Oceanic Squid Research Articles

Towards the identification of the ommastrephid squid paralarvae (Mollusca: Cephalopoda): morphological description of three species and a key to the north-east Atlantic species

Oceanic squids of the family Ommastrephidae are an important fishing resource worldwide. Although cumulative knowledge exists on their subadult and adult forms, little is known about their young stages. Their hatchlings are among the smaller cephalopod paralarvae. They are characterized by the fusion of their tentacles into a proboscis and are very difficult to identify to species level, especially in areas where more than one species coexist. Seven species are found in the north-east (NE) Atlantic. In this study, mature oocytes of Illex coindetii, Todarodes sagittatus and Todaropsis eblanae were fertilized in vitro to obtain and describe hatchlings. Full descriptions based on morphometric characters, chromatophore patterns, skin sculpture and the structure of proboscis suckers are provided based on live specimens. This information was combined with previous descriptions of paralarvae, not necessarily based on DNA or known parentage, from four other ommastrephid species distributed in the same area and a dichotomous key was developed for the identification of paralarvae of the NE Atlantic. The most useful taxonomic characters were: the relative size of the lateral and medial suckers of the proboscis, the presence/absence of photophores and the arrangement of pegs on the proboscis suckers. This key was successfully used to identify wild collected rhynchoteuthion paralarvae from the NE Atlantic. Reliable identification of wild paralarvae can foster a better understanding of the population dynamics and life cycles of ommastrephid squids.

Male copulatory behavior interrupts Japanese flying squid Todarodes pacificus female spawning activity

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 551:277-281 (2016) - DOI: https://doi.org/10.3354/meps11776 NOTE Male copulatory behavior interrupts Japanese flying squid Todarodes pacificus female spawning activity Pandey Puneeta1,*, Dharmamony Vijai1,3, Jun Yamamoto2, Yasunori Sakurai1,4 1Department of Marine Bioresources and Ecology, School of Fisheries Sciences, Hokkaido University, 3-1-1 Minato-cho, Hakodate 041-8611, Japan 2Field Science Center for Northern Biosphere, Hokkaido University, Hakodate, Hokkaido 041-8611, Japan 3Present address: Oceanography Division, Tohoku National Fisheries Research Institute, 25-259 Shimo-mekurakubo, Samemachi, Hachinohe, Aomori 031-0841, Japan 4Present address: Hakodate Cephalopod Research Center, Fisheries and Oceans Hakodate, Benten-cho 20-5, Hakodate, Hokkaido 040-0051, Japan *Corresponding author: puneeta83@gmail.com ABSTRACT: Batch spawning, intermittent spawning and multiple spawning represent common reproductive strategies among cephalopods. These flexible spawning strategies are also common in fishes, and are thought to be a female trait that is programmed depending on environmental parameters. The ommastrephid squid Todarodes pacificus, being a terminal spawner, is considered to have a single spawning event, extruding one large egg mass and dying soon thereafter. Females that are interrupted by males exhibiting mating behavior, while extruding the egg mass, spawn multiple egg masses over the course of 2-3 d instead of dying soon after spawning the first egg mass. We demonstrate that male mating behavior causes ‘forced’ intermittent spawning by females (i.e. more than one spawning event). We hypothesize that in T. pacificus, some males use this strategy to mate with females unable to repel advances while spawning, thus providing the male with the opportunity to contribute sperm and enhance gene flow. KEY WORDS: Batch spawning · Spawning interruption · Multiple paternity · Egg mass · Oceanic squid Full text in pdf format Supplementary material PreviousCite this article as: Puneeta P, Vijai D, Yamamoto J, Sakurai Y (2016) Male copulatory behavior interrupts Japanese flying squid Todarodes pacificus female spawning activity. Mar Ecol Prog Ser 551:277-281. https://doi.org/10.3354/meps11776Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 551. Online publication date: June 09, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Growth and Mortality of the Oceanic squid Sthenoteuthis oualaniensis (Lesson, 1830) off the south west coast of India

The study attempted to understand the difference in growth and mortality rate, between two phenotypic variants of the oceanic squid Sthenoteuthis oualaniensis. Specimens (1015 nos.) of the species collected off the south-west coast of India (lat. 07 to 11oN; long. 74 to 77o E) at a depth range of 180-2601 m were used in this study. Data on dorsal mantle length (DML) of dwarf and medium forms of the species were collected and analysed using the length-based FiSAT routine. L∞ varied from 17.37 to 18.05 cm with an average of 17.89 cm for the dwarf and 29.5 to 30.49 cm with an average of 30.08 cm for medium form. Dwarf forms had a higher average K value (3.65 cm y-1) with 􀂛 of 3.06, whereas, medium form had a lower average K value (2.38 cm y-1) with 􀂛 of 3.33. Growth curve and longevity study indicated longer than a year life span for medium forms (461 days) with growth rate of 13.3 cm DML in three months (91 days), 20.8 cm in six months (182 days) and 25.0 cm in nine months (273 days). Dwarf form attained maximum length in ten months (302 days) with a growth of 10.5 cm in three months (91 days), 14.9 cm in six months (182 days) and 16.7 cm DML in nine months (274 days). The average total instantaneous mortality (Z) was estimated as 4.58 y-1 for dwarf and 6.03 y-1 for medium form. As there was no commercial fishing for this species, fishing mortality was considered nil. Therefore, total mortality rate Z was considered equivalent to natural mortality.

Geographical variation in the body size of adult female sperm whales (Physeter macrocephalus) – an example of McNab’s resource rule?

Abstract This study investigates possible regional variations in size composition of adult female sperm whales (Physeter macrocephalus) using data from 3302 pregnant individuals taken on Soviet whaling expeditions to the Southern Hemisphere 1961/62–1974/75. A general linear model (GLM) was used to take the covariates of expedition, latitude and ocean basin into account. The average body size decreased from south to north in each ocean basin, with the biggest decrease (about 200 cm) in the Indian Ocean; followed by the Pacific Ocean (about 110 cm), and the Atlantic Ocean (about 80 cm). Independent data confirm the small size of female/immature sperm whales in some tropical areas of the Indian and Pacific Oceans. The mechanism responsible for this geographic variation in sperm whale growth could reflect culturally transmitted differences in foraging behaviour between clans of female/immature sperm whales in response to differing availabilities of prey resources by geographical region – McNab’s resource rule. However there is little available information for such a mechanism to be readily identifiable. Although data for oceanic squids (sperm whale’s main source of food) are lacking, there is evidence that the individual sizes of neritic species are positively correlated with latitude. Hence feeding in equatorial regions may be energetically more demanding due to smaller individual prey size, with consequent effects on growth rate.

Biogeography of Cephalopods in the Southern Ocean Using Habitat Suitability Prediction Models

Our understanding of how environmental change in the Southern Ocean will affect marine diversity, habitats and distribution remain limited. The habitats and distributions of Southern Ocean cephalopods are generally poorly understood, and yet such knowledge is necessary for research and conservation management purposes, as well as for assessing the potential impacts of environmental change. We used net-catch data to develop habitat suitability models for 15 of the most common cephalopods in the Southern Ocean. Using modeled habitat suitability, we assessed favorable areas for each species and examined the relationships between species distribution and environmental parameters. The results compared favorably with the known ecology of these species and with spatial patterns from diet studies of squid predators. The individual habitat suitability models were overlaid to generate a “hotspot” index of species richness, which showed higher numbers of squid species associated with various fronts of the Antarctic circumpolar current. Finally, we reviewed the overall distribution of these species and their importance in the diet of Southern Ocean predators. There is a need for further studies to explore the potential impacts of future climate change on Southern Ocean squid.

Distribution of short-finned squid Illex argentinus (Cephalopoda: Ommastrephidae) inferred from the diets of Southern Ocean albatrosses using stable isotope analyses

The diets of marine predators are a potential source of information about range shifts in their prey. For example, the short-finned squid Illex argentinus, a commercially fished species on the Patagonian Shelf in the South Atlantic, has been reported in the diet of grey-headed, Thalassarche chrysostoma; black-browed, T. melanophris; and wandering, Diomedea exulans, albatrosses breeding at Bird Island, South Georgia (54°S 28°W) in the Southern Ocean. Tracking data suggest that these birds may feed on I. argentinus while foraging in Southern Ocean waters during their breeding season. This led to the hypothesis that I. argentinus may occur south of the Antarctic Polar Front. To test this hypothesis, we used stable isotope analyses to assess the origin of I. argentinus. We compared I. argentinus beaks from the diets of the three albatross species with beaks of cephalopod species endemic to the Patagonian Shelf and others from the Southern Ocean. Our results show that I. argentinus from the diet of albatrosses at Bird Island have δ13C values in the range −18.77 to −15.28‰. This is consistent with δ13C values for Octopus tehuelchus, a typical species from the Patagonian Shelf. In contrast, Alluroteuthis antarcticus, a Southern Ocean squid, has typically Antarctic δ13C in the range −25.46 to −18.61‰. This suggests that I. argentinus originated from warmer waters of the Patagonian Shelf region. It is more likely that the albatross species obtained I. argentinus by foraging in the Patagonian Shelf region than that I. argentinus naturally occurs south of the Antarctic Polar Front.

Spawning pattern of the neon flying squid <em>Ommastrephes bartramii</em> (Cephalopoda: Oegopsida) around the Hawaiian Islands

Summary: The neon flying squid, Ommastrephes bartramii, is an oceanic squid species that is widely distributed in the North Pacific, with the winter-spring cohort spawning around the Hawaiian Islands. Here, we investigated the spawning characteristics of O. bartramii by analyzing various reproductive parameters of individuals (622 males, 108 females) collected in this region. Female spawning status was determined from the somatic indices and histological characteristics of the ovaries. At all developmental stages, the ovaries of spawned females contained oocytes, and oviduct fullness was not correlated with body size. Thus, because the eggs mature asynchronously, with multiple filling and evacuation events, this species is considered an intermittent spawner. Mature males with developed accessory glands were also present within the distribution range of healthy spawned females, indicating that mating occurs between spawning events. Our data indicate that the first spawning event occurs at a mantle length of ~520-540 mm for Hawaiian O. bartramii. Subsequently, the squid forage and grow, and refill the oviducts, before the second spawning event occurs.

Variations of oceanic fronts and their influence on the fishing grounds of Ommastrephes bartramii in the Northwest Pacific

Two predominant currents, the warm Kuroshio Current and the cold Oyashio Current, meet in the Northwest Pacific Ocean. The dynamics of physical oceanographic structures in this region, including frontal zones and meandering eddies, result in a highly productive habitat that serves as a favorable feeding ground for various commercially important species. Neon flying squid, Ommastrephes bartramii, is an important oceanic squid, which is widely distributed in the North Pacific Ocean. Based on the catch data collected by Chinese squid jigging fleets and relevant environmental data, including sea surface temperature (SST) and fronts (represented by gradients of SST and thermocline) during 1998–2009, the variations of oceanic fronts and their influence on the fishing grounds of O. bartramii were evaluated, and the differences in distribution of fishing grounds of O. bartramii in 2000 and 2002 were compared by describing the differences in vertical temperature between 0–300 m. It was found that the preferred horizontal temperature gradient of SST for O. bartramii tended to be centered at 0.01–0.02°C/nm, which attracted nearly 80% of the total fishing effort, and the preferred horizontal temperature gradients at the 50 m and 105 m layers were mainly located at 0.01–0.03°C/nm, which accounted for more than 70% of the total fishing effort during August-October. The preferred vertical temperature gradient within the 0–50 m layer for O. bartramii tended to be centered at 0.15–0.25°C/m during August and September and at 0.10–0.15°C/m in October, implying that the mixed surface layer was distributed at depths of 0–50 m. It was concluded that the vertical temperature gradient was more important than the horizontal temperature gradient in playing a role in forming the fishing ground. The results improved our understanding of the spatial dynamics of the O. bartramii fishery.

Malcolm Roy Clarke. 24 October 1930 — 10 May 2013

Malcolm Clarke was a leading authority on cephalopods and their significance in the world oceans. Much of his knowledge of their abundance was gained through a study of their beaks from the stomachs of predators, particularly sperm whales. He had a lifelong enthusiasm for sperm whales (and for other cetaceans), leading him to reappraise their buoyancy control. Postgraduate experience as a whaling inspector in the Antarctic led to his joining the National Institute of oceanography in 1958 to work on oceanic squids. In 1972 he moved to the Marine Biological association’s Plymouth laboratory, where he was elected FRS in 1981 and was awarded a Special Merit promotion. He remained there until retirement in 1987, during which time he set up the Cephalopod International Advisory Council (CIAC). After retirement he travelled widely and continued his research on whales and squids, based first at home in Plymouth and later at his house in Pico, in the Azores.

Design of the Centralized Control Circuit for Large Ship Borne Squid Jigging Machine

Squid jigging machine is an important equipment in the oceanic squid jigging fisheries. Now, we have used the intelligent squid fishing machine, though, we have to guard the machine one by one. To reduce the labor on deck, we designed a serial interface circuit between PC and Single Chip Microcomputer (SCM) for the communication within multiple squid jigging machines by the way of RS-485 bus, realizing centralized control of machines. For hardware, we converted TTL level to 485 level by serial interface conversion chip so that SCM could achieve RS-485 interface communication; For software, we customized instruction sets, data package format, communication protocol format. We designed RS-485 bus interface circuit for PC and SCM by simulation software Proteus. Through tests in the field, we knew the circuit makes the connection of centralized control network simple, and signal transmission reliable. We will pay particular attention to the design of communication protocols software, which can provide new thinking of designing about communication within multiple machines for the researchers.

Fecundity, oogenesis, and ovulation pattern of southern African Lycoteuthis lorigera (Steenstrup, 1875)

Lycoteuthis lorigera is among the most abundant mesopelagic squid on the continental slope of the south Atlantic. It is the dominant prey in some commercially harvested groundfish. Despite its abundance and importance in the mesopelagic foodweb, its general biology is poorly known. In this study, the spawning pattern and fecundity of L. lorigera from southern African waters were investigated. Both histological examination and length frequency analysis of ovaries in various stages of development revealed that the ovulation pattern of L. lorigera is asynchronous, which indicates a spawning strategy where batches of eggs are spawned repeatedly over time. More specifically, ovulation is group synchronous, where distinct batches of 1,200–2,400 eggs ripen in the ovary and accumulate in the oviducts. The potential fecundity was estimated to be 20,000–50,000 in immature females (n = 6) and 8,000–25,000 in mature females (n = 21). The number of ripe eggs in the oviducts suggests that batches of spawned egg masses contain between 1,000 and 4,000 eggs. The reproductive strategy of L. lorigera is discussed and compared to the reproductive strategies of oceanic squid inhabiting the continental slope of southern Africa.

Design and Simulation of the Communication Circuit on Multi Jigging Machines

Squid jigging machine is an important equipment in the oceanic squid jigging fisheries. In order to take centralized control of multi jigging machines, improve manufacturing efficiency, this paper introduce the centralized control circuit between PC and single chip microcomputer for the communication within multi jigging machines by the way of RS-485 bus in detail, and we focus on describing the design of the hardware circuit for the centralized control system. The master is PC while the slave is MCS-51. The communication between them is realized by the MSComm control in VB6.0. It researches practicable ways to improve the reliability of RS-485 bus system, respectively from different aspects such as bus conflict, burst interference, common mode interference and nodes fault and so on. This study provides reference data for the researchers.

Cryobiology of cephalopod (Illex coindetii) spermatophores

Cephalopod culture is expected to increase in the near future and sperm cryopreservation would be a valuable tool to guarantee sperm availability throughout the year and to improve artificial insemination programs. We have studied the tolerance of spermatophores from the oceanic squid Illex coindetii to several cryoprotectants, in two toxicity experiments and a cryopreservation test. Five permeating cryoprotectants were tested: Dimethyl sulfoxide (Me2SO), methanol, glycerol, propylene glycol and ethylene glycol. In the first experiment, spermatophores were exposed to the five cryoprotectants at 5% (v/v) and 15% (v/v) at 4°C for 5min. In the second experiment, spermatophores were exposed to the cryoprotectants at 15% using different exposure times: 5, 15 and 30min. In a third experiment, we tested two cryopreservation protocols: LN2 vapor or −80°C freezer, using a 15% cryoprotectant and 15 or 30min of exposure. Viability and mitochondrial activity were assessed using Mitotracker deep red, YOPRO1 and Hoechst 33342, by flow cytometry. Spermatozoa in this species remain viable after cryoprotectant exposure but their quality decreased considerably after cryopreservation, only 5–10% of spermatozoa being motile. Flow cytometry demonstrated that Me2SO may be the most appropriate cryoprotectant for I. coindetii spermatozoa, and shows a first approach on cephalopod sperm cryopreservation, opening new possibilities for the research and culture of this group of molluscs.

Oceanic squid do fly

Using powerful jet propulsion, some squid species are able to exit the water and become airborne; this is a common behavior seen throughout the world’s oceans. However, direct scientific observation is rare, with most studies relying on anecdotal evidence and limited photographic documentation. Here, we examine the flying behavior of young oceanic squid (Ommastrephidae) observed in sequential photographs taken in the Northwest Pacific (35o34.0′N, 146o19.3′E) on July 25, 2011. We define four phases in the flight process: launching, jetting, gliding and diving. During flight, squid actively change their aerial posture and attitude depending on the flight phase and their distance from the water. The present study demonstrated that flight of squid is not simple gliding after incidental exit from the water, but involves jet propulsion, generation of lift force and control of different body postures in different flight phases, which have evolved to enhance escape from predators.

Hypoxia tolerance and antioxidant defense system of juvenile jumbo squids in oxygen minimum zones

Jumbo squid (Dosidicus gigas) is a large oceanic squid endemic off the Eastern Tropical Pacific that undertakes diel vertical migrations into mesopelagic oxygen minimum zones. One of the expected physiological effects of such migration is the generation of reactive oxygen species (ROS) at the surface, promoted by the transition between hypoxia and reoxygenation states. The aim of this study was to investigate the energy expenditure rates and the antioxidant stress strategies of juvenile D. gigas under normoxia and hypoxia, namely by quantifying oxygen consumption rates, antioxidant enzyme activities [including superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST)], heat shock protein expression (Hsp70/Hsc70), and lipid peroxidation [malondialdehyde (MDA) levels]. A high significant decrease (68%) in squid’s metabolic rates was observed during hypoxia (p<0.05). This process of metabolic suppression was followed by a significant increase in Hsp70/Hsc70 expression (p<0.05), which may be interpreted as a strategy to prevent post-hypoxic oxidative damage during the squid’s night upwards migration to the surface ocean. On the other hand, in normoxia, the higher SOD and CAT activities seemed to be a strategy to cope with the reoxygenation process, and may constitute an integrated stress response at shallower depths. GST activity and MDA concentrations did not change significantly from normoxia to hypoxia (p>0.05), with the latter indicating no enhancement of lipid peroxidation (i.e. cellular damage) at the warmer and normoxic surface waters. The understanding of such physiological strategies that are linked to oxygen deprivation and reoxygenation phases may provide valuable information about how this species is quickly responding to the impacts of environmental stressors coupled with global climate change.

The foraging ecology of an oceanic squid, Todarodes filippovae: The use of signature lipid profiling to monitor ecosystem change

Signature lipid/fatty acid and stomach content analyses were used in combination to examine the feeding ecology of Todarodes filippovae, an abundant oceanic squid with a broad circumpolar distribution in continental slope waters in the Southern Ocean. Both techniques show a diet that is closely linked to prey availability and abundance, with some specialisation occurring for Myctophid fishes which dominated the diet numerically and taxonomically. Mean monthly differences in total lipid content of the digestive gland correlated with satellite-derived sea surface chlorophyll, illustrating that the diet is closely linked to short-term (monthly) temporal changes of primary productivity. Multidimensional scaling analysis of prey and T. filippovae signature fatty acid profiles revealed apparent intra-specific predator to prey relationships. Significant season versus site interactions for various lipid classes and fatty acids were observed, further indicating that temporal dietary shifts are related to site-specific oceanography and ecosystem structure (prey composition and/or productivity). Comparing fatty acid profiles with other Southern Ocean squid species, interspecific similarities and differences in diet composition were evident. Results demonstrate that signature lipid profiling of squid can be used as a complimentary or even alternative and cost effective tool to examine key changes in prey-community structure and ecosystem productivity. Such knowledge is fundamental to better understanding the effects of environmental perturbations from fisheries, climate change and pollution.

Role of squid in the Southern Ocean pelagic ecosystem and the possible consequences of climate change

Southern Ocean squid are important predators and prey and are a potential fishery resource. Their future under climate change is analysed from predictions of change by 2100 and assessments of the effects on squid biology. There are ∼18 Antarctic species of squid. Young feed primarily on crustaceans and switch later to fishes. They are preyed on by odontocetes, seals and seabirds – which together consume ∼34×106tyr−1 – and fish. As predators, squid are second to fish as biomass producers but recent evidence suggests predator consumption of squid needs to be reassessed. Fatty acid composition and stable nitrogen isotope ratios indicate some predators consume less squid in their diet than gut contents data suggest. Southern Ocean oceanography is unique in having circumpolar circulation and frontal systems and at high latitudes it is heavily influenced by sea ice. The Antarctic Peninsula is among the fastest warming regions worldwide but elsewhere the Southern Ocean is warming more slowly and the Ross Sea is probably cooling. Sea ice is receding in the Peninsula region and increasing elsewhere. Modelled predictions for 2100 suggest although the Southern Ocean will warm less than other oceans and sea ice will reduce. The Antarctic Circumpolar Current may shift slightly southwards with intensification of westerly winds but resolution of the models is insufficient to predict mesoscale change. Globally, pH of seawater has decreased by 0.1 units since the mid-1900s and is predicted to decrease by another 0.5 units by 2100. Impact on calcifying organisms will be high in the cold Southern Ocean where solubility of calcium carbonate is high. Predicted temperature increases are unlikely to have major effects on squid other than changes in distribution near the limits of their range; acidification may have greater impact. Small changes in large scale circulation are unlikely to affect squid but changes in mesoscale oceanography may have high impact. Change in sea ice extent may not have a direct effect but consequent ecosystem changes could have a major impact. Cephalopods are ecological opportunists adapted to exploit favourable environmental conditions. Given their potential to evolve fast, change in the Southern Ocean pelagic ecosystem might act in their favour.

Species identification of &lt;i&gt;Ommastrephes bartramii, Dosidicus gigas, Sthenoteuthis oualaniensis&lt;/i&gt; and &lt;i&gt;Illex argentinus&lt;/i&gt; (Ommastrephidae) using beak morphological variables

Four oceanic squid species, Ommastrephes bartramii, Dosidicus gigas, Sthenoteuthis oualaniensis and Illex argentinus, not only support important commercial fisheries, but also play a vital role in their marine ecosystems. It is therefore important to identify them in the analyses of their predators’ stomach contents as this can yield critical information on the trophic dynamics of ecosystems. Hard beaks of the four species frequently found in their predators’ stomachs can be used to identify them. In this study, to remove the effect of size differences among individuals, measurements of upper and lower beaks were standardized with an allometric model. A discriminant analysis was carried out to compare morphological differences among the four species and between the sexes for each species. The upper rostral width and upper rostral length showed the greatest interspecific variation in the beak morphological variables of the four Ommastrephidae. The linear discriminant functions of beak morphological variables were developed for the four Ommastraphidae, which resulted in a rate of correct species classification of over 97%. Sexual dimorphism was also found in the beak morphology of O. bartramii and I. argentinus. This study suggests that morphological variables can be used to reliably classify Ommastrephidae at genus level, which can help identify the specie in the stomachs of cephalopod predators. This helps to improve the understanding of the role cephalopods play in their marine ecosystems.

Resolution of fine biological structure including small narcomedusae across a front in the Southern California Bight

We sampled a front detected by SST gradient, ocean color imagery, and a Spray glider south of San Nicolas Island in the Southern California Bight between 14 and 18 October 2010. We sampled the front with an unusually extensive array of instrumentation, including the Continuous Underway Fish Egg Sampler (CUFES), the undulating In Situ Ichthyoplankton Imaging System (ISIIS) (fitted with temperature, salinity, oxygen, and fluorescence sensors), multifrequency acoustics, a surface pelagic trawl, a bongo net, and a neuston net. We found higher fluorescence and greater cladoceran, decapod, and euphausiid densities in the front, indicating increased primary and secondary production. Mesopelagic fish were most abundant in oceanic waters to the west of the front, market squid were abundant in the front associated with higher krill and decapod densities, and jack mackerel were most common in the front and on the shoreward side of the front. Egg densities peaked to either side of the front, consistent with both offshore (for oceanic squid and mesopelagic fish) and shelf origins (for white croaker and California halibut). We discovered unusually high concentrations of predatory narcomedusae in the surface layer of the frontal zone. Potential ichthyoplankton predators were more abundant either in the front (decapods, euphausiids, and squid) or shoreward of the front (medusae, chaetognaths, and jack mackerel). For pelagic fish like sardine, which can thrive in less productive waters, the safest place to spawn would be offshore because there are fewer potential predators.

Factors influencing the embryonic development and hatchling size of the oceanic squid Illex coindetii following in vitro fertilization

Egg masses of oceanic squid accidently collected in the wild have been observed only from a few spawning events in aquaria, and as a consequence, the study of their embryos and hatchlings is very limited. Here, we used in vitro fertilization techniques to understand the abiotic factors that influenced egg development and hatchling performance of the ommastrephid squid Illex coindetii from the Mediterranean Sea. Egg and hatchling sizes of these ommastrephids are close to the minimum for cephalopod species, and therefore, short embryonic developmental periods were expected under a Mediterranean temperature regime. Low incubation densities and the use of antibiotics in the incubation medium resulted in relatively high survival rates to hatchling. Hatching time was inversely proportional to incubation temperature and ranged from 5 to 11days at 21°C and 13°C, respectively. The addition of oviducal jelly to the eggs immediately after fertilization, followed by another addition at the beginning of organogenesis, resulted in better chorionic expansion, with an increase in egg diameter, delayed hatching and higher hatchling weight, which suggests a better use of yolk reserves. Larger hatchlings in length and weight also tended to be produced at low temperature, probably also due to better yolk absorption. As this species spawns all year round, size differences between summer and winter hatchlings may be suspected. In vitro fertilization techniques used in the laboratory proved to be useful in shedding some light on the early life of this oceanic squid. Further research is needed to elaborate on tests to predict gamete quality and to develop methods to avoid premature hatching.