Impact assessment of various rearing systems on fish health using multibiomarker response and metal accumulation.

European sea bass were reared in three different systems: one flow-through (FTS), one recirculating (RAS), and one recirculating with a high-rate algae pond (RAS + HRAP). After 1 year of rearing, the final fish weight was 15% lower in the RAS compared to the FTS. The accumulation of a growth-inhibiting substance in the RAS is the main hypothesis explaining this difference. As in environmental risk assessment, fish bioaccumulation markers and biomarkers were used to demonstrate exposure to and effects of the rearing water in the three rearing systems. Thirty fish per system were sacrificed before their condition factor (CF) and liver somatic index (LSI) were calculated. Nine biomarkers, including ethoxyresorufin-O-deethylase (EROD) and superoxide dismutase (SOD), were measured in liver and twelve metals including As, Cd, Cu, Pb, Cr, and Zn, for which there are regulations regarding human consumption, were measured in liver and muscle. In all systems, CF and LSI were not significantly different and no correlation was found with biomarker activity or metal concentration. EROD and SOD activities were significantly increased in RAS. Accumulation of seven and four metals in muscle and liver, respectively, was significantly higher in the RAS relative to FTS. The HRAP prevented metal accumulation except for chromium and arsenic. Eight metal concentrations were significantly higher in liver than in muscle. Concentrations of toxic metals were similar to reported values and below FAO/WHO recommended values for human consumption.

Spatial and temporal co-structure analyses between ichthyofauna and environment: an example in the tropics.

Ichthyofauna distribution and habitat characteristics of Thalassia beds in the Grand Cul-de-Sac marin lagoon in Guadeloupe were studied during a one-year survey. Environmental variables (9) were measured monthly in ten sites along with collection of fish communities. The environmental data set, analysed alone through between-within group 'principal component analysis' (PCA), exhibited a significant spatial and temporal variability. The fish data set, however, presented only a significant spatial structure, stable over the year. Given the lack of temporal variability in fish distribution, a 'between-site co-structure analysis' (BSCA) was used to compare the faunistic and environmental structures in space. The co-inertia structure was reduced to one axis representing a strong coast-reef gradient, the major common phenomena to both data sets. Environment and fish distribution allowed to distinguish sites directly under mangrove influence (characterised by high seagrasses, high concentration of chlorophyll a and high densities of zooplankton), to sites under reef influence (with short but dense seagrasses, clear water, and poor nutriments). For that purposes, the BSCA summarised efficiently what in common the fauna spatial structure and the environment spatial structure may present.