Noninvasive assessment of nitrate-induced stress in koi Cyprinus carpio L. by faecal cortisol measurement

Abstract

This study determined effects of nitrate (NO3−)‐induced stress on faecal cortisol levels in koi (Cyprinus carpio). NO3− was presented in two formats: (1) bulk increase followed by dilution to assess cortisol response and recovery and (2) bulk increase followed by incremental increases to assess cortisol response limit. Fish were maintained group‐wise in treatment and control aquaria (n=6 per group), and 0.5 g L−1 NO3− (as NaNO3) was added to the water. Faecal samples were collected daily and blood samples were taken pretreatment and 72‐h posttreatment and were assayed for cortisol via ELISA. NO3− increased plasma and faecal cortisol 4.4‐fold and 3.9‐fold respectively. Plasma cortisol was not measured further. After a 74% NO3− decrease by dilution, faecal cortisol decreased to baseline within 24 h, and restimulation by NO3− (1.0 g L−1) elevated faecal cortisol to maximal study levels. In a separate experiment, exposure to 0.4 g L−1 NO3− increased faecal cortisol 6.9‐fold. However, three additional 0.4 g L−1 NO3− increments across 9 days did not further increase cortisol. This study demonstrates that faecal cortisol measurement in fish via an ELISA can be useful as an indicator of NO3−‐induced stress in the aquatic environment.

Measuring cortisol, the major stress hormone in fishes

“…In the latter case, it involves conscientious tracking of the focal fish or holding the animal individually. However, because of the low concentrations of cortisol in the faeces, the quantity required to detect cortisol is generally important, such that numerous fish are commonly used (Lupica & Turner Jr, ; Turner et al, ). For instance, using six rainbow parrotfish Scarus guacamaia Cuvier 1829, Turner et al () detected an average of 3.4 ng cortisol g −1 faeces (wet weight) in aquaria and 2 ng g −1 in the field.…”

Stress response to daily temperature fluctuations in common carp, Cyprinus carpio L.

“…Interestingly, the period from spring to early summer is also associated with an increase in the prevalence of disease (e.g., Cyprinid herpesvirus 3 (CyHV-3)) disease, Matsui et al, 2008). A number of studies have examined the stress response to crowding, tag insertion, nitrate exposure, confinement, and cold shock in common carp (Tanck et al, 2000;Ruane & Komen, 2003;Lower et al, 2005;Lupica & Turner, 2010;Pottinger, 2010). However, little is known about the effect of daily temperature fluctuations in this species.…”

Dynamics of endogenous and water cortisol release in Asian SeabassLates calcariferafter acute stress in a farm scale recirculating aquaculture system

“…Fish stress has negative effects on growth, survival, and meat quality, and is both a cause and consequence of disease (Snieszko, 1974; Bly, Quiniou and Clem, 1997; Daskalova, 2019). Pathogenic infections (Ellis et al ., 2007; Triki et al ., 2016) and environmental stressors such as poor water quality (Lupica and Turner, 2010; Mota et al ., 2017a; Zarantoniello et al ., 2021), handling (Scott, Pinillos and Ellis, 2001; Ellis et al ., 2004), noise (Mickle and Higgs, 2018), and overcrowding (Pavlidis et al ., 2013; Odhiambo et al ., 2020) commonly induce the stress response in fish, which is marked by the secretion of the stress hormone, cortisol. As such, cortisol has been utilized as a biological indicator of fish stress levels in both laboratory and aquaculture settings (Martínez-Porchas, Martínez-Córdova and Ramos-Enriquez, 2009; Sadoul and Geffroy, 2019; Tanaka et al ., 2023).…”