Title Study on the fisheries biology of lizardfishes, Saurida umeyoshii in the East China Sea and Saurida elongata in Tsushima/Korea Strait
Authers Takeshi SAKAI
Keywords lizardfish, Saurida, age, growth, reproduction
Citation Bull. Fish. Res. Agen. No.28, 1-45, 2009
Abstract
The lizardfishes Saurida spp. are commercially important to the Japanese trawlfisheries, and are utilized as surimi or fish cakes “kamaboko”in Japan due to its high meat yield, and high gel forming ability.
 In recent years, stock levels of lizardfish have been low in the East China Sea similar to other demersal fishes. The Japanese large pair trawl fishery catch per unit effort of lizardfish in the East China Sea in 2006 was 9 % of that in 1982, and the landing of lizardfish from Japanese large trawl in the East China Sea decreased from 8585 metric tons in 1982 to 23 metric tons in 2006. Similarly, in the Tsushima/Korea Strait the landing of lizardfish from the Japanese offshore trawl also decreased by about 30 % between 1973 and 2006. Lizardfishes are commercially important to the Japanese trawl fisheries, assessment of lizardfish stocks and establishment of fishery management guidelines are urgently needed. The purpose of the present study is to update information on the biological characteristics, for formulating management proposals on the fishery in the East China Sea and Tsushima/Korea Strait.
1.To reveal the age and growth of the lizardfish, Saurida umeyoshii specimens collected from the East China Sea during the period from April 1998 to April 2000 were studied using polished thin sections of otolith. A total of 1052 individuals, ranging in size between 118 and 454mm fork length, were examined. The frequency of the appearance of the translucent band on the outer margin of the otolith and monthly changes in marginal growth increments indicated that ring marks (outer edge of translucent zone)were formed once a year between December and March. The von Bertalanffy growth curves were expressed as
    Males:FLt = 421.7 [1-exp{-0.162 (t + 1.24 )}], (1 ≦ t ≦ 8)
    Females:FLt = 489.4[1-exp{-0.160 (t + 0.95 )}], (1 ≦ t ≦ 10).
2.Sexual maturity, annual reproductive cycle, and batch fecundity of the lizardfish, Saurida umeyoshii, were examined in specimens collected from the East China Sea between April 1998 and April 2000. The minimum FL at sexual maturity was 180 mm in males and 228 mm in females. Females with mature and spawning stage ovaries were collected between April and December, majorly between June and September when the mean gonadosomatic index was also high. This indicates that the spawning season extends from April and December, mainly from June and September. In the spawning stage ovary, postovulatory follicles continued to degenerate and disappear until the most advanced oocytes attained the migratory nucleus and mature stage, suggesting that this species is a multiple spawner. Time course sampling showed that final oocyte maturation occurred during the daytime and subsequent ovulation occurred in the evening. Batch fecundity (BF)in females with mature oocytes was related to FL (mm):
    BF = 1.70×10-8FL4.88 (278 ≦ FL ≦ 421).
3.To reveal the age and growth of the lizardfish, Saurida elongata, specimens collected from Tsushima/Korea Strait during the period from May 1999 to June 2001 were studied using polished thin sections of otolith. A total of 695 individuals, ranging in size between 189 and 478mmFL, were examined. The frequency of the appearance of the translucent band on the outer margin of the otolith and monthly changes in marginal growth increments indicated that ring marks(outer edge of translucent zone)were formed once a year between November and February. The von Bertalanffy growth curves were expressed as
    Males:FLt = 422.3 [1-exp{-0.202 (t + 1.30 )}],(1 ≦ t ≦ 10)
    Females:FLt = 512.6 [1-exp { -0.157 (t + 1.45 )}], (1 ≦ t ≦ 11).
Our findings indicate that scale method is inadequate for age determination of lizardfish and it is necessary to reexamine the age and growth of Japanese lizardfish studied using scales.
4.Sexual maturity, annual reproductive cycle, and batch fecundity of the lizardfish, Saurida elongata, were examined in specimens collected from the Tsushima/Korea Strait between May 1999 and May 2002. The minimum FL at sexual maturity was 235 mm in males and 249 mm in females, and these were larger than Saurida umeyoshii. Females with spawning stage ovaries were collected between May and August, when the mean gonadosomatic index was also high. This indicates that the spawning season extends from May and August. In the spawning stage ovary, postovulatory follicles continued to degenerate and disappear until the most advanced oocytes attained the migratory nucleus and mature stage, suggesting that this species is a multiple spawner. Batch fecundity (BF)in females with mature oocytes was related to FL (mm):
       BF = 0.00161FL2.98 (261 ≦ FL ≦ 445).
URI http://www.fra.affrc.go.jp/bulletin/bull/bull28/sakai.pdf