WHY ARE THE FISH DYING? By Raaisa Lemos Vaz

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There is been large scale mortality of fish across the rivers and lakes of Goa due to a very high degree of pollution from arbitrary sewage discharge…

GOA is world-renowned for its sun-kissed beaches, vibrant coastal culture, and rich culinary heritage, where fish curry-rice is a staple of daily life. However, beneath the sparkling surface of its celebrated rivers, lakes, and estuaries, a quiet ecological crisis has been unfolding. Over recent years, locals and environmentalists have been alarmed by a recurring, tragic sight: thousands of dead fish floating belly-up along river stretches like the Mandovi, Zuari, and Sal, as well as historic inland lakes like Carambolim and various village ponds.
These mass mortality events are not isolated accidents. Instead, they serve as a flashing warning sign from an aquatic ecosystem pushed to its absolute limit by rapid urbanization, tourism pressures, and changing weather patterns. To protect Goa’s biodiversity and food security, we must understand exactly why these fish are dying and what can be done to reverse the trend.

SYSTEMATIC FAILURE
THE recurring nature of these events points to a systematic failure in managing local water bodies. Several key areas have witnessed severe die-offs:
Mala Lake: A highly vulnerable zone that has experienced multiple mass fish deaths, including incidents where prized local varieties like Giant Sea Perch (chonak) and Pearl Spot (kalundar) died overnight.
Campal Lakeview Colony Lake: Directly connected to the heavily stressed St Inez Creek, this water body has seen repeated flare-ups of floating dead fish, sparking immense local alarm.
Carambolim Lake: An Important Bird and Biodiversity Area (IBA) where severe fish mortality has historically clashed with its status as a world-famous winter refuge for migratory birds.
Agacaim: Agricultural and tidal runoff channels where toxic waste dumping has historically decimated local populations of crabs, snails, and commercial fish.

CORE CULPRIT: INVISIBLE SEARCH FOR OXYGEN
WHEN thousands of fish die simultaneously without external signs of physical trauma or injury, the primary culprit is almost always hypoxia – sudden, catastrophic drop in dissolved oxygen levels.
Just like humans need clean air to breathe, aquatic life relies on microscopic oxygen molecules dissolved directly into the water. In a healthy tropical aquatic ecosystem, dissolved oxygen levels should consistently hover between 4 to 5 milligrams per liter. When environmental pollution disrupts the balance, these levels can plummet to near zero in a matter of hours, effectively suffocating everything beneath the surface.

Why Is This Happening Across Goa?
THE Goa State Pollution Control Board (GSPCB) along with institutes like the ICAR-Central Coastal Agricultural Research Institute (CCARI) have identified a web of interconnected human and natural activities driving these events.

Untreated Sewage and Domestic Wastewater
With Goa’s booming tourist economy and expanding urban centers, wastewater infrastructure has struggled to keep pace. In many coastal belts and dense settlements, untreated or partially treated sewage leaks from overloaded septic tanks or is discharged directly into municipal storm drains. St. Inez Creek in Panaji and stretches of the Sal River in South Goa have historically faced immense stress from domestic waste. Sewage is incredibly rich in organic carbon and nutrients, providing the perfect fuel for the suffocating algal blooms.
Agricultural Run-off During Monsoons
Goa’s heavy monsoon season plays a dual role. While rainwater flushes out stagnant systems, the initial heavy downpours wash accumulated synthetic fertilizers from inland paddy fields and plantations straight into adjacent streams and lakes. This seasonal influx of agricultural chemicals causes sharp, unpredictable spikes in nutrient loading, triggering sudden fish die-offs in early monsoon cycles.
Industrial Effluents and Changing Chemistry
Beyond organic waste, some inland river stretches near industrial estates experience chemical pollution. Inadequately treated industrial effluents can sharply alter the watershed pH or salinity, shocking the biological systems of local fish species. Furthermore, historically unmanaged runoff from iron ore mining zones has deposited heavy metal traces and fine silt into river beds, destroying bottom-dwelling organisms and damaging delicate fish gills.
Stagnant Waters and Climate-Driven Heat Spikes
Climate change has noticeably altered local weather patterns, causing frequent spikes in summer temperatures. From a purely physical standpoint, warm water holds less dissolved oxygen than cold water. When an intense heatwave hits Goa, shallow lakes or river bends that suffer from poor water circulation become environmental traps. If human-made bunds, illegal land reclamation, or plastic debris block the natural, oxygenating flow of the daily tides, the water stagnates, heats up, and turns into a localized death zone.

DYING LANDSCAPES OF OLD
THE impact of repeated fish mortality stretch far beyond an unpleasant smell or a temporary blemish on a tourist landscape. The consequences rip through Goa’s ecological and socioeconomic fabric:
Livelihood Strains: Small-scale, traditional fishermen who rely entirely on inland rivers and estuaries face immediate financial losses when local fish stocks collapse.
Biodiversity Loss: Constant environmental shock wipes out sensitive native species, leaving the water dominated by hyper-resilient or invasive species, permanently altering the ecosystem.
Public Health Risks: While mass die-offs usually prompt immediate cleanups, chronic low-grade pollution leads to bioaccumulation– where toxic metals or chemicals build up inside the tissue of surviving fish, eventually making their way onto local dinner plates.
Fixing Goa’s water bodies requires moving away from reactive cleanups and moving toward proactive, scientific management. The recurring fish mortality cases across Goa are a clear reminder that economic progress and environmental preservation cannot be separated. The rivers and lakes that shaped Goa’s history and support its legendary cuisine require active protection. By treating waste responsibly, restoring natural water flows, and utilizing modern monitoring tools, Goa can clean up its precious water bodies – ensuring they remain vibrant, healthy ecosystems for generations to come.