This study examined interindividual personality differences between Port Jackson sharks Heterodontus portusjacksoni utilizing a standard boldness assay. Additionally, the correlation between differences in individual boldness and stress reactivity was examined, exploring indications of individual coping styles. Heterodontus portusjacksoni demonstrated highly repeatable individual differences in boldness and stress reactivity. Individual boldness scores were highly repeatable across four trials such that individuals that were the fastest to emerge in the first trial were also the fastest to emerge in subsequent trials. Additionally, individuals that were the most reactive to a handling stressor in the first trial were also the most reactive in a second trial. The strong link between boldness and stress response commonly found in teleosts was also evident in this study, providing evidence of proactive-reactive coping styles in H. portusjacksoni. These results demonstrate the presence of individual personality differences in sharks for the first time. Understanding how personality influences variation in elasmobranch behaviour such as prey choice, habitat use and activity levels is critical to better managing these top predators which play important ecological roles in marine ecosystems.
Milkfish (Chanos chanos)
Sungei Buloh Wetland Reserve, 2nd February 2016
This photo of the carcass of a Milkfish was shared by Yap Xinli. I also came across it later that same day and took some photos of my own.
The location of this dead fish, on one of the wooden bridges within Sungei Buloh Wetland Reserve, suggests that it had been picked up and then dropped by another animal, possibly a Bird of Prey or a Feral Dog (Canis lupus familiaris).
Given that Milkfish are raised in some of the fish farms in the waters of the western Straits of Johor, it is difficult to determine whether the Milkfishes found in these waters are of captive or wild origin.