Seasonal change in activity of abyssal demersal scavenging grenadiers Coryphaenoides (Nematonums) armatus in the eastern North Pacific Ocean

The responses of the grenadier fish Coryphaenoides ( Nematonurus ) armatus to bait deployed on the sea floor at station M in the North Pacific Ocean (34°50′N, 123°00′W; 4,100 m deep) in February and October were compared. In February 1990 and 1992, the first fish arrived after an average time of 25 min and stayed an average of 150 min. In October 1991, the respective times were 15 and 98 min. The faster response in October is correlated with a higher mean swimming speed of 0.0692 m s −1 compared with 0.0262 m s −1 in February. Fish activity was elevated in October following seasonal enrichment to the benthos by downward flux of particulate organic matter from the surface. Grenadier abundance was estimated from arrival times as 325 individuals km −2 , corresponding to a wet weight biomass of 146 mg m −2 or 10.2 mg C m −2 .