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Spawning aggregations of squid (Sepioteuthsis australis) populations: a continuum of 'microcohorts'

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Moltschaniwskyj, NA and Pecl, GT (2007) Spawning aggregations of squid (Sepioteuthsis australis) populations: a continuum of 'microcohorts'. Reviews in Fish Biology and Fisheries, 17 (2-3). pp. 183-195. ISSN 0960-3166

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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-atage,
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 microcohorts
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.

Item Type: Article
Keywords: Spawning aggregation Squid Fishing closures Egg production Population structure
Journal or Publication Title: Reviews in Fish Biology and Fisheries
Publisher: Springer Netherlands
Page Range: pp. 183-195
ISSN: 0960-3166
Identification Number - DOI: 10.1007/s11160-006-9025-7
Date Deposited: 07 Apr 2008 14:41
Last Modified: 18 Nov 2014 03:36
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