Serum Lipids and the Death of Spawning Pacific Salmon

Abstract

DURING a recent expedition of the R/V Alpha Helix (1968), we had the opportunity to compare blood serum lipids of pink salmon (Oncorhynchus gorbuscha) collected at two points in their spawning migration. Fish were sampled from commercial purse seines near Namu, which is located on the British Columbia coast at the entrance to the Burke Channel; and again 60 miles from the sea in a small freshwater stream (a tributary of Thomsons Creek) near Bella Coola, at the head of the same channel. The fish were spawning at this latter site and were obtained by dip net. The principal difference between the Namu and Thomsons Creek fish was that the latter had undertaken a migration of 60 miles under total fasting conditions. The Namu fish were in good condition while those in the freshwater stream had lost on average one-third of their weight and were close to death. Other studies^1–4 have demonstrated that salmon lose weight during the spawning migration. It is known that lipids are the principal substrate in the energy metabolism offish and that 91 to 96 per cent of the fat reserve in the salmon is utilized during this migration¹. Ultrastructural observations (to be published) confirmed that lipid deposits had disappeared from the back muscle of the salmon after migration.