We know that humans have an enormous impact on the world around us. Think of the skyline of New York. Now imagine how the island of Manhattan looked 300 years ago – that’s an amazing change entirely due to humans.
When an organism changes the environment around them, ecologists refer to it as an ecosystem engineer. Humans are easily called to mind as ecosystem engineers, but we aren’t the only ones. Beavers build dams to divert streams, the Indian Crested porcupine digs holes that persist for decades, and woodpeckers create habitats for many other bird species.
But while humans aren’t the only species that have changed the world around us, we’ve certainly done so at the largest scale. We’ve affected ecosystems in every corner of the world. Even the most remote areas – where humans have never visited – have been impacted by our use of pesticides and other pollutants.
Marine fish stocks have been particularly impacted. Currently, NOAA Fisheries estimates that more than 60 of the fish stocks under its management are overfished or overfishing is currently ongoing. Current fisheries research is able to give us an idea of what’s happening in the environment today, but how can we study the processes that got us here?
In a 2009 study, Loren McClenachan was able to document the long-term loss of large fish from the world oceans using an ingenious method. The study analyzed photographs of trophy fish taken from Key West over 50 years to measure their decline. Between 1956 and 2007, the study found that average trophy fish size declined from 43.9 lbs (19.9 kg) in 1956 to 5.1 lbs (2.3 kg) in 2007.
Check out more historic photos of trophy fish from the Florida Keys Public Library Flickr site.
This month, another study used a similar method to evaluate the recreational fisheries of California. The authors developed a 47 year database of trophy catches from all California ports and evaluated the changes in size and species caught.
The bad news. Of the 16 species they analyzed, 12 showed clear trends toward decreasing size and fishermen needed to travel farther offshore – clear evidence of overfishing.
The good news. Nine of the 12 overfished species seem to be getting better. The authors attribute this to new policies that were implemented by the State of California in 2001, around the time that these species began to recover.
This is especially relevant as we recently celebrated the 40th birthday of the Magnuson-Stevens Fishery Conservation and Management Act, the landmark legislation governing US fisheries management. While the act has received criticism for failing to prevent the collapse of some fisheries, this study represents is an important win for fisheries management.
The moral of this story: Take lots of photos. You never know when scientists will need them.
Feature image courtesy of Florida Keys Public Library