Fig. 2

Lava caves filled with groundwater near Lake Mývatn, which contain small Arctic charr(Salvelinus alpinus). Caves of different sizes and spatial complexity are shown to display the diversity of lava caves present in this area. From top to bottom: main opening of cave 1 in the South of the Haganes area, with unbaited minnow traps laid to catch fish; drone picture of the main circular opening of the largest cave (cave 25) found in the center of Haganes area; view inside a large and complex cave (four openings, cave 5) found in the North of the Haganes area, lava rocks can be seen close to the openings and then mud cover the hard bottom towards the center of the cave. (Photo credits from left to right: Camille Leblanc, Árni Einarsson, Anup Gurung)