Science Serving Maryland's Coasts
Louis Plough, Ph.D., Ryan Woodland, Ph.D.
Horn Point Laboratory
Determining Fecundity and Genetic Differences of Neomysis americana in River Systems that Vary in Productivity Within the Chesapeake Bay
Small, pelagic crustaceans such as mysids are a central component of productive food webs in many estuaries and serve as a critical trophic link between primary production and larger consumers. Neomysis americana (Smith 1873) is a highly abundant mysid species found in temperate coastal habitats of the western Atlantic; although known to be an important prey item in the Chesapeake Bay (CB), basic understanding of its distribution, population dynamics, and ecology is lacking. This project investigated spatial patterns in relative abundance of N. americana by examining female fecundity and assessing genetic connectivity of mysids across space and time (seasons), focusing on two major tributaries of the CB, the Choptank and Patuxent Rivers. St. Lawrence River N. americana were used for regional genetic comparisons. Tests for length-specific fecundity differences between tributaries indicated the number of eggs per female was higher in the Choptank (ANCOVA, p= 0.002) and spring female fecundity was higher than fall fecundity (ANCOVA, p= 0.02). Preliminary analysis of CO1 haplotype networks using a median joining approach revealed strong regional structure (no sharing of haplotypes between St. Lawrence and CB), AMOVA results confirmed high variation among regions (Phi-St = 0.93). Within Chesapeake Bay, haplotypes were well-mixed and statistical analyses verified no significant spatial (Choptank vs Patuxent) or temporal (June vs. September) differences (AMOVA P >0.5). Given the absence of genetic differences between tributaries based on CO1 data, environmental factors likely play a large role in the fecundity differences observed across the tributaries. Future research into the drivers of spatial fecundity differences will help inform development of mysid population models, contribute to our understanding of estuarine food web controls, and build our capacity to better integrate forage into ecosystem-based fisheries management in CB.
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