204 NPAFC Salmon Tagging

Figure 1. Sea temperature (°C on left axis, red line) and depth (m on right axis, blue line) data from TD 7517. Chum salmon released in the Bering Sea (175°03’W, 55°00N) on 6/30/04 and recovered on Sakhalin Island, Russia, on 10/5/04.

To date, 50 DSTs have been returned from this program, mostly from chum (n=25) and sockeye (n=12) salmon. Almost all were from maturing fish released in summer and fall and came primarily from Japan (21), Russia (13), and western Alaska (10). New types of data acquired include the first overwintering marine data from Pacific salmon (two years of sea temperature and depth data from a Yukon River Chinook salmon) and the first salinity data from a migrating Pacific salmon.

Depth data confirm that Chinook and chum salmon have deeper vertical distributions (average daily maxima: Chinook: 130 m; chum: 58 m) than those of sockeye (22 m), pink (37 m), and coho salmon (46 m). Temperature ranges varied widely among water masses traversed by maturing salmon, while maximum daily depths remained fairly uniform.

This indicates that salmon chose maximum depths and not temperature ranges, and that usual depths of maturing salmon may remain relatively constant across water masses and ocean areas. The results of this scientific data collection project are preliminary.

Figure 2. Sea temperature (°C on left axis, red line), depth (m on right axis, blue line), and salinity (psu, on second right axis, green line) data from CTD 1899. Chinook salmon released in the Bering Sea (175°08’W, 54°50N) on 6/8/06 and recovered in the Yukon River on 6/30/06.