Catching Clustered Critters
Ann Arbor, MI — "Birds of a feather flock together," the old adage goes. So too do many species of fish and aquatic invertebrates, which gather in smaller clumps or clusters within a population.
This can present problems for researchers studying these populations, because traditional methods require that samples be taken in a random manner from within the inhabited area, to ensure that the results are not biased by the selection process.
The random approach to sampling works well for species that are not found in clusters, but results in low catch rates for those that are.
A sampling method, called "Adaptive Cluster Sampling," has been developed for animals that exhibit a clumped distribution. It targets effort in places where capture is most likely, while accounting for the bias that this type of non-random sampling would normally cause
"After they hatch, sea lamprey larvae live in burrows they construct in sandy and muddy areas of stream bottoms," says Paul Sullivan, a biologist with Fisheries and Oceans Canada at the Sea Lamprey Control Centre in Sault Ste. Marie, Ontario. "Within these areas, lamprey larvae are not randomly distributed, but are found in clusters. Adaptive Cluster Sampling allowed us to collect more larvae per sample, which in turn, provided better estimates of larval density and will improve our understanding of their specific habitat requirements."
This method will prove useful to researchers that have previously been frustrated by low capture rates when sampling species with clumped distributions. In these cases, it is undoubtedly true that "a bird in hand is worth two in the bush."
Original Publication Information
Results of this study, "Adaptive Cluster Sampling: Estimating Density of Spatially Autocorrelated Larvae of the Sea Lamprey with Improved Precision," are reported by W. Paul Sullivan, Bruce J. Morrison and F. William H. Beamish in the latest issue (Volume 34, No. 1, pp. 86-97) of the Journal of Great Lakes Research, published by the International Association for Great Lakes Research, 2008.
Contacts
For more information about the study, contact Paul Sullivan, Sea Lamprey Control Centre, Fisheries and Oceans Canada, Sault Ste. Marie, ON P6A 6W4; Paul.Sullivan@dfo-mpo.gc.ca, (705) 941-3010.
For information about the Journal of Great Lakes Research, contact Marlene Evans, Editor, National Water Research Institute, 11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada; editor@iaglr.org; (608) 692-1076.
Links
Since 1967, IAGLR has served as the focal point for compiling and disseminating multidisciplinary knowledge on North America's Laurentian Great Lakes and other large lakes of the world and their watersheds. In part, IAGLR communicates this knowledge through publication of the Journal of Great Lakes Research, available to members in print and electronic form. A searchable archive of the journal is available online and includes the abstracts of articles from the journal's inception in 1975 through the most recent issue. In addition, complete articles are available to members who have signed up for an electronic subscription.