Science Saves Sharks

Genomics Tools for Conservation Of Southern Africa's Sharks and Rays.
T ext by E X T B Y Jessica Winn, Mia Groeneveld & Karla Redelinghuys

Sharks, rays, and skates (elasmobranchs) have persisted through several mass extinction events to claim their position as one of the oldest living lineages on Earth, with an evolutionary history spanning 450 million years. This predates the dinosaurs by 200 million years!

The current Anthropocene era, marked by unprecedented human-mediated environmental change, has led to a staggering 70% decline in the global abundance of elasmobranchs in just the past 50 years. This rapid decline has pushed sharks and rays into the category of the most imperilled animals, with over a third of species facing extinction due to a variety of threats. The urgency of this situation cannot be overstated.
 
Biomass depletions from large-scale fishing efforts, habitat destruction, and climate change are reshaping the ecosystems that these species inhabit. Elasmobranchs hold important roles in community functioning as apex- and meso-predators, and their eradication has the potential to catalyse trophic cascades in ecosystems. This not only negatively impacts the species relying on those ecosystems but also threatens to deplete resources that humans depend on and ultimately impacts the health of our bio-economy.

All  sharks and rays interacting in an ecosystem contribute to its stability. However, a few charismatic species tend to dominate the public realm. South Africa’s waters host an abundance of biodiversity, with 191 Chondrichthyan (cartilaginous fish) species, 70 of which are endemic - meaning they are found nowhere else in the world. Species such as the Flapnose Houndshark and Ornate Sleeper Ray occur along only a few hundred kilometres of coastline. The mportant question is how do we go about protecting this biodiversity? 

Our research group in the Genetics Department at Stellenbosch University is dedicated to using molecular tools to study the evolutionary relationships, population dynamics, genetic diversity, and adaptive potential of shark and ray species, particularly those that are threatened or endemic. We believe that genetic diversity is the key to survival, and understanding how to preserve it is crucial. We also believe that each one of us, including you, can play a role in creating species management strategies that lead to the revival of threatened populations while still ensuring a sustainable form of income for local fishing communities.

Phylogenetics and phylogeography enable us to decipher the evolutionary relationships and historical distribution patterns of different shark and ray species to design unique management strategies. In the shark and ray world, species often look very similar but cannot breed and exchange genetic material. Assessing a group of species as a single unit can compromise estimates of their true population size and conservation requirements. The same can be true for populations belonging to a single species that are reproductively isolated from each other by geographical barriers.

Genetics can also be an asset in forensic investigations, which aim to identify the species and origin of confiscated shark products to combat illegal trade. Additionally, uncovering patterns of genetic evolution allows us to pinpoint adaptations to specific environmental conditions, paving the way for informed conservation strategies that can prevent further declines of species faced with environmental challenges. When combined with data from marine scientists and other experts, genetic insights guide the prioritisation of protection efforts.

For example, measures such as catch limits and Marine Protected Areas are being developed, which enhance species recovery and preserve biodiversity in vital coastal breeding regions.

The field of shark and ray conservation in South Africa has grown exponentially, with many different organisations, research groups, officials, and public stakeholders dedicated to protecting our species. Although there is still a long way to go, we must acknowledge the great strides that have been made so far. Many stakeholders attended the 7th South African Shark and Ray Symposium in Umhlanga, Kwa-Zulu Natal, highlighting the growing collaborative network emerging between seasoned experts and the next generation of scientists.

Equally noteworthy is the increasing presence of women making significant contributions in this field, marking a commendable milestone. However, the potential of genetics as a powerful tool for conservation in this domain is still sometimes underestimated due to the science not being well understood. In an attempt to navigate this, “Science Saves Sharks” was cofounded by three postgraduate students: Jessica Winn, Mia Groeneveld and Karla Redelinghuys. Through our organisation, we aim to achieve four main goals, which are all interconnected.

We strive to raise awareness about the threats facing sharks and rays. We are focused on demonstrating how genetic approaches can be applied in synergy with other marine sciences to add real value to conservation efforts. We also aim to make scientific findings more accessible and highlight the incredible work that scientists are doing to a broader public network. We hope to create a community that unites different ocean stakeholders for the common cause of ensuring healthy oceans for our future.

Science Saves Sharks Links
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