Explorative study on scale cortisol accumulation in wild caught common dab (Limanda limanda)

Area of Science:

• Marine Biology
• Ecotoxicology
• Fish Physiology

Background:

• Marine ecosystems face changes from natural and anthropogenic factors, inducing stress responses in fish, primarily via cortisol.
• Cortisol accumulation in fish scales provides a retrospective method for assessing chronic stress.
• Previous research has not extensively studied scale cortisol concentrations in wild-caught common dab (Limanda limanda).

Purpose of the Study:

• To investigate cortisol accumulation in the scales of wild-caught common dab (Limanda limanda).
• To assess the correlation between scale cortisol levels and plasma cortisol concentrations.
• To evaluate the impact of cortisol accumulation on fish health parameters.

Main Methods:

• Field measurements of scale cortisol concentration in wild-caught common dab.
• Laboratory in vivo study involving feeding dab cortisol-spiked feed for 30 or 90 days.
• Analysis of plasma cortisol, scale cortisol, and various fish health indicators.

Main Results:

• Wild common dab exhibited scale cortisol concentrations (0.0034 ± 0.0046 µg kg⁻¹ scale).
• Cortisol-fed fish showed significantly higher plasma cortisol (80.16 ± 82.58 µg L⁻¹) compared to controls (4.54 ± 9.57 µg L⁻¹) after 30 days.
• A positive correlation between plasma and scale cortisol was observed after 30 days, but not after 90 days. Pigmented scales had higher cortisol concentrations. Health parameters like epidermal thickness, body condition, and parasitic infection correlated with scale cortisol after 30 days.

Conclusions:

• Common dab (Limanda limanda) demonstrably accumulate cortisol in their scales.
• Scale cortisol accumulation appears proportional to plasma cortisol concentrations after 30 days of dietary exposure.
• Scale cortisol analysis offers a promising tool for non-invasive chronic stress assessment in common dab.