Chapter 17
Fisheries oceanography
Our goal here is to provide an initial look at the mental machinery of fishery
biologists. Studies of fisheries are a major part of the practical side of ocean science;
so all oceanographers should know something of the ideas in this neighboring field.
We will consider the population units (“stocks”) that fishery biologists try to discern
and evaluate; review the simplest models of stock dynamics and the interaction of
fishery production with economics; and briefly examine the overall status of world
fisheries. We can only touch the surface of this deep, complex subject.
(^) To understand the data supplied in what follows, you must have mental pictures of a
metric tonne (SI unit symbol is “t”) and of a million metric tonnes (Mt) of fish, crabs,
or squid. A million tonnes is also 10^12 grams (1 teragram = 1 Mt), if that’s useful. One
metric tonne is the mass of water it would take to fill a cubical box with sides of 1 m.
That is about the volume surrounded by a small desk. A metric tonne of fish, then, is
an amount that might all be tossed into one large fish box and hoisted from a fishing
boat onto a processing plant dock. It is an amount you can visualize. One Mt of fish
can be visualized in a similar way. It is about the amount of fish it would take to fill a
box sitting over two, side-by-side soccer fields (each 100 × 50 m) to a height of 100
m. That amount of fish would fill one of the very largest international soccer stadia or
the Los Angeles Memorial Coliseum to the top row of seats. In the late 1990s, the
world catch of wild fish and other marine animals peaked at about 90 Mt, about 90
stadia full of fish, crabs, shrimp, oysters, and squid. Picture a row of these huge fish
hoppers, side by side for about 18 km. It is not an inconceivable amount, just a great
deal. The total production of all “fish” is rapidly increasing due to advancing
mariculture and aquaculture, which are not always well separated in available data.
They bring the sum up to ∼160 Mt.
Stocks or “Unit” Stocks
(^) Some critics (e.g. Gauldie 1991) have claimed that the notion of stocks is outdated;
that the impact on all stocks of harvesting one of them makes separating and
distinguishing them risky; and that distinguishing stocks without considering their
interaction with the economics of fisheries isolates them in an undesirable way. On