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In upwelling systems around the world, octopus abundance is forecast by marine productivity linked to upwelling strength, often indicated by sea-surface temperatures. Climate change may disrupt populations of marine animals that are linked to such temperature-dependent events. We analysed the relationship of the abundance of giant Pacific octopuses (Enteroctopus dofleini) to Gulf of Alaska and Washington State water temperatures. Abundance was measured in targeted visual surveys in Prince William Sound, Alaska, over the period 1995–2016 and from REEF.org diver surveys in Washington State from 2003 to 2019. Octopus counts from both survey programs had significant negative correlations with water temperatures over the previous 2.5–4 years. Water temperature accounted for from 0.41 to 0.71 of the variance (R 2) in octopus abundance in eastern Gulf of Alaska waters located in ocean currents up-stream of the survey areas, and up to 0.81 of the variance in Washington State waters. These negative correlations provide a possible predictive index for octopus abundance as measured by targeted visual surveys. These methods may be useful tools in management of octopuses and indicate impacts of climate change on North Pacific coastal marine ecosystems. Climate change is warming the world's oceans, and will disrupt marine populations. We have shown that in Alaska and Washington nearshore waters, the recruitment and abundance of giant Pacific octopuses fell sharply following years of higher average ocean temperatures. Visual surveys and ocean temperature data together may allow better management of octopus harvests. [ABSTRACT FROM AUTHOR]

Understanding the trophic ecology of the giant Pacific octopus Enteroctopus dofleini is challenging in developing marine ranches and in reestablishing its regional stocks against the severe stress of fishing. We adopted carbon and nitrogen stable isotope techniques (termed δ13C and δ15N, respectively) to identify the trophic niche (i.e., pathways and positions) of this species systematically in the entire food webs of two marine ranches off the east coast of the Korean peninsula. While a slight spatial shift in the isotopic nestedness of faunal communities was observed, the δ13C and δ15N values of consumers were distinct and separate among functional groups at both ranches. The consumer δ13C values spanned a broad range between pelagic and benthic sources of organic matter, and their δ15N values recorded a stepwise trophic-level enrichment, indicating that suspension feeders and herbivore-deposit feeders served as baselines of pelagic- and benthic-based trophic pathways, respectively. The δ13C values of predators, including E. dofleini, were arrayed between the two primary consumer groups. Neither δ13C nor δ15N values showed any remarkable variations with increasing octopus weight. Dietary mixing-model calculations indicated that E. dofleini is a generalist predator relying on both benthic- and pelagic-affinity prey, similar to some teleost species that consume a diverse spectrum of prey. In contrast, other teleost groups showed prevalent trophic links with either pelagic- or benthic-based pathways. The trophic-level estimations revealed that E. dofleini occupies an intermediate position slightly below the teleosts. A lack of discrete trophic positions between E. dofleini and teleosts seemed to be indicative of the released teleost predation but instead reflects the imposed food competition. Overall, the results demonstrated that despite compositional changes in the taxa constituting individual trophic groups, E. dofleini occupied a very similar trophic niche in both ranching systems. Finally, as extracted from information based on octopus marine ranches launched on natural rocky bottoms, our isotopic evidence provides a greater understanding of the trophic ecology of this octopus species in nearshore natural habitats along the southwestern margin of its distribution range.

There is a lack of information available on octopuses in Alaskan waters and because of this lack of data, catch limits are set based on historical incidental catch rates or survey biomass estimates that are likely to be overly conservative. This issue is further exacerbated by the fact that catch accounting for octopuses assumes 100% mortality for all octopuses caught whether retained or discarded. We examined the delayed mortality of the giant Pacific octopus, Enteroctopus dofleini , captured in Pacific cod, Gadus microcephalus , pot fisheries in the Gulf of Alaska. Octopuses captured as bycatch during commercial fishing operations were held on the vessel and brought back to the laboratory to assess delayed mortality over a period of 21 days. The relationship between survivorship and injury presence, sex, maturity, weight, season of capture, air temperature, water depth, and pot soak time were examined using generalized linear models. In addition, the relationship between injury presence and the same parameters were examined. Survivorship ranged from 77.8% to 93.6% during each of three fishing seasons and was significantly related to injury presence. Injury presence ranged from 10.0% to 63.2% during each season and was related to season with an increase in injuries during the fall. These data indicate the conservative assumption of 100% bycatch mortality for octopus is not appropriate for some fisheries, in particular those utilizing pot gear. [ABSTRACT FROM AUTHOR]

Octopus growth and movement occurs during all life stages and have implications for survival, food web dynamics and reproduction. From 2009 to 2011, 1714 North Pacific giant octopus (Enteroctopus dofleini) were tagged and recaptured in the eastern Bering Sea with visible implant elastomers to better understand the ecology of this data-poor species. Over this period, 246 of the tagged individuals were recaptured. In autumn, when temperatures were warmest,E. dofleinihad higher growth rates and moved more than in the colder winter months. For both short- and long-term recaptures, small octopus grew faster than large octopus. Movement of octopus over short- and long-term periods was low for very small and very large octopus and high for median-sized octopus, which is likely to be a function of maturity status and reproductive activities. Approximately 80% of recaptures moved less than 2 km from the initial tagging location for time periods up to a year, suggesting long-term site fidelity. As temperature and size may be tightly linked to growth and movement rates forE. dofleiniin the eastern Bering Sea, predicted climate warming will likely alter ecological processes for the species and impact their distribution. [ABSTRACT FROM AUTHOR]

Octopus are caught incidentally in several US federally-managed trawl, longline, and pot fisheries in Alaska. The majority caught are giant Pacific octopus Enteroctopus dofleini . Recent changes in fisheries management in Alaska have resulted in the creation of an octopus species complex with annual catch limits, leading to increased interest in management and catch accounting for this data-poor assemblage. This study characterized the incidental octopus catch in Alaska groundfish fisheries and the mortality rate of octopus caught and discarded at sea. Onboard fisheries observers collected data on octopus weight, sex, and condition at discard in a variety of Alaska groundfish fisheries from 2006 to 2011. A field study aboard a commercial pot-fishing vessel examined delayed mortality resulting from the capture process in giant Pacific octopus during routine pot fishing. Octopus incidental catch varied widely in size and condition at capture for various fishing gear types. Vessels fishing using pot gear captured larger octopus than vessels using longline or trawl gear. Initial condition at capture was best in pot gear, with over 90% of octopus discarded from pot vessels alive in excellent condition. Octopus taken in trawl gear had the highest immediate mortality rate, with 68–94% dead or injured at discard. Giant Pacific octopus held for 24–60 h following pot capture showed no signs of delayed mortality or decline in condition. These results suggest that assuming 100% mortality of discarded octopus may overestimate fishing impacts. [ABSTRACT FROM AUTHOR]

The giant Pacific octopus ( Enteroctopus dofleini) is a popular exhibit species in public display aquaria, but information on health and disease is limited. This retrospective review evaluates time in collection and describes antemortem clinical signs and pathology of giant Pacific octopuses in an aquarium setting. Between March 2004 and December 2013, there were 19 mortalities: eight males, 10 females, and one individual whose sex was not recorded. Average time spent in collection for all octopuses was 375 ± 173 days (males 351 ± 148 days, females 410 ± 196 days). Ten (52.6%) of the octopuses were sexually mature at the time of death, six (31.6%) were not sexually mature, and reproductive status could not be determined in three octopuses (15.8%). Minimal changes were noted on gross necropsy but branchitis was histologically evident in 14 octopuses, often in conjunction with amoeboid or flagellate parasites. Senescence, parasitism, and husbandry were all important contributors to mortality and should be considered when caring for captive octopuses. [ABSTRACT FROM AUTHOR]

Abstract: Visible Implant Elastomer (VIE) tags represent a viable approach for long-term tracking of North Pacific giant octopus (Enteroctopus dofleini) in Alaska. Over a two year period, 1730 E. dofleini were tagged with individually identifiable VIE tags and 238 E. dofleini were recaptured in a 25km2 area. Of the 238 E. dofleini recaptured, 31 were at liberty for 60 days or more with a maximum time at liberty of 374 days. This study shows that long-term retention of VIE tags may prove to be a vital tool in determining important life-history information for octopus species. [Copyright &y& Elsevier]

Multiple species of large octopus are known from the north Pacific waters around Japan, however only one large species is known in the Gulf of Alaska (the giant Pacific octopus, Enteroctopus dofleini). Current taxonomy of E. dofleini is based on geographic and morphological characteristics, although with advances in genetic technology that is changing. Here, we used two mitochondrial genes (cytochrome b and cytochrome oxidase I), three nuclear genes (rhodopsin, octopine dehydrogenase, and paired-box 6), and 18 microsatellite loci for phylogeographic and phylogenetic analyses of octopuses collected from across southcentral and the eastern Aleutian Islands (Dutch Harbor), Alaska. Our results suggest the presence of a cryptic Enteroctopus species that is allied to, but distinguished from E. dofleini in Prince William Sound, Alaska. Existence of an undescribed and previously unrecognized taxon raises important questions about the taxonomy of octopus in southcentral Alaska waters. [ABSTRACT FROM AUTHOR]

We isolated and developed 18 novel microsatellite markers for the giant Pacific octopus ( Enteroctopus dofleini) and examined them for 31 individuals from Prince William Sound (PWS), Alaska. These loci displayed moderate levels of allelic diversity (averaging 11 alleles per locus) and heterozygosity (averaging 65%). Seven loci deviated from Hardy-Weinberg Equilibrium (HWE) due to heterozygote deficiency for the PWS population, although deviations were not observed for all these loci in other populations, suggesting the PWS population is not in mutation-drift equilibrium. These novel microsatellite loci yielded sufficient genetic diversity for potential use in population genetics, individual identification, and parentage studies. [ABSTRACT FROM AUTHOR]

Abstract. Habitat characteristics associated with the giant Pacific octopus, Enteroctopus dofleini (Wülker 1910), were studied in Prince William Sound and Port Graham, Alaska, from beach walk, SCUBA and submersible surveys at depths of 0 to 197 m. Octopus counts on beach walk transects were positively correlated with soft substrates (sand, gravel or broken rubble), the presence of boulders, and dense kelp cover immediately offshore of the transect; and negatively correlated with depth on SCUBA transects. No significant habitat correlations were found with counts on submersible transects. On beach walks, octopus counts were reduced on hard substrates to 38 % of the counts on soft substrates. Counts increased five-fold in the presence of boulders over counts in their absence, and increased fifteen-fold adjacent to dense (> 75 %) kelp cover over counts adjacent to sparse (< 25 %) kelp cover. On SCUBA transects, the average density at less than 5 m depth was over five times that below 5 m. No trends in octopus size or sex ratio were detected with depth. Den use was inversely correlated with depth although there was no indication that den availability declined with depth. Octopuses were found at densities from 0 to 2.5 per 1000 m 2 . These densities were only 1 to 50 % of densities of the same species recorded in British Columbia in the late 1970s and early 1980s. Few data are available to test recruitment, mortality, and habitat selection hypotheses that would account for differences between habitats. However, the presence of the highest octopus densities in intertidal and very shallow subtidal areas indicates the likely importance of near-shore, shallow-water habitats, and highlights the vulnerability of octopus populations to changes in these habitats. [ABSTRACT FROM AUTHOR]

Abstract: New opportunities for the export of food grade octopus have furthered interest in developing an actively managed directed fishery for North Pacific giant octopus Enteroctopus dofleini in Alaska state waters. Trawl, long-line, and pot fisheries already harvest over 230 metric tons of octopus as bycatch annually. Managed under the authority of commissioner''s permits, applications for directed harvest in most management regions have historically been rejected due to the lack of information on stock status. Our limited knowledge of octopus movement, age structure, and demography hamper the ability to successfully manage this potential fishery. Chief among these obstacles is the lack of abundance estimates on which to base harvest guidelines. While catch-per-unit-effort estimates can be made from bycatch data and used as a proxy of abundance, these estimates can often be inaccurate. Mark-recapture estimates can be more accurate, but can also be expensive and require an effective means of marking individuals. We compared two different tags in order to assess their effectiveness for use on octopuses. We tagged 97 octopuses with modified Peterson discs and visible implant elastomer tags in Kachemak Bay, Alaska. Three tagged octopuses were recaptured, making a statistically sound tag comparison difficult. Our data suggest that visible implant elastomer tags will be a more effective means of marking octopuses. [Copyright &y& Elsevier]

Five scuba divers observed a female Giant Pacific Octopus, Enteroctopus dofleini, (Wülker, 1910) using the webover technique of speculative hunting. [ABSTRACT FROM AUTHOR]