Population Studies one of the oldest and most important goals of fisheries managers is to assess the abundance , size and age of a population of bass . they do that using three main techniques .
1 . Electrofishing : electrofishing or “ shocking ” is one of the most common ways that fisheries biologists collect and study fish in the wild . introducing a highvoltage current into the water causes involuntary muscle contractions in fish , essentially stunning them , which allows biologists to catch them in nets . electrofishing is harmless to fish , and they quickly recover and swim away .
2 . Mark recapture studies : Mark recapture is one of the most common ways of estimating the population of fish in a water body . at their simplest , mark recapture studies involve fishery managers going out and catching a bunch of bass – whether by shocking , netting or some other method that allows live release . Biologists “ mark ” each captured bass using a tag , fin clip or some other method and then release them back into the fishery . after a certain period of time – often just a week or two – researchers return to the study area and repeat the capture process to assess how many recaptures they have ( bass that were previously tagged , clipped , etc .). Based on that information and standard industry formulas , they can calculate an estimate of the total population size .
In the electrofishing process , bass that are momentarily stunned float to the surface unharmed and are netted by fisheries biologists .
3 . “ Aging ” bass : another important factor that biologists use in fisheries management is the age structure . this is a major factor in assessing the overall health of a fishery , as the healthiest fisheries have a diverse age population with ample numbers of different age groups . to learn this , biologists first determine the age of the bass they examine . there are several ways they do this . the most accurate way is through counting the rings on a fish ’ s otolith – or “ ear bone .” each year a fish lives , new calcium carbonate is accreted , and , similar to counting the rings of a tree to determine its age , biologists can count the layers of the otolith to figure out how old a fish is . similarly , fish scales also develop a ring pattern of growth that can be used to determine age .
Behavior Studies outside of age and abundance , biologists also want to know things about bass such as what types of habitat they favor , what prey species they most prefer in a particular water body or season , and how they move throughout their environments both daily and seasonally . to study this , biologists use a variety of techniques .
1 . Gastric lavage : understanding what bass are eating can be an important part of managing the resource in whole . the best way to do that is to analyze the stomach contents of captured bass . other than performing a necropsy , biologists
In mark recapture studies , fish are caught and then marked somehow or affixed with a small tag ( such as the yellow tag shown here ). use a technique called “ gastric lavage ” to do this . similar to “ stomach pumping ” performed on humans , a small amount of water is flushed down the fish ’ s throat , which causes it to empty its stomach contents for study .
2 . Telemetry : to study bass behavior and location , biologists rely on telemetry , in which a data logger that transmits location and other data to a receiver is affixed to a fish . telemetry technology has come a long way from the old days , providing researchers with the means to record speed , position , depth and acceleration , and even log video .
Angler Studies although it ’ s less “ science-y ,” studying angler behavior is also a major part of modern fisheries science . By understanding the number , type and preferences of anglers , biologists can learn more about the fisheries they service , and also better establish regulations . the most important tool in angling-related science is the creel survey . if you ’ ve fished long enough , you ’ ve likely participated in one , typically where a manager asks questions or has you fill out a survey at the ramp when getting off the water . these data help establish population estimates , which species anglers are targeting and “ catch per unit effort ,” which is helpful in gauging the overall quality of a fishery .
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