Aquaculture production continues to increase to satisfy global demand, and as such, issues relating to its environmental sustainability and the welfare of fish are becoming more prominent within society. Sterile triploid fish (possessing one additional chromosome set to the more natural diploid state) are in use in aquaculture and fisheries management to avoid the problems associated with unwanted early sexual maturation and genetic interactions between wild and cultured fish. Triploids are physiologically and behaviorally similar to diploids, although ploidy effects do exist. This review focuses on the welfare of triploid fish within aquaculture and fisheries management. The main conclusions are that triploids appear more susceptible to temperature stress, have a higher incidence of deformities, and are less aggressive than their diploid counterparts. However, considerable knowledge gaps exist in triploid physiology and performance; therefore, triploid requirements for water quality, nutritional requirements, stocking densities, and slaughter methods cannot be fully assessed. In addition, other than growth and survival, no information exists on the performance of triploids when released into natural environments, and this is of considerable concern, as triploids are commonly used in catch-and-release fisheries. These matters become more pressing with today's increased emphasis on animal welfare.

Embryonic and larval zebrafish (Danio rerio) behavior is commonly used to identify neurotoxic compounds. Here, we investigated whether sub-lethal exposures to the common solvents dimethyl sulfoxide (DMSO, 0.01-1%) and methanol (MeOH, 0.01-1%), or the anti-fungal agent methylene blue (MB, 0.0001-0.0005%), can influence larval behavior in a simple light/dark paradigm conducted in 96-well plates. In addition, we tested whether the media volume within the behavioral arena or the zebrafish strain, AB wild type, AB Tübingen (AB/TU), or Tüpfel long-fin (TL), could also influence larval behavior. Following the single exposures, we co-exposed larvae to DMSO and either MB or two other compounds with known behavioral effects in larval zebrafish, flutamide and perfluorooctanesulfonic acid (PFOS). We found ≥0.55% DMSO and 0.0005% MB significantly affected larval behavior, but there was no effect of MeOH. Similarly, TL showed less movement compared to AB and AB/TU strains, whereas lower media volumes also significantly reduced larval movement. However, all strains responded similarly to DMSO and MB. In the co-exposure studies, we found either additive or interaction effects between DMSO and either MB, flutamide, or PFOS, depending on the behavioral endpoint measured. In addition, media volume had no effect on the DMSO concentration response curve, but again we observed additive effects on behavior. In conclusion, methodology can lead to alterations in baseline locomotor activity and compounds can have additive or interaction effects on behavioral endpoints. However, we found no evidence that strain effects should be a concern when deciding on solvents for a simple light/dark behavioral test in larval zebrafish.

The objective of this investigation was to compare the toxicity of two manufactured carbon nanomaterials (CNs) to determine if shape influenced toxicity. Juvenile rainbow trout Oncorhynchus mykiss were fed a control diet (no CN addition), or a diet supplemented with 500 mg single-walled carbon nanotubes (SWCNT) kg⁻¹ or 500 mg C₆₀ kg⁻¹ for six weeks. Fish growth, haematology, tissue ion concentrations, histopathology, osmoregulation, and biochemistry were evaluated. At week 4, but not on weeks 2 and 6, significant elevation in brain TBARS (an indication of lipid peroxidation) was observed in fish exposed to SWCNTs (16.2 ± 1.38 nmol mg⁻¹ protein) compared to the control (9.11 ± 0.81 nmol mg⁻¹ protein) and fish exposed to C₆₀ (8.28 ± 0.56 nmol mg⁻¹ protein). No other significant treatment-related differences were observed. Results indicate that dietary exposure to SWCNTs and C₆₀ in rainbow trout did not result in overt toxicity.