Post by yihunt on Mar 30, 2008 18:03:46 GMT -4
Trout can be indiscriminating or finicky, depending upon conditions
Sunday, March 30, 2008
By Scott Shalaway
Just as hunters anticipate deer season and birders look forward to spring migration, anglers count the days until the opening day of trout season (April 12). As March closes and April begins, the clock is ticking.
Whether fishing with flies, baits or lures, it helps to have at least a passing knowledge of trout feeding habits and diet.
Trout eat a wide range of foods. They are dietary generalists. The only limit is the size of the mouth. Smaller trout eat smaller prey; larger trout eat larger prey. For any given mouth size, larger prey are preferred because they have more nutritional value.
Trout food can be classified into three general types: small aquatic insects and invertebrates, terrestrial invertebrates that fall onto the water's surface, and larger prey such as crayfish, fish and frogs. Lures and flies are designed to mimic these various natural foods.
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As springtime water temperatures increase, "invertebrate drift" increases. This refers to the insects and invertebrates that drift downstream with the current. It includes larval stages of mayflies, stoneflies, caddisflies, crane flies, midges and various invertebrates. These insects may spend months to years as aquatic larvae before metamorphosing into adult insect form. Most live a relatively short adult life where reproduction is the primary activity.
During the transition from larvae to adult, myriad insects drift along the water's surface waiting to be eaten. Those that survive and transform into adults swarm into breeding frenzies near the water's surface until eggs are deposited into the water and the invertebrate life cycles are renewed. While adult insects swarm above the surface to breed, they are vulnerable to hungry, leaping trout.
Later in the season as insect reproduction wanes, terrestrial insects that fall onto the water's surface become a more important food source. This list includes ants, bees, wasps, true bugs, beetles, grasshoppers and crickets.
And, of course, adult aquatic insects such as water striders, water boatmen, backswimmer, dytiscid beetles, whirligig beetles and crayfish of various sizes are important prey whenever they are active.
The key to success for any predator is to synchronize feeding activity with prey activity. Because trout are primarily visual feeders and invertebrate drift peaks at dawn and dusk, trout feed most aggressively at those times. Anglers hoping to tempt hungry trout should time their efforts accordingly. Trout feed most aggressively at low light levels because that's when food is most available. But trout are like my dogs -- they eat almost continuously if food is available. Because some subsurface invertebrate drift continues all day long, even mid-day fishing can be rewarding. This is when the skill and experience of the angler becomes most important.
Though trout are opportunistic feeders, they do make choices. Under daylight conditions, trout can distinguish colors. In laboratory experiments they can distinguish different types of food based on color. Individual preference varies, so I can't put you on to the "best" color for lures and flies.
Trout also select prey based on size, regardless of prey abundance. In the laboratory, trout select larger prey (mealworms or crickets) even if small prey such as brine shrimp were super abundant. Perhaps taking fewer, big prey is more cost-effective from an energetic standpoint than the energy required to take many small prey.
Interestingly, however, it takes trout time to distinguish variations in prey size. In experiments, brown trout did not respond immediately to larger prey. It took five to 25 minutes while anywhere from 25 to 250 larger prey drifted by before the trout attacked.
The lesson here is that anglers should exercise patience when changing lures and flies.
Prey palatability also affects prey choice by trout. In other experiments, brown trout were given a choice between drifting mealworms and tent caterpillars. Even when the caterpillars were five times more abundant than mealworms, trout chose mealworms. Presumably, caterpillars covered with irritating hairs are less palatable than mealworms. With a few exceptions, most birds show a similar aversion to hairy caterpillars.
The array of flies and lures on display in the fishing department of an outdoor store can be confusing. But when the complexities of food choice by trout are considered, it's easier to understand why fishing can seem so complicated.
Sunday, March 30, 2008
By Scott Shalaway
Just as hunters anticipate deer season and birders look forward to spring migration, anglers count the days until the opening day of trout season (April 12). As March closes and April begins, the clock is ticking.
Whether fishing with flies, baits or lures, it helps to have at least a passing knowledge of trout feeding habits and diet.
Trout eat a wide range of foods. They are dietary generalists. The only limit is the size of the mouth. Smaller trout eat smaller prey; larger trout eat larger prey. For any given mouth size, larger prey are preferred because they have more nutritional value.
Trout food can be classified into three general types: small aquatic insects and invertebrates, terrestrial invertebrates that fall onto the water's surface, and larger prey such as crayfish, fish and frogs. Lures and flies are designed to mimic these various natural foods.
--------------------------------------------------------------------------------
As springtime water temperatures increase, "invertebrate drift" increases. This refers to the insects and invertebrates that drift downstream with the current. It includes larval stages of mayflies, stoneflies, caddisflies, crane flies, midges and various invertebrates. These insects may spend months to years as aquatic larvae before metamorphosing into adult insect form. Most live a relatively short adult life where reproduction is the primary activity.
During the transition from larvae to adult, myriad insects drift along the water's surface waiting to be eaten. Those that survive and transform into adults swarm into breeding frenzies near the water's surface until eggs are deposited into the water and the invertebrate life cycles are renewed. While adult insects swarm above the surface to breed, they are vulnerable to hungry, leaping trout.
Later in the season as insect reproduction wanes, terrestrial insects that fall onto the water's surface become a more important food source. This list includes ants, bees, wasps, true bugs, beetles, grasshoppers and crickets.
And, of course, adult aquatic insects such as water striders, water boatmen, backswimmer, dytiscid beetles, whirligig beetles and crayfish of various sizes are important prey whenever they are active.
The key to success for any predator is to synchronize feeding activity with prey activity. Because trout are primarily visual feeders and invertebrate drift peaks at dawn and dusk, trout feed most aggressively at those times. Anglers hoping to tempt hungry trout should time their efforts accordingly. Trout feed most aggressively at low light levels because that's when food is most available. But trout are like my dogs -- they eat almost continuously if food is available. Because some subsurface invertebrate drift continues all day long, even mid-day fishing can be rewarding. This is when the skill and experience of the angler becomes most important.
Though trout are opportunistic feeders, they do make choices. Under daylight conditions, trout can distinguish colors. In laboratory experiments they can distinguish different types of food based on color. Individual preference varies, so I can't put you on to the "best" color for lures and flies.
Trout also select prey based on size, regardless of prey abundance. In the laboratory, trout select larger prey (mealworms or crickets) even if small prey such as brine shrimp were super abundant. Perhaps taking fewer, big prey is more cost-effective from an energetic standpoint than the energy required to take many small prey.
Interestingly, however, it takes trout time to distinguish variations in prey size. In experiments, brown trout did not respond immediately to larger prey. It took five to 25 minutes while anywhere from 25 to 250 larger prey drifted by before the trout attacked.
The lesson here is that anglers should exercise patience when changing lures and flies.
Prey palatability also affects prey choice by trout. In other experiments, brown trout were given a choice between drifting mealworms and tent caterpillars. Even when the caterpillars were five times more abundant than mealworms, trout chose mealworms. Presumably, caterpillars covered with irritating hairs are less palatable than mealworms. With a few exceptions, most birds show a similar aversion to hairy caterpillars.
The array of flies and lures on display in the fishing department of an outdoor store can be confusing. But when the complexities of food choice by trout are considered, it's easier to understand why fishing can seem so complicated.