Changes in community structure of finfish catches in Brunei Darussalam between 2000 and 2009

• Published in: Ocean & coastal management 2013-05, Vol.76, p.45-51
• Main Authors: Ebil, Syazana, Sheppard, Charles R.C., Wahab, Ranimah, Price, Andrew R.G., Bull, James C.
• Format: Article
• Language: English
• Subjects: community structure; Earth sciences; Earth, ocean, space; Exact sciences and technology; fish; fish communities; food webs; Geomorphology, landform evolution; invertebrates; Marine and continental quaternary; marine ecosystems; overfishing; statistics; Surficial geology
• ISSN: 0964-5691; 1873-524X
• DOI: 10.1016/j.ocecoaman.2013.02.021

Commercial fishery catches in Brunei Darussalam between 2000 and 2009 were used to examine changes in community structure of Brunei's marine ecosystem – a relatively lightly harvested system within a region chronically overexploited by fisheries. We found that Mean Trophic Level (MTL) has declined at a rate of 0.08 trophic levels (TL) per decade, suggesting a ‘fishing down the marine food web’ process in Brunei waters. In order to focus on changes in relative abundance of the more threatened, higher TL finfish only, MTL was recalculated as 3.30MTL (to exclude catches of finfish and invertebrates species with TL less than 3.30). Here, we found no overall trend in the 3.30MTL over the study period. However, a more in-depth analysis suggested that MTL fails to capture substantial changes in underlying species assemblage. Over the course of the study period, marked changes in fish community structure were observed. Analysis of official statistics showed an increase in total catch was driven primarily by an increase in pelagic catches, with a similar trend observed when the catches were aggregated into either high- or low-TL. This pattern is consistent with the increasing Fishing-in-Balance (FiB) index for the Brunei region. Whilst our study was not aimed at demonstrating overfishing as the cause of observed trends, there is a danger that current best practice fails to detect what may be an imminent fishery collapse. In many fisheries around the world, there is a need for detection methods able to identify potential problems within a time scale short enough to be able to react effectively. ► Catch sustainability was assessed using Brunei fisheries records from 2000 to 2009. ► Standard metrics, MTL and FiB, showed no clear signal of unsustainability. ► Closer inspection of ecosystem architecture indicated substantial changes. ► Brunei fisheries became increasingly unsustainable towards end of last decade. ► Trophic level metrics may fail to capture early warnings signs of stock collapse.