Studying Fish DNA in Water Samples Helps Researchers Estimate Multiple Species’ Biomass
A new study by NOAA Fisheries in partnership with the University of Alaska Fairbanks shows it’s possible to estimate fish biomass at once for more than one species, using environmental DNA.
The study, released by NOAA Fisheries on Oct. 31, found that researchers can estimate the abundance of ecologically and commercially important Alaska fish species — Arctic cod, walleye pollock and Pacific cod — which are difficult to distinguish in eDNA samples.
DNA, which stands for deoxyribonucleic acid, is a molecule found inside cells that carries the genetic information necessary for an organism’s development and function, essentially acting as a blueprint for all the proteins in an organism and passing this information from one generation to the next.
eDNA is the genetic material shed by organisms into the surrounding environment.
As a fish swims through the ocean, its DNA is shed and accumulates in the water around it. Some sources of eDNA include scales, skin cells, mucus, feces and gametes. A gamete is a reproductive cell of an animal or plant.
In animals, female gametes are called ova or egg cells, and male gametes are called sperm. All this genetic material can be recovered from environmental samples.
Kimberly Ledger, lead author and a research biologist with the Alaska Fisheries Science Center’s Auke Bay Laboratories, said it was learned through laboratory studies that species compositions and estimate biomass for different species of cod and pollock can be accurately quantified at the same time using eDNA, and that it is possible to apply these methods to other species to improve eDNA’s quantitative utility.
The central goal of managing species is understanding where they live and how many exist. Accurately estimating this information is difficult and relies on making inferences about an entire community based on observations of a subset of individuals, NOAA researchers said.
With eDNA, scientists are able to detect and quantify fish DNA from the environment to help estimate species abundance and biomass from just a sample of water, they said.
Scientists caution that it does not replace standard trawl surveys or actual sampling by fisheries observers, and that they still need to collect important biological data including size, age, sex, sexual maturity and diet information, which is important for stock assessments.
Meanwhile, eDNA researchers are working to identify ways to use this information to support management decisions with the help of stock assessment authors and quantitative ecologists.
