Named for its rudder-like tail fin. Also for its habit of following ships. The rudderfish is dark, almost black. It has a deep, compressed body and large eyes. A fish that looks like it belongs in deep water. Which it does. Juveniles are strikingly patterned with vertical stripes. They are often found near the surface. Sometimes they shelter under floating debris. Adults are more uniformly dark. They live deeper. The large mouth feeds on soft-bodied prey. Salps, jellyfish, small fish and crustaceans. Rudderfish often follow floating debris and jellyfish swarms. They pick off the creatures that gather there. A scavenger of the open ocean. It takes advantage of whatever drifts past. The strategy is opportunistic. It requires little energy. The current does the work. The fish just waits. Closely related to the warehou and bluenose. The flesh is firm and oily. It is sometimes used in fish and chips when other species are scarce. Not a first-choice fish. But a fish that fills the gap. The taste is acceptable. The texture holds up to frying. It serves a purpose in the supply chain. When the preferred catch is low, the rudderfish steps in. It is the understudy that knows the lines. Population trends are poorly understood. Rudderfish are caught as bycatch in trawl and longline fisheries. These target hoki and other mid-water species. No species-specific stock assessment exists for New Zealand waters. The data is sparse. The habitat is remote. Monitoring is difficult. The fish remains a shadow in the records. A dark fish with a rudder tail. It follows ships in the open ocean. It is caught by accident. It is poorly understood. The lack of knowledge is not unusual for deep-water species. But it leaves management blind. Decisions are made without clear numbers. The bycatch continues. The population responds in silence. There is no outcry. No one notices the decline until it is too late. Or perhaps it is stable. No one knows for sure. The uncertainty is the defining feature. It swims on. The rudder turns. The ship moves ahead. The fish keeps pace. It has done this for millennia. It will likely continue. Unless the nets change. Or the prey disappears. Then the pattern breaks. For now, it persists. In the dark. In the deep. Following the lead.