Bias associated with statolith-based methodologies for ageing squid; a comparative study on illex illecebrosus (Cephalopoda: Ommastrephidae)

González, Ángel F.; Dawe, Earl G.; Beck, P.; Perez, J. A.

doi:10.1016/s0022-0981(99)00136-7

Cited by 13 publications

(9 citation statements)

References 22 publications

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“…Age estimation error for a single reader may be attributable to differences in preparation methods (e.g., mounting, grinding), increment enumeration methods (e.g., type of viewer, viewing magnification, increment interpretation) or both factors. For I. illecebrosus statoliths, the use of image analysis resulted in a systematic bias by underestimating ages of young squid and overestimating ages of old squid compared to a light microscopy method (Gonzalez et al, 2000). The bias was attributed to differences in increment interpretation and resulted in a doubling of growth-rate estimates.…”

Section: Discussionmentioning

confidence: 99%

“…The bias was attributed to differences in increment interpretation and resulted in a doubling of growth-rate estimates. Gonzalez et al (2000) also suggested that increased growth rates for squid grouped by hatch month were an artifact of age estimation error, owing to methodological differences between statolith-based vs. gladius-based estimates. However, substantial variability in the precision of statolith-based age estimates may also occur when conducted by a single reader using exactly the same methodology.…”

Section: Discussionmentioning

confidence: 99%

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Population biology of northern shortfin squid (Illex illecebrosus) in the Northwest Atlantic Ocean and initial documentation of a spawning area

Hendrickson

2004

ICES Journal of Marine Science

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Growth, maturity, and age structure of the northern shortfin squid (Illex illecebrosus) population were characterized from samples collected during a stratified, random bottomtrawl survey conducted in May 2000. The survey was conducted on the continental shelf of the east coast of the US and utilized a commercial squid fishing vessel and standardized sampling protocols and gear. Statolith increment counts of 391 individuals, representing the full maturity spectrum from juveniles to mated females (34e250 mm), ranged in age from 69 to 215 d. Substantial variability in the precision of individual age estimates was encountered. The population consisted of a predominant winter cohort of maturing and mature squid (hatched during OctobereFebruary, with a peak in January) and a spring cohort of juveniles (hatched during February and March, with a peak in March). Recruitment patterns to northern and southern fishing grounds are discussed. The first evidence of a spawning area, located on the continental shelf in the Mid-Atlantic Bight, is presented. Growth in length and weight was best described by a Gompertz model and a power model, respectively. The age range of mated females (115e215 d) indicated a shorter lifespan than expected based on maturity and age information for Newfoundland squid. A latitudinal cline in female size-at-maturity was evident, whereby maturity stages of squid in the southern part of the survey area were more advanced than those in the northern part. Also, females from US waters reach maturity and spawn at smaller sizes and younger ages than females from Newfoundland waters. The results suggest that females from the Mid-Atlantic Bight may exhibit faster rates of growth and maturation, and possibly a shorter lifespan, than their Newfoundland counterparts.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Population biology of northern shortfin squid (Illex illecebrosus) in the Northwest Atlantic Ocean and initial documentation of a spawning area

Hendrickson

2004

ICES Journal of Marine Science

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“…Statolith increment analysis has been applied systematically in squid (Arkhipkin and Laptikhovsky, 1994;Jackson, 1994;González et al, 1996González et al, , 2000Rocha and Guerra, 1999) and cuttlefish (Raya et al, 1994;Bettencourt and Guerra 2001;Challier et al 2002), and it is currently considered a reliable and validated technique. Unfortunately, statoliths have failed to provide useful results for octopus owing to a lack of visible growth rings (Lombarte et al, 2006), and the search for techniques to age octopods based on hard structures has continued.…”

Section: Introductionmentioning

confidence: 99%

Age validation in common octopus Octopus vulgaris using stylet increment analysis

Hermosilla

Rocha

Fiorito

et al. 2010

ICES Journal of Marine Science

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Hermosilla, C. A., Rocha, F., Fiorito, G., González, Á. F., and Guerra, Á. 2010. Age validation in common octopus Octopus vulgaris using stylet increment analysis. – ICES Journal of Marine Science, 67: 1458–1463. Daily periodicity of growth increments in stylets was validated in wild-caught Octopus vulgaris maintained under controlled conditions. It was corroborated by staining the stylets either with oxytetracycline (OTC) or tetracycline (TC), and comparing the number of rings produced with the number of days elapsed. In all, 19 animals (10 males and 9 females; 680–1470 g body weight, BW) were injected with OTC in Vigo (mean 124 mg kg−1), and another six animals (1 male and 5 females; 248–570 g BW) with TC at Naples (mean 120 mg kg−1). The animals were successfully maintained in captivity until sacrificed for up to 6 (one animal), 9 (one animal), 18 (the six animals from Naples), and 21 (17 animals) days. The number of increments counted in transverse stylet sections was 18.9 ± 1.4 and 20.5 ± 1.5 for octopuses maintained for 18 and 21 d, respectively. The mean rate of increment formation was 1.02 increments per day, suggesting a periodicity of 1 increment per day in the stylet. Consequently, the results successfully validate daily increment deposition in O. vulgaris stylets in the size range analysed.

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“…The ageing error associated with counting the daily increments deposited in statoliths has been documented for several cephalopod species (Gonzalez et al, 1998;Jackson and Moltschaniwskyj, 1999;Gonzalez et al, 2000), including I. illecebrosus (Hendrickson, 2004). In the maturation-natural mortality model, the fraction of non-mature squid in the cohort declines rapidly with age (Fig.…”

Section: Discussionmentioning

confidence: 98%

An age-based cohort model for estimating the spawning mortality of semelparous cephalopods with an application to per-recruit calculations for the northern shortfin squid, Illex illecebrosus

Hendrickson

Hart

2006

Fisheries Research

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Bias associated with statolith-based methodologies for ageing squid; a comparative study on illex illecebrosus (Cephalopoda: Ommastrephidae)

Cited by 13 publications

References 22 publications

Population biology of northern shortfin squid (Illex illecebrosus) in the Northwest Atlantic Ocean and initial documentation of a spawning area

Population biology of northern shortfin squid (Illex illecebrosus) in the Northwest Atlantic Ocean and initial documentation of a spawning area

Age validation in common octopus Octopus vulgaris using stylet increment analysis

An age-based cohort model for estimating the spawning mortality of semelparous cephalopods with an application to per-recruit calculations for the northern shortfin squid, Illex illecebrosus

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