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国際シンポジウム「明日の海と食を守る水産海洋サステナビリティ学」 >

Sustainability on seafood security and ocean ecosystem conservation

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タイトル: Sustainability on seafood security and ocean ecosystem conservation
その他のタイトル: Sustainability Sciences for Ocean Ecosystem Conservation and Seafood Security
食と海を守るためのサステナイビリティ科学
海洋生態系保全と水産食料安全保障のための持続可能性
著者: Kaeriyama, Masahide 著作を一覧する
発行日: 2009年11月 7日
引用: International Symposium on "Sustainability Science on Seafood and Ocean Ecosystem Conservation". 7 November 2009. Hakodate, Japan.
抄録: Marine food should be a renewable resource for humans. However, world fish catches have peaked since the 1990s, despite increase in aquaculture production. Fish provide more than 2.9 billion people with at least 15% of their animal protein intake (FAO, 2009). Tuna (Thunnus spp.) abundance decreased severely by overfishing since the 1980s (Myers and Worm, 2003). Bluefin tuna (T. thynnus) is already listed as a 'critical species' in the IUCN. Although production from aquaculture is increasing worldwide, many aquaculture programs cause destruction of aquatic ecosystems, such as destruction of mangrove forests due to the introduction of shrimp aquaculture over the last 20 years in Eastern Asia (Primavera et al., 2005), marine pollution and threats to marine food security (e.g. contaminants in farmed Atlantic salmon; Hites et al., 2004). Traditional fisheries science considers only fisheries, some consequences of which include fishing down marine food webs (Pauly et al., 1998), overfishing of tuna, tragedy of the commons, food mileage, ecosystem crashes and food pollution. A paradigm shift is needed from traditional fisheries science to a new ecological fisheries science and oceanography for protection of ocean ecosystems and human seafood resources for the well being of future generations. The objective of this presentation is to consider risk management, including adaptive management and precautionary principles based on the ecosystem approach for protecting marine ecosystem and seafood security. Carrying capacity and long-term climate change: Population dynamics of Pacific salmon (Oncorhynchus spp.) are directly affected by a number of stresses (climatic and human impacts) that need to be considered within an ecosystem context. A significant positive correlation was observed between the Aleutian Low Pressure Index (ALPI) and carrying capacity at the species level. Residual carrying capacity was significantly positively correlated with body size and negatively related to age at maturity in chum salmon (O. keta) as an example of a density-dependent effect (Kaeriyama, 2008). On the other hand, the biomass of wild chum salmon populations in the 1990s decreased to 50% of that in the 1930s, despite the significant increase in hatchery populations. This phenomenon suggests that the increased number of hatchery salmon impacted the reproductive value (e.g. fecundity) of wild populations. Global warming is affecting marine organisms. How will Pacific salmon be affected by global warming in the near future? Using the SRES-A1B scenario of the IPCC, it is possible to infer the global warming effect on chum salmon based on their optimal temperature for growth (8-12℃). This suggests that chum salmon would be brought into direct competition with other salmon populations, leading to decrease in the survival rate and population density-dependent effects because of reduction of distribution area, displacement to the north (e.g. the Arctic Ocean) and loss of migration routes (e.g. the Okhotsk Sea). Sustainable conservation management based on the ecosystem approach: The structure of ecosystems includes interaction between the abiotic environment and organism, while the function of ecosystems includes interaction between the abiotic environment and biodiversity. The aquatic ecosystem is subject to disturbance by natural factors and human impact. Recently, human impact has strongly affected the aquatic ecosystem (e.g. global warming, overfishing, habitat loss, creation of artificial river channels, dam construction and the negative effects of aquaculture and hatchery programs; Kaeriyama and Edpalina, 2004). We need to identify the limitations of fisheries management, focused at the population level, and establish sustainable conservation and management based on the integration of population level approaches within a wider ecosystem-based approach. Definitions of an ecosystem-based approach to fisheries management have been proposed by several authors (NRC, 1999, Witherell et al., 2000, FAO, 2003, McLeod et al., 2005, Murawski and Matlock, 2006, Marasco et al., 2007). We have used the definition of McLeod et al. (2005) in this section: 'Ecosystem-based management is an integrated approach to management that considers the entire ecosystem, including humans. The goal of ecosystem-based management is to maintain an ecosystem in a healthy, productive and resilient condition so that it can provide the services humans want and need. Ecosystem-based management differs from current approaches that usually focus on a single species, sector, activity or concern. It considers cumulative impacts of different sectors.' In this century, ecosystem conservation and stable production of food from marine sources are the most important issues for humans in the global earth system, considering increases in the human population and impacts such as global warming. Sustainable conservation management based on the ecosystem approach (SCMEA) for Pacific salmon should be part of the sustainability science of fisheries and oceans. Three aspects of the structure and function of the ocean ecosystem should be monitored, particularly for Pacific salmon: (1) spatial and temporal changes including carrying capacity, food web and trophic level; (2) climatic oceanic conditions including global warming and regime shifts and (3) biological interactions between wild and hatchery populations, density-dependent effects and inter- and intra-specific competition. For the SCMEA of Pacific salmon, adaptive management and precautionary principles are important. In particular, adaptive management should be conducted based on the feedback of monitoring, modelling and adaptive learning, which includes learning by conducting risk analyses and consensus building.
FAO統計によると,2006年の世界水産生産量は110百万トンに及ぶが,漁獲量(53%)は1990年代以降減少傾向を示し,養殖量(47%)が近年著しく増加している。世界の29億人が水産生産物を食糧として利用し,一人当たりの年間消費量は2006年16.7kgに増加し,動物タンパク質消費量の少なくとも15%を占めている。漁獲量の減少は乱獲に負うところが大きく,例えば北大西洋のクロマグロは絶滅危惧種に位置づけられている。一方,生産量が増加の一途をたどる養殖においても,例えばわが国で20万トン以上輸入している養殖エビの生産地では養殖地造成によるマングローブ林生態系の破壊や抗生物質汚染が拡大しており,養殖生産量の増大が海洋を含む地球生態系の驚異となりつつある。一方,わが国のシロザケ資源は長期的な気候変動とリンクして最近増加傾向を示してきた。特に,最近の地球温暖化はシロザケ資源の増加にプラスの役割を果たしてきました。しかし,近い将来,その影響はマイナスに転じることが予想される。ここでは,陸域の食資源が生産飽和状態であることを踏まえて,水産資源がサステナブルな食資源として今後ますます重要性を増しつつあること,人類は不確実性の高いダイナミックな地球生態系と共存しなければ生きて行けないことを認識し,海洋生態系を保全しつつ水産食資源の持続的利用をどのように図っていくかについて,ケース・スタディとしてサケ属魚類を例に紹介する。その上で,われわれが取り組まねばならないアクション・プランとして,伝統的な水産学から生態学的水産海洋学へのパラダイムシフトの必要性と持続的可能な社会をめざす順応的管理と予防原則によるリスク管理について述べる。
記述: Lectures
資料タイプ: conference presentation
URI: http://hdl.handle.net/2115/39914
出現コレクション:国際シンポジウム「明日の海と食を守る水産海洋サステナビリティ学」(International Symposium on Sustainability Science on Seafood and Ocean Ecosystem Conservation)

提供者: 帰山 雅秀

 

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