The Cayuga Fisher

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Hot Knots

Never tie an improved clinch again.

The uni knot is versatile, easy to tie, and strong. Use it to tie on hooks or join two lines together with the double uni knot. Works great for tying dissimilar lines together or a leader to braid. For tying a braid backing to heavier mono or even a leader to braid the Red Phillips knot is faster and smaller.

The Water:  Seasonal Variations:  The Thermocline in Depth

Stratification Details  <=  Water Index  =>  Isothermal Winter

Seasonal Variations:  The Thermocline and Metalimnion

This layer of water is very important to the trout and salmonid fisherman.  Some species are found above it, some in it, and some below, but all will be in the general neighborhood most of the time.  The metalimnion undergoes a predictable seasonal evolution: forming in the depths in early spring, quickly rising to shallow water, deepening again through summer, and finally dissipating in late fall.  The width of this layer is variable and moves within the water column in response to wind and currents, but remains fairly unmixed while in place, as does the epilimnion and hypolimnion.

To examine how the thermocline sets up, it is useful to look at the shape of the lake bed.  Cayuga Lake, and most of the Finger Lakes, have long deep narrow basins, with shallower ends.  Cayuga has both a large Northern shelf and a smaller Southern shelf.  This is important for the initial creation of the thermocline in the lake, as the shelves warm first, before the main basin.  At some point this warm puddle meets the cold water of the main lake, and a sharp temperature change is found.  This should sound familiar to anyone who has fished a thermal bar in the Great Lakes in spring- the same effect occurs at either end of Cayuga Lake to a much smaller degree.  The metalimnion begins at either end and eventually meets in the middle of the lake, though this is somewhat dependent on yearly conditions.

When first formed the metalimnion is shallow and sharp.  An smaller scale example can be found in a pond, where the top three feet of water is bathtub warm, but if you stick your feet down they go numb from the chill.  This occurs on Cayuga too, with the boundary eventually reaching great depths.  Even though the layers themselves do not mix during summer, there is some "leakage" and limited heat exchange does occur, primarily through little eddies where they meet.  By this means heat is slowly transported into the deeper water. 

The diagrams at right should help visualize the seasonal progression. Please note these diagrams are not to scale!  In reality the hypolimnion occupies a far greater portion of the water column, and the epi- and metalimnion are relatively much thinner. 

In early summer these layers become more firmly established with very distinct boundaries.  Once established the epilimnion and metalimnion continue to grow into August.  Long days and a high sun angle mean a lot of energy is added to the lake.  This period also features the greatest biomass growth, of both plant and animal life, especially near the beginning, from May- early July.  Trout are within range and hungry, and the alewives are spawning too.  As high summer approaches this growth trend slows down, and so does the fishing.

By late summer the warm water has reached deep into the lake, forcing most trout below 80-100 feet.  The surface begins to cool in mid-late September as the nights become longer than the days.   The exact timing of this point varies from year to year due to amount of sun and the weather, but it remains near the equinox.  As the surface begins to cool it is more easily mixed into the subsurface layers because the density difference becomes smaller.  This same process allows the metalimnion to begin to mix into the hypolimnion.  The general cooling of the lake is characterized by a cooling surface and warming depths.

And here, in late fall or early winter, the epilimnion is fading and the stratification becomes very weak.  The surface may be 50 degrees while the depths are 45 degrees, not much of a temperature difference.  At this point the fish could be anywhere!  The baitfish, however, are mostly in deep water at this point, and many trout are too.  As the lake cools further, past this point, whatever gradient is left disappears and the lake mixes from top to bottom throughout the winter months.

In the first paragraph I stated the thermocline forms in the depths in early spring.  The temperature profile is very similar to the late fall and can be explained with this same picture.  The temperature may be 35° throughout the lake in February.  By April the lake is gaining heat and on a nice sunny day will warm the surface water.  For example, the top foot of water goes from 36° to 38 degrees Fahrenheit over the course of the day.  Since water is densest at 39°, that warmer water sinks and begins to collect on the bottom of the lake.  Just as the benthos (the deep zone) is the last to cool in fall, it is the first to warm in spring.  The thermocline first forms near the bottom, and rises as the 39° water continues to accumulate. 

The transition to a surface thermocline is relatively swift and takes place over a week or two.  Soon the lake is near 39° throughout and the warmer water floats to the top rather than sinking.  For a time wave energy can overcome the slight temperature gradient and mix heat into the subsurface water, but eventually the warm pancake forms and the season's stratification is complete.  (The winter period will be covered on the next page when I finish it.)

Stratification Details  <=  Water Index   |  Top  =>  Isothermal Winter

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