Is Fishing Good After Rain? It Depends Where You Fish

Fishing after rain is good in some places and poor in others. An estuary gains food from light rain. Heavy rain moves bream towards the mouth. An enclosed bay depends on where the runoff goes. On the open coast, rain matters least.

Most pages answer this question with one word. That word is wrong somewhere in Australia every time it rains. Rain is not a condition you can read on its own. It is a delivery system for three things that do matter: dirt, fresh water and food. Which of the three reaches your spot, and how fast it clears, is the whole answer.

This guide covers saltwater only. It splits the answer by place, because an estuary and an open beach are not the same water body, and by species, because a squid and a flathead behave in opposite ways when the water goes brown. It is the fourth guide in this series, after wind, barometric pressure and water temperature.

What rain actually delivers

Runoff. Rain that lands on a catchment takes hours to a day or more to reach the water. Small drains respond within an hour. A big river system lags by a day, and lags again if the ground was already wet. A heavy burst on dry ground does less than a lighter fall on soaked ground. This is why the water can be clean at 8 am and brown at 3 pm with no rain falling at all.

Clarity. Suspended sediment is what colours the water. It scatters and absorbs the light a fish needs to see your lure. The effect is local and intense near the inflow, and it thins with distance and tide. A published study on a New South Wales estuary found turbidity rose hardest in the upper half on the heaviest rain day, spread to the lower reaches the next day, had fallen significantly by day 5, and had returned to pre-rain levels by day 8 (Payne and others, 2013).

Salinity. Fresh water is lighter, so it floats. A hard fall can put a low-salinity layer over salt water, and the two can stay layered for days. That matters because the fish you want may be sitting under the fresh layer, not in it. It also means the reading at the surface and the reading at the bottom are different numbers.

Bait. Runoff carries worms, insects, prawns and dislodged organic matter out of the catchment and into the salt. This is the one genuinely positive part of the equation, and it is why a drain or a creek mouth is worth a look when little else is.

Estuary: the place where rain matters most

An estuary is a catchment with a tide in it. That makes it the most rain-sensitive water you can fish, and the most rewarding when you get the timing right.

Light rain versus heavy rain. Field reports from Australian anglers treat light rain as a positive. Food washes in from the banks and the stormwater drains, and the fish work those delivery points. Heavy rain is a different event. It drops salinity in the upper estuary, discolours the whole system, and moves the fish, rather than switching them on.

Bream move downstream. One acoustic telemetry study of 34 black bream in a small Tasmanian estuary found fish moving down the estuary during heavy inflows, and returning upstream as salinity rose. Our notes put the trigger near 10 parts per thousand. That is a movement finding on one system, so treat it as a direction rather than a law. The practical read is simpler: after heavy rain, the fish are closer to the mouth than they were last week. Fish where they are.

Bream also change shift. The best study here is unusual and worth knowing. Six yellowfin bream in a New South Wales estuary carried activity tags for four months. Normally they were most active and shallowest during the day. After rain they flipped and became nocturnal, with the switch lasting until conductivity and turbidity came back to normal. So in the days after a big event, daytime bream fishing is the weaker half of the clock and the night is the better half. That is one study, on one species, on six fish. It is still the best measurement anyone has.

Flathead stay. Flathead are estuarine residents with high fidelity to their system, and they stay put through a rain event. Tackle shop advice has them tight to the bottom and close to the edges when the water is up. They remain catchable in stained water. The "rain turns on a flathead feeding frenzy" claim is repeated everywhere and has no measurement behind it. The finding it usually rests on links more freshwater to a higher chance of fish moving, and to bigger commercial gill-net catches, across five New South Wales estuaries. Movement is not feeding, and gill-net catch is not lure catch.

Mulloway sit at the mouth. The colour line where dirty fresh meets clean salt is the classic spot, and Australian tackle shops and anglers name it again and again. No study has measured it. A distinct line gives an ambush predator an edge to hunt along. If you can see the line, fish it. If the whole system is one colour, there is no line to fish and the mouth is your fallback.

Where to go. Werribee River Mouth is the shallow end of an estuary meeting a bay, and it fishes best after three or more dry days when the colour settles. Maribyrnong River at Footscray is a bream and mulloway system where the fresh push matters more than the tide. In New South Wales, Lake Illawarra at Windang Bridge and Minnamurra River Mouth both put you on the entrance water rather than the dirty interior. Mogareeka, at the Bega River mouth is the same play on the far South Coast. Tom Uglys Bridge and Captain Cook Bridge on the Georges River are the water the bream study actually came from.

Enclosed bay: the runoff plume decides

A bay has catchments all round its edge. So the question stops being "did it rain" and becomes "which river drains into the shore I am fishing". That is the single most useful thing you can learn about your local bay.

Port Phillip Bay is the clearest example. The Yarra enters in the north-east and spreads turbid water mainly to that sector. The Werribee enters in the west. The Patterson enters in the south-east near Carrum and Seaford. Inshore water near those mouths can colour within a day or two of rain. Our working range for it to clear is 2 to 5 days, depending on tidal flushing and wind. That range is an estimate. The Victorian EPA advice is different: avoid swimming for up to 48 hours after heavy rain, and that advice is about bacteria, not colour. Away from the plumes the bay can be clean at the same moment.

Squid struggle first. Southern calamari hunt mainly by sight. Our species record puts their tolerance at about 27 to 37 parts per thousand, and notes that a river-mouth spot freshens within about a day of heavy rain and the squid leave for saltier water. That is why the squid guides say to cancel after heavy rain. A jig they cannot see, in water they do not want to be in, catches nothing.

Snapper tolerate more colour. Moderate colour on a shallow edge often fishes well, and anglers have believed this for a long time. Be careful with the reason. The claim that snapper use smell and their lateral line more than sight, so dirty water helps them, has no citation in our research. The pattern may be real. The explanation is a guess.

Where to go. Fish the clean side of the bay, not the side the plume is on. Mordialloc Pier sits on a creek mouth, so it colours fast, and it can fish well once it clears. Williamstown, Gem Pier and Altona Pier are shallow enough to colour quickly and to clear quickly too. Stony Point and Hastings Jetty sit in Western Port, which flushes differently again. Flinders Pier sits where that bay meets Bass Strait, and its guide explains how clarity shapes a session there.

Open coast: rain matters least

A surf beach usually has little catchment directly behind it. Rain falling on sand drains through sand, and swell keeps mixing the surface. That makes the open coast the water we expect a downpour to change least. This is reasoning, not a measurement, and it has a limit: a big flood can push a river plume along the coast.

What does change is local. A flooded drain, a creek crossing the beach, or stormwater from a car park colours one stretch of water and leaves the rest alone. After a big event that local patch can hold bait and hold fish, and it is small enough to find on foot. The rest of the beach fishes the way it always does.

Species. Salmon and tailor already live in high-energy water, and anglers keep fishing for them in a bit of colour. When a bay has coloured up, squid on open-coast rocks are worth a try, because the ocean behind them stays salty. Those are field habits, not measured results.

Where to go. Gunnamatta Beach, 13th Beach and Bancoora Beach are Victorian surf beaches where the rain changes little and the swell changes everything. Bellambi Point and Point Ho on the Illawarra coast give you rock platforms with real ocean behind them. Port Welshpool Long Jetty is the deep-water alternative when the ocean is up.

Squid and flathead answer in opposite ways

This is the part that makes a single answer useless. Put the same brown water in front of these two fish and they do opposite things.

Squid leave. They hunt mainly by sight, so dirty water takes away the sense they rely on most. They do feel water movement through sensory lines on the head and arms, but nobody has shown that this lets them find a jig in brown water. Our record gives them a narrow salinity range. Fresh water pushes them towards salt, and dirty water stops them seeing the jig. Both run the same direction. The field claim that they leave is graded low in our record. After heavy rain near a river mouth, fish somewhere else until the water clears.

Flathead stay and hunt. They live in the estuary and they hold position. Stained water is normal habitat for them, not a shutdown. Their clarity preference in our own research is unresolved, with one model saying slight turbidity is best and another saying clear water earns a bonus. Both agree on the shape: it is a band, not "clearer is always better".

What that means for your session. Brown water and a squid plan is a wasted drive. Brown water and a flathead plan is a session: fish slower, keep the lure on the bottom, and work the edges. Same water, opposite plan.

How long does the effect last?

Match the answer to the size of the system in front of you. This is the honest version, and none of it is measured to the day.

• A drain or a small creek, a day or less. Small catchment, small volume of dirt, and the tide washes it out fast.
• A bay shoreline near a river mouth, about 2 to 5 days. This is our working estimate, not a measured figure, and it moves with tidal flushing and wind.
• A big estuary, about a week. The Payne study measured turbidity falling significantly by day 5 and back to normal by day 8, with the upper estuary holding colour longer than the lower.
• Fresh water sitting on top, days. Layering can persist after the colour has gone, because the fresh layer needs wind or a tide to mix it away.

You will read that the best sessions come 2 to 3 days after moderate rain. Treat that as a local rule of thumb rather than a measurement. It sits inside our working range for a bay shoreline, which may be why it feels right to the people who repeat it. No study has measured the day after rain when fish actually feed hardest, on any of these species, in these waters.

What the evidence actually says

Strong. Turbidity lowers prey capture for aquatic predators. That is a systematic review and meta-analysis of 60 studies and 657 effect sizes, and it is the best-supported link in this whole page. Read it honestly, though. About half of those effect sizes were not statistically significant, and the size of the turbidity change mattered more than the type of predator. What it does not say is that a visual hunter is cushioned by having other senses.

From related squid. Squid eyes are built for low light, and their salinity tolerance is recorded as narrow. Most of that work comes from close relatives of southern calamari. A squid also has sensory lines on the head and arms that respond to water movement, recorded in a 1988 study of a cuttlefish and a squid, so sight is not its only sense.

Moderate. The bream rain switch, meaning the flip to night activity, is one acoustic study on six fish. It is real data, carefully collected, and narrower than it sounds.

Thin. The claim that rain switches on a flathead feed. The claim that snapper feed better in dirty water because they smell it. The salinity figure where bream move, which comes from our notes on one study of one system. The idea that an open beach changes after rain at all, beyond the local drain.

Absent. No study measures the rainfall intensity at which any of these effects start for these species. No study measures the day after rain when the bite peaks. No study measures bream, flathead or squid catch rate against rain in Victorian water. Where you see a precise number of millimetres or a precise number of hours quoted with confidence, it is angler practice wearing a lab coat.

How to read the conditions

• Worth a session when the rain has stopped, the water has colour but you can still see a lure at a metre, and you are on the side of the system the runoff is not coming from. A drain, a creek mouth or a visible colour line all raise the odds.
• Not at its best means fishable but compromised. Fresh water still coming down, colour past reading, or a bay still carrying the plume. Fish deeper, fish slower, fish the edge of the dirty water rather than the middle of it.
• Leave it when the water you came for is chocolate to the bottom, the fresh push is still running, or the whole system is one colour with no line to fish. Try the mouth, or a different water body.

The spot page shows the hourly rain rate and an estimate of visibility in metres. Read them together. The rate on its own tells you what is falling now, not what has already run off the catchment. The clarity figure tells you what the water in front of you is actually like, which is the number that decides whether a squid will see your jig.

Safety, plainly

Heavy rain brings floodwater, and floodwater carries debris, sewage and strong current. Check the official warnings for your area before you go, and stay out of flooded water. Do not walk a rock platform or a river entrance in a rising or dirty sea, and do not stand below a stormwater outlet that is running hard.

This page gives no safety clearance. The catchability and fishability bands on a spot describe the fit for the fish. Neither one tells you that a place is safe to stand.

Frequently asked questions