Distribution and early growth characteristics of anchovy eggs， larvae and juveniles in the central Yellow Sea in summer

Abstract:

Anchovy（Engraulis japonicus）is an important fishing target in the Yellow Sea， and it is also the main prey for large fishes such as Japanese-Spanish mackerel.Exploring the distribution and early growth characteristics of anchovy is important for understanding of the recruitment mechanism.In this study， based on the survey data of the cross-section in the central Yellow Sea in the summer of 2019， the relationship between the distribution of eggs， larvae and juveniles and environmental factors was investigated using Tweedie GAM model. Furthermore， based on the otolith microstructure analysis， the daily age and body length composition of larvae and juveniles were estimated， and the early growth equation of power function was constructed by extrapolating the hatching date.The results showed that in the summer of 2019， a dense distribution area of anchovy eggs occurred in the line section of 35.5°N in the south of Shandong Peninsula， and the dense distribution area of larvae and juveniles occurred in the area of 35.5°N-36.5°N along 123.5°E longitudinal sections.Salinity has a significant effect on the distribution of anchovy eggs， larvae and juveniles， the optimum salinity range was 30-32，on the other hand， the water temperature only has a significant effect on the distribution of anchovy eggs， and the optimum temperature range was 23-26 ℃.Analysis of daily otolith increment for 211 larvae and juveniles showed that the range of body length was 4-24 mm with the dominant length group of 12-14 mm， the age range was 12-40 days with dominant age group of 18-20 days， and the otolith growth rate ranged from 3.08 μm/d to 5.90 μm/d.The variation pattern in the daily otolith growth rate of larvae and juveniles was different between samples in July and August， which might be related to the difference in the water temperature between different months.This study provides scientific basis for the early growth and recruitment mechanism of anchovy resources.