Blackrider

All of these high mountain lakes are now inhabited by two morphs of Arctic charr: fish of small body size (so called: 'blackriders') are highly numerous in these lakes and large body size fish (so called: 'wildcaught charrs') which are significantly less numerous.

Source: wiktionary

The lake is inhabited by two morphs of Arctic charr (Salvelinus alpinus); small-bodied “blackriders” are very numerous, whereas larger “wild-caught charrs” are less frequent

Source: wiktionary

To rile their professors, South Carolina students staged 'blackrides,' when they blackened their faces, stole the horses of faculty, and galloped about campus while holding flaming torches. After exhausting a horse and drawing a cheering crowd, a 'blackrider' dismounted and slipped into the midst of his fellows to hide from investigation."

Source: wiktionary