How to

Weather to go fishing

Rockfishing can be dangerous in rough weather.

ONE thing none of us can control is the weather. This is probably why many anglers conveniently blame adverse weather as a catchall reason why they don’t catch fish. Too hot, too cold, too windy, not windy enough, too wet, too dry. And so on. Weather certainly plays an important role in all outdoor activities. Sports like sailing, surfing and windsurfing thrive on windy stuff, while others like cricket and drag racing have a distinct aversion to rain and other forms of precipitation. For fishing, the weather is particularly crucial as conditions such as wave heights, water temperature, salinity and clarity, and a myriad of other variables, are all intimately linked to weather conditions and seasonal influences. To top it all off, we also have the added variables of how weather and season influence the movements and activities of fish. Obviously if you have a basic understanding of weather phenomena, this can help you make sure the weather variable works for you more often than against you.

Successful fishermen tend to be avid students of the weather. They put in time to determine relationships between weather controlled variables and where and when their local fish are biting. From the angler’s point of view, wind and rainfall are high on the list of the most important weather variables as they directly affect access to some fishing spots and your comfort level once you get there. From a fish’s point of view, the list is different. Water conditions affect fish the most; this will include water temperature, salinity, clarity, and oxygen content. For baitfish, other important variables may include water nutrient content (which modulates plankton blooms and therefore food availability), while predatory fish are affected by these variables and also the distribution of baitfish. Then there are the overlying influences of tidal movements related to the position of the moon, seasonal aspects related to the Earth’s path around the sun, and longer term climate trends. Indeed, weather is a complex and dynamic phenomena, and only recently have we humans begun to get a handle on how the various parts fit together and influence each other.

Marlin prefer warm clear water.

Weather prediction is a critical aspect of fishing as it actually influences where and how you intend to fish. In the 50 or 60 years since the advent of satellites and computer technology, meteorologists have made huge advances in understanding and predicting weather. At a larger scale, improved understanding of climate phenomena such as the El-Nino -Southern Oscillation (ENSO) has allowed climatologists to accurately determine the probability of large scale weather events such as droughts, floods and cyclones months or even years in advance. However, while fisheries managers might be interested in how these large-scale phenomena influence fish recruitment and thus will affect fish populations in years to come, the average angler is not really worried about this stuff. We usually want to know what the weather will be like up to a week or so in advance to organise a fishing trip, devise a gameplan, and improve the chance of encountering our chosen target species. Fortunately meteorologists have become quite good at predicting weather up to a week in advance, so it comes down to working out where to get the weather info and how to apply the data to your fishing scenario to make it work for you.

Snapper respond to changing weather conditions.

Finding weather reports
In today’s world if you read anything in a newspaper you’re a day behind when it comes to having your finger on the pulse. The internet is your first and probably best source of weather information – it can even be better than looking out the window! I own a 4m tiller steer tinny but I like chasing snapper and pelagic fish in Moreton Bay. To do this I need wind speeds less than 10 knots and preferably no rain, but even though I live on Bribie Island, less than 15 km as the crow flies from where I do a lot of my fishing, it’s no good poking my head out the window to check what the weather is doing. Before I began to use internet technology, plenty of times I had a gentle 3 or 4 knot breeze at home or at the boat ramp in Pumicestone Passage, only to find 15 to 18 knots of north-easter when I got out into the bay, making it unfishable for me. The lesson here is that wind and rain can be very localised, but there is no need to guess about these things today when real time wind speed and rainfall data are available on the internet. Now I just check the weather online before hooking up the boat. Even when out on the water, for those of us with internet access on mobile phones or on your boat via satellite, the latest weather predictions are just a keystroke away.

The Bureau of Meteorology (BOM) website has several useful tools which enhance my safety, comfort and chances of catching fish when on the water. Besides the usual weather forecasts and satellite imagery, it has dedicated marine weather services and very useful real time observations such as rain radars in locations around the country. Each of these radars shows rainfall intensity, as well as observations on wind speed and direction from various weather stations in the area. The radar locations tend to overlap on the 512km setting, so the service is available virtually everywhere, and on one page you can view the rainfall loop for the entire country! Amazingly powerful technology which allows the angler to become virtually omnipresent – everywhere at once!

I have found other websites equally useful for longer term planning of fishing trips. If I want to plan trips up to seven days ahead, one of the best sites is This site is slanted towards all on water activities by providing not only real time wind and wave data, but also tide and moon data as well as basic sea surface temperature readings for the entire country. By having weather as well as tide and moon data all in one place, this information will give you a better chance of planning your day off to coincide with favourable weather and tides. Longer range weather forecasting is also available on the BOM site and others, but the precision drops off markedly and while they may be able to define major events, exact dates for weather phenomena become elusive more than a couple of weeks ahead.

There are also other more specialised services available, mainly in the area of satellite measurement of sea surface temperatures (SSTs), ocean currents and fronts and ocean colour (phytoplankton abundance which relates to nutrient levels). These can be invaluable “roadmaps” for those chasing pelagic fish offshore. Most of the highly detailed services of this nature are paid for services, though the CSIRO does has some free services which include a SST and ocean current service, which includes some quite in-depth analysis via the ARGO float program.

A sea surface temperature chart showing the East Australian Current moving south along the coast.

The theory behind these services is that pelagic fishes like tunas and marlins have known optimal water temperature preferences. But finding the right water temperature is only one part of the puzzle. To find the pelagic predators you need to find the bait they are feeding on, and the baitfish will be concentrated in areas where plankton is abundant. The plankton abundance is related to nutrient levels which are associated with upwellings and ocean fronts that occur between nutrient poor warm water and nutrient rich cold waters, so interpolation of water temperatures, current direction and nutrient levels (the latter using “ocean colour” which is a measure of phytoplankton abundance) is required in order to determine the most likely locations to capture pelagic predators. The analysis can be further fine tuned using additional data on sub surface temperatures, thermocline depth, and salinity. Of course, it takes time for the pelagic food chain to kick into gear even when all conditions are optimal, so it requires expertise backed up by regular ground truthing to perfect prediction of where the fish are at, which is why it can pay to subscribe to the specialist services which do the legwork for you. They can more than pay for themselves in saved time and fuel as well as improved fishing success.

Cold snaps can trigger impoundment “bites”.

Weather & fish
All anglers can benefit if they link weather observations together with a basic understanding of their target species and how they might be influenced by weather phenomena. Let’s look at the main variables and their possible effects on fish.

Temperature: Water temperature has a direct influence on fish feeding, prey availability, timing of spawning migrations and so on. Each fish species has its own preferred water temperature range and each individual fish is acclimatised to a particular water temperature. Rapid increases or decreases in water temperature out of the range the fish is acclimatised to will put the fish off the bite and possibly even threaten its wellbeing if the water temperature swings too low or high. The exceptions to this rule are few, mainly relating to pelagic tunas and large sharks which up to a certain point are able to regulate their body temperatures independent of that of the surrounding water. As a rule of thumb, water temperature fluctuations will be larger and more rapid in shallower waters and smaller water bodies.

Wind: Wind is movement of atmospheric air from areas of high pressure to low pressure. Because of the rotation of the Earth, the movements of air do not occur in straight lines from high to low, instead winds in the southern hemisphere radiate outwards from high pressure areas in an anti-clockwise fashion and towards low pressure areas in a clockwise motion. Some anglers swear that bite times in some fish species are linked to the barometer, with fish biting if the barometer (and thus air pressure) is high or rapidly changing. While events such as cold fronts and thunderstorms indeed may influence fish behaviour, it may not actually be the change in atmospheric pressure that the fish are responding to, as the atmospheric pressure changes are minute compared to the water pressure changes caused by movements of the tides and moon, or even changes in water quality due to rainfall events or simple changes in wind direction. Indeed, the fish might instead be responding to changes in light intensity or wind direction, especially as wind has a direct and near instantaneous influence on water conditions.

Close monitoring of synoptic weather charts will certainly acquaint you with predicted wind speeds and directions. From there you need to begin to visualise what this might be doing to the water you want to fish. Wind not only affects wave heights, but it pushes surface water around. For example, in some parts of Australia strong offshore winds can push warm surface waters far off the coast, generating upwellings of cooler nutrient rich water near the coast. This can shut the inshore areas down in the short-term if target fish species prefer warmer water temperatures, but offshore anglers might find the front between the cool upwelling and warmer waters offshore suddenly becomes particularly productive for pelagics. Conversely, periods of onshore winds can push warm water inshore, spicing up action for pelagics near the coast.

Australian bass feeding habits are affected by weather conditions.

In lakes and impoundments the wind also plays a crucial role in affecting water conditions by causing major shifts in the position of the thermocline or complete mixing of entire lakes over short time scales (daily or weekly). Even moderate winds create surface currents which generate upwellings of water at the upwind side of the lake (to replace the surface waters which have been moved downwind). These upwellings tilt the thermocline towards the surface, reducing the area available to fish, and can even push the cold, oxygen poor water from below the thermocline all the way to the surface. Fish will avoid the area completely if the water upwind is too cold or low in oxygen. Bottom waters can also contain naturally occurring toxic compounds such as hydrogen sulfide. Both low oxygen and natural toxic compounds can result in localised fish kills if conditions change too rapidly for fish to avoid areas of upwelling.

Rain: Rainfall is arguably the most important weather variable which can affect fish behaviour in freshwater areas and estuaries. In rivers and lakes the effects of heavy rainfall events on the distribution and activity levels of fish will vary depending on the circumstances. For example, native fish in rivers are usually quite active when water levels rise as long as the temperature and oxygen levels remain in their comfort zone. However, this may not be the case in some impoundments where storms with high winds and rain may “dilute” the fish by breaking up stratification and drastically increasing the volume of water. Strong winds can also produce strong enough surface currents to tilt thermoclines and bring oxygen poor water to the surface, while strong inflow from rivers can break up stratification, stirring up anoxic bottom waters and put the fish off the bite.

Heavy rainfall can also affect fish in estuaries and inshore waters near coastal bars. In these cases salinity and water clarity can drop dramatically in very short periods of time. Flood waters may also be turbid, low in oxygen and have abnormal pH, especially in areas which have acid sulphate soils and/or large land use changes.

Historically, flood events bought life by flushing out rivers, spreading nutrients into the sea and boosting recruitment of inshore fish species. However today, sadly, in many parts of the country the extent of urbanisation, land clearing and agriculture is so great that the frequency and intensity of fish kills during flood events is increasing. When riparian areas and floodplains are modified, instead of draining slowly back into our rivers through coastal wetlands and intact riparian vegetation, the floodwaters now race back into our rivers, bringing with them a cocktail of pesticides and other chemicals that can deform and kill fish larvae, while low dissolved oxygen levels can trap estuarine fish and result in 100 per cent kills of adult fish.

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