Abstract:

To clarify variation of Coilia nasus biomass and explore the conservational effects of the coastal waters on anchovy resources, investigations were carried out along the Jingjiang section of the Yangtze River 2 or 3 times per month from 2002 to 2013 using a stow net． The results showed that occurrence rate of C.nasus was 946% in 369 samples, accounting for 518 % (individual) and 546% (weight) of the total catch yield, respectively. The average abundance and biomass (CPUEN and CPUEW) of C.nasus was 167 ±199 ind. and 1066±1095 g. Being a dominant or subdominant species of the fish assemblage in 12 years, C.nasus was not stable in resource. The highest biomass in 2010 was 54 times higher than the lowest in 2002. The average body weight and body length was 75 g and 1236 mm, respectively. 1 315 specimens were determined as three age compositions: 789% of specimens as 0+ year age group, 207% as 1+ year age group and 05% as 2+ year age group. 2+ year age group only appeared in April and May, and accounted for 30% of the total individual. Thus, the larvae were major components of C.nasus population along the coast water. According to monthly length distribution of 0+ age group individual, larvae and juveniles began to appear in the coastal zone after hatching, coastal habitats supposedly play an important role in maintaining anchovy recruitment stock. Although the closed fishing season in the Yangtze River during April 1st to June 30th could protect the total 426% larvae and juveniles, properly longer fishing ban period in coastal region might acquire better protective effect. Maintaining habitat integrity of coastal waters is also an important measure to protect the resources of C.nasus larvae.