Semester of Graduation

Summer 2023

Degree

Master of Science (MS)

Department

Oceanography and Coastal Sciences

Document Type

Thesis

Abstract

Artificial reefs provide critical habitat for fish in areas lacking benthic structure, yet our understanding of how artificial reefs function and develop is limited. Here, changes in reef fish community assemblages were monitored using baited remote underwater video (BRUV) surveys (n=6) before and after a new artificial reef was deployed. Movement of red snapper (Lutjanus campechanus, n=20) and gray snapper (Lutjanus griseus, n=20) between nearby platforms (n=3) and the new artificial reef was examined using acoustic telemetry, and residency was calculated for fish associated with platforms and the artificial reef (red snapper n=12, gray snapper n=8). One year post-deployment, development at the artificial reef was slow, and the reef fish community did not differ from control sites. Residency of red snapper at the artificial reef was surprisingly low with most fish emigrating within the first 36 hours, and no tagged fishes from the surrounding platforms were detected moving to the artificial reef. Results suggest that low relief artificial reefs may offer sub-optimal habitat for reef fish in comparison to vertical relief offered by standing platforms, particularly in areas exposed to benthic hypoxia.

The northwestern shelf of the Gulf of Mexico (GoM) is exposed to a large seasonal coastal hypoxic (dissolved oxygen [DO] ≤ 2.0mg/L) zone; however, in situ measurements of organismal response are limited. Acoustic telemetry was used to examine patterns of vertical hypoxia avoidance in reef fish (red snapper n=10, gray snapper n=10) at a large platform during peak seasonal hypoxia (mid-summer). Species-specific hierarchical generalized additive models were developed to test the influence of benthic DO and individual on fish depth use and vertical habitat compression. Despite clear vertical habitat partitioning, a significant shift in depth use was observed for red snapper and gray snapper, with both species inhabiting deeper water as benthic DO levels increased. Red snapper exhibited vertical habitat compression (38% reduction of vertical habitat) with both species demonstrating individual variability in hypoxia avoidance response. These findings have implications for both management of energy infrastructure and artificial reef deployments, and results highlight the potential benefits of vertical structure for reef fishes in the presence of benthic hypoxia.

Date

7-10-2023

Committee Chair

Michael Dance

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