Geology topics

Carson Jeffres

Publications and source records attributed to Carson Jeffres.

2 recordsLinked to original sources

USGS2026

Fatty acid profiles recorded in ocean prey and California salmonine eggs reveal maternal ocean diets linked to thiamine deficiency

Following the principle ‘you are what you eat’, fatty acid signatures (FASs) of adult fish tissues, when compared with those of potential prey, can link diet to nutritional status. In 2020, thiamine (vitamin B 1 ) deficiency was diagnosed for the first time in multiple anadromous salmon populations in California. However, direct information linking ocean diet to thiamine status in marine-feeding salmonines is typically unavailable. This research aimed to link diet composition and egg total thiamine concentration of anadromous Chinook salmon, coho salmon and steelhead using FAS analysis. From 2020 to 2022, unfertilized eggs from these California salmonine species were collected alongside key forage species from the Pacific Ocean. FASs in eggs and prey were quantified using gas chromatography/mass spectrometry and total thiamine concentrations were quantified using high-performance liquid chromatography. Eggs rich in oleic acid (18:1n-9) reflected a diet dominated by Pacific herring and exhibited higher total thiamine concentrations. Conversely, eggs rich in eicosapentaenoic acid (20:5n-3) indicated a diet dominated by northern anchovy or euphausiid krill and were more likely to have low total thiamine concentrations. Polyunsaturated fatty acid proportions and the egg unsaturation index were strongly negatively correlated with egg total thiamine concentration, emphasizing the importance of lipid quality over quantity as a driver of egg thiamine concentration. This study highlights the utility of FASs for tracking the impacts of a changing ocean prey base on diet and underscores how dietary shifts can directly impact egg thiamine status in anadromous salmonines.

California↗

USGS2025

Widespread thiamine deficiency in California salmon linked to an anchovy-dominated marine prey base

Thiamine (vitamin B 1 ) deficiency in marine systems is a globally significant threat to marine life. In 2020, newly hatched Chinook salmon ( Oncorhynchus tshawytscha ) fry in California’s Central Valley (CCV) hatcheries swam in corkscrew patterns and died at unusually high rates due to a lack of this essential vitamin. We subsequently investigated the impacts and causes of thiamine deficiency in California’s anadromous salmonids. Our laboratory studies defined the relationship between thiamine concentrations in Chinook salmon eggs and early life-stage survival in offspring; we used these data to develop a model that estimated 26 to 48% thiamine-dependent fry mortality across consecutive years (2020–2021) for winter-run Chinook salmon. We established an egg surveillance effort that found widespread thiamine deficiency in CCV Chinook salmon in 2020 and 2021, and emerging thiamine deficiency in Klamath River and Trinity River coho salmon ( Oncorhynchus kisutch ) in 2021. We determined that thiamine injections into adults raised egg thiamine concentrations above levels found to impact early life-stage survival and swimming behavior. Ocean surveys, prey nutrition, salmon gut contents, and stable isotope data link thiamine deficiency to an ocean diet dominated by a booming population of northern anchovy ( Engraulis mordax ). This forage fish had low thiamine, high lipid, and high thiaminase activity levels consistent with both a thiaminase and oxidative stress hypothesis for causing thiamine deficiency in California salmon. Our research suggests California’s already stressed anadromous salmonids will continue to be impacted by thiamine deficiency as long as their ocean forage base and diet are dominated by northern anchovy.

Proceedings of the National Academy of Sciences↗