Adaptation to hypoxic environments; bearded gobies Sufflogobius bibarbatus in the Benguela upwelling ecosystem

Abstract

The oceans of the world are slowly losing oxygen, in part because of climate change and in part because of anthropogenic eutrophication. This deoxygenation affects marine organisms in species-specific ways. This paper reviews what is known on how hypoxia tolerant species respond to low dissolved oxygen, using the bearded goby Sufflogobius bibarbatus as a model system. This species is endemic to the Benguela upwelling ecosystem, where, off Namibia, 9000 km of the shelf is hypoxic. Here, the species is now considered central to ecosystem functioning and in recent decades it has sustained commercial fisheries. Unlike their predators, S. bibarbatus has strong anti-predator responses as they can remain alert and escape threats in anoxic and severely hypoxic waters and can cope with sulphide shocks. Populations display diel vertical migration and shuttle between suboxic seabed refugia during the day to more oxygenated waters higher up in the water column at night and whilst they may share the water column with predators they may reduce their predation risk by associating with jellyfish (Aequorea forskalea and Chrysaora fulgida). The spatial distribution of S. bibarbatus varies with changes in available oxygen and populations expand and contract with climate-induced changes in the distribution of hypoxic waters. This species has an unusual diet and plays an important role in ecosystem functioning. It is a batch-spawner, with a protracted spawning season. Remarkably, males display alternative reproductive tactics and reproduction can take place at oxygen levels <0·5 ml l dissolved oxygen on the shelf break. Gaps in knowledge are identified and future works are proposed.

Home sweet suboxic home: remarkable hypoxia tolerance in two demersal fish species in the Gulf of California

“…hypoxia-tolerant fish (Mandic et al 2009), but no physiological measurements are available. Both species would be excellent candidates for an in-depth study of hypoxia adaptations, as was recently done for the hypoxia-tolerant bearded goby on the Namibian margin (Salvanes and Gibbons 2018). While C. emmelas and C. cephalus individuals were mainly observed actively swimming in this study, more than 20 observations were made of C. emmelas individuals resting with their heads buried in the sediment (Fig.…”

Understanding fish populations

“…Fish in a Changing World is represented by specific and more generic studies. Specifically, the effects of increasing hypoxia on bearded goby Sufflogobius bibarbatus (von Bonde 1923) by Salvanes & Gibbons (2018) and of the endocrine profiles of group-living skunk anemonefish Amphiprion akallopisos Bleeker [P.] 1853 by Mills et al (2018) improve our understanding of how species reproduction will be affected by future environmental changes. On a more generic level, the future of fishes and fisheries in the changing oceans was highlighted by Cheung (2018) and addressed by Gordon et al (2018) in a wide-ranging discussion paper also including freshwater issues.…”

“…Fish in a Changing World is represented by specific and more generic studies. Specifically, the effects of increasing hypoxia on bearded goby Sufflogobius bibarbatus (von Bonde 1923) by Salvanes & Gibbons () and of the endocrine profiles of group‐living skunk anemonefish Amphiprion akallopisos Bleeker [P.] 1853 by Mills et al . () improve our understanding of how species reproduction will be affected by future environmental changes.…”

Genetic structure ofSufflogobius bibarbatusin the Benguela upwelling ecosystem using microsatellite markers

“…After the collapse of the sardine population Sardinops sagax , S. bibarbatus has partially replaced the sardine as the main prey item in the diet of predators, where it can represent over 50% of the prey consumed by seabirds, seals and hake Merluccius spp. (Crawford, Cruickshank, Shelton, & Kruger, ; Crawford et al, ; van der Lingen et al, ; Mecenero, Roux, Underhill, & Kirkman, ; Salvanes & Gibbons, ). As a result, it has become vital to understand their population genetic structure across the region.…”