Neon Flying Squid Ommastrephes Bartramii Research Articles

Effects of Kuroshio and Mesoscale Eddy on Fishing Ground Gravity of Neon Flying Squid Ommastrephes bartramii in Northwest Pacific Ocean

Understanding the spatial patterns of neon flying squid is important for the monitoring and management of fishery resources. Mesoscale eddies and the Kuroshio Extension play important roles in the variation of the fishing ground of Ommastrephes bartramii. However, the way in which eddies and the Kuroshio influence the distribution of Ommastrephes bartramii requires further understanding. In this study, the spatial variation in the distribution of fishing activity and the change of fishing ground gravity of squid were analyzed using automatic identification system (AIS) data. There is a positive correlation between the fishing ground gravity in latitudinal direction and Kuroshio Extension indicators based on the high-frequency eddy kinetic energy (EKE), which describes the Kuroshio variations. Furthermore, the Kuroshio Extension indicators show a positive relationship with the number of the eddies generated in the fishing ground. The results suggest that the changes in the dynamics of SST anomalies could be influenced by eddy-shedding processes in the upstream KE and then alter the distribution of the fishing ground for Ommastrephes bartramii. The Kuroshio index (mean high-frequency eddy kinetic energy between 32° and 37° N, 142° and 149° E) can be used as a good indicator of Kuroshio extension variations to investigate the squid fishing ground in the Kuroshio–Oyashio transition area.

Decadal Changes in the Annual Growth of Two Commercial Ommastrephid Species in the Pacific Ocean

Neon flying squid Ommastrephes bartramii and jumbo flying squid Dosidicus gigas are two important commercial ommastrephid species in the Pacific Ocean. As short-lived marine species, squids are highly susceptible to changes in climate and marine environments. According to samples collected from the northwest and southeast Pacific Ocean in different years, we explored the growth characteristics of these two squids in terms of their mantle length (ML) distribution and the relationship between mantle length and body weight (LWR), also considering the relative condition factors (Kn), and explored the effects of the El Niño and Southern Oscillation (ENSO) on their growth. The results showed that the ML for O. bartramii and D. gigas had significant differences among different years and different sexes (p < 0.01), and the size of females was larger than that of males. LWR showed that both squids demonstrated a positive allometric growth pattern (b > 3), and parameters a and b were influenced by year and sex. Furthermore, there were significant differences in Kn in both squids for different years and different sexes (p < 0.01), and their interannual fluctuations were quite significant. In conclusion, the alterations in the marine environment caused by climate change had a significant impact on the growth of O. bartramii and D. gigas in this study. ENSO events had opposite effects on the growth of both squid species.

Interannual and ontogenetic stage differences on trophic ecology of neon flying squid Ommastrephes bartramii inferred from stable isotope analyses in beaks

To reveal the interannual and ontogenetic stage variation of trophic ecology, different subsections of Ommastrephes bartramii beaks from different years were used for stable isotope analysis. The δ13C and δ15N values of beaks within different subsections showed significant differences between different years and different ontogenesis stages (P < 0.05). Different ecological overlap rates were found between different years and the overlap rate between 2012 and 2016 was larger than that of 2012 versus 2015 and 2015 versus 2016. The δ13C and δ15N values in 2015 were lower than those in 2012 and 2016 and represented a narrower isotope niche, whereas the ellipse area of isotope niche in 2015 was the widest and indicated that the food organisms preyed on by O. bartramii were in the lower trophic level, but the species of food organisms were more abundant in 2015. The stable isotope analyses in different growth stages showed that the niches in the larvae stage and paralarvae stage showed no significant difference between different years, indicating that the species of food organisms in the larvae stage and paralarvae stage were similar. However, with the growth of individual size, the isotopic niche gradually showed differences and developed towards a wider isotope niche in 2012 and 2016. During the El Niño event in 2015, the marine environment was not conducive to the growth of prey organisms and the poor environment might affect the feeding behavior of O. bartramii, resulting in the narrower isotope niche. During the normal years and the La Niña event, the environment was relatively suitable for O. bartramii and resulted a wider isotope niche.

Climate-induced life cycle and growth variations of neon flying squid (Ommastrephes bartramii) in the North Pacific Ocean

Climate change has had large impacts on marine animals, including neon flying squid Ommastrephes bartramii (O. bartramii) in the North Pacific Ocean. O. bartramii statoliths from 2012, 2015, and 2016 were used to evaluate the variations in life cycle events. The relationship between mantle length and body weight showed significant differences between years and gender. The oldest squid was collected in 2016 at 271 days old, further proving that O. bartramii has nearly a 1-year life span. The hatching season ranged from December to May and the peak hatching time in 2015 was one-half month later than in 2012 and 2016. Growth rates varied with environmental factors such as sea surface temperature (SST) and chlorophyll a concentration (chl. a), indicating that higher SST and chl. a concentrations led to faster growth. An extreme El Niño event with lower SST in 2015 also led to younger age class and slower growth rates. The occurrence of differences in body size and growth rates between years, caused by the interannual variations of environmental factors, makes it necessary to use separate growth curves for different years when analyzing North Pacific O. Bartramii populations.

The Change Characteristics of Potential Habitat and Fishing Season for Neon Flying Squid in the Northwest Pacific Ocean under Future Climate Change Scenarios

AbstractClimate‐driven changes in the marine environment can impact the distribution and abundance of marine species. Here, we combined available commercial fishery data of the neon flying squid Ommastrephes bartramii in the traditional fishing grounds in the northwest Pacific Ocean collected by Chinese squid jigging vessels between 1996 and 2005 with the dominant environmental climate factors affecting its distribution. Fishery and dominant environmental climate factors were incorporated into a species distribution model (maximum entropy model, MaxEnt) to describe the suitable habitats for neon flying squid. Two climate change scenarios (RCP4.5 and RCP8.5) from the Community Earth System Model Version 1 were used with MaxEnt to project the future distribution of environmental suitability for neon flying squid. Results indicated that suitable neon flying squid habitat moved northward under climate change, and the projected area of suitable habitat decreased by the end of the century. Projections revealed that suitable habitats for neon flying squid will almost disappear between July and September by 2095 in RCP4.5, and between July and November (except in October, which increased by about 34%) in RCP8.5. These findings suggest that the fishing season for neon flying squid might be delayed and the total fishing time might be shortened. We suggest that adaptive fisheries management strategies, such as controlling fishing effort and setting a closed season, should be established as soon as possible in response to climate changes in the North Pacific Ocean.

Migration patterns and changes in hatching date of neon flying squid Ommastrephes bartramii distributed in the northwestern Pacific Ocean in early summer and caught in fishing grounds off the coast of northeastern Japan in winter

Migration patterns and changes in hatching date of neon flying squid Ommastrephes bartramii distributed in the northwestern Pacific Ocean in early summer and caught in fishing grounds off the coast of northeastern Japan in winter

Habitat suitability response to sea-level height changes: Implications for Ommastrephid squid conservation and management

Sea level rise, amplified by anthropogenic climate change, causes visible impacts on wildlife habitats in low-lying coastal areas. However, the potential consequences of sea level height (SLH) changes for pelagic fish habitats in the open oceans are poorly understood, especially for climate-sensitive Ommastrephid squid. In this study, the impacts of SLH changes were estimated under three different SLH change scenarios (5 cm, 20 cm, and 35 cm) for the western stock of winter-spring neon flying squid Ommastrephes bartramii, an ecologically- and commercially-important species in the northwest Pacific Ocean (NWPO). A habitat suitability index (HSI) modeling approach was applied to predict the habitat suitability of O. bartramii, using data from 2006 to 2014 for model construction and data from 2015 for model validation. Results showed that the decreasing catch-per-unit-effort (CPUE) of O. bartramii from 2006 to 2015 was highly correlated with the increases in sea level height (SLH). Significant positive relationships were found between the HSI values for latitudinal centers of gravity (LATGHSI) and SLH. The monthly-averaged HSI of O. bartramii was negatively correlated with the SLH, except in July and November. SLH scenarios revealed that the predicted suitable habitat (areas with HSI≥0.6) exhibited a decreasing trend with increasing SLH from August to October. In July and November, the suitable habitat initially increased in the +5 cm and +20 cm scenarios, but largely declined under the +35 cm scenario. The poor habitat (areas with HSI≤0.2) significantly increased under all SLH scenarios. A poleward shift of LATGHSI was observed under all scenarios. These findings suggest that the O. bartramii habitats in the NWPO are at risk to SLH changes and have important implications for better conservation and fishery management regarding pelagic short-lived Ommastrephid squid in global oceans.

Top predator reveals the stability of prey community in the western subarctic Pacific.

The stability of the ecosystems depends on the dynamics of the prey community, but changes in the composition and abundance of prey species are poorly understood, especially in open ocean ecosystems. We used neon flying squid Ommastrephes bartramii, an active top predator, as a biological sampler to investigate the dynamics of the prey community in the southwestern part of the Western Subarctic Gyre in the northwestern Pacific Ocean. Squid were collected monthly from July to November 2016. There were no significant differences among months in stable isotopes (δ13C and δ15N) in the digestive gland, a fast turnover organ reflecting recent dietary information. Similar findings were obtained from analyses of isotopic niche width and fatty acid profiles. The potential influence of the environment (monthly mean sea surface temperature, SST, and chlorophyll-a, Chl-a) on the prey community was examined with SST and Chl-a both varying significantly among sampling months. We found little evidence for significant effects of SST and Chl-a on the isotopic values, nor on the fatty acid profiles except for 20:4n6 and 24:1n9. These lines of evidence indicate that the prey community in the southwestern part of the gyre remains stable, with little evidence for systematic changes at the community level. This study provides a novel understanding of the dynamics of the prey community and highlights the use of top predators to study the trophic dynamics of an oceanic system where a long-term scientific survey is unavailable.

Habitat suitability modelling revealing environmental-driven abundance variability and geographical distribution shift of winter–spring cohort of neon flying squid Ommastrephes bartramii in the northwest Pacific Ocean

Abstract To identify climate-related habitat changes and variations in abundance and distribution of Ommastrephes bartramii in the northwest Pacific Ocean, an habitat suitability index (HSI) model was developed in this study including sea surface temperature (SST), photosynthetically active radiation (PAR), and sea surface height anomaly (SSHA). The catch-per-unit-effort (CPUE) of O. bartramii gradually decreased between 2006 and 2015, and the latitudinal gravity centres (LATG) of the fishing effort shifted southward. Correlation analyses suggested that CPUE was positively related to SST, PAR, and the areas of suitable and optimal habitat, but negatively correlated with SSHA and the percentages of poor habitat. A significantly positive correlation was found between the LATG and the average latitude of the most preferred SST, PAR, and the average latitude of the area with an HSI between 0.9 and 1.0. From 2006 to 2015, the annual declined CPUE was highly consistent with the increase in areas of poor habitat and the reduction in areas of suitable and optimal habitats. The south-approaching LATG coincided with the southward migration pattern of the latitude of the HSI area in the range of 0.9–1.0. Moreover, compared to the El Niño events, the La Niña events, and normal climate condition yielded enlarged suitable habitat areas for O. bartramii, and the LATG moved further north.

Impacts of oceanographic factors on interannual variability of the winter-spring cohort of neon flying squid abundance in the Northwest Pacific Ocean

The neon flying squid Ommastrephes bartramii is an economically important species in the Northwest Pacific Ocean. The life cycle of O. bartramii is highly susceptible to climatic and oceanic factors. In this study, we have examined the impacts of climate variability and local biophysical environments on the interannual variability of the abundance of the western winter-spring cohort of O. bartramii over the period of 1995–2011. The results showed that the squid had experienced alternant positive and negative Pacific Decadal Oscillation (PDO) over the past 17 years during which five El Nino and eight La Nina events occurred. The catch per unit effort (CPUE) was positively correlated with the PDO index (PDOI) at a one-year time lag. An abnormally warm temperature during the La Nina years over the positive PDO phase provided favorable oceanographic conditions for the habitats of O. bartramii, whereas a lower temperature on the fishing ground during the El Nino years over the negative PDO phase generally corresponded to a low CPUE. The same correlation was also found between CPUE and Chl a concentration anomaly. A possible explanation was proposed that the CPUE was likely related to the climateinduced variability of the large-scale circulation in the Northwest Pacific Ocean: high squid abundance often occurred in a year with a significant northward meander of the Kuroshio Current. The Kuroshio Current advected the warmer and food-rich waters into the fishing ground, and multiple meso-scale eddies arising from current instability enhanced the food retention on the fishing ground, all of which were favorable for the life stage development of the western squid stocks. Our results help better understand the potential process that the climatic and oceanographic factors affect the abundance of the winter-spring cohort of O. bartramii in the Northwest Pacific Ocean.

Detection of spatial hot spots and variation for the neon flying squid Ommastrephes bartramii resources in the northwest Pacific Ocean

With the increasing effects of global climate change and fishing activities, the spatial distribution of the neon flying squid (Ommastrephes bartramii) is changing in the traditional fishing ground of 150°–160°E and 38°–45°N in the northwest Pacific Ocean. This research aims to identify the spatial hot and cold spots (i.e. spatial clusters) of O. bartramii to reveal its spatial structure using commercial fishery data from 2007 to 2010 collected by Chinese mainland squid-jigging fleets. A relatively strongly-clustered distribution for O. bartramii was observed using an exploratory spatial data analysis (ESDA) method. The results show two hot spots and one cold spot in 2007 while only one hot and one cold spots were identified each year from 2008 to 2010. The hot and cold spots in 2007 occupied 8.2% and 5.6% of the study area, respectively; these percentages for hot and cold spot areas were 5.8% and 3.1% in 2008, 10.2% and 2.9% in 2009, and 16.4% and 11.9% in 2010, respectively. Nearly half (>45%) of the squid from 2007 to 2009 reported by Chinese fleets were caught in hot spot areas while this percentage reached its peak at 68.8% in 2010, indicating that the hot spot areas are central fishing grounds. A further change analysis shows the area centered at 156°E/43.5°N was persistent as a hot spot over the whole period from 2007 to 2010. Furthermore, the hot spots were mainly identified in areas with sea surface temperature (SST) in the range of 15–20°C around warm Kuroshio Currents as well as with the chlorophyll-a (chl-a) concentration above 0.3 mg/m3. The outcome of this research improves our understanding of spatiotemporal hotspots and its variation for O. bartramii and is useful for sustainable exploitation, assessment, and management of this squid.

Sexual asynchrony in the development of beak pigmentation for the neon flying squid Ommastrephes bartramii in the North Pacific Ocean

The squid beak is a hard structure that displays high variability in both shape and coloring and can contain valuable ecological information. The beak pigmentation process reflects changes in growth and diet. In this study, we proposed species–specific beak pigmentation stages (PS) to supplement a previous classification scheme, which quantifies beak growth based on pigmentation variability. We analyzed sexual differences for Ommastrephes bartramii in the North Pacific Ocean. Distribution of beak PS increased with mantle length (ML). Body and beak measurements and beak weight were significantly different between PSs for both sexes. The relationship between ML and beak measurements differed significantly between the sexes. The observed differences might result from variable growth in different habitats as a result of sex-segregated migration in the North Pacific Ocean. The process of beak pigmentation may reflect variability in growth associated with different feeding regimes. The sexual asynchrony of pigmentation can also give us a supplemental way to discriminate different sexes using beak morphometric.

Spatio-temporal distributions and habitat hotspots of the winter–spring cohort of neon flying squid Ommastrephes bartramii in relation to oceanographic conditions in the Northwest Pacific Ocean

ABSTRACT The spatio-temporal distribution and habitat hotspots of western winter–spring cohort of neon flying squid Ommastrephes bartramii in the Northwest Pacific Ocean were examined using Chinese squid-jigging fishery data and relevant environmental data during 1998–2009. An empirical cumulative distribution function approach was employed for evaluating squid’s preference of biophysical environments. The following environmental variables were included because of their identified importance in influencing squid habitat: sea surface temperature (SST), sea surface height anomaly (SSHA), sea surface salinity (SSS), chlorophyll-a (Chl-a) concentration, mixed layer depth (MLD) and eddy kinetic energy (EKE). Integrated environmental probability maps were generated for identifying the squid habitat hotspots. The distribution and abundance of O. bartramii exhibited interannual and seasonal variability. Annual latitudinal and longitudinal gravity centers were mainly located in the waters between 41.7° and 43.4°N and between 154.2° and 160.4°E, respectively. The nominal catch-per-unit-effort (CPUE) was high in 2003–2005, 2007 and 2008, but was relatively low in 2001, 2002 and 2009. The highest CPUE occurred in August. The inferred optimal ranges for SST, SSHA, SSS, Chl-a, MLD and EKE, determined from the cumulative distribution curves, were 17.6–18.6 °C, −5–1.5 cm, 33.58–33.79 psu, 0.41–0.55 mg m −3 , 15.5–18.5 m and 28–35.5 cm 2 s −2 , respectively. Potential habitat hotspots identified for O. bartramii coincided with locations of subarctic front zone (SAFZ). Approximately 72% of the average O. bartramii CPUE observations were found in the regions with probability indices higher than 0.6. The O. bartramii CPUEs tended to increase with the increasing integrated environmental probability values over 1998–2007. The predicted areas of high CPUEs corresponded well with the fishery observation data in 2008 and 2009. This study improves our understanding of spatio-temporal variability in the habitat hotspots of O. bartramii . Similar approach may also be used to predict habitat hotspots distributions of other pelagic species.

Effects of temperature on embryonic development and paralarval behavior of the neon flying squid Ommastrephes bartramii

Studies on the relationships between the early life stages of the neon flying squid Ommastrephes bartramii and oceanographic conditions are essential for understanding the spatial and temporal distribution patterns of this ecologically and economically important species. In this study, O. bartramii eggs were artificially fertilized and incubated at temperatures found in its known distribution range (16−26°C). Complete organogenesis with normal successive cleavage and the distinct continuity of morphological features was limited to between 18 and 25°C. Experimental rearing, cruise-collected specimens, and oceanographic data confirmed that the optimal temperature range for paralarval survival around Hawaii is 18 to 25°C. Embryos reared at 16°C showed abnormal organogenesis; however, normal development resumed when the embryos were transferred to 22 or 24°C after blastoderm formation. Hatchlings showed a variety of swimming behaviors, which may allow squid to regulate their thermal distribution in the wild. Furthermore, ball formation and associated chromatophore expansion might represent an apo sematic adaptation to imitate unpalatable prey. This study highlights the flexible strategy of O. bartramii embryo development and illustrates how information on paralarval behavior and oceanographic data (sea surface temperature) may be combined to improve our understanding of the factors that influence the survival of this species.

Embryonic and paralarval development following artificial fertilization in the neon flying squid Ommastrephes bartramii

Ommastrephidae are the most important commercial fishery group among cephalopods. However, little is known about their embryonic development. This article provides details of embryonic development observed in three ommastrephids: Ommastrephes bartramii, Sthenoteuthis oualaniensis, and Eucleoteuthis luminosa. All embryos were obtained through artificial fertilization conducted onboard the research vessel Kaiyo Maru during a cruise around the Hawaiian Islands in December 2013. The embryonic and paralarval stages of O. bartramii are explained in detail. The hatchling stages were compared between all three species, as well as with information on Illex argentinus hatchlings from the literature. The species-specific effects of the oviducal gland powder on chorion expansion were analyzed. The results indicated that the overall chemical nature of the oviducal gland was species specific, although the inducer of chorion expansion was the same across species. In addition, treatment with oviducal gland jelly induced partial parthenogenesis in the early stages of embryonic development through the expansion of the perivitelline space and blastodisc formation.

北太平洋柔鱼微卫星标记的筛选及遗传多样性分析

PDF HTML阅读 XML下载 导出引用 引用提醒 北太平洋柔鱼微卫星标记的筛选及遗传多样性 DOI: 10.5846/stxb201303030334 作者: 作者单位: 上海海洋大学海洋科学学院,上海海洋大学海洋科学学院,上海海洋大学海洋科学学院,上海海洋大学海洋科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(41276156);国家863计划(2012AA092303);国家发改委产业化专项(2159999);上海市科技创新行动计划(12231203900) Isolation and genetic diversity of microsatellite DNA of Ommastrephes bartramii in the North Pcific Ocean Author: Affiliation: SHOU,shou,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:采用(AC)12、(AG)12两种生物素探针,通过磁珠富集法构建了柔鱼部分基因组微卫星富集文库。68个阳性克隆中有60个含有微卫星序列,重复次数在10次以上的占86.84%,最高重复次数为33次。其中,完美型微卫星占60.53%,非完美型微卫星占36.84%,混合型微卫星占2.63%。除探针使用的AC/TG、AG/TC重复外,还得到ACAG、AGAC重复序列。利用筛选出的8个微卫星位点对北太平洋柔鱼6个群体的遗传多样性及遗传结构进行分析。结果表明,8个微卫星位点均为高度多态性位点(PIC=0.787-0.987),位点Bo103与位点Bo105极显著偏离Hardy-Weinberg平衡(P < 0.01)。6个地理位置的柔鱼群体显示出较高的遗传多样性水平(Ho=0.672-0.761,He=0.808-0.851)。两两群体间的Fst值以及AMOVA分析结果均表明,群体间遗传分化不显著(Fst=0.00559,P > 0.05),遗传差异主要来自于个体间。基于Nei's遗传距离的UPGMA聚类树显示,北太平洋东北部2个柔鱼群体(NE1、NE3)聚为一类,西北部3个群体(NW1、NW2、NW3)与东北部1个群体(NE2)另聚为一类,且群体NW1与群体NE2亲缘关系最近,遗传距离与地理距离线性相关分析没有呈现出正相关性(R=0.175,P > 0.05)。遗传结构分析结果推断北太平洋柔鱼存在1个理论群。柔鱼个体具有较强的游泳能力,在海流的作用下,群体之间存在较强的基因交流。建议今后在柔鱼资源开发利用过程中将北太平洋柔鱼看作1个管理单元。 Abstract:The neon flying squid Ommastrephes bartramii is found circumglobally in subtropical and temperate waters in the world and supports important fisheries in the North Pacific Ocean. The population of the North Pacific O. bartramii comprises a fall spawning cohort and a winter-spring spawning cohort. Most of the fall cohort occurs east of 170°E, whereas the winter-spring cohort is widely distributed across the North Pacific Ocean. Two spawning cohorts can be further subdivided into four stocks: a central and an eastern stock of the fall cohort separated near 160°W, and a western and a central-eastern stock of the winter-spring cohort separated near 170°E in which the fall cohort was the target of a driftnet fishery before 1993 while the west stock of winter-spring cohort became main fishing target of an international jigging fishery. Being a short-lived ecological opportunist, neon flying squid exhibits large fluctuations in stock abundance and distribution on the feeding grounds and large fluctuating recruitment on the spawning grounds in response to environmental variability. In order to improve our understanding of population structure, the genetic diversity of O. bartramii populations in the North Pacific Ocean was examined using microsatellite markers. Two types of biotin-labeled oligos were employed and part of microsatellite-enhanced genomic library of O. bartramii was constructed by the method of streptavidin magnetic beads. Sixty of 68 positive clones comprised microsatellite sequences and repeat number of more than 10 accounted for 86.84% with the largest one of 33. Of these were 60.53% perfect, 36.84% were imperfect, and the rest were compound type (2.63%). Repeats including (ACAG)n and (AGAC)n were also detected except that of AC/TG and AG/TC. Microsatellite markers were isolated and screened, and 8 of them were then used for the analysis of genetic diversity and genetic structure of six populations of O. bartramii in the North Pcific Ocean. Results showed that all the 8 loci were highly polymorphic (PIC=0.787-0.987), and locus Bo103 and locus Bo105 were extremely significant deviated from Hardy-Weinberg equilibrium (P < 0.01). All of the 6 different geographic populations showed high genetic diversities (Ho=0.672-0.761, He=0.808-0.851). Pairwise F test and AMOVA analysis detected no significant genetic differentiations among populations, and genetic differences mainly came from individuals. UPGMA clustering tree based on Nei's genetic distance demonstrated that two stocks (NE1 and NE3) in the northeast of the North Pcific Ocean clustered together, while the three stocks (NW1, NW2 and NW3) in the western part as well as one stock (NE2) in the eastern part clustered together, and the genetic distance between NW1 and NE2 was closer. Relations between genetic distance and geographic distance did not show positive correlation (R=0.175, P > 0.05), indicating that different populations of O. Bartramii could mingle together. Genetic structure simulation analyses suggested that there was only one logic population of all individuals, and extensive gene exchange might occur among the populations, which could be attributed to the influence of ocean currents and swimming ability of O. bartramii individuals. The North Pacific O. bartramii should be considered as a single stock in their assessment and management. 参考文献 相似文献 引证文献

Pelagic cephalopods in the western Indian Ocean: New information from diets of top predators

Using a combination of diverse large predatory fishes and one seabird, we collected information on the cephalopod fauna of the western Indian Ocean. We analyzed the stomach contents of 35 fishes representing ten families (Xiphiidae, Istiophoridae, Scombridae, Carangidae, Coryphaenidae, Alepisauridae, Dasyatidae, Carcharhinidae, Alopiidae and Sphyrnidae) and of the sooty tern Onychoprion fuscata of the Mozambique Channel from 2000 to 2010. Both fresh and accumulated beaks were used for identifying cephalopod prey. Cephalopods were important prey for twelve predators; swordfish Xiphias gladius had the highest cephalopod proportion; sooty tern (O. fuscata) and bigeye tuna (Thunnus obesus) had high proportions too. We recovered 23 cephalopod families and identified 38 species. Ten species from four Teuthida families (Ommastrephidae, Onychoteuthidae, Histioteuthidae and Ancistrocheiridae) and two Octopoda families (Argonautidae and Bolitaenidae) occurred very frequently in the stomach contents, while Sepiida were rare. Ommastrephidae were the most cephalopod food sources: the purpleback flying squid Sthenoteuthis oualaniensis was the most prevalent prey by far, Ornithoteuthis volatilis was important for eleven predators and few but large specimens of the neon flying squid Ommastrephes bartramii were recovered in the stomachs of swordfish in the Indian South Subtropical Gyre province only. Predators' groups were identified based on cephalopod prey composition, on depth in which they forage, and on prey size. Surface predators' diets were characterized by lower cephalopod diversity but greater average numbers of cephalopod prey, whereas the deep-dwelling predators (swordfish and bigeye tuna) preyed on larger specimens than surface predators (O. fuscata or yellowfin tunas Thunnus albacares). Our findings emphasized the usefulness of a community of marine predators to gain valuable information on the biology and the distribution of the cephalopod forage fauna that are discussed with regard to biogeographic province, marine predator, fishing gear to catch the large pelagic fishes, and size of the beaks recovered in the stomachs.

Tentacle-breakage mechanism for the neon flying squid Ommastrephes bartramii during the jigging capture process

In squid jigging operations for neon flying squid (Ommastrephes bartramii), 30–40% of hooked squid are estimated to fall off (i.e., become detached) from the jigs during the drum-hauling process, caused by breakage/severance of the hooked tentacle(s). Reducing fall-off events can lead to higher productivity and more efficient use of the squid resource. In the present study, there were 950 fall-off events either directly observed or assessed from the residue of tentacle(s) left on the jigs compared with the 1720 total captures, which comprises 35.6% of 2670 total hooked squids. The fall-off ratio according to the mantle length (ML) was examined using logistic curve analysis and a higher fall-off ratio for smaller squid was confirmed through size selectivity curve analysis. F50, the 50% probability of fall off from the jig, was estimated to be 37.4cm ML. The breaking strength of a single tentacle was determined to be similar to the body weight (BW) of squid smaller than 41.4cm ML, indicating a high possibility of tentacle breakage in the case of 1 tentacle grabbing the jig for smaller-sized squid.

Population genetic structure of the neon flying squid Ommastrephes bartramii inferred from mitochondrial DNA sequence analysis

アカイカは北太平洋の沖合域で最も重要な漁業対象種の一つであり，適切な資源評価を行う上で，その基礎的な集団構造に関する情報を得ることは重要である。そこで，mtDNA の ND1 から 16SrRNA 遺伝子領域の塩基配列分析を行い，海域間の比較を行った。対照としてインド洋のアカイカを用いた。インド洋と北太平洋のアカイカ集団には有意な遺伝的な変異が認められた。一方，北太平洋の採集位置間には有意な遺伝的差異はなかった。今後，より変異性の高い領域を使って集団構造解析をする必要がある。

Genetic differentiation of the neon flying squid Ommastrephes bartramii between North Pacific and South Atlantic populations

全世界の亜熱帯から温帯域に広く分布するアカイカの，南北大洋間の遺伝的差異を明らかにすることを目的に，北太平洋と南大西洋で採集された各 50 個体を用い，mtDNA 16S rRNA 領域（506 bp）の塩基配列分析を行った。その結果，13 種類のハプロタイプが検出され，北太平洋標本群と南大西洋標本群では共通するハプロタイプをもたず，3 つのサイトにおいて異なる塩基の固定がみられた。Exact test の結果は p<0.001 で有意差が認められ，両集団間に遺伝的分化が見られることが確認された。