Apex Predators and a Healthy Planet

Large predators often get a bad rap in terms of public outlook and opinion. Large predators in both marine and terrestrial environments has often been one of fear, misunderstanding, and misinformation. It was not until recently that public opinion on orcas began to change from one of a negative monstrous creatures to one of intelligent and social animals. Many people still fear apex predators, which are the highest carnivorous species in a food chain such as lions, sharks, orcas, or wolves. Apex predators are often targeted for unnecessary culls, relocations, and removals without consideration of the impacts this has for the lower end of the food chain. Bioaccumulation – that is, the accumulation of chemicals up a food chain – of heavy metals, harmful pollutants, and microplastics within our oceans is amplified within top predators, like orcas. This can lead to a secondary loss of apex predators from the top of the environment due to illness and mortality that can result from toxic contamination, which is often rooted in human activities.

Diagram: University of Walkato- www.sciencelearn.org.nz


Apex predators – top of the food chain!

The dynamics of apex predators is complicated. Did you know that the complexities of our kelp forests, recreational fishing successes, and beauty of our coastlines is deeply connected with the health of individual apex predators like orcas? Each group is directly related to one another.

Predators play an immense role in terms of top-down control, removing individual prey including sick prey, from populations, creating opportunities for more species to compete, and controlling trophic cascades, which can change the environment itself. Trophic cascades are a Domino-style effect, where one change leads to a series or cascade of changes in the environment.

Diagram: Wikipedia, https://en.wikipedia.org/wiki/Trophic_cascade

This diagram shows how the removal of an apex predator, like the wolf, has negative consequences down the food chain leading to an over-population of browsers like elk, who deplete primary sources of food like plants, shrubs and grasses.

Mesopredators- Stuck in the middle!

Within both temperate and tropical oceans, the presence of apex predators plays an important role in controlling secondary predator populations. A secondary predator, or mesopredator (meaning mid-ranking), is a species which preys upon lower trophic level organisms. Predators such as various Pacific salmon species and Pacific cod are important sources of food, transferring nutrients and energy from lower trophic level species, like small fish and krill, to high apex predators like orcas. Chinook salmon, which predate heavily on oil-rich fish such as eulachon and herring, are highly valuable to Southern Resident orcas who eat them. Negative effects within mesopredator populations can occur once apex predators are removed from the delicate equation. Mesopredator populations are controlled by apex predators who keep them in check and prevent them from eating too many individuals lower in the food chain, like herbivores. When an apex predator species is removed, that directly controls mesopredators populations, herbivore populations often become over-hunted as meso-populations explode in the newly available space.

The danger of losing an apex predator, within any environment, comes from mesopredators behaviours being unpredictable once the pressure from apex predators is removed. This can change things from nitrogen deposition in oceans to increasing clogging of waterways by algae, to decreasing seabird populations feeding on low trophic level animals. For example, corals are more likely to bleach and be blocked from sunlight due to algae growth when sharks are removed, due to mesopredators eating the cleaner fish entirely out of reefs. Lakes can become dead zones when mesopredators are not controlled by apex predators. They devour the algae-eating smaller fishes that control toxic algal blooms. Removal of jaguars increases deer populations which impact forests by over-browsing. Removal of wolves increases elk populations, which reduce foraging cover for birds and smaller animals.

So how does this play out close to home?

photo: Rachael Merrett

What happens if Southern Resident orcas go extinct?

With the recent announcement from the federal government that the endangered Southern Resident killer whales are at imminent threat of survival and recovery, decisions need to be made on best options to protect the 76 remaining individuals, now and into the future. The ecological impacts of whales should they go extinct, needs to be evaluated. Within Alaska, however, there have been studies of mammal-eating orcas akin to transient orcas found in the Georgia Strait. Downward trends in seal and sea lion populations in Alaska have been noted, with the main explanation likely due to decreasing fish stocks in the north. With decreasing mesopredators like the sea lions, the top predators, orcas, are turning towards unlikely prey. The orcas in Alaska have been observed predating on sea otter populations, and dramatically reducing them as the orcas attempt to adjust to the changing food availability in their region. Sea otters are keystone species, meaning they have an effect on the environment that is far greater than expected compared to their biomass. Sea otters control urchin populations, which if left unchecked, devastate coastal kelp forests. When orcas are left to starve, they indirectly create a vicious cycle of coastal instability, which can all be traced back to extreme harvesting within Alaskan fisheries.

An Unclear Future

Currently, Chinook salmon populations are largely impacted from unsustainable fisheries, open net-pen fish farming activities, polluted waters both in the ocean and spawning waterways, loss of habitat in their home streams, and the negative effects of climate change. Southern Resident killer whales depend on Chinook and have been heavily impacted by the depletion of their main food source, suffering from malnutrition and starvation. The federal government has announced a reduction of 25-35% in catch limits of Chinook along the coast of BC as well as some fishing area closures within the Strait of Juan de Fuca, the Gulf Islands, and portions of the Fraser River estuary. These measures alone will not be enough to bring back healthy Chinook populations and therefore the Southern Residents. Fisheries management needs to ensure that enough Chinook salmon are reaching the spawning grounds in order to rebuild the population. Habitat restoration of Chinook spawning grounds and migration corridors is essential to their survival and stock recovery. Chinook also need clean, healthy waters to live in, free of toxic contamination. A starving – and eventually disappearing killer whale population may negatively impact our coastline in ways we may not be able to predict. This is a tragedy, as it is human-caused threats that have pushed Southern Residents to the brink of extinction.

There are many examples of how impacting apex predators through their prey has often created long-lasting, negative effects. To aid in further action, we need to consider how our coast will change with the potential extirpation of our most iconic apex predator and how that could alter the entire food chain from the top down. Losing our killer whales is a potential environmental slippery slope and would be an immense cultural loss to our coastal communities. As threats to the orcas increase while the federal government continues to stall in taking immediate action to address these threats, our Southern Residents slide further towards extinction, and only then will we realize just how deep of a role our orcas play in the functioning of our coastal ecosystems.

~Written by Octavio Cruz


Learn More

Orca Awareness Month – join in the celebration!
Orca Protection – read more about orcas and GSA’s work to help protect them

3 thoughts on “Apex Predators and a Healthy Planet

  1. We are Ape X. This species of ape is heavily overpopulated and must learn to curb its numbers drastically before it overwhelms the ecology.

  2. The prioritization of cutting access to areas for fishermen is a very narrow focus to a broad spectrum problem. The reason given for the restrictions was to create a quiet area for whales. Unfortunately the most of the areas are still open to the commercial whale watching/harassing industry. Supposedly they are doing this in a kind nurturing way so as not to disturb the delicate biorhythms of the waters. There are only a few small areas that fishermen frequent, out of these larger closure areas, and the pods don’t seem to mind the boats, often travelling right through the boats. In all my years on the water I have never seen or heard of an Orca entangling in fishing lines and I have had them go right under my boat between the lines. A couple of times I have seen them gather at Beechy head to Secretary Island and stay most of the day, even though it is one of the more congested areas. The pods generally travel in an inverted v in and out of the straight. The first whales by are a long way off shore and the last are close in. We have always surmised that they travel out until they meet their prey in sufficient numbers and then travel east feeding and then back west as they run out of good hunting. If it had been stated as a means of saving salmon by cutting access to fishing areas, fine, that would make sense but it was promoted as creating a quiet area so one would assume that the whale watching industry would be shut out of that area as well. The fishing activity in most of the Otter point/East Point closure area is mostly for halibut, though Sherringham to Otter point was salmon fishing. Also the East Point closure is entirely unjustified. Some of the locals that didn’t like crowds will fish there, close to shore. Most of the salmon seem to congregate further into the bay and it is one of the most unpleasant fishing experiences of my long career trying to fish there. Fisheries has been aware of the link between chinook and whale for quite some time, at least 20 years, and has done nothing to accelerate the growth of the spring salmon. If it wasn’t for the American hatchery programs in Washington and Oregon, most fishermen realize there wouldn’t be enough chinook to allow fishing at all. Also a lot of the fish that are of Canadian origin are due to the efforts of sportsfishing groups raising funds and volunteers to run hatchery programs.
    Fisheries has also been aware for a long time that something is wrong in Georgia Straight with the whole ecological system, from the ground up. It is probably due to contaminants from humans flushing down the Fraser and killing the lower building blocks in the food chain. I think it would be a good idea to find out what is the actual problem but there doesn’t seem to be much political will to do this as it would probably create some major inconvenience to the general populace. More political points for whale hugging than hugging some microscopic plants and animals. Fisheries and the fishing population has been aware that for the last 30 years, salmon fry (and herring) must migrate quickly out of the inner waters or starve. This exposes them to more predation and increases the mortality rate. I would think that this(the whole inner waters dying scenario) might be a priority on the save the salmon/whale agenda, as each smolt has already run a gauntlet and it’s first semi-safe haven is a starvation zone and should be at the point of having it’s mortality rate decrease. The general size of salmon seems to be decreasing, which would lead most people to surmise that their food supply overall is diminishing. Salmon will feed on almost anything. I have found their bellies packed with the young of different rockfish, mostly the midwater variety, off Brooks peninsula. Squid, shrimp, krill and even an occasional hake add to the other than normally perceived salmon diet. Herring and needle fish are surely one of their main food along with squid and all of these, through my eyes, have been declining seriously over the last 40 years. Still the Government allows unbridled shoreline development and the herring fishery and dragging for “bottom fish” continues and there is no additional money available for marine biological research.
    Then there is the fact that even if the salmon do make it through all the perils at sea, find enough food to grow, and avoid the waiting fishermen, whales,and seals and arrive to spawn in their native streams, it is to less than ideal conditions. Human development again has made many streams unsuitable for optimum egg survival. There is a general malaise in forestry oversight. Second growth doesn’t seem to have the same restrictions as first growth did. It seems to me that there is a general attitude of “it’s second or third growth, who cares” even though it is still ground cover that is important to the runoff rates. Then there is the fact that a lot of the logging is on private land and is not controlled or so it seems. In the beginning forestry was pitched as a fifty year cycle. You take all the old growth over fifty years and then go back to the beginning and start again. So theoretically you could cut 2% a year. Unfortunately the growth rates they used were skewed so the forest were not producing as fast. Cut rates have gone up because of increased human growth and consumption and more efficient logging equipment. An acre of old growth held more wood than an acre of 50 year second growth so therefore more land needs to be denuded to meet demand. So this makes the Rivers uninhabitable for salmon spawning and nursery for their young. Second growth forests are coming down in our area at an alarming rate and no one seems to care. A lot of the land is then sold off for farms and development further destabilizing the forest base which the salmon need to spawn naturally. I could go on, agriculture needs the water to the point that, in some areas if all water permits were used to capacity, the river would be gone. Hydro electrical development, pollution from abandoned mines etc it all points to the need for more oversight of industry at a time when the Federal and Provincial Govt. has decreased spending in those areas.
    Human development is killing the environment and the political will for change is not there for serious change because it will hurt the economy. So if we still want to feel green about ourselves we get rid of plastic straws and ban fishing in a few areas. I think there are more cigarette filters making it down storm drains and have been for years but straws are a PR opportunity for some big corporations to show they are doing their part to save the world. Fishermen are a direct visible drain on the food supply of the Orca so it is good PR to impose more restrictions without spending too much money or effort. Going further with the real problems would start stepping on all sorts of jurisdictions, donors , toes etc. and generally create bad PR.
    I as a fisherman, admit that if you took us all off the water more salmon will be available for Orca however a new funding for salmon enhancement will need to be found. The natural River systems are compromised to the point that they are not viable in most cases for salmon. One thinks first of the big systems, which hold considerable spawning capacity but a large percentage of salmon spawning was done in smaller streams all along the coast. Overall I think most of the salmon runs from these has been diminished considerably.
    So with the multi faceted aspect to the whale starvation from lack of salmon I think you would need to add a bit more to your food pyramid. If you are looking for a quick fix, I don’t think keeping a few fishermen out of an area that wasn’t heavily fished anyway(because there wasn’t a lot of salmon there)excepting the Otter Point to Sherringham section, will be of any significant benefit. The best quick fix that I can think of is to act now and pressure DFO to step up chinook enhancement drastically, having something in place by this fall to gather more chinook eggs and building a system to protect them previous to release as smolts next spring. Now those smolts will need some food while they are in the ocean so get DFO to cut the roe herring fishery back so that more herring spawn. Then pressure DFO to do more research to find out why Georgia Straight (Salish Sea for the newbies)is not supporting salmon smolts (and possibly herring fry as well). You guys sound like you are getting quite a bit of support from different areas so maybe you might succeed where others have failed. Change the direction that DFO has been on for the last 40 years, involve all levels of government in restoring the salmon spawning habitat that is being destroyed (municipalities control the zoning and use of the land in their boundaries, province controls the water rights, forestry practices and land use outside of munipalities, feds control the ocean and all aspects of salmon, over-fishing, habitat destruction from draggers etc, etc.) If you start doing that you will more than likely get quite a bit of support from the salmon fishermen that are having restrictions put on right now, I know I will.
    Mark Perkins

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