October 8, 2018

Photo: John O’Connor

Photo: John O’Connor

I’ve learned many things from working with megafauna here in Ireland, but perhaps the most impactful lesson has been that a major key to success in wildlife research is flexibility. As someone with a strong perfectionist streak, I’ll admit that it’s taken about two field seasons of chasing the ever-elusive basking shark to really embrace this new attitude. But, after this past week, I could not be more grateful to have done so.

A captured “common skate”.  Photo: Davey Benson,  taken   from   The Shark Trust

A captured “common skate”. Photo: Davey Benson, taken from The Shark Trust

Roughly one year ago, I met Dr. Patrick Collins at Queen’s University Belfast, where I’m currently a visiting researcher. Patrick is a benthic ecologist – his focus is on the seafloor (the “benthic zone”) and the organisms that reside there. Among these organisms is the skate. Closely related to sharks and rays, skates are elasmobranchs. This means that they possess features distinct from teleosts (bony fish), most notably a skeleton made of cartilage. At first glance, skates and rays can be difficult to tell apart, as both have flattened bodies and can be found on the ocean floor. However, these animals differ in terms of both their appearance and life history strategy. Skates are perhaps most easily distinguished from rays by their shape, more triangular with an elongated nose. A skate’s tail is also stockier, with no stinging spine but rather thorny scales running laterally down each side and two small dorsal fins near the tip. Finally, skates exhibit a different mode of reproduction. Most rays are viviparous and give birth to life young, while skates are oviparous, which means that they lay eggs (commonly referred to as “mermaid’s purses”). Learn more about skates and rays here.

Mermaid’s purses, or skate egg cases, often wash up onshore in coastal areas.  Photo: Pembrokeshire Coastal Photography

Mermaid’s purses, or skate egg cases, often wash up onshore in coastal areas. Photo: Pembrokeshire Coastal Photography

Although I actually collected mermaid’s purses on the beach as a child, I’ve always considered skates the lesser-known cousins of the elasmobranch family. Even I didn’t know much about their life history or physiology until about a year ago, when I was introduced to Patrick. What fascinated me most about the animal he proposed to study was that I wasn’t alone in my ignorance. In fact, until about 2009, the species didn’t technically exist at all. This is particularly surprising because the flapper skate (Dipturus intermedia) is the world’s largest skate species. Females (which are larger than males) can reach almost ten feet in length at maturity. Like sharks such as great whites, they serve as apex predators in the ecosystems where they reside, feeding on large fish and crustaceans. In fact, these animals are so large that smaller sharks are a consistent part of their diet. Other than that, however, very little is known about them. This is partly because the flapper skate has seen a precipitous population decline in the last one hundred years [1], to the point where it is now considered critically endangered.

Photo: Patrick Collins

Photo: Patrick Collins

This was not always the case. Giant skates were once so abundant in the UK and Ireland as to be referred to collectively as the common skate. However, as with many apex predators, common skate possessed life history strategies that rendered them exceedingly vulnerable to fishing pressures: site fidelity (small home range), slow growth, late maturation, and a long lifespan. Thus once decimated, it became nearly impossible for the populations to recover. Even when not directly targeted for sport or sustenance, these large animals were prone to being captured as bycatch in multiple different types of fishing gear, including trawls. Because most do not migrate, entire local populations could be easily targeted and captured. What’s more, fishermen tended not to note the number of skate being captured; rather, all species were clumped together in fisheries records as bycatch under the collective category of “elasmobranch”. It therefore became challenging to track exactly how quickly regional populations were declining. Perhaps because of this, some researchers now consider skate the most vulnerable groups of marine fishes [2]. And, as if the situation weren’t sufficiently dire, in 2009 it was discovered that the common skate was actually two different species that closely resembled each other – the flapper skate (D. intermedia) and blue skate (Dipturus flossada). This meant that flapper skate populations were even smaller than initially considered, and it is now known that the global distribution of this species specifically is restricted to the western coasts of Ireland and Scotland, with only one breeding site recorded in Ireland. The species is predicted, without further conservation efforts, to become the first commercially-landed fish to be driven to extinction through overfishing.

Though efforts to combat the demise of the flapper skate are currently underway, data deficiency can be conservation’s biggest enemy. Needless to say, when Patrick approached me last fall about conducting a telemetry and biologging project with this species, I was hooked (no pun intended). The more I learned about the flapper skate, the more fascinated I became. It’s worth repeating that this is a skate that actively hunts and consumes sharks. Furthermore, it’s rare that one has the unique opportunity to work with an organism on the brink of extinction. As a result, I found myself last Sunday on a flight to Dublin mere weeks after my return to the states following a summer of basking shark searching. This was to be the first stage and foundation of a series of projects on flapper skate in Ireland and the UK, all directed at the recovery of this species. My goal was two-fold. I would spend the first half of this trip at the Queen’s University Marine Lab in Portaferry (Northern Ireland). Here, I would work on a new method of attaching accelerometers to flapper skate with Dr. Natasha Philips, a recent PhD graduate of Jon Houghton’s lab. Many skate researchers have attached transmitters most effectively to the tail using cable ties, which can cause lasting harm after longer periods of time. But for her PhD project, Tash had developed a method of tag attachment for ocean sunfish (Mola mola) using a rubbery but durable material. She and I, along with Dr. Lawrence Eagling (another QUB graduate), would combine forces do something similar, carving small packages out of buoyant foam material to contain our accelerometers and attaching them to this same rubbery material, which would be wrapped around the skate’s tail.

The packages were to be attached to the tails of skates caught during The Helm Skate Fishing Festival.  Photo: Haley Dolton

The packages were to be attached to the tails of skates caught during The Helm Skate Fishing Festival. Photo: Haley Dolton

Once the packages were prepped and ready to go, my second goal was to test them. This took me along the western coast of Ireland to the aptly-named Westport, a stunning mid-sized town that takes pride in consistently being among the “tidiest” in the country. I was joined in this part of my journey by Haley Dolton, a recently graduated Master’s student from the University of Exeter under Dr. Matthew Witt and a fellow basking shark researcher. Together, we would attend the Helm Skate Festival, a flapper skate fishing tournament hosted by The Helm, a restaurant and bar in Westport. Though critically endangered, the flapper skate remain targeted for the sport of catch-and-release angling. Thus far, this is not though to contribute dramatically to the population decline. Indeed, anglers have been known to re-capture the same skate during consecutive days, months, and years of fishing (they often assist in the scientific tagging effort), and at least at this particular festival, all captured skate seem to have been released in full fighting form.

More importantly, however, capture-and-release also happens to be the method that most scientists use to attach equipment or tags in order to monitor wildlife populations. Thus, in addition to trying to reduce the initial detrimental effect of transmitter attachment, we also wanted to look at the immediate behavior of the skate following release. Parallel studies have already been conducted in several shark species, many by Dr. Nick Payne at Trinity College Dublin, and the resulting data has been useful in assessing the costs and benefits of different fishing or scientific practices. For instance, some sharks bolt after they’ve been captured and tagged, or swim erratically in the water column. All of the time and energy spent in this post-release behavior could be more prudently expended foraging or mating in a productive habitat. With such an established angling community here in Ireland and the UK and a future research effort for flapper skate on the horizon, we wanted to see how long it would take the skate to behaviorally recover (i.e. resume normal behavior) following release. This information could be useful not only for fishermen, but also in conservation practices or in studies that examine movement behavior and habitat use using transmitters and loggers. And, as I prepared to work with yet another species of marine megafauna in this amazing ecosystem, there was a very significant perk that the Helm Skate Festival would offer: I would finally lay my eyes on a flapper skate. Given its current population status, that may be something very few people will be able to say even by the end of the next decade.

A flapper skate freshly released following capture . Photo: John O’Connor

A flapper skate freshly released following capture. Photo: John O’Connor

Read on to learn more about my experience at The Helm Skate Fishing Festival.

Works cited:

[1] Wearmouth, V. J., & Sims, D. W. (2009). Movement and behaviour patterns of the critically endangered common skate Dipturus batis revealed by electronic tagging. Journal of Experimental Marine Biology and Ecology, 380(1-2), 77-87.

[2] Dulvy, N. K., & Reynolds, J. D. (2002). Predicting extinction vulnerability in skates. Conservation Biology, 16(2), 440-450.