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1. The pulse-like clicking sounds made by odontocetes for echolocation (biosonar) can be roughly classified by their frequency characteristics into narrow-band high-frequency (NBHF) clicks with a sharp peak at around 130 kHz and wide-band (WB) clicks with a moderate peak at 30–100 kHz. Structural differences in the sound-producing organs between NBHF species and WB species have not been comprehensively discussed, nor has the formation of NBHF and WB clicks. 2. A review of the sound-producing organs, including the latest findings, could lead to a new hypothesis about the sound production mechanisms. In the current review, data on echolocation click characteristics and on the anatomical structure of the sound-producing organs were compared in 33 species (14 NBHF species and 19 WB species). 3. We review interspecific information on the characteristics of click frequencies and data from computed tomography scans and morphology of the sound-producing organs, accumulated in conventional studies. The morphology of several characteristic structures, such as the melon, the dense connective tissue over the melon (the ‘porpoise capsule’), and the vestibular sacs, was compared interspecifically. 4. Interspecific comparisons suggest that the presence or absence of the porpoise capsule is unlikely to affect echolocation frequency. Folded structures in the vestibular sacs, features that have been overlooked until now, are present in most species with NBHF sound production and not in WB species; the vestibular sacs are therefore likely to be important in determining echolocation click frequency characteristics. The acoustical properties of the shape of the melon and vestibular sacs are important topics for future investigations about the relationship between anatomical structure and sound-producing mechanisms for echolocation clicks.

Aims: Morphology and molecular biology of a rare shark-rays Rhina ancylostoma caught from Java sea.Indonesia. Study Design: Morphology, morphometry and DNA analysis of the fish specimen. Place and Duration of Study: Sample wascollected from fish auction hall at north Java, specimen now stored in Lab of Ichtiology. Department of Fisheries. Faculty of Fisheries and Marine Science. Diponegoro University, between March to December 2019. Methodology: DNA extraction, amplification and molecular identification of fish sample.Yield of DNA supernatant transferred in an eppendeorf tube and stored in 4°C for further process. PCR amplification. Part of Mithocondrial DNA COI (Cytochrome Oxidase subunit-I) gen was amplified using Polymerase Chain Reaction (PCR) method. Then matched up with GenBank database at NCBI using Basic Local Alignment Search Tool (BLAST) analysis. Philogenetic tree was set using Neighbor-Joining method, Kimura-2 parameter model and 1,000 bootstrap replication. Some sequence from NCBI GenBank were inputted into philogenetic tree as comparison. Results: Rhina ancylostoma as one of demersal shark rays catch from tropical shallow Java sea. Range of Total Length 73 – 200 cm and dominant Total Length catch 125 cm. Morphologyis characterised with three lines of spine thorn on the head, morphometry characteriswide of head to TL ratio 0.77. DNA analysis had confirmed the specimen of AH2 as Rhina ancylostoma based on homological match up of sequence of Gen Bank database with reference accesion number KU721837.1 with length sequence of 665 bpand identical similarity of 99.84% for specimen Accession number LC 505461. Conclusion: Rhina ancylostoma as one of demersal shark rays catch from Java sea. Range Total Length (TL) of catch 73 – 200 cm and dominant TL catch range 101 – 125 cm. Morphologically character of wide head ratio with three lines of spine thorn on the head. Nearest genetic distance of 0.02 to Rhincobatushorkelii and 0.017 to R. australiae. Longest genetic distance of 0.243 to Potamotrygon motoro.

A serologic investigation of Brucella infection was performed in 7 species of cetaceans inhabiting along the coast of Japan. A total of 32 serum samples were examined by enzyme-linked immunosorbent assay (ELISA) using Brucella abortus and B. canis antigens. One serum sample from five melon-headed whales (Peponocephala electra) was positive for B. abortus. No serum sample showed positive for B. canis. The ELISA-positive melon-headed whale serum demonstrated a strong band appearance only against B. abortus antigens in Western blot analysis. Many detected bands were discrete, while some of them had a smeared appearance. The present results indicate that Brucella infection occurred in melon-headed whale population and the bacterial antigenicity is more similar to that of B. abortus than B. canis.

Harvest control rules (HCRs) for sustainable fishery management have been developed for data-limited fish species for which stock assessments cannot be conducted. However, HCRs have largely not considered mixed-species catches, as when fishing-effort data are widely pooled for numerous minor species in a multispecies fishery. Presently, a feedback HCR has been successfully applied in Japanese fisheries management. By combining management strategy evaluation with a simulation to generate mixed-species data from a multispecies fishery that assume constant catchability (q) among species, we evaluated the performance of this feedback HCR and then compared its performance using species-specific data. In most cases, the biomass was controlled over that needed for maximum sustainable yield (MSY), and the fishing effort was under the fishing mortality consistent with achieving MSY (FMSY). However, for slow-growing species, the biomass might become lower than what is required to remain capable of producing MSY, even though fishing effort was controlled under FMSY. The results show that the feedback HCR is appropriate for multispecies fisheries management where only mixed-species data are available but with special monitoring for slow-growing minor species.

Studies on odontocetes (e.g., porpoises) have revealed that these animals may adaptively use vision. The present study examined the contributions of vision to the approaching behavior of the harbor porpoise (Phocoena phocoena). When a porpoise approached a target, the time-to-contact perceived by the animal and its trajectory with a visual impediment condition were compared with those in the control (no impediment) condition. The results suggested that approaching behavior to a stationary target was guided by the animal's evaluation of time-to-contact (τ), maintaining the time derivative of τ () at a constant value. A porpoise with visual deprivation exhibited grater τ value and a longer evaluation time before contact than a porpoise that was not blindfolded in the task of reaching for the target. Furthermore, the porpoise with a visual impediment changed its swimming trajectory toward a target less than the control, which appeared to adaptively adjust its approaching trajectory. These findings imply that the use of vision aided echolocation and enables precise control and alteration of the trajectory during the approach. The present study has implications for adaptive use of vision during approaching behavior in the harbor porpoise.

Studies on odontocetes (e.g., porpoises) have revealed that these animals may adaptively use vision. The present study examined the contributions of vision to the approaching behavior of the harbor porpoise (Phocoena phocoena). When a porpoise approached a target, the time-to-contact perceived by the animal and its trajectory with a visual impediment condition were compared with those in the control (no impediment) condition. The results suggested that approaching behavior to a stationary target was guided by the animal's evaluation of time-to-contact (tau), maintaining the time derivative of tau ((tau) Over dot) at a constant value. A porpoise with visual deprivation exhibited grater (tau) Over dot) value and a longer evaluation time before contact than a porpoise that was not blindfolded in the task of reaching for the target. Furthermore, the porpoise with a visual impediment changed its swimming trajectory toward a target less than the control, which appeared to adaptively adjust its approaching trajectory. These findings imply that the use of vision aided echolocation and enables precise control and alteration of the trajectory during the approach. The present study has implications for adaptive use of vision during approaching behavior in the harbor porpoise.

Shrimp products play a vital role in the international trade of fisheries products. The main suppliers for shrimp products are developing nations such as Vietnam, Thailand, Bangladesh, and other countries in Southeast Asia. Among them, Vietnam is one of the largest exporters of shrimp products, and developed countries, especially the United States (US), Europe, and Japan, are key importers of shrimp in the global market. An increase in the demand for shrimp products has led to the development of traceability regulations in developed countries. In this study, Pressure–State–Response (PSR) concepts are applied to evaluate the implementation responses of traceability regulations by exporting countries to meet the mandatory requirements of global markets. The evaluation was based on the prepared questions that were developed to allow comparison of specified indicators in the traceability regulations of importing countries and those of Vietnam. The examination showed that importing countries have introduced stringent traceability regulations via legislation and quality assurance practices. Regarding measures taken by exporting countries, Vietnam has introduced traceability regulations for both shrimp and other seafood products. Thus, Vietnamese regulations were found to satisfy the regulations of importing countries. However, the implementation of these regulations has faced a number of challenges, largely because of complicated of distribution channels, small-scale production, price discrimination, and a lack capital to apply for international certificates.

Systemic amyloidosis is rarely reported among cetaceans, and a surveillance dedicated for its occurrence across a certain geographic location has not been reported. Between 2013 and 2018, comprehensive gross and histopathologic examinations were conducted on 54 animals comprising 11 species of stranded and bycaught cetaceans in Hokkaido, Japan. Systemic amyloidosis was diagnosed in 2 out of 3 Stejneger’s beaked whales (Mesoplodon stejnegeri), through Congo red staining and immunohistochemistry for amyloid A. The kidney and gastrointestinal tract had the largest amounts of amyloid deposits, representing a previously undescribed organ distribution in the species. The current study demonstrates the possibility of Stejneger’s beaked whales being prone to the development of systemic amyloidosis, and highlights the need for further investigations.

Traceability is considered the most important requirement for shrimp products exported to global markets. However, implementing traceability in shrimp-exporting countries is challenging because of limited production at the local supply chain and lack of financial welfare awareness. This study aims to investigate the expected farm-gate price for traceability implementation using a double-bound dichotomous choice experiment. The censored regression model is used to estimate the factors influencing the anticipated farm-gate price of shrimp farmers. The survey was conducted in Ca Mau Province, Vietnam, by interviewing 71 Penaeus monodon Fabricius, 1798, and 43 Penaeus vannamei Boone, 1931, farmers. To implement traceability, P. monodon farmers estimated the farm-gate price at 10.17 USD.kg-1 , while P. vannamei farmers expected 6.18 USD.kg-1 . Application of international quality assurance certifications, willingness to implement traceability, land used, culture methods, shrimp species, current farm-gate price, and variable costs affected the expected farm-gate price. The attractive anticipated farm-gate price compensated for the negative influence of applying international quality assurance certifications, indicating that the farmers were willing to implement traceability. This suggests that the application of certifications increased the ability to implement traceability in the shrimp supply chain. The attractive farm-gate price for certified shrimp products would enhance their willingness to implement the traceability of shrimp products.

Bycatch of harbour porpoises (Phocoena phocoena) by gillnets is a recognised threat to populations. To develop effective mitigation measures, understanding the mechanics of bycatch is essential. Previous studies in experimental conditions suggested foraging activity is an important factor influencing porpoises’ reaction to gillnets. We acoustically observed the behaviour of wild harbour porpoises around a bottom-gillnet set-up in a commercial fishing ground, especially foraging activity. Passive acoustic event recorders (A-tags) were fixed to the ends of the gillnet, and recorded for 1 392 hours. Although harbour porpoises frequently and repeatedly appeared around the net each day, incidental bycatch occurred only three times during the observations. The stomach contents of two individuals contained mainlyAmmodytessp., which were observable around the bottom-gillnet but not targeted by the fishery. A total of 276 foraging incidents were acoustically detected, and 78.2% of the foraging activity was in the bottom layer (deeper than 25 m). Porpoises appeared around the net with more frequency on the day of a bycatch incident than on the days without bycatch. These results suggest that the harbour porpoises appeared around the bottom-gillnet to forage on fish distributed in the fishing ground, but not captured by this bottom-gillnet. Thus, porpoises face the risk of becoming entangled when foraging near a gillnet, with the probability of bycatch simply increasing with the length of time spent near the net. Bycatch mitigation measures are discussed.

Striped dolphins (Stenella coeruleoalba) mass-stranded on 26 April 2013 at Minamisatsuma, Kagoshima Prefecture, in southern Japan (East China Sea). The diet of the mass-stranded striped dolphins was investigated to reveal their foraging pattern through analyses of the stomach contents and stable isotopes in muscle. Of 26 stomachs sampled, 25 contained hard parts of prey animals; no fleshy remains were found in any of the stomachs. The identified prey species represented four cephalopod families: Loliginidae, Onychoteuthidae, Histioteuthidae, and Ommastrephidae. Among these, ommastrephids had the highest abundance (42.4%) and frequency of occurrence (69.2%). A chi-square test revealed that the prey species consumed did not significantly differ between male and female dolphins, although deeper-water squids (Onychoteuthidae and Histioteuthidae) appeared only in the stomachs of females. The values of δ13C ranged from –20.4 to –17.0‰ (mean ± SD: –18.2 ± 0.9‰), and values of δ15N ranged from 10.2 to 12.5‰ (10.8 ± 0.5‰), with a significant difference in δ15N between sexes (P < 0.05).

Even though the cetacean tapeworm Diphyllobothrium stemmacephalum occurs in both cold and warm waters, human infections and final host occurrences have been confined to temperate areas in and near Japan. We recently obtained a strobila of this cestode that was excreted from a harbor porpoise accidentally caught offshore of Hokkaido of northern Japan. Genetic analysis of 28S rDNA and cox1 genes confirmed that the cestode was D. stemmacephalum. Our finding sets the northernmost record of D. stemmacephalum in the western Pacific, suggesting that the risk of human infections by this parasite in northern Japan deserves further attention.

Levels and profiles of naturally produced halogenated bipyrroles (Br4Cl2-DBP and Cl7-MBP), methoxylated tetrabromodiphenyl ethers (6-MeO-BDE47), anthropogenic perfluoroalkyl substances (PFASs) and legacy persistent organic pollutants (POPs) were investigated in the livers of 14 cetaceans from the Sea of Japan and the North Pacific Ocean. The concentrations of Br4Cl2-DBP (4 to 4900 ng/g-wet), Cl7-MBP (16 to 3960 ng/g-wet) and 6-MeO-BDE47 (7 to 190 ng/g-wet) were higher in the order of killer whales > toothed whales > baleen whales. Profiles of PFASs were dominated by perfluoroundecanoic and perfluorotridecanoic acids (10 to 540 ng/g-wet), sum of which accounted for 70% of total measured PFASs. Regional difference was observed for Cl7-MBP and PFASs, which were higher in the Sea of Japan, whereas Br4Cl2-DBP was in the North Pacific Ocean. Specific accumulation pattern of these natural contaminants in cetaceans around northern Japan could help compare the exposure profile of PFASs and POPs among other geographic regions.

Harbor porpoises (Phocoena phocoena) are often captured as bycatch in set net fisheries, which may have a large impact on their population and reduces the efficiency of fishing operations. Therefore, this study aimed to use passive acoustic monitoring using “A-tag” stereo acoustic data loggers to observe the presence and movement of harbor porpoises in two large set nets off Usujiri, Hakodate, Hokkaido, Japan, from April to May 2013–2015. Bycatch of harbor porpoises in the set nets was surveyed from onboard the set net fishing boat. Harbor porpoises were observed in the final trap of the set net on 10 separate days; however, bycatch was confirmed only once. These results indicate that the number of harbor porpoises captured as bycatch represents only a fraction of the number that are present in the set net, demonstrating their ability to escape from the net.

This study investigated accumulation of perfluoroalkyl substances (PFASs), persistent organochlorines (OCs), and naturally produced halogenated compounds (NHCs), including brominated methylbipyrroles and methoxylated bromodiphenyl ethers, in liver, blood, and blubber from Dall's porpoises (Phocoenoides dalli) and harbor porpoises (Phocoena phocoena) stranded in Hokkaido, northern Japan. Profiles of the PFASs were dominated by perfluoroundecanoic acid and perfluorotridecanoic acid, both of which accounted for 70% of the total measured PFAS concentrations in both porpoise species. The mean concentrations of the ∑PFCA were 573ng/g wet weight (ng/g-wet) in liver, 62ng/g-wet in whole blood, and 28ng/g-wet in blubber from the Dall's porpoises, and were significantly higher (p0.05) than those in the harbor porpoises. The hepatic concentrations of perfluorooctane sulfonate (PFOS) were14ng/g-wet, and accounted for only 3% of the total measured PFASs. The profiles of PFASs in the porpoises resembled those in fish species in this area, implying a common source of exposure to PFASs in East Asia. On the other hand, in the blubber of Dall's porpoises, NHCs were dominated by 2,3,3',4,4',5,5'-heptachloro-1'-methyl-1,2'-bipyrrole (867ng/g-wet), 5,5'-dichloro-1,1'-dimethyl-3,3',4,4'-tetrabromo-2,2'-bipyrrole (481ng/g-wet), and 6-methoxy-2,2',4,4'-tetrabromodiphenyl ether (30ng/g-wet), which were present at higher concentrations than in harbor porpoises. Factor analysis with varimax rotation revealed that factor 1 had higher eigenvectors (element in eigenvalues) for long-chain PFCAs and PFOS, which was found in the highest concentrations in the liver, whereas factor 2 was mainly associated with lipid soluble NHCs and OCs in both species. No correlations were observed between long-chain PFCAs and NHCs in the porpoises, probably because of the different sources and accumulation kinetics. Future research should assess the temporal trends and long-term effects of PFASs and NHCs in the tissues of mammals from the Asia-Pacific region.

Overfishing can affect life history traits, resulting in population collapse and oftentimes a decrease in length-at-age and maturation size in fish populations. However, little is known about the recovery mechanisms and time scales of these traits in exploited wild populations. In the study reported here, we documented long-term shifts in growth and mature size in Miyabe charr Salvelinus malma miyabei associated with a history of recreational fishing in Lake Shikaribetsu for approximately 80 years. Downsizing in the charr was observed when the charr population collapsed due to intensive recreational fishing. However, subsequent moratoriums and the introduction of fishing regulations, especially the implementation of a catch-and-release policy, during the following 10–30 years facilitated the recovery of population size, length-at-age and mature fish size. This study provides important insights into the biological changes and required recovery time scales of a heavily harvested population and supports management and conservation strategies.

Fisheries closure has been used as a fisheries management tool to protect species that need to be conserved. A commonly used type is fixed closure (FC), which specifies the closure area and period in advance and does not change after that decision is made. It has been claimed that FC is not effective for the management of migratory species, because it is difficult for FC to respond to uncertainties in the predicted distribution of species. Recently, real-time closure (RTC) has been introduced to address this issue. However, the use of RTC is still limited, because its benefits compared with FC have not been evaluated sufficiently. In this study, we conducted simple simulations to evaluate the efficiency of RTC to respond to uncertainties in the movement of migratory species. In terms of the protection of migratory species, the mean performance index of RTC was generally higher than that of FC, and the mean performance index of FC tended to decrease with greater uncertainty of species movement. We also estimated the extent of the reduction of the closure period by applying RTC instead of FC. The results of this study indicate that RTC is an efficient method of fisheries closure, and provide quantitative information to guide the use of RTC instead of FC.

Groupers (family Epinephelidae, subfamily Epinephelinae) are reef fishes of high value as food resources that generate export revenue to Sri Lanka. Yet, with less attention and poor resource management, grouper population dynamics remain understudied. This paper investigates the temporal variation of grouper species on the continental shelf of Sri Lanka in relation to seasonal, regional, and seafloor depth variables using data based on quantitative sampling of demersal fish conducted in 1978, 1979, 1980, and 2018 with a bottom trawl on the R/V Dr. Fridtjof Nansen, where the authors joined the 2018 survey. A total of 277 trawl samples were included in the analysis. The analysis of variance of all the grouper species found that the average density significantly declined from 0.89 t/NM2 (tonnes per square nautical mile) in 1979 to 0.28 t/NM2 in 2018. The contribution of groupers to the total catch (by weight) was also higher in 1979 (9.06 %) than in 2018 (1.28 %). The distribution patterns significantly differed among the six regions of the Sri Lankan shelf. In addition, seafloor depth was negatively correlated with grouper density. The results point to an urgent need for better management and conservation of the grouper resources.

The genus Anisakis is a well-known group of nematodes that parasitize cetaceans as the final host and cause mucosal damage to their stomach. However, little has been done to precisely identify the nematodes recovered from the final hosts, especially in the Western Pacific, because of taxonomic confusion about the discrimination of sibling species and the difficulties of obtaining specimens from cetaceans. We describe the results of genetic identification and histopathological observations of specimens recovered from an ulcerated lesion and stomach contents in the forestomach of a female harbor porpoise accidentally caught by a set net fishery in Usujiri, southern Hokkaido, Japan. All the specimens arbitrarily collected from the lesion and stomach contents were identified as Anisakis simplex sensu stricto according to their ITS rDNA sequences. The size of the ulcer was approximately 6.3 mm in diameter and it was infected with 119 individual nematodes, mostly consisting of L3 and L4 stage larvae (95.0%). Histological sections were characterized by a locally extensive ulcer with the parasites penetrating into the muscularis externa that caused a thickening of the surrounding mucosa.

Recreational angling is a popular leisure activity globally and can be a threat or useful conservation tool depending on the management strategy. Miyabe charr Salvelinus malma miyabei is an endemic fish that inhabits Lake Shikaribetsu, and a management program was established to harmonise recreational fishery and conservation. To examine the suitability of this program, population assessment was conducted with the cooperation of anglers. The population size in 2014 as assessed by tag-and-release angling was estimated to be 105,300 [95% confidence interval (CI) 37,300-178,600], much higher than the reported estimate in 1995. Further, angling mortality was estimated to be quite low. Moreover, no decreasing population trend was detected on analysing 8 years of anglers' catch data. Consequently, angling has facilitated stock assessments of Miyabe charr under the current program. This case is a good example of recreational angling acting as a conservation tool under appropriate management.

We performed the first known study of polychlorinated biphenyls (PCBs) concentrations and patterns in the blubber and liver of a Hubbs' beaked whale. Samples were pretreated with Supeldean (TM) sulfoxide and Discovery (R) Ag-ION solid phase extraction cartridges to remove whale oil. PCB concentrations in the blubber and liver were 13,000 and 7300 ng/g lipid, respectively. Highly poisonous congeners such as dioxin-like (DL) PCBs tended to accumulate in the liver. The toxic equivalents (TEQ) of DL-PCBs in the liver (740 pg-TEQ/g lipid) were higher than those in the blubber (74 pg-TEQ/g lipid). The blubber and liver samples showed that hexachlorinated biphenyls were dominant among homologues, and PCB-153 was dominant among congeners. Several congeners accumulated disproportionately in the blubber and the liver (PCB-28, 52, 74, 99, and 118), while others did not persist (PCB-31, 70, and 110). This indicates that PCBs are metabolized differently according to their specific composition. (C) 2016 Elsevier Ltd. All rights reserved.

Two types of Berardius are recognised by local whalers in Hokkaido, Japan. The first is the ordinary Baird’s beaked whale, B. bairdii, whereas the other is much smaller and entirely black. Previous molecular phylogenetic analyses revealed that the black type is one recognisable taxonomic unit within the Berardius clade but is distinct from the two known Berardius species. To determine the characteristics of the black type, we summarised external morphology and skull osteometric data obtained from four individuals, which included three individuals from Hokkaido and one additional individual from the United States National Museum of Natural History collection. The whales differed from all of their congeners by having the following unique characters: a substantially smaller body size of physically mature individuals, proportionately shorter beak, and darker body colour. Thus, we conclude that the whales are a third Berardius species.

Sri Lankan marine fishery resources were not assessed and updated for the last four decades. A comprehensive survey was performed by R.V. Dr. Fridtjof Nansen, starting from June 24 to July 16, 2018. Variations of fish density and diversity on the continental shelf of Sri Lanka were determined by region (East and West) and depth (20–50 m and 50–100 m) using 65 trawl samples collected. Associations between ichthyofauna, ecological parameters, and hydrographic variables (temperature, salinity, and oxygen) were determined. There were 620 species from 137 different families observed during the survey, with family Myctophidae being the most dominant with the highest number of individuals caught from all station (24.61% out of the total number of individuals) while the most represented families by density (t/NM2) were Carangidae (8.01%). A total of 440 species were found in the East region compared to 385 species in the West region; the density of fish was 1.3 times higher in the East region (9.00 ± 1.08 t/NM2) compared to the West region (6.85 ± 1.40 t/NM2). Similarly, the East region was 1.3 higher in the Shannon Wiener’s Diversity Index (SWDI) than the West region. Shallow-water (20–50 m) area has been reported as more diverse and denser than deep-water (50–100 m). Canonical correlation analysis showed a positive association of fish density with oxygen and a negative with temperature and salinity. This study would be an invaluable baseline for monitoring future changes and preparing recommendations and management action plans.

This study investigates the impact of the application of quality assurance certification on the origin traceability of shrimp exports in the Vietnamese Mekong Delta region. The primary data was investigated in 2018, which covered the whole supply chain of shrimp production such as farmers, collectors, distributors, processing factories. Descriptive statistics are utilized to analyze and compare the differences in the supply chain and product origin traceability between certified and non-certified shrimps. The willingness of farmers to embrace product origin traceability of certified and non-certified shrimps is also analyzed. The results show that certified farmers indicate a higher possibility of traceability due to proper monitoring and management essential to traceability. The application of international quality assurance certification of shrimp farmers increases awareness and willingness to implement origin traceability. The result proves the effectiveness of the collaboration between the farmers and processing factories in the implementation of traceability in the entire supply chain.

The present study examined the factors influencing catch per unit effort (CPUE) and standardized the CPUE of sockeye salmon (Oncorhynchus nerka) from offshore angling in Lake Toya, northern Japan. A generalized linear model (GLM), based on a negative binomial error distribution, was used to standardize the catch-and-effort data collected from anglers, using questionnaires and interview surveys during the fishing season (June) in 1998, 1999 and 2001–2012. Year, week, fishing area, number of fishing rods, fishing duration and Year × Week were the factors that significantly (P

Dall's porpoise (Phocoenoides dalli) is one of most common North Pacific porpoise species, for which information on sound-emitting processes is limited. To evaluate the mechanism of click emission in the head of this porpoise, the distribution of acoustic impedance in head tissues was calculated using density and Young's modulus'which is a measure of linear resistance to linear compression. Two Dall's porpoise heads were examined: one for macroscopic dissection, and one for investigating the distribution of acoustic impedance calculated from CT-measured density, and Young's modulus measured by creep meter. Acoustic impedance increased from the dorsal bursae to the melon's emitting surface, with impedance matching observed at the boundary between the emitting surface and seawater, and was more similar in distribution to Young's modulus than it was to density. The distribution of acoustic impedance differed from that of harbor porpoise (Phocoena phocoena), despite similarities in the sound-producing organs in the heads of Dall's and harbor porpoises. A comparison of the physical properties of Dall's and harbor porpoise head tissues suggests that hypertrophic vestibular sacs and an oval emitting surface are common characteristics in Phocoenidae.

We analyzed radiocesium (134Cs and 137Cs) levels in the muscle tissue of several odontocetes and mysticetes stranded on the coast of Hok kaido (the northernmost island of Japan) in 2011 and 2012, fol lowing the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in March 2011. Since most of the radiocesium from the FDNPP was released into the western North Pacific Ocean and carried eastward from the Japan coast, there was little radiocesium contamination in the seawater around Hok kaido. Hokka ido is surrounded by the North Pacific Ocean, the Japan Sea, and the Okhotsk Sea, but radiocesium was predominantly detected in the cetaceans stranded along the North Pacific coast between June and October 2011. Among the stranded cetaceans, which included the Pacific white-sided dolphin, harbour porpoise and Dall’s porpoise (odontocetes) as well as the common minke whale and humpback whale (mysti cetes), the highest level of contamination was found in a common minke whale. The radiocesium contamination of these ceta ceans suggests that they moved seasonally from the south of Hokkaido, particularly through the contaminated area of the western North Pacific Ocean. The radiocesium levels in the tissues of these animals is likely a result of the contamination level of the seawater along their travel route, rather than their trophic level, because of the sudden changes in radiocesium transport and diffusion in seawater that occurred in 2011.

The process by which sound is propagated in the head of a toothed whale is still a subject of discussion. Investigating the distribution of acoustic impedance calculated by density and Young's modulus is effective for quantitative comprehension because acoustic impedance determines the reflection coefficient of a sound wave. However, the sound propagation process of the toothed whale has been mainly examined by either anatomical techniques or the measurement of density or sound velocity. In the current study, the acoustic impedance of head tissue of harbor porpoise was measured. Results of this study should be a helpful information for further discussion about the relationship between the structure of sound-producing organ and clicks property. (C) 2015 Acoustical Society of America.

The genus Mesoplodon (Cetacea: Odontoceti: Ziphiidae) is one of the few cetacean genera with the karyotype 2n = 42. The 2n = 42 karyotype of M. europaeus and M. carlhubbsi is largely consistent with the general cetacean karyotype 2n = 44, although other 2n = 42 karyotypes do not exhibit clear homologies with the general cetacean karyotype. Therefore, the chromosomes of Mesoplodon species may be the key to understanding cetacean karyological evolution. In the present study, the male karyotypes of M. stejnegeri and M. carlhubbsi were examined. In both species, the diploid number of the male karyotype was 42. Both species had the following characteristics: 1) a huge subtelocentric X chromosome with a large C-block; 2) a small metacentric Y chromosome; 3) nucleolus organizer regions (NORs) in the terminal regions of a large autosome and one or two small metacentric autosomes; 4) small metacentric autosomes; 5) large submetacentric and subtelocentric autosomes; 6) less accumulated C-heterochromatin in the centromeric region; and 7) heteromorphism in C-heterochromatin accumulation between homologues. Characteristics 1 and 3 are peculiar to only the karyotypes of Mesoplodon species, whereas characteristics 4, 5, 6, and 7 are also found in the species with the general cetacean karyotype 2n = 44.

We analyzed δ(13)C, δ(15)N and δ(18)O in the muscle and liver from killer whales stranded on the coast of Japan. The δ(15)N values in the muscle samples from calves were apparently higher than those in their lactating mothers, suggesting that nursing may result in the higher δ(15)N values in the muscle samples of calves. The δ(15)N value in the muscle samples of male and female whales, except for the calves, were positively correlated with the δ(13)C values and body length, suggesting that the increases in δ(15)N were due to the growth of the whales and increase in their trophic level. In contrast, the δ(18)O values in the muscle samples of female whales except for the calves were negatively correlated with the δ(13)C and δ(15)N values. The δ(18)O may be lower in whales occupying higher trophic positions (δ(15)N), although it might also be affected by geographic and climatic conditions.

The catch forecast is important for fisheries activities. Previous research has tried to improve forecast accuracy. However the forecast accuracy does not directly correspond to the forecast benefit, and an inaccurate forecast could be more beneficial than accurate one. Herein as part of the forecast utility, predictability was evaluated using information theory. Mutual information (MI) was used as index of predictability. MI denotes a reduction in uncertainty when a forecast is taken into account. Adding this, hit ratio (HR) and relative entropy (R) were used as consistency indices. HR denotes a frequency for which the predicted values are consistent with the actual values, and R denotes the distance of the probability distribution between the actual and forecasted fishing conditions. As an application, the long-term change-ratio forecasts in 1972–2009 (n = 36), short-term change-ratio forecasts (n = 34), and short-term level forecasts (n = 33) in 2004–2009 of Pacific saury Cololabis saira fishery were evaluated. The order of MI, HR, and R varied between these forecasts, indicating that forecast predictability and consistency do not correspond. Monitoring multiple indices would improve forecasting systems.

Information on accumulation of halogenated phenolic contaminants in the blood of marine mammal is limited. The present study, we determined the residue levels and patterns of chlorinated and brominated phenolic contaminants (OH-PCBs, OH-PBDEs and bromophenols) in the blood collected from pinnipeds (northern fur seal, spotted seal, Steller sea lion and ribbon seal) and small cetaceans (harbor porpoise and Dall's porpoise) from Japanese coastal waters. Concentrations of PCBs and OH-PCBs found in pinnipeds were the same as in small cetaceans living in the same coastal area. However, significantly lower concentrations of brominated compounds (PBDEs, MeO-PBDEs, OH-PBDEs) were found in the blood of pinnipeds than the levels found in cetacean species which live same area (p