Octopus Tetricus (Gloomy Octopus) Gould, 1852

DWhatley

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#1
Body Size, Growth and Life Span: Implications for the Polewards Range Shift of Octopus tetricus in South-Eastern Australia
Jorge E. Ramos, Gretta T. Pecl, Natalie A. Moltschaniwskyj, Jan M. Strugnell, Rafael I. León, Jayson M. Semmens 2014 (full article)

Abstract
Understanding the response of any species to climate change can be challenging. However, in short-lived species the faster turnover of generations may facilitate the examination of responses associated with longer-term environmental change. Octopus tetricus, a commercially important species, has undergone a recent polewards range shift in the coastal waters of south-eastern Australia, thought to be associated with the southerly extension of the warm East Australian Current. At the cooler temperatures of a polewards distribution limit, growth of a species could be slower, potentially leading to a bigger body size and resulting in a slower population turnover, affecting population viability at the extreme of the distribution. Growth rates, body size, and life span of O. tetricus were examined at the leading edge of a polewards range shift in Tasmanian waters (40°S and 147°E) throughout 2011. Octopus tetricus had a relatively small body size and short lifespan of approximately 11 months that, despite cooler temperatures, would allow a high rate of population turnover and may facilitate the population increase necessary for successful establishment in the new extended area of the range. Temperature, food availability and gender appear to influence growth rate. Individuals that hatched during cooler and more productive conditions, but grew during warming conditions, exhibited faster growth rates and reached smaller body sizes than individuals that hatched into warmer waters but grew during cooling conditions. This study suggests that fast growth, small body size and associated rapid population turnover may facilitate the range shift of O. tetricus into Tasmanian waters.
 

haggs

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#2
D, after watching the growth of local octopus (O tetricus) around here the 11 months mentioned would seem to be close to true. Those that I have watched grow, seem to mature rather quickly as in 8 months before they move out of the smaller rock pools. Those that I have seen not in rock pools tend to be larger mature octo's, I'm assuming they then move out and mate, and start the cycle over again.
 

DWhatley

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#3
I found the lifespan unexpected for the size. Our all warm water animals of that size usually live over a year, only the dwarfs are known for 8-10 months (several of mine born in captivity lived over 12 but not all but 10 months was an average).
 

DWhatley

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#4
Will Climate Change Bring an Invasion of the Octopuses—Or Halt It?
By Katherine Harmon Courage | September 5, 2014 |

Katherine Harmon summarized the expansion of the Gloomy octopus @haggs, note her comment about the importance to fisheries. I wonder if there is a large export to Asian countries that is not locally known.

The fate—and location—of the common Sydney octopus is of interest not only to biologists, but also to local fisheries, which depend on this species for a sizable chunk of their catches.
 

DWhatley

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#5
Sydney octopuses heading south as Tasmanian waters warm

An oddity in this article mentions that the long-spine urchin is negative to the environment where its disappearance in the Caribbean has been detrimental to reefs.

A Tasmanian researcher has found octopuses from Sydney are reproducing in Tasmanian waters.
The common Sydney octopus was thought to have migrated south because of rising ocean temperatures.
The creature was usually found between southern Queensland and southern New South Wales.
Jorge Ramos, a PhD candidate from the Institute for Marine and Antarctic Studies (IMAS), has been studying hundreds of octopus samples from near the east coast of Flinders Island.
"So far, the octopus seems to be doing well here in Tasmania," he said.
Mr Ramos found the species could reproduce in Tasmanian waters, had a fast growth rate and rapid population turnover.
That meant numbers could be set to increase.
"If the octopus is growing fast and short lifespan, then it might have better chances to thrive under new conditions in Tasmanian waters," he said.
Fears for commercial marine species
The octopus is not the only species on the move.
Others, such as the long-spine sea urchin, have wreaked havoc on Tasmania's marine environment.
Craig Johnson from IMAS said it is unclear what ecological impact the common Sydney octopus was having.
There are reports of octopus preying on rock lobster.
Jorge Ramos, IMAS
"Most of the species that come down here are just going to sit in the background and aren't necessarily going to have a major impact on diversity or production or fisheries or any of those things we're concerned about," he said.
"Unfortunately, some of them do."
Mr Ramos said the migration could be bad news for some fisheries.
"Well it might prey on other commercial species; for example there are reports of octopus preying on rock lobster," he said.
Mr Ramos believed it could result in more catches for the commercial octopus industry.
But Michael Hardy, the only commercial octopus operator in Bass Strait, was not convinced.
"The research and the money spent on trying to sort out this tetricus octopus would've been far better spent on the octopus we've already got in Tasmanian waters," he said.
Mr Ramos was now waiting on results to pinpoint exactly what the octopus had been feeding on in Tasmania.
 

DWhatley

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#6
Genetic evidence extends the known distribution of Octopus insularis to the mid-Atlantic islands Ascension and St Helena
Michael D. Amora, Vladimir Laptikhovsky, Mark D. Norman, Jan M. Strugnell 2015 (subscription)

Interesting to note that Octopus Tetricus (Gloomy) is more closely related to O. vulgaris than O. bimaculoides/bimaculatus as I have often wondered if bimacs were a close relative.(DWhatley)


Abstract
Recent molecular studies have proved beneficial in providing taxonomic resolution within the Octopus vulgaris species complex, therefore aiding in the appropriate management of this high value global fisheries resource. This study used the mitochondrial ‘barcode of life’ gene Cytochrome Oxidase subunit I(COI) to investigate the identity of shallow-water benthic octopuses in the mid-Atlantic Ocean and their relationship to members of the Octopus vulgaris species complex. Maximum likelihood and Bayesian phylogenetic inference placed individuals collected from two tropical islands, Ascension and St Helena, into a highly supported monophyletic clade with the North Brazilian species O. insularis (BS = 81, PP = 1), extending the known distribution of O. insularis to Ascension and St Helena Islands. Octopus vulgaris and two other member species of the O. vulgaris species complex, O. tetricus and O. cf. tetricus formed a highly supported monophyletic clade (BS = 99, PP = 1). Interspecific distances between the O. mimus group (O. mimus, O. bimaculoides, O. maya and O. insularis) and the O. vulgaris species group (O. vulgaris, O. tetricus and O. cf. tetricus) ranged from 14.7–26.0%, and an estimated date of divergence suggests these groups diverged from a common ancestor between 19.0 and 40.9 million years ago.
 

DWhatley

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#7
Innovative development of the Octopus (cf) tetricus fishery in Western Australia
FRDC Project No 2010/200 Anthony. M. Hart, Stephen. C. Leporati, Ross. J. Marriott and Dave Murphy 2016 (pdf)

Executive Summary
In 2010 the broad-scale introduction of a new gear type, the trigger trap, saw a 260% (33 t in 2009 to 119 t in 2010) increase in octopus landings in the Western Australian Developmental Octopus Fishery (DOF). Deployed in waters previously unfished by the DOF, initial catches demonstrated that trigger traps were more efficient and captured a different component of the population, compared to open-ended shelter pots traditionally used in the fishery. This shift caused a surge of interest in commercial octopus fishing. Thus, creating a need to build a solid research foundation on the biology and population dynamics of the key species, to help ensure the ecologically and economically sustainable developmental of the octopus fishery. Conducted by the Department of Fisheries Western Australia, during 2010 – 2014, this project provided a unique opportunity to investigate a new phase of a fishery at inception. Octopus has always been a byproduct of the rock lobster fishery, however targeted fishing for octopus was established in 2001, and fishing effort during the first nine years of the DOF was constrained to a small number of operators in specific inshore (shallower than 20 m) locations. This restriction was a product of the tendency of the light weight shelter pots to be buried in exposed waters. The heavier, larger and active trigger trap was designed specifically to catch the target species Octopus (cf) tetricus and enable fishing in a wider variety of habitats. The success of the trigger trap was typified by its rapid ascension as the dominant gear type (landing 95% of all catch in 2012) in the fishery and the expansion of the fleet from 6 vessels (5 shelter and 1 trigger pot vessels) in 2009 to 17 (4 shelter and 13 trigger pot vessels) by 2013. With vessels operating from Kalbarri in the north to Busselton in the South at depths up to 40 m, this rapid transformation of the DOF is a significant expansion. Determining the size of the resource and sustainable harvest rates requires detailed information on the growth, maturation, mortality and recruitment of the population, all of which are underpinned by age data. The present study was the first of its kind to age a wild population of octopus, using a combination of direct and indirect ageing methods. Through the discovery of a strong relationship between the number of growth rings found in a stylet (reduced internal shells) and stylet weight, the ages of 3500 octopuses were obtained, using stylet weight as a proxy for age. Maximum age was calculated at ~1.5 years for both males and females, with males maturing at ~240 days compared to ~380 days for females. This information enabled the construction of life history profiles of the stock in relation to gear type. Thus revealing, trigger traps were ~15 times more effective than shelter pots and caught predominantly (75%) mature males weighing >1 kg, whereas shelter pots caught a mixture of males and females that mostly weighed <1 kg and were immature. Spawning occurred throughout the year with six monthly hatching pulses during transitional temperatures. Spatial differences in average size of the catch indicated that offshore migration to reef habitats for spawning may be occurring. The life history profile was combined with spatially explicit commercial catch and effort data, and a dedicated depletion study, to determine density estimates (individuals / km2 ). The extent of harvestable area by trigger trap (depths 20 – 50 m) across the western and southern coasts of Western Australia, were calculated at ~34,000 km2 . The harvestable area was split xii Fisheries Research Report [Western Australia] No. 270, 2016 into four fishing zones for ease of analysis and management. Density and area estimates were used to determine biomass and abundance estimates, for three distinct scenarios: precautionary, conservative and possible. The precautionary scenario was based on the assumption that the present percentage (7%) of area fished in the main fishing zone represents the extent of optimal fishing grounds for each zone. The precautionary and possible scenarios, expanded upon this at 20% and 30% of each zone being optimal fishing grounds, respectively. Overall biomass estimates ranged from 8,626 t (precautionary) to 12,605 t (possible). The biomass and abundance estimates, along with the biological data were then used in a per-recruit model to determine a range of sustainable harvest levels for each scenario. From the lowest estimation of 879 t to the highest of 2261 t, it appears likely that the DOF should be able to realistically maintain landings in the proximity of ~1000 t per year. Thus indicating there is considerable room for expansion in the fishery, which could lead to the development of a significant industry for Western Australia. Progression from a 200 t to a 1000 t fishery will require progressive and conscientious development of the DOF on distinct spatial and temporal scales. For the short life span, fast growth rates, high fecundity, semelparity and minimal overlap between generations, observed in the O. (cf) tetricus population, are typical traits of cephalopod stocks. Such characteristics, along with a tendency to be strongly influenced by environmental variables (namely temperature) indicate that the O. (cf) tetricus population will most likely experience high fluctuations in abundance from year to year. Therefore to minimise the potential impacts of fishing pressure on stocks and in turn such fluctuations on economic sustainability, it is recommended that expansion is incrementally increased, using total catch limits for each fishing zone. To determine the efficiency and validity of such an approach, will require monthly monitoring of catch rates, annual fishery assessments and ongoing biological monitoring. The present study has provided a detailed depiction of the DOF’s harvest potential, across large expanses of unfished areas. As the fishery progressively develops, further information will be obtained on the extent of optimal and sub-optimal habitats in each zone, thus providing insights into how the population may respond to fishing effort on local and regional scales. By providing a detailed life history profile for O. (cf) tetricus, this study has also established a strong foundation for future research on O. (cf) tetricus trophic role and the potential ecological impacts of octopus fishing. Information that will be essential to maintain the fisheries social licence to operate as the fishery expands.
 

DWhatley

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#8
The Australian 'gloomy octopus' leads a murky wave of climate change invasions
June 26, 2018 by Amy Mcdermott, Oceana.org

Gloomy octopuses used to blend in. They were just another cephalopod, drab-gray and medium-bodied, living in the ocean off east-central Australia. Until, a few decades ago, the octopuses started to spread.

They crept south, establishing populations down Australia's East Coast, a climate change hotspot where seawater temperatures are rising almost four times faster than the global average. Gloomies love the heat—and chowing down on shellfish. If the newcomers' appetites disrupt existing fisheries, researchers say, they could spell trouble.
In Australia and around the world, ocean animals are relocating because of climate change, often with consequences for fisheries. Gloomy octopuses are just one of many marine species on the move. Their expansion is a harbinger of what's to come in places warming slower than Australia. Forget blending in, climate consequences have arrived. ...
 

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