Comparison of fluctuations in fish communities and trophic structures of ecosystems from three currents around Japan: synchronies and differences

Abstract

Tian, Y., Uchikawa, K., Ueda, Y., and Cheng, J. Comparison of fluctuations in fish communities and trophic structures of ecosystems from three currents around Japan: synchronies and differences. – ICES Journal of Marine Science, 71: . Features of three marine ecosystems affected by the Tsushima (TWC), Kuroshio (KC), and Oyashio (OC) currents were analysed based on fishery, oceanographic, and climate datasets during 1955–2010. Principal component (PC) analysis for catches of 25 indicator species showed evident decadal variation patterns with a step change in the first principal component (PC1) in the late 1980s, indicating synchronies in the dominant variation mode across the ecosystems. Step changes were also detected in the mid-1970s in PC2 and PC3 in OC, and around 1970 in PCs in KC and TWC. These indicate that the most marked change across the ecosystems occurred in the late 1980s, corresponding to the late 1980s climate regime shift, but OC also responded strongly to the mid-1970s regime shift, indicating different responses to regime shifts. The generalized additive model showed the PCs associated largely with water temperature in each region as well as climate indices, indicating the importance of regional oceanographic conditions. Ecosystem indicators such as the mean trophic level showed similarities between TWC and KC but differences with OC, indicating that trophic structures in TWC and KC were largely dependent on the mid-trophic (small pelagic species) level, while on demersal species in OC.

Climate Variability Patterns and Their Ecological Effects on Ecosystems in the Northwestern North Pacific

“…All these large-scale climatic indices (short as CIs) are derived from open-access online databases and have a monthly temporal scale for the period 1963-2016. These CIs are well documented and largely associated with variations in the fish communities and ecosystems in the North Pacific (Tian et al, 2014;Liu et al, 2019;Ma et al, 2019).…”

“…Based on the availability of qualified long-term time-series, we compiled fishery catch data of various taxa (with raw catch data shown in Supplementary Figure S1) from four countries/regions (i.e., China, Chinese Taipei, Japan, and Korea) for the period of 1963-2016 (the longest time period considering both data availability and comprehensiveness). Although the taxa from different countries/regions may differ, they generally fall into three major categories, large predatory, demersal, and small pelagic (Supplementary Table S1), such that they well represent the ecosystem structures (Tian et al, 2014). Within each country/region, taxa that account for a small amount of catch (<1% of total catch) are excluded to avoid the effects of potential recording errors.…”

“…Therefore, these climate variability patterns may contribute less to ecosystem variability in the northwestern North Pacific. Aside from the patterns in the PDO, NPGO, and ENSO (SOI), studies in the northwestern North Pacific always consider the Arctic Oscillation Index (AOI), East Asian Monsoon Index (MOI), and Siberian High Index (SHI, variations in Siberian High pressure system) in order to explore more potential links between climate variability patterns and regional environment and ecosystem variability (Tian et al, 2014;Jung et al, 2017;Liu et al, 2019;Ma et al, 2019). However, the ecological importance of these climate variability patterns has not been evaluated, which may hamper predictions of climateinduced ecosystem variability in the northwestern North Pacific.…”

Long‐term changes in recruitment of age‐0 Pacific bluefin tuna (Thunnus orientalis) and environmental conditions around Japan

“…h defines the range of departure from the observed mean beyond which observations are considered outliers. In the present study, h was set equal to 1 based on a similar study around Japan (Tian, Uchikawa, Ueda, & Cheng, ). The duration of l was set at 5, 10 and 15 years, and the significance level ( p ) varied from 0.1 to 0.5.…”

Association between the interannual variation in the oceanic environment and catch rates of bigeye tuna (Thunnus obesus) in the Atlantic Ocean

“…Pelagic tuna species likely track suitable habitats for feeding and spawning migrations. Climatic oscillations, anomalies, and changes clearly affect numerous ecological processes in marine ecosystems, influencing the population abundance and distribution of many species (Lan, Lee, Wang, & Chen, ; Stenseth, Ottersen, Hurrel, & Belgrano, ; Tian, Uchikawa, Ueda, & Cheng, ). The biophysical effects of large‐scale environmental and climatic variability play a critical role in controlling tuna distribution and abundance (Goñi et al., ; Lan, Evans, & Lee, ; Lan et al., ; Lehodey et al., ).…”