Spawning Biomass of Sardine (Sardinops sagax) in South Australia in 2006

1. This report provides estimates of the spawning biomass of Australian sardine (pilchard, Sardinops sagax) in gulf and shelf waters of South Australia during 2006. 
2. Estimates of spawning biomass were obtained from data collected from surveys conducted on RV Ngerin in February and March 2006. The total survey area was ~114,490 km2. 
3. Sea surface temperatures ranged from 15.4 to 21.9 °C and were lowest off Coffin Bay Peninsula, which reflects strong upwelling during the surveys. 
4. Estimates of adult reproductive parameters (95% CI) were: mean female weight, W = 57.2 g (50.86-65.16); mean sex ratio, R = 0.64 (0.55–0.77); mean spawning fraction, S = 0.13 (0.09–0.16) and mean batch fecundity, F = 14,290 (11,013–17,580) hydrated oocytes. 
5. A total of 3,083 eggs were collected from 341 stations. High densities (254–5,126 eggs.m-2) were recorded in southern Spencer Gulf, Investigator Strait, and west of Anxious Bay. Few eggs were found south of the Eyre Peninsula between Cape Catastrophe and Cape Finnis, 
and there were distinct eastern and western spawning areas. 
6. The total spawning area of 44,891 km2 was the highest recorded and was comprised of an eastern spawning area of 10,936 km2 and a western spawning area of 33,954 km2. 
7. The proportion of eggs collected from the region east of Coffin Bay declined between 2004 and 2005 and increased slightly in 2006. 
8. Daily egg production, P (95% CI), for the entire spawning area was 104.7 eggs.day-1. m-2  (67.95–158.44). 
9. The estimate of spawning biomass (95% CI) for the entire spawning area was 226,088 t (136,060–417,612). Estimates of spawning biomass for the eastern and western spawning 
areas were 55,079 t (25,406–134,141) and 171,009 t (86,360–299,656), respectively. 
10. The large proportion of the spawning biomass located in the western spawning area highlights the large disparity between the historical distribution of fishing effort and the 
distribution of the spawning stock in 2006.