Pacific Coast Of Hokkaido Research Articles

Snailfishes of the genus Careproctus (Perciformes: Liparidae) with a reduced pelvic disk: three new species and new records from the western North Pacific with comments on their phenotypic diversity

A taxonomic review of the snailfish genus Careproctus (Liparidae) with a reduced pelvic disk—the Careproctus gilberti species group—from the western North Pacific recognized three new species from the southern Sea of Okhotsk, and confirmed the validity of Careproctus gilberti, Careproctus mederi, Careproctus ostentum, and Careproctus parvidiscus. One of the newly described species, Careproctus longibarbatus sp. nov., had been previously confused with C. mederi, but was readily distinguishable on the basis of counts of vertebrae (61–66 vs. 57–63), dorsal- (56–60 vs. 52–56) and anal-fin rays (50–54 vs. 47–52), as well as length of the pectoral fin lower lobe (extending past anus vs. not reaching anus) and color of the peritoneum (dark vs. pale with black dots). Careproctus barbatulus sp. nov. and Careproctus spinulosus sp. nov. were diagnosed by pectoral fin lower lobe length, anus position, and vertebral, and dorsal- and anal-fin ray counts. The validities of the three new species were also confirmed by mitochondrial sequence data. Careproctus mederi was redescribed based on specimens from the southern Sea of Okhotsk, representing the first Japanese, as well as southernmost record of the species. Furthermore, the full description of an unidentified Careproctus species, most similar to C. gilberti, from the Pacific coast of Hokkaido was provided. Significant morphological variation within the C. gilberti species group, possibly resulting from reproductive interference among sympatric species, was also discussed.

Radiocarbon ages and tsunami deposits in laminated mud layers from the Lake Harutori, Pacific coast of Hokkaido, Northeast Japan

To identify temporal changes in the marine reservoir effect in Northeast Japan, the radiocarbon ages of terrestrial plants and marine shells were measured from two cores obtained from Lake Harutori in Kushiro City. This lake located where one of the highest marine reservoir effect was detected in East Asia, facing the Oyashio cold current. This drilling site is situated in a tectonically active region of the southwestern Kuril arc. Based on lithological analyses, molluscan assemblages, and radiocarbon dating, we interpreted five units in order of decreasing age: basement coastal sediments, estuary sediment, laminated sediment, inner bay sediment, and artificial fills. These sediments consisted of laminated mud beds with terrestrial plant fragments and intercalating tsunami sand beds. The structure was imaged using core scanning computed tomography and X-ray fluorescence. The reservoir ages of seven pairs were obtained from estuary sediment to inner-bay sediment over the past 9000 years.

Paleotsunami history of Hachinohe, northern Japan: a multiproxy analysis and numerical modeling approach

Paleotsunami studies along the Pacific coast of Tohoku, northern Japan, have been considerably developed recently, particularly after the massive impact of the 2011 Tohoku-oki tsunami. Nevertheless, in the southernmost Shimokita Peninsula, studies pertaining to paleotsunami are underdeveloped, leading to a vague understanding of the tsunamigenic sources northward of the Tohoku region, along with incomplete hazard evaluation. Paleotsunami deposits in Shimokita can be related not only to the Japan Trench along the Sanriku coast but also to the Kuril trench along the Pacific coast of Hokkaido. In this study, we unveiled the paleotsunami history of Hachinohe in northern Tohoku. Using a combination of sedimentological, geochemical, paleontological, and mineralogical proxies, we characterized seven sand layers that dated from ca. 2700 to ca. 5500 yr BP based on radiocarbon (14C) ages as event deposits of marine origin. Sedimentological and paleontological evidence coupled with ground-penetrating radar imagery revealed a marsh environment comprising successive extinct ponds, controlling the depositional environment. Numerical modeling ruled out the possibility of storms as genetic sources, leading to the conclusion that the presence of event deposits with marine sediments in the study area would be associated with tsunami inundation episodes. Based on 14C dating, the mean frequency of recurrence of tsunamis is estimated as 384 years (320–450 yr, 95% confidence interval) and a coefficient of variation of 0.78 (0.68–0.99, 95% confidence interval). The previously recorded limited paleotsunami evidence and absence of an estimated recurrence interval in the Shimokita Peninsula reaffirm the importance of Hachinohe as a tsunami record site for the activity of both trenches.

Positive effect of filtration additives for increasing environmental DNA detections in summer and winter oceanic waters

AbstractEnvironmental DNA (eDNA) is a convenient biodiversity monitoring tool, and many studies have focused on river and coastal areas, while deep‐water oceanic surveys are rare. However, using eDNA techniques to learn about oceanic communities may also be a useful approach. We tested methods to enhance ocean eDNA collections adding four different materials (sediment, diatomite, zirconia bead, and molecular sieve) in combination with 0.45‐μm pore size filter, also compared 0.22‐μm pore size filter, using five 2‐L volume replicates. The experiments were conducted off the Pacific coast of Hokkaido, Japan, in summer and winter. The winter trial also included a larger water volume (10 L, duplicate) experimental treatment. The added diatomite showed the highest number of detected operational taxonomic units (OTU) in the summer trial, while sediment and beads showed higher numbers in winter. GLM analysis showed that pore size does not affect the number of OTUs, while season and the other four additive materials were significant effects. The added materials in the water likely trapped more eDNA and prevented it from passing through the filters. The 10‐L filtered sample had more OTUs than combining five replicates of 2‐L filtered samples. Comparison among the same trial revealed that DNA composition in the water is variable, and detected species differed even in the same water sample. Species richness and diversity were higher in winter than in summer, and species compositions differed between seasons. The greater numbers of species detected using filtration additives suggest these methods could be useful for eDNA ocean biodiversity surveys.

Horizontal distribution of harmful red-tide Karenia selliformis and phytoplankton community along the Pacific coast of Hokkaido in autumn 2021

Horizontal distribution of harmful red-tide <i>Karenia selliformis</i> and phytoplankton community along the Pacific coast of Hokkaido in autumn 2021

Osteodiscus abyssicola, a new snailfish (Cottoidei: Liparidae) collected off the Pacific coast of northern Japan.

The snailfish Osteodiscus abyssicola sp. nov. is described from a single specimen collected off the Pacific coast of Hokkaido, northern Japan, at a depth of 4,6714,744 m. It is distinguished from all currently recognized congeners by the following combination of characters: vertebrae 49; dorsal-fin rays 44; anal-fin rays 39; principal caudal-fin rays 8; pyloric caeca 5; mouth horizontal; teeth on both jaws simple and sharp, without cusps; upper and lower jaw symphyses without diastema; cephalic pore sizes moderate, similar to or slightly larger than nostril; gill slit extending ventrally to 2nd pectoral-fin ray base; pectoral fin notched; mandibular symphysis to center of anus 101.6% head length (HL); posterior edge of pelvic disk to center of anus 15.5% HL; epural 1, reduced; epipleural ribs absent. An emended diagnosis and key to the species of Osteodiscus are provided.

Holocene tsunami, storm, and relative sea level records obtained from the southern Hidaka coast, Hokkaido, Japan

On the Pacific coast of Hokkaido, historical documents and seismic detections spanning the last 200 years show that large earthquakes (magnitude 7–8) have occurred every 50–100 years along the Kuril Trench. Geological reconstructions of past earthquakes in the region show extend records to the last 6000 years and show that unusually large (>M8) earthquakes occurred at intervals of several hundreds of years. However, the magnitude and extent of tsunamis induced by these unusually large earthquakes are not fully understood. In this study, we found nine anomalous sand layers embedded in peat sediments that dated between 5.5 and 1.2 ka on the southern Hidaka coast, Hokkaido. Paleoenvironments reconstructed from the peat sediments using diatom, chemical, and mineralogical analyses showed an evolution of the site from a saltmarsh, to a supratidal marsh, to a back-barrier wetland environment. Radiocarbon dating of peat sediments showed that these environmental changes correspond to a sea-level fall following the mid-Holocene highstand. The anomalous sand layers showed inland thinning and shape contacts with the underlying peat. Amongst the layers, the most recent layer (1.7–1.2 ka) was designated as a storm deposit due to its limited distribution of less than 100 m from the beach ridge. Eight additional sand layers from 5.5 to 2.2 ka were distributed more than 300 m away from the beach ridge, and displayed a normal grading of sand particles, a characteristic typical of tsunami deposits. Because there was no record of tsunamis striking the Hidaka coast from the observed large earthquakes (M7–8) that recur every 50–100 years, we interpret the sand layers as tsunamis deposited by unusually large earthquakes. Because the eight inferred tsunami sand layers were deposited during the highstand period, prior to 2.2 ka, we infer that the inundation area due to tsunamis in the coastal zone has changed with relative sea-level (RSL) in the past. We highlight the necessity of evaluating the influence of long-term RSL change.

Detecting no natural hybridization and predicting range overlap in Saccharina angustata and Saccharina japonica

Natural hybridization can play a significant role in evolutionary processes and influence the adaptive diversification and speciation of brown seaweeds. However, this phenomenon is as yet unknown in Saccharina kelps. Saccharina angustata and two varieties of Saccharina japonica (S. japonica var. japonica and S. japonica var. diabolica) partly overlap in distribution along the Pacific coast of Hokkaido, which makes them a good model system to study hybridization and introgression among species of the genus Saccharina. Based on 13 highly variable nuclear microsatellites and a mitochondrial marker, we assessed the genetic diversity levels of S. angustata for the first time and populations from Muroran to Shiranuka (western part of the Pacific coast in Hokkaido) exhibited highest genetic diversity. Genetic diversity of S. japonica was higher in S. japonica var. japonica as compared with S. japonica var. diabolica. There was significant genetic differentiation (FST > 0.25, p < 0.05) between S. japonica and S. angustata based on both markers. Moreover, there was poor genetic connectivity and limited interspecific hybridization among these closely related Saccharina species. Ecological niche models projected a northward expansion of both S. japonica and S. angustata under future climate scenarios and a range overlap between two species along the coast of Okhotsk Sea in Kamchatka Peninsula. The interspecific hybridization and genetic diversity among these kelps provide insights for kelp selection and cultivation as well as future conservation strategies of wild stocks.

Limpet disturbance effects on barnacle recruitment are related to recruitment intensity but not recruit size.

Intertidal limpets are important grazers along rocky coastlines worldwide that not only control algae but also influence invertebrates such as common barnacles. For instance, grazing limpets ingest settling barnacle cyprid larvae (hereafter cyprids) and push cyprids and barnacle recruits off the substrate. Such limpet disturbance effects (LDEs) can limit barnacle recruitment, a key demographic variable affecting barnacle population establishment and persistence. In this study, we examined limpet (Lottia cassis) disturbance to barnacle (Chthamalus dalli, Balanus glandula) recruitment on the Pacific coast of Hokkaido, Japan, as information on limpet-barnacle interactions from this region is missing. We investigated, for the first time, whether barnacle size and recruitment intensity influence LDEs on barnacle recruitment. Small barnacles may be less susceptible to LDEs than larger barnacles, because small size may reduce the propbability of limpet disturbance. Moreover, recruitment intensity can influence LDEs, as high recruitment can compensate for LDEs on barnacle recruitment density. In Hokkaido, C. dalli cyprids are smaller than B. glandula cyprids, and C. dalli recruitment is higher than B. glandula recruitment. Thus, we hypothesized that LDEs on C. dalli recruitment would be weaker than those on B. glandula recruitment. To test our hypothesis, we conducted a field experiment during which we manipulated limpet presence/absence on the interior surfaces of ring-shaped cages. After four weeks, we measured barnacle recruitment and recruit size on the interior surfaces of the cages and found negative LDEs on C. dalli and B. glandula recruitment and recruit size. As hypothesized, the LDEs on C. dalli recruitment were weaker than the LDEs on B. glandula recruitment. Additionally, C. dalli recruits were smaller than B. glandula recruits. However, the LDEs on C. dalli recruit size were as strong as the LDEs on B. glandula recruit size, indicating that the smaller C. dalli recruits are not less susceptible to LDEs than B. glandula recruits. Since C. dalli recruitment was higher than B. glandula recruitment, we propose that the higher C. dalli recruitment compensated for the LDEs on C. dalli recruitment. Our findings indicate that the detected differences in LDEs on barnacle recruitment are related to barnacle recruitment intensity but not recruit size.

Consumption of juvenile chum salmon by a seabird species during early sea life

Juvenile mortality, a key factor determining the stock sizes of salmonids, may be increased by predation both in rivers and along shores. Information on predation at sea, however, is scarce. We analysed the diet of a pelagic seabird, the rhinoceros auklet Cerorhinca monocerata, breeding on an isolated island off eastern Hokkaido, Japan, and estimated their consumption of juvenile chum salmon Oncorhynchus keta. The auklets brought juvenile chum salmon and Japanese anchovy Engraulis japonicus for their chicks and, in addition, fed on squid themselves. The fork length of most of the juvenile chum salmon was over 80 mm, indicating that they were migrating to offshore nursery area, the Sea of Okhotsk. Using a simple bioenergetics model, the consumption of juvenile chum salmon by auklets during the first half of chick-rearing period (late June to middle July) was 316.6 t in 2014 (296.4 t by adults, 20.2 t by chicks) and 11.7 t in 2015 (0 t by adults, 11.7 t by chicks). The otoliths of six out of 66 juvenile salmon found in the diet for chicks had thermal markings and indicated that these fish were released from the rivers along Pacific coast of Hokkaido. Our study first demonstrates the extent of the auklets' consumption contributing to the reduction of the survival in the open coastal area of juvenile chum salmon with the known stock origins.

Mechanisms underlying predator-driven biotic resistance against introduced barnacles on the Pacific coast of Hokkaido, Japan

Introduced species are a major threat to coastal ecosystems worldwide. Thus, understanding biotic resistance (i.e. the ability of native species to limit introduced species) is a central goal of invasion biology. This paper examines mechanisms underlying biotic resistance. Consumption can limit introduced prey provided that native predators prefer such prey. Furthermore, predator nonconsumptive effects (NCEs), mediated through predator-released cues perceived by prey, can limit prey recruitment, a key demographic process for prey populations. However, information on predator NCEs is largely absent in the context of recruitment in introduced prey. Working on the Pacific coast of Hokkaido (Japan), we addressed this knowledge gap using native predatory dogwhelks (Nucella lima) that prey on native barnacles (Chthamalus dalli) and introduced barnacles (Balanus glandula). We experimentally examined dogwhelk preferences for barnacles in the laboratory and dogwhelk NCEs on barnacle recruitment in the field. We found that N. lima preferred B. glandula over C. dalli, likely as B. glandula prey is more profitable, as suggested by previous findings in congeneric dogwhelks. Moreover, we found that N. lima NCEs limited recruit density in C. dalli and B. glandula, likely as barnacle larvae moved away from dogwhelk cues to reduce future predation risk. Our study suggests that predator prey preferences and predator nonconsumptive limitation of prey recruitment are two mechanisms that can contribute to predator-driven biotic resistance against introduced prey.

Real-Time Tsunami Inundation Forecast for a Recurrence of 17thCentury Great Hokkaido Earthquake in Japan

Paleotsunami studies have shown that several large tsunamis hit the Pacific coast. Many tsunami deposit data were available for the 17thcentury tsunami. The most recent tsunami deposit study in 2013 indicated that the large slip of about 25 m along the plate interface near the Kurile trench would be necessary and the seismic moment of this 17thcentury earthquake was 1.7 × 1022Nm. If a great earthquake like the 17thcentury earthquake occurs off the Pacific coast of Hokkaido, the devastating disaster along the coast is expected. To minimize the tsunami disaster, a development of the real-time forecast of a tsunami inundation area is necessary. Estimating a tsunami inundation area requires tsunami numerical simulation with a very fine grid system of less than 1 arcsecond. There is not enough time to compute the tsunami inundation area after a large earthquake occurs. In this study, we develop a real-time tsunami inundation forecast method using a database including many tsunami inundation areas previously computed using various fault models. After great earthquakes, tsunamis are computed using linear long-wave equations for fault models estimated in real time. Simulating such tsunamis takes only 1-3 minutes on a typical PC, so it is potentially useful for forecasting tsunamis. Tsunami inundation areas computed numerically using various fault models and tsunami waveforms at several locations near the inundation area are stored in a database. Those computed tsunami waveforms are used to choose the most appropriate tsunami inundation area by comparing them to the tsunami waveforms computed in real time. This method is tested at Kushiro, a city in Hokkaido. We found that the method worked well enough to forecast the Kushiro’s tsunami inundation area.

Interannual changes in the timing of walleye pollock spawning migration and their impacts on the gillnet fishery in the southwestern Pacific coast of Hokkaido, Donan area, Japan

The southwestern Pacific coast of Hokkaido is the main spawning ground for the Japanese Pacific stock of walleye pollock Theragra chalcogramma. A commercial gillnet fishery targeting spawning adult pollock in this area mainly operates from October to January to coincide with the migration of adult pollock from the feeding ground. Given the results of acoustic surveys, and changes in the proportion of the monthly total catch that was monthly walleye pollock caught by the commercial gillnet fishery, it is thought that the timing of walleye pollock spawning migration to the Donan area varies among years and that the pollock catch of the gillnet fishery clearly reflects changes in pollock abundance in this area. A time series of interannual variability in catch data from 1980 to 2005 suggested that adult pollock migrated and concentrated on their spawning ground later in the 1980s and after 2000 than in the 1990s. Such decadal-scale shifts are presumably caused by climatic changes (e.g., in water temperature) in the Oyashio region. These shifts affect the gillnet fishery through differences in monthly unit prices of pollock and changes in the formation of fishing grounds. These scientific findings can aid the establishment of rules for more efficient walleye pollock resource management under the total allowable catch system.

Decade‐scale decrease inb value prior to the M9‐class 2011 Tohoku and 2004 Sumatra quakes

The Gutenberg‐Richter frequency‐magnitude distribution of earthquakes has become well established in seismology. The slope of the relation between frequency and magnitude (b value) is typically 1, but it often shows variations around 1. Based on an analysis of seismicity prior to the 2011 Tohoku and 2004 Sumatra earthquakes (both in magnitude (M) 9 class), we show that the pronounced decade‐scale decrease inbvalue was a common precursor to both mega‐quakes around their hypocenters. This is the first report onM9‐class quakes to confirm a change inb value, which has been predicted based on the results of laboratory experiments. We propose that the b value is an important indicator of an impending great earthquake, and has great potential in terms of predicting a future large quake off the Pacific coast of Hokkaido, Japan.

Site-Specific Behavior of 2011 Tohoku Earthquake Tsunami Influenced by Artificial Changes of Coastal Environments

Many aspects affect local tsunami behavior. A drastic change in behavior in the 2011 Tohoku Earthquake at specific sites in relation to coastal conditions in Hokkaido. These include coastal constructions such as jetty ports, digging formula ports, types of seawall, etc., in addition to land use for fisheries. Examples of site-specific behavior in the 2011 Tohoku Earthquake along the Pacific coast of Hokkaido are introduced in order to help future tsunami disasters.

Evolution of the 2011 Tohoku Earthquake Tsunami on the Pacific Coast of Hokkaido

A numerical computation of the 2011 Tohoku earthquake tsunami was performed to identify fundamental features of the tsunami evolution along the coast of Hokkaido, Japan. Edge waves formed at multiple locations where the refracted tsunami focused, governing local surface oscillations and regional variations in tsunami height along the Pacific coast of Hokkaido. The computation reasonably reproduced the distribution of surveyed tsunami height as well as the time records of surface elevation recorded at ports in Hokkaido. The major features of the frequency spectrum for the 2011 Tohoku tsunami were identical to those for the 2003 Tokachi-oki earthquake tsunami; inherent local properties of surface oscillation caused by the passage of edge waves existed, determined by the local bathymetry.

Seismic quiescence before the 2003 Tokachi‐oki earthquake

Some studies have found evidence of seismic quiescence, periods with fewer small earthquakes than normal, before the occurrence of some large earthquakes. In a new case study, Katsumata reexamined data from an earthquake catalog to study seismic activity preceding the magnitude 8 Tokachi‐oki earthquake that occurred on 26 September 2003 off the Pacific coast of Hokkaido. The author's statistical analysis showed that there was a clear, significant decrease in seismic activity in the region during the 4 years leading up to the Tokachi‐oki earthquake. This period of quiescence was similar in length to several other quiescence periods reported before other earthquakes. Further studies and improved seismic monitoring will be needed to determine how common precursory seismic quiescence is. (Journal of Geophysical Research‐Solid Earth, doi:10.1029/2010JB007964, 2011)

First Record of Ernogrammus zhirmunskii (Actinopterygii: Cottiformes: Stichaeidae) from Japan, with a Description and a Revised Diagnosis

Sixteen specimens of Ernogrammus zhirmunskii Markevich and Kharin, 2011, formerly known only from Peter the Great Bay, Russia, were collected from Volcano Bay on the Pacific coast of Hokkaido and from Shizugawa Bay, Miyagi Prefecture, Pacific coast of the northern Honshu, Japan. This species is redescribed on the basis of these specimens and several errors in the original description are corrected. This species is easily distinguished from other stichaeid fishes in having a diagnostic lateral-line pattern and a rigid spine in the posteriormost part of the anal fin.

北海道太平洋側の大陸斜面域漁場における海底表面の起伏と底生魚類の分布

漁業が海洋生態系に及ぼす影響を明らかにするため，北海道太平洋側大陸斜面域の底魚漁場において，深海ビデオカメラを用いて海底表面の起伏を観察し，起伏の程度と底生魚類の分布の関係を調べた。イラコアナゴ，ソコダラ類，キチジ，スケトウダラ，ゲンゲ類，コブシカジカ，カレイ類などの魚類が観察された。キチジは地形・地質的な起伏が大きい場所を選好し，底層水温が高く地形・地質的な起伏の大きな調査点で分布密度が高かった。キチジの生息環境を良好に維持するためには，起伏に富む海底を保全することが必要であると思われた。

Precursory seismic quiescence before theMw= 8.3 Tokachi-oki, Japan, earthquake on 26 September 2003 revealed by a re-examined earthquake catalog

[1] The 2003 Tokachi-oki earthquake (Mw = 8.3) occurred on 26 September 2003 off the pacific coast of Hokkaido, Japan. In the present study, an earthquake catalog is used that lists 2,000 earthquakes with M ≥ 3.3. All of the earthquake waveforms were recorded by the Institute of Seismology and Volcanology, Hokkaido University. In the present study, these waveforms are manually re-examined, and hypocenters and magnitudes are re-calculated. A detailed analysis of the re-determined earthquake catalog between 1994 and 2003 using a gridding technique (ZMAP) shows that the 2003 Tokachi-oki earthquake is preceded by two neighboring seismic quiescence anomalies that start around the beginning of 1999, and last about 5 years, until the main shock occurs. These quiescence anomalies are located around the asperity ruptured by the main shock, and the Z-values are +3.9 and +4.0 for a time window of Tw = 4 years, using a sample size of N = 100 earthquakes. The detected seismic quiescences can be interpreted as being caused by a decrease of 50% in the stressing rate based on Dieterich's theory. It is proposed that a quasi-static pre-slip occurs at the northeastern edge of the asperity ruptured by the main shock, and lasts for five years until the main shock occurs. By calculating the change in the Coulomb failure stress (ΔCFS), it is found that negative ΔCFS areas are consistent with the two quiescence anomalies, and a positive ΔCFS area corresponds to the hypocenter of the main shock, indicating that the quasi-static pre-slip model is a plausible one.