Fish are getting smaller on a large scale
- In the 1900s, 60 lb Atlantic cod were common. Now they’re a third this size
- Large groupers have been replaced by smaller snappers in the Florida Keys
- Fishermen consistently catching the giants are artificially skewing evolution towards smaller fish
Average fish sizes are getting smaller than they were just a century ago according to Eric P. Palkovacs, an Assistant Professor of Ecology and Evolutionary Biology at UCSC.
The main reason for this trend is the fact that commercial fishermen prefer the largest fish they can catch. Larger fish are worth disproportionately more than their smaller counterparts. It also doesn’t take as long to fill your quota with larger fish.
A grad student, Loren McClenachan, working on her doctoral thesis came across a stack of photos that were taken at the same Key West FL dock over the course of 50 years.
It’s common for deep-sea fishing charter boats to take group pictures of their catch. Comparing the catches from 1957 to 2007, the size difference is rather astounding as you can see below:
So what effect on the marine ecosystem does this have?
It’s not completely understood whether removing larger specimens from a species has any profound repercussions for either the species itself or the ecosystem as a whole. There is one example involving California sheephead. These fish prey on sea urchins, who in turn eat kelp. Larger sheephead are more adept at eating urchins than smaller ones, so when their population drops, sea urchin population increases. This has a negative effect on kelp forests, so one can see the ripple effect removing large fish can have on an ecosystem.LIST SEA AND OCEANS IN THE WORLD-