Despite a growing interest in animal welfare in production systems, there remains
a severe scarcity of information pertaining to fish welfare, especially in the case
of commercial fisheries. Fish caught in fixed nets (i.e., gill and trammel nets)
undergo a multitude of stressors from the time of capture to mortality on deck
considered detrimental to their welfare. This study aimed to examine the impact
of gill nets on fish welfare using behavioral and physiological evidence. Four
species were selected, a Mullid and three Sparids. Vitality assessments were
performed onboard fishing vessels by visually assessing the fish welfare
condition through a devised vitality scale. Physiological stress parameters were
evaluated in plasma and correlated with vitality. The rate of decrease in vitality
differed amongst the target species, along with a significant difference in the time
elapsed to their onboard mortalities. Furthermore, our statistical models predicted
that weight, scale loss, fishing depth, and sea surface and atmospheric
temperatures have a significant effect on the time to mortality, and hence, on the
welfare. Lastly, plasma osmolality was found to have a significant negative
relationship with vitality and may be used as a reliable indicator of stress in fish
welfare assessments.
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