Effects of fish kills on fish consumers and other water-dependent fauna: exploring the potential effect of mass mortality of carp in Australia

Abstract

Although the effects of mass fish mortality (MFM) events on fish populations and water quality are frequently reported, the effects on consumers of fish and other water-dependent fauna are relatively poorly understood. Managing the effects of MFM events on other fauna is important when they occur in ecologically or culturally sensitive locations, or involve protected or significant species or ecosystems. Better understanding of the effects of such events on fish consumers and other water-dependent fauna would aid proactive management of predictable events, such as pest-fish biocontrol releases. We conducted a global literature review to synthesise the effects of unexpected MFM events on fish consumers and other water-dependent fauna in freshwater, estuarine and marine ecosystems. We then constructed two conceptual models distinguishing between the short-term (hours to weeks) and long-term (months to years) effects of such events, highlighting the importance of key factors in determining the magnitude of the response. Last, we used these models and relevant literature to explore the potential implications of the proposed release of cyprinid herpes virus 3 as a biological control agent for the invasive common carp (Cyprinus carpio) in Australia and develop recommendations to minimise adverse effects of carp mass mortality on food webs.

Scavenging by threatened turtles regulates freshwater ecosystem health during fish kills

“…the Lachlan river, ~ 3,144 kg carp/ha 31 ). A sudden increase in carp carcasses where turtles are now scarce will severely affect the ecosystem due to the absence of scavengers removing them quickly 7 .…”

“…Fish kills degrade water quality by increasing the concentrations of ammonia and nitrates, and driving phytoplankton and cyanobacteria blooms, which decrease dissolved oxygen concentrations 4 , 5 . Together, these effects can lead to devastating biodiversity losses and ecosystem breakdown 6 , 7 . Fish kills also have human impacts; bacterial and cyanobacterial blooms can cause serious illnesses, such as botulism 8 .…”

Key steps to improve the assessment, evaluation and management of fish kills: lessons from the Murray–Darling River system, Australia

“…Fish kills can affect water quality, food availability, food webs and trophic structure (crustacean, molluscs and macroinvertebrates), competition and population processes (e.g. reduced predation pressure) and food sources for non-fish organisms (birds, terrestrial fauna; McGinness et al 2020).…”

“…Impacts of dead fish on water quality, general ecology and the ecology and health of other species that rely on fish also need to be considered (McGinness et al 2020). These issues should all be addressed through the development and implementation of post-kill plans that aim to recover the populations and values lost.…”

Women in freshwater science: challenges and solutions for achieving equity

“…Research papers also explore the timing of, and appropriate methods of sampling to detect, spawning of freshwater fish in the wet-dry tropics (King et al 2020) and whether changes in prey composition have the capacity to affect efficiency of protein synthesis and nitrogen wastage in freshwater fish (Dwyer et al 2020). Two papers develop new conceptual frameworks: one a model of the effect of mass fish-kills on consumers of fish in aquatic streams (McGinness et al 2020) and the other developing a method to place individual management actions (here, environmental watering actions) in a broader spatial and temporal context to identify possible barriers to achieving long-term objectives (Lester et al 2020). Finally, four other pieces explore broader aspects of women in freshwater science: the challenges associated with being a woman in tropical peatland research (Thornton et al 2020), highlight past contributions to freshwater science by women that have been largely overlooked (Downes and Lancaster 2020;Waterton et al 2020), explore the gender bias in measures of research quality and output (Downes and Lancaster 2020), and raise awareness of the risk of avian botulism and identify appropriate management strategies (Brandis et al 2020).…”