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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.

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.

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.

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.

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

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.

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.

Cohort analysis (also known as virtual population analysis) is a method of population reconstruction from age-specific harvest data. Because cohort analysis requires data over a whole life span to reconstruct a population for a single year, this method is impracticable for longer-lived animals. Three models are routinely combined by fisheries scientists to make cohort analysis more cost effective and to provide real-time estimates of population size; these models may be applied to large terrestrial mammal harvest data. Each model has unique assumptions about hunting mortality rates or age distributions, and the reliability of estimates depends on meeting these assumptions. In this study, we first tested previously used assumptions for these models through an analysis of long- term moose (Alces alces) harvest data, followed by an examination of the robustness of estimates for each moose age class. We developed practical ways to achieve more realistic assumptions for two of three models and showed that meeting these assumptions was more important in estimations of large terrestrial mammal population parameters than for fish population parameters. Therefore, we recommend compliance with assumptions of the three models for more reliable population estimates of large terrestrial mammals.

Lake Victoria is one of the African Great Lakes, and an important source of affordable protein food in the form of fish. It provides employment, income, and export earnings to the riparian communities. Despite this importance there are major concerns about the status and exploitation of the fisheries. This study assesses if current extraction rates/yield of Nile perch, Lates niloticus (L.), from Lake Victoria are sustainable for the foreseeable future. The paper reviews trends in catch and effort in the Nile perch fishery and models the expected scenarios using ECOPATH. The fishery exhibits, classic indicators of intensive fishing, erring towards overexploitation, including: (i) decline in total estimated catch of Nile perch in recent years from the peaks in the 1990s. This is coupled with a shift in contribution of catches from higher trophic level species (Nile perch) to lower trophic level (dagaa) species. (ii) Three major trends in the fishing effort are evident: (a) almost doubling of the number of fishers and fishing boats between 1990 and 2000, and the even greater expansion between 2000 and 2002; (b) a large scale increase in the number of gears operational in the lake; and (c) the propensity for use of illegal gears. (iii) Catch- per-unit-effort has declined from about 80 to 45 kg per boat day. (iv) Predictive modelling (ECOSIM) of the future of the Nile perch fisheries under a scenario of increased fishing effort suggests that the fisheries are unsustainable and will decline in the long term. It appears that the Nile perch stocks in the three riparian countries are under intense fishing pressure, and unless concerted action is taken, the potential for degradation of the resources is prevalent. In view of the importance of these fisheries, it is recommended that a precautionary approach to further intens-ification of the fisheries is adopted until such time empirical evidence shows that the fisheries are capable of further expansion and intensification. The main options for management are devolvement of responsibilities for the fisheries to the communities, enforcement of existing regulations, improved monitoring and data collection processes, reducing post-harvest losses and increasing the value of the products to the export market.

東北海域におけるマダラ資源に VPA を適用して得られた資源量推定値をもとに，トロール調査に基づく面積密度法による資源量推定に必要な漁獲効率を推定した。1 歳と 2 歳の漁獲効率はそれぞれ 0.54, 0.12 と大きな差がみられた。1 歳魚については調査範囲が生息域を網羅していることから，漁獲効率はトロール網の前にいた個体の入網率を反映した値であると考えられる。2 歳魚以上では，着底トロール調査が困難な岩礁域等にも生息することから，漁獲効率は入網率に加え，網との遭遇率の影響も受けていることが示唆された。

許容漁獲量制度が導入されている北海道噴火湾のケガニ資源について，資源管理方策を検討するため，甲長コホート解析（LPA）を適用し資源量推定を行うとともに，甲長に基づく YPR（YPRL）モデルを開発し，資源診断を行った。推定した資源量は回復傾向にはないものの，近年比較的安定していた。YPRL モデルにより資源診断した結果，当資源の許容漁獲量設定に用いている漁獲死亡係数は，F0.1 の 6 割程度で充分安全な値であった。以上のことから，当面は現状の管理基準に基づいた資源管理を継続すべきであると判断された。

Age-based population assessment is widely used, but there are cases where information on age or even body length of landed fish is difficult to collect. In the present study, the biomass and fishing mortality of the southern Hokkaido stock of Pacific cod Gadus macrocephalus was estimated directly from body weight composition, using weight-based virtual population analysis, from 1994 to 2000. The estimated biomass over 1 kg body weight was 5607 t in 1994 and increased to 7908 t in 2000. The increase was explained by an increase in recruitment.

We carried out mail and access point surveys to estimate the catch numbers, angling effort of recreational angling and the population of sockeye salmon Oncorhynchus nerka in Lake Toya in 1998 and 1999. The mail survey questions in questionnaires distributed to anglers with a recre- ational angling license included date of angling, caught fish species and size, and catch number. In the access point survey we also asked anglers if they had a license. We measured the fork length and weight of caught fish. The catch rate (catch number in a day by each angler) from both surveys showed no significant difference, suggesting no bias for the catch rate between surveys. The esti- mated total angling effort was 1760 people (1998), and 1516 people (1999). The estimated recre- ational catch was 28 889 (1998) and 5455 (1999), that is, two or three times larger than the commercial catch. The fish population was estimated by using the DeLury method as 60 262 (1998) and 10 806 (1999). The total exploitation rate was 62% (1998) and 78% (1999). The size of caught fish was much larger in 1999 than 1998 because of the difference in age composition.

津軽海峡の鯨類に関する知見は極めて乏しい。本研究では津軽海峡の鯨類の鯨種，それらの出現頻度を明らかにするため，2003年4月から2004年11月まで函館・青森間を運行するフェリーからの目視調査を実施した。58日6,102kmの目視調査により，合計415群3,010 個体の鯨類の発見があった。発見はカマイルカが優占し，マイルカ，イシイルカ，ハンドウイルカ、ネズミイルカ、コビレゴンドウ等が発見された。カマイルカの来遊のピークは5～6月の年一回であった。

High biodiversity is the most remarkable characteristic of Lake Tanganyika including vertebrates, invertebrates, and plants. A few protected areas have been created along the lake to protect its biodiversity. However, limited studies have been carried out to ascertain their effectiveness. The current study aimed at assessing and comparing fish diversity and abundance of Lake Tanganyika in a protected area (Mahale Mountains National Park (MMNP)) and unprotected areas surrounding it. The data were collected in the near shore zone at 5 m and 10 m depths using stationary visual census (SVC) technique. The protected area recorded higher fish richness and abundance than unprotected areas (P<0.05). It was concluded that the protected area is effective in conserving the fish diversity and abundance of the lake. However, more studies should be carried out regularly to explore the efficacy of the protected area in conservation of aquatic biodiversity and abundance.

底曳漁獲量からみたマダラの濃密な分布は, 太平洋では北海道の襟裳岬以東の海域, 北海道恵山沖および三陸沖の3つの海域にみられ, 日本海では, 青森・秋田県沖および山形県沖の2つの海域にみられた。月別1曳網当り漁獲量を用いて因子分析を行った結果, 襟裳岬以東海域, 北海道恵山沖および三陸沖の魚群はそれぞれ異なる変動傾向を示す魚群であった。また脊椎骨数の解析から, 襟裳以東海域は他海域より脊椎骨数が有意に多いことが分った。これらの結果と産卵場の知見を考慮すると, 太平洋側海域には襟裳岬以東群, 陸奥湾・恵山沖群および三陸沖群の3つの系群が存在すると結論された。