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Biology

How Our “Trash” Can Aid Juvenile Red Snappers

Article: Jason R. Brandt & Donald C. Jackson (2013) Influences of Artificial Reefs on Juvenile Red Snapper along the Mississippi Gulf Coast, Marine and Coastal Fisheries: Dynamics, Management, and Ecosystem Science, 5:1, 1-10. DOI:10.1080/19425120.2012.736445

Have you ever thought about what happens to old container ships or broken bridge sections? While they may seem like trash to us, several marine organisms are turning these used structures into homes and breeding areas. Cement, limestone, and even old barges are being used in the northern Gulf of Mexico to build additional habitats for several fish species. These recycled, man-made structures, also known as artificial reefs, have been piling up off the coast of the U.S. for the last 50-some years. While these rubble piles may look random, time and energy has gone into figuring out what the best design is to help aid fish species in terms of habitat safety.

Different fish species thrive in different environments; therefore, scientists from Mississippi State University set out to explore what types of artificial reefs benefit the Red Snapper population the most. In order to accomplish this task, they targeted the question of where exactly to place these “random rubble piles” and how close they should be to one another. With the hope that artificial reefs will help build back the Red Snapper population in the Gulf, juveniles were the targeted catch in this project. The behavior of young Red Snappers can tell us a lot about how resilient the adults are going to be, therefore fish traps designed specifically for juveniles were set among artificial reefs in the Gulf. All artificial reef structures in this project were rock and limestone pyramids (Figure 1), however, they differed in how much space was between them. Some pyramids were clumped very close together, while others were spaced far apart. After a total of 927 juvenile Red Snappers were caught over a one-year span, results were compiled in order to see their spatial distribution.

Figure 1. Pyramid construction of the artificial reefs.

Figure 1. Pyramid construction of the artificial reefs.

Findings

Results showed a significant difference in fish size between clumped versus non-clumped reef structures. Researchers determined that smaller Snappers were found on the clumped pyramids, while the larger, but still juvenile, Snappers were found living in the more spaced out reefs. While the total number of Snappers did not differ dramatically between reef areas, the fact that only the smallest of the Snappers were found in a clumped reef zone shows how important habitat is: The smaller the animal, the more protection it needs. Small, soft-bottom dwelling critters are an ideal meal for a young Snapper, but consuming these critters can be quite dangerous for a small fish. Reefs that are placed too close together tend to overlap the prey’s habitat, thus hindering their population. Therefore, in order to scavenge for a hearty meal, Snappers have to venture beyond a clumped reef, searching for their small prey.  For the smallest of Snappers this venture poses a huge threat to their survival, which may be one of the reasons only the smallest of the Red Snappers stay in clumped reefs. Results from this study also showed a higher abundance of juveniles in the summer compared to the spring and fall, which proves juveniles will actively seek out refuge among artificial reefs during the summer. Past research has shown adult Red Snappers to have the opposite response to seasons, living in the artificial reefs during the fall and spring and then moving on in the summer. Adults have a huge advantage over juveniles in terms of speed and size and can outcompete them for food, so researchers believe that the offspring wouldn’t want to share a reef with the adults.

Future Implications

This project demonstrates that artificial reef structures provide an important habitat for the Red Snapper population. Reef spacing has proved to be an important element in the design process of artificial reef placement. Clumped reefs are ideal only for the smallest of Snappers and all juveniles prefer their space from adults. As previously stated, different fishes thrive in different environments, therefore, several design methods must go into artificial reef development. Reef spacing is only one characteristic, but it is now an obvious factor in helping to revive the Red Snapper population. Catering to threatened species, such as the Red Snapper in the Gulf, will allow artificial reefs to aid in the comeback of fish populations. Those piles of rubble aren’t just random trash deposits, but rather valuable areas of protection for many different species. With the right construction and placement, they may just save a threatened population.

Valeska Upham
For my fisheries and aquatic science PhD I am working on how to tank raise urchins and transplant them onto reefs across the Florida Keys in order to help reverse the phase shift from algae dominated back to coral dominated.

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