It is almost like clock-work, the dance of precious life that regularly occurs in places such as Placentia Bay. During the summer, schools of capelin swim into Placentia Bay where many of them, the males at least, are destined to end their days. However, life and death are intimately twined and so, at the same time, the capelin are also turning the key to not only ensure life for future capelin. Whether known as a keystone species, a lynchpin, or cornerstone, these slender, silvery fish are a paradox. However small and seemingly insignificant, without them, many of the animals who are part of Placentia Bay would face an uncertain future. Capelin reflect a small yet ever so robust element in the diversity of life of the bay. And it is all about diversity.
Thinking About Diversity
The idea of biological diversity or simply, biodiversity, is sweeping in nature and is applicable at different levels. So, it is possible to think of species or “organismal diversity” as the variety of particular species in a region. Finally, “ecosystem diversity” refers to the number and variety of ecosystems, a measure that can be complicated by the fact that the boundaries of ecosystems are rarely defined. Ecosystem diversity may be a reflection of the variety of ecosystems within a region or a single ecosystem. Single ecosystems with species native to that particular region or “endemic species” also add to global diversity.
In Placentia Bay, species come in all shapes and sizes, all with their own unique characteristics. And while the Bay may look immense and vacant, the wind often stirring its surface, it is teeming with life of all sorts, from microscopic algae to gargantuan blue whales whiling away in the bay. Scientists have given us a sense of the different animals, including the birds, marine mammals, fish and shellfish, all of who belong to the bay. Other species merely stop by for a visit. Amongst these creatures are countless insects, invertebrates and other small and microscopic species—some yet to be discovered—who make a home for themselves in Placentia Bay. Each and every one, through their interactions, is somehow interconnected by their common pursuit of life, a reflection of the diversity that abounds in the bay.
At the same time, biodiversity is characterised by “genetic diversity” or the variety of genes that form our collective genetic blueprints. This is the quality that translates into the variability that characterises a species—eye colour, the speed of maturity, nature of the feathers, resistance to disease, and countless other relevant attributes. This aspect of diversity helps to determine how a plant or animal will interact with one another and with their local environmental conditions.
Finally, think of “ecosystem diversity.” Similar to the various species, ecosystems come in a wide assortment of types, everything including estuaries, marshes, lagoons, or shoreline ecosystems, all of which can be found in Placentia Bay. We can think of the various ecosystems in Placentia Bay where myriad interacting organisms, large and small, live in accordance with non-living elements of their environment. It may be the barachoix estuaries in places such as Ship Cove or Big Barasway. Elsewhere in Placentia Bay, eelgrass meadows offer a haven for varied organisms that help to nurture the biodiversity of the bay. And there is no better species to exemplify the species richness of the bay than the capelin, our tiny but unsung hero. They occupy a unique place in the diversity of animals who spend time in the bay.
Capelin - Our Unsung Heroes
Despite the significant role they play in Placentia Bay, capelin are relatively small, with the males ranging up to a maximum length of 20 cm while the females can grow to about 25cm. These cold-water fish spend much of their time in the open water of the sub-Arctic in both the Atlantic and Pacific oceans. Around Newfoundland, scientists believe there to be four stocks, one of which occupies an area that includes Placentia Bay. Capelin generally reach maturity at three to four years of age and while alive, the health and well-being of many other fish and mammals hinge on their behaviour in places like Placentia Bay.
Capelin are closely bound to a wide array of species, including ourselves. Belonging to the family osmeridae, these smelts originated in the North Pacific, only migrating to the North Atlantic over the past few million years. Known as planktivores, the capelin feed on a smorgasbord of food, such as planktonic crustaceans which simply drift in the sea, copepods (small crustaceans), euphausiids, better known as krill, amphipods (crustaceans lacking a carapace), marine worms, and small fishes. Quite a sizeable menu.
Despite their wide-ranging appetites, Calanus finmarchicus, a type of copepod, are one of favoured prey species of capelin. The key quality about the capelin is that they occupy and dominate a vital spot in the food chain or trophic level wherein, they prey on particular species and then, they in turn become the prey for other fish and marine mammals. So without them, a link in the food chain is missing.
Capelin are a particularly valuable fish by virtue of their nature. They are an “oily fish,” rich in lipids which are essential “energy food.” Their place in the food chain is a reflection of the vitality of the bay, every year touching off a unique dance amongst the many participating species.
Things get moving around March and April. This is when capelin begin to swim inshore to spawn on beaches such as those at Point Verde and Gooseberry Cove on the Cape Shore of the Avalon peninsula. Not all capelin spawn on beaches. Some of the capelin stocks around Newfoundland actually do spawn offshore, in particular, on the “tail” of the Grand Banks (NAFO 3NO). And some capelin have been known to spawn in subtidal areas that were adjacent to spawning beaches where the water temperatures had been too warm. In one location (Bellevue Beach), the scientists found that the capelin spawned on the beach until the water reached an upper range for spawning, at which time, spawning took place along the bottom, something that is known as demersal spawning. While capelin are Arctic-Boreal species and have evolved to survive and thrive in polar temperatures, they do require higher temperatures for successful reproduction. So, temperature of the prospective beach appears to be a factor.
When the capelin do come ashore to spawn, it is an activity accompanied by a supreme and yet expected sacrifice in that the females are likely the only ones who will survive the encounter. It is the way things work. Capelin spawning is an event that has changed since the early 1990s. Nowadays, the capelin spawning tends to occur around a few weeks to a month later than it did prior to the 1990s.
During the early portion of the 1990s, the capelin experienced a major biomass (or the total number of organisms in a particular area), decline, one from which the species has yet to recover. As a hint of the substantial change, in the NAFO SA2 + Divisions 3KL, in 1990, the capelin biomass plummeted from an estimated 6.9 million tonnes in 1990 to around 100,000 tonnes in the following spring. This substantial drop coincided with a particularly cold period and at the time, capelin apparently moved south and east to warmer waters where zooplankton may have been more available. This remained the situation from 1991 to 1994.
While the capelin stock levels had returned to more moderate levels from 2013 to 2015, they have since returned to those more typical of post-1991 period. It is not yet exactly clear what has caused the change. Although, the general belief holds that feeding conditions in the spring and fall and the relationship with the seasonal sea-ice retreat have had a role to play.
According to some scientists, the late spawning time for the capelin during the early 1990s was tied to the smaller size of the fish and below normal sea temperatures. The lower temperature of the water delayed the production of zooplankton. And like a domino effect, this, in turn, set everything back, including the maturation of the capelin, their migration, and finally their spawning. Other scientists have pointed to the timing of the seasonal sea-ice retreat which was taking place later than it had customarily been occurring. These result of these changes then rippled through the system, eventually altering the spawning time for the capelin. How it appeared to function was something like this—the retreat of the seasonal sea-ice in the spring would set off a bloom of phytoplankton which, in turn would feed zooplankton. So, the various forces that interact and affect the seasonal sea ice drive both the biomass and timing of the capelin spawning.
Calamus finmarchicus, a species of zooplankton feed heavily on the spring phytoplankton. And then, helping to close the food chain, Calamus finmarchicus just so happen to be one of the favourite foods of capelin. And if this is in any way delayed, it would alter the dynamics of the system, meaning capelin would only be ready to spawn later than usual. Capelin are particularly sensitive to environmental changes and can even function as a “canary,” providing an alert to temperature shifts.
Regardless of how, when, where or why, the capelin spawning has remained a special time for many people around Newfoundland. For decades, it is a tradition that has been passed on ever so gently through the years, from grandparent to grandchild. That it continues to happen is really the primary concern, a way of life that somehow assures us that maybe some things never change. Everyone eagerly awaits the time when the capelin will “roll,” likely a reference to the tendency of the fish, caught in the rolling waves, to wash ashore, their slithery bodies racing in and out with the swish and swash of the waves. It is now an iconic scene. All eyes are fixed on the oncoming waves, almost entranced. There is an unmistakable energy in the air. People of all ages with nets of every description on hand can be seen arrayed along the beach to catch the capelin. Some Newfoundlanders have been following this tradition for as long as they can remember. It is an unspoken union with the sea that, every year, pulls them back to the shore.
While people are intent on gathering the capelin into their nets, other creatures who grace the underwater thoroughfares of the bay are equally drawn by this miniscule fish. All of the whales who spend time in Placentia Bay—humpback, fin, minke, pilot, and sei—dine on capelin for part of their sustenance. The harbour porpoise and the harp seal are also known to rely in part on this tiny but indispensable species. And one species has remained as closely connected to capelin as it has to the people of Newfoundland—cod. Their lives follow a similar path and where one is found, the other is not far behind. Other species such as American plaice also depend on this humble fish for at least part of their sustenance.
Although, of all the species bound to capelin, humpback whales possess the most memorable place in our minds, their massive bodies leaping into the air with what always appears as nothing less than a jubilant celebration of life. Measuring around 12 to 16 metres in length and weighing in at 25-30 metric tons, these grand creatures of the sea begin to arrive in the waters of Newfoundland in April. And they are hungry. The goal will be to replenish and build their blubber which will be needed on their return migration to the subtropical and tropical regions where they breed. These gentle giants offer one of the most fascinating and mesmerising acrobatic spectacles when they are feeding.
While feeding, they have several tricks up their sleeves. One method is to simply charge into an unsuspecting school of capelin with their mouths open. But sometimes a little deception helps. One ingenious method that humpbacks use is to corral the schools of capelin. When encircling the capelin, they release air underwater to form numerous bubbles in order to create what amounts to a “bubble-net.” Afterwards, each of the whales take turns lunging towards the bubble structure, and open-mouthed, they devour thousands of capelin.
Awaiting a Smorgasbord
It is not difficult to appreciate the central role of capelin when looking at the array of species that rely on it as a food source. These small fish have a big impact. Much like the humpback whale, the fin, sei and minke whales also feed on the capelin. After the blue whale, fin whales are the second largest and one of the swiftest animals in the ocean. Although, unlike the humpback, these sleek whales tend to remain offshore. Likewise, the Sei whale also predominantly remains offshore and after the blue and the fin whales, it is longest. The smallest of the baleen whales, the minke whale is commonly seen in close proximity to the humpback whales.
Another marine mammal who awaits the arrival on the capelin are the harp seals. Although harp seals spend the majority of their lives at sea, they gravitate to the southern reaches of their customary territory around late February to mid-March in order to give birth. Feeding their pups is an all-consuming period, a time when they rely heavily on fish such as the capelin. Seals are fairly respectable divers, descending as deep as 370 m for around 16 minutes. They likely use their highly sensitive vibrissae or whiskers to detect the location of schools of capelin. They have not got much time to lose. The idea is to make certain that pup will be ready after 12 or so days when it will be weaned and the mother prepared to mate again.
Similarly, harbour porpoises (Phocoena phocoena) include capelin in their diet. These small and sedate odontocetes or toothed whales tend to be found over the continental shelves of the northern hemisphere and are the smallest ones in Atlantic Canada. Those who are found in Placentia Bay are part of the Newfoundland/Labrador subpopulation, the others being Gulf of Maine/Bay of Fundy, Gulf of St. Lawrence, and West Greenland. Being small and having limited ability to store energy, the harbour porpoises must eat frequently. Although the harbour porpoises are usually found feeding alone, when together, they use the seafloor as a way to corral the the capelin. Harbour porpoises have also been known to fish closely together, collectively herding the capelin to the surface where they can be eaten. It pays to work together sometimes.
Above is a Northern Gannett (Source Wikipedia)
Amongst seabirds, gannets make up another species who await the arrival of the capelin. Gannets are renowned for their ability to execute breathtaking dives into the deep waters further off shore. Sometimes, several may be flying overhead and suddenly, they begin dropping, one after the other. While it is with a mixture of awe and anxiety to watch them, the thought that one of them is sure to collide with another, gannets are too skilled to allow such a misadventure to occur. Once underwater, certain longer dives will witness the gannets propelling themselves in a type of “plunge-pursuit,” their wings being used to help them to manoeuvre towards schools of capelin. Afterwards, they rise back to the surface with their prize.
Meanwhile, like the whales and other marine mammals who rely on capelin to arrive, gulls similarly await their movement inshore. And when it happens, they will be never far behind fretting and fussing about at the water surface and claiming a cut of this waterborne treasure. Whether it happens to be humpback whales netting the capelin from below or people doing so from above, a cloud of gulls will almost always be overhead, darting and diving, determined to find a morsel or two. During the early 1990s when the arrival of the capelin had been delayed, scientists working on Great Island, NL, noted how gulls began to prey on Leache’s storm-petrels. The behaviour decreased significantly when, several weeks later than had been the norm, the capelin moved inshore. Such behaviour points to the important role that these silvern-like fish play in food webs that characterise places such as Placentia Bay.
Key Role of the Cod
Of all the species whose livelihoods are closely connected to the capelin, none seem to be as harmonised with this small titan as the cod. The two engage in one of those water bourne dances that forever unites predator and prey. As long as anyone can remember, the cod would migrate inshore at a time that coincided with the capelin spawning migration. Once the two met, the cod would feed voraciously on the capelin both during and following capelin spawning.
Throughout the early years of the 1990s, climatic changes led to particularly cold oceanic conditions that were the “final straw” for the cod. And after decades of over-fishing, their numbers plummeted. Along with the cod, like a tragic accompaniment, a similar fate befell the capelin.
After the ups and downs that followed the period when the brakes were violently and unexpectedly applied to the cod fishery, thus yielding the subsequent moratoriums, cod remains in a sensitive place. Still, the largest spawning stock of Atlantic cod in the NW Atlantic occurs in Placentia Bay. The main spawning areas for cod in Placentia Bay are close to the shore and also on Burgeo Bank. St. Pierre Bank, and the Halibut Channel.
Fisheries and Oceans Canada reported that landings for both Canada and France (St. Pierre & Miquelon) have been substantially below the Total Allowable Catch (TAC ) since the 2009/10 season. Although the biomass index for 3Ps division values for post-moratorium to 2004 were higher than those in early 1990s, recent biomass estimates have been low.
While the highly variable diet of cod was once dominated by fish such as the capelin, these days, their food source is dominated by sandlance and crabs, particularly Snow crab. Given that the capelin appears to have not yet recovered from their fate in the 1990s, it is not surprising that the cod have had to alter their diet. And albeit a viable alternative, it is likely that an invertebrate-dominated diet would not be as nourishing as one dominated by fish.
Scientists have also noted high mortality rates for cod in the 5-10 age range, a fate that includes deaths as a result of fishing. However, it is very high considering the TAC had not been reached for several years. Why the mortality for this age range has increased and why is unknown. Is it perhaps due to their lower level of nutrition due to the loss of the capelin? The cod also appear to be displaying changes in terms of their “length-at-age.” This refers to an x-y graph plotting length on the y-axis and age on the x-axis. Therefore, with a declining length-to-age, it refers to length declining with increasing age. After declining from the early 1980s to mid-1990s and then increasing from the mid-1990s into the mid-2000s, in recent years, the length-to-age has been lower. From 2013 to 2016, it was the lowest has been since being recorded.
Much like the length-to-age measure, the “condition” factor of the cod has also diminished. This is a measure of the fish weight relative to its length and is regarded as a substitute for “energy reserves.” This measure generally declines during the winter and early spring. And similar to the length-to-age measure, that for the condition also improved during the period from 2008 to 2013 and again, from 2014 to 2016, it declined to the lowest level it has been since first being measured.
Despite the challenges that some species have faced, given the losses during the 1990s, capelin remain at the heart of the web of connections that characterise one of the central facets of Placentia Bay that is tied to its ecology. However small, their lives free and fleeting, capelin are a pivotal element in the wide diversity of plants and animals that collectively add a lustre of uniqueness to the bay. Such qualities lend to the spirit of the bay. And in much the same manner, there are other elements of the bay that likewise enhance its spirit.