Case Studies in Fisheries Conservation and Management: Applied Critical Thinking and Problem Solving
Case 20: Standardized Sampling: Lake Meredith, Texas
Many biologists have to deal with clumped distributions of organisms when designing a sampling program, and fishery biologists are no exception (Brown and Austen 1996). Because we tend to have so much variation in samples among individual net catches or individual electrofishing stations, many fishery management biologists use standardized sampling procedures (Bonar et al. 2009). Under this concept, standardized sampling means that sampling gears are chosen to effectively sample the target species and that the same gears are used, to the extent possible, at the same sites, at the same times of year, and from year to year.
Fishery biologists often hotly debate the proper method for selection of sampling sites. Some biologists prefer to subjectively choose sampling sites that they believe will yield substantial numbers of target organisms, while others believe that sampling sites should be randomly selected. Even among the group of biologists who believe in random site selection, there still is disagreement. Some biologists will randomly choose the sampling sites, and then return to those same sites in subsequent years, while others argue that a new group of random sites should be selected and sampled each year.
Regardless of these disagreements, the purpose of standardized sampling is to minimize variation due to sampling device efficiency and seasonal changes in sampling data. In this way, long-term trends in population structure and dynamics can be more reliably monitored. While a one year increase or decrease in catch per unit effort for a target species may not cause alarm, a continuing trend in that increase or decrease over a 10-year period certainly would be a concern.