Alaska

It's taken just 24 hours for America's most northern state to deliver two once-in-a-lifetime encounters. Having departed Alaska's popular port, Seward, the evening before, we sailed along the striking snow-capped coastline before tucking into anchor on a branching fjord off Aialik Bay, 40 nautical miles away. There, against the silky blue crystal-like mass of ice of Holgate Glacier, we enjoyed sundowners.

Now, I'm watching a 15-metre, 30-tonne humpback whale feeding at the water's surface just a few metres away. And when we think the scene could not get any more astonishing, nature unleashes something special. The humpback opens its mouth to guzzle down thousands of herring, but as it does so, a tufted puffin appears inside – cheekily attempting to steal a fishy dinner. As the humpback slowly closes its mouth, saltwater starts to pour out like a waterfall from all sides. There's an audible gasp from the boat passengers as the puffin escapes into flight in the blink of an eye.

Considered a keystone species in the region – their presence enables the growth of kept forests and controls invasive sea urchin populations – sea otters are remarkable creatures that use tools, such as stones, to break open mollusc shells for food. Once sought for their pelts, population numbers have bounced back since a ban on hunting was introduced. However, according to the International Union for the Conservation of Nature (IUCN), they remain endangered.

Meanwhile, towering cliffs and granite precipices fringe the region, providing safe havens for hundreds of thousands of breeding sea birds. From puffins, kittiwakes and auklets to cormorants and murres – sightings are abundant across the Alaskan coastline. Shorelines also harbour moderate colonies of Stellar sea lions – the most enormous sea lion in the world and an endangered species. They can often laze along the granite outcrops or swim in the water. Spot them on Zodiac cruises, when excitable juvenile Stellars, often leap and chase in the wake of the boat.

A highlight – mainly as they are infamously hard to spot – is the brown bears that inhabit this region. Coming out of hibernation in the late spring and early summer, bears typically consume seasonal produce – from berries and grass to insects and fish. However, when the autumn comes, they actively seek out salmon, feasting on the fatty layer under the skin and oily roe to put on weight for winter. Like with all nature, brown bear sightings cannot be guaranteed. However, expeditioners are most likely to spot this predator around the open shorelines of Kukak Bay and Geographic Harbour, where the bears hunt for salmon.

An early morning Zodiac tour into Geographic Harbour offers a sighting I never imagined – a female brown bear and her two cubs attempting to catch fish. Our knowledgeable guide edges the boat into the shallow bay before quietening the engine. As we watch with binoculars in hand, it’s clear that the mother is doing all the hard work while the cubs chase and paw at each other’s snouts. She heads to the stream – pacing up and down the pebbles, working out the best place to go in – then takes to the water with a large splash, leaping in amidst the flow with her right paw poised to make her catch. And make her catch she does. Retrieving the pink salmon with her mouth, the mother bear casually heads into the grassland – before turning and summoning her cubs to join her.

Salmon are critical to Alaska’s larger ecosystem. They provide a valuable diet to the brown bears that hunt in this region and other species, including seals, black bears, wolves, eagles, gulls, and even orcas. Remnants left behind by predators collect in river bends and shallow pools and, eventually, break down – providing valuable nutrients for invertebrates and insect eggs. Meanwhile, decomposing salmon carcasses lost in forest waterways contribute nitrogen, phosphorus, sulphur and carbon for vegetation growth – which, in turn, offer verdant habitats for fauna.

This salmon run begins in April or May and extends into August, with king salmon being the first to return to Alaska’s waterways. Sockeye, pink, chum and silver salmon follow soon after – with king salmon, sockeye, silver and chum swimming deeper up larger rivers, looking for a safe place to lay eggs. By contrast, pink salmon are known to remain in the lower arms of rivers and streams, closer to the ocean – and are, therefore, the most likely species to be spotted in the jaws of a brown bear. The salmon that survive to make it upriver bury their eggs in the permeable gravel of the freshwater – allowing oxygenated water to encircle the eggs.

Once hatched, young salmon spend up to two years heading back downstream, adapting to the increasing salt water. Upon entering the ocean, the salmon remain at sea for several years until maturity – before returning to Alaskan rivers to spawn. And so, the cycle starts again.

• Hats (for sun and wind protection) and waterproof gloves
• Waterproof, rubber boots that reach the knee - these may be provided on board. Check with your operator before setting off
• Parkas may be provided onboard. Check with your agent or operator before setting off
• Small backpack, with waterproof cover, for excursions
• Reusable water bottle
• High factor sunscreen Insect repellent
• Binoculars for wildlife watching
• Small drybag for phones, wallets, camera and medication US dollars for buying souvenirs