A low rate of multiple maternity for pregnant male northern pipefish Syngnathus fuscus

Microsatellite parentage analysis was applied to 22 broods of the northern pipefish Syngnathus fuscus for the first time. The majority of males mated singly, 23% of males mated with two females, and no males mated with more than two females. The arrangement of embryos within the brood pouch of multiply mated males reflects a previously undocumented fill pattern where full‐sib groups are segregated within the pouch by both right and left sides as well as anterior and posterior ends.