title: Hypoxia increases the risk of egg predation in a nest-guarding fish.
abstract: For fish with parental care, a nest should meet both the oxygenation needs of the eggs and help protect them against predators. While a small nest opening facilitates the latter, it impedes the former and vice versa. We investigated how the presence of potential egg predators in the form of shore crabsCarcinus maenasaffects nest building, egg fanning, defensive displays and filial cannibalism of egg-guarding male sand gobiesPomatoschistus minutusunder two levels of dissolved oxygen. In the high oxygen treatment, males retained their nest opening size in the presence of crabs, while males in low oxygen built large nest openings both in the absence and presence of crabs, despite the fact that crabs were more likely to successfully intrude into nests with large entrances. Males in low oxygen also fanned more. In the presence of crabs males increased their defensive displays, but while males in high oxygen reduced fanning, males in low oxygen did not. Filial cannibalism was unaffected by treatment. Sand gobies thus prioritize egg ventilation over the protection afforded by small nest openings under hypoxia and adopt defensive behaviour to avert predator attention, even though this does not fully offset the threat from the egg predators.
authors.affiliation: National Institute of Aquatic Resources, Technical University of Denmark, Lyngby, Denmark; Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Karin H
authors.identifier: 0000-0002-1695-0989
authors.initials: KH
authors.lastname: Olsson
authors.affiliation: Department of Biological and Environmental Sciences , University of Gothenburg , Gothenburg , Sweden.
authors.forename: Charlotta
authors.initials: C
authors.lastname: Kvarnemo
authors.affiliation: Department of Biological and Environmental Sciences , University of Gothenburg , Gothenburg , Sweden.
authors.forename: Maria Norevik
authors.initials: MN
authors.lastname: Andrén
authors.affiliation: Department of Biological and Environmental Sciences , University of Gothenburg , Gothenburg , Sweden.
authors.forename: Therése
authors.initials: T
authors.lastname: Larsson
keywords: clutch cannibalism; egg predation; low oxygen; nest defence; parental care