Lobster and aquaculture: Studying interactions on Canada’s East Coast

Lobster and aquaculture: Studying interactions on Canada’s East Coast

There’s a real interest in the interaction
that an aquaculture farm plays in a marine environment. One of the things that it does is give structure
to a whole lot of other organisms. So what was once just plain water that things
would drift by, now is almost like an oasis. Most of the studies in the past have been
looking at the negative impact on the animals living in the sediments directly underneath
and surrounding the farm. But there’s also a potential that there’s
other more positive impacts of aquaculture because we’re essentially putting a bunch
of energy, a bunch of food into the system that the animals that live under and around
that farm can take advantage of and increase their fitness and their productivity. With this research, we’re looking at two main
things. One is the movement of crabs and lobsters
in and around aquaculture sites, and second is the condition of these animals. So to follow the crabs and lobsters, what
we’ve done, is we set out a whole big grid of hydrophones and we glue little sound emitters
onto the back of crabs and the lobsters. And then, the hydrophones can follow the movement
of the animals on the bottom by triangulation of the noise. Using this data, we can find out a lot about
the behaviour of lobsters and crabs. For example, were the individuals present
under the culture site? Did they exhibit foraging behaviour? Did they exhibit habitat-seeking behaviour? How large were their home ranges under the
culture site? “869 – they were all gone from there”
“They move” “So they’re moving around!” So the way we’re doing the second part of
this experiment is we’re looking at the lipids within the crabs and the lobsters that we’re
out sampling. The idea is that the food that’s being given
to the salmon, that we think that the lobsters and crabs are eating, has a different class
of lipids inside of it. And so, we should be able to follow those
lipids, those fats, inside the crabs and the lobsters. Lobster and crab samples were collected near
the farming site to check the lipid profiles of these individuals as well as in a reference
area to compare the numbers with data from an area free of influence from salmon feed. During dissection of the lobster, I remove
the hepatopancreas, which is similar to the liver in that it’s an accumulating organ. And this is the organ in which we think the
omega 3/omega 6 ratio signal will be the most off-balance, making it the best indicator
of the vegetable oil signature that we expect to see. We’re also conducting a lab experiment to
confirm how long animals have to be exposed to this feed before we detect a signal. What we’re doing in the lab is basically
calibration work. We have 60 lobsters, all in individual tanks,
and for about the past two months now, each lobster has been on a precision-calculated
diet ranging from between 0% and 100%. So at the end of the experiment, we’ll collect
samples of hemolymph, which is more or less the lobster equivalent of blood, and we’ll
send it off to the lab so they can do a detailed analysis of all fatty acids detected in the
hemolymph. And this helps us to make the connection between
the lobster’s lipid profile and the proportion of its diet coming from aquaculture feed. Once the method is calibrated, we’ll be
able to take any lobster out of its natural environment, do the same analysis and compare
the result with our lab findings. Then, by comparing the lipid profiles of lobsters
in different regions, we’ll get a better idea of how much of an influence aquaculture
feed has on bottom-dwelling invertebrates living near aquaculture sites. And so, this whole interaction is important
to understand because there’s a lot of interest on the part of the fishermen for example that
are fishing lobsters in the area, and whether there’s any benefits or problems that are
occurring because of that, but also to the farmers. I mean, they want to know what’s going on
around their farm so they can at least be benign and, possibly they can even enhance
some things that we want to enhance. I like the work that I do because the results from my research are used in the management of aquaculture. That’s to say that we’re now looking at aquaculture
in a much more holistic point of view than we used to in the past and that’s, to some
extend, based on the research that I’ve been doing for the past few years.

local_offerevent_note September 30, 2019

account_box Gilbert Heid


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