Cryptic persistence and loss of local endemism in <scp>L</scp>ake <scp>C</scp>onstance charr subject to anthropogenic disturbance

Baer, Jan; Schliewen, Ulrich K.; Schedel, Frederic D. B.; Straube, Nicolas; Roch, Samuel; Brinker, Alexander

doi:10.1002/eap.2773

Cited by 3 publications

(1 citation statement)

References 64 publications

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“…However, lake deep-water habitats do not always have low fish density, and some may possess a considerable proportion of total abundance or biomass [ 40 ]. It is desirable to obtain records of rare and sensitive deep-water species, and, in Lake Constance, this is particularly true of the endemic deep-water char [ 87 , 88 ], rediscovered in 2014 and likely to be vulnerable to the effects of climate change. The increased thermal stratification caused by rising water temperatures can impede water turnover [ 4 ] and exacerbate the risk of hypoxia in deep zones, posing a clear threat to this temperature- and oxygen-sensitive salmonid [ 89 , 90 ].…”

Section: Discussionmentioning

confidence: 99%

Obtaining accurate population estimates with reduced workload and lower fish mortality in multi-mesh gillnet sampling of a large pre-alpine lake

Bader,

Gaye-Siessegger,

Scholz

et al. 2024

PLoS ONE

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The EU Water Framework Directive requires monitoring of the ecological status of lakes, with fish as a relevant class of biotic quality indicator, but monitoring fish populations in large lakes is demanding. This study evaluated use in Lake Constance of a novel multi-mesh gillnet modified to reduce catch numbers. In direct comparison with conventional European Committee for Standardization (CEN) nets we achieved 48% reduction in fish mortality with 38% less labour for tasks directly influenced by fish catch numbers, while maintaining comparable species composition and catch per unit effort. Comparison of mesh sizes indicated no significant reduction in species detection in area-reduced panels of the small mesh sizes, while total observed species richness was greater when using the modified nets. Differences in benthic species communities among depth strata were common, while those of pelagic zones were more homogeneous and did not differ significantly with depth. Catches of different net types from the same depth stratum did not exhibit significant differences. The dominance structure of the most common species, relevant to lake assessment, was similar in catches of both net types, suggesting overall superiority of the modified nets in Lake Constance. Sampling conducted according to standard European CEN protocol, while deploying 60% fewer nets, yielded sufficiently precise abundance estimates for monitoring shallow areas of the benthic zone. A 50% difference in the abundance of dominant species was detected among sampling events with a certainty of 95%. The sample did not provide comparable accuracy in deep benthic strata or the pelagic zone, but was adequate to record complete inventories of species present. Based on this trial data, a new stratified sampling design is proposed for monitoring large lake fish communities for ecological assessment. Depth-dependent fish communities were used to calculate the required number of nets, which resulted in a 69% reduction for the entire lake compared to the CEN calculation method. Using the modified nets increases the feasibility of performing WFD surveys, by reducing effort and cost, while the simultaneous halving of fish mortality minimises the negative impact of fish surveys.

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Section: Discussionmentioning

confidence: 99%

Obtaining accurate population estimates with reduced workload and lower fish mortality in multi-mesh gillnet sampling of a large pre-alpine lake

Bader,

Gaye-Siessegger,

Scholz

et al. 2024

PLoS ONE

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Cryptic persistence and loss of local endemism in Lake Constance charr subject to anthropogenic disturbance

Baer¹,

Schliewen

Schedel

et al. 2022

Ecological Applications

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In the welcome circumstance that species believed extinct are rediscovered, it is often the case that biological knowledge acquired before the presumed extinction is limited. Efforts to address these knowledge gaps, in particular to assess the taxonomic integrity and conservation status of such species, can be hampered by a lack of genetic data and scarcity of samples in museum collections. Here, we present a proof-of-concept case study based on a multidisciplinary data evaluation approach to tackle such problems. The approach was developed after the rediscovery, 40 years after its presumed extinction, of the enigmatic Lake Constance deep-water charr Salvelinus profundus.Targeted surveys led to the capture of further species and additional sympatric normal charr, Salvelinus cf. umbla. Since the lake had been subject to massive stocking in the past, an evaluation of the genetic integrity of both extant forms was called for in order to assess possible introgression. A two-step genomic approach was developed based on restriction site associated DNA (RAD).Diagnostic population genomic (single nucleotide polymorphism [SNP]) data were harvested from contemporary samples and used for RNA bait design to perform target capture in DNA libraries of archival scale material, enabling a comparison between extant and historic samples. Furthermore, life history traits and morphological data for both extant forms were gathered and compared with historical data from the past 60-120 years. While extant deep-water charr matched historical deep-water specimens in body shape, gill raker count, and growth rates, significant differences were discovered between historical and extant normal charr. These resulted were supported by genomic analyses of contemporary samples, revealing the two extant forms to be highly divergent. The results of population assignment tests suggest that the endemic deep-water charr persisted in Lake Constance during the eutrophic phase, but not one of the historical genomic samples could be assigned to the extant normal charr taxon. Stocking with non-endemic Jan Baer and Ulrich K. Schliewen contributed equally to this work.

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Intra-lake origin and rapid expansion of invasive pelagic three-spined stickleback in Lake Constance

Dahms,

Roch,

Elmer

et al. 2024

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The rapid expansion of three-spined stickleback (Gasterosteus aculeatus Linnaeus, 1758 (Perciformes, Gasterosteida)) in the pelagic zone of Lake Constance, Central Europe, since 2012 contributed to stark ecosystem-wide effects, such as food-web shifts and declines in native biodiversity, including commercially important fish species. Yet, the origin of this invasive pelagic population remains unclear. Using RAD-sequencing of Lake Constance sticklebacks, we show that the pelagic Lake Constance population likely arose recently within the lake, potentially from the littoral population. We did not detect any substantial genome-wide genetic differentiation between individuals from different habitats, supporting a recent origin of the pelagic population and/or ongoing gene flow. This is further supported by minimal differences in meristic and morphometric traits. However, we also identified multiple outlier loci between littoral and pelagic individuals across the genome, potentially suggesting early signs of adaptation despite high connectivity. In this study, we provide an important example of rapid within-lake ecological diversification of an invasive species from standing genetic variation. Ultimately, our findings will have major implications for the management of invasive pelagic stickleback, as they indicate that the stickleback population has to be managed as a whole and that management efforts cannot only focus on the hyper-abundant pelagic population.

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Cryptic persistence and loss of local endemism in Lake Constance charr subject to anthropogenic disturbance

Cited by 3 publications

References 64 publications

Obtaining accurate population estimates with reduced workload and lower fish mortality in multi-mesh gillnet sampling of a large pre-alpine lake

Obtaining accurate population estimates with reduced workload and lower fish mortality in multi-mesh gillnet sampling of a large pre-alpine lake

Cryptic persistence and loss of local endemism in Lake Constance charr subject to anthropogenic disturbance

Intra-lake origin and rapid expansion of invasive pelagic three-spined stickleback in Lake Constance

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