Winter wildlife extravaganza

in Juneau’s Auke Bay

During late November and early December, 2015, Auke Bay harbor put on a wildlife spectacular, drawing photographers, reporters, and just plain gawkers (such as me). Hordes of young-of-the-year herring, mixed with a few capelin and sand lance, milled around the docks and boats. The banquet of small fish also drew many predators, who put on a good show for observers.

Why are there so many young herring in the harbor this year? There are possibly several reasons, suggests Michelle Ridgway (Oceanus Alaska). It may have been a good spawning season in spring. The sunny spring, plus an El Niño, warmed the harbor waters, even at considerable depths, and all the spring run-off from the soggy land brought in nutrients. Those conditions produced a fine bloom of phytoplankton, which led to good body condition and burgeoning populations of zooplankton. For example, Ridgway has noticed extended reproduction of little shrimp-like crustaceans called mysids, extra-large fat globules in copepods, an abundance of amphipods not far from the surface, and an unusual influx of ‘sea butterflies’ (molluscs that fly through the water). That made excellent foraging for baby herring. In addition, young herring may seek protection from the massive maws of humpback whales by moving into shallower bays and harbors, with docks and boats, where the whales are less likely to forage intensively.

Herring and other so-called forage fishes often form densely packed balls, especially when predators are lurking about. When a predator dives through the ball of fish, the survivors scatter in all directions, but not far and only briefly, before returning to the tight cluster. Researches have called this behavior ‘the geometry of the selfish herd’: each fish trying to put as many other little fish as possible between itself and predators. The result is a tight ball of nervous, jittery fish.

The baby herring in the harbor had every reason to be jittery. The millions of small fish were being attacked on all sides by throngs of predators. They may have eluded most of the whales in the confines of the harbor, but other predators took advantage of the great aggregation.

A gang of Steller’s sea lions cruised rapidly back and forth, diving continually, probably after pollock that were gorging on the herring. The pollock drove the little fish toward the surface. The sea gulls knew this, of course, and hung about, just waiting for the fleeing fish to get close to the surface where the gulls could nab them. Indeed, the fish were caught ‘between the devil and the deep’ (the gulls and the aquatic predators respectively).

Several harbor seals were there, some with well-grown pups. They did their share of fish-driving too, but usually not near the sea lions. I watched one seal surface-swimming slowly along, on its back, in a most relaxed fashion. It may have been looking down into the depths, for eventually its head went down, followed by the plump body, into a mob of fish.

Scattered Pacific loons and little clusters of common mergansers foraged away from the biggest crowds of predators. Marbled murrelets in snazzy winter plumage could be observed at close range; they were much less skittish than in the breeding season.

The most amazing sight was the huge flock of common murres—many hundreds of them. They rafted up just beyond the last float and split off occasional smaller bunches that moved in among the inner floats. They, and everybody else except the gulls, avoided the sea lions that charged to and fro. I had never seen so many murres before, except at the St Lazaria nesting colony on the outer coast. The murres talked to each other constantly, except when they were diving.

murres-in-Auke-Bay-Jos
Photo by Jos Bakker

That huge concentration of murres was arguably the most unusual happening in the harbor. All the other predators visit the area rather regularly to feast on small fish that spend the winter there. Although murres nest on the outer coast, they tend to move closer to shore in winter, congregating where prey is abundant. But we don’t customarily see the murres in such numbers in Auke Bay harbor. Furthermore, over near Glacier Bay, good observers reported uncountably huge numbers of murres moving about.

The throngs of murres may be a sign of bad news, however, according to John Moran (NOAA). A mysterious oceanic anomaly in the Gulf of Alaska called the Warm Blob (because water temperatures are as much as five degrees (F) above average) created nutrient-poor conditions that greatly reduced productivity and thus decreased the abundance of fishes that feed on plankton, or at least caused them to move to deeper waters where diving birds can’t get them. The Blob developed in 2013 and its effects have contributed to reduced nesting success and great mortality of some marine birds in the Gulf. The poor food supply may have been one factor that drove the murres we’ve seen in Auke Bay out of their usual foraging areas in search of better feeding conditions.

All those baby herring in the harbor seem to offer a ready banquet but, in fact, those little fellows have very little fat because they put their energy into growing as fast as they can. On a gram-for-gram basis, they are much less rewarding than capelin or adult herring, for example, and even less than krill, according to data of Moran and colleagues. So a murre or any other predator would need a lot of them in order to survive—and that’s certainly what was available in the harbor.

Humpback whales were reported to pass by the harbor upon occasion, but there are other spots where they might find better foraging. Seymour Canal is a good place for foraging on krill, for example, and adult herring (far more nutritious than the young ones) from all over Lynn Canal winter in deep, dense schools northward of Tee Harbor. When a whale dives deep through such a school of herring, some of the fish try to escape up shallower water, but there the sea lions can get them. Sea lions themselves may attract the attention of transient killer whales; a few years ago, Moran watched killer whales take down five sea lions (plus two probable kills) in five days. But in Auke Bay harbor, the foraging sea lions were quite safe from the killers.

Eagles were notably scarce in Auke Bay harbor during this extravaganza, although they are known to feed on murres (we saw the evidence in Berners Bay one spring). Perhaps the eagles sought out the adult herring to the north.

A little squad of goldeneye ducks quietly kept to themselves along a rocky shore of the harbor. Seemingly uninterested in the shimmering mass of herring, they may have been looking for molluscs.

Thanks to John Moran of the NOAA lab and Michelle Ridgway of Oceanus Alaska for extensive discussion, not all of which could be packed into this essay.

Gambling on Berners Bay

playing the annual wildlife lottery

Going to Berners Bay in spring is always a bit of a lottery—you never know what you might see there. Maybe nothing much, except some scenery. But if you hit it just right, things can get pretty interesting.

When the eulachon (a.k.a. hooligan) are in the bay, staging for their spawning migration up the rivers, there might be dozens upon dozens of sea lions, foraging cooperatively and rafting up to rest from their exertions. Harbor seals would be there too, in quantity, and humpback whales would be likely to cruise through. Orcas may arrive, in search of unwary sea lions or seals.

Once the hooligan are in the rivers, the action in the bay dies down. Tens of thousands of gulls and ten hundred eagles gather to gorge on these oil-rich, slow-swimming fish, which run a fearsome gauntlet of predators in the lower reaches of the rivers.

Springtime also brings shoals of herring, which often spawn in the bay. That draws lots of eagles, which line the shore and swoop down to snag a distracted spawner. Gulls feast on the eggs that coat the rockweed in the intertidal zone, and humpback whales come to fill their maws with fish.

One year, our annual kayak junket to Berners Bay happened when both hooligan and herring were bringing in hordes of predators, and the bay was a crazy place. We hardly knew where to cast our watchful gaze!

This year, 2011, was different again. The eulachon were up the rivers, attracting clouds of gulls, and only a few sea lions and seals remained in the bay. The herring had spawned recently, and their eggs glistened on the rockweed when the tide went out. The gulls were all busy with the hooligan in the rivers and ignored the herring eggs, and the mobs of eagles were notably absent.

Instead, we saw acres and acres of surf scoters—there must have been ten or twenty thousand of them. What a racket! They spent a lot of time apparently loafing and talking. Every so often, a group of them would head to the shore and nibble on herring eggs, sometimes pulling off chunks of seaweed too. I suspect they were also diving for mussels. Or they would suddenly all dash across the water with great splashing, for no apparent reason. When thousands of ducks do this all at once, it creates quite a ruckus.

Bonaparte’s gulls were diving after pink salmon fry that thronged the shallows and maybe also juvenile herring in the deeper water. Barrow’s goldeneyes in small squadrons swam along the rocky shore, gobbling up herring eggs. A kingfisher dove repeatedly and seemed to catch a salmon fry on almost every try. Three solitary black bears foraged on separate beaches.

A little walk in the woods produced three very dead and dried herring, perhaps dropped by some inept or unlucky eagle or gull. Another possibility, however, is that ravens had grabbed a fish as it tried to spawn in shallow water, or had stolen it from another bird, and stashed it in the trees. Years ago, when I was studying predators at the eulachon run, we noticed ‘rains’ of dead eulachon falling from the trees when the wind blew; they’d been stored up there by a gang of scavenging ravens.

Another stroll in the woods found us in a soggy little opening where lots of skunk cabbage grew. But instead of a cheery array of bright yellow, there were only stubs barely showing above the muck. Something had messily chawed them all off, right down to the mud line. The culprit left evidence of its passing: huge cloven hoof prints and occasional clusters of digested pellets about the size of the end of my thumb. Moose were introduced to the Berners Bay area some decades ago and they have found a nice smorgasbord there—we also noted well-browsed alder shrubs along the upper beach.

So, although we missed the show at the hooligan staging in the bay and the show at the spawning herring, we found plenty to see!

Spring in Berner’s Bay

so much to discover and ponder!

Every year, exciting things happen in Berners Bay. Eulachon (a.k.a. hooligan) run into the rivers to spawn. Herring come in great shoals and often spawn on the rocky shoreline there. And, of course, hordes of their predators come to feast. Every year, also, a little group of kayaking friends tries to be there when all that show is going on. It’s a bit of a lottery: sometimes we find an almost empty bay; sometimes we hit it big-time. This year was a good one!

We got off the beach in Echo Cove by nine o’clock, in good paddling conditions. On the way up-bay, we saw several humpback whales, cruising around, frequently lunge-feeding. This was a good sign that there might be a show developing in the bay. A strange sight was a northern harrier being chased by a squad of gulls. Had it tried an on-the-water snatch, arousing their defensive reaction?

A snarling, writhing ball of dark fur resolved itself into two river otters as we passed. “Otter-wauling” seems to accompany the mating process in otters for some unexplained reason. Although otters mate in spring, the undeveloped embryo does not implant in the female’s uterus until fall, and the cubs are born the following spring. Delayed implantation is common among members of the weasel family.

Way back last fall, we rented the Forest Service cabin for the last weekend in April. Because there were six of us and the cabin is small, two of us chose to set up our tents near the cabin. Cosiness is nice, but there are limits…

Arriving at the cabin about noon, we had plenty of time for settling in and then doing a bit of exploring. Some of us hiked over to the waterfall to see if dippers live there (they do). Along the quasi-trail that squirms along just above the edge of the cliffy shoreline, we found the feathery remains of some predator’s lunch. A few yards farther one, there was another one. And then another. We puzzled over the identity of the feathered prey—black and white, yes, but there are many black and white birds. Then we found yet another scattering of feathers, with some bones and a bill. Aha! These were the remains of a Common Murre. As we scrambled along, eventually we found nine of ten leftovers from the lunch of the predator(s)—probably eagles. So we called this route Murre-der Row.

murre-der-2011-kh
Field sketch page documenting Murre-der evidence. Illustration by Katherine Hocker

That evening, things were popping right in front of the cabin. Bonaparte’s Gulls were diving for tiny fish near the shore—probably catching young pink salmon that had hatched recently. A shoal of herring arrived and predators soon followed. Sea lions, mostly juveniles, were having a grand time, often porpoising in pursuit of their dinner. Some invisible underwater predator, presumably a big fish such as a king salmon, was terrorizing the herring too. Panicked herring were leaping every-which-way out of the water. Some of them stranded themselves, or stunned themselves, on the shoreline rocks. The local raven took full advantage of these freebies, making regular trips, fully loaded with fat herring, from the rocks to a particular place (presumably a nest) south of the cabin.

This same raven, or its mate, had earlier scavenged things from the outflow of the tiny stream by the cabin, where previous cabin users had dumped their garbage. Body parts of Dungeness crab still lay near the tideline, along with bits of cauliflower (!), which were wisely rejected.

As twilight crept in, we heard the song of our first Hermit Thrush. A fine ending to a good day.

Cruisin’ to Berners Bay

in search of an annual wildlife congregation

Every year, Juneau Audubon offers several spring cruises to Berners Bay, not far north of town. There is always a hope that the cruise might happen to arrive in the bay during the time when the hooligan (=eulachon=candlefish=salvation fish) are running. this is hard to do, because the hooligan spawning run is short, only a week or two, and the timing varies from year to year—and it may be getting earlier than it was a few years ago.

When the hooligan come in, they mill about in the bay for a while, and that’s when the marine mammals enjoy a feast. Whales pass through, and seals hang out on a reef near Slate Cove. Steller’s sea lions stock up on the fatty little fish before heading out to their outer-coast rookeries for pupping and mating. On the rookeries, males don’t feed for several weeks, being busy defending harems and mating; females give birth and nurse the newborns, which costs them a lot of energy—so putting on some fat ahead of all that activity is essential. Years ago, when we studied the predators at hooligan runs, we counted over two hundred sea lions in the bay on some days, making a racket and leaving hooligan-grease slicks on the water.

Hooligan spawn in the lower reaches of the glacial rivers that enter the bay, and sometimes the seals and sea lions follow their prey up-river. It was quite a sight to watch a big bull sea lion humping hastily over the sand bars to reach deeper river waters and the up-running spawners.

thayers-gull-with-eulachon-by-bob-armstrong
A Thayer’s Gull with eulachon. Photo by Bob Armstrong

Birds come to the spawning run in droves. White clouds of over forty thousand gulls would be calling, chasing, pirating fish from each other, loafing on the sands. Eagles lined the river banks—we estimated that there could be a thousand or so. Local ravens and crows scavenged hooligan that were stranded by out-going tides and stashed their prey in the grass or fed them to chicks in the nest. Even dabbling ducks, such as mallards, chowed down moribund hooligan.

In some years, herring also spawn in the bay about the same time as the hooligan run. Herring spawn on the seaweeds along the rocky shores and attract hordes of egg-eating scoters and gulls, along with eagles interested in the fish themselves.

It was all very exciting! But, as a naturalist aboard the cruises this year, I had to tell folks to imagine all that predatory excitement. It seemed as if the hooligan run was over, although gulls still hung out along the edges of the river mouths. We heard rumors that the herring were in, and getting ready to spawn, but it didn’t seem to be happening just yet.

While it was a bit disappointing, perhaps, to miss the big show, I suspect that the folks on board were not unhappy at all. We saw a fine display of “pec-slapping” by humpback whales: whacking the water with powerful slaps of their long pectoral fins. The pectoral fins of humpbacks are longer, relative to body size, than those of other whales. Those mighty pecs are reportedly used to herd small fish, in fighting off attacks by orcas, and in making a swimming whale very maneuverable. They may also be used as some kind of display (still to be studied), and male humpbacks sometimes use them as props for their headstand posture while they sing during the mating season in winter.

Near Tee Harbor we chanced upon several orcas (=killer whales), splashing about and moving along the shores. There were several orcas, including one quite small one, mostly foraging independently, not in a close bunch. I guessed that these were likely to be the fish-eating ‘resident’ sort of orcas, probably after spring king salmon. Orcas had recently been seen near downtown in Gastineau Channel too, and we wondered what had lured them there.

We were treated to the delightful presence of several Dall’s porpoises, rushing hither and thither, sometimes riding our bow waves. A picturesque little flight of swans headed north, against a backdrop of the Chilkats. And I have not even mentioned the pigeon guillemots, marbled murrelets, loons, Arctic terns, scoters of two species, and clusters of Bonaparte’s gulls dipping down to the water surface to snatch some tiny prey.

Altogether, very satisfactory wildlife viewing, and fine days on the water!