Depik (Rasbora tawarensis)

Mohamed bin Zayed Species project number 0905687

The Depik (Rasbora tawarensis) population is decreasing, indicated by decreasing catch-per-unit effort (CPUE), where the average CPUE decreased from 1,166 g/m2 of net in the 1970s to only 15 g/m2 of net in 2009 (refer to Chapter 7). Unfortunately, many basic life history characteristics of the R. tawarensis including distribution pattern and genetic profile have not been documented.

Presently, the fisheries activities in Lake Laut Tawar are unregulated and not well managed, resulting in over exploitation and ecological perturbations. Therefore, a sustainable management of fisheries in general and Depik in particularly is crucially needed to maintain fish production in the future and to ensure this endemic species is sustainable. To achieve these objectives, information on distribution and production trend of the Depik population are needed to plan better management strategies.

Based on our study showed that the Depik, R. tawarensis is widespread in the lake but most abundant in shallow water and near shore, however, the size is small on average for this areas. In contrast, the bigger fish was found in deep water offshore, but with lower abundance. The distribution of Depik was more spatially than seasonally dependent. However, the production (indicated by the CPUE) was seasonally and spatially dependent. The production of Depik in particular and fishes of Lake Laut Tawar in general are declining dramatically during the last two decades. The decrease in the water levels, destructive fishing gears, the presence of introduced species and pollution are the main reasons suggested for this phenomenon.

The study on the DNA profile (DNA barcoding) resulted in a total of 31 haplotype from 112 sequences of 14 freshwater fish species from Lake Laut Tawar.  The study revealed that species status proposed by traditional morphological identification was generally supported by DNA barcoding sequences data. However, further morphological study is needed to evaluate the taxonomic status of several unclarified taxa namely Rasbora sp. (Relo), Homaloptera sp. and Clarias sp. and the relationship between Puntius brevis and Poropuntius tawarensis.