Small Squid Research Articles

Towards unlocking the trophic roles of rarely encountered squid: Opportunistic samples of Taningia danae and a Chiroteuthis aff. veranii reveal that the Southern Ocean top predators are nutrient links connecting deep-sea and shelf-slope environments

Deep-sea squids are presumably vital components of largely undescribed marine ecosystems, yet limited access to specimens has hampered efforts to detail their ecological roles as predators and preys. Biochemical techniques such as stable isotope analyses, fatty acid analyses, and bomb calorimetry are increasingly recognized for their ability to infer trophic ecology and dietary information from small quantities of tissue. This study used five opportunistically collected Taningia danae specimens and one Chiroteuthis aff. veranii specimen retrieved from the Great Australian Bight, South Australia, to detail the trophic ecology of these poorly understood squids. Four body tissue types (i.e., arm, buccal mass, mantle, and digestive gland) were assessed for their utility in stable isotope (SI) and fatty acid (FA) analyses, and we found that the arm, buccal mass, and mantle tissues had similar SI and FA profiles, suggesting that they can be used interchangeably when the entire specimen is unavailable. δ13C, δ15N, and fatty acid data suggests that the T. danae and C. aff. veranii specimens lived in the Southern Ocean and were high-trophic-level predators, feeding on deep-sea fishes and small squids, while also taking advantage of the summer upwelling region of the Great Australian Bight. The fatty acid analysis and bomb calorimetry results indicate that these squids might be important reservoirs of essential FAs (EPA and DHA) for Southern Ocean predators and that the whole-body energy content of T. danae individuals can reach up to 362,250 kJ. Our findings indicate that these squids may be contributing greatly to the transport of nutrients and energy between the Southern Ocean deep-sea and the Great Australian Bight shelf–slope environments. In addition to building our understanding of the trophic ecology of two poorly understood deep-sea squids, these findings also highlight the utility of partial specimens and demonstrate the important ecological information that can be obtained from few samples that may be opportunistically collected.

Geographical and species differences of fatty acid components of small pelagic fishes, micronekton, and squids in the northwestern pacific

Geographical and species differences of fatty acid components of small pelagic fishes, micronekton, and squids in the northwestern pacific

Design of a High-Tc SQUID Planer Gradiometer and Evaluation of Sensitivity Distribution

When using SQUID magnetic sensors to inspect metallic contaminants in magnetic matrices, such as battery components, it is advantageous to use a gradiometer rather than a magnetometer because a higher signal-to-noise ratio can be obtained. In this study, we reviewed the design of directly coupled SQUID gradiometers and optimized their pickup loops. Several gradiometers with pickup loops of different sizes were fabricated. To evaluate these gradiometers, we applied a small magnetic field produced by a magnetic field coil with a small diameter (effective diameter: 0.65 mm) to them. The sensitivity distribution of these gradiometers was evaluated using a special mechanism that allows for complete scanning over the device substrate. As a result, the magnitude of the peak value could be explained by an inductance imbalance between the pickup loop and the SQUID. Finally, we could find the optimal pickup coil design conditions. Furthermore, we could capture the sensitivity distribution of a small SQUID loop placed in the center of the device.

Life History Patterns of the Atlantic Brief Squid, Lolliguncula brevis (Blainville, 1823), in the Charleston Harbor Estuary, South Carolina, USA

The Atlantic brief squid, Lolliguncula brevis, is a euryhaline cephalopod that inhabits shallow, continental shelf habitats from Argentina to the Bay of Fundy. In the southeastern United States, brief squid can account for a considerable portion of the estuarine animal biomass and are an important component of the diets of species with high priority for management and conservation. Historical data from South Carolina Department of Natural Resources suggest that brief squid exhibit spatially and temporally variable size-frequency distributions within the Charleston Harbor estuary. Prior to this study, however, detailed life history information for this species was lacking in the region. Samples of brief squid were collected monthly at four stations along a salinity gradient within the Charleston Harbor estuary in 2019 to investigate temporal and spatial patterns of abundance, sex, size, and maturity. Season and station were significantly related to brief squid abundance, which was greater for all sexes in spring, summer, and fall than in winter. Catches of brief squid were dominated by immature squid compared with mature squid. Excluding sexually indistinct squid, and across all seasons, significantly more males were collected than females. Mean brief squid size tended to be larger in May than in several other months of the year, largely due to the lower abundance of small squid in that month. Logistic regression analyses indicated that brief squid size-at-maturity occurred at 50.2 mm for males and 59.2 mm for females. The presence of both small and large brief squid throughout the year at all stations supports a pattern of overlapping cohorts, whereas the continual presence of immature brief squid at all stations suggests asynchronous recruitment. This study provides valuable life history information that can be used to support the conservation and management of organisms that are either prey or predators of brief squid within the Charleston Harbor estuary. Further research over multiple years and within other estuaries in the Georgia Bight is needed, however, to determine how the life history patterns observed in this study apply more broadly across the region.

GROWTH IN HERD FORM AND FOOD SPECTRUM OF REEVE’S CROAKER Chrysochir aureus (Richardson, 1846)

A study on growth and food spectrum of Reeve’s croaker was carried out from June 2021 to January 2022 in the coastal areas from Soc Trang to Bac Lieu provinces. Fish samples were collected monthly by bottom trawl.Fish stomachs were fixed in a 4% formol solution to prevent feed items from being digested in the stomach. The analysis of 198 male and 215 female samples showed that the total length (L) and body weight (W) of the fish had a regression relationship according to the equations Wmale = 0.0064L3;1425 and R2= 0.9735 (totallength ranged 14.0 – 40.0 cm) and Wfemale = 0.00463:2425 and R2 = 0.9504 (total length ranged 13.5 – 41.0 cm). The relative length of the gut (RLG) < 1 (RLG = 0.08 ± 0.02 cm in immature fish and RLG = 0.08 ± 0.04 cm in mature fish),indicated that Reeve’s croaker was a carnivorous fish. Many individuals in the population haveno food in their stomachs. The immature fish eat three types of food (small fish, shrimp and other food) while mature fish eat six types of food (small fish, shrimp, squids, crabs, nereid and other food). The feed spectrum of immature fish was narrower than that of mature fish.

Acoustic seascape partitioning through functional data analysis

AbstractAimWater column acoustic backscatter is regularly registered during oceanographic surveys, providing valuable information on the composition and distribution of pelagic life in the ocean. We propose an objective approach based on functional data analysis to classify these acoustic seascapes into biogeographical regions.LocationTropical South Atlantic Ocean off northeastern Brazil.TaxonSound‐scattering pelagic fauna detected with acoustic echosounders, principally small fish, crustaceans, squid and diverse gelatinous life‐forms.MethodsWe use acoustic backscatter as a function of depth, simultaneously at three frequencies, to numerically describe the vertical distribution and composition of sound‐scattering organisms in the water column. This information is used to classify the acoustic seascape through functional principal component analysis. The analysis routine is tested and illustrated with data collected at 38, 70 and 120 kHz in waters affected by contrasting environmental conditions.ResultsAcoustic seascape partitioning mirrored the distribution of current systems, fronts and taxonomically based regionalization. The study area was divided between slope‐boundary and open‐ocean waters, and between spring and fall hydrological regimes.Main ConclusionsThe acoustic seascape consistency and the spatiotemporal coherence of the regions classified show that the method is efficient at identifying homogeneous and cohesive sound‐scattering communities. Comparisons against hydrological and biological regionalization prove that the method is reliable at delineating distinct pelagic ecosystems in a cost‐efficient and non‐intrusive way.

Influence of migratory route on early maturation of swordtip squid, Uroteuthis edulis, caught off western Kyushu Island, Japan

Mature female Swordtip squid (Uroteuthis edulis) of ca. 100 mm mantle length are found in Tachibana Bay (western Kyushu, Japan) from June to August, although many mature females caught in the eastern Tsushima Straits (the entrance to the Japan Sea) are over ca. 150 mm. To reveal the cause for the difference, statolith analyses and Lagrangian tracer experiments were conducted. The results show that the small mature female squid would have hatched in the southern East China Sea in winter and migrated to the Sea of Amakusa via the Kuroshio Current, as also would many squid caught in the eastern Tsushima Straits. The two major differences between them were found to be the history of their empirical water temperature (estimated from the ratio of Strontium to Calcium in the statoliths) and the depth of the waters where they were caught. The small mature females would have experienced water temperatures rising from 18° to 20°C in the coastal waters off Kyushu, probably over 16 °C even at the bottom layer, for one month or more before being caught. Considering also the results from previous research, a hypothesis is proposed that, after reaching the minimum age of maturity, the squid could begin (and continue) to mature when the water temperature in the bottom layer (or in the deepest zone to which this species can dive) exceeds ca. 16 °C, and take about one month to reach full maturity. The method used here to explain the size differences detected among siblings born in the same locality but following migratory paths with very different temperature conditions is a useful and the results also suggest another small mature squid that appear in the southern East China Sea in spring may migrate from the warmer waters, which can be contributed to the stock management of this species.

Dietary shifts and niche partitioning throughout ontogeny reduce intraspecific competition in a pelagic generalist predator

Patterns of feeding strategy change throughout ontogeny according to size-specific abilities and requirements. Characterizing the extent and potential repeated occurrence of dietary differences within the population can improve understanding of the intraspecific predation regime and population dynamics. Here, we investigated size-related feeding habits and trophic niche partitioning of an iconic pelagic generalist predator, the jumbo squid Dosidicus gigas, by a combined analysis of morphologic indicators of feeding capability (fin and feeding apparatuses), trophic biochemical tracers (stable isotopes and fatty acids), and stomach contents. Results showed significant variation in prey composition, isotopic values, and fatty acid profiles with size. D. gigas exhibited a shift in diet at approximately 250 mm mantle length (ML). The trophic niche of small (ML ≤ 250 mm) and large (ML > 250 mm) squid revealed low potential for resource overlap, suggesting segregation in terms of spatial and food resources of different size groups. Large individuals tend to feed deeper and on smaller prey to optimize food capture costs and energy benefits. This feeding strategy is likely related to variability in the development of feeding capacity, increasing swimming ability, and metabolic demand as squid grow and may reduce intraspecific competition to improve survival. These results highlight the dietary flexibility of D. gigas and demonstrate that niche differentiation acts as a major factor in a cohort, which may have important implications for their population dynamics and management. In addition, this study demonstrates that using multiple diet tracers can highlight subtle differentiations in diet correlated to growth in a pelagic generalist predator.

Size-related, seasonal and interdecadal changes in the diet of the Patagonian longfin squid Doryteuthis gahi in the South-western Atlantic

AbstractThe Patagonian longfin squid Doryteuthis gahi has an annual life cycle with two seasonal cohorts (autumn and spring spawners). Earlier studies on the Patagonian shelf found a predominance of Euphausiacea in the D. gahi diet, but no studies to date have investigated differences between feeding spectra of the two cohorts or decadal diet shifts. The present study investigated differences in diet of D. gahi on the Patagonian shelf sampled two decades apart, and differences between seasonal cohorts. Classical stomach content analysis and generalized additive models were used to investigate and model the influence of mantle length, sampling period and spawning cohort on the diet. Results revealed an ontogenetic diet change from ~70% Frequency of Occurrence of Euphausiacea in small squid to more than 60% FO of fish and Cephalopoda at larger sizes. Cannibalism was also frequently observed. Euphausiacea were ingested more frequently and in higher amounts during the austral summer and therefore were consumed more by the autumn spawning cohort, whereas fish was more frequently fed upon during austral winter and also by the spring spawning cohort. Cannibalism was also recorded more in austral winter months but, contrary to feeding on fish, was more prevalent in the autumn spawning cohort. Increased predation of Munida gregaria was observed in 2020 compared with 2001. This study is an important step towards improving the knowledge of D. gahi's two seasonal cohorts, providing data that can be used for future ecosystem modelling.

Feeding ecology of juvenile Pacific bluefin tuna

The feeding ecology of juvenile Pacific bluefin tuna (PBF) Thunnus orientalis in the Sea of Japan was examined to better understand the survival process before fishery recruitment. Stomach content analysis showed that the main prey items were fish, especially Japanese anchovy Engraulis japonicus, cephalopods, mainly small squid Enoploteuthis chunii, and copepods. In addition, although both fish prey and cephalopods were important for large juveniles (100–300-mm fork length, FL), the stomach contents of small juveniles (40–99 mm FL) mainly included fish prey. The strong possibility of cannibalism was also suggested, although its contribution to total food consumption was limited. The size of fish prey increased significantly with the FL of PBF. Nitrogen isotope ratios (i.e. δ15N) also increased with increasing FL (12–227 mm), suggesting that the trophic level increases rapidly during the juvenile stage because of the active feeding on fish by PBF. Such feeding habits, especially feeding on fish, would be essential to achieve a high growth rate and would therefore be associated with the survival of juvenile PBF before recruitment in the Sea of Japan. In addition, PBF exhibited a decrease in stomach fullness during the night-time, and their estimated gastric evacuation rate was 0.36 h–1.

Prey-Related Asphyxiation in Harbor Porpoises (Phocoena phocoena) along the U.S. West Coast: Importance of American Shad (Alosa sapidissima) on Adult Female Harbor Porpoise Mortality

Harbor porpoise (Phocoena phocoena) diets are predominantly comprised of small fish species (<30 cm) and squid. However, predation on larger species (up to 63 cm) occurs, raising the question of increased risk of asphyxiation associated with this behavior. Literature was reviewed and stranding data from 1983 to 2020 from the U.S. West Coast (including California, Oregon and Washington) were searched for cases of prey-related asphyxiation of harbor porpoises and analyzed in relation to age, sex, reproductive status and prey species. Twenty-nine cases were documented. Twenty-seven cases involved large prey; non-native American shad caused the asphyxiation in 87% of the cases where the prey species was identified. The majority (92%) of harbor porpoises were females, and at least 83.3% were pregnant or recently post-partum. Reproductively active females may be more likely to attempt potentially risky behavior in order to compensate for their increased energetic needs. Increasing numbers of non-native American shad may pose a unique danger in this region for harbor porpoises not adapted to deal with the challenges of that prey. This may be a cause for concern, as there is likely an interaction between location, age and reproductive status on the diet composition and foraging strategies of harbor porpoises.

Komposisi Hasil Tangkapan dan Tingkat Keramahan Jala Cumi (Cast Net) di PPN Kejawanan Cirebon Jawa Barat

Pelabuhan Perikanan Nusantara (PPN) Kejawanan Cirebon berada di bagian Timur Jawa Barat, merupakan pelabuhan tipe B yang didominasi oleh kapal dengan alat tangkap jala cumi (cast net) dengan jumlah sebanyak 123 unit kapal. Tujuan dari penelitian ini adalah manganalisis komposisi hasil tangkapan dan tingkat keramahan alat tangkap jala cumi (cast net) berdasarkan komposisi hasil tangkapan utama dan sampingan. Pengumpulan data dilakukan melalui wawancara dan survei. Data hasil tangkapan ikan dikumpulkan dari unit alat tangkap jala cumi (cast net) sebanyak 10 (sepuluh) unit kapal pada tahun 2018. Analisis data meliputi komposisi jenis hasil tangkapan dan tingkat keramahannya. Hasil penelitian menunjukan bahwa alat tangkap jala cumi (cast net) dengan komposisi hasil tangkapan didominasi oleh cumi-cumi sebesar 97% dan sisanya sebanyak 3% terdiri dari ikan lemuru, layang dan teri. Adapun ukuran hasil tangkapan cumi-cumi yang didaratkan di PPN Kejawanan Cirebon memiliki ukuran dengan kategori cumi besar 27-30 cm dengan jumlah total 79.324,64 kg dan cumi ukuran kecil 1-7 cm dengan jumlah total 18.411,29 kg. Nilai tingkat keramahan lingkungan pada alat tangkap jala cumi (cast net) diperoleh dengan jumlah nilai total 30. Berdasarkan nilai tersebut maka alat tangkap jala cumi (cast net) dikategorikan sebagai alat tangkap yang sangat ramah lingkungan.

Brachioteuthis beanii Verrill, 1881 (Cephalopoda: Brachioteuthidae) in the northwest Atlantic

Four research cruises to the Gully Marine Protected Area (known as "the Gully") off Nova Scotia, Canada (2007–2010) collected 1454 specimens of the oegopsid squid family Brachioteuthidae. All specimens were identified as Brachioteuthis beanii, and the 842 individuals collected in 2007 were used to describe the morphology and ecology of the species. A subset of 565 specimens were measured for population size distribution, and over 200 of these individuals (21–117 mm ML) were fixed, vouchered, measured, dissected, and sexed to examine the internal and external characters of juveniles, males, and females. Specimens <40 mm ML were almost entirely juveniles. Specimens 40–49 mm ML were a mix of juveniles, males, and females. The smallest specimens, where the spermatophoric complex and nidamental glands could be identified, were approximately 39 mm ML in both males and females, suggesting that maturation begins at roughly the same size in both sexes. Specimens >50 mm ML could be sexed based solely on the color and texture of the mantle. Male mantles were fusiform in shape with few small, widely spaced chromatophores and a reticulated net on the mantle that developed concurrent with the internal spermatophoric complex. Females had a flaccid mantle with larger and denser chromatophores on the mantle and head and no external ornamentation (i.e., ridges or nodules). Measurement data showed that males had slightly larger arms and wider fins than females. The high abundance of B. beanii at the Gully in August/September may be a spawning aggregation and suggests that this small squid is an important component of the canyon food web.

Got Squid? Changes in the Ecological State of the Gulf of California Since the 1940 Steinbeck-Ricketts Expedition with a Focus on Humboldt Squid

Got Squid? Changes in the Ecological State of the Gulf of California Since the 1940 Steinbeck-Ricketts Expedition with a Focus on Humboldt Squid W. F. Gilly (bio), Unai Markaida (bio), Carlos Robinson (bio), and Bilin Liu (bio) Introduction Although the exact number of invertebrate species collected by Steinbeck and Ricketts in conjunction with the 1940 Sea of Cortez expedition on the Western Flyer is uncertain (Brusca, this volume), it is clear that the number of cephalopod species observed was small—fewer than 1% of the species collected. In particular, Dosidicus gigas, the Humboldt or jumbo flying squid, was apparently not seen during the expedition. This stands in contrast to the remarkable ease with which this species was observed north of Santa Rosalía in the Guaymas Basin region of the Gulf of California during a 2004 retracing of the 1940 expedition during the same time of year and using the same type of vessel and similar observational methods (Sagarin et al. 2008). Dosidicus is a monocyclic, short-lived species that matures only once at a broad size range. During favorable years, large squid prevail and commonly reach a mantle length (ML) of >60 cm and a mass of 20 kg or more at maturity, with a life span of 1.5–2.0 years in the Sea of Cortez (Hoving et al. 2013). [End Page 411] Large squid of this sort supported the third- or fourth-largest commercial fishery in Mexico for the decade preceding the 2004 trip, with the vast majority of landings coming from the Guaymas Basin area (Rosa et al. 2013). These factors made it hard for even a casual observer in the Central Gulf to be unaware of Dosidicus gigas between 1995 and 2009. It thus seems that large Humboldt squid were likely not to have been abundant in the Gulf of California in the spring of 1940, and reasons for the apparent change in the status of Humboldt squid since that time have been discussed without reaching any firm conclusion (Sagarin et al. 2008). Shortly after publication of the 2008 paper, a strong El Niño in 2009–2010 influenced the Central Gulf in a profound way. Humboldt squid in this region responded to this climatic anomaly by taking on a characteristic of the tropical portion (Costa Rica to Ecuador) of their large range, where squid mature at extremely small size (~30 cm ML, ~0.1 kg) and live for only about 6 or months (Hoving et al. 2013). In addition, commercial landings crashed. Both phenomena also occurred in conjunction with the strong El Niño of 1997–1998 (Bazzino et al. 2007; Morales-Bojórquez and Nevárez-Martínez 2010). Although recovery of landings and return to a large size at maturity occurred within a few years after the 1997–1998 event (Markaida 2006), recovery has not occurred during the years after El Niño 2009–2010, a period characterized in the Central Gulf by reduced wind-driven upwelling and productivity (Robinson et al. 2016) and, as documented in the present paper, increased warming at depth (see also Frawley et al. 2019). Another strong El Niño occurred in 2015–2016. These observations suggest that the ecological state of the Gulf of California can show drastic, long-lasting alterations that involve the size of Humboldt squid. Although small Humboldt squid are probably still abundant in the Gulf (Hoving et al. 2013 and unpublished jigging data), they are clearly much less obvious (and more difficult to capture by jigging) than larger squid were a decade ago. This new awareness is relevant to the question of why Steinbeck and Ricketts did not record this species in the Sea of Cortez in 1940. We examine several possibilities in reassessing this question. First, squid may not have been of much interest to the intertidal explorers in 1940, so not much attention was paid to this group. Second, small, juvenile specimens of Dosidicus gigas were in fact collected but misidentified. Third, large Humboldt squid were temporarily absent from the Gulf during their visit because of the effects of El Niño. Fourth, [End Page 412] large (and potentially smaller) squid were absent because of chronically unfavorable...

Trophic ecology of Humboldt squid, Dosidicus gigas, in conjunction with body size and climatic variability in the Gulf of California, Mexico

AbstractOver the past two decades, the Gulf of California (GOC) has experienced three strong El Niño events (1997–1998, 2009–2010, and 2015–2016), each of which was followed by a drastic reduction in mantle length of mature Humboldt squid, Dosidicus gigas (from >60 cm to <20 cm). However, it is unclear how the oceanographic changes associated with strong El Niño events affected the midwater organisms on which D. gigas feed, limiting our ability to assess the relative importance of temperature and food availability in the phenotypic response of D. gigas to environmental variability. We quantified the diet of D. gigas in the GOC before, during, and following the past three El Niño events and found that although its diet varied little across a large range of body sizes (8–85 cm), significant and predictable diet variability was observed with respect to sea surface temperature and chlorophyll‐a concentration. Consumption of large numbers of relatively small, high calorie prey in both relatively cool (anchovies) and relatively warm, productive conditions (myctophids) is likely necessary to support growth to large body sizes before maturation. When warm, unproductive conditions prevailed in the GOC, only small squid were present and had diets dominated by euphausiids and pteropods, prey with relatively low caloric value. Using a time series of diet data, this work provides unique insights into the response of a midwater forage community to oceanographic variability and the effects of environmental variability on the trophic ecology of an oceanic predator.

Are pelagic seabirds exposed to amnesic shellfish poisoning toxins?

Marine birds have been hypothesized to be underreported victims of harmful algal blooms (HABs). Toxic blooms of Pseudo-nitzschia spp., the primary amnesic toxin producer microalgae, domoic acid (DA) are known to cause massive mortalities of coastal seabirds and marine mammals around the world. However, these fatalities are only detected when birds die nearby the coastline and little is known about possible outbreaks of pelagic seabirds in oceanic areas. Here we aim to understand whether pelagic seabirds are exposed to amnesic shellfish poisoning (ASP) toxins. For this purpose, we tracked pelagic seabirds feeding on small epipelagic fish and squid, reported to be vectors of DA, which are obtained in high productivity zones where intense Pseudo-nitzschia blooms regularly occur. In particular, we tracked Cory’s (Calonectris borealis) and Scopoli’s (C. diomedea) shearwaters breeding in Gran Canaria (Canary Is.) and in Menorca (Balearic Is.) and feeding on the Canary Current region and the Catalonian coast, respectively. We sampled birds for blood at the recovery of the GPS (Global Positioning System) and analyzed it for DA determination by Liquid Chromatography coupled with Tandem Mass Spectrometry (LC–MS/MS). Among the 61 samples analyzed from Gran Canaria, and 87 from Menorca, 31 (50.8%) and 28 (32.2%) from each location presented detectable levels of DA ranging 1.0–10.6 ng mL−1. This work reveals that DA can be detected at variable levels in the blood of ASP-asymptomatic shearwaters and suggests a chronic exposure of shearwaters to DA, highlighting the need for further studies on DA effects. These results are of high relevance due to the vulnerability of these marine birds, which populations are in continuous decline. Since global warming is expected to alter and increase the occurrence of HABs, marine toxins might become an additional stressor for seabirds and exacerbate the already precarious conservation status of many species.

Migratory routes of different sized swordtip squid (Uroteuthis edulis) caught in the Tsushima Strait

Swordtip squid (Uroteuthis edulis) of various sizes are caught on an almost daily basis from early spring to late autumn in the eastern Tsushima Strait and southern Sea of Japan. In this study, we estimated the migratory routes of different sized squid jigged in the Tsushima Strait using statolith analyses, information on seawater temperature distributions and currents, and tracer experiments. Estimates of age and historic water temperatures suggested that both small and large squid hatch in the southern East China Sea and are then transported northeastward with the currents to the northern Kuroshio region. Following this, the small squid are transported north-northwestward to offshore waters, from where many of the squid enter the southern Sea of Japan and some move into coastal waters in the eastern strait, whereas large squid slowly move northward from the northernmost part of the Kuroshio region. Based on these distributions, it is likely that the small squid remain immature due to insufficient water temperatures over shorter durations, whereas the large squid mature in the Kuroshio region. Since migratory routes affect fishing ground formation, this information is important for both efficient fishing operations and stockmanagement of this species.

Current status of the megabenthic community in coastal Fukushima Prefecture, Japan, in the wake of the Great East Japan Earthquake

We conducted fisheries-independent bottom-trawl surveys along the coast of Fukushima, Japan, from 2013 to 2017 to study the megabenthic community structure after the 2011 earthquake, tsunami, and nuclear disaster. Although we observed no substantial changes in biodiversity, total abundance and biomass fluctuated among years, primarily because of temporary increases in the abundance or biomass of small shrimp and squid, or variations in abundance or biomass of mid-sized fishes (i.e. puffers and flatfishes) and large elasmobranchs. Echinoderm abundance and biomass decreased in all areas. Crustacean abundance and biomass were extremely low in the central and southern offshore transects. Our results suggest that there has been no recognizable recovery in the megabenthic community, and megabenthic species off the coast of Fukushima might have been experiencing reproductive or recruitment failure. Further research is needed to reveal the causal factors behind changes in these megabenthic communities.

Rapid Associative Learning and Stable Long-Term Memory in the Squid Euprymna scolopes.

Learning and memory in cephalopod molluscs have received intensive study because of cephalopods' complex behavioral repertoire and relatively accessible nervous systems. While most of this research has been conducted using octopus and cuttlefish species, there has been relatively little work on squid. Euprymna scolopes Berry, 1913, a sepiolid squid, is a promising model for further exploration of cephalopod cognition. These small squid have been studied in detail for their symbiotic relationship with bioluminescent bacteria, and their short generation time and successful captive breeding through multiple generations make them appealing models for neurobiological research. However, little is known about their behavior or cognitive ability. Using the well-established "prawn-in-the-tube" assay of learning and memory, we show that within a single 10-min trial E. scolopes learns to inhibit its predatory behavior, and after three trials it can retain this memory for at least 12 d. Rapid learning and very long-term retention were apparent under two different training schedules. To our knowledge, this study is the first demonstration of learning and memory in this species as well as the first demonstration of associative learning in any squid.

Squid predation by slender sunfish Ranzania laevis (Molidae)

In addition to crustaceans, remains from 17 individual squid were found in the stomach of a 58 cm slender sunfish Ranzania laevis from Australia, adding a new prey item to their little studied diet. Taken together with existing data from the literature, crustaceans appear to be a common prey item, with larger R. laevis (26-65 cm) also taking small fish and squid. Along with new documentation on breaching, the unexpected finding of squid in the stomach confirms that these fish are fast and agile predators.