Nikolai Klibansky, J Kevin Craig, and Matthew D Campbell, Community structure and environmental drivers of offshore hard-bottom reef fishes in the northern Gulf of Mexico, ICES Journal of Marine Science, Volume 81, Issue 9, November 2024, Pages 1724–1744, https://doi.org/10.1093/icesjms/fsae119
Studying Reefs
Large scale studies of reef systems are becoming more important as we try to understand how to protect them from climate change. However, this can be challenging with the amount of organisms that live in these habitats and how environmental factors influence them.
Fish can be categorized into several types of large units that help make studying them easier. Communities are frameworks that establish a broad set of species that occur together in a geographic area. In those communities, there are assemblages which are subsets of taxonomically related species that are in the same space at the same time. For example, on a coral reef there would be a fish community which includes all the fish in the area as they interact with one another in their daily lives. Within that fish community there are multiple assemblages which could include snapper and grouper in one and small bass and wrasse in another.
Environmental Influence
These groups are heavily influenced by environmental conditions at both large and small scales. Depth, geographic location, and gradients like temperature are large scale processes that can have influences across hundreds or thousands of kilometers of ocean. On the opposite side, habitat complexity and organism influence like predation/competition will have much smaller influences at a local scale. Together, large scale processes will determine regional patterns in fish presence that are then modified based on local habitat conditions.
That being said, how do fish presence and environmental conditions interact in the real world? The northern Gulf of Mexico (nGOM) is a great spot to study this. It is a diverse shoreline with reef habitats that contain fish communities important to local economies that are at risk from climate change. Prior studies in this region have been small and isolated including the West Florida shelf, Florida Panhandle, and South Texas shelf. These provide important information about small scale patterns, but fail to understand how they all connect. Klibansky, Craig, and Campbell, 2024, aimed to understand the greater reef fish patterns of the nGOM based on video data from 1995 to 2007.
Northern Gulf of Mexico Diversity
The video data researchers reviewed included 243 fish species across 2115 sites in the northern Gulf of Mexico. The 30 most abundant species accounted for 70% of the individuals observed. Six regions were described across the nGOM displayed in figure 1. Region 6 in South Florida had the greatest species richness with 98 unique species observed. On the other hand, Northeast Florida in Region 4 had the greatest fish biomass (total weight of fish present).
Twelve unique fish assemblages were identified in the nGOM. The assemblage of snapper and grouper made up the largest grouping with 12 species present, 45% of the individual fish observed were in this group, and made up the majority of the biomass observed at 88%.
Environmental factors heavily influenced these assemblages. Large scale processes including depth, temperature and substrate composition (sand vs gravel) were more important than small scale factors. This is important because it shows that prior small scale studies of this region may have missed how influential these greater processes actually are.
Understanding Scale
Even though the northern Gulf of Mexico’s reefs have been studied in the past, they lacked larger observations to understand the greater environmental processes that influence them. This study (Klibansky, Craig, and Campbell, 2024) identified 6 regions in the nGOM that contain 12 unique fish assemblages. The snapper and grouper assemblage was the greatest in size across all categories, demonstrating its importance to the area. Not only that but it was actually large scale environmental factors that influenced fish assemblages, not local processes.
This information will be able to help inform future management plans by establishing baseline fish observations in both space and time. Focused work at the region scale will help see changes across the Gulf of Mexico and understand which regions and fish assemblages may be at risk and which may be refuges from climate change.
I am a recent MSc graduate in marine biology from Bangor University, where I studied population dynamics of elasmobranchs off the coast of Wales. My interests lie in ecological data analysis to understand environmental processes and identify natural patterns. However, nothing beats being in the field and interacting directly with the marine life.