Quantification of alizarin red S uptake in coregonid eggs after mass‐marking

Abstract

An easy method to measure the uptake rate of the persistent dye alizarin red S (ARS) during marking of whitefish eggs was established and used to measure the ARS content in three different whitefish species during and at the end of the marking procedure. Those values show that only 6-10% of the ARS in the marking solution will be absorbed by the eggs (0.0061-0.0119 mg per egg). Additional analyses 6, 15 and 36 months after marking showed ARS levels below the response level (<6.9 μg kg-1).

A matter of time—Efficacy of whitefish stocking in a large pre‐alpine lake

“…However, another benthic whitefish species, the Sandfelchen C. arenicolus spawns in shallow areas of ULC at the same time as C. macrophthalmus (Hirsch et al, 2013). This species could benefit from increasingly abundant invasive Quagga mussel Dreissena rostriformis bugensis that was found for the first time in 2016 (Baer, Becke, et al, 2021; Hydra, 2021) and is today the main prey of C. arenicolus (Baer, DeWeber, et al, 2021). Therefore, the density of C. arenicolus might have increased in recent years and if some caught during sampling in 2019 and 2021 were assigned erroneously to C. macrophthalmus , this may have reduced the estimate of stocked C. macrophthalmus .…”

“…Marking at one hatchery (Nonnenhorn) followed the protocol of Eckmann et al (2007). Briefly, the marking solution was prepared in a single circular tank using 2000 L of demineralized water with 1 g L −1 Tris buffer (C 4 H 11 NO 3 ; Sigma‐Aldrich), into which 1 g L −1 of ARS (alizarin red S monohydrate, C 14 H 7 NaO 7 S; Waldeck Chemie) was dissolved (Baer, Becke, et al, 2021; Eckmann, 2003). Eggs from the other five hatcheries were transported to Nonnenhorn and transferred immediately into one of six 200‐L Zug jars.…”

“…Virtual year‐class strength of pelagic whitefish from 1956 to 2015 was calculated using cohort analysis (Kugler, 2022; Thomas & Eckmann, 2007). The total number of annual spawned eggs was also estimated using cohort analysis for the same period (Baer, Becke, et al, 2021). Other variables evaluated to determine how they affected recruitment included: average total mean phosphorous TP (1956–2015) calculated from measurements during winter mixing in February–March (IGKB, 2018; Stich & Brinker, 2010); April water temperature at 5‐m depth estimated from a model described by DeWeber et al (2022); numbers of yearly stocked larvae in ULC (1956–2015) recorded by IBKF; lake‐wide abundance of stickleback (1956–2015) estimated as average annual density of small stickleback‐sized targets in hydroacoustic surveys minus mean density of small fish from 2009 to 2011, when sticklebacks were not yet abundant in the pelagic zone (all years before 2012 were assigned a density of zero, Eckmann & Engesser, 2019; Gugele et al, 2020; Rösch et al, 2018); minimum winter oxygen concentration at 250‐m depth recorded monthly by LUBW (Institute of Lake Research) from 1965 to 2015 (data was not available from 1958 to 1964); and December to March mean of the previous winter's North Atlantic Oscillation (NAO) calculated according to Straile et al (2007).…”

“…Virtual year-class strength of pelagic whitefish from 1956 to 2015 was calculated using cohort analysis (Kugler, 2022;. The total number of annual spawned eggs was also estimated using cohort analysis for the same period (Baer, Becke, et al, 2021). Other variables evaluated to determine how they affected recruitment included: average total mean phosphorous TP A Beverton-Holt stock-recruit relationship (Beverton & Holt, 1993) was used to estimate the expected mean number of recruits (in millions) for a given egg production (in billions):…”