The bitterness of racemic praziquantel (PZQ) currently constrains its use as an infeed treatment against monogenean flukes in finfish aquaculture. In an effort to increase the palatability of diets containing racemic PZQ for yellowtail kingfish, the palatability and efficacy of 2 forms of racemic PZQ (powder or powder within microcapsules) against natural infestations of skin and gill flukes were compared using 2 different dietary application methods (incorporated within the pellet mash prior to extrusion or surface-coated after extrusion) at active dietary inclusion levels of 8, 16 and 25 g kg −1 in large (3.5−4 kg) yellowtail kingfish. There was no clear benefit of incorporating PZQ into diets prior to extrusion. PZQ microcapsules improved the palatability of PZQ-containing diets but did not completely mask the bitter flavour. At the lowest active dietary inclusion level of 8 g kg −1 , ingestion of the diet containing PZQ microcapsules was equal to the control and significantly better than that containing PZQ powder. At an inclusion level of 16 g kg −1, ingestion of the PZQ microcapsule diet was significantly better than that containing the same inclusion of PZQ powder but significantly lower than the control. Consumption of the diet containing 25 g kg −1 of PZQ microcapsules was poor. All fish consuming medicated feeds had a significant reduction in flukes relative to control fish; however, efficacy data and blood serum analysis suggested that diets containing PZQ microcapsules had lower bioavailability than those containing PZQ powder.

The direct and indirect effects of a simulated, calcarenite-based dredge material on eggs and larvae of pink snapper Pagrus auratus were assessed. Direct effects were assessed by measuring hatch rate or survival of eggs and pre-feeding larvae, respectively, over a range of concentrations and exposure durations. Exposure of eggs to suspended solid concentrations up to 10 000 mg l(-1) for 24 h did not affect egg buoyancy or hatch rate, despite sediment adherence occurring at the two highest concentrations tested. Newly hatched larvae, whose mouths were still closed, were relatively tolerant of suspended solids, with a 12 h lethal concentration resulting in 50% mortality, LC(50), of 2020 mg l(-1) and a first observable effect concentration of 150 mg l(-1). Once the larvae's mouths opened, tolerance was significantly reduced, with a 12 h LC(50) of 157 mg l(-1) and a first observable effect concentration of 4 mg l(-1). Tolerance of larvae to suspended solids was negatively correlated with suspended solids concentration and exposure time, with exposure durations of