Spawning aggregations of squid (Sepioteuthis australis) populations: a continuum of ‘microcohorts’

Spawning aggregations of squid (Sepioteuthis australis) populations: a continuum of... The aim of this study was to determine how size, age, somatic and reproductive condition, abundance and egg production of southern calamary spawning aggregations changed during the spawning season in each of 2 years. During the spawning period in at least one of the years there was a decline as much as 20% in average size, 50% in somatic condition, 28–34% in size-at-age, 26–29% in reproductive status, as well as abundance and reproductive output of the stock declining during the spawning season. However, this change was not a function of the population becoming reproductively exhausted, as the aggregation was composed of different individuals with different biological characteristics. In each month the average age of individuals was ca. 6 mo, indicating that squid that had hatched at different times had entered the spawning aggregations, suggesting that the aggregation was made-up of a succession of microcohorts. Currently, management of many squid populations assumes that there is a single cohort in the aggregation. Therefore, estimating stock biomass at the start of the spawning season cannot be used as the population is constantly changing as micro-cohorts move into the aggregation. An instantaneous estimate of the spawning biomass, independent of fishing activity may be obtained by quantifying the density of deposited eggs. The strategy of individuals with a diversity of life history characteristics coming together in a single spawning aggregation may ensure the phenotypic and genetic diversity required to guarantee successful recruitment of this short-lived species. Therefore, temporally structured protection from harvest throughout the spawning season will ensure maintenance of this population diversity. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Reviews in Fish Biology and Fisheries Springer Journals

Spawning aggregations of squid (Sepioteuthis australis) populations: a continuum of ‘microcohorts’

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Publisher
Kluwer Academic Publishers
Copyright
Copyright © 2006 by Springer Science+Business Media, Inc.
Subject
Life Sciences; Freshwater & Marine Ecology; Zoology
ISSN
0960-3166
eISSN
1573-5184
D.O.I.
10.1007/s11160-006-9025-7
Publisher site
See Article on Publisher Site

Abstract

The aim of this study was to determine how size, age, somatic and reproductive condition, abundance and egg production of southern calamary spawning aggregations changed during the spawning season in each of 2 years. During the spawning period in at least one of the years there was a decline as much as 20% in average size, 50% in somatic condition, 28–34% in size-at-age, 26–29% in reproductive status, as well as abundance and reproductive output of the stock declining during the spawning season. However, this change was not a function of the population becoming reproductively exhausted, as the aggregation was composed of different individuals with different biological characteristics. In each month the average age of individuals was ca. 6 mo, indicating that squid that had hatched at different times had entered the spawning aggregations, suggesting that the aggregation was made-up of a succession of microcohorts. Currently, management of many squid populations assumes that there is a single cohort in the aggregation. Therefore, estimating stock biomass at the start of the spawning season cannot be used as the population is constantly changing as micro-cohorts move into the aggregation. An instantaneous estimate of the spawning biomass, independent of fishing activity may be obtained by quantifying the density of deposited eggs. The strategy of individuals with a diversity of life history characteristics coming together in a single spawning aggregation may ensure the phenotypic and genetic diversity required to guarantee successful recruitment of this short-lived species. Therefore, temporally structured protection from harvest throughout the spawning season will ensure maintenance of this population diversity.

Journal

Reviews in Fish Biology and FisheriesSpringer Journals

Published: Dec 28, 2006

References

  • Flexible reproductive strategies in the squid Loligo forbesi
    Boyle, PR; Pierce, GJ; Hastie, LC
  • Multiple spawning in the tropical squid Photololigo sp.: what is the cost in somatic growth?
    Moltschaniwskyj, NA
  • Small-scale spatial and temporal patterns of egg production by the temperate loliginid squid Sepioteuthis australis
    Moltschaniwskyj, NA; Pecl, GT
  • Can understanding squid life-history strategies and recruitment improve management?
    O’Dor, RK
  • Inter-annual plasticity of squid life-history and population structure: ecological and management implications
    Pecl, GT; Moltschaniwskyj, NA; Tracey, S; Jordan, A
  • A note on mating and egg deposition by Sepioteuthis lessoniana in Ishigaki Island, Okinawa, southwestern Japan
    Segawa, S; Izuka, T; Tamashiro, T; Okutani, T

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