USE OF THE DAILY EGG-PRODUCTION METHOD TO ESTIMATE THE STOCK SIZE OF WESTERN-AUSTRALIAN SARDINES (SARDINOPS-SAGAX)

The daily egg production method was used to estimate the spawning biom ass of the sardine Sardinops sagax in the Albany region of Western Aus tralia. Plankton surveys covering 10000-14000 km(2) were completed in July of 1991 and 1992 in three to five days using up to three boats. A dult sardines were obtained from the local purse-seine fleet. The spaw ning area was similar in both years at approximately 3800 km(2) (1100 nmile(2)), but the number of eggs collected was larger in 1991 with eg g production values of 6 . 5 per 0 . 05 m(2) day(-1) compared with 3 . 9 per 0 . 05 m(2) day(-1) in 1992. The average batch fecundity values were similar (approximately 11000 eggs female(-1)) as were the propor tions spawning (0 . 13 in 1991; 0 . 09 in 1992). The calculated biomas s estimates were 23121 t (CV = 0 . 51) and 16121 t (CV = 0 . 44) in 19 91 and 1992 respectively.