Rebounding sturgeon in the Chesapeake?
Twenty years ago, sturgeons were thought to be extirpated from the Chesapeake Bay, but now we know we weren't looking hard enough. A new multi-scale collaborative research program funded through support by NOAA's Protected Resources Division is making important discoveries on this once-misunderstood and seemingly-cryptic species.
So why did sturgeons suddenly appear in the Chesapeake?
Some initial ideas that CSI is examining:
Now that we have a viable population in the Chesapeake, all would like to see continued recovery. CSI is examining factors that could curtail recovery such as sedimentation of spawning habitat, poor water quality in nurseries, ship strikes of adults in the narrow spawning corridors, and fisheries bycatch.
- Chesapeake sturgeons may have increased in abundance over the past 20 years, making them more apparent.
- Sturgeons have recolonized parts of the Chesapeake.
- In the past, we weren't looking with the right gear in the right times and places.
- Our predictions of poor habitats for sturgeons in the Chesapeake were overly dismal.
2014 Progress on Study Objectives
1. Assess Reproductive Habitats (VCU lead)
Recent evidence suggests there may be two spawning
periods in the James River, during spring (April-May) and fall (September). Previous evidence supported the latter (Balazik
et. al. 2012), and concentrated use of a narrow restricted segment of the upper
James River by two ripe males provides initial evidence of spawning during
spring months. Bottom types along this
stretch were likely favorable spawning habitats due to higher flows and scour
of hard bottoms. These same segments
receive heavy ship traffic. Ship strikes
of adults that had recently spawned were recovered during both spring (2014)
and fall months (2013) (left). Summer and fall 2013 telemetry indicates that
sturgeons may preferentially use narrow navigation channels within the James
Juveniles produced from fall spawning would have abbreviated growth seasons prior to their first winter.
In intensive rearing trials conducted at UMCES (right), juveniles originating
from St. John’s River (Canada) or the Altamaha River (Georgia) showed similar
growth responses to fall and winter conditions that they would experience in
northern (Canada), mid-Atlantic (Chesapeake), and southern (SC) systems. This
indicates that juveniles do not compensate for variations in growth season as
occurs for striped bass and other coastal fishes.
2. Assess nursery habitats in the James and York Rivers (VIMS, VCU lead)
During spring 2014, VCU biologists attempted to capture age
1-2 year old juvenile sturgeon in the James River. In >500 gill net hours of
effort only a single 58 cm juvenile was captured. Large catches of blue catfish and menhaden
interfered with their efforts. Over 1000
hours of effort to capture larger juveniles and adults during winter-spring
2014 in the James and York Rivers resulted in 44 transmitters being deployed. Telemetry receivers have been deployed by CSI
partners in the York, Rappahannock, Potomac Patuxent, eastern shore tributaries
and mid- and upper Chesapeake Bay (see figures below). Intensive mobile surveys were initiated in
July 2014 to study how tagged sturgeons select habitats on the basis of water
CSI Sturgeon News:
Resources for CSI Participants
Study Period: July 1, 2013 – June 30, 2016
Co-Principal Investigators/Managers: Brian Richardson and Chuck Stence, Maryland Department of Natural Resources
Bob Greenlee, Virginia Department of Game and Inland Fisheries David H. Secor, Univ of Maryland Center for Environmental Science