FISH DEATHS: KEY REASONS, OCCURRENCE PATTERN AND FUTURE PERSPECTIVES

Fish kill, also known as Massive Fish Deaths (MFD) are kind of death on a massive scale and an example of Mass Mortality Events (MMEs). MMEs are among the most extreme events of nature as they are single catastrophic incident that wipes out vast numbers of a species in a short period of time. The MFDs are thought to be random events due to the lack of systematic documentation and studies, but this study ponder out the reasons and the patterns of their occurrences.

Diseases, direct effects tied to humans; such as environmental contamination, bio-toxicity and processes directly influenced by climate; including extreme weather, thermal stress, and hypoxia are the key reasons for MFDs.

Over time the magnitude of MMEs has been intensifying for birds, fishes and marine invertebrates; invariant for mammals; and decreasing for reptiles and amphibians. It is found that the number of MFDs has been increasing by about one event per year.  This is a substantial increase especially given the increased magnitudes of MMEs, even while the die-offs are rare and fall short of extinction.

MFDs provide an understanding about the effects of changes in aquatic ecosystems. An MME can push a species closer to extinction and also can have knock-on effects elsewhere in the fragile food web. Understanding both the cause and consequence of animal die-offs is critically important, because disease may be involved which could spread to humans. Toxic chemicals may be a cause which can affect other animals and humans. Changes in climate or weather may be involved and recognizing patterns could help prepare for future events and understand natural systems better.

The reports of MMEs are probably underestimates in terms of occurrence and sheer magnitude as there had been no quantitative analysis of the patterns of MMEs. There are no much scientific reports of these events especially for fishes in India and most of these event reports are published as only newspaper report rather than scientific studies. WHISPers like databases are very much essential and documentation of such events can be improved in the future by including the possible use of citizen science to record mass mortality events in real time. In addition to monitoring physical changes such as changes in temperature and precipitation patterns, it is important to document the biological response to regional and global environmental change. There needs to be better monitoring of these events, since that's the only way we'll know how much trouble life on Earth is in. It can be said with confidence that, the sorts of extreme weather events linked to MMEs will become more frequent potentially killing more than ninety percent of a population in one shot.