Anja Murray: Even though many sharks are predators, it is we humans who pose a threat

Common Angel Shark (Squatina squatina) swimming over sea grass: this species is particularly vulnerable to bottom trawling

Ireland has half a million square kilometres of ocean territory, filled with incredible, strange and beautiful creatures. Brightly coloured anemones live on the seabed among forests of kelp. Huge Spider crabs, more than half a metre across, scuttle about the seafloor. Deepwater coral reefs have been slowly growing for thousands of years, teaming with life and giving shelter to young fish in the deep sea. Sea sponges, one of the oldest groups of animals on earth, fill healthy underwater ecosystems with whorls of geometric colour. But to most of us, the creatures who live in these waters are strange and unknown.

One group of animals at home in Irish waters is sharks. There are 39 different shark species and 28 species of skates and rays (closely related to sharks) living in the ocean around Ireland, long before people ever reached these shores. One species, the common skate, can live to be 100 years of age and get as large as 3 metres — though contrary to its name, this skate is now no longer common. It is classified as ‘critically endangered’ here and is only one step away from being classed as ‘extinct in the wild’.

One of the incredible traits that many sharks, skates and rays share is the ability to perceive very small electrical signals, such as the electrical signature from the heartbeat of a fish or a shrimp swimming through the water. As predators living in often dark water, being able to detect a well-concealed shrimp, or a cryptically coloured fish through the electrical charge generated by their heartbeat means that these sharks, skates and rays can hunt without seeing, hearing or smelling their prey.

But while many sharks are predators, the vast majority pose no threat to humans. More people are killed each year worldwide by defective toasters than by sharks. It is we humans who pose a threat to sharks, and many are now endangered because of human activities.

Incredibly rare angel shark in Galway this morning. Confirmed by The Marine Institute. @rtenews @InlandFisherIE pic.twitter.com/CiNfInM1Pk

— Colin O'Loan (@irishcharcoal) May 28, 2023

At the end of May, a very rare Angel shark was seen by a group of young kayakers in shallow water in Galway Bay. The kayaking instructor who filmed the sharks managed to get exceptional footage, showing the big wings on these sharks that gave rise to the name ‘Angel’ shark. 

Angel sharks are a bottom-dwelling species, which makes them especially vulnerable to bottom trawling. This is a fishing practice in which large nets are towed along the seafloor and the weights that hold them down are hugely damaging to seafloor habitats. Because seafloor sediments are churned up in the process, many marine species don’t survive repeated trawling and vast amounts of carbon stored in seafloor sediments are also released by bottom-trawling fishing. Angel sharks are just one of many victims of such destructive practices, their population has plummeted so drastically in recent years that they are now classified as critically endangered. Tralee Bay is known to be one of the last strongholds of this species in Ireland.

Another shark that occurs in Irish waters is the rare Porbeagle shark. Unlike most other fish, porbeagle sharks are warm-blooded. In April 2022 a team of research scientists caught, tagged and released one off the coast of Donegal that was the largest ever recorded in Irish waters. Because lots of female Porbeagle sharks show up in Irish waters for a short period each spring, scientists are currently investigating the likelihood that Irish waters are a globally important reproductive area for this species. But like many sharks, the population of porbeagles has drastically dropped in recent years, due mainly to their being caught in commercial fisheries, and they have now become critically endangered. Ireland has a global responsibility to protect this species, in particular to safeguard their breeding areas.

Shark, skate, and ray eggcases

Another charismatic shark at home in Irish waters is the Basking Shark, often seen in Irish coastal waters from June onwards. These enormous creatures are the second largest fish on the planet, though they survive on a diet of plankton. Rather than being a proper predator, basking sharks just swim slowly through the water, often near the surface where plankton are richest, filtering their food from the seawater that passes through their enormous mouths and the gills at the side of their head. These are such slow-moving animals that there’s a saying in Irish: ‘Comh sámh le liamhán’ — as tranquil as a basking shark.

‼️New research by @TheSimsLab and others (such as IBSG co-founder Simon Berrow) finds that the northeast Atlantic, including Ireland, is a critical habitat for courtship/reproductive behavior. This is the first such habitat identified for basking sharks globally🤯 https://t.co/3OBqGwZ5e2

— Irish Basking Shark (@BaskingIrish) September 8, 2022

In May, a large group of Basking Sharks was filmed off the coast of County Clare by Dr Simon Berrow of the Irish Basking Shark Group. Filming with a drone from above, the footage shows that the group were ‘circling’ in a formation known as a ‘torus’, a behaviour that is thought to be a courtship ritual. On that occasion, there were hundreds, if not thousands of sharks swimming in the area. The sea around Ireland is thought to be key for Basking shark courtship and mating, in addition to being home to a large proportion of the remaining global population. An amendment to the Wildlife Act in October 2022 has given Basking sharks much-needed legal protection, so that disturbing and harassing these animals is now illegal. 

As top predators, sharks have a vital role in maintaining marine ecosystems. They are considered 'keystone species', keeping the intricate webs of ocean life in balance. To give sharks the protection they need, we have to ease the pressure of industrial fishing and introduce Marine Protected Areas. These are zones out at sea where fish nurseries and other marine habitats are given respite from our relentless exploitation, where cold-water coral reefs, kelp beds and other fish nurseries are allowed to survive and thrive. Marine Protected Areas help sustain fisheries by giving safe spawning grounds for fish reproduction, and are also necessary to protect increasingly rare sharks, skates and rays. Full protection means that these are places where fish of every shape and size can live out their lives without threat of sudden annihilation.

Many of us are optimistic that the Marine Protected Area Bill, due to go to Cabinet before the Dáil takes its summer break, will give hope for sharks, for the future of sustainable fisheries, and for the many wondrous and often poorly understood creatures at home in the sea around Ireland.