▁dawn . ▁Only ▁males ▁tend ▁to ▁under go ▁these ▁migr ations . ▁Ju ven ile ▁H . ▁anom ala ▁often ▁inhab it ▁different ▁positions ▁( us ually ▁higher ) ▁in ▁the ▁water ▁column ▁than ▁adult s , ▁possibly ▁to ▁avoid ▁can n ib al ism . ▁Being ▁more ▁transparent , ▁ju ven iles ▁may ▁be ▁less ▁at ▁risk ▁of ▁fish ▁pred ation ▁than ▁adult s . ▁The ▁adult s ▁are ▁fast ▁sw imm ers , ▁moving ▁at ▁several ▁cent imet res ▁per ▁second ▁when ▁al ar med . ▁Blo ody - red ▁my s ids ▁generally ▁avoid ▁areas ▁where ▁other ▁my s id ▁species ▁are ▁found . ▁Their ▁t endency ▁to ▁aggregate ▁creates ▁locally ▁dense ▁sw ar ms ▁up ▁to ▁several ▁square ▁meters ▁in ▁area . ▁During ▁day light ▁hours , ▁especially ▁in ▁late ▁summer , ▁these ▁re dd ish ▁sw ar ms ▁can ▁be ▁observed ▁in ▁the ▁sh adows ▁of ▁pi ers , ▁boats , ▁or ▁break w alls ; ▁at ▁night , ▁the ▁sw ar ms ▁dis per se . ▁The ▁species ▁is ▁also ▁reported ▁to ▁spend ▁day light ▁hours ▁hiding ▁in ▁rock y ▁cre v ices ▁and ▁b ould er ▁cav ities . ▁ ▁Life ▁history ▁H . ▁anom ala ▁bre eds ▁from ▁April ▁to ▁September ▁/ ▁October . ▁Sex ual ▁m atur ity ▁occurs ▁in ▁ 4 5 ▁days ; ▁life ▁span ▁is ▁about ▁ 9 ▁months . ▁Fem ales ▁become ▁ov iger ous ▁at ▁ ▁and ▁produce ▁ 2 ▁to ▁ 4 ▁bro ods ▁per ▁year . ▁Bro