Model for estimating thiamine deficiency-related mortality of Atlantic salmon (Salmo salar) offspring and variation in the Baltic salmon M74 syndrome

Pekka J Vuorinen,Mervi Rokka,Soili Nikonen,Esa-Pekka Juntunen,Tiina Ritvanen,Petri Heinimaa,Marja Keinänen

doi:10.1080/10236244.2021.1941942

Abstract

ABSTRACT Thiamine (vitamin B1) deficiency of salmonines, caused by an abundant lipid-rich fish diet and consequently, the abundance of polyunsaturated fatty acids, is called the M74 syndrome in the Baltic Sea. Because of its deleterious effects on wild Atlantic salmon (Salmo salar) stocks and progeny production in fish cultivation, a model was developed to derive the annual female-specific mortality percentages of yolk-sac fry (YSFM) from the free thiamine concentrations of unfertilized eggs. In years with a high M74 incidence, thiamine-deficient females were larger, with a larger condition factor (CF) than non-M74 females. Otherwise, M74 females were generally smaller. The mean CF of M74 females was in most years higher than that of non-M74 females. The model compiled enables the cost-effective estimation of YSFM of individual female salmon, without the incubation of eggs and hatched yolk-sac fry for several months, thus benefitting the management of salmon stocks and their efficient utilization.

Highlights

Monitoring of M74 in Atlantic salmon (Salmo salar L.) ascendants has been performed for the Rivers Simojoki, Tornionjoki, and Kemijoki, all of which drain into the Bothnian Bay of the Gulf of Bothnia, and for the River Kymijoki, which flows into the Gulf of Finland (Figure 1)
Yolk-sac fry mortality (YSFM), proportions of females with partial M74 mortality among their offspring (M74 females) and those females whose offspring all died of M74 [M74 (100%) females], and the median free thiamine (THIAM) concentration in unfertilized eggs of salmon from the Bothnian Bay rivers (Rivers Simojoki, Tornionjoki, and Kemijoki) during the 1985/1986–2019/2020 reproductive periods
The variation of M74 is presented in Figure 2 as yolk-sac fry mortality (YSFM), proportions of M74 females, and those females whose offspring all died of M74, and as the median THIAM concentration in eggs, for BB salmon during 1985/1986–2019/2020

Summary

Introduction

Salmonines suffer from thiamine (vitamin B1) deficiency caused by feeding abundantly on lipid-rich fish and the abundance of n-3 polyunsaturated fatty acids (n-3 PUFAs) (Keinänen et al 2012; Futia et al 2019). Thiamine, which as the thiamine pyrophosphate (TPP) derivative is needed as a coenzyme in all enzymatic reactions of oxidative metabolism yielding ATP (Lonsdale and Marrs 2019) and in fatty acid metabolism (Casteels et al 2007), is depleted in the peroxidation reactions of PUFAs (Gibson and Zhang 2002; Depeint et al 2006). High dietary fish-based lipid content increases both the lipid and n-3 LC-PUFA content of fatty predatory fish species, and the susceptibility of their tissues to perox idation reactions (Alvarez et al 1998; Kjær et al 2008)

Methods

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Discussion

Conclusion