Article

Habitat selection and shelter use by Octopus tetricus

April 1997
Marine Ecology Progress Series 150(1-3)

Authors:

The ecology of a shallow-water benthic octopus (Octopus tetncus) in northeastern New Zealand was examined. Spatial and temporaI patterns of abundance, habitat association, and shelter use were quantified. Octopus were abundant on the reef during summer, during which time females brooded eggs. Numbers declined rap~dly at the end of summer Octopus were not evenly distributed across sites, and were more abundant in patch reef habitats than in broken or flat reef habitats. The role of reefal factors in habitat selection, both abiotic and biotic, was examined using multiple regression and partial correlation analyses. Octopus were more abundant near the reef edge, and in areas wlth high numbers of small boulders. No relat~onsh~ps between octopi~s and potential reefal predators (eels) or reefal prey (crayfish) species were found. Soft-sediment bivalves occurred in the majority of shelter middens, suggesting that octopus were foraging over adjacent soft-scdiments rather than on the rocky reef itself. The degree of shelter modification varied with habitat, sex, and brooding status. Shelters were more likely to be modified in patch reef habitats than In broken and flat reef habitats. Brooding females were more likely to modify their shelters than non-brooding females and males, and often com-pletely barricaded shelter entrancvs. This study suggests that Octopus telricus are associated with rocky reef habitats during the breeding season, while a considerable portion of their life may be spent in soft-sediment habitats.

The ecology of Octopus aff. O. tetricus and prevalence of anisakid nematodes in near-coastal waters of North Fremantle, Western Australia

Thesis

Full-text available

Nov 2020

Jorja Claybrook

In contrast to most fished groups, global landings for cephalopod have been increasing over the last two decades. This and their fast-growth rate and short lifecycles, responsiveness to environmental change, and their function as mesopredators within the marine environment have led to an increased focus on their ecology. Within Western Australia, the common octopus, known currently as Octopus aff. O. tetricus is the target species of the commercial fishery which operates in Cockburn Sound. This Thesis focused on the population of O. tetricus inhabiting near-coastal waters of North Fremantle, ~7 km north of the current commercial operations and assessed any inter and intra-population variability between the two sites. Samples of octopus were collected by commercial fishers setting four lines of shelter pots, two in shallow (≤10 m) and two in deeper water (15-17 m) on seven occasions between March and June 2020 in North Fremantle. One sample of octopus was collected from Cockburn Sound on 1 st April. These data were used to examine if the distribution, abundance, and sex ratio differed across the sampling period and between depths. A total of 701 octopus were caught ranging in size from 35 to 218 mm mantle length (ML) and 5.13 to 691.62 g mantle weight. Over the duration of the study, the mean number of octopuses caught decreased. Males were more abundant in March and May, while females were more prevalent in April. The mean size of female octopus fluctuated in the first four hauls the trap lines and then declined from late-April to June, indicating a possible migration out of the area by larger females. Females caught in Cockburn Sound over a wider range of habitats were larger than those from North Fremantle at the same time. The mean size of male octopus increased gradually over the duration of the study with the highest mean ML recorded in June. Male octopus matured during the study with the number of immature males decreasing from March to June, in both depth regions. Initially, this Thesis aimed to include a detailed analysis of the dietary composition of Octopus aff. O. tetricus, however due to time constraints only a preliminary analysis is presented in this dissertation. The contents of the gastric tract (crop and stomach) of 701 octopus were examined. A total of 12 taxa were identified in the gastric contents, with crustaceans identified as the most common prey, followed by teleosts and non-cephalopod molluscs. Cannibalism was observed in 51 octopus (10.8% of gastric contents with dietary items). 4 During the dissection of octopus mantles, parasites, tentatively identified as anisakid nematodes, were recorded on the internal organs and this became an additional focus of the research. The incidence of parasites was nearly 60% in North Fremantle and when present, always occurred in the gastric tract but were also found in the mantle muscles, digestive gland, posterior salivary glands and gonads. Binomial logistic models with a logit link function showed that the probability of parasite incidence was nearly ten times higher in the North Fremantle population compared with Cockburn Sound. The probability of parasite occurrence was also significantly greater on medium (80-160 mm ML) and large octopus (>160 mm ML) than small octopus. The resultsfrom thisstudy show that the nearshore waters of North Fremantle are likely a nursery habitat for juvenile and maturing male octopus’ but females probably migrate to deeper waters to mate and brood their eggs. The prevalence of parasites and location suggests that nematodes are being ingested within North Fremantle at a much higher rate than in Cockburn Sound.

Biomass estimates and harvest strategies for the Western Australian Octopus aff. tetricus fishery

Article

Full-text available

Dec 2019

Octopus aff. tetricus is the target of Australia’s most significant octopus fishery. We utilized both fishery-independent surveys and fishery data from spatially detailed catch and effort logbooks to examine distribution and abundance across the spatial and depth ranges of the population. From this, a harvest strategy was developed to form the basis for monitoring, assessment, and management. Octopus aff. tetricus is abundant and widely distributed in Western Australia, with a biomass density range of 150–1000 kg km−2. This is comparable to Octopus vulgaris fisheries in the Mediterranean and sub-Saharan Africa. From an estimated habitat area of 20 073 km2, total biomass on the West Coast was estimated to be a minimum of 3600 tonnes whole weight with 90% certainty. At the current annual catch of 300 tonnes, overall population exploitation rate is low, given the high natural productivity of the species, which has a maximum age of 1.5 years and two recruitment pulses per year. A formal species name for O. aff. tetricus is required so its contribution to the Australian cephalopod fisheries harvest can be officially recognized.

Octopus as predators of Haliotis laevigata on an abalone sea ranch of south-western Australia

Thesis

Feb 2018

See peer-reviewed articles "Octopus as predators of abalone on a sea ranch" - https://www.researchgate.net/publication/330280503_Octopus_as_predators_of_abalone_on_a_sea_ranch https://doi.org/10.1111/fme.12328... "Diet and trophic role of octopus on an abalone sea ranch" https://www.researchgate.net/publication/335235492_Diet_and_trophic_role_of_octopus_on_an_abalone_sea_ranch... Octopuses play key ecological roles within coastal marine environments around the world. Their short-lived, rapid-growing lifecycle commands high feeding rates, which has the potential to impose strong top-down controls on the benthic communities where they are found. This Thesis investigated two major questions on the predatory role of octopuses on an abalone sea ranch in south-western Australia: (i) does the distribution of octopus on the sea ranch affect the mortality of Greenlip Abalone, Haliotis laevigata (Chapter 2), and (ii) what is the diet and nutrient assimilation (δ13C and δ15N) of Octopus cf. tetricus in this ecosystem (Chapter 3). Data were collected by commercial divers over a 27-month period on octopus abundance and the number of empty abalone shells at ~fortnightly to monthly intervals, and the number of abalone surviving on artificial abalone habitats (“Abitats”) every six months. These data were used to examine whether the number of empty shells, and the counts of surviving abalone were related to the presence of octopus. Negative binomial generalised linear models showed that the presence of octopus had a significant impact on the number of empty abalone shells collected and estimated that the shell counts are 78% higher when O. cf. tetricus is present when adjusting for location (“Line”) and Season. The Abitats provide an ideal habitat for octopuses, offering shelter and an abundant food supply. The relationship between octopus and shell counts was also influenced by the spatial position of the Abitats (Line) and Season, which may be linked to environmental variability and the time at which abalone are seeded. The results from time series (AR1) models for the relationship between octopus presence and abalone survival were not significant, contradicting those from the negative binomial models. This result is likely an artefact of the random sampling design for counting abalone to estimate survival and uncertainty in the number of abalone seeded onto each Abitat. A subsample of 110 shells collected by the divers was examined for evidence of octopus predation. Twenty shells (18%) had a small, slightly ovoid hole with a bevelled edge, consistent with the holes made by octopuses. These results confirm that octopuses are a major source of mortality on the sea ranch, supporting the results of the negative binomial models. Gastric tract and stable isotope analyses were undertaken to determine the dietary composition of different sizes of O. cf. tetricus, and its significance as a predator of H. laevigata on the abalone sea ranch. The crops and stomachs of 44 individuals were examined to assess whether diet differed between these digestive organs, or with increasing body size (< 300 g, 300 to 999 g, ≥ 1,000 g). A much higher proportion of material could be identified in the crops (%Volume, %V = 96%) than in the stomachs (26%). Molluscs contributed the largest %V in the crops (~31%) followed by crustaceans (33%), with unidentified material only contributing ~4%. In contrast, 74% of stomach contents were not identifiable, with molluscs comprising the majority of identifiable material (~19%), followed by crustaceans (~6%). The dietary composition of O. cf. tetricus did not change with increased body size (from 58.5 to 1596.1 g), paralleling the findings of stable isotope analysis. However, only four octopus > 1,000 g were available for analysis. The nitrogen (δ15N) and carbon (δ13C) isotope signatures of octopus, fish, abalone, and benthic primary producers were examined to understand the assimilation of nitrogen and carbon by O. cf. tetricus, and the trophic position of this species within the Flinders Bay sea ranch food web. Examination of δ15N values revealed that O. cf. tetricus (8.08 ± 0.19) occupies a mid-trophic level, slightly below teleosts (10.10 ± 0.22) and loliginid squids (9.47 ± 0.27). The δ13C signature of O. cf. tetricus (-23.63 ± 0.42) was similar to three benthic teleosts, Coris auricularis and Opthalmolepis lineolatus, and Upeneichthys vlamingii, highlighting the overlap in use of benthic food resources by several consumers in this system. While gastric tract analyses suggest that O. cf. tetricus is an important predator of H. laevigata, stable isotope analyses show a less obvious trend. This is indicated by the enrichment of δ13C by ~4‰ between abalone and octopus. The results from this Thesis provide information on the predatory role of O. cf. tetricus, their significance as predators of H. laevigata, and their trophic positioning within this coastal marine system.

Octopus insularis (Cephalopoda: Octopodidae) on the tropical coast of Brazil: Where it lives and what it eats

Article

Full-text available

Dec 2016

Octopus insularis is the dominant octopus in the shallow tropical waters of the coast and oceanic islands in the North and Northeast of Brazil. Is the abundance, distribution, habitat and diet of this species on the continent the same as in oceanic islands? These factors were evaluated in seeking these answers at two areas of occurrence of Octopus insularis on the coast of Rio Grande do Norte, Brazil. Three main types of habitats were described where the species is concentrated, being: Deep Reefs (Reefs of Risca) (> 15 m), Flat Biogenic Plateaus (Restingas) (5-15 m) and Shallow Sedimentary Reefs (Pirangi reefs) (< 5 m). An aggregate spatial distribution was verified, along with bathymetric segregation in which small individuals occupied shallow areas. Regarding diet, O. insularis consumed mainly crustaceans (68%) in shallow reef areas, bivalves (86%) in biogenic plateau areas, and gastropods (33%) in deep reef areas. The characterization of new occurring habitats, such as the area of biogenic plateau, and changes in their diet due to habitat function have shown that O. insularis occupies a broader niche than has been described in literature to date, expanding our knowledge on the ecology and biology of this octopus species of economic interest.

The behavioral ecology and locomotion of Abdopus aculeatus (d’Orbigny 1834)

Thesis

Full-text available

Dec 2005

Christine L Huffard

An illustrated ethogram describes the behavioral ecology and skin components of Abdopus aculeatus studied on Sulawesi, Indonesia and Queensland, Australia. These octopuses aggregated on intertidal reef flats and foraged for crustaceans during diurnal mid and low tides. Mating by A. aculeatus in the wild involved frequent copulation and alternate mating strategies. Most mating took place in mate guarding situations rather than during transient interactions. Large males followed and mated with females throughout the day and mate-guarded by chasing away smaller males that approached the female. The largest guarding males paired by occupying a den within arm’s reach of a female. These ‘paired’ male and female octopuses were more likely than unpaired individuals to spend time copulating throughout the day. Sneaker males were rare but demonstrated longer individual mating bouts than males employing other strategies. Male-male and male-female agonistic interactions were observed in the wild. Arm-wrestling was most common between unpaired males, as well as males closely matched in size. Contest escalation was not observed. While male-male agonistic interactions were more common and involved more physical contact than male-female interactions, equivalent degrees of arm injuries were measured in both sexes indicating that most arm injuries observed did not result from aggression. Variation in behavior, density and local sex ratio of Abdopus aculeatus were studied in five 200m2 plots. Principal Components Analysis and Kendal’s Partial Rank Correlation Coefficients were used to examine possible associations between mating behavior, rates of aggression, displaying behavior, sex ratio and density. As the male-bias of sex ratio within plots increased, unpaired males lengthened the duration of copulation, while paired males increased rates of aggression. It is possible that male A. aculeatus might detect local levels of mate competition and adjust their behavior accordingly. Speeds and body patterns during crawling, swimming, jetting, and walking Abdopus aculeatus were compared and interpreted in a behavioral context. Jetting and swimming was faster than crawling, while walking proceeded approximately as fast as swimming. Octopuses swam faster when dorso-ventrally compressed than when swimming with the head raised. Based on these findings, I re-evaluate behaviors like “flatfish mimicry”, polyphenism, and the Blanch-Ink-Jet maneuvers.

Female Mating Preference Polyandry and Paternity Bias in Octopus tetricus

Thesis

Full-text available

Jun 2008

Peter Morse

Honours Research Thesis (2008) - Abstract: In polyandrous mating systems where females do not receive any direct benefit from successive matings and they are not being forced into subsequent copulations by the males, genetic benefits may be the driving mechanism for the evolution of promiscuous behaviour. This has been shown in mating systems of some birds, mammals, fish, and insects. In these systems females often combine strategies of pre-copulatory mate choice (choosing to mate with certain types of males) and post-copulatory mechanisms (cryptic female choice and/or sperm competition) to genetically enhance the fitness of their offspring. This study investigates whether some of these mechanisms for females to benefit from polyandrous mating can be applied to a virtually unstudied mating system of the octopus, by examining mating preferences and paternity patterns in a common Western Australian species, the gloomy octopus (Octopus tetricus). Laboratory mating trials revealed that female O. tetricus display a strong pre-copulatory mating preference for males that have longer mating appendages (ligulae), and in successive matings have a tendency to trade-up for males with successively larger ligulae. Microsatellite analyses showed that all sampled females sired their broods to multiple males and that relative paternity in this species was greatly influenced by the duration of time that the female spent mating with each candidate father. However, this pattern overwhelmed the ability of this study detect any other forms of consistent paternity bias e.g. towards males with longer ligulae or last-male bias. It was also found that O. tetricus have the capacity to regulate their polarised skin patterns, but there was no evidence that this was related to mating or mate choice. Several mechanisms were discussed that might explain the evolution of polyandry in this species: female trade-up behaviour, ensuring genomic compatibility, increasing offspring genetic diversity, and increasing sperm supply for a larger brood. Distinguishing between these potential mechanisms might be achieved with future paternity testing across more samples, and comparing offspring abundance and viability between promiscuous and non-promiscuous females.

Spawning habitat selection by Octopus vulgaris: New insights for a more effective management of this resource

Article

May 2015
FISH RES

The selection of spawning habitat of a population of Octopus vulgaris that is subject to a small-scale exploitation was studied in the Cíes Islands within the National Park of the Atlantic Islands of Galicia (NW Spain). The technique used was visual censuses by scuba diving. We conducted 93 visual censuses from April 2012 to April 2014. The total swept area was 123.69 ha. Habitat features (season, depth, zone, bottom temperature, swept area, bottom substrate type, and creels fishing impact) were evaluated as predictors of the presence/absence of spawning dens using GAM models. O. vulgaris has a noteworthy preference for spawning in areas with hard bottom substrate and moderate depth (approximately 20 m). The higher density of spawning dens (1.08 ha−1) was found in a surveyed area of 50.14 ha located in the northeastern part of the northern Cíes Island. We propose to protect the area comprised from Punta Escodelo to Punta Ferreiro between 5 and 30 m depth. This area has a surface of 158 ha equivalent to 5.98% of the total marine area of the Cíes islands. The strengths and weaknesses of a management strategy based on the protection of the species’ spawning habitat are discussed.

Spawning habitat selection by Octopus vulgaris: New insights for a more effective management of this resource

Article

May 2015
FISH RES

The selection of spawning habitat of a population of Octopus vulgaris that is subject to a small scale exploitation was studied in the Cíes Islands within the National Park of the Atlantic Islands of Galicia (NW Spain). The technique used was visual censuses by scuba diving. We conducted 93 visual censuses from April 2012 to April 2014. The total swept area was 123.69 ha. Habitat features (season, depth, zone, bottom temperature, swept area, bottom substrate type, and creels fishing impact) were evaluated as predictors of the presence/absence of spawning dens using GAM models. O. vulgaris has a noteworthy preference for spawning in areas with hard bottom substrate and moderate depth (approximately 20 meters). The higher density of spawning dens (1.08/ha) was found in a surveyed area of 50.14 ha located in the northeastern part of the northern Cíes Island. We propose to protect the area comprised from Punta Escodelo to Punta Ferreiro between 5 and 30 m depth. This area has a surface of 158 ha equivalent to 5.98 % of the total marine area of the Cíes islands. The strengths and weaknesses of a management strategy based on the protection of the species’ spawning habitat are discussed.

Temperature induced changes in the development of embryos and paralarvae of the merobenthic octopus, Octopus tetricus

Article

Feb 2021
AQUACULTURE

Incubation temperatures can extend or decrease the time required for the embryos of marine invertebrates to hatch, while also greatly influencing the morphology and survival of hatchlings, characteristics which are of critical importance in hatchery production. This study examines the effect of incubation temperatures (16, 19, 22, 25 °C and ambient seawater temperature) on the development time to hatch, egg morphometric ontogeny and the hatching success in the common Sydney octopus, Octopus tetricus. These parameters were assessed at regular intervals for eggs from three broods placed in artificial incubation tanks at four temperatures between 16 and 25 °C, while the remainder of the eggs for each of the broods were incubated in ambient seawater under female care. The time to hatch had an inverse relationship to incubation temperature with the egg development time to hatch being halved at 25 °C (26–32 days) compared to 16 °C (67–69 days). Despite the markedly different development times there were no differences in the survival or quality of the resulting hatched paralarvae, although there was an overall tendency for inner yolk sac volume to decrease with increasing rearing temperature but not consistently among broods. There were differences in the number, size and quality of embryos in the three broods which tended to persist throughout their development, but these did not appear to be related to the size of the female octopus or water temperature prior to egg laying. The overall hatching success of eggs in artificial incubation tanks was above 90% for the brood of one female (F1) while for the other two it was 71% (F3) and 57% (F2) mostly likely as a direct result of being compromised by infection of the egg strings. Improvements in hatchery practice is required to prevent such infections for future paralarval production. The results demonstrate a wide thermal tolerance for the early developmental stages of O. tetricus with the potential to manipulate egg incubation temperatures to better meet the timing of hatchery production requirements.

Predictable spatiotemporal dynamics of a dense cuttlefish spawning aggregation increases its vulnerability to exploitation

Article

Jan 2018

The giant Australian cuttlefish, Sepia apama, forms a dense spawning aggregation at a single known location across its wide southern Australian distribution. After a rapid increase in fishing pressure on the aggregation in the late 1990s, a series of fishing closures were introduced before any biological information could be collected. We surveyed the habitats, timing, and spatial distribution of the spawning aggregation over 4 years, using underwater visual transects and passive tagging, to assess the suitability of the closures. We found that the annual aggregation was both temporally (April-August) and spatially (over 8 km of coastline) localized and predictable, with a consistent peak in abundances in late May-early June. Cuttlefish densities were generally highest over the shallow, broken bedrock habitat, which was more extensive in several sites left open to fishing. Although the original closure covered about 43% of the hard substrate, it accounted for only 23-37% of the total cuttlefish abundance. The extremely high densities recorded during this study verified that this is a massive spawning aggregation for cuttlefish species worldwide, and that it could be highly vulnerable to overexploitation in the absence of adequate protection, because it is so spatiotemporally predictable and localized. © International Council for the Exploration of the Sea 2017. All rights reserved.

Allopatric Speciation within a Cryptic Species Complex of Australasian Octopuses

Article

Full-text available

Jun 2014
PLOS ONE

Despite extensive revisions over recent decades, the taxonomy of benthic octopuses (Family Octopodidae) remains in a considerable flux. Among groups of unresolved status is a species complex of morphologically similar shallow-water octopods from subtropical Australasia, including: Allopatric populations of Octopus tetricus on the eastern and western coasts of Australia, of which the Western Australian form is speculated to be a distinct or sub-species; and Octopus gibbsi from New Zealand, a proposed synonym of Australian forms. This study employed a combination of molecular and morphological techniques to resolve the taxonomic status of the 'tetricus complex'. Phylogenetic analyses (based on five mitochondrial genes: 12S rRNA, 16S rRNA, COI, COIII and Cytb) and Generalised Mixed Yule Coalescent (GMYC) analysis (based on COI, COIII and Cytb) distinguished eastern and Western Australian O. tetricus as distinct species, while O. gibbsi was found to be synonymous with the east Australian form (BS = >97, PP = 1; GMYC p = 0.01). Discrete morphological differences in mature male octopuses (based on sixteen morphological traits) provided further evidence of cryptic speciation between east (including New Zealand) and west coast populations; although females proved less useful in morphological distinction among members of the tetricus complex. In addition, phylogenetic analyses suggested populations of octopuses currently treated under the name Octopus vulgaris are paraphyletic; providing evidence of cryptic speciation among global populations of O. vulgaris, the most commercially valuable octopus species worldwide.

Field observations of mating in Octopus tetricus Gould, 1852 and Amphioctopus marginatus (Taki, 1964) (Cephalopoda: Octopodidae)

Article

Full-text available

Jan 2010
MOLLUSCAN RES

We present observations of mating by Octopus tetricus Gould, 1852 and Amphioctopus marginatus (Taki, 1964) in the wild. Males of both species mated in the open using the 'reach' position, however one male O. tetricus also incorporated the 'mount' position when copulating with a smaller female. A small male Octopus tetricus copulated by stretching the hectocotylus (= mating arm) over rugged terrain, to a larger female. Direct evidence confirms the existence of inter-sexual aggression during mating in this species. We observed a male A. marginatus mate at close proximity to the smaller female, with minimal stretching of the hectocotylus, and with no evidence of aggression. © 2010 Malacological Society of Australasia & Society for the Study of Molluscan Diversity.

Transitions During Cephalopod Life History: The Role of Habitat, Environment, Functional Morphology and Behaviour

Article

Full-text available

Jun 2014
ADV MAR BIOL

Cephalopod life cycles generally share a set of stages that take place in different habitats and are adapted to specific, though variable, environmental conditions. Throughout the lifespan, individuals undertake a series of brief transitions from one stage to the next. Four transitions were identified: fertilisation of eggs to their release from the female (1), from eggs to paralarvae (2), from paralarvae to subadults (3) and from subadults to adults (4). An analysis of each transition identified that the changes can be radical (i.e. involving a range of morphological, physiological and behavioural phenomena and shifts in habitats) and critical (i.e. depending on environmental conditions essential for cohort survival). This analysis underlines that transitions from eggs to paralarvae (2) and from paralarvae to subadults (3) present major risk of mortality, while changes in the other transitions can have evolutionary significance. This synthesis suggests that more accurate evaluation of the sensitivity of cephalopod populations to environmental variation could be achieved by taking into account the ontogeny of the organisms. The comparison of most described species advocates for studies linking development and ecology in this particular group.

Assessing the Attractive Effects of Floating Artificial Reefs and Combination Reefs on Six Local Marine Species

Article

Full-text available

May 2023

Artificial reefs (ARs) have been advocated for and implemented as management tools for recreational fisheries, species conservation, and habitat replacement; however, the research that includes attracting marine species of floating ARs remains in its early stages. Here, two types of floating ARs were designed to evaluate the attractive effects using the occurrence rate and attracting index for six commercially important species (Lateolabrax maculatus, Liza haematocheila, Sebastes schlegelii, Acanthopagrus schlegelii, Litopenaeus vannamei, and Amphioctopus fangsiao) in the Bohai Bay of China; their combined ARs were meanwhile compared with two variants of artificial seagrass beds (SA and SB) and the traditional double-frame artificial reef (TD). All of the designed ARs were effective in attracting experimental species. The ARs with higher shelter areas (SB and TD) showed a better attracting effect. The efficiency of the ARs in attracting different species depended on their life histories. The bottom-mounted ARs were more efficient in attracting demersal species, while the floating ARs attracted epipelagic fish. In addition, the combined reefs had a better attractive effect than single ARs did. Overall, floating ARs and their combined ARs show the potential to deploy especially for attracting epipelagic fishes, although further study is needed.

Tetrodotoxin and the Geographic Distribution of the Blue-Lined Octopus Hapalochlaena fasciata on the Korean Coast

Article

Full-text available

Apr 2023

The genus Hapalochlaena, including the blue-lined octopus Hapalochlaena fasciata (H. fasciata), is highly toxic. Venomous, blue-lined octopuses were recently found in Korea, but their toxicity, toxin composition, and distribution remain largely unknown. Here we estimated the geographic distribution of the organisms along the Korean coast and clarified their toxicity. Tetrodotoxin (TTX) was present in all three specimens of H. fasciata examined, although the toxicity varied largely between individuals. The mean TTX concentration in the whole body of the three specimens was 6.5 ± 2.2 μg/g (range 3.3–8.5 μg/g). Among the body parts examined, the salivary glands exhibited the highest concentration (22.4 ± 9.7 μg/g). From 2012 to 2021, 26 individuals were obtained nearly every month from different regions of the Korean coast. A non-fatal case of a blue-lined octopus bite was reported along the Korean coast in June 2015. This is the first report on the widespread distribution of blue-lined octopuses on the Korean coast and TTX detection. The widespread distribution of the TTX-bearing H. fasciata along the Korean coast within the temperate zone indicates that the species may soon become a serious health issue in Korea. The toxicity of this species is also a potentially significant human health risk.

The Case for Octopus Consciousness: Valence

Article

Full-text available

Nov 2022

Jennifer A. Mather

Octopuses may demonstrate perceptual richness, neural unity, temporality, and finally, valence or affective evaluation, as the neural basis for consciousness. Octopuses attach a positive valence to food as ‘specializing generalists’ with long-term learning and flexible choices. They value shelter, yet modify, adapt and even transport it where necessary. They attach a negative valence to what may be described as pain, monitoring and protecting the damaged area and learning to associate locations with pain relief. Finally and surprisingly, octopuses attach a negative value to uncertainty so that they explore their environment before exploiting certain aspects of it and even exhibit motor play. This series of four papers, culminating in the present one, demonstrates in detail why the Cambridge Declaration of Consciousness has suggested octopuses might have the substrate for consciousness, although it is likely not similar to or as complex as that shown by ‘higher’ vertebrate lineages.

The Colours of Octopus: Using Spectral Data to Measure Octopus Camouflage

Article

Full-text available

Sep 2022

No animal can so effectively camouflage in such a wide range of environments as the octopus. Thanks to their highly malleable skin, they are capable of adapting their body patterns to the brightness and texture of their immediate environment, and they often seemingly match the colour of background objects. However, octopuses are colour-blind as their eyes have only one type of visual pigment. Therefore, chromatophores in their skin are likely to respond to changes in brightness, not chromaticity. To determine whether octopuses actually match background colours, we used a SpectraScan® PR-655 spectroradiometer to measure the reflectance spectra of Octopus tetricus skin in captivity. The spectra were compared with those of green algae, brown algae, and sponges—all of these being colourful objects commonly found in the octopus’s natural environment. Even though we show that octopuses change both lightness and chromaticity, allowing them to potentially camouflage in a wide range of backgrounds in an effective manner, the overall octopus colours did not reach the same level of saturation compared to some background objects. Spectra were then modelled under the visual systems of four potential octopus predators: one dichromatic fish (Heller’s barracuda), two trichromatic fish (blue-spotted stingray and two-spotted red snapper), and one tetrachromatic bird (wedge-tailed shearwater). We show that octopuses are able to match certain background colours for some visual systems. How a colour-blind animal is capable of colour-matching is still unknown.

Shelters for aquaculture of Octopus sinensis: preferences for gap width and horizontal versus vertical plates

Article

Full-text available

Jan 2022

It is difficult to keep a large number of cultured octopuses together in the same holding tank due to the high incidence of cannibalism. Appropriate shelters within which the octopuses can more readily avoid their peers are expected to ameliorate this problem. Shelters can be constructed from square plates assembled with appropriate spacing (gap) between them. The purpose of this study was to ascertain the optimum plate orientation and gap width between plates for shelters to maximize the accommodation of octopuses. It was found that the number of shelter occupants increased with the number of gaps available, such that more than half of the individuals in the experimental tank used the same shelter simultaneously. Octopuses tested singly to determine preferences for shelters placed vertically or horizontally preferred the vertical arrangement. Octopuses of more than 300 g tested singly in aquaria given shelters with different gap widths (20–100 mm) were found to not enter shelters with gap widths of 20 or 40 mm. It is concluded that octopus shelters constructed from square vertical plates spaced with gap widths suitable for octopuses are a useful contribution towards maximizing the number of octopuses that can be maintained in culture conditions.

Shelter preference and utilisation behaviour of small benthic octopus Amphioctopus fangsiao d'Orbigny for brooding under laboratory conditions

Article

Full-text available

Oct 2021

For benthic octopuses, shelter utilisation is a common behaviour to defend their vulnerable soft bodies against predators. Furthermore, most species of octopus exhibit egg-care behaviour, and the brooding females often attach their egg masses on the inside of the shelters to defend their eggs securely. The type of shelter is therefore a matter of concern for brooding females, affecting their reproductive success. This study aimed to investigate the shelter preference and utilisation behaviour of the small benthic octopus Amphioctopus fangsiao. Five types of shelters, including empty shells of bivalve Saxidomus purpurata and gastropod Rapana venosa, and different-sized artificial pottery pots, were introduced into the aquaria where eight female octopuses were individually reared. The types of shelters utilised by the females were recorded twice a day until they started spawning (observation period, 12-28 days). Six females with a body weight (BW) ranging from 68 to 125 g utilised the gastropod shells most frequently, and four females attached their eggs to the inside of the shells. Characteristic shell-wearing behaviour like that of live gastropods was observed for these females. Meanwhile, large two females with 135 and 182 g BW selected the largest artificial pot for spawning, suggesting a body size-dependent shelter preference.

An experimental assessment of social tolerance and den ecology in a high-density octopus population

Article

Full-text available

May 2021
MAR BIOL

Long held notions of the universally asocial octopus are being challenged due to the identification of high-density and interacting octopus populations in Australia, Indonesia, Japan and the deep sea. This study experimentally assessed the social tolerance and presence of potential prey items of Caribbean reef octopus , Octopus briareus, in a tropical marine lake (25°21′40″N, 76°30′40″W) on the island of Eleuthera, The Bahamas, by deploying artificial dens in multi-den groups or ‘units’ in the months of May and June 2019. Fifteen octopus were observed occupying dens ( n = 100), resulting in 13 den units being occupied ( n = 40). Two examples of adjacent occupation within a single den unit were identified but with zero examples of cohabitation/den sharing. Ecological models showed den and den unit occupation was predicted to increase with depth and differ between sites. Octopus also displayed no preference for isolated or communal units but preferred isolated dens over dens adjacent to others. Additionally, 47 % of occupied dens contained bivalve or crustacean items with no epifauna on their interior surface. The lack of epifauna suggests that these items have been recently ‘cleaned’ by occupying octopus and so represent likely prey. This study presents evidence of possible antisocial den use by O. briareus , a modification of the default ‘asocial’ ignoring of conspecifics typically attributed to octopus. This is likely in response to the high population density and may imply behavioural plasticity, making this system appropriate for further scrutiny as a research location on the influence of large, insular environments on marine species.

What is in an octopus's mind?

Article

Jan 2019

Jennifer A. Mather

Growth and age of the midget octopus, Octopus huttoni

Article

Full-text available

Dec 2019
AQUAT ECOL

The midget octopus Octopus huttoni is an important link between trophic levels as a food source and a predator, but little is known about its life history or growth. This is the first study to age and quantify growth in O. huttoni from three populations in Southern New Zealand, namely Foveaux Strait, Otago Harbour, and the Otago continental shelf. Morphometries were measured for 121 individuals, ages were estimated for 109 individuals using beak and stylet increment analysis, and lipofuscin quantity was analysed for 106 individuals. Assuming that one increment equals 1 day, beaks provided the highest age estimate (up to 250 days), but are suspected to be an underestimate (40–70 days) because increments were not found on laboratory-reared paralarval beaks, suggesting that the first increment may form after settlement. Daily growth rings in stylets were validated by tetracycline marking, but low estimates of age were attributed to poor visualisation of the stylet nucleus. The relationships between lipofuscin volume ratio and age or size of the individual were not significant, lipofuscin density was low, and individual variation was high. Results indicated that this species displays indeterminate growth until death, with a maximum mantle length of 50–60 mm at an age of 200–250 days. Further, individuals from Foveaux Strait were smaller and younger than those found in the Otago Harbour, supporting an hypothesis of an ontogenetic migration onshore.

Diet and trophic role of octopus on an abalone sea ranch

Article

Full-text available

Aug 2019

Gastric tract (crop and stomach) and stable isotope analyses (SIA) were used to evaluate the dietary composition of resident, commercially important Octopus aff. O. tetricus Gould, and its importance as a predator of Haliotis laevigata Donovan, on artificial abalone habitats. Taxonomic diversity and resolution of diet were higher in crops (13 taxa) than stomachs (10 taxa), with the latter dominated by unidentifiable material (%Volume = 74%). Crops contained mainly molluscs (~54%, including 31% abalone) and crustaceans (33%), suggesting octopus are important predators of abalone on the sea ranch. Dietary composition of crops did not differ with increasing octopus weight (<300 g, 300–999 g, ≥1,000 g wet weight), paralleling the findings of SIA and reflecting the high stocking densities of abalone that are able to be consumed by octopus of all sizes. The SIA also revealed that octopus occupy a mid‐trophic level, slightly below teleosts and loliginid squids.

Growth of juvenile common octopus (Octopus vulgaris) in Korean waters is affected by shelter type

Article

May 2019
AQUACULT ENG

Octopus as predators of abalone on a sea ranch

Article

Full-text available

Jan 2019
FISHERIES MANAG ECOL

This study examined the occurrence of octopus across an abalone, Haliotis laevigata, Donovan, sea ranch in south‐western Australia, to understand how octopus may be impacting abalone production. Commercial divers removed 654 octopus and 17,666 empty abalone shells during regular, 2 to 4‐weekly surveys over 27 months. A negative binomial generalised linear model estimated a 78% increase in empty shells per artificial abalone habitat per day, when octopuses were present, after adjusting for location and season. Of the 408 shells examined for evidence of predation, 19% had a small, slightly ovoid hole consistent with those made by octopus. The mean (± 1 SE) length of shells with boreholes (70.3 ± 2.2 mm) was significantly longer than those without (59.8 ± 0.5 mm), and boreholes were concentrated over the adductor, respiratory organs and heart. This study provides important insights into the adaptable feeding regimes of octopus and their potential to impose strong top‐down controls on sea ranching operations.

Biological and fisheries aspect of Octopus sp. (Cephalopoda) from the waters of buton regency, southeast Sulawesi, Indonesia

Article

Full-text available

Feb 2018

Mugi Mulyono

An octopus fishery in Buton waters is expected to continue to decrease its catch. To know the condition of octopus fishery need to do research to get information of biology and fishery aspect as management effort. The aim of this research is related to fishery in Buton regency waters. Case study method was used in this research, by choosing Buton regency waters as the research area. This research was carried out in January until May 2016. Observation had been done in order to get the biological data of Octopus sp. and fisheries aspect had been used by Purposive Sampling methods. The result of the research of 402 samples Octopus sp. shows the pattern of allometric negative growth that grow rapidly from heavy growth Octopus sp. the value of a (intercept) = equal to 1,979812, b (slope) = equal to 2,5722 and r (coefficient of correlation) = equal to 0.867888 then the equation of length and weight becomes W = 1,979812 L 2,5722. This shows that the b value obtained is smaller than 3 (three), which means that the octopus (Octopus sp.) has a negative allometric growth pattern, due to the increase in octopus length faster than growth weight. Judging from the above calculation, the correlation value (r) is 0.867888 which is almost close to 1 (one) indicates the presence of a close enough and positive relationship between weight gain and octopus length.

A second site occupied by Octopus tetricus at high densities, with notes on their ecology and behavior

Article

Full-text available

Sep 2017
MAR FRESHW BEHAV PHY

We report wild octopuses (Octopus tetricus) living at high density at a rock outcrop, the second such site known. O. tetricus are often observed as solitary individuals, with the species known to exist at similar densities and exhibiting complex social behaviors at only one site other than that described here. The present site was occupied by 10–15 octopuses on eight different days. We recorded frequent interactions, signaling, mating, mate defense, eviction of octopuses from dens, and attempts to exclude individuals from the site. These observations demonstrate that high-density occupation and complex social behaviors are not unique to the earlier described site, which had been affected to some extent by remains of human activity. Behavior at this second site confirms that complex social interactions also occur in association with natural substrate, and suggest that social interactions are more wide spread among octopuses than previously recognized.

Innovative development of the Octopus (cf) tetricus fishery in Western Australia .

Technical Report

Full-text available

Jan 2016

Estudio biológico -pesquero de Octopus spp. en el Complejo Lagunar Bahía Magdalena-Almejas, B.C.S., México

Research

Full-text available

Feb 2016

Ariadna Malinalli Sánchez-García

En el complejo lagunar Bahía Magdalena-Bahía-Almejas (BM-BA), B.C.S. actualmente se lleva a cabo una pesquería del recurso pulpo, sin ninguna limitante, ni diferenciación de especie en los registros de los avisos de arribo. El objetivo de este estudio fue obtener una perspectiva del estado de la pesquería de pulpo y la identificación de la especie de mayor captura. Para ello se analizaron tendencias espacio-temporales de las capturas, esfuerzo, ganancia y la captura por unidad de esfuerzo (CPUE) utilizando los avisos de arribo de SAGARPA de 1999 al 2008, y se dividió el complejo lagunar BM-BA en tres zonas: López Mateos ó zona I, Bahía Magdalena ó zona II y Bahía Almejas ó zona III. Se le realizó además una escala morfocromática de madurez gonádica y se determinó la proporción sexual de la especie más importante. La mayor captura, esfuerzo y ganancia se presentó para el año de 1999; la relación entre las variables de captura-esfuerzo fue positiva, es decir, que al incrementar el esfuerzo las capturas también lo hicieron, lo que podría indicar que la pesquería del pulpo tiene potencial de desarrollo. Aunado a lo anterior, no se encontró una relación significativa entre la CPUE y el esfuerzo, lo que indica que no se han registrado niveles de esfuerzo que hagan descender la CPUE lo que indica que la explotación es moderada.

Movement patterns of adult scallops (Pecten novaezealandiae) within a customary fisheries reserve: Implications for fine scale spatial management

Article

Feb 2016
FISH RES

The endemic scallop (. Pecten novaezealandiae) is patchily distributed around New Zealand's coastline and supports customary, recreational and commercial harvest. Little information exists on post-settlement movement patterns of this species, which if significant, could impact their distribution, thus influencing the effectiveness of spatial refuges to fishing such as rāhui (fisheries closure). The movements of P. novaezealandiae were examined within adult scallop habitat in a customary fisheries reserve, Te Whaka ā Te Wera (Paterson Inlet) Mātaitai, Rakiura (Stewart Island), New Zealand, by tracking the dispersal of tagged scallops from a central release point over two months. The average distance moved, calculated from recovered scallops, was 1.82. m per month, and these movement rates did not differ between the five sites or the two size classes examined. No significant directional movement was observed. The distribution of adult scallops is unlikely to be significantly affected by the scale of random movement observed. Once P. novaezealandiae are settled in appropriate habitat they are likely to only move in response to potential predators. Any spatial refuge created through management intervention, is likely to have positive effects through enhanced larval recruitment due to protection of breeding aggregations, not through movement of adults. The proposed reopening of the scallop fishery to hand collection with a prohibition on underwater breathing apparatus would maintain a deep water refuge for adult scallops, with potential benefits for adjacent fished shallow habitats through larval export.

Octopus tetricus (Mollusca: Cephalopoda) as an ecosystem engineer

Article

Full-text available

Dec 2014

The Sydney octopus (Octopus tetricus) occurs in unusual numbers on a shell bed of its prey remains that have accumulated as an extended midden where additional octopuses excavate dens. Here, O tetricus are ecosystem engineers, organisms that modulate availability of resources to other species and to their own species by causing physical state changes in materials. A community of invertebrate grazers and scavengers has developed on the shell bed. Fishes are attracted to the shell bed in numbers significantly greater than in nearby habitats. Large predators, including wobbegong sharks, were attracted to and fed on concentrations of fish, inhibiting the activities of the original engineers, the octopuses. Positive feedbacks included the accumulation of shell debris, increasing shelter availability for additional octopuses and aggregating fish. Negative feedbacks included reductions of nearby prey size and availability, aggression among octopuses, and predator limitation to octopus activity that would otherwise maintain the shell bed.

Putative Predators of Carcinus Maenas in Eastern Australia

Article

Full-text available

Sep 2015

Following the arrival of non-native species into suitable environments, interactions with native biota can influence non-native species proliferation and spread. The European shore crab, Carcinus maenas, is a global invader for which top-down control by predators has been implicated in limiting range expansion in its North American range. Little is known, however, about predators of this non-native species within its Australian distribution. We conducted quarterly trapping over 2 years in ten Australian estuaries to assess relationships between the abundance of C. maenas and native predators. Feeding assays between C. maenas and putative predators, identified from negative associations in occurrence, assessed the ability of putative predators to recognise C. maenas as prey. Six taxa were negatively correlated with C. maenas’ abundance and capable of eating the non-native crab. These were the blue swimmer crab (Portunus pelagicus), octopods (Octopus spp.), leatherjackets (Monocanthidae), yellowfin bream (Acanthopagrus australis), toadfish (Tetraodontidae) and the eastern fiddler ray (Trygonorrhina fasciata). Octopus spp. were rare in and blue swimmer crabs absent from mangroves; the habitat in which C. maenas was most abundant. A tethering experiment confirmed that Octopus spp. eat C. maenas in the field, with greater rates of mortality of the crab close to than away from the Octopus spp. lairs. Overall, our study indicates that a diverse assemblage of predators may prey upon C. maenas in southeastern Australia. Further studies assessing relative rates of predation by these predators on C. maenas are needed to assess whether they are exerting significant top-down control.

Growth and mortality of the juvenile common octopus (Octopus vulgaris) in pipe- and tire-type shelters placed in flow-through seawater tanks

Article

Full-text available

Feb 2015

The common octopus, which has a high growth rate and high market price, is a prime candidate for commercial marine aquaculture operations. We evaluated the effectiveness of two types of shelters (pipe and tire types) for juvenile common octopus growing out in flow-through seawater tanks. Growth rates were evaluated in two experiments. The first experiment (Experiment 1) ran for 72 days, and the second (Experiment 2; replicated) ran for 46 days. Each trial included 40 octopuses fed a diet of frozen sardine (Sardinops melanostictus) and swimming crab (Portunustri tuberculatus) at 3–8% of body weight once every 3 days. In the two experiments, the respective specific growth rates were 0.3 and 0.04%/day in pipe-type shelters and 0.00 and 0.88%/day in tire-type shelters, while the respective percentage survivals were 80 and 80% in pipe-type shelters and 70 and 90% in tire-type shelters. Shelter type had little influence on the growth rate (P < 0.05).

Octopus life history relative to age, in a multi-geared developmental fishery

Article

Full-text available

May 2015
FISH RES

The ability to obtain broad-scale age information for an exploited octopus population enables the identification of essential life history information, such as age at maturity, recruitment pulses and seasonal effects on growth. This study uses stylet weight (reduced internal shell) as a proxy to age 3494 Octopus (cf) tetricus, the target species of a rapidly developing octopus fishery in Western Australia. Samples were collected during 2008–2012 using passive shelter pots and active trigger traps. Both males and females were found to have similar maximum ages at 1.5 years, with males reaching maturity at 243 days compared to 379 days for females. The two gear types selected for different parts of the population, with shelter pots catching mostly octopus <1 kg total weight, who were a mixture of immature females and immature/mature males, whereas trigger traps caught octopus >1 kg total weight, of which 75% of the total catch were mature males. This variation in catch composition coupled with the inshore (shelter pot) and offshore (trigger trap) depth profiles of the gear types suggests offshore migration may be occurring. Back-calculated hatch months revealed six-monthly recruitment pulses and a positive relationship with ascending sea surface temperature and growth up to 22 °C.

Octopus vulgaris in the Caribbean is a specializing generalist

Article

Nov 2008

The diet of Octopus vulgaris was determined from the remains of 649 prey items gathered from the middens of 38 dens in a small area off the Caribbean island of Bonaire. Remains of 35 species of gastropod (19 % of the total), 19 bivalves (51 %) and 21. crustaceans (30 %) were identified and examined for mode of entry into hard-shelled prey. Although 60% of the gastropods were drilled, neither the size/weight ratio nor the presence of an operculum determined whether drilling occurred. There were strong differences in prey preference among individual octopuses, and the Cardona niche breadth index (B') of the midden items was 0.08, indicative of specialization. Examples include the exclusive preference for Pinna carnea by one den occupant. This study, by focusing on assessment. of preference at specific den locations, is the first to show that while the population had a wide choice of prey items, the individual choices were much narrower, indicating that octopuses were specializing generalists.

Biology Of The Planktonic Stages Of Benthic Octopuses

Article

Full-text available

Jun 2008
OCEANOGR MAR BIOL

Octopuses of the family octopodidae adopt two major life-history strategies. The first is the production of relatively few, large eggs resulting in well-developed hatchlings that resemble the adults and rapidly adopt the benthic habit of their parents. The second strategy is production of numerous small eggs that hatch into planktonic, free-swimming hatchlings with few suckers, simple chromatophores and transparent musculature. These distinctive planktonic stages are termed para-larvae and differ from conspecific adults in their morphology, physiology, ecology and behaviour. This study aims to review available knowledge on this subject. in benthic octopuses with plank-tonic stages, spawning characteristics and duration of planktonic life seem to play an important role in their dispersal capacities. Duration of the hatching period of a single egg mass can range from 2 days to 11 wk, while duration of the planktonic stage can range from 3 wk to half a year, depending on the species and temperature. Thus these para larvae possess considerable potential for dispersal. in some species, individuals reach relatively large sizes while living as part of the micronekton of oceanic, epipelagic waters. such forms appear to delay settlement for an unknown period that is suspected to be longer than for para larvae in more coastal, neritic waters. During the planktonic period, paralarval octopuses feed on crustaceans as their primary prey. in addition to the protein, critical to the protein-based metabolism of octopuses (and all cephalopods), the lipid and copper contents of the prey also appear important in maintaining normal growth. littoral and oceanic fishes are their main predators and defence behaviours may involve fast swimming speeds, use of ink decoys, dive responses and camouflage. sensory systems of planktonic stages include photo-, mechano-and chemoreceptors controlled by a highly evolved nervous system that follows the general pattern described for adult cephalopods. on settlement, a major metamorphosis occurs in morphology, physiology and behaviour. Morphological changes associated with the settlement process include positive allometric arm growth; chromatophore, iridophore and leucophore genesis; development of skin sculptural components and a horizontal pupillary response. At the same time, animals lose the kölliker organs that cover the body surface, the 'lateral line system' and the oral denticles of the beaks. strong positive phototaxis is a common response for hatchlings and some later paralarval stages but this response reduces, disappears or reverses after settlement. There are many gaps in our knowledge of the planktonic phases of benthic octopuses. Most of our understanding of octopus para larvae comes from studies of just two species (Octopus vulgaris and Enteroctopus dofleini) and knowledge of the vast majority of benthic octopus species with planktonic stages is considered rudimentary or non-existent. Research is needed in a variety of fields, from taxonomy to ecology. studies of feeding and nutrition are critical in order to develop the nascent aquaculture of key species and ageing studies are necessary to understand planktonic population dynamics, 106 particularly in commercially valuable species targeted by fisheries. current and potential anthro-pogenic impacts on these early life stages of octopuses, such as pollution, overfishing and global warming, are also identified.

Linking marine fisheries species to biogenic habitats in New Zealand: a review and synthesis of knowledge New Zealand Aquatic Environment and Biodiversity Report No. 130

Article

Full-text available

Jun 2014

Dwellers in dens on sandy bottoms: Ecological and behavioural traits of Octopus vulgaris

Article

Sep 2014

Four visual censuses targeting Octopus vulgaris living in dens on sandy bottoms were carried out from June to October 2013 in the National Park of the Atlantic Galician Islands (NW Spain). Censuses were undertaken by scuba diving between 5 and 21 m depth in daytime. The total area swept was 13.75 ha. There were no significant differences between octopus presence in dens during open and closed fishing seasons. Depth had a significant negative relationship with occupancy. The average number of dens per 1000 m2 was 3.84±0.84 in June and 3.89 in October. The area per den was 260 m2. Den number estimations varied between 1586 and 2057. The largest number of dens (76.5%) was found between 5 and 10 m depth. Den distribution was clumped. No significant differences were found between octopus size classes (small, medium and large) and den diameter. Associate dens were observed. There were no significant differences in den diameter and shell types found around the middens. Many dens could be “permanent”. Drilling bivalve shell behaviour is discussed. The surveyed area had around 1100 individuals, mainly small specimens. No significant differences were found between octopus size and depth. Substrate, den type and food abundance and availability (especially razors Ensis arcuatus) seem to be the main factors influencing dens and octopus density and distribution. Den availability does not appear to be a limiting factor in this case. Temperature, den availability, predators and fishing pressure influencing density and distribution are discussed. Rodas inlet may be a preferential habitat for O. vulgaris individuals ranging from 200 to 2000 g, but especially small specimens (≤1000 g).

Timing mussel deployments to improve reintroduction success and restoration efficiency

Article

Oct 2022

The loss of newly translocated species directly contributes to low rates of reintroduction success in both terrestrial and aquatic ecosystems. In this study, experimental reintroductions of green-lipped mussels Perna canaliculus into a shallow coastal habitat were conducted across 5 week-long experimental translocations within a 10 mo period (April 2021-January 2022) to relate temporal variations in predator abundance, predator size, and environmental parameters (water temperature, rainfall, days before/after full moon, turbidity, wind speed, wind direction) to variations in mussel survival. Predator counts from timelapse camera images gathered over the first 4 d after each deployment were used as a proxy for potential predator pressure. Timelapse images (n = 8561) allowed for a census of 2371 individuals from 10 different mobile species, 5 of which were known bivalve predators (Australasian snapper, New Zealand eagle ray, rig shark, octopus, and an unidentifiable ray species), with Australasian snapper contributing to 98% of overall species counts. At the end of the study, mean mussel survival ranged from 0 ± 0 SE% to 56 ± 8 SE% and was best predicted by changes in turbidity and the total number of predators among deployments (R ² = 0.445). Patterns in predator abundance were best explained by time of year and did not share strong correlations among environmental parameters (rho = 0.015). These results suggest that planning deployments of mussels for cooler times of the year when water clarity is high and predator abundance is low may substantially increase immediate survivorship of translocated mussels and improve reintroduction success.

The waste collector: information from a pilot study on the interaction between the common octopus (Octopus vulgaris, Cuvier, 1797) and marine litter in bottom traps fishing and first evidence of plastic ingestion

Article

Jan 2022
MAR POLLUT BULL

Few studies focused on behaviour adaptations of organisms to marine litter (ML) pollution in Mediterranean Sea. This research, investigates on some behavior traits of Octopus vulgaris, focusing on the interaction with ML during the artisanal fishing activities by the bottom traps in a small coastal area of the southern Tyrrhenian Sea. For the first time, this pilot study uses an integrated approach based on the Fishermen Ecological Knowledge as well as the analysis of ML found in the traps. First assessment of plastic ingestion in this species are also reported. Plastic and metal were the predominant ML categories observed into the bottom traps. A total of 62 plastics, mainly small microplastics and fibres shaped, were ingested. The ML finding in the bottom traps suggests an interesting behavior of the common octopus regarding its interaction with ML, in fact, it seems to bring ML inside its dens, as a collector.

Shell-Exchange Behavior in a Hermit-Crab-Like Tanaidacean (Crustacea: Malacostraca)

Article

Dec 2019
ZOOL SCI

Keiichi Kakui

This study describes shell-exchange behavior in the hermit-crab-like tanaidacean Macrolabrum sp. (Pagurapseudidae: Pagurapseudinae) under captive conditions. I observed one shell exchange by Macrolabrum sp., the behavioral sequence of which was as follows: a shell-carrying tanaidacean 1) grasped the edge of the aperture of an empty gastropod shell with its right cheliped; 2) inspected the condition inside the shell four times by inserting the anterior portion of its body into the shell; and 3) moved into the shell, posterior end (pleotelson) first. The elapsed time from the initial grasping of the empty shell to completing the move into it was 2 min 20 sec. In contrast to a Pagurapseudes tanaidacean and hermit crabs, the individual of Macrolabrum sp. did not examine the external surface of the shell during the single shell exchange observed.

The Associations between Fishes and Molluscs

Chapter

Apr 2014

Ilan Karplus

This chapter talks about cephalopod structures and the discussion is limited to those structures that are of importance for understanding the partnership between fishes and cephalopods and, particularly, the foraging associations with octopuses. Octopuses feed mainly on bivalves, gastropods and crustaceans. The glochidia host relationship is discussed because bitterling may serve as their hosts and the laying of eggs into bivalves by these fishes may be affected by the brooding of glochidia. This chapter talks about the central role played by the mussel in the bitterling biology: attraction of the fish to the mussel, choice of oviposition sites, adaptations of eggs, embryo and larvae for development inside the mussel, impact of the mussel on male and female reproductive behavior, utilization of mussels by sympatric bitterling species and, finally, the costs and benefits for the mussel from being in association with fishes and the possible coevolution of the bitterling–mussel partnership.

Cephalopod culture: current status of main biological models, and research priorities, in: Vidal, E.A.G (Ed.), Advances in cephalopod science, biology, ecology, cultivation and fisheries

Article

Full-text available

Jun 2014
ADV MAR BIOL

A recent revival in using cephalopods as experimental animals has rekindled interest in their biology and life cycles, information with direct applications also in the rapidly growing ornamental aquarium species trade and in commercial aquaculture production for human consumption. Cephalopods have high rates of growth and food conversion, which for aquaculture translates into short culture cycles, high ratios of production to biomass and high cost-effectiveness. However, at present, only small-scale culture is possible and only for a few species: the cuttlefish Sepia officinalis, the loliginid squid Sepioteuthis lessoniana and the octopuses Octopus maya and O. vulgaris. These four species are the focus of this chapter, the aims of which are as follows: (1) to provide an overview of the culture requirements of cephalopods, (2) to highlight the physical and nutritional requirements at each phase of the life cycle regarded as essential for successful full-scale culture and (3) to identify current limitations and the topics on which further research is required. Knowledge of cephalopod culture methods is advanced, but commercialization is still constrained by the highly selective feeding habits of cephalopods and their requirement for large quantities of high-quality (preferably live) feed, particularly in the early stages of development. Future research should focus on problems related to the consistent production of viable numbers of juveniles, the resolution of which requires a better understanding of nutrition at all phases of the life cycle and better broodstock management, particularly regarding developments in genetic selection, control of reproduction and quality of eggs and offspring.

Symbiosis in Fishes: The Biology of Interspecific Partnerships

Article

Apr 2014

Ilan Karplus

Symbiosis in Fishes provides comprehensive coverage of the biology of partnerships between fishes and invertebrates, ascending the phylogenetic scale, from luminescent bacteria, sponges and coelenterates to molluscs, crustaceans and echinoderms. Both facultative and obligatory partnerships are reviewed with emphasis on the behavioral, ecological and evolutionary aspects of fish symbiosis. Each of the eight chapters of this book focuses on a different group of partners. The structure, physiology and anti-predatory strategies of each group are described to provide the necessary background for the understanding of their partnerships with fishes. The formation of the associations, the degree of partner specificity and its regulation, as well as the benefits and costs for the fishes and their associates, communication between partners and their possible co-evolution are discussed in each chapter. This is the first attempt to critically review in a single volume all associations of fishes with invertebrates based on the latest studies in these areas, together with studies published many years ago and little cited since then. Symbiosis in Fishes provides a huge wealth of information that will be of great use and interest to many life scientists including fish biologists, ecologists, ethologists, aquatic scientists, physiologists and evolutionary biologists. It is hoped that the contents of the book will stimulate many to further research, to fill in the gaps in our knowledge in this fascinating and important subject. Libraries in all universities and research establishments where biological sciences are studied and taught should have copies of this exciting book.

Effects of competition and egg predation on shelter use by Octopus tehuelchus females

Article

May 2013

Parental care in the ocean ranges from provision to eggs and embryos to protection from predators. In particular, nest attendance has several benefits associated with relatively higher survival rates, lower vulnerability to predation and parasitism, and faster development rates. The quality of shelters matters, and adults of many species have to compete for suitable shelters. Here, we studied whether shelter type for brooding and egg protection from predation could be a determinant of competition among adults in the cephalopod Octopus tehuelchus. To this end, we (1) assessed the abundance of different types of shelters and preference under field and laboratory conditions, (2) tested the effect of intraspecific competition for shelters, (3) estimated density of potential sources of embryo mortality, and (4) determined the role of female protection in egg survival against predators. We found that in areas where shelters for development are scarce, females compete with males for the most suitable shelters. Fecundity depends on the female size, and shelters with higher volume are preferably selected by females. Excluding the brooding female from shelters resulted in increased egg mortality due to predation by octopus males and removal by chitons. We suggest that, in this species, shelter availability poses a constraint to brooding and affects total parental investment in reproduction and predation risk on eggs. This constraint may also take place in other marine invertebrates with similar life history traits, especially in areas where shelter is limited.

Identification and characterization of adeaquate habitats for spawning and early stages of development of commercially important cephalopods

Conference Paper

Full-text available

Jan 2012

Putative Predators of Carcinus Maenas in Eastern Australia

Article

Oct 2014

Clifford J Garside

Abstract Following the arrival of non-native species into suitable environments, interactions with native biota can influence non-native species proliferation and spread. The European shore crab, Carcinus maenas, is a global invader for which top-down control by predators has been implicated in limiting range expansion in its North American range. Little is known, however, about predators of this non-native species within its Australian distribution. We conducted quarterly trapping over 2 years in ten Australian estuaries to assess relationships between the abundance of C. maenas and native predators. Feeding assays between C. maenas and putative predators, identified from negative associations in occurrence, assessed the ability of putative predators to recognise C. maenas as prey. Six taxa were negatively correlated with C. maenas’ abundance and capable of eating the non-native crab. These were the blue swimmer crab (Portunus pelagicus), octopods (Octopus spp.), leatherjackets (Monocanthidae), yellowfin bream (Acanthopagrus australis), toadfish (Tetraodontidae) and the eastern fiddler ray (Trygonorrhina fasciata). Octopus spp. were rare in and blue swimmer crabs absent from mangroves; the habitat in which C. maenas was most abundant. A tethering experiment confirmed that Octopus spp. eat C. maenas in the field, with greater rates of mortality of the crab close to than away from the Octopus spp. lairs. Overall, our study indicates that a diverse assemblage of predators may prey upon C. maenas in southeastern Australia. Further studies assessing relative rates of predation by these predators on C. maenas are needed to assess whether they are exerting significant top-down control.

Characteristics by the Behaviour and Habits of the Common Octopus (Octopus minor)

Article

Dec 2003

In order to develop a logical method for using selective fishing gear, the behaviour and habits of the aquatic animals must be investigated. However, until now, little national research has been carried out to investigate the behaviour and habits of the common octopus (Octopus minor). The purpose of this study henceforth, is to compile necessary behavioral data to develop fishing gear to catch the common octopus. Behaviour and habits of the common octopus were observed while breeding in a water tank from February to May, 2003. The feeding habits of common octopus are more vigorous at night than in the daytime. The common octopus feeds on 1-4 bait crabs per day and consume each crab in 40-50 min. The sensory organs of the common octopus are more influenced by the sense of touch and smell, than by vision. Using live bait is more effective and advantageous than using dead bait, as the common octopus responded more to live bait. The hiding habits of the common octopus were very intensive, as they hid around all the shelters that were provided in this study. They demonstrated territorial behavior and struggled to maintain their sphere of influence. In addition, out of the various colors for shelters and bait supplied, the common octopus preferred light colors.

Long-term high-density occupation of a site by Octopus tetricus and possible site modification due to foraging behavior

Article

Jul 2012
Mar Behav Physiol

We report observations of wild octopuses (Octopus tetricus) living in close proximity at a site centered on a single den that has been occupied since at least November 2009. Numbers observed on survey dives range from 2 to 11 (average of 5.48). We hypothesize that long-term occupation of the site has led to its physical modification through the accumulation of shells brought in during foraging, and that this “ecosystem engineering” has in turn resulted in higher densities being viable at the site.

The Future of Breach of Confidence and the Protection of Privacy

Article

Jan 2007

Tanya Aplin

Using the impetus of the Human Rights Act 1998, English courts have significantly reshaped the law of confidence in an attempt to better protect privacy. This article argues that there is a persuasive case for no longer utilising the equitable action for breach of confidence and instead recognizing a limited tort of privacy, in the form of misuse of private information. This would minimise any possible risk of distortions to the law of confidence as it relates to non-personal information, accord with current judicial practice, and provide a sound basis for awarding compensation for non-pecuniary harm and exemplary damages. Such a tort would also be suitably confined so as to minimise confusion and would be a constitutionally defensible step for the courts to take. Once a tort of misuse of private information is recognised courts can begin the crucial process of articulating and clarifying the internal principles of such a tort, along with its relationship to the ‘old’ law of confidence.

Shelter Utilization by the Molluscan Cephalopod Octopus bimaculatus

Article

Full-text available

Jan 1982

Richard F Ambrose

Estimating total abundance of a large temperate-reef fish using visual strip-transects

Article

Full-text available

Jan 1987

Total abundance estimates for the large, common, reef fish Cheilodactylus spectabilis (Hutton) were obtained for a marine reserve and adjacent section of coast in north-eastern New Zealand during 1985. Visual strip-transects were used to estimate abundance and size structure in both areas. The accuracy, precision and cost efficiency of five transect sizes (500, 375, 250, 100, 75 m2) were examined over three times per day (dawn, midday and dusk), by simulating transects over mapped C. spectabilis populations. Two transect sizes showed similarly high efficiency. The smaller of the two (20x5 m) was chosen for the survey because of the general advantages attributable to small sampling units. Biases related to strip-transect size are discussed. Preliminary sampling indicated that C. spectabilis was distributed heterogeneously, and that density was habitat-related. An optimal stratified-random design was employed in both locations, to obtain total abundance and size-structure estimates. This reduced the between-habitat source of variability in density. The total number of sampling units used was governed by the time available. The resulting total abundance estimates obtained were 18 3382 886 (95% confidence limit) for the 5 km marine reserve, compared to 3 9871 117 for an adjacent, heavily fished 4 km section of coast. When corrected for total area and habitat area sampled, this represented a 2.3-fold difference in abundance. If sampling had been designed to detect an arbitrary 10% difference in abundance within each habitat, an infeasible 440 h of sampling would have been required. Size-frequency distributions of C. spectabilis at the reserve had a larger model size class than distributions from the adjacent area. The data suggest that reserve status is causal in these differing abundance and size structure estimates.

Dynamics of shallow-water populations of Octopus dofleini

Article

Full-text available

Aug 1984

Octopus dofleini (Walker) is a common inhabitant of shallow subtidal communities in the Northeast Pacific. The abundances of octopuses at two sites monitored since 1977 have fluctuated greatly during this period. The populations reached high abundances in mid-summer and, during some years, mid-winter. The highest abundances at the two sites did not coincide. There was a constant influx of new octopuses into both study sites, with the greatest immigration occurring in early summer. The octopuses captured spanned a wide range of weights every month, with no clear size classes or seasonal trends in size. The weights of newly-captured octopuses, however, did differ between the sexes and seasons: males weighed more on the average than females, and male weight decreased from winter to fall while female weights did not change O. dofleini appeared to recruit throughout the year; the smallest octopuses occurred between May and November and the greatest number of small octopuses was found in July and August in most years. Females predominated at both study sites throughout the year. However, males predominated among octopuses caught in traps at nearby locations, suggesting that the skewed sex ratios were due to behavioral differences between the sexes.

Den associates of the giant Pacific octopus, Octopus dofleini (Wulker)

Article

Jul 1978

During a population study of Octopus dofleini, the dens of octopus were checked for other organisms. A variety of organisms were consistently associated with the dens or wirh debris accumulating at the den arising from the feeding behaviour of rhe octopus. These co-inhabitants included fishes, sea stars and crabs. For some organisms the association involved scavenging, but in other cases the relationship was not clear.

Choice and competition: Their effects on occupancy of Shell Homes by Octopus joubini

Article

Aug 1982
Mar Behav Physiol

Jennifer A. Mather

Observations of Octopus joubin's home choices in the laboratory and home occupancy in the field sometimes give conflicting results. In the laboratory octopuses choose shells of a specific size range, with a small opening and little light access. They also choose empty Gastropod shells over Bivalve ones. In the field they are normally found in Bivalve shells (Trachycardium cockles). This is partly a result of competition for Gastropods by hermit crabs and Bleniid fishes. Laboratory studies show that these competitors can only be supplanted half the time ; octopuses’ shelter occupancy is shaped both by choice and by competition.

Interaction of juvenile Octopus vulgaris with scavenging and territorial fishes

Article

Jan 1992
Mar Behav Physiol

Jennifer A. Mather

Juvenile Octopus vulgaris were often approached or accompanied by fish (<15cm distant), mainly the scavenging slippery dick and the territorial dusky damselfish. Fish were significantly more often near octopuses (56/60 min) when the latter were foraging across the rocky bottom, compared to 26/60 minutes or less when the octopuses were stationary. Octopuses generally ignored fish (83%), although they sometimes changed colour (9%) or made an overt body action (7%), especially when fish attached. The slippery dick caught prey escaping from octopuses and fed on remains of food left in octopus middens. The damselfish attacked foraging octopuses and may have benefited by excluding octopuses who could compete for shelter or eat their eggs. The octopuses excluded from potential foraging areas were made more localizable by predators due to the presence of slippery dicks. These common interactions are another manifestation of Cephalopods’ competition with fish in the marine environment.

Feeding behaviour of broody female Octopus vulgaris

Article

Aug 1978

Jerome Wodinsky

When female Octopus vulgaris reproduce, their feeding behaviour changes. Food intake decreases, on the average, by 70% of normal intake per meal, and additionally by 65% of the normal number of meals, a total decrease of about 90%. The method of predation upon gastropod prey changes from boring a hole in the shell, secreting a toxin, and pulling out the affected snail, to pulling the living snail out by force, and ceasing to bore. The fact that the post-egg-laying female expends energy to extract the body of the snail which it then scarcely eats may be a unique pattern of feeding behaviour.

Breeding season of Octopus vulgaris

Article

Jan 1972

Jerome Wodinsky

Female Octopus vulgaris Cuvier mated in the laboratory in every month tested. Females maintained in isolation after capture and not mated in the laboratory laid eggs, fertile and infertile, each month of the year. The longest period of sperm viability was 104 days. Young specimens weighing between 4.0 and 66.0 g were found regularly. It is concluded that O. vulgaris breeds throughout the year, at least in Bahamian waters.

Factors affecting the spatial distribution of natural populations of Octopus joubini Robson

Article

Nov 1982

Jennifer A. Mather

Observations were made on the density and distribution of Octopus joubini in its natural environment. The average density of octopuses was 1/33 m2 but their distribution was clumped. This distribution correlated significantly with the distribution of molluscan shells in which they hid. In addition, octopuses were attracted to sites that had been enriched with extra empty gastropod shells. Since site stability was not observed and they were not repelled from one another when placed at a high density, octopuses were probably not spaced by social pressure. Small crab species, the normal prey of O. joubini, were at a very high density of 30/m2, and food abundance probably did not limit octopus number. The main factor affecting distribution of this population of octopuses may be predator pressure acting through the availability of places to hide.

Penetration of the Shell and Feeding on Gastropods by Octopus

Article

Aug 1969

Jerome Wodinsky

The behavior of the octopus when feeding upon shelled molluscs is described in four steps: selection of prey, boring a hole in the shell, secreting into the borehole, and pulling out the body oC the mollusc and eating it. Selection of some gastropod prey is determined by a firm, deep, either partial or complete obstruction in the aperture of the shell. Selection of other prey, gastropods, pelecypods, and amphineurans, may be based upon resistance by the mollusc to the application of force by the octopus. Drilling of the hole is done by the radula. Since the octopus will drill and secrete into empty shells with obstructions in the apertures, metabolites from a live mollusc are unnecessary. This technique can be usedto collect the secretion. The frequency of occurrence and the eflect of the secretion are discussed. The hypothesis that the octopus first tries by force to pull out the body and, failing to do so, drills a hole in the shell is experimentally supported. The conditions under which the octopus drills or pulls out the body of the mollusc are incompletely understood. The octopus may drill two or more shells in succession without feeding upon the previously drilled and weakened snail. No two steps in the behavioral sequence are necessarily linked to each other. The drilling-feeding patterns are complex and plastic.

Habitat selection and shelter use by Octopus tetricus

Abstract

No full-text available

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