material on the bottom of the fishery and is a major component in reservoir aging . It can impact a fishery in several ways , including a reduction in shallow spawning areas .
Bass often prefer to spawn in the backs of pockets , and over time , pockets can silt in . This makes them less suitable for spawning , which at a large scale can impact bass populations through loss of spawning habitat .
Many reservoirs are also designed for water storage , and deposition reduces water storage capacity . This has municipal impacts , particularly combined with widespread drought like is happening in much of the West right now . Low water also limits angling access , as many ramps are only usable at certain water levels .
Finally , on reservoirs used for major transport , deposition can impact shipping and navigation . Similarly , it can be harder to get your boat into prime fishing areas due to siltation . Many marinas and canals often need to be dredged to remove new layers of silt , which is costly to stakeholders .
erosion
Wave action , rising and falling water levels over time and lack of a wetland buffer can cause some significant erosion problems in reservoirs as they age . This has impacts throughout the system , including habitat homogenization and barren littoral habitats .
When shoreline erosion gets bad enough , it reduces riparian wetlands , prevents or negates growth of aquatic vegetation and causes bank sloughing or caving . Over time , this causes long stretches of bank to become featureless . Older reservoirs with erosion problems have much less unique shallow habitat than younger and less-eroded reservoirs . Lack of unique shoreline habitat creates a less habitable place to be if you ’ re a fish , creating “ barren ” areas up shallow where very few fish spend any time .
habitat loss
Bass are crafty and adaptable , which is why they thrive in such diverse places . As reservoirs age , however , they become much less diverse , and deposition and erosion lead to poorerquality bass habitat . Specific examples include loss of woody cover , siltation in hard-bottom areas and decreases in water clarity .
Wood ( brush , standing timber , laydowns or stumps ) is classic bass habitat . Over time , wood degrades and standing timber gets knocked down by wave and ice action . This naturally leaves bass with fewer places to hide .
Rock piles , gravel patches , shell beds and even stumps are also prime bass country . Siltation covers them up over time , too , turning spots that were once loaded with bass into featureless ghost towns .
Erosion and lack of shoreline vegetation can cause turbulent water , and high nutrient runoff can cause algae blooms in older reservoirs . Those can also impact a fishery from a productivity perspective and change the techniques and presentations that are most effective for chasing bass .
Unfortunately , understanding how reservoirs change through the years doesn ’ t change the fact that many of the effects are irreversible . As bass anglers , we simply need to find ways to understand and adjust to the everchanging waters we fish on a regular basis .
THE “ NEW RESERVOIR EFFECT ”
In 2008 , the Toyota Series Southwestern Division fished a fourday event on Falcon Lake in southern Texas ( the reservoir spans the border of Texas and Mexico ). The result : four anglers topping the century mark , including a 110-pound , 2-ounce bag from winner Jeremy Guidry .
That tournament took place during a period when Falcon Lake was experiencing what fisheries biologists call the “ new reservoir effect ,” and was just one of many record-shattering events on what was then probably the best bass fishing lake in the world .
Throughout the 1990s , Falcon Lake ( and southern Texas in general ) went through an extended period of intense drought that led to low water for years at a time . During that time of low water , dense vegetation grew along the shoreline . In 2004 the rains came , and the lake started to rise , inundating all that brush .
By 2008 , the lake was full and nutrients from all that flooded brush combined with endless shallow cover and created an explosion of life that led to several years of epic fishing .
While not very common , the new reservoir effect happens from time to time as nature experiences major swings within its regular cycles . We can ’ t do much about the negative effects of reservoir aging on our favorite fisheries , but we can still take advantage of the positive changes in other reservoirs throughout the country .
PHOTO BY BRETT CARLSON
Jeremy Guidry
OCTOBER-NOVEMBER 2021 | MAJORLEAGUEFISHING . COM 31