Key takeaways
- Season, route, boat length and destination all follow the herring.
- The stock gathers somewhere sheltered for months, then leaves to spawn.
- It has shifted along the coast within living memory, and more than once.
- Whale-watching towns have gained and lost the whales as the fish relocated.
The fish that runs the Norwegian coast
Norwegian spring-spawning herring is one of the largest fish stocks in the world, and its annual cycle is the closest thing the Norwegian Sea has to a heartbeat.
In spring it spawns along the coast. Through the summer the young drift north while the adults feed in the open Norwegian Sea, growing fat on the plankton bloom. In autumn the adults leave the open sea and come inshore to spend the winter somewhere sheltered, packed in enormous concentrations, barely feeding and living off what they built up over summer.
That winter concentration is the event everything else keys off. It is millions of tonnes of oily, energy-rich fish held in a small volume of protected water for months. Nothing in the North Atlantic ignores that.
Everything after that point in the season is a consequence of one gathering: the whales, the birds, the fishing fleet and the boat you are standing on.
Why the whales come
For an orca, a wintering herring shoal is the difference between working hard for a living and not.
A large orca needs a serious amount of food every day, and getting it from scattered prey burns more energy and time than it returns. A dense overwintering shoal collapses that problem: the fish are concentrated, they are relatively sluggish in cold water, and they are there for months rather than passing through.
Humpbacks make the same calculation and arrive for the same reason. So do fin whales in some years, along with white-tailed eagles, gulls, guillemots and cormorants working the same water from above. A herring overwintering ground is not a place where whales happen to be. It is a place built entirely around one fish.
The timing works in the whales' favour too. Cold water slows a herring down, and a shoal that has spent two months barely feeding is not at its most athletic. The winter aggregation is both the largest and the least evasive the fish will be all year.
The fjords north-east of Tromso, where the herring currently winters
A stock that nearly disappeared
The herring has not always been reliable. Through the middle of the twentieth century the fishery expanded enormously, and by the end of the 1960s the Norwegian spring-spawning stock had collapsed to a small fraction of its former size.
The recovery took decades of heavy restriction and was not guaranteed. From a low point in the 1970s the stock rebuilt through the 1980s and 1990s into the large biomass that supports today's wintering aggregations, and the whale-watching industry of northern Norway exists downstream of that recovery.
It is worth stating plainly because it puts the current situation in proportion. The orcas gathering in these fjords each winter are doing so because a fishery was pulled back from the edge, not because northern Norway has always been like this.
The wintering ground keeps moving
Here is the part that shapes your day at sea. The herring does not overwinter in the same place from decade to decade, and when it changes address the whales change with it.
Through the 1990s and into the 2000s the great overwintering concentrations sat in the fjord systems well to the south of Tromso, and the whale watching of that era happened there. Then the fish moved. It spent seasons further out and further north, and by the early 2010s the reliable winter concentrations had shifted to the fjords north-east of Tromso, in the waters around Skjervoy and Kvaenangen.
Nobody fully explains why. Water temperature, the size and age structure of the stock and where the young fish grew up are all part of the argument, and the honest position is that the shift is better described than understood.
What is not in doubt is the consequence. Towns that had orcas outside the harbour lost them. Tromso, which is well placed as a base with an airport, gained a whale-watching industry that has to sail two and a half hours to reach the animals. That journey is not inefficiency. It is the current distance between the city and the fish.
It moved
The herring's winter address has shifted along the Norwegian coast within living memory, and the whale-watching fleet moved with it rather than the other way round.
What happens if it moves again
It will. The only question is when and how far.
If the wintering ground shifts further north or further offshore, the day gets longer or the sightings get thinner, and the operators will adjust or stop running. If it comes back south, the boats will get shorter and the seasons easier. Neither outcome is under anyone's control.
This is a good reason to treat any confident statement about the season with mild suspicion, including from us. The pattern of the last few winters is a reasonable guide to the next one and a poor guide to the one after that, and the operators who read the situation best are the ones talking to fishing boats rather than to last year's brochure.
It is also, for what it is worth, the most interesting thing about this whole business. You are not visiting an attraction. You are visiting a food source, and the animals are there for exactly as long as it pays them to be.
