World squid fisheries

Peer reviewedPublisher PD

Enzymatic capacities of metabolic fuel use in cuttlefish (Sepia officinalis) and responses to food deprivation: insight into the metabolic organization and starvation survival strategy of cephalopods

Food limitation is a common challenge for animals. Cephalopods are sensitive to starvation because of high metabolic rates and growth rates related to their "live fast, die young" life history. We investigated how enzymatic capacities of key metabolic pathways are modulated during starvation in the common cuttlefish (Sepia officinalis) to gain insight into the metabolic organization of cephalopods and their strategies for coping with food limitation. In particular, lipids have traditionally been considered unimportant fuels in cephalopods, yet, puzzlingly, many species (including cuttlefish) mobilize the lipid stores in their digestive gland during starvation. Using a comprehensive multi-tissue assay of enzymatic capacities for energy metabolism, we show that, during long-term starvation (12 days), glycolytic capacity for glucose use is decreased in cuttlefish tissues, while capacities for use of lipid-based fuels (fatty acids and ketone bodies) and amino acid fuels are retained or increased. Specifically, the capacity to use the ketone body acetoacetate as fuel is widespread across tissues and gill has a previously unrecognized capacity for fatty acid catabolism, albeit at low rates. The capacity for de novo glucose synthesis (gluconeogenesis), important for glucose homeostasis, likely is restricted to the digestive gland, contrary to previous reports of widespread gluconeogenesis among cephalopod tissues. Short-term starvation (3-5 days) had few effects on enzymatic capacities. Similar to vertebrates, lipid-based fuels, putatively mobilized from fat stores in the digestive gland, appear to be important energy sources for cephalopods, especially during starvation when glycolytic capacity is decreased perhaps to conserve available glucose

Multiple spawning in the tropical squid Photololigo sp.: what is the cost in somatic growth?

This study assesses the potential of the tropical loliginid squid Photololigo sp. to lay multiple batches of eggs and examines changes in somatic growth during reproduction. Histological analysis of the ovary and the relative size of the oviduct to mantle weight and ovary weight were used to determine the potential for multiple spawning. Ovaries of mature females always had immature and mature oocytes present, suggesting that not all the oocytes were maturing simultaneously and that multiple batches of eggs were being produced. Furthermore, poor correlations of oviduct weight with body size and ovary weight indicated that mature oocytes were not accumulating in the oviduct for a single spawning event. Both these observations supported the hypothesis that Photololigo sp. has the potential to lay multiple batches of eggs throughout its life. Specific growth rates, length-weight relationships, relative growth of somatic and reproductive tissue and microscopic assessment of muscle tissue were compared between immature and mature females. Growth rates of immature females were almost twice as fast as those of mature females. Mature females also had no large muscle fibres present, suggesting that energy for reproduction was mobilised from the muscle tissue

Effect of temperature and food levels on the growth and condition of juvenile Sepia elliptica (Hoyle 1885): an experimental approach

Temperature and ration level can differentially affect growth and life history characteristics of marine organisms. In this experiment we reared juvenile cuttlefish, Sepia elliptica, under two feeding regimes (satiation and half satiation) and two temperature regimes (25 and 30°C). This study examined differences in somatic growth, muscle tissue structure and composition as a function of temperature and food levels. We estimated body mass and the concentration of water, carbohydrate, protein and lipid in the mantle muscle tissue for each individual. Both high water temperature and high feeding rations increased growth rates. Temperature appeared to change the rates of muscle fibre generation and fibre growth similarly. In contrast, the ration level altered the relative rates of fibre production and fibre growth. The muscle tissue of individuals reared at 30°C had higher concentrations of carbohydrate and protein. In contrast, increasing ration levels only increased carbohydrate concentrations in the muscle tissue. The muscle tissue of reared juveniles had lower concentrations of carbohydrate and protein than wild individuals of similar size. In conclusion, water temperature and feeding levels both affect somatic growth, but the nature of the effect at the sub-organismal level differs

The adaptive response of protein turnover to the energetic demands of reproduction in a cephalopod

Sourcing energy for reproduction is a major driver of the life-history characteristics of animals. Unlike other molluscs, cephalopods do not appear to have significant glycogen stores, and energy is either sourced directly from ingested food or mobilized from protein stores in the muscle. Given the importance of protein to cephalopods, this study quantified changes in protein turnover in the muscle tissue in reproductively immature and maturing/mature individuals. Quantifying protein accretion and protein synthesis allowed an assessment of protein turnover in immature and maturing individuals of the southern dumpling squid (Euprymna tasmanica), which has fast nonasymptotic growth, has a short generation time, and does not use lipid stores. This study found that protein turnover slowed in the mantle muscle tissue with gonad growth, suggesting an adaptive response to the energy demands associated with reproduction but one that allows for continued somatic growth and muscle function in these animals. However, the cost of reproduction may be indirect, with less energy available for somatic repair, and therefore may be responsible for the rapid senescence typical of many cephalopod species

Changes in muscle structure associated with somatic growth inIdiosepius pygmaeus, a small tropical cephalopod

Mantle muscle tissue of Idiosepius pygmaeus was examined to describe changes in structure and organization associated with growth. Growth in I. pygmaeus|DD was a function of both an increase in muscle fibre number and fibre size within muscle blocks. Continuous fibre production over the observed life span of I. pygmaeus was indicated by the presence of very small muscle fibres (< 1.0 μm in diameter) in substantial proportions in all sizes of individuals. Muscle blocks became larger as animals increased in size, although new muscle blocks were generated in all sizes of individuals. Mantle muscle fibres had a maximum size of 11 μm. Therefore, for an individual to continue increasing muscle block sizes, new fibres must be produced. This is further evidence of continuous fibre production throughout the size range of I. pygmaeus examined. The relative rates of muscle fibre generation and fibre growth depended on the size of the animal and position along the mantle (anterior, mid or posterior mantle). The predominance of small fibres and blocks at the anterior end of the mantle suggested that this was the primary growth region. Mitochondriapoor and mitochondria‐rich muscle fibres from small individuals had much larger mitochondrial cores than muscle fibres from larger animals. Changes in the muscle structure are discussed with respect to the metabolic and energetic requirements of I. pygmaeus, and how these may change with growth

The influence of ration level on growth and statolith increment width of the tropical squid Sepioteuthis lessoniana (Cephalopoda: Loliginidae): an experimental approach

Juvenile squids were grown in individual 2.6-l floating enclosures and were fed either a high- or a low-ration diet of fish and the crustacean Acetes. Squids were maintained for a maximum of 44 days in two experiments. The high-ration individuals reached a significantly larger size in both experiments (27, 25.5 mm mean mantle length, ML) compared to their low-ration siblings (19 mm mean ML) in both experiments. The statolith increment widths prior to the start of the experiment were significantly wider (between 3 and 4 μm) compared to the increment widths after the start of the experiment (between 2 and 3 μm) both for the low- and the high-ration squids. High-ration squids also had significantly wider increments and larger statoliths than their low-ration siblings. Even though we detected consistent trends in daily statolith increment widths for the different feeding regimes, we could not detect variation in increment widths at a daily level of resolution (i.e. as a result of differences in day-to-day food intake at an individual level). This was probably due to the relatively consistent diet experienced by each individual. These experiments revealed that ration level influences squid growth rate, statolith size and daily statolith increment width

Small-scale spatial and temporal patterns of egg production by the temperate loliginid squid Sepioteuthis australis

This study explored the spawning dynamics of southern calamary (Sepioteuthis australis) by estimating small-scale temporal and spatial variability in egg production in an area known to attract spawning aggregations. Surveys of the seagrass beds (Amphibolis antarctica) over 14 months determined the timing and location of egg deposition, as well as estimating total egg production and loss of deposited egg masses from the spawning grounds. Egg laying in the inshore seagrass beds occurred predominantly during the austral spring and early summer. Egg production at one location (Hazards Bay) was very similar between the two years, but at the second location (Coles Bay) egg production was threefold less during the second summer. There was considerable spatial variability in egg production among seagrass beds within a kilometre of each other as well as within 10 km. Variability in the use of seagrass beds by the squid during each summer could not be attributed to differences in seagrass density or vegetation cover. Losses of deposited egg masses in the A. antarctica beds were detected on two occasions. On the first occasion the loss was correlated with storms; however, the second and smaller loss of egg masses was not correlated with storm activity. Information about the spatial and temporal patterns of egg production was used to make recommendations about the use of fishing closures to protect spawning adults from over-fishing

Spatial and temporal variation in growth rates and maturity in the Indo-Pacific squid Sepioteuthis lessoniana (Cephalopoda: Loliginidae)

Age, growth and maturity parameters are described for the Indo-Pacific squid Sepioteuthis lessoniana both temporally and spatially (equatorial, tropical and subtropical). Tropical squid that grew through periods of warming water temperatures grew 9% faster than squid that grew through periods of cool water temperatures. The tropical spring-hatched and equatorial squid had similar growth rates (3.24, 3.18 g/day) and these were significantly faster than the tropical summer/autumn hatched squid (2.89 g/day). The oldest squid aged was 224 days, but the majority of individuals were 400 g, 85% greater than tropical and equatorial squid. Geographical differences revealed that subtropical mature winter females and males had mean ages >150 days, respectively 17% and 23% older than their tropical mature winter counterparts. Temporal differences in age at maturity were also evident with tropical winter females and males having a mean age of ~140 days, respectively 41% and 25% older than their summer counterparts. Cooler subtropical and winter tropical squid had the heaviest gonads (>15 g ovaries, >1.5 g testes) compared to summer tropical and equatorial squid. However, relative gonad investment (GSI) values of the cooler squid were significantly lower with cool subtropical and winter tropical females having GSI values <3, which was about half the value of the warmer water females. This study revealed considerable plasticity in the size-at-age of this species. The tropical population had growth parameters that fluctuated between an equatorial strategy (fast growth, small body size, and small gonads) and a subtropical strategy (large body size, slower growth, and large gonads) depending on season