MAPUSA
Goa’s unusually dry and oppressive September may not be making much noise at the fishing jetty yet, but beneath the surface, the sea could already be responding to a monsoon that has behaved very differently this year.
The State has gone through a prolonged rainfall deficit, with September bringing barely a fraction of the rain normally expected at this time of the year. By mid-September, Goa had recorded a seasonal rainfall deficit of around 34 per cent, placing it among the more rain-deficient States in the country.
For fisheries, however, the concern is not simply the amount of rain that falls on land. It is what the altered weather does to the marine ecosystem.
Director of Fisheries Shamila Monteiro puts the issue cautiously: “Climate effect in the long run can have an effect on fish production.”
She has, however, stopped short of linking this year's unusual weather to any immediate decline in catches or identifying particular fish species that could be affected.
That caution is important. There is currently no basis to say that Goa is heading for a fish-production crisis because of this year's deficient monsoon. But there is growing scientific evidence that changes in temperature, rainfall, winds and ocean conditions can alter the marine food chain on which fish depend.
First link in chain
may be plankton
Rainfall and monsoon winds influence the movement and mixing of nutrients in coastal waters. Those nutrients help sustain phytoplankton, which form the base of much of the marine food web. Changes at this level can eventually ripple upwards to zooplankton and fish.
A recent study published in Scientific Reports, examining fish landings along India's west coast and including observations off Goa, found that fish landings were associated with chlorophyll-a concentrations – a proxy for phytoplankton – and dissolved oxygen, while warmer sea-surface temperatures were associated with lower landings. The study found that landings declined when sea-surface temperatures crossed about 28.9°C.
That does not mean every hot September will produce fewer fish. It does suggest, however, that the weather above the sea and the conditions inside it are closely connected.
Earlier research specifically on Goa's coastal fisheries has also established that the monsoon influences the movement and spawning of fish and directly affects fish diversity and abundance.
Fish may not disappear
-- they may move
For fishermen, perhaps the more immediate consequence of changing marine conditions could be a change in where the fish are found and which species dominate the catch.
A warmer sea does not necessarily mean fish die. Some species can move to deeper or cooler waters, while others may shift their geographical distribution. Former IMD and NIO scientist Dr Ramesh Kumar pointed out that weather-related changes can cause fish to migrate towards cooler waters or move deeper into the sea.
This is particularly relevant for commercially important species. A Union fisheries department assessment on climate change and Indian marine fisheries has documented changes in the distribution of species such as oil sardines and Indian mackerel in response to changing sea-surface temperatures. It also notes temperature-related effects on spawning and growth in several species.
For Goa's fishermen, such changes can translate into a very practical problem: The fish may still be there, but not necessarily where fishermen expect them to be.
That can mean longer fishing trips, higher fuel consumption and greater uncertainty over catches.
Unpredictability may
be the real warning
The bigger question, therefore, may not be whether Goa will have less fish this year.
The more significant concern is whether increasingly erratic weather will make fishing itself less predictable.
The monsoon is not merely a period when fishing is restricted. It is part of the ecological rhythm of the Arabian Sea. If rainfall patterns, wind regimes and sea temperatures increasingly depart from that rhythm, the timing of plankton production, fish spawning and seasonal migration could also shift.
For a State whose fishing economy is built around generations of knowledge about seasons and fish movement, that could prove more disruptive than one bad monsoon.
