One Fish, Two Fish, Red Fish, Killifish

Melanie Herrera, U. of Maryland, College Park

After 9 sampling days, 18 collections, and over 3000 fish, we’ve discovered fishes’ habitat preferences are much more complex than we thought. To recap, our hypothesis predicted fish would prefer dense sites of the invasive seaweed, Gracilaria vermiculophylla, over sites with more open water (thus, less Gracilaria).  We also predicted that dense site would have greater diversity by attracting various types of fish due to its branches that conceal fish from predators.

Our belief that Gracilaria would fulfill the refuge effect, attracting more fish and more diverse species, was supported through the copious amounts of fish found in Gracilaria. Despite more abundance in the dense sites of Gracilaria, more diversity was shown in sparse sites (Figure 1). Among both the dense and sparse sites Atlantic Silversides and Bay Anchovies, Pipefish, and Striped Killifish were the most abundant and common species. While similar species occurred in both habitats, the sparse site had more occurrences of species that were considered rare in dense sites. For example, sparse sites had more occurrences of Spade fish and Florida Pompanos than dense sites. Additionally, sparse sites had species of fish such as leatherjackets and lizardfish that never occurred in dense sites.

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Figure 1: Rank abundance patterns of fish in dense sites (represented by triangles) and sparse sites (represented by circles) of G. vermiculophylla at Grice Cove. The number of fishes were calculated as a logarithm as a measure of relative abundance of fish at each site. Species are ranked from most abundant (1) to least abundant (8-10). Slopes show differences in species evenness amongst sites. Steeper slopes exhibit less species evenness.

 

Supporting our hypothesis, dense sites did demonstrate more abundance. In total, 2944 fish were collected from the dense sites while 361 fish were caught in the sparse sites. It is predicted that smaller-bodied fish used Gracilaria more as a refuge because of their increased vulnerability to threats as small animals. Lack of abundance in sparse sites could be explained by increased exposure to predators and environmental threats.

Increased use of the dense sites shows Gracilaria does contribute towards housing all types of fish, most importantly economically important fishes. According to the National Marine Fisheries Service’s report on fisheries economic in 2011, the seafood industry alone brings in a minimum of $88 million dollars annually. In order to support this important industry, commercial fisheries can use our research to establish sustainable fisheries by understanding the various habitats that help rear economically important fishes. Our identification of the invasive seaweed’s role on housing fish can be used as a protective measure for these fish in future sustainable management.

 

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Figure 2: Two of the top three most abundant species collected from dense sites of Gracilaria. (Left: Striped Kilifish; Right: Atlantic Silversides).

 

Thank you so much to my mentors Dr. Tony Harold and Mary Ann McBrayer for their advice and guidance. This research is funded through the National Science Foundation and College of Charleston’s Grice Marine Lab.

 

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Catch of the Day(s)

Melanie Herrera, University of Maryland College Park

South Carolina is known for its iconic southern cuisine, including a staple of fresh seafood which fuels the buckets of shrimp & grits and “catch of the day”. In order to support this huge industry (and fill the bellies of every South Carolinian), I am conducting an experiment to figure out where this seafood is holing up prior to its demise. Dr. Harold, his graduate student, Mary Ann McBrayer, and I are out on Grice Beach collecting fishes, crabs, shrimps, and much more in order to figure what exactly is there… And what they are using to survive.

Using a seine net, we encircle marine animals in dense and sparse patches of an invasive sea grass, Gracilaria, for collection. We hypothesize that Gracilaria is helping the local economy (a surprising contribution from an invasive species) by creating refuge for young animals. On the beach, we submerge separate samples of animals (from dense versus sparse areas of Gracilaria) into a euthanizing solution to bring them up to the lab for preservation and analysis (Figure 1).

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Figure 1: An example of animals caught in separate habitats at Grice Cove. The left exhibits animals caught in a dense area of Gracilaria and the right exhibits animals caught from a sparse area of Gracialaria. Credit: Melanie Herrera

In the lab, separate samples (dense versus sparse) undergo a few transfers into different fixatives (10% seawater formalin, 25% isopropyl, and 50% isopropyl consecutively) to keep the fish from decaying. After this preserving process, fish and other animals are separated and categorized by family, genus, and species. This categorization enables us to identify and analyze what types of animals and how many of each are using different habitat. Our analysis will give us insight on what type of habitat, either patches dominated by Gracilaria or areas with more open water, benefits fish. Specifically, we will be able to identify if Gracilaria is more advantageous to young fish or if their survivorship is independent from their habitat.

So far, we have collected lots of pipefish, narrow skinny fish that resemble a hair strand-size snake, Atlantic Silversides, a fish that looks exactly like it sounds, and more shrimp than anyone needs (Figure 2). Although some of these animals do not directly contribute to the seafood industry, its presence in the Charleston Harbor can tell us a lot of things. For example, we have seen some fishes that usually stay in warmer waters in the Southern U.S. Their expanding habitat can lead us to some more hypotheses on climate change and warm weather moving northward. In addition, we can find out if Gracilaria has a stake in rearing economically important fish in the future.

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Figure 2: (From left to right) Pipefish, Atlantic Silversides, and Grass Shrimp caught for analysis.Credit: Melanie Herrera

Thank you so much to my mentor Dr. Tony Harold and his lab for his advice and guidance. Thank you to Mary Ann McBrayer for helping me facilitate this project. This research is funded through the National Science Foundation and College of Charleston’s Grice Marine Lab.

 

Invasive Species: Friend or Foe

Melanie Herrera,  University of Maryland – College Park

Invasive species…. Haunting, domineering, and downright evil. Or are they? Unlike the infamous Zebra Mussels, dominating the Great Lakes, or Fire Ants, constantly wreaking havoc, Gracilaria Vermiculophylla, are giving invasive species a good name. Don’t get me wrong, invasive species infuriate me just as much as the next guy; but Dr. Tony Harold and I are here to draw out the benefits of this invasive sea grass to baby fish.

Unlike the native, simpler sea grass previously occupying Charleston Harbor, Gracilaria is characterized by coarse branching structures that appeal to many species of fish as protective homes. We are particularly interested in fishes in the larval and juvenile stages (the young ones) that associate with these complex habitats. Having access to more protective sea grass, such as this invasive, in these vulnerable life stages can help determine how many of these little guys make it into adulthood. Similar macro-algae to Gracilaria, such as seaweeds, have been known to be preferable hideouts for larvae and juveniles, reducing the pressures of predation. Since Gracilaria is on the rise in our local estuary, the Charleston Harbor, it’s important to find out the role they play in keeping our fish alive and well.

Our project is designed to better understand the level of association of local fish such as Gobies, Atlantic Menhaden, Atlantic Silversides, and other estuary-occupying fishes, with Gracilaria. We will compare abundance and distribution of young fish in dense patches of Gracilaria to sparse patches. Maybe these young fishes prefer the familiarity that native sea grass and open water brings. Or maybe Gracilaria’s “new and improved” design is too advantageous to resist. After we figure this out, we can go on sustainably managing local fish critical to commercial and recreational use and condemning the rest of the invasive species.

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An example of a collection site characterized as a “dense” habitat of Graclaria vermiculophylla.  Photo Credit: Melanie Herrera

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An example of a collection site characterized as a “sparse” habitat of Gracilaria vermiculophylla. Photo Credit: Melanie Herrera

 

Thank you so much to my mentor Dr. Tony Harold and his lab for his advice and guidance. Thank you to Mary Ann McBrayer for helping me facilitate this project. This research is funded through the National Science Foundation and College of Charleston’s Grice Marine Lab.

 

Works Cited

Munari, N. Bocchi & M. Mistri (2015) Epifauna associated to the introduced Gracilaria vermiculophylla (Rhodophyta; Florideophyceae: Gracilariales) and comparison with the native Ulva rigida (Chlorophyta; Ulvophyceae: Ulvales) in an Adriatic lagoon, Italian Journal of Zoology, 82:3, 436-445, DOI: 10.1080/11250003.2015.1020349