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humans have been eating seafood for
thousands of years and in many ways it's
awesome animals like fish don't produce
as many greenhouse gases as say cattle
do and also they're just plain delicious
sorry non fish eaters unfortunately
getting this kind of high-quality
protein isn't always easy
some animals don't grow fast enough to
be a sustainable food source and others
taste pretty gross
for at least part of the year so to
solve these problems
scientists have turned to a may be
unexpected field genetics by carefully
breeding or modifying aquatic animals
they've found ways to get us more
efficient responsible and delicious
meals and if you're a seafood fan the
odds are good that you've encountered at
least one of these three examples on
your plate our first example is catfish
every year the world consumes hundreds
of millions of kilograms of these fish
but the animals only grow so fast so
since the 1960's the catfish industry
has been collaborating with researchers
to get those crispy fillets to our
plates more sustainably one way they've
been doing this is by crossbreeding
species of catfish trying to find a
hybrid with the most commercially
desirable traits and they found one it's
a cross between a female channel catfish
and a male blue catfish and
appropriately it's called the channel
blue this hybrid is bigger and is better
at converting food to body weight than
either of its parent species it also has
a higher survival rate and improved
disease resistance the verdict is still
out on how and why this happens but the
hypothesis is that the channel blue just
ended up with a really useful
combination of genes unfortunately
though you can't just throw channel and
blue catfish in a pool and wait for them
to produce tasty offspring these species
rarely mate with each other in the wild
to get a channel blue you have to do
things like treat female channel catfish
with hormones to induce ovulation then
mix in sperm from male blue catfish
don't get me wrong this method is
effective
in 2011 about 20% of the catfish
harvested were channel blues but it's
not always successful so the next step
for researchers is to find a way to
breed these species more efficiently
among other things some scientists are
trying to do this by mapping the genes
of both parent species they're hoping to
find genetic markers that could someday
help channel and blue catfish mate more
readily so maybe we'll be seeing more of
these hybrids soon
catfish isn't the only seafood we're
interested in improving though another
example is oysters oysters aren't as
widely consumed as catfish but people do
love slurping them down and the demand
for them is growing the problem is wild
oysters don't always contain a lot of
good meat during spawning season they're
smaller with mushy runny flesh and their
gonads take up around 40 percent of
their body mass for real some could call
them the ballsiest creatures on earth
that just doesn't sound appetizing so
scientists found a workaround
they made commercial oysters sterile
they did it by engineering triploid
oysters these are a stir with three sets
of chromosomes one more than normal this
odd number messes with their ability to
produce sperm and egg cells which means
the animals have more energy to devote
to growing fatter and tastier scientists
started experimenting with triploid
oysters in the 1970s and 80s but while
they did achieve some victories their
methods weren't good enough to go widely
commercial they were creating triploids
by applying chemicals to recently
fertilized eggs and that wasn't always
successful and didn't go over well with
the public so in 1993 scientists tried a
modified approach first they combed
through the triploid oysters from
previous experiments and found the rare
exceptions that were somehow still
fertile then they took the oysters eggs
and injected them with sperm cells
containing one more set of chromosomes
ultimately this led to the creation of a
tetraploid oyster one that had four sets
of chromosomes and when that animal
mated with a normal a stir with two sets
of chromosomes it produced sterile
triploid offspring today this idea is
what leads to those fat juicy oysters
you order at restaurants so not only is
the
dude fancy but the science is - now as
weird as they might be neither hybrid
catfish nor triploid oysters are
considered genetically modified because
they weren't engineered by directly
transferring specific deliberately
chosen genes this last example though is
a proper GMO in fact it's the first
truly GMO animal to hit the market for
human consumption it's called the aqua
advantage salmon
unlike wild oysters and catfish wild
atlantic salmon are already pretty good
at converting food into body mass but
scientists wanted to create an even more
efficient version because like have you
tasted salmon don't you want more of
that
to modify this animal researchers took
fertilized eggs from wild Atlantic
salmon and inserted two new components
the growth hormone gene from a chinook
salmon and a short bit of DNA called a
promoter from a fish called an ocean
pout the chinook gene was chosen because
compared to Atlantic salmon these salmon
tend to grow more from the same amounts
of food and the ocean pout promoter was
chosen because it allows the pout to
grow year-round as opposed to the
Atlantic salmon which only grows during
certain times these researchers
essentially took two beneficial traits
and threw them into one organism they
also made the salmon triploid and
sterile to make sure they could never
mate with wild salmon even if they
somehow escaped captivity the aqua
advantage fish was tested for safety and
approved for sales in early 2019 and
compared to its wild counterparts it
grows faster and reaches the same size
with 25% less food so more salmon for us
projects like these are major ways we
can continue eating seafood without
taking as much of a toll on wild
populations and habitats they won't
solve all of our problems but these
clever creative ideas do have the
potential to really improve
sustainability if you want to learn more
about how scientists are improving
agriculture you can check out the series
curious minds global food supply over on
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