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.