Complex effects of temperature and copepod abundanceon early life growth of subtropical fishes:based on cutlassfish Trichiurus japonicus

• Main Authors: Yun-Kae Kiang, 江勻楷
• Other Authors: 王慧瑜
• Format: Others
• Language: en_US
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/cp6k66

碩士 === 國立臺灣大學 === 海洋研究所 === 104 === Early life growth rates provide insight on larval survival and determine future population dynamics. Such knowledge for subtropical fishes, however, is understudied. Subtropical fishes often display prolonged spawning seasons, thus, their larvae may experience differential growing conditions (e.g., temperatures and food availability). To advance current knowledge on early life growth rates for subtropical fishes, we carried out a study based on an important fisheries species, the cutlassfish Trichiurus japonicus, which spawn all year round throughout the coastal water of Taiwan (around 21.8 – 25.4⁰N, 119.2 – 122.1⁰ E). The coastal environments of Taiwan are influenced by differential monsoons and currents, interacting to form variable patterns in temperatures and productivity. We hypothesized that such variable temperature and food abundance could lead to variation in early life growth rates for cutlassfish. We compared growth of larval and early juvenile cutlassfish, copepod abundance (i.e., an index of food availability), and temperature data among the three coasts: NW, NE, and SW coasts, 2000-2015. Copepod abundance was positively correlated with temperature at the NW but not NE or SW coasts (r = 0.44, 0.15, and -0.25, at NW, NE, and SW respectively). Similarly, daily growth rates of cutlassfish (at age = 2-60 days) were positively correlated with temperatures at the NW but not NE or SW coasts. To elucidate the effects of temperature and copepod abundance on fish growth, we constructed a bioenergetics model and compared simulations with the temperature and copepod abundance among three coasts in present-day vs. global warming scenarios. Simulation outputs reflected differential temperature effects on cutlassfish early life growth rates, with similar pattern as our empirical data, but the magnitudes did not match the mean growth rates among coasts. The impacts of climate change on growth also varied among coasts: simulated growth increase at the NW but decrease at NE and SW coasts. Integrating field data and bioenergetics modeling, our study demonstrates diverse environmental effects on early life growth for cutlassfish in subtropical ocean within small spatial scale. Our study provides implications for population dynamics under climate change, which induces anomaly in temperature and food availability, influencing growth and recruitment of fish. Such effects should be considered for fishery management of subtropical marine fishes.