The real cost of predatory seals to coastal fisheries

Lost or partially eaten catch. Damage to nets and traps. Decreased fish supply. Explore the real cost of predatory seals to the inshore fishery industry


Harbour seals have diverse habitats. They can be found throughout the northern hemisphere in bays, rivers, estuaries, and even up near the icebergs in glacier tidewater. But their favorite place to spend their time is just off the coast, under the boats of inshore fisherman.

What was once a just a game of cat and mouse between fisherman and seals has become a full blown battle for survival. In a lot of fishing villages off the coasts of Sweden, Ireland, Scotland, and the Baltic coastal areas, the seals appear to be winning.

One independent fisherman explains the impact of seals on his business: “Seals have more [or] less killed off the cod net fishery in our area.”  Another says, “Seals have become a big problem in some areas and have been seen as far as 130 miles from the nearest point of land. Fish can be hard to find most of the time and when what you catch is damaged beyond sale it’s really heart breaking. The seal will tend to only eat the liver of a fish which means it normally destroys the fish beyond sale.”

For some inshore fisherman, who are typically independently owned, small scale operators, losses to daily catch can range from 10-20%. But for the less fortunate, loss of catch can reach 30% or even 50% or more.

One fisherman who had no choice but to shut down his business explains: “They put me out of fishing with nets. They would follow my boat and wait for me to shoot my nets. We used to tangle nets for monk fish as well but not anymore; can’t keep a whole one in the nets.”

As seal populations have boomed over the past over the past several decades – due in part to regulations prohibiting the shooting of seals – coastal fishermen have done what they could to protect their catch. Fishing tactics, avoidance measures, harmful acoustic deterrent devices. Nothing seems to have worked.

The Hidden Costs of the Lost Catch

The true cost exacted by predatory seals to coastal fisheries is hard to calculate, but it may well be a lot higher than most of us realize. That’s because it’s hard to know just how many fish have disappeared from fishing nets. But the disappearance of whole fish is just the start. Seals also leave fish half eaten and damaged. They also force fisherman to change how, when, and where they fish. It’s all part of an ongoing effort to outsmart the seals.

To calculate the actual economic cost of predatory seals on coastal fishing enterprises, we need to add up all the direct, indirect, and hidden costs. These include lost whole fish, partially eaten fish, decreased fish supply in fishing zones, direct damage to fishing nets and gear, shorter lifespan of equipment due to frequent replacement, increased fuel usage, greater travel times back and forth to shore, and the decreased time nets can be left in water each day.

Lost and Half Eaten Catch
By far the biggest cost is lost and damaged catch. Lost catch can be hard to calculate, as those fish disappear without a trace. While the losses vary dramatically from one fishery to the next, almost no inshore fisherman can avoid losses to seals.

On average, estimates of 15-20% of total losses from both damaged fish and lost catch seem to be the norm. But the numbers in areas with high seal populations can be much worse, sometime averaging losses of 50% or more.

Damage to Gear
Damage to fishing gear is the second biggest cost. Seals are highly intelligent, and some have figure out that by tearing large holes in the net panels, they can chase the fish into the netting and then wiggle them lose for an easy meal. Damage can occur to the nets, traps, or hooks, together with the uneaten fish remains. Damage also can occur to tows and hauls.

It’s not only the direct costs to damaged gear, but the long-term replacement resulting for worn out gear with a much shorter lifespan.

Operational Costs
Fisherman have been forced to adopt new tactics to help minimize seal interactions. Some decrease the amount of time they leave nets in the water overnight, or the number of days nets are left in the water each week. In search of better fishing zones free of seals, fisherman spend more fuel increased travel time back and forth from harbor.

The reality, however, is that most inshore fleets have limited options for alternative fishing areas – with no guarantee that the conditions will result in a better catch.

Decreased Fish Supply in Fishing Zones
When seals abound, fish tend to seek refuge in other areas. Although seals are certainly not the only cause of decreased fish supplies, scarcity of fish in fishing zones is yet another cost impacting the fishing industry.

As we explore the true costs of seal predation to inshore fisheries, we begin to understand just how big of an impact that seals have had on the livelihoods of fishermen – and the local coastal economies they help sustain.

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