Description: Seasonal growth rates and size- and age-at-maturity were analysed for the small near-shore tropical loliginid squid Loliolus noctiluca off North Queensland, Australia, over a 2 yr. Age of individuals was determined using daily statolith increments. The life cycle of L. noctiluca off North Queensland was just over 4 mo. Analysis of growth found that growth was non-asymptotic, and the form of the curve; exponential, linear or log-linear, depended on sex and season that individuals were caught. Winter-caught individuals were the fastest growing and achieved the largest size compared with summer or autumn-caught individuals. Furthermore, females grew faster than males during the winter. The patterns of growth of L. noctiluca were compared between tropical North Queensland and temperate New South Wales. The temperate individuals lived longer and had slower growth rates. There was also a marked seasonal influence on the onset of sexual maturity among the North Queensland population, with the fastest growing winter-caught individuals maturing later than the autumn or summer individuals. L. noctiluca has a large latitudinal range from New Guinea to Tasmania, this study, and published work, suggests a trend towards increased lifespan and decreased growth rate with increasing latitude.

Description: Squids typically demonstrate considerable plasticity in individual growth rates. However, it is not known if individuals growing at different rates also differ at lower levels of organisation. We wished to determine if Sepioteuthis lessoniana individuals that were larger than predicted for their age differed in their digestive gland and mantle muscle tissue proximal composition or mantle muscle structure, compared with individuals that were smaller for their age than predicted. The residual, the difference between the observed size-at-age and that predicted by the growth equation, was used as a measure of the difference in an individual's lifetime growth from the population average. Individual squid varied considerably in their size-at-age, with juveniles showing less variation than adults. Juveniles had greater concentrations of lipid in their muscle tissue, perhaps due to an emphasis on storing energy reserves in this critical period of their life. Differences in biochemical constituents in both the digestive gland and muscle tissue were not related to the size-at-age of individuals, despite biochemical make-up being the lowest organisational level of growth. This may be due to whole animal growth and changes in biochemical composition occurring on different time scales. There was no relationship between the size-at-age of individuals and average mantle muscle fibre size. A strong relationship, however, existed between the size of mantle muscle blocks and the size-at-age of individuals for both juvenile and adult individuals, suggesting that larger muscle blocks are related to both body size and faster individual growth rates. This study demonstrates a clear relationship between mantle muscle structure and growth and the size-at-age of S. lessoniana individuals.

Description: This study examined the relation between statolith and somatic growth in the tropical squid Sepioteuthis lessoniana. Five separate linear dimensions were measured on the statoliths of 103 individuals (17–245 mm mantle length). In addition the statoliths of 80 adults (82–245 mm mantle length) were weighed. Statolith increment analysis provided age estimates for 78 individuals. Statolith total length was correlated with age for squid less than ~60 days of age, although neither statolith total length nor weight was a useful predictor of age in older squid. Combining the five statolith dimensions to produce a description of statolith shape provided only slightly better estimates of age than statolith total length or weight alone. Statolith shape changed during ontogeny, developing from relatively elongate juvenile statoliths into the adult form with more robust dorsal and lateral domes. This development was reflected in wider spacing and superior optical definition of daily growth increments in the dorsal and lateral domes of adult statoliths, in relation to the slower growing rostrum. Growth of S. lessoniana statoliths does not appear to be strongly linked to mantle growth; both statolith total length and weight increase more slowly than mantle length.

Description: This study sought to determine if the tropical loliginid squid Photololigo sp. stores energy in the form of lipid, carbohydrate or protein for reproductive investment. Individuals were examined for changes in morphometry, mantle muscle structure and concentrations of water, lipid, carbohydrate and protein in muscle tissue and the digestive gland, associated with the stage of reproductive maturation. Muscle mass was affected by reproductive maturation in females. Mature individuals were lighter for their length compared with females in the early stages of maturation. Concentrations of lipid and carbohydrate in the muscle tissue were very low, and female Photololigo sp. showed equivocal evidence of declining lipid and carbohydrate levels with egg production. There was no evidence of dramatic changes in protein concentration in the mantle muscle with reproductive maturation. Male Photololigo sp. showed a change in the digestive gland with maturation, with water content increasing and protein concentrations decreasing. The digestive gland of both male and female Photololigo sp. increased in size and contained less water with growth. There was little evidence that the storage and transfer of energy for reproduction occurred in Photololigo sp. Instead, it is probable that energy for reproduction is predominantly sourced directly from consumed food.

Description: Statolith size and growth was used to determine the influence of abiotic factors on the growth of Loligo vulgaris and Sepioteuthis australis embryos. Recently spawned egg masses collected from the field were incubated in the laboratory under different levels of light intensity, photoperiod, or short periods of low salinity (30‰). Double tetracycline staining was used to follow statolith growth. In L. vulgaris constant light conditions produced significantly slower growth in the embryonic statoliths and embryos held at summer photoperiod had slower statolith growth than those held at winter photoperiods. However once they hatched out there was no evidence that photoperiod affected statolith growth. After hatching, in all photoperiods statolith growth rates decreased in comparison with late embryonic rates. In S. australis embryos, differences between the high and medium light intensities for summer and intermediate photoperiods were found, suggesting that under summer incubation temperature, longer daylengths at medium light intensity favoured higher statolith growth for this species. In comparison to controls, slower statolith growth in S. australis embryos due to low salinity only occurred when exposed for 72 h. Comparison with previous studies indicates that temperature seems to be the main abiotic factor influencing statolith growth during early stages, however, interactions among all abiotic factors needs to be determined as well as the unknown influence of other isolated factors, e.g., oxygen concentration within the egg mass.

Description: 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.