Using genomic sequencing, I investigated the evolutionary history of marine fishes in the group Carangoidea, which includes ~170 species known as kingfish, jacks, trevallies and pompanos, as well as the remoras, dolphinfishes (mahi-mahi), and the cobia. With DNA sequences, I am able to estimate how long ago these species evolved, whether there have been time periods of increased rates of speciation, and how each species in the group is related to one another.
In addition to studying the evolution of the whole group, I am conducting a population genomics study on both the Giant Trevally (Caranx ignobilis) and Bluefin Trevally (Caranx melampygus). Giant trevallies can weigh up to 80 kg (176 lbs) and, along with bluefins, are found throughout the Indo-Pacific. I’m researching how genetically diverse these species are across their range by sampling vast amounts of their genome (a method called next-generation sequencing). I’m sampling fish from locations including South Africa, Mozambique, Seychelles, Hawaii, Australia, Mauritius, and Saudi Arabia, looking at connectivity and genetic diversity at multiple spatial scales. This can be used to determine if these fish show any geographic structure to designate specific “stocks,” which can be used for conservation and management decisions.
This work is complementary to ongoing tagging studies by Dr. Paul Cowley at SAIAB, who is tracking the movement of giant trevallies. Two questions I will be asking are, “Do the movement patterns of these fishes reflect their genetic diversity?” and “How much genetic exchange is occurring across their range?”
Here is a short video produced in 2016 that gives a glimpse into the challenges of catching Giant Trevally samples in the Seychelles!