by Katrina Munsterman, Ph.D. student in the Coastal Ecology and Conservation Lab in EEB
If you build it, they will come. It all seems so simple. A few years ago, I gifted my dad a wooden bird house, a bag of bird seed, and The Sibley Guide to Birds. Within a few days of placing the bird house in his yard in the Pacific Northwest, he had the pleasure of frequent visits by finches, thrushes and jays.
It makes sense that creating new habitat leads to more organisms using the habitat that provides shelter and food. What is not clear is whether new habitat simply attracts animals from other areas, or if it helps to add or produce new animals in an area. This puzzle, known as the attraction-production debate, is a hot topic for the use of artificial reefs in fisheries management.
Some fisheries scientists believe that adding artificial reefs simply attracts fishes from surrounding areas. Because groups of fish are often easier to catch, this can lead to overfishing. Other fisheries scientists believe that adding new habitats helps fish grow and produce more fish (also known as fish production) by increasing access to shelter and food. Solving this puzzle is especially important for tropical reef fisheries that provide food to over two billion people globally.
In our lab, we build artificial reefs in shallow seagrass fields in The Bahamas and Haiti to better understand the different pieces of this complex puzzle. Our field studies show that artificial reefs can increase fish production by increasing production of seagrass. Fish that are attracted to artificial reefs release nutrients in their pee, and these nutrients increase seagrass growth. More seagrass provides more habitat for invertebrates, the major food source for fish. Through this cycle, artificial reefs may in fact increase fish production.
In addition to studying artificial reefs in the real world, we also use computer models to test the importance of each puzzle piece. In these models, we create a seagrass field, artificial reefs, invertebrates, and fish that swim around in a virtual environment, like a video game. Our recent modeling study verifies the first piece of the puzzle: grouped fish increase seagrass production. Our ongoing studies provide hope that building artificial reefs in tropical seagrass fields can in fact increase fish production.
In sum, if you build it, fish will come. And they will pee, seagrass will grow, invertebrates will prosper, fish will forage, and the fisher will be happy with a fresh catch to bring home to their family.