About 91 per cent of halibut are right-eyed. “They start off as a larval fish with eyes on both sides of their head,” says Larry Hammell, “and then they go through a metamorphosis where one eye migrates over the top of their head so they have both eyes on one side and they swim on their sides.”
But, says the Professor in the Department of Health Management, when the eye is only partially migrated, or goes missing altogether, “The fish have higher mortality and much poorer growth.”
He can tell you that because his AVC team went into a hatchery in the spring of 2006 and micro-chipped just over 5,000 individual fish. “We monitored their eyes, their pigmentation, and a number of other factors.”
It’s one small part of Hammell’s efforts over the years to create an adaptable, ongoing, and standardized record of performance for farmed fish. “In the last five years we’ve also micro-chipped more than 54,000 salmon. We monitor individual measurements on weight and length, whether they had gill operculum deformities, or fin erosion. We look for disease or growth problems, and monitor every death. We weigh the salmon five times: once at the beginning, once two months later in the hatchery, once in the fall after they’re transferred to salt water, then the following spring and at harvest. Vaccine trials are often done at the same time.
“Now we’re trying to expand it even further. No one in the world has done this level of monitoring.
“I did a presentation once, and called it ‘Solving fish health problems one fish at a time,—yet as an epidemiologist I never really look at one fish. I’m trying to deal with whole populations. I prefer to call it
evidence-based research. I’m providing evidence to make better policy decisions, whether it’s at the farm, industry, or regulatory level. Often people are making decisions based on what they think should work, not what is proven to work.”
Hammell was born in Montreal, “but travelled around a lot because my father was in the military. I spent time in Germany, and in all parts of Canada.” Now, he spends a great deal of time on the road: in New Brunswick—in the heart of the region’s salmon farming area—as well as travelling everywhere from Chile to Paris in connection with his work.
“I knew I wanted to be a veterinarian by the time I was in high school, and I was interested in being a food animal practitioner. I realized that fish are one of the most efficient food proteins—and knew that’s where I wanted to be.”
As Director of AVC’s Centre for Aquatic Health Sciences, Hammell has focused much of his work on aspects of infectious salmon anaemia (ISA), a virus that has caused major problems for the finfish aquaculture industry. “We created a program to identify factors in husbandry,
environment, and the fish, which could contribute to ISA outbreaks. We conducted clinical field trials, and developed and evaluated surveillance programs. The program actually applies to all different kinds of diseases.”
He and his team are also looking at bacterial kidney disease (BKD). “Although ISA was the driving factor in our industry since 1997, over the past two years it has been less of a problem in this region, while BKD has caused more economic loss.
“One of the problems with many of the diseases of fish is that if you don’t treat a fish before it stops eating then you can’t treat that fish orally with medicated feed. So we look at antibiotic and oral treatments to see when they are most effective and if we’re using them properly, to minimize the amount of medication that has to be used.”
Hammell has also investigated the reliability of diagnostic tests used in surveillance programs and found that there were false positives in the results. Different ISA isolates are pathogenic while others are non-pathogenic, and the false positives tended to be the more non-pathogenic strain. “Before that we were managing them all as one result,” he says. “So now decisions are made based on seeing if the virus is one of the ones that’s going to be a bad one or less bad one. They are never good, just less bad. But that has helped us tremendously in identifying which fish should be depopulated because the only response to a virus is to try to remove fish before they become sick or before they infect other fish.
“We’re doing similar things with cod, but the results are still being compiled. We’re looking at things like water temperatures—perhaps the water temperature might be a degree warmer than it should be in the hatchery and that might increase the proportion of fish with spinal deformities. We need to quantify the impact such things have on production.
“In field research, there are many external influences that cannot be controlled. With imagination, you can apply epidemiology principles to the problem and get that much closer to a solution. Same with regulatory decisions. Our data allows industry and government agencies to really put a number on a problem, and it shows them that if this issue is costing millions of dollars, spending hundreds of thousands to identify a problem, or prevent it, is worth doing.
“But on a lot of disease outbreaks you don’t have three months’ notice. You have to respond quickly and report back quickly. Yet many of the rules for funding and approval aren’t set up to deal with this reality. I think they should make their rules apply to the situation, not the other way around. It’s emergency research just like emergency medicine, and I do it all the time.”
Looking to the future, Hammell sees the need for more health research related to new growing technologies and new species. “Hatcheries are better at growing their fish because the use of recirculated water is very efficient. It’s the way of the future. But there are many new health challenges we need to look at.”