Age frequency, growth, mortality and PAH levels of roughtongue bass, Pronotogrammus martinicensis, following the Deepwater Horizon oil spill

Abstract

The 2010 Deepwater Horizon (DWH) oil spill and its immediate effects on the surrounding ecosystems have been extensively examined, but longer term effects are still widely unknown. Among the regions potentially affected by the DWH spill were the Pinnacle reefs located 54 to 111 km from the spill site. Roughtongue bass, Pronotogrammus martinicensis, is an ecologically important resident fish from these “mesophotic” reefs. The present study examined age frequency, growth rate, mortality, and PAH levels in roughtongue bass from the Pinnacle reefs. Sample sites within the Pinnacles included the Alabama Alps 54 km from the DWH site, and Roughtongue Reef 111 km from the DWH site. Fish were collected in September-October 2014 (n = 190), December 2014 (n = 249), March 2015 (n = 310) and June-July 2015 (n = 360). Size of roughtongue bass collected ranged from 54 to 135 mm standard length (SL; n = 1109). Resident fish (n = 1090) were dominated by the 2009 and 2010-year classes. The Von Bertalanffy (VB) growth rates (L∞ = 103.5, K = 0.54, t0 = 0.02, R2 = 0.22) were similar to previous pre-oil spill estimates. The VB growth curve for the east site (L∞ = 101.2, K = 0.73, t0 = 0.22, n = 873, R2 = 0.17), showed faster rates than the west site (L∞ = 95.7, K = 0.32, t0 = -1.48, n = 216, R2 = 0.20), and comparisons of the linear portions of the curves confirmed significant differences in growth rates between east and west sites (F3,1081 p < .02). Roughtongue bass mortality rate (M) = 1.7 and survival rate (S) = 18%. Polycyclic aromatic hydrocarbons were detected (> 5 ppb) in 76 % of the roughtongue bass tested (n=38; mean ± SE = 50 ± 52.2 ppb), but below the minimum 300 ppb level that had detectable effects in marine organisms established by the EPA in 1987. Levels of PAH in fish were not significantly different between collection sites and were not correlated with growth. The present study examined a mesophotic reef species where PAH contamination might be expected due to reefs proximity to the DWH oil spill site. Despite this close proximity, there was little effect detected in this ecologically important mesophotic reef fish species.