          n

Arthropoda                          42.9        44.9
Crustacea, ni                        1.0         0.2
Ostracoda                            1.0         0.2
Decapoda (shrimp)                    3.0         0.5
Alpheidae                            0.5         0.1
Decapoda (crab)                      5.9         1.1
Diogenidae                           0.5         0.1
Lithodidae                           4.9         2.5
Brachyura, ni                        2.0         0.4
Portunidae
  Portunidae, ni                     9.9         3.6
  Portunus xantusii                  0.5         0.2
Leucosidae
  Speleophorus schmitti              0.5         0.1
  Xanthoidea                        29.1        35.9
Mollusca                            52.7        46.3
Bivalvia total                      38.9        39.3
Bivalvia, ni                         1.0         0.2
Anomidae
  Placuanomia cumingii               0.5         0.1
Arcidae
  Arcidae, ni                        0.5         0.1
  Anadara multicostata               9.9         2.9
  Barbatia reeveana                  0.5         0.1
Cardiidae
  Papyridea aspersa                  5.9         1.2
  Trigoniocardia biangulata         13.8         4.2
Carditidae
  Cardita affinis                    1.0         0.4
Crassatellidae
  Eucrassatella digueti              1.0         0.3
Glycymeridae
  Glycymeridae, ni                   1.0         0.2
  Glycymeris gigantea               11.3         4.5
  Glycymeris multicostata            8.9         3.7
Mytillidae
  Mytella guayanensis                2.5         0.4
Pectinidae
  Argopecten ventricosus             3.4         0.7
  Euvola vogdesi                     9.9         3.1
  Nodipecten subnodosus              1.0         0.3
Ostreidae
  Myrakeena angelica                 1.0         0.3
Psammobiidae
  Gari regularis                     3.0         0.6
Plicatulidae
  Plicatula spp.                     0.5         0.1
Veneridae
  Veneridae, ni                      1.0         0.3
  Chione californiensis              4.9         1.2
  Chione pulicaria                   0.5         0.1
  Chione lumens                      1.0         0.2
  Chione undatella                   2.5         0.4
  Dosinia ponderosa                  8.4         2.4
  Megapitaria auriantiaca            2.0         0.4
  Megapitaria squalida              20.2         9.2
  Pitar spp.                         0.5         0.1
  Protothaca grata                   2.5         1.2
  Ventricolaria spp.                 0.5         0.1
  Transennella puella                2.0         0.4
  Gastropoda total                  27.6         7.0
  Gastropoda, ni                    13.3         3.0
Bullidae
  Bulla spp.                         0.5         0.1
  Bulla punctulata                   1.0         0.2
Buccinidae
  Cantharus spp.                     0.5         0.1
  Cantharus elegans                  0.5         0.1
Cancellaridae
  Cancellaria spp.                   0.5         0.1
Calyptraeidae
  Crepidula spp.                     0.5         0.1
  Crepidula excavata                 0.5         0.1
  Crepidula onix                     0.5         0.1
  Crucibulum spinosum                4.9         0.9
Muricidae
  Murex recurvirostris               0.5         0.1
Naticidae
  Polinices bifasciatus              1.5         0.3
  Polinices recluzianus              0.5         0.1
Ollividae
  Ollivella spp.                     0.5         0.1
Strombidae
  Strombus granulatus                1.0         0.2
Trochidae
  Tegula spp.                        1.5         0.4
Turbinidae
  Turbofluctuosus                    5.9         1.3
Cephalopoda
Octopodidae
  Octopus spp.                       3.0         0.5
Echiura
  Echiurus spp.                     22.2         5.0
  Sipuncula                          1.5         0.4
  Echinodermata                      5.4         1.0
  Acroechionoidea (irregularia)      0.5         0.1
  Echinoidea, ni                     2.5         0.4
Ophiodermatidae
  Ophioderma panamense               0.5         0.1
Ophiothricidae
  Ophiothrix spiculata               2.0         0.4
Ectoprocta
Onychocellidae
  Floridina antiqua                  0.5         0.1
Annelida
  Polychaeta, ni                     1.5         0.3
  Chordata                           5.4         1.1
Urochordata
  Ascidacea, ni                      0.5         0.1
Clavellinidae:
  Archidistoma pachecae              0.5         0.1
Teleostei
  Teleostei, ni                      3.0         0.5
  Huevos de Pez                      1.0         0.2
  Kyphosidae                         0.5         0.1
Labridae
  Halichoeres nicholsi               0.5         0.1
UOM                                 38.9         0.0
Total general                      296.6       100

                                     Digestive tract

Item                                  FO          n

Arthropoda                          51.5        78.6
Crustacea, ni                        1.2         0.3
Ostracoda                            1.2         0.3
Decapoda (shrimp)                    3.6         0.9
Alpheidae                            0.6         0.2
Decapoda (crab)                      7.1         2.0
Diogenidae                           0.6         0.2
Lithodidae                           6.0         4.5
Brachyura, ni                        2.4         0.6
Portunidae
  Portunidae, ni                    11.9         6.3
  Portunus xantusii                  0.0         0.0
Leucosidae
  Speleophorus schmitti              0.0         0.0
  Xanthoidea                        35.1        63.3
Mollusca                            25.7         8.4
Bivalvia total                       3.0         0.8
Bivalvia, ni                         1.2         0.3
Anomidae
  Placuanomia cumingii               0.0         0.0
Arcidae
  Arcidae, ni                        0.6         0.2
  Anadara multicostata               0.0         0.0
  Barbatia reeveana                  0.0         0.0
Cardiidae
  Papyridea aspersa                  0.0         0.0
  Trigoniocardia biangulata          0.0         0.0
Carditidae
  Cardita affinis                    0.0         0.0
Crassatellidae
  Eucrassatella digueti              0.0         0.0
Glycymeridae
  Glycymeridae, ni                   1.2         0.3
  Glycymeris gigantea                0.0         0.0
  Glycymeris multicostata            0.0         0.0
Mytillidae
  Mytella guayanensis                0.0         0.0
Pectinidae
  Argopecten ventricosus             0.0         0.0
  Euvola vogdesi                     0.0         0.0
  Nodipecten subnodosus              0.0         0.0
Ostreidae
  Myrakeena angelica                 0.0         0.0
Psammobiidae
  Gari regularis                     0.0         0.0
Plicatulidae
  Plicatula spp.                     0.0         0.0
Veneridae
  Veneridae, ni                      0.0         0.0
  Chione californiensis              0.0         0.0
  Chione pulicaria                   0.0         0.0
  Chione lumens                      0.0         0.0
  Chione undatella                   0.0         0.0
  Dosinia ponderosa                  0.0         0.0
  Megapitaria auriantiaca            0.0         0.0
  Megapitaria squalida               0.0         0.0
  Pitar spp.                         0.0         0.0
  Protothaca grata                   0.0         0.0
  Ventricolaria spp.                 0.0         0.0
  Transennella puella                0.0         0.0
  Gastropoda total                  19.2         6.7
  Gastropoda, ni                    16.1         5.3
Bullidae
  Bulla spp.                         0.6         0.2
  Bulla punctulata                   0.0         0.0
Buccinidae
  Cantharus spp.                     0.6         0.2
  Cantharus elegans                  0.0         0.0
Cancellaridae
  Cancellaria spp.                   0.6         0.2
Calyptraeidae
  Crepidula spp.                     0.6         0.2
  Crepidula excavata                 0.0         0.0
  Crepidula onix                     0.0         0.0
  Crucibulum spinosum                0.0         0.0
Muricidae
  Murex recurvirostris               0.0         0.0
Naticidae
  Polinices bifasciatus              0.0         0.0
  Polinices recluzianus              0.0         0.0
Ollividae
  Ollivella spp.                     0.6         0.2
Strombidae
  Strombus granulatus                0.0         0.0
Trochidae
  Tegula spp.                        1.8         0.6
Turbinidae
  Turbofluctuosus                    0.0         0.0
Cephalopoda                          3.6         0.9
Octopodidae
  Octopus spp.                       3.6         0.9
Echiura
  Echiurus spp.                     26.8         8.8
  Sipuncula                          1.8         0.6
  Echinodermata                      5.4         1.4
  Acroechionoidea (irregularia)      0.0         0.0
  Echinoidea, ni                     2.4         0.6
Ophiodermatidae
  Ophioderma panamense               0.6         0.2
Ophiothricidae
  Ophiothrix spiculata               2.4         0.6
Ectoprocta
Onychocellidae
  Floridina antiqua                  0.6         0.2
Annelida
  Polychaeta, ni                     1.8         0.5
  Chordata                           5.4         1.5
Urochordata
  Ascidacea, ni                      0.6         0.2
Clavellinidae:
  Archidistoma pachecae              0.6         0.2
Teleostei
  Teleostei, ni                      3.6         0.9
  Huevos de Pez                      1.2         0.3
  Kyphosidae                         0.0         0.0
Labridae
  Halichoeres nicholsi               0.0         0.0
UOM                                 45.8         0.0
Total general                      187.4       100

                                         Midden

Item                                  FO         n

Arthropoda                           3.8        0.6
Crustacea, ni                        0.0        0.0
Ostracoda                            0.0        0.0
Decapoda (shrimp)                    0.0        0.0
Alpheidae                            0.0        0.0
Decapoda (crab)                      0.0        0.0
Diogenidae                           0.0        0.0
Lithodidae                           0.0        0.0
Brachyura, ni                        0.0        0.0
Portunidae
  Portunidae, ni                     0.0        0.0
  Portunus xantusii                  1.3        0.4
Leucosidae
  Speleophorus schmitti              1.3        0.2
  Xanthoidea                         0.0        0.0
Mollusca                            95.0       98.8
Bivalvia total                      95.0       91.1
Bivalvia, ni                         0.0        0.0
Anomidae
  Placuanomia cumingii               1.3        0.2
Arcidae
  Arcidae, ni                        0.0        0.0
  Anadara multicostata              25.0        6.8
  Barbatia reeveana                  1.3        0.2
Cardiidae
  Papyridea aspersa                 15.0        2.9
  Trigoniocardia biangulata         35.0        9.9
Carditidae
  Cardita affinis                    2.5        1.0
Crassatellidae
  Eucrassatella digueti              1.3        0.4
Glycymeridae
  Glycymeridae, ni                   0.0        0.0
  Glycymeris gigantea               28.8       10.5
  Glycymeris multicostata           22.5        8.7
Mytillidae
  Mytella guayanensis                6.3        1.0
Pectinidae
  Argopecten ventricosus             8.8        1.7
  Euvola vogdesi                    23.8        7.0
  Nodipecten subnodosus              2.5        0.6
Ostreidae
  Myrakeena angelica                 2.5        0.6
Psammobiidae
  Gari regularis                     7.5        1.4
Plicatulidae
  Plicatula spp.                     1.3        0.2
Veneridae
  Veneridae, ni                      2.5        0.6
  Chione californiensis             12.5        2.9
  Chione pulicaria                   1.3        0.2
  Chione lumens                      2.5        0.4
  Chione undatella                   6.3        1.0
  Dosinia ponderosa                 18.8        5.2
  Megapitaria auriantiaca            3.8        0.6
  Megapitaria squalida              48.8       21.3
  Pitar spp.                         1.3        0.2
  Protothaca grata                   6.3        2.9
  Ventricolaria spp.                 1.3        0.2
  Transennella puella                5.0        1.0
  Gastropoda total                  32.5        7.6
  Gastropoda, ni                     0.0        0.0
Bullidae
  Bulla spp.                         0.0        0.0
  Bulla punctulata                   2.5        0.4
Buccinidae
  Cantharus spp.                     0.0        0.0
  Cantharus elegans                  1.3        0.2
Cancellaridae
  Cancellaria spp.                   0.0        0.0
Calyptraeidae
  Crepidula spp.                     0.0        0.0
  Crepidula excavata                11.3        0.2
  Crepidula onix                     1.3        0.2
  Crucibulum spinosum               11.3        2.1
Muricidae
  Murex recurvirostris               1.3        0.2
Naticidae
  Polinices bifasciatus              3.8        0.6
  Polinices recluzianus              1.3        0.2
Ollividae
  Ollivella spp.                     0.0        0.0
Strombidae
  Strombus granulatus                2.5        0.4
Trochidae
  Tegula spp.                        0.0        0.0
Turbinidae
  Turbofluctuosus                   15.0        3.1
Cephalopoda                          0.0        0.0
Octopodidae
  Octopus spp.                       0.0        0.0
Echiura
  Echiurus spp.                      0.0        0.0
  Sipuncula                          0.0        0.0
  Echinodermata
  Acroechionoidea (irregularia)      1.3        0.2
  Echinoidea, ni                     1.3        0.2
Ophiodermatidae
  Ophioderma panamense               0.0        0.0
Ophiothricidae
  Ophiothrix spiculata               0.0        0.0
Ectoprocta
Onychocellidae
  Floridina antiqua                  0.0        0.0
Annelida
  Polychaeta, ni                     0.0        0.0
  Chordata                           1.3        0.2
Urochordata
  Ascidacea, ni                      0.0        0.0
Clavellinidae:
  Archidistoma pachecae              0.0        0.0
Teleostei
  Teleostei, ni                      0.0        0.0
  Huevos de Pez                      0.0        0.0
  Kyphosidae                         1.3        0.2
Labridae
  Halichoeres nicholsi               0.0        0.0
UOM                                  0.0        0.0
Total general                      350        100

                                       Live prey

Item                                  FO         n

Arthropoda                           0.0        0.0
Crustacea, ni                        0.0        0.0
Ostracoda                            0.0        0.0
Decapoda (shrimp)                    0.0        0.0
Alpheidae                            0.0        0.0
Decapoda (crab)                      0.0        0.0
Diogenidae                           0.0        0.0
Lithodidae                           0.0        0.0
Brachyura, ni                        0.0        0.0
Portunidae
  Portunidae, ni                     0.0        0.0
  Portunus xantusii                  0.0        0.0
Leucosidae
  Speleophorus schmitti              0.0        0.0
  Xanthoidea                         0.0        0.0
Mollusca                            66.7       77.8
Bivalvia total                      66.7       77.8
Bivalvia, ni                         0.0        0.0
Anomidae
  Placuanomia cumingii               0.0        0.0
Arcidae
  Arcidae, ni                        0.0        0.0
  Anadara multicostata               0.0        0.0
  Barbatia reeveana                  0.0        0.0
Cardiidae
  Papyridea aspersa                  0.0        0.0
  Trigoniocardia biangulata          0.0        0.0
Carditidae
  Cardita affinis                    0.0        0.0
Crassatellidae
  Eucrassatella digueti             11.1       11.1
Glycymeridae
  Glycymeridae, ni                   0.0        0.0
  Glycymeris gigantea                0.0        0.0
  Glycymeris multicostata            0.0        0.0
Mytillidae
  Mytella guayanensis                0.0        0.0
Pectinidae
  Argopecten ventricosus             0.0        0.0
  Euvola vogdesi                    11.1       11.1
  Nodipecten subnodosus              0.0        0.0
Ostreidae
  Myrakeena angelica                 0.0        0.0
Psammobiidae
  Gari regularis                     0.0        0.0
Plicatulidae
  Plicatula spp.                     0.0        0.0
Veneridae
  Veneridae, ni                      0.0        0.0
  Chione californiensis              0.0        0.0
  Chione pulicaria                   0.0        0.0
  Chione lumens                      0.0        0.0
  Chione undatella                   0.0        0.0
  Dosinia ponderosa                 22.2       22.2
  Megapitaria auriantiaca           11.1       11.1
  Megapitaria squalida              22.2       22.2
  Pitar spp.                         0.0        0.0
  Protothaca grata                   0.0        0.0
  Ventricolaria spp.                 0.0        0.0
  Transennella puella                0.0        0.0
  Gastropoda total                   0.0        0.0
  Gastropoda, ni                     0.0        0.0
Bullidae
  Bulla spp.                         0.0        0.0
  Bulla punctulata                   0.0        0.0
Buccinidae
  Cantharus spp.                     0.0        0.0
  Cantharus elegans                  0.0        0.0
Cancellaridae
  Cancellaria spp.                   0.0        0.0
Calyptraeidae
  Crepidula spp.                     0.0        0.0
  Crepidula excavata                 0.0        0.0
  Crepidula onix                     0.0        0.0
  Crucibulum spinosum                0.0        0.0
Muricidae
  Murex recurvirostris               0.0        0.0
Naticidae
  Polinices bifasciatus              0.0        0.0
  Polinices recluzianus              0.0        0.0
Ollividae
  Ollivella spp.                     0.0        0.0
Strombidae
  Strombus granulatus                0.0        0.0
Trochidae
  Tegula spp.                        0.0        0.0
Turbinidae
  Turbofluctuosus                    0.0        0.0
Cephalopoda                          0.0        0.0
Octopodidae
  Octopus spp.                       0.0        0.0
Echiura
  Echiurus spp.                     11.1       11.1
  Sipuncula                          0.0        0.0
  Echinodermata
  Acroechionoidea (irregularia)      0.0        0.0
  Echinoidea, ni                     0.0        0.0
Ophiodermatidae
  Ophioderma panamense               0.0        0.0
Ophiothricidae
  Ophiothrix spiculata               0.0        0.0
Ectoprocta
Onychocellidae
  Floridina antiqua                  0.0        0.0
Annelida
  Polychaeta, ni                     0.0        0.0
  Chordata                          11.1       11.1
Urochordata
  Ascidacea, ni                      0.0        0.0
Clavellinidae:
  Archidistoma pachecae              0.0        0.0
Teleostei
  Teleostei, ni                      0.0        0.0
  Huevos de Pez                      0.0        0.0
  Kyphosidae                         0.0        0.0
Labridae
  Halichoeres nicholsi              11.1       11.1
UOM                                  0.0        0.0
Total general                      100        100

Total values for larger groups are not indented in the left
column. FO, frequency of occurrence; ni, not identified;
UOM, unidentified organic matter.

TABLE 2.
Female, male, and combined fullness weight index by season.

                 Summer               Autumn

Female     0.30 [+ or -] 0.47   0.42 [+ or -] 0.53
Male       0.08 [+ or -] 0.07   0.25 [+ or -] 0.36
Combined   0.20 [+ or -] 0.36   0.32 [+ or -] 0.44

                 Winter               Spring

Female     0.28 [+ or -] 0.41   0.36 [+ or -] 0.40
Male       0.31 [+ or -] 0.35   0.41 [+ or -] 0.37
Combined   0.29 [+ or -] 0.37   0.39 [+ or -] 0.38

TABLE 3.
Female, male, and combined fullness weight index by gonad
development stage.

              Immature             Developing

Female   0.41 [+ or -] 0.52    0.25 [+ or -] 0.29

                              Immature/ Developing

Male                           0.42 [+ or -] 1.01

                Ripe            Spawning/Spent

Female   0.53 [+ or -] 0.45   0.02 [+ or -] 0.01

                Ripe               Spawning

Male     0.41 [+ or -] 0.64   0.30 [+ or -] 0.34

TABLE 4.
Frequency of occurrence (FO) and number of larger groups by
sex and by gonad development stage of Octopus bimaculatm
from Bahia de los Angeles, BC, Mexico.

                   Crabs (%)     Bivalves (%)  Gastropods (%)

                 n      FO       n      FO       n      FO

Female         40.9    39.1    40.4    28.7     7.7    28.7
  (n = 87)
Immature       35.4    36.6    45.3    36.6    11.0    43.9
  (n = 41)
Developing     42.5    23.1    50.6    46.2     3.4    23.1
  (n = 14)
Ripe           52.7    52.2    21.8     8.7     4.5     8.7
  (n = 23)
Spawning/      33.3    25.0    66.7    25.0     0.0     0.0
  spent
  (n = 4)
Male           53.0    47.9    32.5    40.8     4.9    22.4
  (n = 97)
Immature/      29.9    26.3    50.7    52.6     4.5    15.8
  developing
  (n = 18)
Ripe           61.1    59.6    26.4    36.2     4.9    23.4
  (n = 47)
Spawning       49.2    52.9    36.7    41.2     4.2    23.5
  (n = 17)

                 Echiura (%)    Other prey (%)

                 n      FO       n      FO

Female          6.7    24.1     4.2    16.1
  (n = 87)
Immature        6.6    24.4     1.7     7.3
  (n = 41)
Developing      1.1     7.1     2.3    15.4
  (n = 14)
Ripe           10.9    34.8    10.0    34.8
  (n = 23)
Spawning/       0.0     0.0     0.0     0.0
  spent
  (n = 4)
Male            4.6    23.5     4.9    21.4
  (n = 97)
Immature/       7.5    26.3     7.5    21.1
  developing
  (n = 18)
Ripe            4.1    23.4     3.5    19.1
  (n = 47)
Spawning        3.3    17.6     6.7    29.4
  (n = 17)
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Article Details
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Author:Villegas, Elisa Jeanneht Armendariz; Ceballos-Vazquez, Bertha Patricia; Markaida, Unai; Abitia-Carde
Publication:Journal of Shellfish Research
Article Type:Report
Geographic Code:1MEX
Date:Apr 1, 2014
Words:8172
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