Apparently many of the Hong Kong groupers landed in Hong Kong in the past were caught from islands off the mainland coast to the north of Hong Kong were they were once common but are evidently no longer common (Patrick Chan, pers. comm. 2001).

Declines in landings are assumed to reflect declines in Hong Kong grouper stocks unless it is known that fishing effort has decreased or other factors are involved. The mean percentage decline of Hong Kong grouper (excluding Hong Kong and Taiwan which appear to have negligible populations of Hong Kong grouper) from China (90%), Japan (50%) and Republic of Korea (50%) is 63 %.

Ideally, the percentage decline would be applied to estimates of the original Hong Kong grouper population within each country for which the decline applies. This would be done for all countries and the overall decline would be the percentage difference between the original global population size and the current one. Unfortunately, estimates of country stock size are non-existent for this species. The declines were therefore weighted by rocky reef area (rather than by population size) to give an overall decline figure. This method assumes that pristine densities of Hong Kong grouper were the same at all localities. This is probably not likely to have been the case but it enables a single figure to be derived which is likely more representative of the global situation than the alternative, which is just to say the decline lies between 50 and 90% (the lowest and highest decline rates).

It is worth noting that simply taking the mean of all decline figures gave a very similar figure, 63% rather than 65%.

Decreasing