Gasterosteus aculeatus, Linnaeus, 1758

Alexander, Timothy & Seehausen, Ole, 2021, Diversity, distribution and community composition of fish in perialpine lakes – “ Projet Lac ” synthesis report, Eawag: Swiss Federal Institute of Aquatic Science and Technology : 140-141

Also not native to Switzerland, Gasterosteus aculeatus

was recorded in lakes Constance (Upper and Lower lakes), Biel and Lucerne. G. aculeatus was first recorded in the Lake Constance catchment in 1870 in streams on the Austrian side of the lake (see and references in [174]). Genetic analyses suggest that the G. aculeatus in Lake Constance derive mostly from a genetic lineage found in the Baltic drainage (Poland) [172]. Gasterosteus across the middle of Switzerland, such as those caught in lake Biel, are a hybrid mixture of the native upper Rhine and non-native Baltic lineages of G. aculeatus , as well as the non-native middle Rhone lineage of G. gymnurus [175].

[173]

The Gasterosteus aculeatus of Lake Constance, and especially those of Upper Lake Constance, were far more abundant, larger and were found in a wider range of lake habitats than stickleback caught in the other lakes sampled by Projet Lac ( Table 11 , Figure 52 ). More than 2,500 G. aculeatus were recorded in the littoral zone, benthic zone and pelagic zones of Upper Lake Constance, to around 45 meters deep. This species formed 96% of the number of fish and 30% of the biomass caught in the CEN pelagic nets in Upper Lake Constance and formed around 50% of the fish caught in the vertical gillnets (volume-weighted, whole-lake NPUE).The G. aculeatus of Upper Lake Constance have many and large bony plates covering the entire side of their body and thereby resemble both their freshwater-Baltic and marine ancestors. Most other lineages of G. aculeatus reduced their number of bony plates as they adapted to freshwater habitats, such as streams, rivers, small lakes or the littoral zone of larger lakes [177]. However, freshwater lineages of G. aculeatus in the Baltic [176], as well as several other lineages around the world have maintained the full set of bony plates. This may provide them with an adaptive advantage in the habitats of large lakes where piscivorous fish are the dominant predators [180]. The strong and highly developed armour of the Upper Lake Constance G. aculeatus , inherited from their marine ancestors, may be part of the reason why they are able to colonise the pelagic zone of such a large waterbody.

[176]

[178, 179]

Gasterosteus aculeatus were also abundant in the pelagic zone of Lower Lake Constance, constituting almost 65% of fish caught in the CEN pelagic nets. G. aculeatus caught in Lower Lake Constance were on average 2 cm smaller than those caught in the Upper Lake (average total length 47 mm compared to 67 mm).The smaller body size of G. aculeatus in Lower Lake Constance meant that very few were caught in the vertical nets in this lake. Analyses of gillnet mesh size selectivity show that the smallest mesh size of the vertical nets (10 mm) only starts to become efficient at catching stickleback over 60 mm in length.The smaller size of the stickleback in the Lower Lake therefore resulted in very few of this species being caught in this vertical net protocol.

Figures

Figure 52: Stickleback were dramatically larger in Upper Lake Constance compared to other lakes. Length frequency distribution of all Gasterosteus spp caught in Projet Lac. Scaled photos on the right show one of the larger individuals from each lake.