Augmented biomass of recruits of Japanese Spanish mackerel Scomberomorus niphonius by release of hatchery-raised juveniles as estimated from the larval biomass of Japanese anchovy Engraulis japonica

Obata, Y.. Tamano Station; Yamazaki, H.; Takemori, H.; Iwamoto, A.; Hamasaki, K.; Kitada, S.

Augmented biomass of recruits of Japanese Spanish mackerel Scomberomorus niphonius by release of hatchery-raised juveniles as estimated from the larval biomass of Japanese anchovy Engraulis japonica

2008

We estimated the augmented biomass of recruits from released juveniles of the Japanese Spanish mackerel Scomberomorus niphonius in the eastern Seto Inland Sea based on the biomass of the bait, i.e., larvae of Japanese anchovy Engraulis japonica which is the dominant prey of larvae and juveniles of this species. A total of 51,000 juveniles with a mean total length (TL) of 38mm and 82,929 with a mean TL of 114mm were released in 2002; further, 94,000 juveniles with a 36mm TL and 77,193 with a 96mm TL were released in 2003. Before release, all the fish were marked on the otoliths with alizarin complexon. Based on the contribution rates of the released fish in the landings, the relationship between the mean weight of 0-year-old fish in November of 1987-2001, and the stock biomass of the bait per 0-year-old Japanese Spanish mackerel, we estimated the augmentation in biomass over natural production to be 30 and 116 tons in 2002 and 2003, respectively.

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