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Regards, John

Thank you John! That lead me to the idea of using dried blood spots in the field to store blood samples. Later I'll try to extract the cortisol in the lab using RI-Assays (like Wong et al. 2004) or LC-MS/MS (like Janzen et al. 2011). I'm not certain that it will work but it's worth the financial risk of obtaining filter cards.

Janzen, Nils; Sander, Stefanie; Terhardt, Michael; Steuerwald, Ulrike; Peter, Michael; Das, Anibh M.; Sander, Johannes (2011): Rapid steroid hormone quantification for congenital adrenal hyperplasia (CAH) in dried blood spots using UPLC liquid chromatography-tandem mass spectrometry. In: Steroids 76 (13), S. 1437–1442. DOI: 10.1016/j.steroids.2011.07.013.

Wong, Vincent; Yan, Tony; Donald, Andrew; McLean, Mark (2004): Saliva and bloodspot cortisol: novel sampling methods to assess hydrocortisone replacement therapy in hypoadrenal patients. In: Clinical endocrinology 61 (1), S. 131–137. DOI: 10.1111/j.1365-2265.2004.02062.x.

Hello

I read many articles about fish cortisol assay, but I did not find any paper on dry blood cortisol assay. However, you may try scale cortisol assay. You can dry the scales and then extract cortisol for assya:

Article Scales Tell a Story on the Stress History of Fish

Thank you for that suggestion, Seyyed! That is very interesting indeed, I will read through the article that you suggested. On the first glance, it seems like both dried blood spots and scales yield reliable cortisol values if analyzed via LC-MS/MS tandem. Do you have an idea how long scales can be stored for later analysis? I will be in the field for 60 days and can only afterwards analyze my samples.