Barometric Pressure

The effect of barometric pressure on fishing feeding activity is one of the more interesting theories. In short, the theory proposes that a dropping air pressure brings on feeding activity, rising pressure turns the fish off feeding, high pressure results in the fish moving to shallower water, and low pressure results in fish moving to deeper water. This article will provide an overview on barometric pressure, summarize various theories about why atmospheric pressure affects fishing activity, and then summarize in tabular fashion the generally accepted fish behaviors with various barometric patterns.

Barometric pressure is the measure of the weight of the atmosphere above us. A barometer is used to measure air pressure. The earliest barometer consisted of a glass vacuum tube inserted into a container of mercury which was exposed to the pressure of the air. Increased air pressure would force the mercury up the tube in a height proportional to the pressure. The height was measured in inches (inHg) or in millibars (1 inch = 33.864 millibars). Although new types of barometers are now used, these measures are still in place. In general, 30 inHg or 1016 millibars is considered to be normal air pressure. In normal weather, 30.5 is considered extreme high, and 28.5 is considered extreme low. The measures are taken at sea level, a higher elevation has less atmosphere above it, so a correction factor against the normal measure is needed depending on altitude.

It is believed that the effect of barometric pressure is greater in shallow water than deep, probably due to the pressure of the weight of the water in deep water being so high, that the air pressure above it is not relatively significant.

The principal theory, is that the effect of changing pressure on the swim bladders of fish makes them uncomfortable or dis-oriented. In this theory, the fish will move to feel well, or they feel bloated or full. With a lowering barometer, it is believed these fish move into deep water seeking higher water pressure and ride out the low pressure around structures. The theory suggests that just prior to change from a high to a low, fish will bite like crazy until the low hits and then stop. The difficulty with this theory, is that water is 900 times more dense than air, and generates significantly more pressure than air. In fact, a 3 foot wave will produce a variation of pressure more significant than can be expected from a change in atmospheric pressure through a dramatic change, and the wave effect is happening every few seconds, rather than the hours or days that the atmospheric changes takes to occur.

Frankly, given that the pressure of water depth is such a significantly greater factor than the pressure of atmosphere, it seems likely that the weather conditions created by changes in barometric pressure, such as clouds, rain and wind, have more effect on fishing than the barometric pressure alone. So in the opinion of the author, barometric change is a good indicator of fishing change, but it's not because of the pressure change by itself, as much as what other weather conditions are likely to occur because of the pressure change.

The following table attempts to summarize the barometric pressure, and observations on fish activity and fishing techniques.

Wind Effect on Fishing

Wind is a condition for fishing that can make many anglers uncomfortable. A strong wind combined with rain, is sure to get you soaking wet. Trying to maneuver a boat in the wind is difficult, and in the case of engine failure, wind can get you in serious trouble in a hurry. High winds create high waves, which can swamp your boat. It's too windy to fish when you can't realistically be safe on the water. Otherwise, you need to understand what fish are likely to do in the wind, adjust your fishing patterns accordingly, and understand when it's time to get off the water.

The wind can help energize a quiet fishery, especially if it is preceded by calm, warm weather. Undisturbed water can suffer from a lack of oxygen. Wind starting to beat on shorelines and structure, can inject oxygen into the water. In particular, structure like timber and trees in the water can really cause a disturbance of the waves, bringing up oxygen levels, baitfish, and of course predators. Also, the wind blowing consistently against one shore will push plankton and feed towards that shore, in addition to raising the oxygen level in that area.

Wind and wave also break up a mirror surface, making fish less spooky from boat movement, and wading. However, waves lapping on an aluminum boat can be quite noisy, and you need to think of this when positioning your boat around fish. The wind can also create a mud line off a muddy bank, which can attract some fish species, which will lie in the edge of the mud line to ambush baitfish.

Strong directional wind can create current along shorelines, but it needs to be consistent and long-lasting to generate a current. As well, the wind needs to hit the shore at an angle to generate the current. Also, it can be easy to over-estimate how fast a current will be, a 30 mph wind might generate a .5 mph current, and a slower wind will generate a dramatically slower current. Fish will almost always point their head into the current, and you need to cast INTO the wind in order to bring your lure retrieve into the face of the fish. Generally, fish are reluctant to chase a lure which has come from behind it. Keep an eye on jutting points and cuts into the bank, because the current going over low water can be an area of high activity. As well, shallow humps and other disturbances can cause current patterns as the water is pushed around it.

Strong consistent directional wind which has blown for a long period will likely push the warmer surface water downwind, which will be replaced from upwind by colder deeper water. Consider how this temperature change might change the depth of species you were fishing recently.

Look for windy shores, if there appears to be a current running, try to fish upwind if you can. Between boat handling into the wind and casting upwind, this is easier said than done. You need to keep in touch with your lure on the retrieve, which suggests a fast retrieve on a heavier lure. Wind will make baitfish like Shad more active, select lures which imitate them.

Certainly don't lose focus on the fact that fishing in the wind in inherently more dangerous than in calm weather. There will likely fewer fishermen around to help you should you get in trouble, and the effect of the wind can be to swamp your boat or otherwise push it into trouble. Make sure your motor is running well, the electrics are charged, and that your emergency equipment and anchor are sufficient for the conditions.

So take advantage of those windy days. You might find that your favorite fishing spots are less crowded, and you may also find that other fishermen are not fishing the same windy spots that you are, creating a lot of room, and lot of active fish to keep for yourself.

Water Temperature

Most fish species are cold blooded, which means they do not and can not control their internal body warmth. As a result, their metabolism is strongly influenced by the temperature of their surrounding environment. A few species, bluefin tuna as an example, are somewhat warm blooded in that they can control the temperature of some organs by using muscle movement to generate heat. But as far as I know, most sport fish are cold blooded.

Given their cold-blooded nature, fish need to move to stay within their temperature comfort zone. Generally they do not need to move too quickly, because water has a high heat capacity, so generally change in temperature happens slowly. Fish then are rarely trapped outside their comfort zone, unless exceptional changes happen, such as a fish being caught in a small landlocked pool on a very hot day, or when there is a large draw-down of a reservoir.

Fish generally try and find their thermal optimum, i.e. that temperature which is not too cold or not too hot. The thermal optimum varies for different fish species, and many feel that larger fish in a species have a better cold tolerance, and this may be a factor why larger fish are generally deeper than smaller fish.

For migratory species such as Striped Bass, water temperature generating movement of their preferred prey species is the key indicator. However when the predatory fish reaches the final practical limit of it's range, for example in a large tidal estuary, temperature will be a significant factor in the fish moving inland, with larger fish generally being able to move early and leave late, given their supposed greater tolerance for colder water.

Many species of fish feed or congregate where there are differences in water temperature. The warmer water accommodates a temporary increase in their metabolic processes, while the colder water is more oxygenated. Certainly the fish can move between zones depending on whether or not they are actively feeding, or are less active. Certainly if their preferred prey species at any given time is higher or lower than optimal, the fish are going to go where the meal is. When the water temperature finally goes below their desired range, a semi hibernation takes effect, and fish activity drops off almost altogether.

The following table attempts to summarize the temperature comfort zone and thermal optimum for many sport fish species.

Solunar Theory

Solunar theory is one of the more interesting factors affecting fishing to consider. Solunar is short for SOlar LUNAR. Solunar theory essentially postulates that the position of the moon and sun effect fishing success. Many of the articles on solunar theory seem to be reprints of the same material, this article is intended to try and simplify the most relevant aspects of the theory in simple to understand language.

Daily Peak Times.

The theory is that when the moon is directly overhead, and directly underneath you (the other side of the world), there will be peak feeding periods. In addition, there are two periods of the day when the fishing is also good. Those are moon rise, and moon set.

If you have been watching the moon, you can predict yourself to some degree of accuracy when the peak times are going to be. But if you haven't been observing the moon or would like to predict in advance the peak periods, you need to know where you are in longitude/latitude, or the name of the nearest city. You can then look up the times in the tables provided free of charge by the U.S. Naval Observatory.

Monthly Peak Day

When the moon and sun are in the same sky, the gravitational pull of each works together, and causes the biggest overall solunar effect. The next best period is when the sun and moon are completely opposite each other. When they are in the same sky, you have a "new" moon, caused because the sun is behind the moon. The sun and moon being in opposite skies, results in a full moon.

Yearly Peak Month

In June, the solunar effect is the highest. During New Moon, both sun and moon travel the sky together, and during the full moon, the sun and moon travel completely opposite each other.

Ok, Now It's Getting Stupid Out There!

We know that dawn and dusk are also prime fishing times, and I particularly favor dawn. So when you have dawn and dusk hit at the same time that the moon is directly overhead or underfoot - ya, BINGO! And if it's a new moon overhead at dawn in June, why wouldn't you be fishing!

It Can't Be That Simple

You're right, it's not that simple. Weather, wind, sun, rain and lots of other factors also come into consideration and need to be kept in mind. Other articles in this serious attempt to line these factors up for you.

If in doubt?

Go fishing.

Water Clarity

The importance of water clarity on fishing success boils down to two things - the ability of fish to find your lure, and the size of the fish you are likely to catch.

Most of the predator fish that are popular game species, are sight feeders. By that, I mean that they rely on seeing their prey, be it minnows, crawfish, or leeches in order to catch it. There are a few species, such as catfish and sturgeon, which rely principally on the smell of their prey in order to feed. The sight feeders include bass, pike, muskie, trout, walleye, and salmon.

When water clarity is low, such as after a rainstorm which has caused suspended sediment to move into a river, pond or river, other effects of rattles or splashing are necessary to assist the fish in locating its prey.

The other main consideration of water clarity, is its effect on the fish carrying capacity of the body of water. If the water is crystal clear, it is usually an indication that it is not carrying enough microscopic life within it to feed a large population of fish. It may be possible that there are still large fish in the body of water though. Of course if you are fishing a body of water in which fish migrate for spawning, or where prey fish follow baitfish which are spawning, the fish carrying capacity of the body of water is temporarily skewed.

In general, a slightly green tinge to a body of water is ideal. The greenish water means that it is carrying a lot of microscopic organisms, in particularly Phytoplankton. The Phytoplankton is eaten by other small organisms like Zooplankton, which are eaten by bugs and larvae, which are eaten by fish fry and crawfish, and so on up the food chain. So there needs to be a continuous chain of feed right up to the fish you catch.

As well, another consideration for healthy water and a good place to fish, is that perhaps 20% of the water contains healthy weeds in season. Over 20%, and prey can hide extra easy making it hard for large fish to find feed. In addition, a very heavy bloom of growth may be a sign than an area is over fertilized, perhaps caused by leeching off waterfront properties, or agriculture.

So typically, you are looking for a body of water that doesn't have too much suspended solids, is slightly greenish, and has an overall clarity that allows fish to see perhaps 4 feet. In this ideal situation, there should be a good quantity of fish in the body of water, and they should be able to see your lures with no particular difficulty.

As fishermen and landowners, we have the capability and responsibility to ensure the water we fish has optimal carrying capacity and water clarity. In particular, we have the capability to affect suspended solids and ensure that water in not over-saturated with fertilizers leeching into the waterways. When we are running our boats in areas with exposed banks, we should slow down to ensure that as little washout as possible occurs. As land owners, we shouldn't clear brush and expose soil all the way to the water. And we have the ability to ensure we don't fertilize ground near the water where the fertilizer might leech into the water.

If in doubt?

Go fishing

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