Health status in wild and captive short mackerel, Rastrelliger brachysoma from Thailand: Histopathology

Information regarding the health status of wild and captive Rastrelliger brachysoma (Bleeker, 1851) is scanty. This is an economically/ ecologically important fish species in Thailand which has experienced recent dramatic declines in population numbers. Therefore, the aim of this research was to assess the health status of this fish using histopathology as biomarker. The results revealed previously the gill lesions including lamellae disorganization, fusion and edema with lifting of lamellar epithelium in the secondary lamellae. The skin histopathology included epidermal hyperplasia and the proliferation of the Malpighian cells. Pyknotic nuclei and vacuolar degeneration of exocrine acinar cells were detected in the pancreas tissue. Degeneration of the renal parenchyma and tubules as well as the melanomacrophage center (MMC) was observed in kidney tissue. In captive fish, the most common histopathology of gill tissue, primary lamellae disorganization and degeneration of secondary gills, was observed in all samples. In some areas of the kidney tissues, renal degeneration and damage to the glomeruli throughout the majority of the macrophage aggregates (MMC) were also found. Important histopathological observations of liver tissue were hepatic degeneration, focal coagulation necrosis and increased frequency of MMC. Interestingly, a gastric tumor was observed in only one male specimen. Additionally, it must be emphasized that histopathological alterations are an effective biomarker used to evaluate potential effects of the environmental pollution on fish health and marine biota.