Substantial genetic structure among stocked and native populations of the European grayling (Thymallus thymallus, Salmonidae) in the United Kingdom

Abstract

While currently in a state of recovery in the United Kingdom (UK), the grayling (Thymallus thymallus) remains of conservation interest due to its historical decline, socio-economic value and the potential impact of hatchery-reared stock fish on the genetic structure and diversity of wild populations. However, little is known about the levels and distribution of genetic diversity among UK grayling populations. To this end, 27 UK populations of grayling were genotyped across 10 microsatellite loci and sequenced at the mtDNA D-Loop. All populations clustered into four higher-level groups: Northern England, Southern England, Wales, and group consisting of a mixture of native and introduced populations. Ten populations showed evidence of bottleneck or founder effects, and the effective population size (Ne) was low in all populations. In most cases, historical stocking records agreed with the genetic relationships revealed in the study. A D-Loop haplotype network supported the groupings observed in the nuclear data, while phylogenetic inference places the UK populations amongst Central European samples. The combined datasets demonstrate that many of the UK populations can be treated as separate Management Units and we recommend that to preserve population specific genetic diversity, that stocking should be an intervention of last resort. However, if stocking is deemed essential, brood stock should originate from the river to be stocked

Genetic population structure and evidence of genetic homogeneity in populations of the Argentinian silverside Odontesthes bonariensis (Teleostei: Atherinopsidae) inhabiting central and northwestern Argentina

“…Given that genetic variation relates to the effective size of the populations, it also showed the highest values of histo- CC, LCH and CH had Ne <50, which is similar to the estimates of Dawnay et al (2011) for the freshwater fish Thymallus thymallus, in which low values of Ne were found in 19 of the 27 populations studied. Theoretically, values of Ne between 50 and 500 are necessary to minimize the effects of endogamy and maintain genetic variation in the short and long term, respectively (Van Dyke, 2008;Rieman & Allendorf, 2001).…”

Microsatellite Development and First Population Size Estimates for the Groundwater Isopod Proasellus walteri

“…In particular, much effort was devoted to highlight the effect of environmental variables [23] and anthropogenic disturbances such as dams [24] or restocking practices [25,26] on N e . Actinopterygian fishes hence provided a much-needed opportunity to compare approaches and methods to estimate N e [7] or to infer the intraspecific variability of N e (e.g.…”

Roles of discharge and temperature in recruitment of a cold‐water fish, the European grayling Thymallus thymallus, near its southern range limit

“…Most studies on the long-term recruitment drivers of salmonids have focused on salmon and/ or trout, with a paucity of knowledge on other salmonids, such as European grayling, despite these fish often being an important fisheries resource across Europe (Ibbotson et al, 2001), and with apparent declines in many populations in recent years (Dawnay, Dawnay, Hughes, Cove, & Taylor, 2011). Although there have been studies of many aspects of grayling ecology, including their recruitment (reviewed in Ibbotson et al, 2001), these studies have tended to focus on the recruitment process and were of short duration (e.g.…”