# Stress Induced by Fishing in Common Octopus (Octopus vulgaris) and Relative Impact on Its Use as an Experimental Model

## TL;DR

This study examines how fishing affects the stress levels of common octopuses used in research and suggests ways to improve their welfare.

## Contribution

The study introduces new welfare biomarkers to assess stress in octopuses caused by fishing, aiming to improve research reliability.

## Key findings

- Fishing causes significant physiological stress in common octopuses, as shown by changes in gene expression.
- Morphological stress signals and gene expression levels (ER, CAT, HSP70) are affected by fishing methods.
- An acclimation period after fishing is recommended to improve octopus welfare and research outcomes.

## Abstract

The common octopus (Octopus vulgaris) is a fascinating marine animal known for its advanced nervous system and complex behaviors, making it an important model for both ethological and molecular research. Unlike other research animals like zebrafish, octopuses are not farmed, so they must be collected from the wild for studies. This study investigated how fishing impacts the welfare of O. vulgaris used in research. We compared O. vulgaris caught using artisanal pots in the ‘Regno di Nettuno’ Marine Protected Area with individuals subsequently kept under controlled conditions. We examined both morphological stress signals and the expression of stress-related genes—estrogen receptor, catalase, and heat shock protein—and we found that fishing induces significant changes in gene expression, reflecting physiological stress. Our main goal was first to evaluate the stress impact of fishing on the octopuses using a new set of welfare biomarkers. The second is to improve the octopuses’ welfare, supporting the researchers in their behavioral studies and avoiding data misinterpretation due to the stress impact of fishing. These findings emphasize the need for an appropriate evaluation of the animals using welfare biomarkers after fishing to improve their welfare and ensure more reliable scientific results.

The common octopus (Octopus vulgaris), among coleoid cephalopods, has evolved the most complex nervous system and sophisticated behaviors. Historically, O. vulgaris was a key animal model for neurophysiology research, and today, it is studied for its genomic innovations. However, unlike other models, there is no octopus farming for research, so specimens must be collected from the wild. This study assessed the impact of fishing on octopuses used in research, considering those caught using artisanal pots in the ‘Regno di Nettuno’ Marine Protected Area, Ischia (NA). To evaluate fishing stress, we identified morphological stress indicators such as chromatophore pattern and posture, and three potential molecular markers, estrogen receptor (ER), catalase (CAT), and heat shock protein (HSP70). We measured the percentage of stress signals shown by fished specimens and analyzed their differential gene expression. The transcriptional levels of octopuses caught using traps were compared to control specimens acclimated in captivity. Results indicated fluctuations in gene expression due to fishing stress. These findings suggest that an acclimation period after the stress event of fishing is crucial for ensuring the welfare of octopuses used in research, thus enhancing the quality of physiological and ethological studies.