Migration patterns of sterlet ( Acipenser ruthenus , Linnaeus 1758) in the Middle Danube assessed by 1 year acoustic telemetry study

Abstract

Summary The sterlet (Acipenser ruthenus, L.) is the last of the five native sturgeon species historically inhabiting the Middle and the Upper Danube. Its population has undergone a large decline, mainly due to the degradation of key habitats, the spawning and feeding grounds, the construction of migration barriers, over‐fishing and poaching. Generally, no information is available about sterlet migration patterns and how they are triggered. Our results, based on direct observations by acoustic telemetry, suggest that sterlet seem to migrate when the water temperature is above 12°C. No pattern is visible in sterlet migrations in connection with the water level. The restricted one‐year life of implanted transmitters does not allow to separate the effects of highly correlated water temperature and the length of the day on sterlet migration. The sterlet tends to spend from three to seven months in the feeding area, from 6 to 8 months in the wintering area and around 2–4 weeks in the spawning area. There is a need for further confirmation of the exact location of these habitats in the Middle Danube. A description of the migration patterns and identification of environmental cues affecting its migration are an important part of effective sterlet conservation and management.

Bayesian modelling suggests that the sterlet (Acipenser ruthenus, Linnaeus 1758) population is ageing in the middle Danube River

“…It is worth mentioning that when conducting a recent study on migration patterns of sterlet the average weight of the specimen was 4.8 kg. The heaviest fish observed in the field reached almost twice (8 kg) that previously reported (Kubala, Farský & Pekárik, 2019). For comparison, the maximum weight that can be found in the published literature is 16 kg (Berg, 1964).…”

“…It is highly unlikely that many fish grow beyond 8 kg under natural conditions, as the genetic predisposition of the maximum size of sterlet is 1.2 m. We propose that establishing an upper weight threshold should be seriously considered for future models. For our model design, we used the most recent record of the heaviest sterlet (8 kg) from natural conditions observed in the field during the previous telemetry study (Kubala, Farský & Pekárik, 2019).…”

Development of a TaqMan qPCR protocol for detecting Acipenser ruthenus in the Volga headwaters from eDNA samples

“…No amplification was observed from any eDNA samples corroborating the results of Lecaudey et al (2019). The non-detection could be caused by seasonal migrations during summer months (Kubala et al 2019, Sorokin et al 2002, orvery low abundances ("rarely caught andin single instances"- Sorokin et al 2002), that may have led to eDNAconcentrations below the detection threshold of the assay. One sampling replicate consisted of 250 ml of filtered water and replicates were kept separate for analyses.…”

How do suboptimal temperatures affect polyploid sterlet Acipenser ruthenus during early development?

“…However, although the spawning cues in A . ruthenus have only ever been poorly studied, water temperature is very likely not the only factor affecting reproduction since the timing of spawning migration and/or spawning itself might also be correlated with water levels, turbidity (Kalmykov et al ., 2010) and the photoperiod (Kubala et al ., 2019) in this species. The latter factor was identified as the most crucial factor affecting spawning timing in shortnose sturgeon A .…”