Abstract

Community composition and abundances of fish species were examined from six South Texas banks, including from north to south Baker, Aransas, Dream, Blackfish, Mysterious, and a previously undescribed bank referred to herein as Harte Bank. These shelf-edge banks are relic coralgal reefs that existed off the South Texas coast approximately 21,000 to 12,000 years BP but were drowned and buried as a result of Pleistocene deglaciation and subsequent rise in sea level. Today, the remnant peaks of these reefs protrude 14 to 22 m above the surrounding sediment from depths of 58 to 84 m with buried portions extending 20 to 30 m beneath the sea floor. Enumeration and identification of fish species was accomplished by reviewing video footage from an ROV deployed from the R/V Falkor of the Schmidt Ocean Institute in September 2012. Multiple ROV transects were made across each of the relic banks. Fish abundances were standardized (relative percentages) to account for differences in sampling effort among the banks. Community assessments were limited at Mysterious Bank due to low visibility resulting from a nepheloid layer suspended across surveyed terrace. Collectively, 45 fish species in 17 families were recorded from Baker, Aransas, Dream, Mysterious, Blackfish, and Harte banks. Five species accounted for 66% of total abundance including Pronotogrammus martinincensis (rough tongue bass; 25.5% of total), Chromis insolata (sunshine fish; 15% of total), Stegastes variabilis (Cocoa damselfish; 10.4% of total), Lutjanus campechanus (red snapper; 7.7% of total), and Chromis scotti (purple reeffish; 7.3% of total). Diversity generally diminished from north to south along the relic coral bank chain with Baker and Aransas banks having the highest diversity. Community similarity was highest among the northernmost banks and distinct from the southernmost bank.

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