기후변화에 따른 한국대형선망어업의 생태계 기반 위험도 평가 연구

Abstract

The purpose of this study is to examine how ecosystem-based fishery assessment approach (EBFA) can contribute to the better understanding of climate change impacts on fisheries. Sea surface temperatures showed increasing patterns and accelerated in recent decades in Korean waters. The recent warming trend was associated with replacement patterns, that is, a decline in cold-water species and an increase in warm-water species, as well as with changes in spatial distribution of fish stocks in the Korean marine ecosystem. The Korean large purse seine fishery targets chub mackerel, sardines, jack mackerel, and Spanish mackerel, which are major pelagic fish species in Korean waters. The proportion of chub mackerel which is the main target species, was over 60% in the Korean large purse seine fishery. Surface water temperature increased 0.0188°C per year and the total rising rate was 0.752°C per 40years from 1970 to 2009 in the southern sea of Korea, where is main fishing grounds of the Korean large purse seine fishery. The center of fishing grounds of chub mackerel by the Korean large purse seine fishery has moved to the north at the rate of 4.57km/yr during two decades from 1980s to 2000s. The fishing grounds of Spanish mackerel and bluefin tuna moved northwards about 7.1km/yr and 8.13km/yr, respectively. However, the fishing ground of jack mackerel moved to the south during the two decades. A pragmatic ecosystem-based approach, the Integrated Fisheries Risk Analysis Method for Ecosystems (IFRAME), has been developed with an aim to assess and forecast impacts of climate changes and fishing activities on fish and fisheries of an ecosystem. Using the IFRAME, we constructed the ecosystem structure of the habitat of chub mackerel which includes the fishing area of the Korean large purse seine fishery for 2009, and forecasted the structure for 2059 under climate changes. We analyzed ecological risks by the fishing intensity, based on warming scenarios in 2059. We adopted climate change scenario of IPCC SRES A1B by GFDL-CM2.0 and MIROC3.2 (Hires) models, and to examine the impacts by fishing mortality (F-value) scenarios in IFRAME. The range of F-value was from zero to double FABC, which is the current F-value. We considered some impact factors on the fish biomass under the climate change as the first step in assessing the effects of climate change on major commercial species of the fishery. We assumed that the fluctuation factors of fish biomass were (1) variations in habitat areas of target species, (2) habitat overlapping ratios between target species and bycatch species, (3) recomposition of demersal ecosystems interacting with pelagic ecosystems, because of the movement of pelagic fish, (4) variations in vertical distribution due to the increased water temperature in water column, (5) changes in lower trophic biomass and production, and (6) biogeochemical effect, such as, ocean acidification, decreases in dissolved oxygen, etc. We forecasted exploitable biomass of chub mackerel from 2010 to 2099 in the fishing ground of the Korean Exclusive Economic Zone (EEZ). The exploitable biomass was forecasted by two different air-ocean models, which were GFDL-CM2.0 and MIROC3.2 (Hires). Results of this forecasts can be used in the a management-strategy evaluation framework of IFRAME to assess alternative harvest strategy and/or tactics in the rapidly changing marine ecosystem.