My name is Martin Krkosek. I'm currently a research associate at the School of Aquatic and Fishery Sciences at the University of Washington.
I've been working on the sea lice and salmon issue for just over eight years now. I received my doctorate from the University of Alberta for work that I did on this issue two and a half years ago. I've received numerous awards for that work, including a Governor General's gold medal. I've written approximately 20 papers on this topic over the years, including some of the most significant papers in the top journals that have received a large proportion of the media interest on this issue.
I'd like to thank you for having me here. It's an honour to come here and be able to communicate with you on this issue. I have prepared a briefing document for you. Unfortunately there's no French translation at the moment, but it should be forthcoming.
I agree with most of what my colleagues said in the previous hour. I'd say there's been a large focus on what we do not know about this issue and not so much of a focus on what we do know about this issue, and I'd like to speak to that a little bit.
Four key questions are at the heart of this issue, and I've been working on those questions. The first one is whether sea lice spread from salmon farms to wild salmon. Second, if they do, what's the impact on individual fish in terms of their behaviour and in terms of their survival? Third, if infestations are recurrent, what's the effect on the populations of wild salmon that are affected? Finally, if all this amounts to a problem, what are the management solutions that can be implemented, if any? I've been working on all these questions over the last eight years.
The first question is whether sea lice spread from salmon farms to wild salmon. I think there's an overwhelming amount of evidence to indicate that they do. Salmon farms are not the only source of sea lice in the environment; in fact, sea lice are a natural parasite, and they were here long before the salmon farms were here. What's different is the point in time when transmission happens and the magnitude of that transmission.
In the absence of salmon farms, when juvenile salmon leave the rivers and lakes and enter the nearshore marine environment, they do so in the spring, in March, April, May, and June. During this period there are very few natural hosts for sea lice in the nearshore environment. Most of the hosts are offshore; they're adult salmon, and they're out there on their feeding migration. It's not until summertime, in July or August, that large populations of wild salmon return to the coast and bring sea lice with them. This means that there's about a three- to four-month window between the time juvenile salmon enter the ocean and the time they first encounter sea lice. It's during this period that they're smallest and most vulnerable to infection.
There is a key difference when salmon farms are in the water. They provide a very large host population for sea lice during the winter, so when juvenile salmon enter the nearshore marine waters, they encounter salmon farms that host several million domesticated hosts in a region like the Broughton Archipelago, and those hosts support a large parasite population. When the juvenile salmon enter the ocean, they encounter those parasites, and they're poorly equipped to handle them. That is where the concern is: the effect of sea lice on the very small juvenile stages of salmon during their first few months of marine life.
What we've learned is that in areas without salmon farms, the natural prevalence of infection is about 5% on juvenile salmon during this stage of their life. In areas with salmon farms, the prevalence has a wide range, but it's generally higher than that, and in some instances can reach 90%, 95%, 100%. There is sometimes a very high mortality associated with very high infestations.
You don't have to be a mathematician to figure it out. I've been in the field studying this for about six months of the year for the last eight years, and you can see it happening.
The effect of the sea lice on the juvenile salmon can be direct mortality. One adult louse on the smallest salmon is lethal. The more common situation is two or three lice on a medium-sized juvenile salmon, and there, the interactions are much more subtle. There will more likely be sublethal effects that make the fish more prone to, primarily, predators or diseases. It's probably there that mortality happens. The lice change the behaviour of the juvenile salmon in ways that make them more prone to predators. So in reality, in the ocean, long before a louse would kill a fish, a predator would kill that fish because of the infection that was there in the first place.
There was a period of about five years when we had recurrent, very large, sea lice infestations of juvenile salmon in the Broughton Archipelago. Those were the infestations that triggered this issue. During that time, we observed very high mortality among the juvenile salmon. Using standard fisheries and epidemiological tools, we were able to isolate the effect of sea lice from numerous other confounding factors and identified that as a major factor affecting the productivity of wild pink salmon populations in the Broughton Archipelago. During that period of infestation, the productivity was negatively affected so much that the populations were at risk of local extinction.
Since then, we've seen major changes in management. It has moved from a focus on protecting the productivity of the farms to a focus on protecting wild salmon from sea lice. It's a coordinated area management plan; most of this work is still focused on the Broughton Archipelago.
During the spring, when the juvenile salmon migrate out to sea, about half the farms are emptied or are treated with chemical parasiticides to bring the lice numbers down as low as possible during that out-migration season. Preliminary results indicate that this management plan is working. The number of lice on the farms and on the wild salmon have declined dramatically in recent years.
As scientists, with the models we're using, we would predict that this should result in the recovery of those populations. The predictions we made in the past, when we were expecting to see local extinction because of sea lice infestations, now no longer hold. The sea lice infestations have been largely eliminated from the Broughton Archipelago because of this change in management.
The change in management is largely reliant on the use of chemical parasiticides, and this is a situation that is, I think, a little bit tenuous. First, one reason is that the chemicals could have adverse effects on the aquatic ecosystem. This is toxic to crustaceans. That includes shrimp, prawns, crab, and the copepods in the zooplankton that are a key component of the food web. To date, no one has done any work to evaluate what the ecological effects of these chemicals are.
Another tenuous aspect of the use of these chemicals is the possibility that sea lice will evolve resistance to these chemicals. This is an outcome that has already happened in New Brunswick, Norway, and Chile. Based on our experiences in these other areas, we would expect a similar outcome in British Columbia, although that outcome may be slower.
However, this last winter, we had our first evidence that Slice treatment--emamectin benzoate, known as Slice, which is what is used--failed in one area of British Columbia, Nootka Sound, and this suggests that sea lice may already be evolving resistance to the chemicals used in British Columbia.
However, it's not the only explanation. Other explanations are also possible, such as that the dosage was incorrect or that the salmon were not feeding well and did not receive the correct dosage. No one has done the work yet to determine whether sea lice have evolved chemical resistance in British Columbia.
So far, most of the work in British Columbia has been focused on pink salmon in the Broughton Archipelago, and that's where we have made our largest advances in understanding the science of sea lice and salmon and in understanding the effectiveness of new management.
I would like to point out, though, that in all major salmon-farming regions of British Columbia, primarily the Discovery Islands, the Broughton Archipelago, and Clayoquot Sound, we have the same patterns of sea lice infestation and population decline of wild salmon. This includes pink salmon, chum salmon, coho salmon, chinook salmon, and sockeye salmon.
It's likely that the problems we've seen in the Broughton Archipelago are widespread. However, it's also likely that there are management solutions that can deal with this. Those management solutions depend on the long-term sustainability of the chemicals that are used to control sea lice on farms.
