2026年5月26日(火)　13:15～ @seminar room + zoom

Date: 26th May.  (Tue)  13:15-  @seminar room + zoom 

Presenter 1 ： Taiga Mukai

Chairperson：Sara Kim

Title： My past research and future research plan
Language:   Slides in English, talk in Japanese
Abstract：

[Past research]

In my undergraduate research, I examined migration patterns and 20-year trends of four cetacean species in the Tsugaru Strait. Utilizing visual survey data collected from Tsugaru Kaikyo Ferry since 2003, I calculated monthly and annual encounter rates to analyze their seasonality, interannual trends, and geographic distributions across four regions. Overall, cetacean occurrence in the Tsugaru Strait is concentrated from winter to spring. The 20-year accumulation of data enabled the detection of migration patterns and long-term trends, even for species with fewer observations.

 [Future research plan]

For my master’s course, I plan to investigate the migration patterns of Sato's beaked whales (Berardius minimus) off Rausu, Hokkaido. Described as a new species in 2019, fundamental ecological information on this ziphiid species remains extremely scarce. Ziphiids primarily feed on deep-sea cephalopods and fish, making them difficult to detect visually due to their long dives and brief surface intervals. While a previous study on the Kunashiri side of the Nemuro Strait reported frequent sightings at depths of 400–600 m. However, information regarding their peak seasons, group sizes, surfacing behaviors, depth, and slope preferences is limited. To address this, I conducted a visual survey from both land and whale watching boats from April 22 to May 20, 2026, and plan to continue surveys during their migration season in 2027. Photo and video records were collected to estimate group sizes and surfacing behaviors, and vessel-based encounters recorded depth and temperature. In next year's survey, I will utilize drones to obtain coordinates from land, enabling more accurate tracking of group sizes, surface behaviors, and swimming formations. Furthermore, I will compare these findings with Baird's beaked whales (Berardius bairdii), which migrate to Rausu in autumn. Through these approaches, this study aims to clarify migration patterns of Sato's beaked whale off Rausu, ultimately providing a critical ecological foundation for its future conservation and management.

Presenter 2： Sara Kim

Chairperson：Taiga Mukai

Title： History and Current Understanding of Narwhal Populations in Greenland
Language:   Slide (English) Talk (Japanese)
Abstract：

This seminar presents a review of studies on narwhal (Monodon monoceros) populations and population structure. My research focuses on narwhals inhabiting the waters around Qaanaaq in northwestern Greenland. During my master’s program, I conduct acoustic analyses to investigate their behavior and distribution. In my doctoral research, I plan to examine population structure using whale lice (Cyamus monodontis) as a biological indicator.

To date, a variety of approaches have been applied to investigate narwhal populations, including genetic analyses and satellite tagging for tracking movements. These methods provide information at different spatial and temporal scales and have contributed to understanding patterns of distribution and population segregation.

However, population classifications are not always consistent across studies. Also, it is important to understand the positioning of populations in the focal study area. This presentation summarizes previous research, outlines the strengths and limitations of different approaches, and discusses how narwhal populations can be characterized.

2026年5月19日(火)　13:15～ @seminar room + zoom

Date: 19th May.  (Tue)  13:15-  @seminar room + zoom 

Presenter   ：Mayako Fujihara

Chairperson：Mayako Fujihara

Title：How to Navigate International Conferences and Joint Research Projects
Language:  English
Abstract:（English) Participating in international conferences is essential for promoting your research, gaining cutting-edge insights to refine your work, and building networks with global researchers for future research and career development. In this presentation, I will share how international conference participation has shaped my own career path. Additionally, I will provide a step-by-step guide on how to prepare for and navigate these conferences, offering practical tips for your next global leap. 

（日本語）国際学会への参加は、自身の研究を世界にアピールして最先端の知見を獲得し、研究をブラッシュアップするだけでなく、世界的な研究者とのネットワーキングやキャリア形成にとっても不可欠なものです。本発表では、私自身のキャリアパスにおいて国際学会への参加がどのような役割を果たしてきたかを紹介します。さらに、次の一歩を踏み出すための実践的なアドバイスとして、国際学会への具体的な参加手順についてもレクチャーします。  

2026年4月28日(火)　13:15～ @seminar room + zoom

Date: 28th April.  (Tue)  13:15-  @seminar room + zoom 

Presenter 1: Takayori Matsuoka

Chairperson: Ziyu Deng

Title: My past research and future research plan

Language: Slides in English, talk in Japanese

Abstract:

[Past research]

In my undergraduate research, I examined the characteristics of carbon and nitrogen stable isotope ratios across different tissues in green sea turtles to evaluate their suitability for analysis. Although this species has been widely studied, comparisons among tissues for isotope analysis remain limited, and sampling protocols have not been standardized. I conducted an experiment involving two bycaught green sea turtles, which were reared on a consistent diet for approximately two months. Samples of blood, claws, skin, and scutes were collected on two separate days with a one-month interval. The analysis revealed significant differences in isotope ratios among tissues. Furthermore, the results suggested that blood is relatively easy to process and provides stable, consistent data.

[Future research plan]

For my master’s course, I plan to investigate habitat selection of sea otters recolonizing the eastern coast of Hokkaido. In regions such as Alaska, sea otters are well known as keystone species that play an important role in marine ecosystems. Monitoring populations during recolonization is important not only for conservation but also for understanding their ecological impacts. Furthermore, identifying the factors influencing habitat selection is essential for predicting future distribution patterns. Previous studies have shown that sea otters typically select shallow waters, sheltered areas such as dense kelp forests or the leeward side of islands for resting, and foraging sites with high prey biomass per unit area. They are also known to favor complex coastal topographies. Research on sea otters in eastern Hokkaido has yielded results consistent with previous findings, such as the primary use of canopies composed of kelp, Sargassum, and seagrass (Phyllospadix iwatensis) as resting sites, foraging site selection based on prey preferences, and the maintenance of a constant distance between foraging and resting areas across all seasons. On the other hand, contrary to established knowledge, no significant correlation was found between habitat use and water depth or coastal complexity in eastern Hokkaido. This discrepancy is likely attributable to the differences in spatial and temporal scales between overseas studies and those conducted in this region.

Therefore, this study aims to re-evaluate the habitat selection of sea otters by aligning our research scale as closely as possible with those of overseas studies, while clarifying more detailed environmental requirements. We hypothesize that by extending the monitoring period and expanding the survey area, we can redefine the discrepancies between overseas findings and the current status of sea otters in eastern Hokkaido. Furthermore, we anticipate that long-term monitoring will enable a finer categorization of behaviors, leading to a comprehensive understanding of the factors driving their habitat selection.

Presenter 2: Ziyu Deng
Chairperson: matsuoka takayori
Title: My past research and future research plan
Language: Talk (Japanese), Slides (English)

Past research:

My undergraduate research investigated the seasonal reproductive development of the Pacific spadenose shark (Scoliodon macrorhynchos) in the southern Taiwan Strait. Through histological analysis of testicular structures, the study identified distinct developmental stages of spermatocytes and spermatids. The results revealed a clear reproductive seasonality, with testicular maturity peaking from August to December. These findings provided a critical biological foundation for the conservation and sustainable fisheries management of the species.

Research plan:

Tool use in sea otters (Enhydra lutris) provides a critical model for understanding the adaptive significance of animal tool use. Previous studies suggest that tool use can reduce the handling time of hard-shelled prey and improve foraging efficiency, defined here as the rate of net energy gain per unit time. Such behavior is often associated with limited food resources or strong competition. However, in Hokkaido, where sea otters have recently recolonized, population density remains relatively low and competitive pressure may be weak. As a result, the functional role of tool use in this system remains unclear.

This study aims to evaluate whether and under what conditions tool use enhances foraging efficiency in Hokkaido sea otters. Using behavioral observations, I will compare foraging efficiency between tool-use and non-tool-use events to quantify its impact. Additionally, I will sample local prey species to measure their energetic content and physical characteristics (e.g., shell hardness). By integrating these data, I will investigate how prey characteristics and foraging context relate to tool use, identifying the specific conditions under which this behavior is beneficial. This research will contribute to a better understanding of regional variations in sea otter foraging strategies and the environmental drivers of tool-use behavior.

Presenter 3: Eiichiro Ozasa
Chairperson: Sara Kim
Title: Interim report – Automatic detection of the dolphin vocalization, including snapping shrimp noise recorded in Mauritius
Language: Talk (Japanese), Slides (English)
Abstract: In this presentation, I will report on the progress of my research. Mauritius is known for its exceptional biodiversity, and the government of Mauritius has attempted to initiate blue economy policies for the sustainable use of ocean resources for socio-economic growth. Among these, cetaceans play an important ecological and economic role, particularly through marine tourism. However, coastal species are increasingly exposed to anthropogenic pressures. Cetaceans serve as umbrella species, and their conservation contributes to the preservation of broader marine biodiversity, therefore, monitoring of cetaceans is necessary to conserve the marine ecosystem. However, due to limited survey effort, there has been very little research on cetaceans in Mauritius, particularly in the eastern coast of the island. As a result, even basic information, such as species and seasonal occurrence, remains unclear. Passive Acoustic Monitoring (PAM) is a practical monitoring method for detecting cetacean vocalizations enabling the assessment of species presence and temporal occurrence, and providing insights into cetacean habitat use. This study aims to investigate temporal patterns of cetacean vocalization activity in the eastern coast of Mauritius using PAM, providing basic information for understanding habitat use in this data-limited region. The hydrophone was deployed on fish farm cages near the Mahebourg lagoon where is also an area used by tourist boats, and dolphins are occasionally observed there. Acoustic recordings were conducted continuously for 66 days, from December 31st, 2024, to March 7th, 2025, and a total of over 1400 hours of acoustic data were collected. As a result of the acoustic analysis, we found dolphin vocalizations frequently, but there are snapping shrimp as the background noise throughout the whole acoustic data, which are similar to dolphin vocalizations. To efficiently process this large dataset, I am developing an automatic detection tool to identify dolphin vocalizations by refining a detection tool already developed for the vocalizations of dugongs and dolphins. The detection tools in previous research include some acoustic parameters, but on the acoustic data recorded in Mauritius, due to the excessive background noise of snapping shrimp, it is necessary to adjust some parameters suitably. In this presentation, I will report how we developed the automatic detection tool with collaborators and discuss the accuracy of the tool.

2026年4月14日(火)　13:15～ @seminar room + zoom

Date: 14th April.  (Tue)  13:15-  @seminar room + zoom 

Presentation 1 ： WRC Seminar Explanation

Chairperson: Kristin

Presentation 2： WRC security workshop

Chairperson: Hideki Sugiura