Do Red Snapper Call Decommissioned Oil Rigs Home?

Reference: Downey, C. H., Streich, M. K., Brewton, R. A., Ajemian, M. J., Wetz, J. J. and Stunz, G. W. (2018), Habitat‐Specific Reproductive Potential of Red Snapper: A Comparison of Artificial and Natural Reefs in the Western Gulf of Mexico. Trans Am Fish Soc, 147: 1030-1041. doi:10.1002/tafs.10104

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The Red Snapper
Red snapper on a reef. Source: NOAA FishWatch

Red snapper, Lutjanus campechanus, is an economically and ecologically important reef fish in the Gulf of Mexico. Since the mid-1800s, it has been a popular commercial and recreational species. Red snapper prefer to live around hard substrate such as natural banks, ridges, and reefs. However, large portions of the Gulf of Mexico are dominated by a muddy bottom, and there are few areas of hard-bottom bank for the red snapper to reside. Could this be a limiting factor for red snapper populations?

Artificial Structures in the Gulf

The Gulf of Mexico is one of the major petroleum-producing areas of the United States. As such, energy exploration has been an integral part of the Gulf’s history. Oil and gas platforms resulting from energy exploration are artificial hard structures residing in the Gulf’s waters. Some researchers believe that the presence of these structures may double as artificial reef habitat for reef-dwelling species. Anecdotal evidence indicates that red snapper is often the dominant species observed around the artificial structures. However, previous research suggests that red snapper’s tendency to associate with these structures is regional within the Gulf. Similarly, research suggests that the associations may be dependent on age and size of the fish.

Offshore oil platforms. Source: Chad Teer

These findings have since sparked a debate within the fisheries community on whether artificial reefs are valuable for reef fish, specifically red snapper, compared to natural reefs.

Idle Iron & Rigs-to-Reefs

In 2010, the U.S. implemented the Idle Iron Policy which requires oil and gas companies to dismantle and responsibly dispose of their infrastructure after the oil wells are deemed unproductive. Because of this, many platforms in the Gulf are slated for removal. However, some states recognize the potential benefit of these structures for reef-dwelling organisms and have participated in a program called “Rigs-to-Reefs”, where structures will be converted into designated artificial reefs.

To Keep or Not to Keep

The debate about oil platforms, artificial structures, and reef fish is at the forefront in the Gulf of Mexico. Because of this, Downey et al., a group of researchers from Texas, developed a study to understand how artificial structures function in comparison with natural banks. They chose to use the Gulf red snapper population as the focus of the study. Specifically, they aimed to examine the reproductive characteristics of red snapper on natural vs artificial reefs. Red snapper’s reproductive biology was used as a key parameter – that is, do fish using various habitat types have similar reproductive characteristics?

Does Habitat Matter?
Decommissioned oil rig turned reef. Source: US Bureau of Ocean Energy Management

To address this question, researchers collected red snapper from a study area in the western Gulf of Mexico from 2013 to 2015. They collected a total of 1,585 fish from three different habitat types: natural hard-bottom banks, standing oil platforms, and decommissioned oil platforms. For each fish they collected they measured length and weight and tagged it with location and habitat type. In the lab, they were able to identify its sex, condition, age, and reproductive status. They also tried to determine if the snapper collected on artificial structures had a similar spawning season to red snapper found in natural areas. They determined this by calculating their gonadosomatic index (GSI), a measure to determine sexual maturity in fish.

The researchers found that red snapper residing on both types of artificial habitat had similar reproductive capabilities and a similar spawning season as those found on natural banks. These results suggest that red snapper living on artificial reefs are just as capable of contributing to the population as red snapper on natural banks.

Management Implications

Downey et al. demonstrated that red snapper populations are equally productive on artificial reefs as they are on natural banks. This information is vital for the management of reef fish populations as well as an important discussion point surrounding the decommissioning or removal of oil platforms. The use of platforms as reefs by red snapper may be ultimately beneficial to the population. In fact, the removal of these structures could be detrimental to the red snapper population by further diminishing adequate habitat required for their growth and reproductive activities. There are ongoing disagreements about the Rigs-to-Reefs program, but as this study shows, it could continue to provide a unique habitat for reef fish in the Gulf of Mexico.

 

 

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Lauren Bonatakis

Lauren Bonatakis

I'm a second year Master's student at LSU studying the commercial freshwater fisheries in Louisiana. I am interested in pursing a career focused on the intersection of fisheries science, policy, and management. Outside of science I enjoy going to as many concerts as I can, hanging with my dog, and traveling.

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