Small Squid Research Articles

Engine Fuel Consumption for Fishing Lights of Small Squid Jigging Boats

Engine Fuel Consumption for Fishing Lights of Small Squid Jigging Boats

Reactive probing of macroscopically quantum mechanical SQUID rings

In this paper we demonstrate that the energy level structure of ultra small capacitance SQUID rings can be probed adiabatically at radio frequency using both dynamical and quasistatic reactive techniques.

Thin-film dc SQUID gradiometer using a single YBa2Cu3O7−x layer

A dc SQUID gradiometer with a large effective pickup area using only a single YBa2Cu3O7−x layer and step-edge Josephson junctions on SrTiO3 substrate has been prepared. The planar gradiometer consists of two loops coupled directly to a small area SQUID in the center of the structure. The main advantage in comparison to magnetometers is the possibility of direct measurements in a magnetically unshielded environment. At 77 K without bias reversal technique we obtain a white noise level of about 4.5×10−5 Φ0 Hz−1/2 or 8×10−13 T cm−1 Hz−1/2 down to 10 Hz. At 1 Hz noise increases up to 6×10−12 T cm−1 Hz−1/2.

Growth and reproduction in the mesopelagic-boundary squid Abralia trigonura

Abralia trigonura is a small squid that is an important member of the mesopelagic boundary community around Hawaii. Squids were aged by examining statolith growth increments, and various reproductive parameters were measured. Female longevity is ∼6 mo, and they become sexually mature at ∼3.5 mo. Male longevity is the same, but they become sexually mature at ∼2.5 mo. This species appears to be a multiple spawner, and peculiarities in the number of eggs found in the oviducts suggests that they spawn every few days. Possible advantages of this reproductive mode are examined.

Evaluation of the diet of Sowerby's beaked whale, Mesoplodon bidens, based on isotopic comparisons among northwestern Atlantic cetaceans

Sowerby's beaked whale, Mesoplodon bidens, is a poorly known and infrequently encountered species. Consequently, its behavior and habitat requirements are largely unknown. Evidence of the trophic level and diet of M. bidens was obtained through a comparison of δ13C and δ15N values for this species with those for eight other cetaceans and the basking shark, Cetorhinus maximus. The δ13C value for M. bidens (−18.5 ± 1.1‰) was similar to that for all other cetaceans (−18.7 to −17.2‰) except the sperm whale, Physeter macrocephalus, and the blue whale, Balaenoptera musculus (−22.8 and −20.1‰, respectively). At least a portion of the range of δ13C values for the cetaceans and the basking shark is thought to be related to variations in the lipid content of the samples. Nitrogen isotope values appear to reflect trophic position. Based on δ15N, organisms can be ordered along a trophic continuum bracketed by the planktivorous basking shark (9.9‰) and the piscivorous white-beaked dolphin, Lagenorhynchus albirostris (16.2‰). The trophic position of M. bidens (δ15N = 11.7‰) is intermediate between those of the pygmy sperm whale, Kogia breviceps (δ15N = 11.9‰), and the sperm whale, Physeter macrocephalus (δ15N = 11.1‰), and thus supports previous suggestions that these species feed at similar trophic positions. The estimated δ15N value of the diet of M. bidens, 8.7‰, is consistent with a diet that has a large contribution from small offshore squid, δ15N = 9.3‰.

Mechanisms of glutamate activation of axon-to-Schwann cell signaling in the squid

Membrane potentials from Schwann cells associated with giant axons of the small squid ( Alloteuthis and Loliguncula) and the large squid ( Loligo) were monitored with glass microelectrodes following 100 Hz/15 s axonal stimulation, or the application of 10 −7 M glutamate and ion substitutions, in the presence or absence of 10 −7 M d-tubocurarine. Glutamate or stimulation caused the membrane of the Schwann cell to depolarize to approximately −32 mV. This was rapidly replaced by a transient hyperpolarization to approximately −55 mV; the potential returning to the resting level (−40 mV) in approximately 7 min. In the presence of d-tubocurarine only the initial depolarization was evident. Nominally zero [Na +] o or treatment with 10 −7 M tetrodotoxin (in normal [Na +] o) blocked the stimulation-and glutamate-induced depolarization while low Cl o − hyperpolarized the Schwann cell without effect on the glutamate- or stimulation-induced depolarization. Na o + depletion or pretreatment with tetrodotoxin in normal Na o + did not affect the development of the Schwann cell hyperpolarization. These results do not support the hypothesis that the glutamate-induced depolarization is the trigger leading to the Schwann cell hyperpolarization. Preliminary experiments to test the possibility that inositol phosphate second messenger and an increase in [Ca 2+] i are triggered by glutamate receptor activation showed that nominally 0 Ca o 2+/75mM Mg o 2+ only slightly reduced the hyperpolarizing response to stimulation or glutamate while intracellular Bapta (20–30 μM) blocked the hyperpolarization but not the depolarization. [ 3H]Myoinositol incorporation into axon-Schwann cell plasma membranes was high. Treating the preparation for a period of 1–10 min with the glutamate receptor antagonist, 2-amino-4-phosphono-butyrate (10 −5 M), in the presence of glutamate reduced membrane [ 3H]myoinositol content to 45% of control. These observations are consistent with a glutamate-activated Na + channel for the initial depolarization and an independent inositol phosphate second messenger-Ca 2+-dependent triggering event for the development of the Schwann cell hyperpolarization.

Evaluating the performance of light traps for sampling small fish and squid in open waters of the central Great Barrier Reef lagoon

Evaluating the performance of light traps for sampling small fish and squid in open waters of the central Great Barrier Reef lagoon

但馬沖中層型浮魚礁周辺の昼間の魚影分布について

Three mid-layer floating reefs made of steel were deployed at a depth of 80-90m off Tajima in the Japan Sea in May 1987. To examine the distribution of fish around the reefs, an acous-tic survey over a 3×2km area, 70-110m in depth, and ROV observations were carried out during the daytime in May and August, 1988. Around the mid-layer reefs, Navodon modestus and Trachurus japonica were observed. Sol-itary Navodon modestus were close to the reef (within 10m) in the daytime, and were thought to settle on the reef at night. As Trachurus japonica, observed in August, was distributed around the floating reefs and a sunken ship in dense small schools, they were not seen else-where in the survey area. The mid-layer floating reef was concluded to act as a schooling ground for Trachurus japonica in the daytime. In May, many scattering fish echoes, which were thought to be a mixture of small squid, pelagic crustacea and others, were distributed over the whole survey area. They stayed around the reef twice-a scattering fish echo stayed at the bottom layer around the reefs for more than few hours, and a dense fish school stayed beneath the mid-layer reef for a short dura-tion. These phenomena were concluded to show an attraction and detention function of the mid-layer floating reef.

Distribution and morphological characters of immatureMartialia hyadesi(Cephalopoda: Oegopsida) in New Zealand waters

Abstract Before 1985, Martialia hyadesi (Cephalopoda: Ommastrephidae) in the Pacific Ocean was known only from the Eltanin Fracture Zone and Macquarie Island. A joint Japan‐New Zealand squid survey around New Zealand captured many immature ommastrephid squids. Gel electrophoresis confirmed the presence of immature M. hyadesi. Aspects of the external morphology are described. The distinctive tentacle club was evident in the smallest specimen examined, 19 mm dorsal mantle length (ML). Arm trabeculae were first evident in specimens of 40–50 mm ML. Immature squid were distributed around and southward of the Subtropical Convergence Zone. The presence of very small squid (< 10 mm ML) indicated spawning on or near the Auckland Island Shelf.

Evidence that glutamate mediates Axon‐to‐Schwann cell signaling in the squid

High-frequency stimulation (100 Hz) of isolated giant axons of the small squid Alloteuthis subulata and the large squid Loligo forbesi caused the periaxonal Schwann cell resting potential (Em = -40 mV) to hyperpolarize up to 11 mV in direct proportion to train duration and action potential amplitude. In both species, the Schwann cell also hyperpolarized up to 17 mV with the application of L-glutamate (10(-9) to 10(-6) M), in a dose-dependent manner. By contrast, in the presence of 10(-8) M d-tubocurarine (d-TC) to block the cholinergic component of the Schwann cell response, Schwann cells depolarized 8-9 mV during electrical stimulation of the axon or application of L-glutamate. In the presence of 10(-5) M 2-amino-4-phosphonobutyrate (2-APB), the hyperpolarization to glutamate and to axon stimulation was blocked, whereas the cholinergic (carbachol-induced) hyperpolarization was unaffected. In experiments with Alloteuthis, L-aspartate (10(-7) M) also caused a Schwann cell hyperpolarization, but this was not blocked by 2-APB. In tests with glutamate receptor agonists and antagonists, quisqualate (10(-5) M) produced a hyperpolarization blocked by 10(-4) M L-glutamic acid diethylester (GDEE), which also blocked the response to axonal stimulation. Kainic acid (10(-4) M) also caused a hyperpolarization, but n-methyl-D-aspartate (NMDA; 10(-4) M), ibotenate (10(-5) M), alpha-amino-3-hydroxy-5-methyl-isoxazole proprionate (AMPA; (10(-4) M), and isethionate (10(-5) M) had no effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Respiratory and Cardiac Performance inLolliguncula Brevis(Cephalopoda, Myopsida): The Effects of Activity, Temperature and Hypoxia

ABSTRACTLolliguncula brevis Blainville is a small euryhaline squid found at temperatures between 11 and 31 °C. Changes in heartbeat and ventilation frequencies were observed throughout this temperature range and under a variety of conditions, including acute hypoxia and swimming by jet propulsion in a tunnel respirometer. Resting showed a Q10 of 1·47, and heart rate and ventilation rate Q10 values of 1·92 and 1·73, respectively; oxygen uptake could exceed 1·01kg−1h−1 at 30°C even at rest. The squids regulated their oxygen uptake at all temperatures. Oxygen extraction rates were in the region of 5-10% in saturated water, increasing to 15-20% in hypoxic water or after exercise. One effect of this variability is that ventilation stroke volume can remain constant throughout the range of temperatures and oxygen concentrations that the animal is likely to encounter, a necessary condition since the ventilation stream is also the principal mode of locomotion by jet propulsion. Blood oxygen-carrying capacity (from the copper concentration) was 4·6 ± 1·8 vols%. Cardiac output and stroke volume were estimated from the observed values and heartbeat frequencies. Resting at 25°C, the output was close to ll-51kg−1bodymassh−1. The systemic heart of Lolliguncula weighed only 2·06 ± 0·62 g kg−1. In exercise the cardiac output must exceed 14x 1031kg−1 heart mass h−1, pumping more than the heart’s own mass of blood at each stroke.

Periaxonal K+ regulation in the small squid Alloteuthis. Studies on isolated and in situ axons

A novel giant axon preparation from the squid Alloteuthis is described. Properties of in situ and isolated axons are similar. Periaxonal K+ accumulation is a function of the physiological state of the animal and of the axon and its sheathing layers. Carefully dissected isolated axons, and axons in situ in a healthy mantle, show much less K+ accumulation than previously reported in squid. It is suggested that the Schwann cells are involved in the observed K+ regulation.

Fabrication and properties of 1 µm&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt;edge junctions

We describe the construction and characteristics of Nb/Nb 2 O 5 /Pb In edge junctions which are intended primarily for use in DC SQUIDs. Our aim has been to make junctions as small as possible whilst using conventional optical lithography and lift-off techniques. The base electrode for these junctions is an anodised layer of Nb, which is patterned by reactive ion etching to produce angled edges on which the junctions are formed. The tunnel barriers are grown by RF plasma oxidation using 5% O 2 in Ar. A series of test junctions with areas between 1 and 10 μm2has been made to establish the necessary oxidation conditions, which have been found to be markedly different from those needed for the formation of barriers for window junctions. To measure the junction capacitance, we have made small unshunted SQUIDs with self inductances ranging between 3 and 10pH, and from the effect of resonances on their current-voltage (I-V) characteristics and their periodic response to current injected through the structure, we determine the junction capacitance to be 0.22±0.01pFμm-2, at a critical current density of 15 × 103Acm-2We have incorporated similar junctions in simple magnetometer-style SQUIDs of InH inductance, and for these we measure the flux noise as 8 × 10-6φ o Hz-1/2in the white noise region. These junctions will also be used in more complex SQUIDs which have spiral input coils, and, based on present measurements, we expect these to have a current sensitivity of less than 0.2pAHz-1/2

銚子沖産小型ツノザメ類３種の生息水深と食性

Three species of small deep-sea squaloid sharks, Etmopterus lucifer, E. unicolor and Centro-scyllium ritteri, were examined to study their vertical distribution and feeding habits on the basis of specimens collected from the continental shelf and upper slope off Choshi, located at the Pacific coast of Japan. E. lucifer inhabited the shallowest (mean depth range 200-300m) waters among the three species whereas E. unicolor lived in the deepest waters (mainly in 450-850m depth). E. lucifer showed an increase in depth with growth, Sex ratios by depth varied from species to species. Males always outnumbered females in E. lucifer. Stomach content analysis for E. lucifer demonstrated that small squids (mostly Watasenia scintillans) were the most important prey and that fish (mainly myctophids) were next in importance. Food items of E. unicolor con-sisted mainly of Watasenia scintillans, myctophids and Natantia (Acanthephyra sp.). Euphausiids were the main food items constituting 97% of the total number of the prey in C. ritteri. On the other hand, fishes showed high frequency of occurrence in stomach contents of C. ritteri although they were not of importance in numbers. In E. lucifer, the dietary importance of crustaceans like euphausiids decreased with size and as they grew larger, they tended to feed on squids and fishes. From the above observations food overlaps among these three species are considered to be low.

The food and feeding of seven fish species from the Campbell Plateau, New Zealand

Abstract The food and feeding habits of hoki (Macruronus novaezelandiae), southern blue whiting (Micromesistius australis), javelin fish (Lepi‐dorhynchus denticulatus), ling (Genypterus blacodes), smooth rattail (Coelorinchus aspercephalus), silverside (Argentina elongata), and small‐scaled notothenid (Notothenia microlepidota) sampled from the Campbell Plateau in 1979 were examined. The importance of prey items in the diet has been assessed by an ‘index of relative importance’, which combines measurements of frequency of occurrence, number, and weight of prey. Hoki, southern blue whiting, and javelin fish are pelagic feeders. Hoki preyed largely on natant decapod crustaceans, amphipods, and myctophid and photichthyid fishes. The main prey of southern blue whiting were amphipods, natant decapods, and euphausiids. Javelin fish fed on natant decapods, amphipods, and small squid. Seasonal and regional differences in feeding, and dietary changes with length of fish were evident. Ling, smooth rattail, silverside, and small‐scaled notothenid are predominantly benthic feeders. Ling preyed on natant decapods, macrourid fishes, and small hoki. The diet of rattail comprised natant decapod crustaceans, opal fishes (Hemerocoetes spp.), and poly‐chaetes. Silverside fed almost solely on salps. Salps, amphipods, brachyuran crustaceans, and opal fishes were the main prey of small‐scaled notothenid.

Christmas Island birds returning

Six months after their mass exodus, birds are beginning to return to Christmas Island. Roughly 17 million birds, almost the entire adult bird population, either perished or fled their mid‐Pacific atoll home last autumn, leaving behind thousands of nestlings to starve (Eos, April 5, 1983, p. 131). It is believed that the strong El Niño altered the ecology of the surrounding waters and forced the birds to flee. Christmas Island is the world's largest coral atoll.“Ocean and atmosphere scientists are unsure of future directions for the El Niño conditions and cannot now predict what will happen to the birds in the coming months,” said Ralph W. Schreiber, curator of ornithology at the Natural History Museum of Los Angeles County in California. Heisthe ornithologist who discovered the disappearance. “The recovery of the bird populations depends on the food supply in the waters surrounding the island.” The island's birds feed exclusively on small fish and squid.

Luminescent flashing in the midwater squids Pterygioteuthis microlampas and P. giardi

The luminescent flashing capabilities and swimming behavior were examined for two species of small midwater squids (Pterygioteuthis microlampas and P. giardi). Recently captured squid were placed in a small aquarium, where their movements and luminescent flashes could be recorded with an image intensifier, a photomultiplier tube and associated equipment. Flashing behavior was initiated by disturbing the squid with an eletrical shock. The following 4 behaviors were observed: (1) a short flash and a rapid departure from the electrode; (2) a short flash and a delayed, slow departure from the electrode; (3) a longer flash persisting after a rapid departure from the electrode; (4) a longer flash when departure was prevented by continuing the shock. Luminescent flashes probably have a general defensive function, discouraging or disrupting an attack by potential predators, and within this context there may exist numerous strategies involving flashes.

Population dynamics and feeding ecology of juvenile Australian salmon (Arripis trutta) in Westren Port, Victoria

Juveniles (0 + age group) of both subspecies of the Australian salmon were captured over eelgrass meadows in Western Port at various times between October 1974 and February 1976. The western subspecies and the eastern subspecies were present from August through April, and December through May, respectively. The western subspecies always fed on benthic-dwelling prey including fishes, crabs and shrimps, and the eastern subspecies fed on prey which inhabited the water column (crustacean larvae, insects and epitokous polychaetes) in December but switched to benthic-dwelling prey (fishes, small squid, benthic crustaceans and polychaetes) in May. The role of different gill-raker number and morphology in effecting dietary separation of the subspecies is unclear.

Species diversity and size ranges of cephalopods in the diet of jackass penguins from Algoa Bay, South Africa

An analysis of cephalopod remains collected from jackass penguin Spheniscus demersus regurgitations and stomachs at St Croix Island, Algoa Bay, in 1976 and 1977 revealed the presence of three cephalopod species. Most common was Loligo reynaudi, with Heterotuthus sp. and Argonauta argo constituting trace items. Beak measurements were used to estimate dorsal mantle lengths and wet masses of cephalopods taken by penguins. The dominant cephalopod taken by penguins was the same species as that harvested by commercial fisheries. Despite an overlap in the size range of squid taken by penguins and trawlers, penguins tended to take smaller squid and did not take the larger squid landed by trawlers. The seasonal occurrence of squid in the penguin diet in 1976 and 1977 was the opposite of the abundance of squid in the area as reflected by trawler landings. This is explained in terms of the abundance and preference for other prey items. It is suggested that penguins take fish in preference to squid because of the rel...

THE FOODS OF GREAT AND SOOTY SHEARWATERSPUFFINUS GRAVISANDP. GRISEUSIN EASTERN CANADIAN WATERS

SummaryThe foods of Great and Sooty ShearwatersPuffinus gravisandP. griseusare described from birds collected off eastern Canada. There was a broad overlap in diet, but Great Shearwaters tended to take more squid and tough‐bodied fish such as mackerelScomber scombruswhile Sooties took more euphausiidsMeganyctiphanes norvegicaand soft‐bodied fish such as HerringClupea harengus. These differences are apparently related to differences in bill structure and in the degree of adaptation to underwater swimming.The birds appeared to feed opportunistically on whatever prey was locally available in the size‐range between euphausiids and small fish and squid:Meganyctiphanesoff southwest Nova Scotia, spawning and post‐spawning capelinMallotus villosusoff eastern Newfoundland, and migrating squidIllex illecebrosuson the Grand Bank. Possible factors influencing prey selection are discussed. It is suggested that the timing and routes of the birds' migrations in the North Atlantic are related to the exploitation of such local concentrations.Despite the overlap in diets, differences in the distributions of the two species rule out the possibility of significant competition for common food resources.