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MEPS prepress abstract   -  DOI:

Effects of environmental factors within the spawning area and migration routes on the length of Anguilla japonica glass eels recruited to Taiwan

Kuan-Mei Hsiung, Chi Ma, Chia-Ying Ko, Yu-Heng Tseng, Yi-Chun Kuo, Yu-San Han*

*Corresponding author:

ABSTRACT: Growth extent varies considerably among recruiting cohorts of Japanese eels (Anguilla japonica). However, the effects of oceanic variation on the growth of A. japonica, particularly during the larval stage, remain unclear. We performed glass eel sampling in northeast Taiwan from 2010 to 2019 and investigated the effects of sea surface temperature (SST), salinity, chlorophyll-a (Chl-a) concentration, and El Niño–Southern Oscillation (ENSO) events on the total length (TL) of these eels by developing a generalized additive model (GAM). The results revealed that mean SST between 21°C and 24.5°C in the spawning area was associated with TL. Larger TL values were observed from 0.03 to 0.07 mg/m3 in the spawning area, and these values became greater than 13 mg/m3 along the migration routes. Other variables, including mean SST and salinity along the migration route, influenced TL; however, they contributed less than 4.5%. Larger and smaller A. japonica glass eels were observed during El Niño and La Niña years, respectively. Specifically, El Niño years exerted the greatest influence (67.1%) on TL, and this was followed by mean SST (12%) and accumulated Chl-a concentration (11.4%) within the spawning area. Our results indicated that environmental factors within the spawning area influenced the TL of A. japonica glass eels to a greater extent than did those along the migration routes, and climatic ENSO events exerted an additional important effect in regard to changes in TL. Taken together, our results provide fundamental ecological information and a basis for fisheries to more effectively manage A. japonica.