From climate change to species extinctions, ecology has joined economics among the ranks of dismal sciences, and evolution may not be far behind. A short piece in this week’s edition of Science summarizes numerous studies across many species demonstrating the sinister impacts of fishing, and what it means for optimal management. It has been known for some time that, ecologically speaking, many fisheries are harvested unsustainably, leading to collapses. Economics exacerbate the problem. Since many fisheries lack property rights, no single company or country has a strong incentive to sacrifice harvests today for future benefits. Account for rapid evolution, and the picture becomes potentially bleaker. Life history theory predicts that high adult morality will select for smaller fish that reach maturity faster, which is exactly what studies find (see Table). What is surprising is the rapidity and magnitude of changes. Evolutionary changes in fish can impact the biological community through altered species interactions. More practically, smaller and younger fish can significantly change predictions about species recovery and yield.
| HARVEST-INDUCED EVOLUTIONARY CHANGES IN MARINE AND FRESHWATER FISH. | ||||
|---|---|---|---|---|
| Evolutionary Change | No. of species | No. of studies | Change % (n) | |
| Maturation at lower age | 6 | 10 | 23-24 (1) | |
| Maturation at smaller size | 7 | 13 | 20-33 (3) | |
| Lower PMRN midpoint | 5 | 10 | 3-49 (13) | |
| Reduced annual growth | 6 | 6 | 15-33 (3) | |
| Increased fecundity | 3 | 4 | 5-100 (3) | |
| Loss of genetic diversity | 3 | 3 | 21-22 (2) | |
Overfishing is a mature environmental problem. Large datasets over many years from fish harvests make it relatively easy to incorporate economics, ecological, and even evolutionary parameters into optimal management schemes. For less well documented and emerging environmental problems, the data are not as good, but that doesn’t mean the same cocktail of forces aren’t conspiring to degrade our biological resources.