Recruitment patterns of juvenile fish at an artificial reef in the Gulf of Mexico
Arney, Rachel Noel
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In 2011, the Texas Parks and Wildlife Department deployed 4,000 culverts as an artificial reef off Port Mansfield, TX to serve as habitat for sport fish species in the Gulf of Mexico. The aim of this study was to assess juvenile fish recruitment at particular culvert densities among the reef. Standard monitoring units for the recruitment of reef fish (SMURFs) were used in this study and acted as sampling devices. SMURFs were placed at thirteen sampling stations among four different reef patch densities and sampled repeatedly from 2013-2014. Culvert densities included stations with: zero culverts, 1-50 culverts, 51-100 culverts, and 101+ culverts in a 30m radius. The stations were also characterized by measurements of rugosity, vertical relief, and percent cover and used as environmental response variables to elucidate factors that drive juvenile recruitment. Average species richness was highest in bare stations and lowest in dense culvert stations. No settlement pattern was observed among recent arrivals measuring ≤ 55mm TL suggesting that arrival of the smallest fish is stochastic. Species compositions were significantly different between the bare stations and all stations with culverts with an average similarity of 33.8 %. The belted sandfish, Serranus subligarius was the most ubiquitous species among all stations. The juvenile community observed in visual SCUBA surveys showed lower measures of species indices and only 14% similarity to the community sampled by the SMURFs. These results suggest that SMURFs are a more effective tool for examining juvenile fish at an artificial reef due to the cryptic nature of juveniles and the low visibility in shallow reefs along the Texas coast. Commercially important species Epinephelus flavolimbatus, Epinephelus nigritus, and Lutjanus campechanus were only found at SMURFs as juveniles in the bare stations. These findings indicate that fisheries management may benefit from creating small, rubble-reef patches away from the main reef where juveniles can recruit and grow. The results of this study reveal aspects of reefs that are important to juvenile fish recruitment and will be valuable to improve the effectiveness of artificial reefs in the future.