Community structure and diets of fishes associated with pelagic Sargassum and open-water habitats off North Carolina
- UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
- Tara L. Casazza (Creator)
- Institution
- The University of North Carolina Wilmington (UNCW )
- Web Site: http://library.uncw.edu/
- Advisor
- Steve Ross
Abstract: The community structure and diets of fishes inhabiting Sargassum and open water
lacking Sargassum were examined off North Carolina during annual summer or fall cruises,
1999-2003. Significantly more individual fishes (n= 18,799), representing at least 80 species,
were collected in samples containing Sargassum, compared to 60 species (n=2706 individuals)
collected in open water. The majority of fishes collected in both habitats were juveniles, and
Stephanolepis hispidus dominated both communities. Regardless of sampling time (day or
night), Sargassum habitat yielded significantly higher numbers of individuals and species
compared with open water collections. Overall, fishes collected in Sargassum neuston net tows
were significantly larger than fishes collected in open water neuston tows. A significant positive
linear relationship existed between numbers of fishes and Sargassum quantity. Underwater video
recordings indicated a layering structure of fishes among and below the algae, with smaller
fishes being more tightly associated with the algae than larger fishes. Additional observations
from underwater video recordings included schooling behaviors of filefish, dolphinfish and
jacks, and fish-jellyfish associations.
The diets of the dominant fish species collected from Sargassum habitat were compared
to the diets of the same species collected from open water, the diets of fishes collected during the
day were compared to the diets of fishes collected at night within and across habitats, and the
diets of each fish species across different size ranges were compared. Fishes collected from
Sargassum consumed a higher diversity and volume of prey compared with fishes collected from
open water. Fishes collected from Sargassum habitat had fewer empty stomachs than fishes
collected from open water. Overall, fishes collected from Sargassum primarily consumed fishes
that are closely associated with the algae (e.g., balistids, carangids, monacanthids) and endemic shrimps (Latruetes fucorum and Leander tenuicornis). In contrast, open-water fishes primarily
consumed copepods and fishes from the family Exocoetidae. Comparisons between the diets of
Sargassum-associated fishes and fishes collected from open water indicated several species fed
similarly in both habitats. Fishes belong to one or more of three trophic groups: zooplanktivores,
crustacean feeders or piscivores. Overall, fishes collected from Sargassum and open-water
habitats primarily fed during the day. It appears Sargassum habitat enhances early survival of
pelagic fishes by providing protection and concentrating prey resources in an otherwise nutrient poor
area of the western North Atlantic Ocean. Efforts should be made to protect this unique
pelagic habitat because these fishes are very closely tied to Sargasssum and may not be able to
survive without Sargassum.
Community structure and diets of fishes associated with pelagic Sargassum and open-water habitats off North Carolina
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Additional Information
- Publication
- Thesis
- A Thesis Submitted to the University of North Carolina Wilmington in Partial Fulfillment of the Requirements for the Degree of Master of Science
- Language: English
- Date: 2009
- Keywords
- Fishes--Effect of habitat modification on--North Carolina, Fishes--Food--North Carolina, Marine algae, Sargassum, Sargassum--Food
- Subjects
- Sargassum
- Marine algae
- Fishes -- Effect of habitat modification on -- North Carolina
- Fishes -- Food -- North Carolina
- Sargassum -- Food