Landlocked Fall Chinook Salmon Maternal Liver and Egg Thiamine Levels in Relation to Reproductive Characteristics

Abstract

Object: Landlocked fall Chinook Salmon Oncorhynchus tshawytscha in Lake Oahe, South Dakota, typically experience poor reproductive success. Introduction: Salmon diets consist of rainbow smelt Osmerus mordax and other potentially thiaminase-containing fish that could impact reproduction. Methods: The thiamine levels of spawning female Salmon, eggs, and reproductive characteristics, were measured in 2000, 2001, 2002, 2003, and 2005. Results: Thiamine concentrations varied significantly from year-to-year, with the highest mean values recorded in 2001 at 8.70 nmol/g in maternal livers and 28.80 nmol/g in eggs. Most of the thiamine in the eggs was present as free thiamine, while most of the thiamine in maternal livers was present as thiamine pyrophosphate. The lowest recorded egg total thiamine level was 2.75 nmol/g in 2000. Egg survival to hatch ranged from 20.7% in 2005 to 35.4% in 2002, and was not correlated to egg thiamine levels. Twenty-two spawns experienced total mortality prior to hatch, and had significantly lower egg free thiamine and total thiamine concentrations than eggs from the 77 successful spawns. The eggs from spawns with total mortality were also significantly smaller than those eggs from spawns that did survive, and were produced by females that weighed significantly less. Several small, but significant, correlations were observed between egg size and egg thiamine levels, and female size and liver thiamine. There was also a significant negative correlation between the number of eggs per spawning female and egg thiamine pyrophosphate, liver thiamine monophosphate, and liver total thiamine levels. Conclusion: In general, Lake Oahe Chinook Salmon eggs show little indication of thiamine deficiency in the years sampled, indicating other factors are likely responsible for poor egg survival.