Anyone who goes fishing probably has a fishy story about "the one that got away." It was
你要知道 它老大了，嗯 是很悲催。大鱼脱钩却十分重要。
this big, doncha know. Yah, that was a bummer… but it’s actually quite important that big
fish get away, both for fish and fishermen.
For most of the species that we fish, commercial and recreational fishermen are only allowed
to keep individuals above a minimum legal size. The idea behind these laws is to protect
juveniles so they can grow big enough to reproduce at least once before becoming our dinner.
In theory, that means there will always be enough fish for dinner tomorrow. And insuring
dinner for tomorrow is important enough that the British Parliament discussed protecting
young – that is, small – fish as early as 1376, and today it’s a common regulation for
Except, it doesn’t really work.
First, large individuals have the greatest number of successful offspring both because
bigger fish produce more eggs and because the eggs they produce ALSO contain a more
generous food supply for the baby fishies. So by removing the largest fish of a given
species, we severely decrease the population’s ability to replenish itself.
Second, if we only remove the largest fish, that means fish that are small for their age
– and thus smaller when they first reproduce – are more likely to live long enough to make
babies. So individuals with small-fish genes tend to stay in the water, reproduce, and
pass on their small-fish genes to new generations, while big fish and big-fish genes become rarer
and rarer. We’re basically breeding smaller fish, unintentionally – and it’s not a small
change. Size-selective fishing has caused the body mass of large commercial fish to
be cut in half over the last 40 years – let me say that again: heavily-fished fish are
now half the weight they used to be. Six-year-old haddock, for example, weigh 40% of what they
did in 1970. Imagine if full-grown men weighed 65-pounds!
Clearly, size-selective fishing means fewer and smaller fish in the water, which suggests
it’s not the best way to keep our fish supply stocked for future human generations. And
in fact, there’s a new idea called "balanced harvesting" ready to save the day. Instead
of reeling in all of the largest individuals, fishermen would catch a smaller number of
fish across a wider range of sizes, keeping the numbers and sizes of fish, well, balanced.
However, old habits die hard, and the use of size limits is deeply ingrained in our
collective fisheries management DNA. But sooner rather than later, we’ll have to accept that
it’s good to let some of the "big ones" get away, for only they can change the course