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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