Inter-annual plasticity of squid life history and population
structure: ecological and management implications
Oecologia (2004) 139: 515ââ¬â524
G. T. Pecl . N. A. Moltschaniwskyj . S. R. Tracey .
A. R. Jordan
ABSTRACT
Abstract Population size and structure, as well as
individual growth rates, condition, and reproductive
output, respond to environmental factors, particularly in
short-lived and fast-growing squid species. We need to
understand the mechanisms through which populations
respond to environmental conditions, to predict when or if
established relationships, used as management tools to
forecast recruitment strength, might break down completely.
Identifying characteristics of successful recruits who
have grown under different environmental scenarios may
improve our understanding of the mechanistic connections
between environmental conditions and the temporal
variation in life history characteristics that ultimately
affect recruitment. This 5-year study sought to determine
the association between key life history characteristics of
southern calamary Sepioteuthis australis (growth rate,
body size, and patterns of repro-somatic energy allocation)
and the environmental conditions experienced by individuals
on the east coast of Tasmania, Australia. Among
years, all population and individual parameters examined
were highly variable, despite the environmental regime
during the study not encompassing the extremes that may
occur in this dynamic region. Temperature was not clearly
associated with any of the individual or population
differences observed. Populations of apparently similar
abundance were composed of individuals with strikingly
different biological characteristics, therefore seeking
relationships between abundance and environmental parameters
at gross levels did not shed light on the
mechanisms responsible for population size. Importantly,
inter-annual differences in squid size, condition, reproductive
investment, and possibly growth rate, were sexspecific,
indicating that males and females responded
differently to similar factors. Among years differences in
body size were extreme, both among the male component
of the population and between genders. The relative
importance of many size-based processes that contribute to
population size and structure (e.g. predation, starvation,
competition, and reproductive success) will therefore vary
inter-annually.
Keywords Temporal variability . Growth . Environment recruitment
. Reproduction . Condition
structure: ecological and management implications
Oecologia (2004) 139: 515ââ¬â524
G. T. Pecl . N. A. Moltschaniwskyj . S. R. Tracey .
A. R. Jordan
ABSTRACT
Abstract Population size and structure, as well as
individual growth rates, condition, and reproductive
output, respond to environmental factors, particularly in
short-lived and fast-growing squid species. We need to
understand the mechanisms through which populations
respond to environmental conditions, to predict when or if
established relationships, used as management tools to
forecast recruitment strength, might break down completely.
Identifying characteristics of successful recruits who
have grown under different environmental scenarios may
improve our understanding of the mechanistic connections
between environmental conditions and the temporal
variation in life history characteristics that ultimately
affect recruitment. This 5-year study sought to determine
the association between key life history characteristics of
southern calamary Sepioteuthis australis (growth rate,
body size, and patterns of repro-somatic energy allocation)
and the environmental conditions experienced by individuals
on the east coast of Tasmania, Australia. Among
years, all population and individual parameters examined
were highly variable, despite the environmental regime
during the study not encompassing the extremes that may
occur in this dynamic region. Temperature was not clearly
associated with any of the individual or population
differences observed. Populations of apparently similar
abundance were composed of individuals with strikingly
different biological characteristics, therefore seeking
relationships between abundance and environmental parameters
at gross levels did not shed light on the
mechanisms responsible for population size. Importantly,
inter-annual differences in squid size, condition, reproductive
investment, and possibly growth rate, were sexspecific,
indicating that males and females responded
differently to similar factors. Among years differences in
body size were extreme, both among the male component
of the population and between genders. The relative
importance of many size-based processes that contribute to
population size and structure (e.g. predation, starvation,
competition, and reproductive success) will therefore vary
inter-annually.
Keywords Temporal variability . Growth . Environment recruitment
. Reproduction . Condition