Relative Condition Factors of Fish as Bioindicators One Year after the Deepwater Horizon Oil Spill

Abstract

Creel surveys were performed over a three week period in late spring, 2011, in the Lafourche and Calcasieu area estuaries of the Louisiana Gulf Coast. Weights and lengths were measured for black drum (Pogonias cromis), red drum (Sciaenops ocellatus), and spotted seatrout (Cynoscion nebulosus), and relative condition factors were calculated relative to expected weights from the long term (5 year) Louisiana data for each species. A normal relative condition factor is 1.00. The mean relative condition factors in the Lafourche area were black drum, 0.955 ± 0.020; red drum, 0.955 ± 0.011; spotted seatrout, 0.994 ± 0.009. In the Calcasieu area, the mean relative condition factors were black drum, 0.934 ± 0.017; red drum, 0.965 ± 0.014; spotted seatrout, 0.971 ± 0.010. Results suggest that the abundance of primary food sources for black drum and red drum in Lafourche, including oysters and crab, were likely affected by the oil spill and continued to be reduced one year later. Increased harvest of oysters and blue crab in the Calcasieu area (in part to make up for the ban in most of Louisiana) resulted in less food for the black drum and red drum there, also. Spotted seatrout eat mainly shrimp and small fish and showed no significant reduction in relative condition factor in Lafourche and a slight reduction in Calcasieu one year after the oil spill.

Freshwater Fish as Sentinel Organisms: From the Molecular to the Population Level, a Review

“…Gonadosomatic index (GSI) is also a percentage relationship between the gonad weight and fish weight. Depending on the severity of exposure to xenobiotics, the sublethal effects can be to limit physiological capacity, reduce growth, and impair reproduction, therefore GSI is a convenient organosomaitc index [36].…”