A major fish stranding caused by a natural hypoxic event in a shallow bay of the eastern South Pacific Ocean

Abstract

A massive beaching and mortality of fishes occurred in Coliumo Bay, a shallow bay located along the coast of the eastern South Pacific Ocean on 3 January 2008. This stranding was a consequence of an abrupt decrease in the dissolved oxygen concentration throughout the whole water column, due to the effect of intense upwelling along the coast off central-southern Chile. The main objectives of this study were: (1) to characterize taxonomically and biologically the fish species assemblage present in this beaching; (2) to evaluate several physiological indicators for the condition of the beached species at the time of their death; and (3) to assess the possible cause-effect mechanisms involved in the fishes death and the changes that took place in the fish community throughout the time. In this beaching, 26 fish species were identified: 23 teleosts, one myxiniform and two elasmobranchs. Most beached specimens were juveniles. Haematological and histological evidence indicate that severe hypoxia that lasted for at least 48 h was the most plausible cause of death. The main conclusion of this study is that the presence of oxygen-poor equatorial sub-surface water in the shallow coastal zone due to intense regional-scale upwelling caused the fish stranding. Although the effect of the hypoxic event was severe for the fish assemblage of Coliumo Bay, the rapid recuperation observed suggests that hypoxic events at the local spatial scale can be buffered by migration processes from the fish community inhabiting close by areas non-affected by low oxygen conditions. The effect that severe hypoxic events may have on larger spatial scales remains unknown.

Response of the epibenthic macrofaunal community to a strong upwelling-driven hypoxic event in a shallow bay of the southern Humboldt Current System

“…On the third day of this upwelling-hypoxic event, DO below 0.5 ml O 2 l À1 were detected and a massive die-off/stranding of marine organisms was reported, affecting zooplankton, mollusks, crustaceans and fishes. Fish species were strongly impacted by this hypoxic event, but previous fish species richness and half of the previous abundance were recovered during the three months following the event (Hernández-Miranda et al, 2010). This is in agreement with the Pearson and Rosenberg general model for community response to hypoxia for organic enrichment.…”

“…We provide a more detailed description of the oceanographical dynamics of the hypoxic event in January 2008, complementing and expanding a previous description (Hernández-Miranda et al, 2010). We then assess two main hypotheses regarding the response to hypoxia of epibenthic macrofauna in Coliumo Bay.…”

“…No studies have been conducted to assess the dynamic response of the whole epibenthic macrofaunal communities and ecosystems to these disturbances. During early January 2008, most of the south-central coastal zone of the HCS was affected by an intense upwelling (Hernández-Miranda et al, 2010). Severe hypoxic conditions were detected in Coliumo Bay, a small, shallow sandy bay in central Chile.…”

State of the Art and Challenges for Offshore Integrated Multi-Trophic Aquaculture (IMTA)

“…However, it is important to also understand how such environments may affect fed species, as these may not be optimal for fish growth. In some upwelling areas, like the Benguela current or the Humboldt current, hypoxia events occur frequently and this can be detrimental for cultivated species (Ekau et al, 2010;Hernández-Miranda et al, 2010.…”

Interannual variations in the hatching pattern, larval growth and otolith size of a sand-dwelling fish from central Chile

“…An intense event of natural hypoxia in January 2008 affected the entire resident community of shallow Coliumo Bay, causing widespread mortality of organisms and a mass stranding event, with fish being one of the most affected groups (Hernández-Miranda et al 2010, 2012b. These authors reported a recovery in richness of the fish assemblage in a timescale of only 3 months; nevertheless, densities reached only about half their previous level after 2 years of the event.…”