Erlend Haarberg / Bull European elk / Moose (Alces alces) walking, Sarek National Park, Sweden, September

Luke Massey / Giant otter (Pteronura brasiliensis) feeding on a catfish (Loricariidae) with Cocoi heron (Ardea cocoi) scavenging remnants, Rio Cuiaba, Brazil

Remi Masson / Group of Black bullhead (Ameiurus melas) shoaling to protect themselves against predators, River Rhone, Rhone-Alpes, France, July.

Remi Masson / Group of Wels catfish (Silurus glanis) gathered in the River Rhone, France, August.

Anup Shah / Marabou storks (Leptoptilos crumeniferus) feeding on catfish in waterhole, wide angle view. Maasai Mara National Reserve, Kenya.

Shane Gross / Striped catfish (Plotosus lineatus) school in seagrass bed, feeding on Algae growing on Seagrass blades. Manado, North Sulawesi, Indonesia.

Tony Wu / Striped catfish (Plotosus lineatus), school of juveniles feeding on cloud of plankton at night. Ariake Sea, Japan. September.

Jurgen Freund / Striped catfish (Plotosus lineatus) schooling between boats docked at pier and litter on sea floor, taken with fisheye lens. Ambon Island, Maluku, Indonesia. 2018.

Jurgen Freund / Striped catfish (Plotosus lineatus) schooling between boats docked at pier and litter on sea floor. Ambon Island, Maluku, Indonesia. 2018.

Pascal Kobeh / Black seacatfish (Galeichthys ater) Kwazulu-Natal, South Africa

Pascal Kobeh / Black seacatfish (Galeichthys ater) Kwazulu-Natal, South Africa

Remi Masson / Group of Wels catfish (Silurus glanis) a tthe bottom of a river. River Loire, Indre-et-Loire, France. October.

Remi Masson / European catfish (Silurus glanis) in the middle of a school of Fish (common bleak). River Loire, Indre-et-Loire, France. October.

Remi Masson / Group of Wels catfish (Silurus glanis) at the bottom of a river. River Loire, Indre-et-Loire, France. October.

Remi Masson / Giant wels catfish (Silurus glanis), longer than two meters, swimming above the bottom of the lake of Neuchatel, Switzerland.

Brandon Cole / Striped catfish (Plotosus lineatus) shoal, Egypt, Red Sea.

Michel Roggo / Wels catfish (Silurus glanis), on the bed of the Aare river, with Zebra mussel (Dreissena polymorpha) Brugg, Canton of Berne, Switzerland. October. Photographed for The Freshwater Project.

Georgette Douwma / Striped catfish (Plotosus lineatus) shoal, Bali, Indonesia.

Fred Olivier / Striped catfish (Plotosus lineatus) school, Ningaloo Reef, Solomon Islands.

David Hall / Striped eel catfish (Plotosus lineatus), shoal of juveniles. Komodo, Indonesia.

Georgette Douwma / Kaleidoscopic image of Striped catfish (Plotosus lineatus) school feeding on sea bed. West Papua, Indonesia.

George Sanker / Great blue heron (Ardea herodias) with Catfish (Siluriformes) in beak, at dusk. Myakka River State Park, Florida, USA. February. February.

George Sanker / Great blue heron (Ardea herodias) walking with Catfish (Siluriformes) in beak, at dusk. Myakka River State Park, Florida, USA. February. February.

George Sanker / Double-crested cormorant (Phalacrocorax auritus) feeding on Catfish (Siluriformes). Myakka River State Park, Florida, USA. February.

Pascal Kobeh / Wels catfish (Silurus glanis) on the bottom of the river. Its face has a scar probably caused by a fishing hook. Cher River, Loir-et-Cher Department, France

Pascal Kobeh / Two Wels catfish (Silurus glanis) on the bottom of a river. The one on the foreground has a scar on its face probably caused by a fishing hook, Cher River, Loir-et-Cher Department, France

Cyril Ruoso / Wels catfish (Silurus glanis) group gathered in river bed. Loire river, France. November.

Cyril Ruoso / Wels catfish (Silurus glanis) Loire river, France. November.

Cyril Ruoso / Wels catfish (Silurus glanis) Loire river, France. November.

Cyril Ruoso / Wels catfish (Silurus glanis) Loire river, France. November.

Cyril Ruoso / Wels catfish (Silurus glanis) Loire river, France. November.

Cyril Ruoso / Wels catfish (Silurus glanis) in the Tarn river, France, August.

Cyril Ruoso / Wels catfish (Silurus glanis) in the Tarn river, France, August.

Cyril Ruoso / Wels catfish (Silurus glanis) eating Mayflies (Ephoron virgo), dead at the surface of water because of public lighting. Tarn River, France, August.

Cyril Ruoso / Wels catfish (Silurus glanis) eating Mayflies (Ephoron virgo), dead at the surface of water because of public lighting. Tarn River, France, August.

Cyril Ruoso / Wels catfish (Silurus glanis) group gathered in river bed. Loire river, France. November.

Cyril Ruoso / Wels catfish (Silurus glanis) group gathered in river bed. Loire river, France. November.

Shane Gross / School of Striped eel catfish (Plotosus lineatus) move through seagrass, eating the algae growning on the seagrass blades. Manado, Indonesia.

Pascal Kobeh / Close-up of the head of a Striped eel catfish (Plotosus lineatus) Sulu Sea, Philippines.

Luke Massey / Giant otter (Pteronura brasiliensis) feeding on a Pleco catfish (Loricariidae) Rio Cuiaba, Pantanal, Brazil

Luke Massey / Giant otter (Pteronura brasiliensis) feeding on a Pleco catfish (Loricariidae) Rio Cuiaba, Pantanal, Brazil

Luke Massey / Giant otter (Pteronura brasiliensis) feeding on a Pleco catfish (Loricariidae) Rio Cuiaba, Pantanal, Brazil

Luke Massey / Giant otter (Pteronura brasiliensis) feeding on a catfish (Loricariidae) with Cocoi heron (Ardea cocoi) scavenging remnants, Rio Cuiaba, Pantanal, Brazil.

Luke Massey / Giant otter (Pteronura brasiliensis) feeding on a catfish (Loricariidae) with Cocoi heron (Ardea cocoi) scavenging remnants, Rio Cuiaba, Pantanal, Brazil.

Luke Massey / Giant otter (Pteronura brasiliensis) feeding on a Pleco catfish (Loricariidae) Rio Cuiaba, Pantanal, Brazil

Remi Masson / Wels catfish (Silurus glanis) swimming at bottom of Lake Neuchatel. Switzerland. September.

Remi Masson / Wels catfish (Silurus glanis) swimming at bottom of Lake Neuchatel. Switzerland. September.

Alex Mustard / School of young Striped catfish (Plotosus lineatus). Bitung, North Sulawesi, Indonesia. Lembeh Strait, Molucca Sea.

Luke Massey / Giant otter (Pteronura brasiliensis) feeding on a Pleco catfish (Loricariidae) Rio Cuiaba, Brazil