Life history of anadromous burbot (Lota lota, Linneaus) in the brackish Baltic Sea inferred from otolith microchemistry

Abstract

Strontium to calcium (Sr:Ca) and barium to calcium (Ba:Ca) ratios were quantified in 74 otoliths of brackish water-living burbot Lota lota, collected from two regions in the eastern Baltic Sea. Considerable amount of life history plasticity was observed. Ninety-six per cent of analysed burbot were of freshwater origin; only three specimens displayed signs of hatching in low-salinity (1-2) estuarine environment. Most of the juveniles emigrated from freshwater during late winter and spring the next year after birth, while nine individuals did so at the age of 2-3 months. Age and length at maturity (as determined by first freshwater spawning migration) varied from 2-6 years and 189-540 mm, respectively, with most of burbot maturing during the second or third year of life. It is hypothesised that the bulk juvenile downstream migration is triggered by high-flow conditions as evidenced by Ba: Ca peak around the point of freshwater exit. This study provides new information on burbot life history.

Evidence for an autumn downstream migration of Atlantic salmon Salmo salar (Linnaeus) and brown trout Salmo trutta (Linnaeus) parr to the Baltic Sea

“…A continuous line scan was traced from the core (excluding the primordium) to dorsal edge of the otolith. Data were handled following the methods of Miller (2007) as described in Rohtla et al (2014).…”

Life‐history characteristics of ide Leuciscus idus in the Eastern Baltic Sea

“…The strontium‐to‐calcium ratio (Sr:Ca) is the most frequently used chemical marker because the Sr:Ca ratio in fresh waters is usually several times lower than sea water (Kraus & Secor ; Rohtla et al . ). This allows the movements of diadromous species to be tracked because the ambient Sr:Ca levels are recorded in the otoliths (Shiao et al .…”

“…; Rohtla et al . ). The barium‐to‐calcium ratio (Ba:Ca) is often used as an additional marker for interpreting Sr:Ca profiles, but with mixed results (Crook et al .…”

“…; Rohtla et al . ; Smith & Kwak ). By contrast to Sr:Ca, the Ba:Ca ratio is generally enriched in fresh waters and decreased in sea waters.…”

Do sea trout Salmo trutta parr surveys monitor the densities of anadromous or resident maternal origin parr, or both?

“…Data reduction to Sr:Ca in mmol/mol was achieved following the methods ofMiller (2007) as described inRohtla et al (2014).An individual fish was classified as being of anadromous maternal origin if the mean Sr:Ca core value (before the abrupt decrease;Figure 2b) was higher than the mean + 2 SD of the Sr:Ca natal value (Sr:Ca natal ) for the same specimen(Berejikian, Campbell & Moore, 2013). Individual thin sections were glued onto standard glass slide and stored in clean plastic bags for later analysis.…”