Grey Seals on rocky bay

How Seals Benefit Fisheries

As native seal populations have begun to recover over the past several decades due to conservation efforts and protection policies in Ireland, interactions between seals and fisheries have escalated. In recent years, tensions have reached a boiling point as fishermen have renewed campaigns for the government to legalise the culling of seals. Fishermen believe populations are now out of control and claim that seal depredation poses a serious threat to their livelihoods. While the struggles of Ireland’s fishermen need to be taken seriously, it is a misconception that seals are the most prominent threat to coastal fisheries, when ultimately, seals play an essential role in sustaining the health of our oceans on which the industry depends. 

Established colonies of Grey and Common seals must compete for the same species of fish as commercial fisheries and forage across renowned fishing grounds off Ireland’s Western and Southern coasts. Due to increased competition and spatial overlap of resources, seals are known to inflict physical and economic damage on fishermen’s catch and gear. Because seals are more visible than other predators–and thus the impacts of their depredation more noticeable–seals are often targeted as major threats to the livelihoods of small-scale fishermen. The resulting conflict has reinforced notions for culls as communities dependent on the fishing industry believe managing seal populations will decrease depredation and raise fish stocks. However, this perspective does not account for the complexity of marine food-webs, the essential role of seals in coastal ecosystems, or for the devastating impacts anthropogenic activities are having on our oceans. 

Seals are apex predators in Irish waters which means they play an intricate role in coastal food webs and are vital to sustaining the overall health of marine ecosystems. As top predators of the food chain, seals regulate prey populations and lower trophic levels connected by predation, helping keep the food web in balance. Because seals populate marine and terrestrial habitats, they can be used as indicators of changes to food webs because their reproductive rates are affected by environmental factors such as the quality, quantity, and availability of resources.

Seals also provide important ecosystem services by increasing primary productivity in feeding areas, recycling both macro and micronutrients through returning massive amounts of nutrients through excrement, feeding plankton and other consumers up the food chain to humans. The migrating and foraging behaviours of seals aid the translocation of nutrients across environments and water columns. When seals forage in waters, they move bringing nutrients from greater depths to the surface and bring nutrients from marine to terrestrial environments when they haul-out on coastal areas rest, moult, and pup.  

As one of the top predators, humans exert a powerful influence over marine ecosystems and ecological processes. Unsustainable practices that are exploiting, disturbing, and destroying aquatic resources and environments are posing a serious threat to marine species, the fishing industry, and the future of the planet. As semi-aquatic marine mammals, seals are especially vulnerable to a range of anthropogenic effects including resource competition, pollution, habitat loss, acoustic/physical disturbance, and extreme weather resulting from human-induced climate change. 

From 2001 to 2020, Ireland ranked among the top five worst countries in the EU for overfishing, catching an estimated 765,000 tones more fish than scientifically advised for max sustainable yield (MSY). Since the development of industrial fishing, populations of predatory fish populations (commercially preferred species like cod, tuna, herring, etc.) have drastically declined in coastal areas disrupting ecosystem structures and functions.  Humans impact the environment through overfishing and climate change which have cascading effects down the food web, putting immense pressure on predators to compete with one another. As a result, seal-fisheries interactions have increased over the years as seals must compete with humans, other marine mammals, and predatory fishes for the same prey. 

Due to increased seal-fishery conflict, several studies have been conducted over the past decade to investigate this relationship and the effectiveness of current management strategies. Research has shown that seal populations do not have a significant impact on the stock of commercial species, depredation to fish farm stocks increase when there is insufficient wild prey available, and that only a small fraction of seals are responsible for inflicting recurring damage to fish stocks. Thus, indiscriminate culls of seal populations would not only be unethical but ineffective in the long-term. 

Some non-lethal measures already used by fisheries around the world to mitigate seal depredation include seal-proof modifications to gear and nets (making gear more visible and mesh size smaller), acoustic deterrents, and alterations to operational procedures – such as reduced net soak times, relocating fishing efforts further offshore, and avoiding fishing around seal haul-out sites). Further research into seal-fishery interactions in Irish waters must be done in order to inform management plans that prioritise seal conservation while acknowledging losses to fishermen. 

Unsustainable industries and practices also have grave consequences for the future of Ireland’s fishing industry. Despite challenges posed by Brexit and the coronavirus pandemic, Ireland’s seafood sector employs over 16,000 people and contributes over €550 million annually to the economy. With so many livelihoods (many of them remote coastal communities) dependent on healthy marine populations and oceans, current practices are jeopardizing the viability of the fishing industry for future generations. If EU waters were properly managed and fish stocks rebuilt above levels of MSY, the EU could provide food for an additional 89 million EU citizens, generate an extra €1.6 billion in annual revenue, and create over 20,000 new jobs across the continent within a generation.  

When natural resources come under pressure, top predators become scapegoats and populations are controlled as a temporary solution.  However, band-aid solutions like the culling of seal populations fail to address larger systemic threats to marine ecosystems posed by unsustainable fishing practices, climate change, and pollution. Rather than looking at seals as part of the problem, the members of the fishing community need to realize they are integral to the health of Ireland’s coastal ecosystems and consider seals as part of the solution moving forward. 

Written by: Sarah Hurme


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