The Depm Estimation Of Spawning Stock Biomass For Sardine And Anchovy

Author : Nancy C. H. Lo
Publisher :
ISBN 13 :
Total Pages : 38 pages
Book Rating : 4.:/5 (856 download)

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Download or read book Spawning Biomass of Pacific Sardine (Sardinops Sagax) Off U.S. in 2011 written by Nancy C. H. Lo and published by . This book was released on 2011 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: The spawning biomass of the Pacific sardine (Sardinops sagax) in April 2011 was estimated using the daily egg production method (DEPM) calculated by two methods: 1) the traditional method where the egg production (P0) was a weighted mean while each adult parameter was an unstratified estimate, and 2) a stratified procedure where the estimate of total spawning biomass is the sum of the estimated spawning biomass in each of two regions representing high and low spawning activity. The two estimates of the spawning biomass were 383,286 mt (CV = 0.32) and 373,348 mt (CV = 0.28), respectively, for the standard DEPM survey area of 314,480.69 km2 off the west coast of North America from San Diego, California to north of San Francisco, California (CalCOFI line 60.0-95.0). The daily egg production estimate (P0, a weighted average with area as the weight) was 1.16/.05m2 (CV = 0.26). In the standard DEPM area, the estimates of female spawning biomass calculated by the two methods were 225,155 mt (CV = 0.32) and 219,386 mt (CV = 0.28), respectively. A small region close to Astoria, Oregon (47.1° - 45.9°N) was sampled for sardines. No eggs and only 2 immature sardine were collected in this area. Hence, coastwide estimates of sardine spawning biomass and female spawning biomass were not calculated. The estimated daily specific fecundity was 19.04 (number of eggs/population weight (g)/day) using the following estimates of reproductive parameters from 244 mature female Pacific sardines collected from 30 positive trawls: F, mean batch fecundity, 38,369 eggs/batch (CV = 0.07); S, fraction spawning per day, 0.1078 females spawning per day (CV = 0.18); Wf , mean female fish weight, 127.6 g (CV = 0.05); and R, sex ratio of females by weight, 0.587 (CV = 0.06). Since 2005, trawling has been conducted randomly or at CalCOFI stations, which resulted in sampling adult sardines in both high (Region 1) and low (Region 2) sardine eggdensity areas. During the 2011 survey, the number of tows positive for mature female sardines was similar in Regions 1 and 2 (14 and 16 respectively), while four tows in Region 2 contained solely immature sardines. The estimates of spawning biomass of the Pacific sardine off California in 1994 - 2011 based on the traditional method are: 127,000 mt, 80,000 mt, 83,000 mt, 410,000 mt, 314,000 mt, 282,000 mt, 1.06 million mt, 791,000 mt, 206,000 mt, 485,000 mt, 300,000 mt, 600,000 mt, 837,000 mt, 392,000 mt, 117,000 mt, 185,000, 108,000mt and 383,000 mt (for the standard DEPM area), respectively. These estimates of spawning biomass indicate that there has been considerable fluctuation during this time (the peaks occurred in 2000 and 2006) and that biomass has declined in 2008-2010 and increased in 2011. The time series of spawning biomass was one of the fishery-independent inputs to the annual stock assessment of the Pacific sardine from 1985 - 2008. Since 2009, the time series of spawning biomass was replaced by female spawning biomass for years when sufficient trawl samples were available and the total egg production for other years as inputs to the stock assessment of Pacific sardines.