出口 智広

Abstract Long-lived territorial bird populations often consist of a few territorial breeding adults and many nonbreeding individuals. Some populations are threatened by anthropogenic activities, because of human conflicts for high-quality breeding habitat. Therefore, habitat restoration projects have been widely implemented to improve avian population status. In conjunction with habitat restoration, conservation translocations have been increasingly implemented. Adequate nonbreeder survival can be a key factor in the success of these attempts because nonbreeding birds may represent reservoirs for the replacement of breeders. The maintenance of breeding pair numbers is also influenced by the transition rate of nonbreeders to breeders. The reintroduction of Oriental Stork (Ciconia boyciana), a long-lived, territorial, endangered species, was initiated in Japan in 2005 using captive birds in hopes of increasing the population’s use of restored habitat. Our objective of this study was to elucidate the factors determining reintroduced stork survival and recruitment to the breeding populations. We estimated the survival rate and breeding participation rate by sex, age, generation, wild-born or not, haplotypes, and breeding status in storks reintroduced during 2005–2022 using Bayesian hierarchical models. There was no significant difference in survival rate between nonbreeders and breeders. However, the survival rate was lower in wild-born birds than released birds, which may be related to the longer-distance natal dispersal of new generations. Accelerated habitat restoration around breeding areas and preventive measures for collision with human-built structures should be implemented for the sustained growth of reintroduced populations. A low survival rate was also detected for a specific mitochondrial DNA (mtDNA) haplotype that accounts for the majority of the reintroduced population. This phenomenon might be explained by mtDNA-encoded mutations. Moreover, captive breeding and release history might contribute to an increase in the proportion of this haplotype in the wild.

Marine protected areas (MPAs), particularly large MPAs, are increasing in number and size around the globe in part to facilitate the conservation of marine megafauna under the assumption that large-scale MPAs better align with vagile life histories; however, this alignment is not well established. Using a global tracking dataset from 36 species across five taxa, chosen to reflect the span of home range size in highly mobile marine megafauna, we show most MPAs are too small to encompass complete home ranges of most species. Based on size alone, 40% of existing MPAs could encompass the home ranges of the smallest ranged species, while only < 1% of existing MPAs could encompass those of the largest ranged species. Further, where home ranges and MPAs overlapped in real geographic space, MPAs encompassed < 5% of core areas used by all species. Despite most home ranges of mobile marine megafauna being much larger than existing MPAs, we demonstrate how benefits from MPAs are still likely to accrue by targeting seasonal aggregations and critical life history stages and through other management techniques.

Abstract Understanding encounters between marine predators and fisheries across national borders and outside national jurisdictions offers new perspectives on unwanted interactions to inform ocean management and predator conservation. Although seabird–fisheries overlap has been documented at many scales, remote identification of vessel encounters has lagged because vessel movement data often are lacking. Here, we reveal albatrosses–fisheries associations throughout the North Pacific Ocean. We identified commercial fishing operations using Global Fishing Watch data and algorithms to detect fishing vessels. We compiled GPS tracks of adult black‐footed Phoebastria nigripes and Laysan Phoebastriaimmutabilis albatrosses, and juvenile short‐tailed albatrosses Phoebastria albatrus. We quantified albatrosses‐vessel encounters based on the assumed distance that birds perceive a vessel (≤30 km), and associations when birds approached vessels (≤3 km). For each event we quantified bird behaviour, environmental conditions and vessel characteristics and then applied Boosted Regression Tree models to identify drivers and the duration of these associations. In regions of greater fishing effort short‐tailed and Laysan albatrosses associated with fishing vessels more frequently. However, fishing method (e.g. longline, trawl) and flag nation did not influence association prevalence nor the duration short‐tailed albatrosses attended fishing vessels. Laysan albatrosses were more likely to approach longer vessels. Black‐footed albatrosses were the most likely to approach vessels (61.9%), but limited vessel encounters (n = 21) prevented evaluation of meaningful explanatory models for this species of high bycatch concern. Temporal variables (time of day and month) and bird behavioural state helped explain when short‐tailed albatrosses were in close proximity to a vessel, but environmental conditions were more important for explaining interaction duration. Laysan albatrosses were more likely to associate with vessels while searching and during the last 60% (by time) of their trips. Our results provide specific species–fisheries insight regarding contributing factors of high‐risk associations that could lead to bycatch of albatrosses within national waters and on the high seas. Policy implications. Given the availability of Global Fishing Watch data, our analysis can be applied to other marine predators—if tracking data are available—to identify spatio‐temporal patterns, vessel specific attributes and predator behaviours associated with fishing vessel associations, thus enabling predictive modelling and targeted mitigation measures.

地球規模の気候変動が鳥類の渡り・繁殖に及ぼす影響の有無は，ヨーロッパや北米に生息する種について数多く報告されているが，アジアにおける報告は著しく乏しい．本研究では，大規模な気候変動が生じたこの50年の間に，日本に訪れるツバメの渡り時期，繁殖時期，繁殖成績が変化したかどうかを検討するため，1961～1971年の11年間（以下，1960年代）と，2000～2010年の11年間（以下，2000年代）の標識調査データを比較解析した．日別放鳥数の頻度分布において，成鳥の急増時期は2000年代の方が半月ほど早まったが，急減時期は変わっていなかった．幼鳥については，2000年代と1960年代の頻度分布はほぼ一致した．巣内雛については，急増時期が2000年代の方が半月ほど早まっていた．成鳥に対する幼鳥の放鳥数の比率は2000年代の方がやや減少していた．これらの結果は，ツバメの飛来時期・繁殖開始時期は2000年代の方が早まったが，渡去時期は両期間で変わっておらず，また繁殖成績は2000年代の方が低下したことを示唆している．飛来時期と繁殖開始時期については，調査環境や調査時期の影響も考えられるが，多くの既有の知見と一致することから，比較結果にはある程度の妥当性が判断された．一方，渡去時期や繁殖成績については，国土スケールの長期変動解析に有効な情報が他に乏しく，標識調査情報が重要なデータになると言える．

Many ribbon seals (Phoca fasciata) appear in winter in Nemuro Strait, eastern Hokkaido. We propose that their presence is partly related to an exploitation of the large numbers of spawning walleye pollock (Theragra chalcogramma). To investigate feeding habits of ribbon seals in winter, we sampled stomachs from seals for prey composition and size taken in the strait from February–April 1996–1998. Nine fish and five squid species were identified from sixty-four seal stomachs. Walleye pollock and magistrate armhook squid (Berryteuthis magister) were predominant in the diet of seals each year. The index of relative importance of prey showed that walleye pollock was the most dominant prey item. Most pollock eaten by seals had reached maturity. Prey distribution suggested that ribbon seals foraged in the intermediate-bottom layer of the continental slope water. No differences were found between prey composition and size of male and female ribbon seals. Subadult and adult ribbon seals consumed more pollock and less squid than young seals, which also tended to consume smaller pollock. Pinpoint lanternfish (Lampanyctus regalis) and saffron cod (Eleginus gracilis) occurred only in stomachs of adults and young, respectively. Foraging technique and diving ability may explain the differences in prey composition and size among seal age classes.<br>

Daily measurement of chick mass could be a useful method to estimate daily food intake under the assumption that the effects of the body mass on daily mass increment do not differ between chicks receiving different amount of food. To evaluate this assumption, 40g and 60g anchovy per day were fed to Rhinoceros Auklets chicks in semi-captivity. Negative relationships between chick mass and daily mass increment were found in 40g-and 60g-fed chicks. There was no significant difference in the slope of regression equation between 40g-fed chicks (-0.037±0.018) and 60g-fed chicks (-0.041±0.016). The intercept in 60g fed chicks (17.578±3.491g) was larger than that in 40g fed chicks (10.950±3.491g). Therefore, the daily amounts of food intake in Rhinoceros Auklet chicks can be estimated from body mass and daily mass increment.