Introducing inter-individual growth variability in the assessment of a cephalopod population: application to the English Channel squid Loligo forbesi

Challier, Laurencei; Orr, Pia; Robin, Jean-Paul

doi:10.1007/s00442-006-0497-x

Cited by 9 publications

(4 citation statements)

References 49 publications

(66 reference statements)

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“…Individual variability in growth has been observed in many taxa, including cephalopods (Domain et al 2000), gastropods (Hughes & Roberts 1980) and teleosts (Searcy & Sponaugle 2000), resulting in intraspecific size-at-age data often being highly variable (Challier et al 2006). Under these conditions, understanding population dynamics and changes in population size structure becomes challenging (Gurney & Veitch 2007), especially for exploited species.…”

Section: Introductionmentioning

confidence: 99%

Modelling size-at-age in wild immature female octopus: a bioenergetics approach

André¹,

Pecl²,

Grist³

et al. 2009

Mar. Ecol. Prog. Ser.

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The population dynamics of cephalopods are poorly understood because intra-specific size-at-age is characteristically variable. Much of the variation observed is attributed to temperature and food, but other generally overlooked factors such as hatchling size and inherent growth capacities also affect size-at-age. In the present paper, we investigated the relative influence of the principal abiotic (environmental temperature) and biotic (food consumption, hatchling size, inherent growth capacity) factors affecting size-at-age in immature octopus. Using a bioenergetics model and size-at-age data of wild-caught immature Octopus pallidus, we simulated the juvenile growth trajectories of individuals hatched in different seasons (summer, autumn and winter) based on food availability, metabolism, environmental temperature and individual variability, under an assumption of 2-phase growth. Simulations predict that the effect of hatchling size on size-at-age was secondary to that of inherent growth capacity. Projections suggest that wild immature populations comprise a mixture of individuals displaying exponential growth and 2-phase growth and that the proportion of each depends primarily on the individuals' inherent growth capacities and food availability. High food intake was projected to decrease the number of individuals displaying 2-phase growth by delaying the transition between the 2 growth phases, resulting in larger individuals. Overall, individuals hatched in summer grew to larger sizes and matured earlier than individuals hatched in autumn or winter, independent of food availability. The size-at-age distribution of the summer and autumn cohorts tended to become bimodal under certain food intake levels, which highlights the importance of coupling size data with accurate age estimates in future octopus population studies. KEY WORDS: Early life history · Energy balance · Individual-based model · Pale octopusResale or republication not permitted without written consent of the publisher

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Section: Introductionmentioning

confidence: 99%

Modelling size-at-age in wild immature female octopus: a bioenergetics approach

André¹,

Pecl²,

Grist³

et al. 2009

Mar. Ecol. Prog. Ser.

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“…Some exercises with cohort analysis (Royer et al 2002;Challier et al 2006a) and depletion methods (Young et al 2004) have been conducted for loliginid squids, but for the most part, conventional models used in the assessment of fin fish stocks are not applicable (Pierce & Guerra 1994). Nevertheless, if stock size predictions are to partly rely on temperature data (Robin & Denis 1999;Pierce & Boyle 2003;Chen et al 2006), the understanding of age structure, growth, and its variability under fluctuating environmental conditions is of fundamental relevance.…”

Section: Introductionmentioning

confidence: 99%

Growth strategies in the squidLoligo vulgarisfrom Portuguese waters

Moreno

Azevedo

Pereira

et al. 2007

Marine Biology Research

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The growth of the European squid Loligo vulgaris in northwest Portuguese waters is described and the influences of gender and hatching season analysed, based on statolith readings from individuals of a wide range of sizes. Male and female growth follows different models, males attaining a higher length-at-age than females. Males display increasing growth rates irrespective of the hatching season, but the length-at-age is higher in animals hatched during the warm season. Females may exhibit asymptotic growth or not, depending upon the environmental conditions to which they are exposed through their life cycle. Although growth rates after hatching are lower in females hatched during the cold season, favourable feeding and temperature conditions during the following spring and summer months contribute not only to increase growth rates but also to delay sexual maturation. The higher length-at-age of squid hatching in the warm season, observed in both genders, provides evidence that the temperature close to hatching has a significant impact on the size of juveniles and subadults. However, there is also strong evidence that throughout their life, environmental conditions continue to play an important role in growth rates and in defining the shape of growth.

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“…However, it is worth noting that one constraint of this type of growth analysis is that without the availability of age data on the study samples, and because the smoothing graphs are composites of a collection of animals at different developmental points in the life cycle, it is impossible to follow the individual growth trajectories of single animals, and so inferences must be made from the population regarding growth processes (as has been done in previous research, e.g. Challier et al, 2006). As with previous results for male L. forbesii (and to a lesser extent, females) in Scotland and Spain Collins et al, 1999;Smith et al, 2005), for L. vulgaris from the Iberian Peninsula (Coelho et al, 1994; and Loligo reynaudii off South Africa (Hanlon et al, 2002;Olyott et al, 2006), the Dashed lines represent 95% confidence intervals around the main effects existence of two to three size-at-maturity categories within the animals sampled, each potentially having a characteristic gonad weight-body length relationship, would tend to give the appearance of a weaker positive relationship between the variables than exists within each group alone.…”

Section: Body Lengthmentioning

confidence: 99%

Patterns of investment in reproductive and somatic tissues in the loliginid squid Loligo forbesii and Loligo vulgaris in Iberian and Azorean waters

et al. 2011

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The veined squid, Loligo forbesii, is found throughout the northeast Atlantic, including the waters off the Iberian Peninsula, and is a socio-economically important cephalopod species, sustaining several small-scale commercial and local artisanal fisheries. This study uses Iberian and Azorean trawl survey and fishery landings data from 1990 to 1992 and employs additive modelling to examine the relationships amongst somatic growth, season and gonad growth, in an attempt to determine the relative importance of intrinsic (e.g. nutritional state and body size) and extrinsic (temperature and daylight) factors which contribute to maturation in L. forbesii. We compare the results with those from a comparative analysis of contemporaneous data on Loligo vulgaris from the Iberian coast, and with a re-analysis of previously published results for L. forbesii in Scottish waters. Reproductive organ weight in both sexes of L. forbesii from all ports shows seasonal patterns with a fall/winter peak in maturation, as is expected with the animals' year-long life cycle. Two maturity peaks (spring and winter) were found for both Azores L. forbesii males and females, possibly evidence of two breeding cohorts, with males maturing approximately 1 month earlier than females in both seasons. For L. vulgaris, three annual peaks in reproductive weight were identified. With the exception of L. forbesii males from Scottish waters, in all study animals, the partial effect of mantle length and mantle weight on reproductive weight is positive up to large body sizes. The relationship between nutritional status and reproductive weight is also generally positive. Geographic variation in the relationships, as seen between Scottish males and samples from the other study areas, is hypothesised to be largely attributable to local differences in environmental conditions (productivity, food availability, temperature, upwelling),

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Introducing inter-individual growth variability in the assessment of a cephalopod population: application to the English Channel squid Loligo forbesi

Cited by 9 publications

References 49 publications

Modelling size-at-age in wild immature female octopus: a bioenergetics approach

Modelling size-at-age in wild immature female octopus: a bioenergetics approach

Growth strategies in the squidLoligo vulgarisfrom Portuguese waters

Patterns of investment in reproductive and somatic tissues in the loliginid squid Loligo forbesii and Loligo vulgaris in Iberian and Azorean waters

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