Extinction vulnerability in marine populations

Abstract

Human impacts on the world's oceans have been substantial, leading to concerns about the extinction of marine taxa. We have compiled 133 local, regional and global extinctions of marine populations. There is typically a 53‐year lag between the last sighting of an organism and the reported date of the extinction at whatever scale this has occurred. Most disappearances (80%) were detected using indirect historical comparative methods, which suggests that marine extinctions may have been underestimated because of low‐detection power. Exploitation caused most marine losses at various scales (55%), followed closely by habitat loss (37%), while the remainder were linked to invasive species, climate change, pollution and disease. Several perceptions concerning the vulnerability of marine organisms appear to be too general and insufficiently conservative. Marine species cannot be considered less vulnerable on the basis of biological attributes such as high fecundity or large‐scale dispersal characteristics. For commercially exploited species, it is often argued that economic extinction of exploited populations will occur before biological extinction, but this is not the case for non‐target species caught in multispecies fisheries or species with high commercial value, especially if this value increases as species become rare. The perceived high potential for recovery, high variability and low extinction vulnerability of fish populations have been invoked to avoid listing commercial species of fishes under international threat criteria. However, we need to learn more about recovery, which may be hampered by negative population growth at small population sizes (Allee effect or depensation) or ecosystem shifts, as well as about spatial dynamics and connectivity of subpopulations before we can truly understand the nature of responses to severe depletions. The evidence suggests that fish populations do not fluctuate more than those of mammals, birds and butterflies, and that fishes may exhibit vulnerability similar to mammals, birds and butterflies. There is an urgent need for improved methods of detecting marine extinctions at various spatial scales, and for predicting the vulnerability of species.

Measuring marine fish biodiversity: temporal changes in abundance, life history and demography

“…Based on their empirical study of 58 marine fish population extirpations, Dulvy et al (2003) concluded that exploitation was the sole or primary cause of decline for 40 of the cases examined; the remainder were attributed to habitat loss, although the effects of habitat loss and exploitation on abundance are not always readily separable. Irrespective of the causes, failure to arrest population declines can result, and has resulted, in the extirpation of some marine fish from parts of their former geographical ranges (Dulvy et al 2003(Dulvy et al , 2004Myers & Ottensmeyer 2005).…”

Recovery of marine animal populations and ecosystems

“…Today, many marine mammal, bird, reptile and fish populations are at low abundance, and several species are endangered or extinct on regional or global scales [5,[10][11][12]. However, despite long periods of intense human impacts, most marine species persist and some populations do show signs of recovery [3,8,9].…”

Climate Change: Warming Impacts on Marine Biodiversity

“…The greatest risk of extinction is experienced by species with longer generation cycles, small population size as well as ecological specialists and overexploited species (Dulvy et al 2003). Especially more complex species (but also larger species) have to "buy time" to persist in a climate change scenario (Chevin et al 2010;Storch et al 2014), as their genetic modifications usually require more extended time scales for DNA-fixed adaptive changes.…”