2003: The Life History of the Gammarus pseudolimnaeus in the Chesapeake Bay Watershed: New Perspectives

Bethany R. Brookshire (Biology)

It is only recently that Gammarus pseudolimnaeus has been documented in the Chesapeake Bay Watershed, and the populations in the watershed have been studied with regards to life history only rarely. Therefore, in addition to an extensive literature review of all other closely related freshwater Gammaridae, it was deemed necessary to conduct life history experimentation and observation upon four populations of Gammarus pseudolimnaeus. Two of these populations, those in South West Wormeley Stream and in Washington Springs, occur in the York River drainage of the Chesapeake Bay watershed, and two others, Berkeley Creek and Strawberry Creek (otherwise known as Pascal's Creek) occur in the James River drainage.

All four of these populations were examined for mating frequency over time, and the size and fecundity of the population as a whole. Data for mating frequency were collected at weekly intervals, and fecundity information at monthly intervals. For mating frequency studies, random samples were taken and the percentage of mating pairs in the population calculated. For fecundity sampling, randomly selected mating pairs were taken back to the laboratory, males and females measured, and the female's brood pouch extracted to gain information on reproductive success.

Although data is incomplete thus far, there appear to be differences in the size and fecundity of these populations relative to populations described in the literature. There also appear to be significant differences in reproductive timing between these populations and those to the north and west. In future it is hoped that these data will be useful in understanding the life history of Gammarus pseudolimnaeus in this area and in the rest of the Chesapeake Bay watershed, as well as determining the reproductive potential between these populations and others described in the literature.

For additional documentation Bethany Brookshire provided a PowerPoint Presentation entitled "The Life History of the Gammarus pseudolimnaeus in the Chesapeake Bay Watershed: New Perspectives," provided here in PDF form.