Vertical distribution and habitat association of four blenniidae species on gas platforms in the northcentral Gulf of Mexico

Abstract

The abundance of Blenniidae on platforms in the northern Gulf of Mexico may be substantially underestimated. Previous studies have reported the abundance of blenny species on platforms to range between 0.6 fish and 16 fish m^-2. In this study, we used visual surveys to quantify densities of four blenny species (Hypsoblennius invemar, Hypleurochilus multifilis, Parablennius marmoreus, and Scartella cristata) on two gas platforms 14 to 24 km southeast of Dauphin Island, Alabama in July and August 1999. Our mean Blenniidae densities were substantially higher than those in previous accounts. Densities of all four species decreased as depth increased from 3 m to 18 m: 10 fish m^-2 to 1 fish m^-2 (H. invemar), 23 fish m^-2 to 6 fish m^-2 (H. multifilis), 6 fish m^-2 to 2 fish m^-2 (P. marmoreus), and 89 fish m^-2 to 0 fish m^-2 (S. cristata). Blenny length distributions were estimated using three 51 mm total length (TL) categories. Eighty percent of H. invemar, 74% of H. multifilis, 49% of P. marmoreus, and 47% of S. cristata were < 51 mm TL. Blennies occupy crevices and cavities, so, the fouling community on the platform pilings was sampled to predict why blennies <51 mm TL were so abundant. We measured the abundance of fouling organisms such as barnacles, mollusks, and sponges that can affect the availability of crevices and cavities. Abundance of the large barnacle Balanus tintinabulum decreased significantly as depth increased from 3 m to 18 m (χ² = 15, p < 0.05), substantially affecting local relief and hence habitat available to blennies. However, B. tintinabulum abundance was not useful for predicting the abundance of H. multifilis (r² = 0.04, p > 0.05) and P. marmoreus (r² = 0.07, p > 0.05). Balanus tintinabulum abundance did account for 48% (p < 0.05) of H. invemar and 81% (p < 0.05) of S. cristata variability. The community structure of non-game fishes , like Blenniidae, can be used to estimate the ecological success of artificial structures as reefs.