Enrichment effects on growth, health, and reproduction in a single clone of the asexual Amazon molly, <i>Poecilia formosa</i>

This study examines the impact of two types of environmental enrichment on the growth of the Amazon molly (<i>Poecilia formosa</i>), a clonal fish species. We investigated the effects of two welfare-related enrichment factors: physical enrichment (presence of a halfpipe PVC and gravel substrate, E) and social enrichment (presence of visible neighbor fish, N). Fish were divided into four treatment groups: (1) both physical and social enrichment (EN), (2) no physical enrichment but social enrichment (nEN), (3) physical enrichment without social enrichment (EnN,), and (4) no enrichment (nEnN). Results showed that individuals, which received both types of enrichment, exhibited faster growth rates and lower early life mortality compared to the other groups, indicating improved health and welfare. However, this initial advantage did not persist into adulthood, suggesting that the benefits of enrichment may be stage specific. These findings highlight the importance of environmental factors in promoting welfare in a particular species, especially during early developmental stages. This study may have implications for early life-stage fish research indicating that some environmental factors may play a role in enhancing growth, reproductive competence, and reduced mortality. Enrichment effects on growth, health, and reproduction in a single clone of the asexual Amazon molly, <i>Poecilia formosa</i>.