Researchers using sediment traps in the Southern Ocean have included fish fecal material in measurements of carbon flux to the deep ocean. Fish feces was found in three out of four sediment trap deployments. The study focused on the sinking flux of particulate matter (carbon) associated with free-drifting icebergs.
Fish feces included as marine carbon – "fecal material from euphausiids (brown cylindrical shape) and ﬁsh (large reddish pellet)", from Smith et al 2011.
Smith, K. L. Jr., et al., Carbon export associated with free drifting icebergs in the Southern Ocean. Deep-Sea Research II (2011), doi:10.1016/j.dsr2.2010.11.027