MbShea@PWP@English@UMCP

Abstract:

Our research seeks to address the extent to which the northern snakehead (Channa argus), an invasive fish species, represents a threat to the Potomac River ecosystem. The first goal of our research was to survey the perceptions and opinions of recreational anglers on the effects of the snakehead population in the Potomac River ecosystem. To determine angler perceptions, we created and administered 113 surveys from June – September 2014 at recreational boat ramps along the Potomac River. Our results indicated recreational anglers perceive that abundances and catch rates of target species, specifically largemouth bass, have declined since snakehead became established in the river.
The second goal of our research was to determine the genetic diversity and potential of the snakehead population to expand in the Potomac River. We hypothesized that the effective genetic population size would be much less than the census size of the snakehead population in the Potomac River. We collected tissue samples (fin clippings) from 79 snakehead collected in a recreational tournament held between Fort Washington and Wilson’s Landing, MD on the Potomac River and from electrofishing sampling conducted by the Maryland Department of Natural Resources in Pomonkey Creek, a tributary of the Potomac River. Microsatellite allele frequency data were recorded and analyzed in the software programs GenAlEx and NeEstimator to estimate heterozygosity and effective genetic population size. Resampling simulations indicated that the number of microsatellites and the number of fish analyzed provided sufficient precision. Simulations indicated that the effective population size estimate would expect to stabilize for samples > 70. Based on a sample of 79 fish scored for 12 microsatellites, we calculated an Ne of 15.3 individuals. This is substantially smaller than both the sample size and estimated population size. We conclude that genetic diversity in the snakehead population in the Potomac River remains low because of a genetic bottleneck associated with a founder effect.

Reader’s Profile:

The reader would be an official at the Department of Natural Resources here in Maryland (or Virginia). It could also be another government official or researcher that is part of some environmental agency in the local area.

Reader's Response:

As a governmental agency, we as a whole are trying to decide what we can do to address the potential threat of the northern snakehead in our river system and tributaries. Due to its nature of competing with other organisms, as well as anglers catching less than what they used to across the local waterways, we know it has the potential to disrupt the marine ecosystem. Furthermore, we know that the Snakehead has expanded geographically in our waterways as reported by anglers (and verified by government officials). Interestingly, the northern snakehead appears to have very low genetic diversity according to microsatellites, which tends to signal one of two things: an endangered species in decline or a population undergoing a genetic bottleneck. Since we know the population of the northern snakehead is expanding, it is very unlikely that its population dynamics are like that of an endangered species. I would note that the researchers did not stratify for age of the northern snakehead. This is extremely important, because if this fish were from a much older generation, perhaps close to the originally introduced population, it would make the effective population size severely low. Would they be interested in stratification for future research in this regard, seeing as the potential for cross-generational skewing in the microsatellite analysis? (This is probably the biggest criticism we had for our Gemstone project) Nonetheless, although the number might not be accurate, it is highly likely that the genetic bottlenecking has occurred and will slowly level off over time. Based on this research, what do the undergraduate students suggest we as government officials due to resolve this issue?

T -- are you revising the entire project? Or a section?