Ghost sharks: chimaeras, the sharks’ forgotten cousins
SHOW NOTES
It’s spooky season! And we thought that was an excellent opportunity to devote an episode to some close relatives of sharks and rays: the chimaeras. Also known as ghost sharks and spookfish, these mysterious deep-sea dwellers have a cartilaginous skeleton, which makes them part of the chondrichthyans – the group of fishes that also includes the sharks, rays and skates. Despite the fact that they have been around for hundreds of millions of years, we know relatively little about them. In fact, if you think sharks aren’t talked about enough, then chimaeras get even less of the spotlight! Here to tell us more about them is Dr Luz Erandi Saldaña Ruiz, SOSF project leader and postdoctoral research fellow at the Ensenada Center for Scientific Research and Higher Education (CICESE) in Mexico. Luz uses a combination of methods and technologies to fill knowledge gaps for data-poor and data-limited fisheries, building an understanding of what is being caught and landed to inform better management for rare and threatened species of cartilaginous fishes. This work has brought Luz closer to chimaeras, who are caught regularly in the areas in which she works. In this episode, Luz explains more about her research, and introduces us to the enigmatic cousins of sharks and rays.
We begin as always by getting to know Luz, beginning with her most memorable ocean experience [7.20]. She remembers her first time scuba diving, which evoked feelings of both fear and curiosity. Luz experienced thalassophobia – the fear of deep water – and found the prospect of swimming with nothing beneath her quite daunting. But she soon became mesmerised by the vibrancy of the underwater world and its colours, movements and diversity of life. Her fear soon melted away, to be replaced by a love and awe of the ocean and its inhabitants.
However, this curiosity began long before her first dive [9.00]. Growing up, Luz read as many books as she could on marine life, enraptured by the illustrations of strange and brilliant creatures. In particular, she recalls being fascinated by the narwhal, an animal that looked so bizarre that Luz couldn’t believe it was real. Later on, when she discovered narwhals were not mythical creatures, Luz was determined to know more – if narwhals were real, what other weird and wonderful species could be found beneath the waves? This line of enquiry led her to the sharks, rays and skates, who Luz found utterly fascinating. And that fascination was cemented when Luz was introduced to the movie Jaws – something we see a lot on this podcast!
Luz’s passion for sharks took her to university, where she later studied for a PhD investigating shark fisheries off the coast of Mexico [12.10]. Such fisheries are very important for coastal communities, providing both subsistence and income. But there is a lack of fisheries data for the region, meaning more research is needed to manage and conserve the chondrichthyan species that are caught – especially as many of them are thought to be endangered. Luz’s research aims to gather vital data to inform fisheries management, which involves working closely with the fishers themselves. For her SOSF project, Luz surveyed Popotla, a fishing camp located on the Baja California peninsula just 28km from the U.S-Mexico border [15.30]. Luz sought to describe what species were being caught, the different gears being used, and where fishing activities were concentrated. And some of the most common fishes caught were chimaeras.
Luz describes chimaeras as the “sharks’ forgotten cousins” [17.30]. Like sharks and rays, chimaeras have a skeleton made of cartilage, and are close relatives. However, they receive much less media coverage. Luz believes this is partly because of where they live. Chimaeras mostly inhabit waters of 100-3,000m deep, making them quite difficult to observe and study. But this doesn’t mean they don’t deserve the spotlight. They are nicknamed ghost sharks and spookfish because of the spectral appearance of some species, which Luz likens to Zero, the pet dog of Jack Skeleton in the Tim Burton animated movie and cult classic Nightmare Before Christmas. Much like the infamous character, chimaeras glide through the dark in a ghostly manner, and have large eyes that reflect what little light makes its way to the deep. But that’s not the only nickname given to chimaeras! They are also known as rabbitfish, due to their prominent snout and large eyes, and ratfish, because of their long, whip-like tail [21.05]. There may be as many as 40-50 species of chimaera that exist today, but the exact number is hard to know – as Luz points out, we are still discovering new species of cartilaginous fish as technology and science advances, especially those that exist in the deep sea [22.30].
Given the depth that chimaeras tend to hang out at, very little is known about their biology and life history [25.00]. Luz’s project is trying to fill in some of those gaps. For example, she has seen some of their eggs in the lab, and describes them as small (around 8cm long) and yellow in colour, with tiny hair-like structures all along them. In some parts of the world they can be found on the beach, especially near to kelp forests. The chondricthyans, or cartilaginous fishes, are known to have generally slow growth and reproductive rates, and scientists have theorised that chimaeras share these traits. Luz’s project has found that some species of chimaera are regularly caught as by-catch, meaning that there is an urgent need to confirm aspects of their biology and ecology to fully understand what the impact of fishing activities are on these species [29.10]. Chimaeras are not an important resource in Mexico, and are therefore not typically a target species. But they do seem to be showing up more in the Popotla fishery, which is interesting. Luz hypothesises that this is possibly linked to another species that is an important resource: the California spiny lobster. Populations of spiny lobster have been severely depleted due to overfishing, bringing fishers into competition with one another. Some fishers have taken their gear into deeper waters further offshore, where, Luz believes, they are coming into more frequent contact with chimaeras.
One particular species that Luz has seen regularly is the spotted ratfish [31.40]. This is a species with a characteristic spotted pattern on its brown body, and the long, thin tail of its namesake. Luz has also come across a lesser-known species of shark, called a prickly shark [32.50]. Rarer than the ratfish, prickly sharks only show up occasionally – but are very special when they do. They don’t have the classic shark shape, with a small, robust body and a less prominent dorsal fin that occurs nearer to the tail. But the coolest aspect of them is their skin, which is likely where the name ‘prickly’ shark comes from. Under a microscope, their skin – which consists of dermal denticles, like all sharks – has a ‘starry’ appearance which feels prickly to the touch!
Luz is continuing to research the interaction between these species and fisheries [35.20]. She is collecting data on the species caught and their biology and life history to inform sustainable fisheries management, but also working closely with the fishers. She has found that the fishers are equally curious about the sharks and chimaeras that they catch and want to know more about them. Luz believes this is imperative to effective conservation efforts. It is only by engaging the fishers, working with them, and building trust that we will gain their support and respect. Fishers provide Luz with samples and share their knowledge in return, which Luz wouldn’t have access to otherwise. This is why Luz feels so strongly that we need to consider not just the ecological aspects of conservation, but also the human dimensions.
ABOUT OUR GUEST
DR LUZ ERANDI SALDAÑA RUIZ
Luz is a biologist who aims to understand the impacts of anthropogenic stressors (e.g., fishing, climate change, and oil spills) on marine species, mostly cartilaginous fishes (sharks, rays, skates, and chimaeras). Through her research, she wants to contribute to the management and conservation of these fascinating organisms. Her fascination with marine life began early in life, and since college, she has been captivated by the diversity, biological characteristics, and adaptations of cartilaginous fish. Her work encompasses biodiversity, ecology, fisheries, trade, and conservation, with a particular focus on CITES-listed species, deep-water species, data-poor and data-limited fisheries evaluations, and historical ecology.
Currently, Luz is using awesome tech, such as drones, baited underwater video stations, and ROV, to monitor marine megafauna, including cartilaginous fishes, in Marine Protected Areas. She’s also conducting a historical analysis of guitarfishes and evaluating the capacities of governments in Latin American countries to implement CITES listings for sharks.
In addition to her scientific work, Luz is passionate about science outreach. She believes that knowledge is powerful in helping people make informed decisions that impact our marine species and ecosystems. She also loves art and uses clay modeling, and scientific and naturalistic illustration with outreach purposes. She includes outreach strategies in all her projects to make research accessible, increase the visibility of Latin American countries’ ocean research, and hopefully inspire future shark scientists.
https://www.researchgate.net/profile/Luz-Saldana-Ruiz-2
https://www.instagram.com/erandiscienceart/
