Claire Corlett

Fish Food, Fish Tanks, and More


Hi. This is Mr. Andersen and this is environmental
sciences video 20. It is on fishing. These are the famous Sri Lankan stilt fisherman
trying to eek out a living catching fish in the surf. They make most of their money actually on
tourists. But this is commercial fishing. We have been able to catch so many fish that
over fishing is a problem around our planet. What is fishing. It is not only capture of fish but seafood,
so lobsters and oysters and even kelp fall into this idea of fishing. What techniques? Well first of all where we are fishing is
important. Wild catch is when we are catching it in the
wild, in the oceans. Techniques we use are hand and spear. Angling is when you use a hook. We can also use nets and we have been using
trapping. We have been doing this for thousands of years
but not on the commercial scale that we are doing so now. And that has led to this problem over fishing. The classic example is the collapse of the
North Atlantic Cod fishing. The problem here is Tragedy of the Commons. Who owns that area? Nobody. So countries are all fishing it and as a result
we get this over fishing. Some people have put forward this idea of
aquaculture or farming fish. And that is a big portion of the fish that
we eat now. It is has pros. We are not doing wild catch, but there are
definitely some cons that go along with that. And so the key point with any type of fishing
is sustainable yield. How many fish can we catch so we keep that
population healthy. And regulations including quotas are going
to be a big part of the solution. So we have been fishing for hundreds of years,
thousands of years they have been catching by hand abalone and oysters. We can spear fish. We can use nets. We can do angling where we are using a hook. And we can use trapping. So we have done that all along but now we
are capturing fish at a much larger rate. So this would be fishing with giant nets in
Alaska. And these are these giant crab traps or crab
pots in Alaska. We can capture huge amounts of seafood and
as a result, we are dealing with the Tragedy of the Commons. If I am fishing in this small pond, I am okay
if I capture just a few fish and return some of those fish. But if some body fishes next to me and then
everybody fishes next to me, eventually that pond does not have a lot of fish in it. And we see this same thing in the ocean. And so the classic example is the collapse
of the North Atlantic cod stock. And so this is the amount of cod that we were
catching, but in the 1960s and 1970s we were catching so much cod that it eventually collapsed
and we had to have a moratorium, where you are not fishing cod in the hopes that they
will come back. Now if we look at the amount of fish the Canadians
were catching in the 1970s we see that it really did not increase that much. What is the big change? It is other countries that are fishing for
the cod. What countries? It is Russia, Germany, France. It is the US. And so what happened at that time is we had
such an increase in the amount of fishing that that whole fishery collapsed in on itself
to the point where they were not catching cod and they are going to have to wait for
that to come back again. So what is important then when we are maintaining
a fishery like this is the sustainable yield. So if you think of fish like any population
that grows, a population is going to do exponential growth and then logistic growth. It is eventually going to hit what is called
the carrying capacity. Now if we look at different levels along this
graph, at the beginning, what is the growth rate? Well you can see it is not increasing very
much, so it pretty much has no growth rate. As we go along this curve, at this point you
can see that the population is increasing dramatically, so there is going to be a huge
growth rate here, but once we hit that carrying capacity it levels off again. And so I am going to take this picture, put
it to the side and I am going to show you a different graph. Now I am going to take the population, which
is right here, I am going to move it down to the bottom and then we are going to graph
that growth rate. And so again it is low growth rate and the
beginning and the end and high growth rate in the middle. And so we get a graph that looks like this. It is not very interesting but it is incredibly
powerful. What we can do is use a graph like this to
figure out that sustainable yield, how many fish can we catch? And so let’s say for example that at this
population right here we decide to catch fish at a specific rate, right here. So that is matching the growth rate. And so what is going to happen to the population
over time? It is going to stay right there. If you ever catch fish at the same rate at
which this red line exists it will stay right there. The population will never change. Let’s say we catch less fish than that. At a lower growth rate, what is going to happen? Well this amount right here that we did not
catch will add to the population and so what is going to happen to the population? It is going to move to the right. We are going to have an increase in the amount
of fish in that area. Now likewise if we were to catch more than
that amount, so if we are catching more fish than the rate, what is going to happen? It is going to move to the left. And so with a curve like this anything below
the curve is going to move to the right. And anything above the curve is going to move
to the left. And so we can figure out what is the population,
what is the growth rate and we can figure out how many fish to catch. Now why did I color all of these ones down
here green? It is because anything below this line up
here is going to keep a sustainable yield of the fish. We might move down to the left and then move
up to the right again. And so what is the take home message? You want to be fishing when you have a high
population and you never want to exceed that rate or that line. And so let’s look at what has happened to
the planet. So if we look at global total fish harvest,
from 1950 to 2010 you can see that it has actually leveled off. So are we going to have problems into the
future? For sure. A lot of different fish stocks are seeing
this over fishing. But if we look at the total amount of seafood
that we are harvesting it continues to grow up. What is the difference? It is the arrival of aquaculture. It is the farming of these fish. Farming of salmon, or right here they are
farming catfish. So you can think of aquaculture like just
a farm for you fish. It is just like having a bunch of cattle in
an area. And so what are some good parts of this? We can have a greater density of fish. And we do not have to rely on this wild catch. Now what are some of the cons of this however? It is just like having a bunch of cattle in
an enclosed area. You are going to have a problem with waste. We are going to have to control algae for
example. We will use herbicides, maybe antibiotics. We could have a mixing of the native and non-native
fishes. A lot of people are putting forward GMO fish,
this idea that you could make salmon that can grow much faster. But once they escape they are going to compete
with the biodiversity of the fish. And so there are all of these problems. The key part is to remember, this whole idea
of sustainability. And so if we understand this curve, if we
are fishing up here, what you can do through regulations is you could figure out what is
the total allowable catch. How many fish could we catch? So let’s figure that out. This is the amount of fish. And then what you can do is you can quotas. We can use individual transferable quotas. So each little fisherman or each little fishery
gets a set amount of fish that they can catch. It is almost like staking a claim in mining. You can then start to invest in that fishing. And so did you learn the following? Could you pause the video at this point and
fill in all the blanks? Again, techniques wild catch could be hand
spear, angling, this would be netting or trapping. We can also do what is called aquaculture
where we are farming that fishing. The Tragedy of the Commons, the key point
or the solution is a sustainable yield. And then again, the best way to regulate fishing
is to figure out how many total can we catch and then give individual fisherman quotas
of the amount that they can catch. So that is fishing. And I hope that was helpful.

13 comments on “Fishing

  1. Hi bozeman i just want to say thanks for everything! You helped me so much at genetics and chemical equations and i just want to ask if you can make a video about comstellations😀😄😊

  2. i havent been eating any seafood in the past couple months and i feel like it's out of guilt, or maybe its one of those "if i dont eat any seafood then i wont think about how scary it would be to destroy ecosystems like that". anyway, great video

  3. How about starvation of the existing wild stock? Land and ocean balance might be out because of land agriculture and geo-engineering of land. How about compensating for it by taking care of the ocean pastures?

  4. I like how I got an ad disputing the claims that climate change is real, on an Environmental Science video l. XD

  5. Anyone here cares to explain the sustainable field at 4:26? I don't understand why "if fishers are placed on the red line" the population stays the same? Isn't the population supposed to decline if fishers reach that cap? Why is the sustainable field shaped as an arc?

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