Hatchery-reared Gulf of Mexico sturgeon were stocked into two
reaches of the Hillsborough River. Fish implanted with acoustic
transmitters are being tracked. Indices will be developed relative
to habitat use.
Telemetry Study of Habitat Utilization and Success of
Hatchery-reared Gulf of Mexico Sturgeon in the Hillsborough River,
Sturgeon conservation research was initiated in the Special
Projects Group of the Directors office. The Hillsborough River was
selected as a study area where habitat utilization of Gulf of
Mexico sturgeon in a coastal urban river system.
The Hillsborough River is unique in that
although it flows through a large metropolitan and agriculture area
it has been aggressively conserved by maintenance of a "green
corridor" of adjacent upland, conservation of some of its
groundwater sources, intensive pollution elimination and
maintenance of good water quality. There is a dam in the river at
the Sulfur Springs fall line that partitions it into two diverse
reaches, one tidal the other freshwater.
A conservative program to release, track, monitor and assess
hatchery-reared fish in both major reaches of the river was
developed in the first half of calendar year 2000.
Data from this project will be used to develop an analysis of
sturgeon utilization of both reaches of the Hillsborough River
(time series geographical description of distribution), to estimate
relative abundance of fishes, to develop survival indices, and to
provide data on the status and trends of sub-adult sturgeon after
release. These data will provide the Florida Fish and Wildlife
Conservation Commission (FWC) and other resource management
agencies with information necessary for implementing effective
threatened species management measures. These data will also
provide relative life history, feeding, health and other
information for Gulf of Mexico sturgeon, especially in perturbed
element of this project is that it encourages diversity of
scientific approach for sturgeon research. It has an extensive
public education component to encourage dissemination of
information about the threatened and endangered status of sturgeon
to the public. It will educate diverse groups on worldwide status
of sturgeons and provide extensive regional information about Gulf
of Mexico and other sturgeon of Florida. This study also
contributes information to other research groups on mapping,
habitat types and distribution, and water quality of the
Hillsborough River system. This will complement a large assemblage
of research information for the Tampa Bay estuary.
The first objective of the study is to determine initial
mortality, if any, and short-term suitability of two reaches of the
river to support sub-adult Gulf sturgeon. This objective will test
the immediate feasibility of the project concept and allow
determination of survival. In addition short-term movements, growth
and health of stocked sub-adult sturgeon in freshwater habitat of
the river, including the reservoir and the tidal downstream habitat
of the river will be assessed along with water quality evaluations
and habitat parameters for a period of one year. Feasibility of
executing further research will be evaluated.
The second objective is to assess growth, survival, movement,
and habitat utilization in the upper reach of the river (above the
dam) and the lower reach of the river (below the dam). Multiple
stocking sites, stratified over in each of the two reaches of the
system and over three habitat types in each reach were used.
Refinement of existing techniques and development of new
techniques to monitor, track and recapture released sturgeon for
recovery of scientific information will be refined during the
course of this project. This will provide scientists and managers
with information regarding suitability of the system to support
sturgeon and allow conservation decisions based on use of
This monitoring program was initiated in the Hillsborough River
Basin, in the main flow of the river between Crystal Springs Park,
FL. and Davis Islands, FL. (Figure 1.)
MARKING AND TRACKING ELEMENTS
On October 17 and 18 forty nine Gulf of Mexico Sturgeon (mean
weight 2.76 kg and mean total length 877.40 mm) were implanted with
acoustic transmitters and passive integrated transponders. For the
most part fish survived surgery and recovered to better condition
than they were prior to surgery.
Between November 13, 2000 and January 1, 2001 46 sturgeon were
released into 6 separate habitat types in both reaches of the
river. Fish were stocked over a protracted two-month period in
order to closely monitor initial survival and performance of fish.
This was necessary in case problems occurred and stocking strategy
needed to be modified.
Fish were released at the Hillsborough River State Park, Dead
River County Park, and in the Reservoir in Temple Terrace in the
upper reach of the river. Fish were released in the Sulfur Springs
area, Lowery Park area and between Hillsborough Avenue and Columbus
Drive in the lower reach of the river.
Habitat types in the upper river include: (1)hard
bottom/limestone sediments mixed with shell, coarse sand and silt ,
(2) Riverine (majority of upper river includes mixed hard
bottom/limestone, mud flat/coarse shell and sand/clay and rock
banks with bars and deep holes/emergent hardwoods and flatwoods,
(3) Hillsborough River Reservoir (modified riverine with cypress
spoils, fine sand/mudflats, broad shallow areas interspersed with
channels and deep holes, fringed with emergent vegetation and low
density residential dwellings Habitat types in lower river include:
1) Karst (hard bottom/limestone sediments mixed with shell and
coarse sand with ground water sources into the river Sulfur
Springs/Hannah's Swirl, (2) degraded riverine habitat with broad
mud/sand flats emergent oligohaline vegetation, mixed oligohaline
invertebrates/relatively high density residential dwellings with
bulkhead shoreline, (3), riverine/mesohaline to brackish water
habitat, mixed mesohaline-brackish emergent and submerged
vegetation, low density residential dwellings with broad areas of
natural shoreline and adjacent urban greenspace.
Released fish will be monitored on a biweekly sampling schedule
using a digital reference map with mid-river transect and 250 meter
gridlines. When practicable fish will be located from mid-river at
intervals of 250 meters. This approach will vary in the upper river
where bends in the river and structures alter transmissions of
A stationary receiver has been set up on a floating dock at the
University of Tampa where river width is about 300 meters. A
directional hydrophone is connected to a Sonotronics USR 90
stationary scanning receiver interfaced with a Hewlett Packard Palm
computer utilizing DOS 5.0 as an operating system. Data is stored
on a PCMCIA card and uploaded to an Excell Spreadsheet file for
analysis. As of 12/02 no transmission data in the frequency range
or transmission intervals for our sturgeon have been logged at this
fixed station. The fixed station is about 3000 meters from the
mouth of the Hillsborough River.
MOVEMENT OF FISH
Overall, movement of released fish has been diverse. Some have
remained near their release sites, some have moved up-river from
their release sites, and some have moved down-river. A few have
moved long distances from the place of release. Two fish released
at the Hillsborough River State Park were found below Harney Canal
in the reservoir at Temple Terrace, a distance of well over 30
kilometers. This movement has occurred in less than two months.
Sampling the Temple Terrace area on January 2-3, we found 5 of 8
sturgeon up-river, closer to Harney Canal. Sampling the Sulfur
Springs and Lowry Park areas on January 4 we found 13 fish. Six of
those moved down-river, five moved up-river and two stayed in the
same general area of their release. Sampling the river between
Hillsborough River State Park and Dead River we found 6 of 8 fish.
Tracking has now intensified as most of activities with
implantation surgery and release have subsided.