Fish conservation in freshwater and marine realms: status, threats and management

Abstract

1. Despite the disparities in size and volume of marine and freshwater realms, a strikingly similar number of species is found in eachwith 15 150 Actinopterygian fishes in fresh water and 14 740 in the marine realm. Their ecological and societal values are widely recognized yet many marine and freshwater fishes increasingly risk local, regional or global extinction.2. The prevailing threats in aquatic systems are habitat loss and degradation, invasive species, pollution, over-exploitation and climate change. Unpredictable synergies with climate change greatly complicate the impacts of other stressors that threaten many marine and freshwater fishes.3. Isolated and fragmented habitats typically present the most challenging environments for small, specialized freshwater and marine fishes, whereas overfishing is by far the greatest threat to larger marine and freshwater species. Species that migrate within or between freshwater and marine realms may face high catchability in predictable migration bottlenecks, and degradation of breeding habitat, feeding habitat or the intervening migration corridors.4. Conservation reserves are vital to protect species-rich habitats, important radiations, and threatened endemic species. Integration of processes that connect terrestrial, freshwater and marine protected areas promises more effective conservation outcomes than disconnected reserves. Diadromous species in particular require more attention in aquatic restoration and conservation planning across disparate government agencies. 5. Human activities and stressors that increasingly threaten freshwater and marine fishes must be curbed to avoid a wave of extinctions. Freshwater recovery programmes range from plans for individual species to recovery of entire basin faunas. Reducing risks to threatened marine species in coastal habitats also requires conservation actions at multiple scales. Most of the world's larger economically important fisheries are relatively well-monitored and well-managed but there are urgent needs to curb fishing mortality and minimize catch of the most endangered species in both realms.

Genetic diversity and population history ofTanichthys albonubes(Teleostei: Cyprinidae): Implications for conservation

“…Tanichthys albonubes has not been considered an endangered species by IUCN because aquarium specimens are easily kept and bred in a wide variety of water conditions. However, this freshwater fish cannot maintain self‐supporting populations in the wild as a result of many threats, including habitat loss, invasive species, water pollution, overfishing and climate change (Arthington, Dulvy, Gladstone, & Winfield, ). For example, Lee () proposed a mass release of captive‐bred stocks into various wetlands, but the present study found that these reintroduced populations could not exist in a stable state in nature.…”

Relationships between forest cover and fish diversity in the Amazon River floodplain

“…Tropical freshwater ecosystems support high biodiversity and important ecosystem services (Davidson, ; Tockner & Stanford, ). Tropical fishes in particular are highly vulnerable to habitat degradation, with this group comprising over 31% of freshwater species listed as at risk of extinction by the IUCN (Arthington, Dulvy, Gladstone, & Winfield, ; Darwall & Freyhof, ). A few studies have documented effects of land cover change on the taxonomic structure of fish communities in tropical streams (e.g.…”

Potential Impacts of PIT Tagging on a Critically Endangered Small‐Bodied Fish: A Trial on the Surrogate Mountain Galaxias

“…; Arthington et al. ). Based on knowledge of the Mountain Galaxias’ response to PIT tagging, this species may be used as a surrogate for other morphologically similar species, especially those in the Mountain Galaxias species complex.…”