Florida manatee Credit: Carol Grant/Getty Images via Scientific American

When we wrote about “sea-cows” before here it was in a post about water hyacinth. Now Scientific American is sharing some good news on the species that we weren’t aware about, with great increases in their population’s numbers. Sean Carroll reports:

Good news seems to be rare these days, and good news about the environment even rarer.

But in January this year, after fifty years on the endangered species list, the US Fish and Wildlife Service (FWS) proposed to remove the manatee as its numbers in Florida have increased 400% in the past 25 years. And just this month, the FWS proposed to delist the Greater Yellowstone grizzly population as the number of bears has increased from 136 in 1975 to about 700 today.

The encouraging stories are not limited to such famous animals. You would not have seen any headlines, but over the past 15 years, dozens of handsome sea creatures such as the monkfish, lingcod, and something called the gag grouper have rebounded from depleted numbers, along with certain stocks of more familiar menu items such as coho salmon, haddock, snow crab, and swordfish.

How did all of this happen?

The answer is regulation – of two kinds.

The first kind was human regulation. We gave these animals a chance by regulating their hunting or fishing through the Endangered Species Act [1973], the Marine Mammal Protection Act [1972], and the Magnuson-Stevens Fishery Conservation and Management Act [1976].

The second kind of regulation is biological. As a rule, nature is remarkably resilient and productive. And I do mean rule. The ability of species to rebound from very low numbers reflects a fundamental biological rule about how populations are regulated in nature. When populations are small and resources abundant, populations can multiply at near maximal rates.

Populations grow when the birth rate exceeds the death rate, so when human-caused mortality is restricted or eliminated, the rebound can be impressive.

For example, when the American side of the Georges Bank fishery was closed in 1994 due to overfishing, haddock and yellow flounder numbers tripled and quintupled in just five years, while large scallops increased 15-fold.

The closure of fisheries and the regulation of catch limits are usually unpopular and understandably so. But we ignore biological rules and resist such regulation at our peril.  The United States commercial and recreational fisheries contribute $200 billion to the economy and support 1.7 million jobs. While overfishing of some stocks continues, and others remain to be rebuilt, the US is arguably a global leader in the sustainable management of fisheries.

Continue reading the article here.