IBER Freshwater Research at the International Congress for Conservation Biology

Siti Rafhiah Hj Abdul Kahar attended the 29th International Congress for Conservation Biology (ICCB) on 21 to 25 July 2019 in Kuala Lumpur. ICCB is organised by the Society for Conservation Biology and is recognized as one of the most important international meeting which a global venue for presenting and discussing new research and developments in conservation science and practice.  Siti Rafhiah presented a talk entitled ‘Mahseer fish (Tor sp.) of Northwest Borneo: A first Look on the Reproductive Ecology’.  The mahseer fishes represent an iconic genus of large-bodied species of the Cyprinidae family that are native to Asia that have been increasingly imperilled through their riverine habitats being impacted by various anthropogenic activities. Unfortunately, conservation efforts have been constrained by knowledge on the genus being heavily skewed towards aquaculture, with considerable knowledge gaps on their taxonomy, autecology, distribution and population status.

This talk was based on a current research on the freshwater fishes in Ulu Temburong National Park of Brunei Darussalam (Northwest Borneo). Tor tambra is highlighted – a mahseer fish species that has a wide distribution across Southeast Asia. In Borneo, this species is highly prized due its lucrative market price. Thus, wild populations are often intensely exploited through small-scale fishing activities. Other than its economic importance, large- sized fishes like Tor contribute significantly to the biomass of freshwater ecosystems through their trophic positioning in the food web as well as impact on nutrient transfers. Like other Tor species T. tambra is known to have potamodromous behaviour with upstream spawning migrations, often over large distances, to facilitate successful reproduction. 

Despite these economic and ecological significance, there is considerable lack of knowledge on T. tambra and hence it is currently classified as ‘data deficient’ in IUCN Red List. The present research aims to examine: 1) the life history traits and trade-offs which contribute reproductive success and, 2) the spawning cycle and type. As this research is ongoing, preliminary observations were highlighted: 1) Approximately 124 specimens sampled monthly from the Ulu Temburong watershed in July 2018 to June 2019, 2) base on macroscopic observation only 9% (or 9 individuals) were found to have sexually mature or maturing gonads with only three of them being female 3) Tor specimens were found to reach sexual maturity at relatively small sizes (female at total length=377mm; male at total length =255mm), 4) mature specimens were only found in February to June 2019 suggesting a protracted spawning season, 5) egg size distribution analysis show a range of egg sizes at different stages of development suggesting that T. tambra is a multiple spawner. One inference from the preliminary results is that T. tambra may have a low population turnover rate as shown by the low number of sexually mature individuals from the samples which could contribute to its vulnerability to overexploitation. Further developments of this research include histological analyses of gonadal tissues to further elucidate reproductive cycles.