R/P-64

Understanding the Distribution and Ecology of the Mysid Neomysis americana, a Key Forage Species in Chesapeake Bay

Principal Investigator:

Ryan Woodland

Start/End Year:

2018 - 2020

Institution:

Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science

Co-Principal Investigator:

Hongsheng Bi, Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science; Elizabeth North, Horn Point Laboratory, University of Maryland Center for Environmental Science

Topic(s):

Strategic focus area:

Sustainable fisheries and aquaculture

Description:

There is a concerted effort to move away from traditional single species fisheries management in Chesapeake Bay toward a more holistic management framework that considers the interactions between fishery and non-fishery species and how their dynamics are linked to their environment. This framework, termed ecosystem-based fisheries management (EBFM), requires an understanding of the role of forage in sustaining upper trophic levels and the goal of this proposed research project is to fill important knowledge gaps related to the forage base of key commercial and recreational fish species in Chesapeake Bay. This project would seek to establish valuable information on how mysids, particularly Neomysis americana, are distributed relative to key environmental, physical and biological gradients within two tributaries known to serve as important nurseries for a range of commercially and recreationally important fisheries species in Chesapeake Bay, the Patuxent and Choptank Rivers. This project will directly address two focus areas within the Maryland Sea Grant 2018-2020 Strategic Plan - Healthy Coastal Ecosystems, and Sustainable Fisheries and Aquaculture. Specific objectives of this proposal include:

  1. Measure patterns in mysid distribution and abundance within the Patuxent and Choptank Rivers from spring to autumn;
  2. Analyze demographic parameters in each tributary during each season;
  3. Use natural biomarkers of diet to quantify patterns in mysid feeding relative to local water quality; and
  4. Conduct a critical, initial analysis of the relationship(s) between mysid dynamics and key physical and environmental gradients, including oxygenation of bottom waters.

Mysids occupy an important position in coastal ecosystems because they are important prey species for juvenile fish and because they provide an important link between lower trophic levels and finfish production. The Patuxent and Choptank Rivers provide an excellent opportunity to compare the seasonal distribution of mysids in two ecosystems that are broadly representative of many Chesapeake Bay tributaries. Field efforts will focus on sampling during the late spring to early fall months of May, June, July, August and September, periods in which high mysid abundance is expected to coincide with an interval of critical growth and foraging for many young-of-the-year fish species, the timing of peak secondary production and prevalence of hypoxic conditions. Mysids will be surveyed using high resolution sonar and traditional nets during the day and at night in the oligo-mesohaline region of each tributary. Cross-channel transects will provide estimates of relative abundance as well as specimens for trophic analysis using stable isotope natural biomarkers.

These findings will provide insight into the spatial and temporal distribution of a key trophic resource for fisheries species in Chesapeake Bay. Linking patterns in N. americana distribution, relative abundance, population demographics and feeding to environmental gradients within and between tributaries, this project will provide a crucial first step in understanding how local water quality can affect the ecology of a crucial forage taxon through space and time in Chesapeake Bay tributaries. 

Impact/Outcome:

Cryptic Crustaceans: Getting to Know Mysids and Their Important Role in the Chesapeake

Summary: A Maryland Sea Grant-supported, first-of-its-kind study of mysids in the Chesapeake will develop key data on this important forage species and its ability to link food webs throughout the water column.

Relevance: Mysids, also known as opossum shrimp, are small crustaceans that play a big role in coastal food webs. They are important food sources for species including weakfish, summer flounder, and American shad. Because they migrate through the water column-clustering near the bottom during the day and spreading out near the surface at night-they act as biological transfer mechanisms in food webs within the water's layers. However, scientists know little about mysids in the Chesapeake. Understanding their distribution, behavior, and abundance will provide resource managers critical baseline data about these important species to improve the accuracy and effectiveness of ecosystem-based models. In addition, learning how they respond to hypoxic conditions, which frequently occur in the benthic levels of the Bay and its tributaries, will help link biological responses to water quality. 

Response: Through a Maryland Sea Grant-supported project, researchers at the University of Maryland Center for Environmental Science worked with two graduate students, an undergraduate, and three community college undergraduate interns to undertake a first-of-its-kind study of mysids in the Bay. Over two years they completed 40 research cruises in the Choptank and Patuxent rivers from May through September. At seven stations in each, encompassing different levels of salinity and bottom topography, researchers sampled mysids using zooplankton nets at night, and for the first time used a high-resolution ARIS sonar system for daytime mysid swarm sampling. They also monitored salinity, temperature, and water quality throughout the water column, and used carbon and nitrogen isotopes to investigate what and where the mysids were eating. Sample analysis is ongoing, but preliminary results suggest females in the Choptank carried more eggs than those in the Patuxent, though the rivers' populations are not genetically distinct. As the Patuxent River samples showed higher stratification and lower dissolved oxygen than the Choptank, this indicates that water quality may affect fecundity.  

Results: Researchers engaged about 30 advanced computer game design students at University of Baltimore at the Universities at Shady Grove, who developed five prototype computer games and one board game based on mysids. The games emphasize the role of water quality, small forage species like mysids, and the lower trophic levels in sustaining the Bay's ecosystems. These unusual outreach tools can be used in other educational settings and at laboratory open house events. Researchers have also begun distributing preliminary results to regional management groups, providing baseline data on mysids to improve ecosystem-based models for resource management in the Bay. Additional analysis of mysid distribution relative to water quality will provide data on the relationship between mysid distribution and bottom water oxygenation.

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