Where the Fish Are: An Angler's Guide to Fish Behavior - Softcover

Bagur, Daniel

Softcover

ISBN 10: 0071592911 ISBN 13: 9780071592918

Verlag: International Marine/Ragged Mountain Press, 2009

Inhaltsangabe

More science and less art leads to bigger fish and fewer tales

Most anglers rely on advice from fishing buddies or books by well-known but unscientific anglers. Here is a book that distills the science of fish behavior into easy-to-follow advice on how to catch fish in any situation. Describing how feeding behavior in fish changes in response to fluctuations in dissolved oxygen, turbulence, turbidity, temperature, light, noise, and other factors, Bagur advises you on how to respond, recommending specific flies, baits, rigs and tactics.

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Daniel Bagur is a marine and freshwater biologist, avid angler, and regular contributor to the international angling press. He works in fisheries in the United Kingdom, is the resident expert on fish behavior for a leading U.K. fishing magazine, writes columns for Canadian and British publications, and has published feature articles in dozens of magazines worldwide.

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WHERE THE FISH ARE

An Angler's Guide to Fish BehaviorBy DANIEL BAGUR

The McGraw-Hill Companies, Inc.

Copyright © 2009 Daniel Bagur
All right reserved.
ISBN: 978-0-07-159291-8

Contents

Chapter One

How Fish Work, Behave, and Think

Fish are highly evolved creatures that have adapted to the aquatic environment physiologically and behaviorally over millions of years. The significant differences between their aquatic and our terrestrial worlds mean that fish are influenced by factors we may not even consider.

Knowledge of fish behavior and physiology is a vital part of an angler's skill set. Understanding how a fish works and what environmental cues fish are likely to be attracted to or repelled by enables an angler to put him- or herself into the fish's world, making every angling decision a little easier and improving the chances of a catch.

Of course, a reasonably complete overview of either fish behavior or anatomy alone would require a textbook in itself. What follows, therefore, is limited to those factors that have the greatest influence on angling.

Breathing and Metabolism

People use lungs to breathe air that, at ground level, has a more or less fixed and steady oxygen content. Fish, on the other hand, experience huge fluctuations in the levels of available oxygen. To make matters more complicated these fluctuations occur over relatively short time periods. These changes are due in part to the relationship between the temperature of water and its ability to hold oxygen. The warmer the water, the less oxygen it can hold.

Freshwater fish experience much higher oxygen fluctuations than their salt-water counterparts because it takes longer to heat or cool a larger volume of water. Smaller bodies of water, such as streams and small lakes, warm up and cool down more rapidly in response to the warming and cooling of the air and land around them.

Fish are well adapted to cope with these natural changes as they occur. Such changes do, however, influence where fish choose to spend their time and when they feed.

Gills

There are two main problems associated with obtaining oxygen from water. First, water contains less oxygen than air, around one-thirtieth as much per unit of volume. Second, water is denser than air. This makes it more difficult for fish to extract oxygen from water than it is for air breathers to extract oxygen from air. Through evolution, fish have gotten around these challenges by increasing the surface area of their respiratory organs and by pumping larger volumes of water over their respiratory surfaces.

A fish's gills are designed to expose as much surface area as possible to passing water, thereby maximizing the exchange of gasses between the fish's blood and the water. Each gill arch is covered by a strip of gill filaments, each filament is folded into a V shape to increase its surface area, and the filaments are covered in folds to further maximize their surface area. The membranes of the gill filaments are very thin, which further aids gas exchange. Species that lead more active lives, such as trout and bass, tend to have a greater number of gill filaments than less active species, providing them with the greater volume of oxygen needed to generate more energy.

As in humans, the red blood cells of fish contain a respiratory pigment called hemoglobin, which enables the blood to transport oxygen. Once the blood has passed through the gills, it is transported through the fish's body, where it provides the organs with their required oxygen.

The surface area of the gills is also used by fish to purge unwanted by-products of respiration from their blood. Carbon dioxide in the blood passes through the gill membranes and is absorbed by the surrounding water, while oxygen from the surrounding water passes through the membranes and is absorbed by the blood.

Water is pumped over the gills in two ways. Fish gulp a mouthful of water and then pump it into their gill chambers, where it passes over the gill filaments and back out into the environment. Some of the more active fish species, like bass and salmonids (including salmon, trout, char, and grayling), supplement this mechanism with another called ram ventilation. While swimming slowly or hovering at rest, fish pump water over their gills as described, but when swimming at speed, they open their mouths and allow water to "ram" through their gills, increasing the volume of oxygen available to the blood. The gill structure of fish. The rakers filter out debris and keep it from damaging the filaments, where gas exchange between the fish's blood and the water occurs.

Metabolism

Wind strips heat from terrestrial animals in cold conditions much faster than cold air alone. In the same way, mammals swimming in fast-flowing water will lose heat faster than those in still water. For fish, this is not a problem, because fish are cold-blooded—that is, their body temperature rises and falls to remain in equilibrium with the surrounding water. This means that, unlike birds and mammals, fish do not need to expend energy maintaining their body temperature in a cold environment. This energy saving is highly advantageous, particularly in waters where temperatures fluctuate regularly.

During cold weather, fish simply reduce their activity levels. Since they do not need to waste energy maintaining their body temperature, they are able to feed less and keep still until temperatures return to more favorable levels. Because of this, fish seek out places that don't force them to waste energy during the winter. This often means moving into deeper water, where they can hide from predators and avoid currents that exist higher in the water column.

This behavioral pattern is mirrored somewhat by other species. Some aquatic insects, for example, burrow in pond mud when temperatures drop, enabling them to overwinter and survive for a number of years. Similarly, soil insects dig deeper, and tree beetles burrow beneath bark. The basic strategy used by these animals is to put as much distance and matter (be it mud, bark, or overlying water column) between themselves and the greatest extremes of cold. These creatures also move very little during the cold weather in order to conserve energy.

The range of temperatures fish can withstand is generally much smaller than that of terrestrial animals. This is because of the high rate of heat exchange between an aquatic animal and surrounding water. Terrestrial animals are surrounded by air, which has a lower rate of heat exchange, and can therefore survive low temperatures for longer.

Temperature further influences the feeding regimens of fish by determining the behavior of many of their prey species. This point can be illustrated in broad but graphic terms by considering the role of temperature in shark attacks on people. When the water is warm, people spend more time swimming and venture farther from shore. This behavior raises the encounter rate between human swimmers and sharks, and as a result, the number of mistaken attacks increases.

The situation is similar for freshwater fish. Temperatures affect the behavior of the invertebrates upon which these fish feed in a way that influences encounter rates between them and their food. As a general rule, the warmer the water, the greater the activity levels of invertebrates and the higher the level of feeding activity by fish, which in turn increases encounter rates between foraging fish and predatory ones.

The level of a fish's hunger can influence its position within the...

Details zur Ausgabe

• Verlag: International Marine/Ragged Mountain Press
• Erscheinungsdatum: 2009
• Sprache: Englisch
• ISBN 10: 0071592911
• ISBN 13: 9780071592918
• Einband: Taschenbuch
• Anzahl der Seiten: 176
• Kontakt zum Hersteller: Nicht verfügbar
• Verantwortliche Person: Nicht verfügbar