Changes in Patterns of Seasonality Shown by Migratory Fish Under Global Warming: Evidence from Catch Data of Taiwan’S Coastal Fisheries
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sustainability Article Changes in Patterns of Seasonality Shown by Migratory Fish under Global Warming: Evidence from Catch Data of Taiwan’s Coastal Fisheries Ching-Hsien Ho 1,2,*, Hsueh-Jung Lu 1,3, Jia-Sin He 4, Kuo-Wei Lan 1 and Jyun-Long Chen 5 1 Department of Environmental Biology and Fisheries Science, National Taiwan Ocean University, 2 Pei-Ning Road, Keelung 20224, Taiwan; [email protected] (H.-J.L.); [email protected] (K.-W.L.) 2 Department of Global Agricultural Sciences, Tokyo University, 7-3-1 Yayoi, Bunkyo, Tokyo 113-8657, Japan 3 Center of Excellence for the Oceans, National Taiwan Ocean University, 2 Pei-Ning Road, Keelung 20224, Taiwan 4 Coastal and Offshore Resources Research Center, Fisheries Research Institute, Council of Agriculture, No. 6, Yugang N. 3rd Rd., Cianjhen District, Kaohsiung 80672, Taiwan; [email protected] 5 Marine Fisheries Division, Fisheries Research Institute, Council of Agriculture, No.199, He 1st Rd, Keelung 20246, Taiwan; [email protected] * Correspondence: [email protected]; Tel.: +886-224-622-192 (ext. 5033); Fax: +886-224-632-659 Academic Editor: Vincenzo Torretta Received: 7 January 2016; Accepted: 10 March 2016; Published: 16 March 2016 Abstract: In this study, we analyzed the fish species composition data of coastal capture fisheries in Taiwan between 1963 and 2010. The purpose of the analysis was to understand the long-term changes in marine ecosystems. A ratio-to-moving average method was used in conjunction with adjusted seasonal indices to determine the seasonality of individual catch items and to examine the trends shown by the species with the same seasonality. Over the 48-year timespan of the data, 31 species, i.e., 64% of the total number of species, were identified as seasonal migrants. The catch ratio for species showing a single peak in the spring increased steadily over time; however, those species with a single peak in the winter decreased. The catch ratio for those species with dual peaks in both summer and fall varied greatly before 1978. Increasing trends began in the 1980s and accelerated until 1998. As a result of this increase, the previous concentration of the fishing season in the winter months became highly diffuse. Additionally, the winter and/or spring species continued to decrease year after year as the summer and/or autumn species gradually came to dominate the catch. This change in fishing seasonality is likely not an anthropogenic effect. However, the change coincides with trends in sea surface temperature fluctuations. Such variation may not only cause structural change in marine ecosystems but can also significantly impact the economy and the livelihoods of those associated with the fishing trade. Keywords: China Coastal Current (CCC); Kuroshio Current (KC); seasonality; sea surface temperature (sst); species composition; time series analysis 1. Introduction The increasing number of publications assessing the impact of climate change on marine ecosystems and fisheries attests to rising scientific and public interest [1]. A selection of recent papers, addressing biological rather than social and economic aspects, is reviewed here, with particular attention given to the climate impact on future fishery yields [1,2]. Climate change has significant effects on marine organisms. It is predicted that by 2050, serious species invasions, local extinctions, and species turnover will have occurred globally; more species will move to higher latitudes [3]. Globally and under the high-range greenhouse gas emission scenario, the 10-year average maximum Sustainability 2016, 8, 273; doi:10.3390/su8030273 www.mdpi.com/journal/sustainability Sustainability 2016, 8, 273 2 of 13 Sustainability 2016, 8, 273 2 of 13 catch potential will be reduced up to 20% from 2005 to 2055 between 1010°˝ N and 10° 10˝ S. In In the the Northern Northern Hemisphere, thethe catchcatch potential potential will will decline decline moderately moderately in in temperate temperate regions regions (approximately (approximately 25–50 25–50°˝ N) N)but but increase increase in in higher-latitude higher‐latitude regions, regions, particularly particularly in in the the subarctic subarctic region region [ 3[3,4].,4]. InIn thethe Southern Hemisphere, species movement patterns are less clear in the non non-tropical‐tropical regions, except for the large large variations in the maximum catch potential (±30% (˘30% from from 2005 2005 level) level) around around the the Antarctic Antarctic region region [4]. [4]. Therefore, future changes in the position of fish fish stocks will significantly significantly affect fisheries fisheries at both the regional andand national national levels, levels, especially especially in low-latitudein low‐latitude waters, waters, short-coastline short‐coastline coastal coastal states, states, and island and islandcountries. countries. If these If simulations these simulations prove true,prove local true, fishery local fishery resources resources will change will change significantly significantly as global as globalwarming warming progresses. progresses. Taiwan is located near the fastest warming marine marine waters, waters, which which can can be be deemed deemed the the “hotspots” “hotspots” of the world [5]; [5]; therefore, therefore, environmental variation caused by climate climate change change severely severely affects affects fishery fishery resources. In the coastal waters of Taiwan, the the northward northward flow flow of of the the Kuroshio Kuroshio Current Current (KC) (KC) provides provides a acontinuous, continuous, year-round year‐round addition addition to theto the abundant abundant fish fish resources resources of Taiwan, of Taiwan, influencing influencing the year-round the year‐ roundoceanic oceanic regime regime [6]. During [6]. During the winter the winter north-easterly north‐easterly monsoon monsoon period period (September (September to April), to April), the China the ChinaCoastal Coastal Current Current (CCC) (CCC) brings brings cold water cold fromwater the from Yellow the Yellow Sea and Sea the and East the China East Sea China into Sea the into Taiwan the TaiwanStrait (TS) Strait [7–9 ].(TS) Water [7–9]. circulation Water circulation in the TS varies in the seasonally TS varies due seasonally to changes due in to wind changes direction in wind [7–9]. directionFurthermore, [7–9]. the Furthermore, CCC and KC the are CCC tied and closely KC toare sea tied surface closely temperature to sea surface (SST) temperature variations in(SST) the variationscoastal waters in the of Taiwancoastal waters (Figure 1of)[ Taiwan6]. In recent (Figure years, 1) [6]. the In rate recent of SST years, increase the rate in Taiwan’s of SST increase waters has in Taiwan’saccelerated, waters and thehas variability accelerated, has and increased the variability [10]. The has increase increased in SST [10]. has The been increase accompanied in SST byhas a been shift accompaniedin ocean currents. by a However,shift in ocean the mechanismscurrents. However, behind the these mechanisms changes are behind the decline these changes of the CCC are andthe declinethe enhancement of the CCC of theand KC the [6 ,enhancement11–13]. The ocean of the environment KC [6,11–13]. changes The contributeocean environment to modifications changes in contributethe productivity, to modifications distribution, in and the phenology productivity, of marine distribution, species, and affecting phenology ecosystem of marine processes species, and affectingaltering food ecosystem webs [ 5processes,6,14–16]. and altering food webs [5,6,14–16]. Figure 1. The grids selected for observing the long‐term changes of SST from 1963 to 2010: NE, NW, Figure 1. The grids selected for observing the long-term changes of SST from 1963 to 2010: NE, NW, SE SE and SW. (NE: North East, Grids: C1, C2, D1, D2; NW: North West, Grids: A1, A2, B1, B2; SE: South and SW. (NE: North East, Grids: C1, C2, D1, D2; NW: North West, Grids: A1, A2, B1, B2; SE: South East, Grids: C3, C4, D3, D4; SW: South West, Grids: A3, A4, B3, B4). The global ocean temperature has increased at a rate of approximately 0.11 °C every 10 years ˝ from The1982 global to 2001 ocean [17]. temperatureIn Taiwan, the has water increased SST increases at a rate over of approximately this period have 0.11 beenC approximately every 10 years 0.5from °C 1982 per todecade, 2001 [ 17a value]. In Taiwan, much higher the water than SST the increases global average. over this In period recent haveyears, been the approximatelywarmer water ˝ temperature0.5 C per decade, has caused a value seasonal much higher variation than in the the global marine average. species In located recent years,off the the coast warmer of Taiwan water [6,18,19].temperature The has SST caused in Taiwanese seasonal variationwaters has in been the marine rising species since the located 1980s, off leading the coast to of frequent Taiwan [extreme6,18,19]. weatherThe SST and in Taiwanese climatic changes. waters These has been warmer rising temperatures since the 1980s, are putting leading the to coastal frequent fisheries extreme of weather Taiwan inand a disadvantageous climatic changes. position These warmer [6,10,20]. temperatures Previous research are putting on this the topic coastal has focused fisheries on of single Taiwan species in a in specific local areas. Rare, comprehensive, multi‐species, and island‐wide surveys were conducted. However, it is difficult to conduct a long‐term, fishery‐independent survey covering multiple species Sustainability 2016, 8, 273 3 of 13 disadvantageous position [6,10,20]. Previous research on this topic has focused on single species in specific local areas. Rare, comprehensive, multi-species, and island-wide surveys were conducted. However, it is difficult to conduct a long-term, fishery-independent survey covering multiple species in the waters surrounding Taiwan. From 1963 to 2010, the fishing capacity of Taiwan rapidly increased. Excessive fishing capacity may result in mixed impacts, and it is difficult to observe the extent of the impact of climate variability. However, the fishing efforts of Taiwanese coastal fisheries are relatively stable compared to other fisheries.