Why guppies? Two they showed increase aggression in the guppies. Did they really need to see that to know that.... The Tren guppies mating was sheaky "coercive " really did they peer pressure them or slip them a Mickey ?

Chemosphere. 2017 Nov;187:286-293. doi: 10.1016/j.chemosphere.2017.08.125. Epub 2017 Aug 31.
The agricultural contaminant 17β-trenbolone disrupts male-male competition in the guppy (Poecilia reticulata).

Tomkins P1, Saaristo M2, Bertram MG3, Tomkins RB4, Allinson M5, Wong BBM3.
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Abstract
Despite a growing literature highlighting the potential impact of human-induced environmental change on mechanisms of sexual selection, relatively little is known about the effects of chemical pollutants on male-male competition. One class of environmental pollutant likely to impact male competitive interactions is the endocrine-disrupting chemicals (EDCs), a large and heterogeneous group of chemical contaminants with the potential to influence morphology, physiology and behaviour at minute concentrations. One EDC of increasing concern is the synthetic, androgenic steroid 17β-trenbolone, which is used globally to promote growth in beef cattle. Although 17β-trenbolone has been found to cause severe morphological and behavioural abnormalities in fish, its potential impact on male-male competition has yet to be investigated. To address this, we exposed wild male guppies (Poecilia reticulata) to an environmentally realistic concentration of 17β-trenbolone (average measured concentration: 8 ng/L) for 21 days using a flow-through system. We found that, in the presence of a competitor, 17β-trenbolone-exposed males carried out more frequent aggressive behaviours towards rival males than did unexposed males, as well as performing less courting behaviour and more sneak (i.e., coercive) mating attempts towards females. Considering that, by influencing mating outcomes, male-male competition has important consequences for population dynamics and broader evolutionary processes, this study highlights the need for greater understanding of the potential impact of EDCs on the mechanisms of sexual selection.