DOI: 10.5061/dryad.6wwpzgn4p
title: Creating new littoral zones in a shallow lake to forward-restore an aquatic food web

description: Freshwater fish communities typically thrive in heterogenous ecosystems
 that offer various abiotic conditions. However, human impact increasingly
 leads to loss of this natural heterogeneity and its associated rich fish
 communities. To reverse this trend, we need guidelines on how to
 effectively restore or recreate habitats for multiple fish species. Lake
 Markermeer in the Netherlands is a human-created 70,000-ha lake with a
 uniform 4 m-water depth, steep shorelines, high wind-induced turbidity,
 and a declining fish community. In 2016, a forward-looking restoration
 project newly created a 1000-ha five-island archipelago in this degrading
 lake, which offered new sheltered shallow waters and deep sand excavations
 to the fish community. In 2020, we assessed how omnivorous and piscivorous
 fish species used these new habitats by tracking 78 adult fish of five key
 species across local and lake scales. We monitored spring arrival of adult
 fish and assessed local macro-invertebrate and young-of-the-year fish
 densities. Adult omnivorous Cyprinidae and piscivorous Percidae arrived at
 the archipelago in early spring, corresponding with expected spawning
 movements. During the productive summer season, 12 species of
 young-of-the-year fish appeared along the sheltered shorelines, with
 particularly high densities of common roach (Rutilus rutilus) and European
 perch (Perca fluviatilis). This suggests the sheltered, shallow, vegetated
 waters formed new suitable spawning and recruitment habitat for the fish
 community. Despite the highest food densities for adult fish in the
 shallowest habitats (&lt; 2-m), adult fish preferred minimally 2-m
 deep water. After spawning, most Cyprinidae left the archipelago and moved
 long distances through the lake system, while most Percidae remained
 resident. This may be related to (1) high densities of young-of-the-year
 fish as food for piscivores, (2) medium food densities for omnivores
 compared to elsewhere in the lake-system, or (3) the attractiveness of
 30-m deep sand excavations that were newly created and frequently used by
 one-third of all tracked fish. New littoral zones and a deep sand
 excavation constructed in a uniform shallow lake that lacked these habitat
 types attracted omnivorous and piscivorous fish species within four years.
 Both feeding guilds used the littoral zones for reproduction and nursery,
 and notably piscivorous fish became residents year-round.
description: Eighteen different locations at the shorelines of the Marker Wadden archipelago in the Netherlands were sampled
 monthly between May and August 2020.
 Three different taxonomic groups were collected by various sampling
 techniques: zooplankton, macroinvertebrates and young-of-the-year
 fish. Meso-zooplankton densities were
 assessed by filtering 30 L of water through an 80-μm mesh size plankton
 net and condensing the sample into a 50 ml tube. Rotifera densities were
 assessed by filtering 1 L of water through a 30-μm mesh size plankton net
 into a 50 ml tube. Densities of pelagic
 macroinvertebrates in the water column were assessed by placing an open
 metal cylinder (ø 50 cm, 50 cm high) within 5 m from the waterline in the
 water at a depth between 20 and 30 cm and catching all pelagic
 macroinvertebrates in this enclosed area with a small dip net (13 × 10 cm,
 1 mm mesh size). Benthic macroinvertebrates were sampled by taking one
 sediment core (ø 6 cm,
 depth 10 cm) in the metal cylinder and sieving the sample over a 0.72 mm
 mesh. Young-of-the-year (YOY) fish
 catch-per-unit-effort (CPUE) was assessed by means of multiple fishing
 gears that increased in mesh sizes over the season to accommodate for the
 increasing body lengths and swimming speeds of the fish over the season.
 In May, two types of dip nets (21 × 21 cm, mesh 0.5 mm, and 55 × 70 cm,
 3 mm mesh) were used, to which from June until August additional seine
 netting (length 15 m, height 2.5 m, mesh-size 10 mm from knot to knot) was
 added. Sampling always occurred during daytime and at wind speeds
 &lt;4 Beaufort. Data were analysed for spatial and temporal
 variation in generalized linear mixed-effects models as described in the
 two linked publications.
description: # Creating new littoral zones in a shallow lake to forward-restore an
 aquatic food web
 [https://doi.org/10.5061/dryad.6wwpzgn4p](https://doi.org/10.5061/dryad.6wwpzgn4p) ## Description of the data and file structure **Data** Eighteen different locations at the shorelines of the Marker Wadden archipelago in the Netherlands were selected for this study, and sampled monthly between May and August 2020. Three different taxonomic groups were studied: zooplankton, macroinvertebrates and young-of-the-year fish. Meso-zooplankton densities were assessed by filtering 30 L of water through an 80-μm mesh size plankton net, and condensing the sample into a 50 ml tube. Rotifera densities were assessed by filtering 1 L of water through a 30-μm mesh size plankton net into a 50 ml tube. Densities of pelagic macroinvertebrates in the water column were assessed by placing an open metal cylinder (ø 50 cm, 50 cm high) within 5 m from the waterline in the water at a depth between 20 and 30 cm and catching all pelagic macroinvertebrates in this enclosed area with a small dip net (13 × 10 cm, 1 mm mesh size). Benthic macroinvertebrates were sampled by taking one sediment core (ø 6 cm, depth 10 cm) in the metal cylinder and sieving the sample over a 0.72 mm mesh. Young-of-the-year (YOY) fish catch-per-unit-effort (CPUE) was assessed by means of multiple fishing gears that increased in mesh sizes over the season to accommodate for the increasing body lengths and swimming speeds of the fish over the season. In May, two types of dip nets (21 × 21 cm, mesh 0.5 mm, and 55 × 70 cm, 3 mm mesh) were used, to which from June until August additional seine netting (length 15 m, height 2.5 m, mesh-size 10 mm from knot to knot) was added. Sampling always occurred during daytime and at wind speeds &lt;4 Beaufort. **File structure** Excel file with for each taxonomic group a separate sheet with columns including: -       Sampling location, with GPS locations in the meta-data -       Taxonomic information -       Month of sampling in 2020 -       Abundance of the specimens A meta-data sheet with the GPS locations of the sampling locations ## Sharing/Access information This is a section for linking to other ways to access the data, and for linking to sources the data is derived from, if any. Data links to publications in -       Movement Ecology [https://doi.org/10.1186/s40462-023-00405-1](https://doi.org/10.1186/s40462-023-00405-1) -       Science of the Total Environment [https://doi.org/10.1016/j.scitotenv.2023.166768](https://doi.org/10.1016/j.scitotenv.2023.166768 "Persistent link using digital object identifier")