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A comparison of tagging methodology for North Pacific giant octopus Enteroctopus dofleini

Authors:
Patrick D. Barry at University of Alaska Fairbanks
Patrick D. Barry
Sherry L Tamone at University of Alaska System
Sherry L Tamone
David A Tallmon at University of Alaska Southeast
David A Tallmon
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Abstract and Figures

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.
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Fisheries Research 109 (2011) 370–372
Contents lists available at ScienceDirect
Fisheries Research
journal homepage: www.elsevier.com/locate/fishres
Short communication
A comparison of tagging methodology for North Pacific giant octopus
Enteroctopus dofleini
Patrick D. Barrya,∗, Sherry L. Tamonea,b, David A. Tallmona,b
aSchool of Fisheries and Ocean Sciences, University of Alaska Fairbanks, 17101 Point Lena Loop Rd, Juneau, AK 99801, USA
bDepartment of Biology, University of Alaska Southeast, 11120 Glacier Hwy., Juneau, AK 99801, USA
article info
Article history:
Received 11 June 2010
Received in revised form 18 February 2011
Accepted 18 February 2011
Keywords:
Enteroctopus dofleini
Tagging
Mark-recapture
Peterson disc
Visible implant elastomer
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 annu-
ally. 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 esti-
mates 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 dif-
ficult. Our data suggest that visible implant elastomer tags will be a more effective means of marking
octopuses.
© 2011 Elsevier B.V. All rights reserved.
1. Introduction
External tags have been used to study animal behavior, move-
ment and migration, and to provide information on age, growth,
mortality, and abundance (McFarlane et al., 1990). Growing inter-
est in an actively managed directed fishery for North Pacific
giant octopus (Enteroctopus dofleini) has raised both manage-
ment and ecological questions, including those concerned with
octopus movement patterns and abundances. While early tag-
ging studies looked at residence times (Hartwick et al., 1984;
Mather et al., 1985), little is known about large-scale dispersal or
abundance.
A variety of chemical (Ikeda et al., 1999, 2003), electronic
(Anderson and Babcock, 1999; Mather et al., 1985; Scheel et al.,
2007), external (Hartwick et al., 1984; Nagasawa et al., 1991;
Robinson and Hartwick, 1986) and tattooing/branding (Nagasawa
et al., 1991; Replinger and Wood, 2007) tags have been used to
study cephalopods. External tags such as Atkins and Petersen tags
are the most commonly used tag to study E. dofleini (Hartwick et al.,
1984; Nagasawa et al., 1991; Robinson and Hartwick, 1986). Cos-
∗Corresponding author. Tel.: +1 907 796 6034; fax: +1 907 796 6447.
E-mail address: patdbarry@gmail.com (P.D. Barry).
grove (Royal British Columbia Museum, pers. comm.) investigated
the use of numbered plastic discs secured through the mantle with
a plastic cable tie, but octopuses ripped those out leaving large
wounds in the mantle. Tattoo and branding, particularly visible
implant elastomer tags (VIE; Northwest Marine Technology, Shaw,
Washington) have been used successfully on the squid Sepioteuthis
sepioidea to investigate growth rates (Replinger and Wood, 2007).
However, when used on the cuttlefish Sepia (Mesembrisepia) lati-
manus this method (injecting latex between skin and cuttlebone)
led to significant wounds and mortalities (Nagasawa et al., 1991)
suggesting that its usefulness may be limited to animals of a certain
size.
While Peterson tags are the most commonly used tag, the extent
to which they affect animals is debated. Robinson and Hartwick
(1986) observed no ulcerations around tags and octopuses did not
seem to be adversely affected by tagging. Domain et al. (2000) com-
pared spaghetti and Petersen disc tags for use on Octopus vulgaris,
and determined that Petersen disc tags stayed on longer. How-
ever, the authors did not attribute observed tag loss to necrosis
of surrounding tissue or manipulation of the tag by octopuses. In
either case visible implant elastomer (VIE) tags may decrease tag
loss and provide a more effective and efficient means of mark-
ing. The goal of this study is to compare two different marking
techniques.
0165-7836/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.fishres.2011.02.011
P.D. Barry et al. / Fisheries Research 109 (2011) 370–372 371
Fig. 1. Giant Pacific octopuses (Enteroctopus dofleini) were tagged using two differ-
ent marks: Petersen disc tags and visible implant elastomer (VIE) tags. This photo
shows the location of both tags on the ventral side of the mantle. Arrows indicate
where each VIE dye was injected. Injected as a liquid, the elastomer forms a pliable
biocompatible solid. The Peterson discs were inserted through the opening in the
mantle on the ventral surface by puncturing the mantle with the two plastic screws,
and securing a plate with two plastic nuts.
2. Materials and methods
We caught E. dofleini during three surveys (29 May to 18 June
2006, 2–13 October 2006, and 25 November to 6 December 2006)
in Kachemak Bay, Alaska. Unbaited lair pots and three baited pots
(Korean hair crab pots, both commercial and personal use Ladner
shrimp pots, and black cod pots) were used.
Upon capture, we sexed animals and recorded morphometric
measurements including the interocular distance (IOD), mantle
length (ML), and weight, as well as any identifying marks. Before
tagging, each octopus was transferred to water cooled to approxi-
mately 1 ◦C to anesthetize them.
Due to the difficulty in tagging larger octopuses (>11 kg [kilo-
grams]) with the Petersen discs, and to minimize the effect of
handling time on the health of each animal when many octopuses
were caught in a string of pots, 28 octopuses were tagged using
only the VIE tags. Modified Petersen discs were inserted through the
ventral side of the mantle, secured with plastic nuts, and the excess
screw length cut flat using scissors (Fig. 1). We injected the VIE tag
subcutaneously on the ventral side of the mantle where the pig-
mentation is lightest (Fig. 1). Each elastomer tag consisted of four
injected dye spots, occupied by any of four colors (red, orange, yel-
low and/or green) to individually identify each animal. Tags were
injected using a tuberculin syringe fitted with a 20-gauge needle.
We released tagged octopuses within 10 m of the GPS coordinates
at which they were captured. During the third survey, animals were
not tagged with either Petersen or VIE tags.
3. Results
During the first and second surveys 3 and 94 E. dofleini were
tagged respectively using Petersen discs and VIE tags to allow
for their direct comparison. Of the three recaptures, two animals
were marked with both tags while the other had only the VIE tag
(Table 1). We observed from one individual that the Petersen discs
can irritate the tissue surrounding the tag resulting in necrosis
(Fig. 2). Of the two individuals recaptured that were initially tagged
with both methods, one had lost its Petersen tag while all retained
the VIE tag. Upon examination of the VIE tags no noticeable tis-
sue damage was caused at the site of injection. None of the colors
became dull or difficult to distinguish, and there was no noticeable
difference in size of the marks between mark and recapture.
4. Discussion
Our results indicate that VIE tags may be a more reliable tagging
method than the commonly used Petersen tag and that animals
may exhibit a strong trap response. While our results have impli-
cations for tagging studies for studying growth, movement, and
survival, we focus here on the implementation of mark-recapture
on estimates of abundance.
Results of recaptures suggest that VIE tags may provide a more
durable method of marking octopuses than Petersen tags. Petersen
tags were obvious upon recapture and were easily felt and seen
when handling recaptured octopuses, but led to significant tissue
damage in two individuals which may lead to tag loss. Because
they are external tags, octopus may be able to remove the plastic
nuts which secure both plates in the mantle. The VIE tags led to no
signs of irritation, but are not immediately obvious upon recapture
without manipulation of the posterior mantle. Also, consecutively
injected elastomer colors can be embedded in the epidermis such
that the colored dots move with respect to each other when the
mantle tissue is manipulated and this may lead to the misidentifi-
cation of recaptures. Of the three recaptures, the one individual that
had lost the Petersen tag showed significant tissue damage around
the site where the tag had been inserted. Although brown trout
have been observed to absorb the VIE during growth or for layers
of musculature or epidermis to cover the tag (Olsen and Vollestad,
2001), we would still be able to identify octopuses in this study by
their Petersen tag. Consequently, low recapture rates in the third
survey are not likely due to tag loss.
Materials used in the construction of the Peterson disc tags as
well as the part of the body tagged may determine the extent to
which wounds develop. Robinson and Hartwick (1986),Domain
et al. (2000), and Cosgrove (pers. comm.) used Peterson disc tags
secured by nickel pins to the base of the left third. The smaller
diameter of the nickel pin may cause less irritation to surround tis-
sue than the plastic screws with which we constructed our tags.
Tagging at the base of the left third arm where muscle is the thick-
Table 1
Summary statistics from three recaptured North Pacific giant octopuses in Kachemak Bay, AK. Upon capture we recorded sex, weight, inner ocular distance (IOD), and mantel
length (ML).
Animal ID Sex Weight gained (kg) Change in IOD (cm) Change in ML (cm) Distance moved (km) Days between captures
Peterson VIE
85 OOYY F 1.5 0 0 7.53 52
N/A GRRY F 4.5 1.5 2.5 5.31 48
118 RRGG M 1.25 2.5 2 1.44 63
Avg 2.42 1.33 1.33 4.76 54.33
372 P.D. Barry et al. / Fisheries Research 109 (2011) 370–372
Fig. 2. Piercing the mantle of the North Pacific giant octopus (Enteroctopus dofleini) may cause significant wounds and result in necrosis and tag loss. Left: This photo shows
part of the ventral mantle where the tag has been successfully inserted immediately after application of the mark. Tissue was healthy and the tag was clearly visible. Right:
This photo shows the ventral side of the mantle where a Petersen tag was beginning to cause necrosis after approximately 54 days.
est may extend the time for which it takes the tissue to reject the
tag. While no tissue damage was observed in these three stud-
ies, animals were not double marked and tag retention was not
estimated.
Acknowledgements
We are grateful to those who helped in collecting data including
D. Scheel, J. Grund, D. Veerhusen and the crew of the F/V Shady
Lady, G. Carroll and the crew of the F/V Centurion and J. Browning.
This research was supported by a grant from the Alaska Fishery
Development Foundation.
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This project has two main components; (i) aquaculture, i.e. to culture and release larval/juvenile crabs, without the use of live microalgae and (ii) experimental, i.e. to conduct staining/tagging trials and hatchery survival experiments. During this milestone period 36,000 late stage megalopae were cultured from the 1,420,000 zoea produced by four late stage berried females collected in the wild and induced to release their eggs in a single hatchery run undertaken at Australian Centre for Applied Aquaculture Research (ACAAR) in November 2017. Larvae were reared exclusively on Reed Shellfish diet, rotifers and Artemia. Survival remained relatively high (37%) right up until the last day of megalopae, when a large mortality event occurred prior to moulting into crablets. Surviving megalopae were harvested and counted and survival was determined to be around 6%. A total of 23,000 of these megalopae were released into the cooling water intake pond at the disused South Fremantle Power Station, 5,000 were kept for crablet tank trials at Murdoch University and 8,000 were kept at ACAAR for on growing and were later released into an inland aquaculture facility to assess the feasibility for their survival in a nursery/growout environment. The experimental component of this project set out to: (i) test the utility of a chemical stain (Alizarin Complexone) and physical tag (Visible Implant Elastomer) to denote hatchery-reared individuals, so that any crablets released into the wild could be identified; (ii) determine the survival of hatchery-reared crablets in a range of different habitats; and (iii) compare the survival of hatchery-reared megalopae and crablets in the wild to determine which size-at-release provides the best survival rates. Staining crabs with Alizarin Complexone proved unsuccessful as the stain was not detected following mounting in resin and sectioning or dissection. However, Visible Implant Elastomer tags implanted in large crablets and adults were clearly seen under both normal and UV light. A 25 day tank trial in five different habtats types including four types of habitat enrichment (i.e. sand, pebbles, artificial turf and BIO-BLOK) and a control (bare tank) showed that increasing habitat complexity may help reduce cannibalism, but that substantial cannibalism will still occur. 6 The third experiment involved release of megalopae and crablets into a cooling water intake pond for a disused power station south of Fremantle. Following the successful acquisition of a number of approvals, a water exchange occurred to increase salinity and 23,000 megalopae were released and weekly monitoring was carried out after stocking. No crabs were caught during this sampling, indicating that those megalopae died, possibly due to the input of low salinity ground water. Rather than expose remaining 623 crablets to this unfavourable environment, they were all transported from the ACAAR hatchery in Fremantle to an inland saline aquaculture facility ~400 km north-east of Perth in Morawa. These crablets grew rapidly, i.e. from between 20-30 mm carapace width on January 12 to between 40-70 mm carapace width six weeks later, and some were still alive as of July 2018. Unfortunately, as the transfer resulted in the crabs being located at a commercial aquaculture facility six hours away and thus regular monitoring was not able to be maintained. Due to the lack of survival of the megalopae and thus the transfer of the crablets to a different environment no comparison of the trade-off of releasing larger numbers of megalopae vs smaller numbers of crablets were able to be undertaken. Given the results of the current study and the hatchery capacity in Perth it seems likely that any substantial culture effort would either (i) release at the megalopae size (and thus at the point when cannibalism starts), which, in aquaculture-based enhancement projects for other crab species has not proven to be successful or (ii) utilise an outdoor nursery/grow out environment, such as earthen ponds used in inland saline aquaculture, enriched with appropriate vertical habitat, for a period of time sufficient to allow growth to a large size before release, without becoming maladapted to the wild.
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... The effort to increase the canon of field data will be aided by the pace of technological development and decreasing costs of data acquisition tools. Various types of tagging have been utilized successfully in recent years to answer questions about geographic range, migration and diving habits (Fuentes et al., 2006;Gilly et al., 2006;Replinger and Wood, 2007;Bazzino et al., 2010;Barry et al., 2011;Sims et al., 2011;Wearmouth et al., 2013;Sykes et al., 2017b). Remote monitoring through videography and photography is another increasingly accessible option thanks to the profusion of low-cost cameras that have come on the market in recent years. ...
The Current State of Cephalopod Science and Perspectives on the Most Critical Challenges Ahead From Three Early-Career Researchers
Article
Full-text available
  • Jun 2018
Here, three researchers who have recently embarked on careers in cephalopod biology discuss the current state of the field and offer their hopes for the future. Seven major topics are explored: genetics, aquaculture, climate change, welfare, behavior, cognition, and neurobiology. Recent developments in each of these fields are reviewed and the potential of emerging technologies to address specific gaps in knowledge about cephalopods are discussed. Throughout, the authors highlight specific challenges that merit particular focus in the near-term. This review and prospectus is also intended to suggest some concrete near-term goals to cephalopod researchers and inspire those working outside the field to consider the revelatory potential of these remarkable creatures.
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... In addition, the use of new technologies will aid in providing additional information on movement, mortality, and biomass. The development of new tagging technologies (Barry et al., 2011;Brewer and Norcross, 2012) and the examination of short and long term movement (Scheel and Bisson, 2012) with acoustic studies have begun to provide answers on the short and long term migratory movements of these animals. In addition, these studies have started to examine biomass and mortality of giant Pacific octopus as well. ...
Delayed discard mortality of the giant Pacific octopus, Enteroctopus dofleini , in the Gulf of Alaska cod pot fishery
Article
Full-text available
  • Jan 2018
  • FISH RES
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.
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... Body weight may not be a sufficiently sensitive welfare indicator for daily assessment, although it may be useful over longer intervals. However, for species housed in groups reliable identification of individuals is required, and several methods are described for cephalopods (e.g., Huffard et al., 2008;Ikeda et al., 2009;Zeeh and Wood, 2009;Byrne et al., 2010;Barry et al., 2011;Estefanell et al., 2011;Sykes et al., 2017). ...
The Digestive Tract of Cephalopods: Toward Non-invasive In vivo Monitoring of Its Physiology
Article
Full-text available
  • Jun 2017
Ensuring the health and welfare of animals in research is paramount, and the normal functioning of the digestive tract is essential for both. Here we critically assess non- or minimally-invasive techniques which may be used to assess a cephalopod's digestive tract functionality to inform health monitoring. We focus on: (i) predatory response as an indication of appetitive drive; (ii) body weight assessment and interpretation of deviations (e.g., digestive gland weight loss is disproportionate to body weight loss in starvation); (iii) oro-anal transit time requiring novel, standardized techniques to facilitate comparative studies of species and diets; (iv) defecation frequency and analysis of fecal color (diet dependent) and composition (parasites, biomarkers, and cytology); (v) digestive tract endoscopy, but passage of the esophagus through the brain is a technical challenge; (vi) high resolution ultrasound that offers the possibility of imaging the morphology of the digestive tract (e.g., food distribution, indigestible residues, obstruction) and recording contractile activity; (vii) needle biopsy (with ultrasound guidance) as a technique for investigating digestive gland biochemistry and pathology without the death of the animal. These techniques will inform the development of physiologically based assessments of health and the impact of experimental procedures. Although intended for use in the laboratory they are equally applicable to cephalopods in public display and aquaculture.
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Evaluation of visible implants elastomer tags in juveniles of red octopus Octopus maya: Evaluación de implantes visibles de elastómero en juveniles de pulpo rojo Octopus maya
Article
Full-text available
  • Apr 2022
In this work, the effects of visible implant elastomer (VIE) tags on survival and body growth rate on juvenile red octopus Octopus maya from the Yucatan Peninsula were tested under controlled conditions. Juveniles with an average weight of 1.14 g were not affected by VIE within 30 days, so this methodology is suggested as a useful tool to study the life cycle aspects of this important fishery species.
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Cephalopod tagging and marking in Japan: a review
Chapter
Full-text available
  • Jan 1993
Tagging and marking experiments of cephalopods conducted in waters around Japan are reviewed. This review is based on widely scattered information published during the period 1927-1990 mainly from both scientific literature and annual reports of national and prefectural government fisheries institutions. So far a total of 14 species (3 cuttlefishes, 7 squids, and 4 octopods) have been tagged or marked and released in Japanese waters chiefly to study their migratory and distributional patterns. In particular, Japanese common squid (Todarodes pacificus) has been studied and over 930,000 animals have been tagged and released during 1927-1989. This review outlines tagging or marking studies in each of the 14 cephalopod species and compiles information on methods of tagging and marking for Japanese cephalopods. It also summarizes general knowledge from tag-recapture surveys of Japanese common squid.
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Subcutaneous electromagnetic tagging of benthic octopus: a preliminary evaluation
Article
Full-text available
  • Mar 1999
Electromagnetic tags were subcutaneously implanted in the dorsal crown of 28 octopus (20 aquarium tagged; and 8 wild octopus tagged in situ) from two species: Octopus tetricus and O. maorum. Laboratory tagged octopus retained tags for the duration of the study (14 months), as did octopus tagged in the wild (13 weeks). No signs of lesions, physical deterioration, or abnormal behaviours were apparent in either laboratory or field tagged octopus. Tagging had no significant effect on growth trajectories. Both laboratory and field tagged octopus appeared healthy, physically vigorous, maintained voracious apetites, and regularly stalked and attacked vigorous prey (laboratory observations only). Subcutaneously implanted electromagnetic tags enabled individuals to be tagged, and tags to be read in situ with minimal disturbance to the animal. Electromagnetic tagging is a potentially invaluable tool in studying benthic octopus and may have similar value in the study of many cephalopods and other soft bodied organisms.
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Activity and movement patterns of Octopus dofleini
Article
Full-text available
  • Jul 1985
  • Mar Behav Physiol
Four individual Octopus dofleini were followed over a fifteen day period in their underwater habitat by sonic tracking. Octopuses had small home ranges (250 mmaximum) which were stable over the two weeks of observation. These ranges overlapped those of other octopuses extensively, and animals did not keep a constant distance from one another, which suggests they were solitary and non‐social. Activity was slightly higher at night, and was not correlated with changes in other environmental variables. The O. dofleini made frequent short hunting trips (mode 0.5 hours), tending to have more and longer excursions at night. Octopuses are predators who appear to have flexible activity and, in the short term, restricted home range areas.
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Strontium:calcium ratios in statoliths of Japanese common squid Todarodes pacificus (Cephalopoda: Ommastrephidae) as indicators of migratory behavior
Article
Full-text available
  • Apr 2003
Ontogenetic variation in the strontium: calcium (Sr:Ca) ratios was measured in statoliths of the Japanese common squid Todarodes pacificus. Two different geographical groups of T pacificus inhabit the Sea of Japan; these groups are separated by the Subarctic Front during the summer. Element ratios were measured with a wavelength-dispersive spectrometer for 11 individuals from a cold-water subarctic region, which harbors large squid (Subarctic Group), for 12 individuals from a warm-water region, which harbors smaller squid (Tsushima Group), and for 2 individuals from the Subarctic Front. The squid ranged from 190 to 218 mm in mantle length (ML) and were 191 to 262 d old. Similar measurements were obtained for 12 tagged T. pacificus (187 to 259 mm. ML; 214 to 312 d old) that were released and recovered in the Subarctic and the Tsushima Current between June and August 1997 (tagging duration 5 to >40 d). Ontogenetic variation in Sr:Ca ratios from hatchlings to sub-adults differed between the 2 geographical groups. Sr:Ca ratios were high at hatching followed by a drastic decrease up to 10 d of age for both groups. These ratios increased until 40 d of age, continuing at high levels until around 150 d, when they decreased in all specimens of the Tsushima Group. In the Subarctic Group, however, the variations in Sr:Ca ratios differed between individuals. Sr:Ca ratios at the age when squid recruited to either the Subarctic or the Tsushima Current were similar. These differences reflect the different spawning grounds and transport routes of the 2 groups. Thermal history was recorded from the statoliths of tagged individuals, and small fluctuations and seasonal variations in the Sr:Ca ratios were observed. These correspond to diel vertical movements and endogenous rhythms of the squid, and the formation and movements of the cold-water layer in their habitat.
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Den utilization and the movements of tagged Octopus dofleini
Article
Full-text available
  • Aug 1984
  • Mar Behav Physiol
Individual Octopus dofleini in a shallow‐water population in British Columbia, Canada, were tagged and their movements monitored at biweekly intervals for one year. Octopuses moved into the study areas throughout the year and stayed up to 6.5 months (mean = 57 days). Immigration rates were highest in July/August and November/December. Most octopuses occupied the same shelter for at least one month. Octopuses that changed dens within the study area moved an average of 13.2 m. More than one‐fourth of the octopuses were absent for more than a month, then recaptured at the same site. Monthly departure rates were extremely variable, and could not be distinguished from random. These data indicate a pattern of large‐scale movement interspersed with periods of residence in a relatively small area; evidence for seasonal migrations in this population are also evaluated.
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An Evaluation of Visible Implant Elastomer for Marking Age-0 Brown Trout
Article
Full-text available
  • Nov 2001
  • N AM J FISH MANAGE
Injection of visible implant elastomer (VIE) was evaluated as a way to provide age-0 brown trout Salmo trutta with externally visible internal marks. We first tested this fluorescent elastomer material in a laboratory experiment using a single color and body position to batch-mark the fish (28.9–44.1 mm fork length). The experiment lasted for 77 d, with no mortality or tag loss and no significant (P = 0.44) effect on fish growth. Similar marks were then used to individually tag age-0 brown trout (26–70 mm) in small streams in the wild using four different colors and several body positions. The immediate mortality associated with the marking procedure was low (0.5%), and visual identification of VIE marks on recaptured individuals (169 out of 699 released; 39–83 d between release and recapture) was not difficult. We found no significant differences in mean fork length between tagged and untagged individuals captured on the same date at given sampling locations. This suggests that capture and marking had no major negative effect on fish growth (assuming that tagged and untagged individuals experienced similar conditions between sampling occasions and otherwise had comparable histories).
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Cephalopods Present and Past: New Insights and Fresh Perspectives
Book
  • Jan 2007
Cephalopods are diverse, highly developed molluscs capable of swimming and jet propulsion. These animals are an important component of present-day marine ecos- tems throughout the world and comprise approximately 900 species. They also have an extraordinary fossil record, extending back to the Cambrian Period, with as many as 10,000 extinct species. Throughout their long history, they have experienced sp- tacular radiations and near-total extinctions. Because of their superb fossil record, they also serve as ideal index fossils to subdivide geologic time. This book touches on many of these themes, and it treats both fossil and present-day cephalopods. The chapters are outgrowths of presentations at the Sixth International Symposium “Cephalopods – Present and Past,” at the University of Arkansas in Fayetteville, September 16–19, 2004. The Symposium was organized principally by Walter L. Manger of the Department of Geology, University of Arkansas. The editors gratefully acknowledge Walter for his terrific job in putting together this symposium and for making it such an intellectual, and social, success. Other publications related to this Symposium include the abstract volume, assembled by W. L. Manger, and two fie- trip guidebooks, one written by W. L. Manger, and the other by R. H. Mapes. Because this symposium was held in North America, it honored four cephalopod workers from this continent: William A. Cobban (US Geological Survey, Denver, Colorado), Brian F. Glenister (University of Iowa, Iowa City, Iowa), William M. Furnish (University of Iowa, Iowa City, Iowa), and Gerd E. G.
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Analysis of growth based on tag-recapture of the Giant Pacific octopus Octopus dofleini martini
Article
  • Aug 1986
In total, 211 octopuses were tagged and 87 (41·2%) of these were recaptured, some up to eight times for a total of 184 recaptures. Octopuses ranged in wet weight from 1·6 to 20 kg and the sex ratio was skewed towards females. No difference was found in the growth rates between sexes or locations and growth rates were variable for all sizes studied. Evidence for two distinct growth periods was found; a slow period from January to June and a faster period from July to December. Separate growth curves were drawn for each period and their relevance to potential growth in the field discussed. Growth rates of O. dofleini were comparable to those described for other octopod species. A tag-recapture growth study of Octopus dofleini martini was conducted at two inshore, shallow water (2–15 m) sites in Clayoquot Sound, British Columbia. The objective was to describe the growth of O. dofleini in the field and investigate variation related to sex, season or location.
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