Recovery of the crucian carp Carassius carassius (L.): Approach and early results of an English conservation project

Abstract

1. The crucian carp Carassius carassius, a cyprinid fish characteristic of small ponds, is in decline throughout most of its European range, including in England where it is currently thought to be non-native. 2. The present study, undertaken by the Norfolk Crucian Project, reports on reductions in pond populations of crucian carp in Norfolk, eastern England as well as the success of recent introduction/re-introduction efforts in terms of crucian survival, recruitment and growth over the last 10 years. 3. A 72% decline in crucian carp distribution was observed between the 1950s-1980s and the 2010s. Of 18 crucian carp introductions/re-introductions to restored and suitable existing ponds, 17 were successful in terms of survival,

Using DNA metabarcoding to investigate diet and niche partitioning in the native European otter (Lutra lutra) and invasive American mink (Neovison vison)

“…Several fishes were previously detected by morphological spraint analysis or fish surveys but not by DNA metabarcoding, including stone loach, gudgeon (Gobio gobio), ninespine stickleback, ruffe (Gymnocephalus cernua), Lampetra spp., European flounder (Platichthys flesus), rudd (Scardinius erythrophthalmus), common bream, goldfish (Carassius auratus) and common carp (Cyprinus carpio). The common carp and ruffe were initially detected by DNA metabarcoding in agreement with previous morphological studies (Zambrano et al 2006;Sayer et al 2011;Almeida et al 2012;Sayer et al 2020), but removed by our false positive sequence threshold. Other fishes, while not detected in the River Glaven spraints, were nonetheless detected in spraints from the River Hull or Malham Tarn.…”

“…Some medium-sized species were also consumed frequently where they were common, such as the European perch in the River Hull catchment and Malham Tarn, and the crucian carp in the River Glaven catchment, a frequent species in farmland ponds (Sayer et al 2011(Sayer et al , 2020. Conversely, other medium-sized or large species which are abundant at our study sites, such as brown trout, common dace, roach and European eel, seemed to be under-represented in spraints.…”

“…Therefore, smaller fishes that can be consumed whole are often preferred, although habitat conditions and fish abundance also play a role (Ruiz-Olmo et al 2001;Britton et al 2006Britton et al , 2017Remonti et al 2010;Krawczyk et al 2016;Lanszki et al 2016;Martínez-Abraín et al 2019). European bullhead and stickleback species are common at all three of our study sites (Sayer et al 2011(Sayer et al , 2020Almeida et al 2012Almeida et al , 2013Alderton et al 2015;Champkin et al 2017;Harwood et al 2019;Hänfling et al unpublished data), thus their frequent occurrence in spraints may simply reflect their high abundance in the environment.…”

“…Fish survey (seine netting, electrofishing) data from 2000 to 2019 were extracted from the publicly available Environment Agency database (data.gov.uk) for the River Hull and River Glaven catchments. For the River Glaven, additional data were available from the surveys of Harwood et al (2019) and Sayer et al (2020). Fish community data for Malham Tarn were obtained through environmental DNA (eDNA) metabarcoding verified by fishery owners (Hänfling et al 2020) and from fish surveys detailed in Eldridge (2016).…”

Using DNA metabarcoding to investigate diet and niche partitioning in the native European otter (Lutra lutra) and invasive American mink (Neovison vison)

“…The common carp and ruffe were initially detected by DNA metabarcoding in agreement with previous morphological studies(Zambrano et al 2006;Sayer et al 2011;Almeida et al 2012;Sayer et al 2020), but removed by our false positive sequence threshold. Other fishes, while not detected in the River Glaven spraints, were Lampetra planeri), may be due to technical bias that can occur throughout the DNA metabarcoding workflow (see Considerations for molecular scatology).Range expansion of the otter intoMalham Tarn occurred recently in 2009, and only two individuals have established themselves at the site thus far.…”