2:10 PM - 2:25 PM
[ACG38-02] Estimation of the Expansion Process of Plectropomus leopardus Habitats in the East China Sea
Keywords:Plectropomus leopardus eggs and larvae, Two-way Particle Tracking Model experiments, habitat expansion, settling period, East China Sea
Several studies demonstrated the northward expansion of various fish species' habitats due to global warming (e.g., Yamakawa et al., 2020). Regarding the habitat of Plectropomus leopardus in the East China Sea, although Koshikijima island was considered the northern limit of habitat, there are many fishing reports even from Tsushima and Goto Islands at present. In this study, using two-way particle tracking experiments, we attempted to estimate the expansion process of Plectropomus leopardus habitats by investigating the sources of the eggs Tsushima, Goto, and Koshikijima Islands.
The oceanographic dataset used in this study is Data assimilation Research of the East Asian Marine System (DR_M; Hirose et al., 2013). We estimate the sources of Plectropomus leopardus using the DR_M in conjunction with a particle tracking model experiments; we conducted three experiments: two experiments are a drifting period set at 30 days (E30) and 60 days (E60), and the other incorporated the growth process of larvae into the particle tracking model using a length estimation equation based on laboratory experiments (ES60; Okuyama et al., unpublished).
Based on the results of the two-way particle tracking model originate from Tsushima, Goto, and Koshikijima islands, it was found that the southernmost source is the around Kasasa town, Minami-satsuma City (the coasts of China and Taiwan) in experiment E30 (E60). The number of days required for larvae to reach a length of 25 mm (a size considered to settle) was approximately 40-50 days, which is closely consistent with the results of Okuyama et al. On the other hand, when the drifting period was set to 30 days in line wtihe Doherty (1994), the length of the larvae did not exceed 15 mm. Nevertheless, since there may be differences in growth rates between the actual and the rearing environments, it will be necessary caught the naturally settled larvae using light traps, to determine the period until settlement by examining their age and to verify the accuracy of the length estimation formula.
The oceanographic dataset used in this study is Data assimilation Research of the East Asian Marine System (DR_M; Hirose et al., 2013). We estimate the sources of Plectropomus leopardus using the DR_M in conjunction with a particle tracking model experiments; we conducted three experiments: two experiments are a drifting period set at 30 days (E30) and 60 days (E60), and the other incorporated the growth process of larvae into the particle tracking model using a length estimation equation based on laboratory experiments (ES60; Okuyama et al., unpublished).
Based on the results of the two-way particle tracking model originate from Tsushima, Goto, and Koshikijima islands, it was found that the southernmost source is the around Kasasa town, Minami-satsuma City (the coasts of China and Taiwan) in experiment E30 (E60). The number of days required for larvae to reach a length of 25 mm (a size considered to settle) was approximately 40-50 days, which is closely consistent with the results of Okuyama et al. On the other hand, when the drifting period was set to 30 days in line wtihe Doherty (1994), the length of the larvae did not exceed 15 mm. Nevertheless, since there may be differences in growth rates between the actual and the rearing environments, it will be necessary caught the naturally settled larvae using light traps, to determine the period until settlement by examining their age and to verify the accuracy of the length estimation formula.