Abstract
The domestication of fish species is still in its early stages when compared to terrestrial animals. Although the gap between the time domestication has been underway in terrestrial farm animals and in farmed fish is enormous, there has been a considerable effort towards fish domestication in recent times ( Duarte et al 2007). However, the main component in the domestication process is the generation interval (i.e. the average age of the parent animals at the birth of their offspring—note that this is not the age at maturity). A comparison between land animals and fish may be found in Figure 1.
G eneration intervals may be in the same order of magnitude in terrestrial animals and fish, but they vary immensely for different species in aquaculture , adding a biological layer of complexity to the implementation of welfare standards for such a diverse group of animals.
The effects of domestication on welfare of farmed fishes are complex to study because fish differ from livestock in genetics, physiology and behaviour, and experience different sensory worlds. Consequently, empathy with fish and understanding of their needs becomes more problematic than with land animals. Additionally, the acknowledgement and study of mental dimensions of fish existence is very recent
(Brown 2015) . We discuss that higher levels of domestication in fish do not necessarily correspond to better welfare because (1) artificial selection by the aquaculture industry is mostly focused on production-related traits such as growth, and this selection process may have unknown effects on welfare-related traits; (2) the number of fish species presently farmed (circa 400 ) is 10-fold higher than land animals, rendering the establishment of general welfare guidelines extremely complicated , even because there is immense diversity among fishes in what regards their welfare needs; (3) the current paradigm of the Five Freedoms guiding welfare is out-dated, was designed for livestock and largely considers animals passive with regards to their environment; and (4) there are still severe knowledge gaps in the biology of farmed fishes, especially in welfare-related traits
(Saraiva et al 2019) . The implementation and regu lation of humane fish farming systems should acknowledge
the challenges and specificities of farmed fishes (Saraiva et al 2022), integrating
industry, academia, advocacy groups and policy makers in a constructive dialogue.
References:
Brown, C. (2015). Fish intelligence, sentience and ethics. Animal cognition, 18(1), 1-17.
Duarte, C. M., Marbá, N., & Holmer, M. (2007). Rapid domestication of marine species. Science, 316(5823), 382-383.
Saraiva, J. L., Arechavala-Lopez, P., Castanheira, M. F., Volstorf, J., & Heinzpeter Studer, B. (2019). A global assessment of welfare in farmed fishes: The FishEthoBase. Fishes, 4(2), 30.
Saraiva, J.L., Arechavala-Lopez, P., and Sneddon, L. (2022) The welfare of fish in aquaculture systems. In: Routledge Handbook Of Animal Welfare. Taylor and Francis.